JPH0347918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for treating liquid media containing organic and/or inorganic contaminants. In particular, the present invention relates to a method and apparatus for cleaning porous diffusion elements immersed in a liquid medium containing such contaminants.

Aeration of waste liquid media, including, for example, domestic sewage and industrial wastewater, is an old technique. The activated sludge process, which involves aeration of liquid domestic sewage, has been in use for about 60 years.

Liquid media treated by such aeration methods commonly contain organic and/or inorganic contaminants, such as relatively insoluble salts related to water hardness;
and scale, containing living and non-living organic residues that contribute to the formation of grime. When aerating these media by a submerged aeration device, these contaminants gradually contaminate such devices at the point where they release oxygen-containing gas into the liquid medium, and the openings that release the oxygen-containing gas into the medium. occluding or deforming the structure, resulting in various undesirable consequences.

Such contaminants can be removed from the aerator if the aerator is a surface-discharge device, such as the flat porous ceramic plates used to discharge air into the sewer in early activated sludge treatment plants. Disturbs the uniformity of gas distribution from. Furthermore, in some circumstances the differential pressure required to drive the release of oxygen-containing gas from the aerator at a given flow rate may increase, thus reducing the amount of oxygen available through the aerator and thus reducing the oxygen transfer rate and/or the required The power consumed to maintain the flow rate of , thus increasing the energy requirements and costs.

Since these contamination phenomena progress naturally, the aeration equipment is sure to fail during long-term use. However, recognition of the intolerable environment resulting from failure of sewage treatment equipment has encouraged those skilled in the art to find solutions.

The problem of contamination has been discussed for many years and has been addressed in a variety of ways, with varying degrees of success. Literature discussing this problem and proposed solutions are
It can also be seen in the 1930s. But these successive publications only discuss the seriousness of the problem and the difficulty of finding truly satisfactory solutions. At a very early stage, it was recognized that removing the diffusion element from the aeration tank in order to clean it was inconvenient and expensive in terms of labor costs and equipment downtime. Various attempts have therefore been made to develop satisfactory process methods for in-situ cleaning of aerators without removing them from the aerator and, if possible, without removing the liquid medium from the tank.

One technique tried was to mix chlorine gas with air and inject it into the aerator while it was running. This method has had some success in reducing flow resistance and slightly increasing device life. However, this method has had mixed success.

For example, RB Jackson (Water)
Works Sewerage article "How to maintain the opening of a diffuser plate with chlorine" (September 1942, No. 380-
(p. 382), supplying chlorine on demand may be effective in maintaining operation for a period of time, but then draining the aeration tank again and replacing the defunct diffusion element with acid-containing It has been reported that cleaning with a liquid cleanser is required. However, Mr. Jackson is just one of many who have experimented with using gaseous cleaning agents for spot cleaning in a variety of equipment.

However, despite attempts to perfect this technology, it has generally not been accepted for large-scale sewage treatment systems that include porous diffusion elements.

Designers of sewage treatment systems are familiar with pipe diffusers or defusers for sewage treatment ponds or lagoons used in small areas. Such devices consist of rows of small diameter plastic tubes resting on the bottom of the lagoon or suspended above the bottom, with small holes or slits formed in the tubes at relatively long intervals along their length. . For example, Lagoon Aeration Corporation (Lagoon Aeration Corporation)
The tubular differential user, marketed under the trade name "LASAIRE" by Aeratin Corporation, is a 0.30mm tube approximately every 4 inches along the top of a 1/2 inch (12.7 mm) inner diameter tube.
(0.012 inch) diameter hole. Other commercially available tubular differential users have slits instead of holes. Another type is a rigid plastic tube with small porous ceramic inserts in the tube wall instead of the holes or slits described above. The sanitary engineer
In such tubular differential users, a cleaning gas such as hydrogen chloride is added to the oxygen-containing gas and the gas is forced through holes, slits or small ceramic inserts while these remain immersed in place in the liquid medium. Of course, cleaning has been found to be effective in removing deposits of organic and/or inorganic contaminants.

However, the obvious effectiveness of in-situ gas cleaning for tubular defusers, and the initial in-place cleaning of porous surface-emitting diffuser elements employed in tank-type aerators commonly used in large cities and large areas. Despite years of knowledge of attempts, in-place gas cleaning has not been commonly employed in such equipment.
Given the nature of the contamination problem and the fact that the technology associated with in-situ gas cleaning for tubular defusers has been available to wastewater treatment plant designers for many years, the problem of in-situ gas cleaning with porous diffusion elements It is thought that this was the criterion for selecting a tank-type aeration system. i.e., the commonly used method due to the fact that a practical, economical and reliable technique for cleaning in place the porous diffusion elements of tank aerators has not been apparent to equipment designers and those skilled in the art. It seems that this was not the case.

The equipment operator then removes the unit from the equipment, drains the tank, cleans the tank and then the contaminated diffusion elements with a fire hose, removes the multi-ton elements from the tank, and transports them to a cleaning factory. They were then subjected to acid and/or caustic solution cleaning, drying, and re-firing at high temperatures, replacing a significant number of elements that had become defective due to cracks or distortion during the re-firing process. Without the tedious task of removing the gasket material from the holder, installing a new gasket and repositioning the element, retightening the means holding the diffusion element in the holder, refilling the tank with liquid medium, and resuming operation. This is also thought to be the reason why in-place cleaning was not adopted.

Furthermore, Daniel H. completed on September 15, 1980.
“Survey and Evaluation of Fine Bubble” by Mr. Houck and Arthur G. Boon.
A research paper titled ``Dome Diffuser Aeration'' also proves that cleaning in place is not being adopted. They conducted an in-depth look at the design, operating procedures, methods of implementation and maintenance in the United States, and overseas activated sludge treatment equipment with microbubble defusers, as well as studied contamination issues and cleaning methods. It is reported that none of the equipment that requires periodic cleaning employs scheduled gas cleaning. Cleaning methods used for ceramic diffusion elements include refiring, pickling in combination with wash water and steam, ultrasonic cleaning, and manual brushing. This study also provided detailed information and observations about the high cost and limitations in economic viability of refiring. Nevertheless, it has been recommended to use recalcination and/or pickling on the basis of established effectiveness. However, this study states that pickling does not adequately clean ceramic diffusion elements contaminated with scale, particularly calcium carbonate, and that proper cleaning requires re-firing the diffusion element.

The need for suitable in-situ gas cleaning for tank systems with porous diffusion elements has existed for over 40 years. However, the solution to the problem is due to the willingness of equipment designers, operators, and government officials to tolerate and even encourage time-consuming, cumbersome, and expensive methods of shutting down the equipment described above. was not actually made clear.

Accordingly, the present invention seeks to provide a method and apparatus for treating liquid media that satisfies this need.

Similar to the prior art, the present invention passes a process gas through a diffusion element immersed in a liquid medium. Contaminants in the media and process gases have a tendency to form organic and/or inorganic deposits on the surfaces of the device, especially on surfaces adjacent to the liquid media. A cleaning gas, alone or mixed with a process gas, is passed through the device, as is the case with previous attempts. The cleaning gas, or a mixture of cleaning gas and processing gas, should be destructive to the above-mentioned deposits and have a tendency to dissolve and/or flake off the deposits.

According to the present invention, cleaning gas is introduced with sufficient frequency, including continuous introduction, to prevent the progress of deposition of contaminants exceeding a predetermined amount. The degree of contamination can be defined, for example, by the level of increase in hydrodynamic pressure or mean bubble release pressure relative to the initial baseline conditions of the element. For example, if the hydraulic pressure level of the element exceeds the standard condition and the effective gas release surface is 9×10 ² cm ² (1 ft.
² ) Approximately 635 mm (25 inches) of water column at a flow rate of 5.4 × 10 ⁴ cm ³ /min. (2 SCFM), preferably approximately 381.0 mm.
(15 inches), more preferably approximately 177.8 mm (7 inches)
Cleaning gas is supplied with sufficient frequency and in sufficient quantity to limit pressure increases above. As an alternative, the average bubble release pressure above the reference condition is approximately 635 water column pressure.
mm (25 inches), preferably about 381.0 mm (15 inches),
More preferably, the cleaning gas is supplied with sufficient frequency and in sufficient quantity to limit pressure build-up above about 7 inches.

The cleaning gas is supplied to the element via a gas distribution network having an immersion section and a plurality of flow regulating means in the immersion section. The flow regulating means is adapted to supply approximately equal amounts of cleaning gas, alone or mixed with the process gas, to each of the plurality of dimensioned or regulated plenums, and to direct each plenum to one or more diffusion elements. The plenums may be connected directly or indirectly so that each plenum can supply approximately the same amount of gas to the diffusion element.

The treatment gas, alone or in combination with the cleaning gas, is emitted from the diffusion element during an operating cycle consisting of a total number of days of at least about 30 days, preferably about 90 days, and more preferably about 365 days. Contamination is limited (delayed, prevented, and/or scavenging action).

In an embodiment of the liquid medium processing apparatus of the present invention,
Provide a gas distribution network in the tank. Such equipment introduces process gas into the network and
In addition, an introduction means is provided for periodically introducing the cleaning gas alone or in a mixture with the processing gas. A plurality of flow regulating means are also disposed in the submerged portion of the network for receiving and discharging the aforementioned gases at predetermined flow rates. The device is further provided with a plurality of porous surface-emitting diffusion elements having a large number of closely spaced fine pores forming passageways through which gas can be emitted, and in which the organic and/or Alternatively, the accumulation of inorganic contaminants will increase the hydraulic pressure compared to the standard conditions.
Each diffusion element is connected via a separate plenum to separate flow regulating means upstream of each plenum.

Examples of the present invention are shown below with reference to the drawings, but the present invention is not limited to these and various modifications can be made.

Theoretical Considerations In order to pass gas through the gas discharge passages of the diffusion element and foam the liquid medium, the pressure of the gas at the inlet end of the passage must be significantly higher compared to the pressure of the liquid at the outlet end of the passage. There must be.
This differential pressure is called pressure loss.

Most of the pressure loss is due to the surface tension of the liquid at the location where the bubble is formed, which contributes to the force exerted on the gas. Furthermore, the frictional resistance to gas flow in the passageway also contributes to some extent to the total pressure drop across the element.

The magnitude of the surface tension component of the pressure drop is inversely proportional to the effective hydraulic radius of the passageway at the location where the bubble is formed. Therefore, the surface tension component in pressure loss tends to increase as the passage becomes narrower and decrease as the passage becomes thicker.

The frictional resistance component of pressure loss is inversely proportional to the hole diameter. Therefore, this component tends to become larger as the pores become smaller and becomes smaller as the pores become larger.

Furthermore, the pressure drop in the passage is also affected by the gas flow passing through the passage. While surface tension is not significantly affected by flow at flow rates typical for porous elements, frictional resistance is directly related to flow rate. Therefore, increasing or decreasing the flow rate in the passageway increases or decreases the total pressure drop.

When the diffusion element is new, it exhibits a specific pressure drop for a given gas or gas mixture under given conditions of flow rate, temperature, gas viscosity, atmospheric pressure, and humidity, and a given pressure drop results in a specific flow rate. The pressure/flow characteristics of a diffusion element are often expressed in terms of hydrodynamic pressure. The pressure drop and hydraulic pressure of an element represents the result of the combination of different flows passing through many individual passages throughout the element.

The pressure/flow characteristics between each diffusion element vary widely. Individual holes in a given element also have different pressure/flow characteristics due to different passageway or hole shapes, dimensions, and hydraulic radii. Given the state of the art, it is difficult to manufacture hundreds or thousands of diffusion elements that exhibit nearly identical pressure/flow characteristics. Additionally, when the device is used in liquid media containing contaminants, the contaminants may become clogged at the inlet, interior, outlet, or any combination of passages or holes, reducing the diameter and/or effective hydraulic radius of the hole. , which affects the pressure/flow relationship of the element. Thus, all other factors being equal, contaminants can reduce the flow rate at a given pressure or increase the pressure required to maintain a given flow rate.

Next, a theoretical explanation will be provided showing the operation of the present invention and the advantages obtained by the present invention. When the element is new, gas flow through the element is preferentially directed toward the holes where the combined resistance of friction and surface tension is least. Therefore, other pores with a higher combined resistance of frictional resistance and surface tension have less effect and may even become inactive, at least temporarily.
According to this theory, as the busy or most active holes begin to become clogged with contaminant deposits, the flow rate decreases. When the operating pressure of the device is increased to maintain the flow rate, a significant number of the initially working or best working holes become clogged until the holes that are working less due to the high pressure drop are closed to the gas due to the increased pressure. be able to pass through. Eventually, the pores that had little effect in the early stages also begin to become clogged. When the pressure of the device is again increased, other holes which were less active due to the higher pressure drop become active. In this way, it is expected that the progress of clogging and the increase in pressure to maintain the flow rate will lead to a situation where most of the available pores of the diffusion element are clogged. If cleaning in place is carried out in the usual way at this stage of the element's operating history, as the element becomes more clogged, the cleaning gas will begin to clean only a few holes, such as the small holes that started to act the latest. It only passes through some larger holes that were not completely blocked when it was removed.

According to this theory, as the cleaning gas passes through these few holes and the deposits in the holes are reduced, the flow rate through these passages or holes will increase rapidly. This increased flow rate reduces the gas pressure at the inlet face of the element and diverts the cleaning gas to holes that have greater resistance to flow than other clogged holes or the few passageways that are cleaned as a result of the blockage. The pressure at the inlet face is thus reduced and is no longer able to overcome the effects of frictional resistance and surface tension forces in the many congested passages. If this theory is correct, passages or holes that have limited cleaning and are ineffective will first begin to clog and have the potential to pass the maximum flow rate at a given device operating pressure, and therefore will be the first to become clogged. This means that it is the hole that has the greatest potential for saving power.

If the above theory is correct, it would explain why diffusion elements often cannot be restored to their initial level of pressure drop by cleaning in place. This failure may also be due to the use of an inadequate amount of cleaning gas. Failure may also occur in some cases by not providing individual flow rate adjustment means for each diffuser element or group of diffuser elements. In such a case, the cleaning gas will find a flow path through the diffusion element that was last used rather than the initially clogged diffusion element, and therefore supplying cleaning gas will not be able to clean the device. You will no longer be able to recover initial conditions or abilities.

According to the invention, the above-mentioned disadvantages are overcome by supplying the cleaning gas relatively early in the operating history of the element with sufficient frequency and/or by providing individual flow regulators for each element.

A number of techniques and devices can be used to reduce the negative effects of delayed cleaning frequency and to improve the cleaning effectiveness of the present invention. Such techniques include (but are not limited to) the following:
providing the diffusion device with groups of diffusion elements and cleaning the groups individually and independently of other groups;
providing means for operating the diffusion elements in one group as described above with a higher flow rate and/or differential pressure during cleaning than those of another group; providing a relatively higher plenum pressure for the elements operating with lower air flow rates; The diffusion element is provided with a flow control means that provides a relatively low plenum pressure for elements operating with a high air flow rate; temporarily reduces the surface tension at the interface between the liquid medium and the diffusion element; the hydraulic pressure and/or the average Begin gas scrubbing while the diffusion element is operating at relatively low bubble release pressures; begin scrubbing before peaks in demand for the process gas occur, such as load fluctuations that result in seasonal peaks in activated sludge treatment units. provide means for controlling the liquid level in the equipment tank;

Next, embodiments of the present invention will be described with reference to the drawings.

The invention is most commonly used in aeration systems for biological wastewater treatment, but it can also be used to treat aqueous or non-aqueous liquids with or without biological and non-biological contaminants. It can be used for processing.

The cleaning gas used in the present invention may be any gas that is destructive to contaminants.

According to a preferred embodiment of the invention, the treatment gas is an oxygen-containing gas, in particular air, the cleaning gas is hydrogen chloride gas (HCl), the liquid medium is sewage, including domestic sewage, and the treatment equipment is a tank-type activated sludge. A processing device.

In typical sewage treatment plant operations, the inflow and/or
or a large increase in the hydrodynamic pressure or the mean bubble release pressure measured at the outflow surface, or a large increase in both pressures. For example, if there is a large accumulation of contaminants concentrated on the gas outlet face of a diffusion element, the element's hydrodynamic pressure and mean bubble release pressure measured at the outlet face will increase significantly, while the bubble release pressure at the inlet face will remain unchanged. On the other hand, if there is little contaminant accumulation concentrated on the gas inlet faces of the diffusion element, the average bubble release pressure at these inlet faces will increase moderately, the bubble release pressure at the outlet face of the element will remain unchanged, and The increase in the hydrodynamic pressure applied to the element is within the empirical error range of the hydrodynamic pressure measurement method, and is therefore imperceptible to the practical sense. However, if there is a large accumulation of contaminants concentrated on the inflow surface, even if the increase in bubble release pressure at the outflow surface is measurable, the hydraulic pressure and bubble release pressure may be appreciably measured at the inflow surface. causes a significant increase.

According to the invention, a cleaning gas is introduced to limit the deposition of contaminants on the diffusion element. This restriction has the effect of preventing or retarding the formation of such deposits, or of removing portions of the deposits from time to time, thereby controlling the degree of contamination of the diffusion element. Thus, for example, cleaning gas can be supplied frequently to prevent the formation of any appreciable deposits, with no discernible increase in either the hydraulic pressure or the mean bubble release pressure. can. Examples of other constraints include inhibiting the growth of contaminants of an organic or other nature, but not sufficient to completely prevent appreciable contaminant deposition on the diffusion element;
There are therefore treatment methods that use cleaning gas at a frequency sufficient to maintain the hydrodynamic pressure and/or average bubble release pressure of the element within the above-mentioned range over long operating cycles. Furthermore, at different times and under different conditions, a device can be operated in any of the above-mentioned modes of operation, i.e., prevention mode or delay mode or elimination mode.

Whether operating in prevention mode, delay mode, or removal mode, the cleaning gas can be supplied continuously or intermittently, including periodic time intervals. For example, supplying the cleaning gas almost continuously over a long operating cycle and then supplying the cleaning gas when for some reason the contaminant concentration in the liquid medium or process gas decreases, or when the process conditions become unfavorable for contaminant deposition. supply can be interrupted or intermittent. Conversely, in a type of equipment that typically introduces cleaning gas intermittently during one or more operating cycles, abnormal concentrations of contaminants in the liquid medium or process gas may occur, for example due to seasonal factors. When increased to high levels, continuous cleaning can be performed from time to time. This is one example where it has been found to be advantageous to continuously supply cleaning gas before the increase in hydraulic pressure and/or mean bubble release pressure becomes significant. Furthermore, when the device is being used to carry out decarburization operations, the cleaning gas can be supplied continuously. A suitable gas for continuous cleaning is hydrogen chloride gas.

However, it is preferable to supply the cleaning gas intermittently or to start the continuous supply of the cleaning gas when or before the time when contamination has progressed to a predetermined level. The degree of contamination at which cleaning is initiated can be defined, for example, as the level of increased hydraulic pressure or average bubble release pressure relative to the original reference condition of the element. However, this does not mean that the supply of cleaning gas should wait until a contamination condition is sufficient to cause a measurable increase in the hydraulic pressure and/or mean bubble release pressure of the diffusion element. In practice, it is possible to supply the cleaning gas intermittently but frequently enough so that the hydrodynamic pressure and/or the average bubble release pressure does not increase above the reference conditions, or increases only slightly. can. Furthermore, in systems where cleaning gas is supplied intermittently and frequently, the available pressure measuring devices are not capable of measuring the negligible pressure increase due to contaminant deposition between the points in time when cleaning gas is supplied. It does not have to be sufficiently precise.

The most typical mode of operation of many sewage treatment systems is probably to operate in such a way that no appreciable clogging of the diffusion elements occurs between the times the cleaning gas is supplied. For example, such clogging progresses to the point where it causes a measurable increase in the hydrodynamic pressure and/or mean bubble release pressure of the element. The increase in hydrodynamic pressure above the standard conditions is 5.4 x 10 ⁴ per 9 x 10 ² cm ² (1 ft ² ) of the effective gas release surface of the element.
At a discharge rate of cm ³ /min. (2SCFM), the water column pressure is at least about 5.08 mm (0.2 in.), or about 12.7
mm (0.5 inch), or approximately 17.78 mm (0.7 inch)
It can be done. The increase in average bubble release pressure over standard conditions is at least approximately 5.08 mm in water column pressure.
(0.2 inch), or approximately 12.7 mm (0.5 inch), or approximately 17.78 mm (0.7 inch).

When operating in intermittent mode, the hydrodynamic pressure level of the element is lower than the reference condition by 9 × 10 ² cm ² of the effective gas release surface.
At a discharge rate of 5.4 x 10 ⁴ cm ³ /min. (2SCFM) per ft ² , about 635 mm (25 inches) of water column pressure, or preferably about 381 mm (15 inches), or more preferably about 177.8 Gas scrubbing can begin at or before the amount equal to mm (7 inches). Alternatively, when the average bubble release pressure increases by about 635 mm (25 inches) of water column pressure, or preferably about 381 mm (15 inches), or more preferably about 177.8 mm (7 inches) above the baseline condition. You can also start cleaning.

The introduction of cleaning, i.e. the supply of cleaning gas during one or more supply periods, eliminates any increase in dynamic pressure or mean bubble release pressure caused by contamination between the conventional reference conditions and the beginning of cleaning. Supply in sufficient quantity to provide sufficient cleaning as defined by reducing the amount of water to a minimum value. For example, the cleaning gas is supplied until the decrease in hydraulic pressure corresponds to at least about 7.62 mm (0.3 inches), preferably about 12.70 mm (0.5 inches), and more preferably about 20.32 mm (0.8 inches) of water column pressure. Introduce. Alternatively, the average bubble release pressure reduction is at least approximately 12.70 mm in water column pressure.
(0.5 inch), preferably approximately 20.32 mm (0.8 inch),
More preferably, the cleaning gas is introduced to a value corresponding to about 0.9 inches.

In addition, a sufficient amount of cleaning gas can be introduced with sufficient frequency to allow long operation without removing the diffusion element from contact with the liquid medium and/or without applying techniques other than the gas to clean the diffusion element. It is further advantageous if the diffusion element remains in contact with the liquid medium throughout the cycle. The purpose of the present invention is to maintain contact in this manner and/or not use other cleaning techniques, which may be used for at least about 2 or 3 years.
The diffusing element may be removed from its holder during long operating cycles, including years of the design life of the element, which may be years or five years or more. With this in mind, increase the element's hydraulic pressure or mean bubble release pressure over the reference condition from zero in water column pressure.
Consideration should be given to continuous or intermittent supply of cleaning gas to within 127.0 mm (5 inches).

The cleaning gas can be introduced intermittently or continuously, whether or not the hydrodynamic pressure or bubble release pressure is actually measured. For example, initiating, maintaining, controlling or stopping the introduction of cleaning gas into the diffusion element in response to variables or conditions closely related to or representative of the contamination rate or amount to release hydraulic pressure or average bubbles. The pressure may be maintained at or below the above-mentioned levels. Experience with operating certain devices with liquid media and cleaning gases indicates that the hydraulic pressure of the elements and/or
Alternatively, the maximum number of days that the device can be operated with process gas and liquid medium until the increase in average bubble release pressure is at or above the level described above can be determined. Furthermore, experience can determine the time interval for supplying a predetermined amount of cleaning gas to inhibit contaminant build-up. With this information in hand, cleaning can be started periodically based on the time elapsed since the last cleaning, and at each cleaning the cleaning gas can be supplied for a period known from experience to be appropriate. It can be carried out.

However, introduction of cleaning gas is preferably initiated, maintained, controlled or stopped in response to conditions more directly representative of the hydrodynamic pressure or mean bubble release pressure of the element. For example, the back pressure of the device is a good indication of the hydraulic pressure and/or bubble release pressure of the element and can be used as a basis for implementing intermittent or continuous gas scrubbing.

The aforementioned increases and decreases in backpressure are detected by measuring pressure changes in the conduits of the distribution network between the compressor (including the blower) and the flow regulating means through which the diffusion element is supplied. be able to. Alternatively, the flow rate of gas through the diffusion element may be varied and the above-mentioned increase in backpressure detected based on all other conditions being equal or at least equivalent. Further, as device contamination progresses, an increase or decrease in back pressure can be detected based on the amount of additional power consumed to maintain the same flow rate of cleaning gas.

Although the cleaning gas is supplied simultaneously to arrayed groups of from about 10 to hundreds or thousands of elements, the above-mentioned limits on the increase in hydrodynamic pressure or average bubble release pressure need to apply to all of the elements in such groups. There isn't. Cleaning can begin when a majority of all the elements of a group reach a predetermined degree of contamination. However, it is not intended to exclude from consideration the case where a small fraction of the elements exceed the above-mentioned limits. The introduction of cleaning gas can thus be based on the hydrodynamic pressure or average bubble release pressure of a representative element of such a group, or on the basis of an estimated average condition of all elements in the group. Furthermore, it is not important that all elements of a given group receive the same amount of cleaning. If the group being processed contains elements with different degrees of contamination, it is obvious that the amount of cleaning that each element should receive will change, and the reduction in hydrodynamic pressure or average bubble release pressure will vary from element to element. Therefore, it is clear that it is not necessary to clean all of the elements to the same extent.

According to a particularly preferred embodiment of the invention, the reduction in the hydraulic pressure occurring during cleaning is partially slowed down and the aim is to increase as much as possible the number of holes in the diffusion element through which the cleaning gas passes. Assume that a contaminated diffusion element is being cleaned and that no other means are used to maintain or vary the hydraulic pressure during cleaning. Furthermore, it is assumed that the contaminants are of a type that appears as a decrease in hydraulic pressure during the cleaning process. In this case, when a considerably large number of clogged holes are restored to a working state, a larger amount of gas can easily pass through, and the inflow surface of the element is used to pass the gas to other clogged holes. The gas pressure available at will be reduced, so that the other clogged pores mentioned above will never be cleaned and will only have a partial cleaning effect. To avoid this drawback, the invention is implemented in conjunction with a partial delay in the reduction of the hydraulic pressure due to cleaning.

This feature of the invention is beneficial when flushing is initiated when the hydrodynamic pressure or average bubble release pressure increases by more than about 635 mm (25 inches) of water column pressure than the baseline condition, and particularly when the water column pressure Approximately 381
mm (15 inches), and more preferably about 177.8mm
(7 inches) or more, it is even more beneficial if cleaning begins. This method allows the useful life of the diffusing element to be considerably extended.

Means for delaying the decrease in hydraulic pressure include, for example, performing any one or more of the following in any order over at least a majority of the cleaning cycle to achieve good cleaning of the diffusion element. increasing the hydraulic pressure on the element over a portion of the cycle; maintaining the hydraulic pressure on the element constant over a portion of the cycle; and/or decreasing the rate of decrease in the hydraulic pressure on the element over a portion of the cycle, e.g. by simply washing. (assuming all other conditions are the same or equivalent).

Since the hydraulic pressure is actually the difference between the gas pressure at the inlet face of the diffusion element and the head of the hydrostatic pressure of the liquid medium at the outlet face of the element, delaying the decrease in the hydrodynamic pressure involved in gas scrubbing is dependent on the gas pressure or the static pressure. This can be done by controlling the water pressure head or both.

For example, a large pressure differential can be applied to the diffusion element during cleaning. This reduces the total gas pressure exerted on the gas inlet face of the element to the pressure that would be provided if the only change in the equipment and operating conditions was the removal of contaminants by the cleaning gas, at least for most of the cleaning cycle. Obtained if maintained above. Regardless of whether the total pressure level representing the increased differential pressure is set before, at, or after the initiation of cleaning gas introduction, the increased level of differential pressure is approximately 12.7 mm (0.5 mm) of water column pressure.
(inch), preferably 25.4 mm (1 inch), and more preferably 50.8 mm (2 inches).

The cleaning gas is supplied in a mixture with other gases, in such a way that the total pressure of all supplied gases satisfies the above-mentioned increased level of differential pressure, regardless of the proportion of the individual gases to the total gas pressure. . As the cleaning gas gradually removes contaminants from the elements, the volume passing through each individual element increases and the hydrodynamic pressure decreases, all other independent variables being equal. However, the control of hydraulic pressure by manipulating some variables results in the hydraulic pressure remaining constant, increasing, or decreasing at a slower rate than it would otherwise be. I can do it. Delaying the decrease in hydraulic pressure, including slowing down the rate of decrease, improves the cleaning effect. This is because the cleaning gas can be applied to many conduits and/or over long periods of time. This delay can be achieved by increasing the pressure in the plenum delivering gas to the diffusion element and/or decreasing the hydrostatic head.

Any technique that increases plenum pressure can be used to delay the decrease in hydraulic pressure. A preferred technique is to increase the compressor output and/or adjust the valves of the device to direct more airflow to the parts to be cleaned than to the other parts of the apparatus having a common air conduit. There is.

Furthermore, any technique that reduces the hydrostatic head can slow down the decrease in the hydrodynamic pressure. For example, gas is introduced and the hydrostatic head is made significantly lower than the water head before cleaning. Operating with a reduced hydrostatic head includes reducing the amount of immersion of the diffusion element during at least a portion of the period during which the cleaning gas is introduced. For example, if the level of the liquid medium in the processing tank is lowered or the diffusion element is attached to a lifting means for lifting it out of the liquid medium in the tank, the lifting means can be used to remove at least one part of the diffusion element. Raise the immersion position in the medium.

Delaying the decrease in hydraulic pressure during cleaning can be accomplished by controlling and adjusting the combination of gas pressure and hydrostatic head applied to the inlet face of the element. for example,
During periods when the hydrostatic head is rising due to increased equipment loading, the pressure is made high enough to retard the decline in the hydrodynamic pressure.

Other techniques that have been found to be effective in slowing the decline in hydraulic pressure include applying a liquid or gaseous surfactant to the interface between the diffusion element and the liquid medium during the cleaning period. There is. This increases the gas flow to the unit being cleaned due to the reduction in surface tension, thus allowing the cleaning gas to permeate many elements over a longer period of time.
HCl has been found to have this effect.

Not importantly, while providing a sufficiently high pressure and/or maintaining a sufficient amount of surfactant in contact with the diffusion element/liquid medium interface;
Approximately 40% of the cleaning gas, preferably 60%, more preferably
Releasing 80% is beneficial in speeding up cleaning.

Any of the above-mentioned techniques for producing a delay in hydraulic pressure reduction or an equivalent effect can be applied to individual tanks of a gas distribution network or multi-vessel system and to individual groups of diffusion elements forming part of the diffusion elements of a tank. can be applied to any selected part, including.

Various pressure conditions, such as hydrodynamic pressure, average bubble release pressure, reference conditions, equipment back pressure, etc., have been cited to describe the progress of any part of the process according to the invention. However, it is of course necessary to compare a large number of different observations at a given pressure value, and this observation is based on the diffusion of gases releasing the same or equivalent amount of gas at the same level of immersion in the same or equivalent liquid medium. must be applied to the element,
Alternatively, if there are large differences in immersion level, liquid, and/or gas, appropriate corrections must be made to the data to compensate for these differences. In addition, the hydraulic pressure and equipment back pressure must be maintained at a predetermined standard amount, e.g., 5.4 x 10 ⁴ cm ³ /min for every 9 x 10 ² cm ² (ft ² ) of designed, manufactured, and installed effective gas discharge surface.
When releasing a flow rate of (2SCFM), it is expressed by the corresponding numerical pressure. Corrections are therefore required to interpret observations or data regarding hydraulic pressure or equipment backpressure.

Depending on the requirements, some of the equipment may be 9 x 10 ²
The fact that ^it is not operating at a gas flow rate of 5.4 x 10 ⁴ cm ^{3 /} min. (2SCFM) ^and 5.4 ^x 10 ⁴ cm per ^ft 2 ³ /
The need for such a correction arises from the fact that even devices designed to operate at a gas flow rate of 2 SCFM will operate at different flow rates under different conditions. Thus, for example, in any device,
To compare observed conditions of device backpressure and hydraulic pressure, including increases in hydraulic pressure over reference conditions, those skilled in the art can compare the flow rate through the element, the concentration of the gas, and the viscosity, temperature, humidity, and barometric pressure. It is necessary to correct the observed hydraulic pressure using well-known calculations. In particular, the observation conditions for hydrodynamic pressure are 5.4 x 10 ⁴ per 9 x 10 ² cm ² (1 ft ² ), which is used to set the hydrodynamic pressure range.
It is necessary to convert to a value corresponding to the amount at cm ³ /min. (2SCFM).

On the other hand, if the present invention is implemented in an apparatus having flow measurement equipment of reasonable accuracy, the operating conditions may include recording the total gas volume from the compressor, gas viscosity, temperature, humidity, pressure, and other operating conditions. This is convenient because it reduces the need for calculations to quantities corresponding to the reference conditions of water pressure. Depending on the operating conditions of the device and variations in the flow rate, a pre-check can thus be introduced to determine whether cleaning should be started. These preliminary checks include returning the device to the flow rate specified in the reference conditions, then recording the other data described above, and correcting the observed pressure to an amount equivalent to the reference conditions, if necessary.

Flowmeters with the required accuracy are commercially available;
A number of conversion tables are also available for converting to the standard quantities for temperature, pressure, and humidity conditions (SCFM) that are adopted as standards for the equipment in question. A general purpose or special purpose computer may also be provided to perform the required data conversions and operate the process control equipment as required;
Of course, it can also be programmed.

9×10 ² cm ² (1ftt ² ) per 5.4×10 ⁴ cm ³ /min.
Although the flow rate of (2SCFM) is convenient as a reference quantity for hydraulic pressure and device pressure, and is typical as the flow rate through the diffusion element of many commercially available devices,
One or more different reference flow rates may be employed as a basis for implementing and controlling the present invention in a given device. For example, 9×10 ² cm ² (1 ft ² )
^The device and diffusion elements can be designed for different flow rates other than 5.4 x 10 ⁴ cm ³ /min. ( ^2SCFM ) or 5.4 x 10 ⁴ cm ³ / ^min .
It is also possible to operate satisfactorily for an extended period of time, for example 90 days, at an average daily flow rate significantly different from min. (2SCFM). Increases in hydraulic pressure at any of these flow rates can also be used to initiate or control cleaning. For example, the increase in hydraulic pressure is 635 mm (25 inches) in water column pressure compared to the reference condition.
The device can be activated to begin cleaning before the In this case, the baseline operating conditions and the 635 mm (25 inches) water column pressure condition correspond to a flow rate equal to the average daily flow rate through the device for the 90 days immediately before cleaning began. Changes in the reference flow rate can be made in a similar manner to the back pressure of the device.

There is no fixed principle regarding the amount of cleaning gas that should be supplied relative to the amount of contaminant deposited. That is, different cleaning gases have different effects, and each deposit has a different reactivity to the cleaning gas. However, the present invention allows one skilled in the art to determine the amount of cleaning gas for cleaning various contaminant deposits. Generally, the amount used in accordance with the present invention is sufficient to reduce the increase in hydrodynamic pressure and/or mean bubble release pressure of the element.

The amount of cleaning gas supplied and the concentration of the cleaning gas when mixed with other gases can vary considerably. However, it has been found that at lower quantities or concentrations the cleaning gas has to be supplied over a longer period of time, whereas at higher quantities or concentrations cleaning can be accomplished in a shorter period of time. However, it is preferred to provide the cleaning gas in an amount and concentration that will allow cleaning to occur within about 8 hours.

The concentration of the cleaning gas when mixed with the process gas is expressed as the mole fraction and/or equilibrium concentration of the cleaning gas in the gas mixture, which is the concentration that results when the liquid sample is saturated with the medium. Define. However, this does not mean that the liquid medium operating the diffusion element must become saturated with the gas mixture during cleaning.
The concentration to be used can be selected based on various factors. These factors include the solubility of the gas in the liquid medium, the specific destructiveness of the aqueous cleaning gas solution towards deposited contaminants, and the degree of ionization of the synthetic solution in the electrolyte. For cleaning gases that form acidic solutions in water, the solubility constant and degree of ionization are particularly important. In this case the PH as well as the mole fraction and equilibrium concentration of the gas phase can be used as measuring and defining means.

The appropriate limits mentioned above can be determined empirically. Tests using a gas mixture of HCl and air at approximately 100% humidity and atmospheric pressure have shown that the mole fraction per total moles of gas in the mixture is at least approximately 7.5
10 ^-5 , preferably 1.3×10 ⁻³ , more preferably 6.6×
It turns out that 10 ^-3 is appropriate. These values correspond respectively to equilibrium concentrations of 0.167, 0.24 and 0.28 per total weight of the gas mixture at standard atmospheric pressure and standard temperature, and to values of pH less than 0.7, 0.5 and 0.5. However, if the pH equilibrium concentration is about 3 or less,
Alternatively, less than about 2 acid gases, or less than about 1 acid gas may be used. When the present invention is used in a sewage treatment tank that uses aerobic and/or anaerobic microorganisms to metabolize pollutants in sewage, the concentration and amount of cleaning gas have a large negative impact on the overall metabolic activity of the microorganisms in the tank. There should be no amount.

Another gas that may (or may not) be mixed with the cleaning gas and supplied to the diffusion element is water vapor, which may be intentionally added to the device or may be introduced unintentionally. There is also.
For example, water vapor enters the device and mixes with the cleaning gas. This is because water vapor is a normal component of some process gases (eg, air humidity when air is used as the process gas). The cleaning gas and water vapor are mixed before or after introducing the cleaning gas into the network. For example, the cleaning gas is dissolved in water, the process gas is then passed through the water to extract the cleaning gas and water vapor, and this gas mixture is introduced into the network. On the other hand, commercially available tank aeration systems often contain large amounts of condensed water in the network, and this water vapor has entered the system as a component of the aeration air. The cleaning gas and water vapor are thus mixed as a result of contact and admixture of the water vapor accumulated in the network with the mixture of cleaning gas and process gas formed before contacting the cleaning gas or condensed water. Furthermore, when supplying cleaning gas to a network containing a large amount of condensed water, the cleaning gas is Therefore, the maximum cleaning effect cannot be obtained until the water is almost saturated. If contaminant deposits occur in locations in the diffusion element where water supply by liquid media or process gas is not readily available, supply of water vapor entrained in the cleaning gas to form a destructive aqueous solution to facilitate cleaning. That is beneficial.

Various means can be used to supply the process gas, or to continuously or periodically supply a destructive mixture of process gas and cleaning gas. Process gases can be supplied, for example, by conventional compressors or blowers and means for controlling the total pressure or flow rate of the apparatus, well known to those skilled in the art. The cleaning gas is supplied via conventional flow control and flow measurement means from a storage tank containing a quantity of pressurized gas. By connecting the means for supplying the process gas to the means for transferring the process gas to the liquid medium, the required destructive gas mixture can be formed. A device can be provided for automatically controlling the mixing of the process gas and the cleaning gas and the initiation of the supply of the destructive gas mixture.
According to a preferred embodiment of the invention, the distribution network is provided with measuring means, which measuring means are arranged, but not necessarily in the immersed part of the tank, to measure the amount of gas passing through the network or through the typical diffusion element. By measuring temperature, pressure, and flow rate with sufficient accuracy, the dynamic water pressure applied to the diffusion element can be measured in terms of water column pressure to exceed the standard conditions.
It should be maintained at no more than 635 mm (25 inches), preferably about 381 mm (15 inches), and more preferably about 177.8 mm (7 inches).

The gas distribution network can be constructed of any suitable material, such as metal, plastic-lined metal, and rigid plastic tubing, with the plastic tubing being There are reinforced and unreinforced thermoplastic and thermoset tubes. However, it is preferred to supply the cleaning gas to the diffusion element via the part of the network described above made of synthetic resin material. Other parts of the network may be formed of other materials, such as metal conduits and fittings. In accordance with a preferred embodiment of the invention, the cleaning gas is mixed with the process gas at the immersion location of the network. This allows the use of metal conduits in non-submerged parts of the network,
For example, a metal conduit can be used in the lower conduit for transferring the process gas to the liquid medium from above the surface of the liquid medium. Preferably, the parts of the gas distribution network which come into contact with the destructive gas mixture are constituted by conduits having an inner surface of acid-resistant synthetic polymeric material. If synthetic resin tubing is selected with a load-bearing wall of a suitable polymeric material, approximately 140.6 Kg/cm ² (2000 psi) to approximately
Tensile strength of 4218.4Kg/ ^cm2 (60000psi), approx. 2.8×
10 ³ Kg/cm ² (4×10 ⁴ psi) to approx. 2.8×10 ⁵ Kg/cm ² (4
× ¹⁰⁶ psi) bending strength, approx. 0.7Kg/ ^cm2 (10psi)~
It shall have a stiffness of approximately ¹⁰⁰⁰ psi (according to ASTM D-2412). Preferably, the conduit wall may be formed from a synthetic polymeric material, such as rigid polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS) or other suitable resin material. Although these materials can and are preferably used in the construction of the flow regulating means and the diffusion element holder, elastomeric materials that are resistant to cleaning gases may also be used for the flow regulating means or the sealing means. can. The materials used should be selected for resistance to corrosion, weathering, compression, and impact. Suitable devices can be provided for inflation and deflation if necessary.

The flow rate adjusting means can be integrated into the holder of the diffusion element or can be separate. Although the flow regulating means can be mounted inside or outside the holder, the most convenient arrangement is to mount it within the holder. The flow regulating devices used in the present invention may be of any type, including active and passive flow regulating means, including those capable of varying pressure response characteristics. For example, flow regulating means such as fixed orifices that respond exponentially to pressure changes, or flow regulating means that respond linearly, for example passages with a high length to cross-sectional area ratio, can be used. Additionally, passages whose cross-sectional area changes in response to changes in pressure may be used, including those that provide valve action and those that allow flow to pass in only one direction.

The diffusing element may be supported by suitable holders, each of which at least partially surrounds a fill space or plenum (described below) and having a support surface on which the diffusing element is disposed. The circumferential portions are supported and engaged by retaining means and/or sealing means (described below). Known and popular types of holders include those that attach the element to the holder by engaging the threads of the holder with bolt holes extending through the element, and those that attach the element to the periphery of the holder. Of these, the latter is preferred, and various preferred embodiments of the sealing means for sealing such holders and elements are shown below.

The plenum may be of any suitable material, but is preferably formed from a reinforced synthetic material having the physical characteristics described above in connection with the preferred tube. The holder may be formed by any suitable forming method, such as injection molding, lay-up, and spraying.

The gas is discharged from the flow rate adjustment means to the inflow surface of the diffusion element via a plenum, and this plenum is made into a gas chamber defined by a wall means with a gas outlet, so that the gas can be uniformly distributed to the inflow surface. Do it like this. Although the plenum is generally provided within the holder, it does not necessarily have to be within the holder. The walls of one or more regions of each plenum can be defined by an inflow surface of a diffusing element;
The walls of other regions of the plenum may also be defined by the inner surface of the holder. Optionally, a large portion of the wall area of the plenum is defined by the inlet face of the diffuser element, the shape of the element at the inlet face being elongated with a small diameter compared to its length.

As mentioned above, the holder and the retaining means can be of various types, for example in which the elements are mounted in direct or indirect contact with the periphery of the holder, or at mutually spaced points on the periphery of the holder, or otherwise. 4,046,845 and US Pat.
There is a center bolt configuration as described in No. 3532272. However, mounting the diffuser element using a central clamping member or other clamping member extending through a hole formed in the diffuser surface has adverse effects that cannot be foreseen with certainty.

In the prior art, sealing between the element and the plenum has been accomplished by vertically loaded elastomeric gaskets. The load required for proper sealing of a porous diffusion element is high, e.g. 2.54
22.68Kg (50 lbs) per cm (1 inch).
Increased strength and stiffness of the diffuser element and plenum may be required if the forces distributed around the periphery are greater than in the preferred embodiment of the invention, in which case continuous clamping or retaining members are used. .

Additionally, it is common for the clamping member that penetrates the element and enters the plenum to have play in the hole. Therefore, if the entire interior of the hole is not sealed, air can pass freely through this gap, causing an excessive flow from the diffusion element in the vicinity of the clamping member. Enlarging the confinement area below the lower horizontal surface of the retaining means lengthens and does not modify the path of air flowing from the clearance area to the diffusion surface. This is because the reduction in unit flow rate near the clamping member due to the increased sealing area on the surface reduces the frictional pressure in this area, resulting in the problem of non-uniform force distribution.

The negative effects of the above-mentioned through-type fastening members can be overcome by using the preferred peripheral clamp or retention method according to the present invention. Applicable retaining means include clips, clamps and rings, which are clamps or simply retainers, and are attached to the plenum by bolts, hooks, screws and other fastening means.

Suitable sealing members can be formed from a variety of materials and in a variety of shapes. For example, various plastics and rubbery elastomers can be used. The sealing member may be one or more members of circular, flat or other shaped cross-section with a particular contour matching the shape of the diffusion element and/or the support means. The required shape may be formed by any suitable forming method, such as extrusion, casting, and other forming techniques.

According to the invention, sealing means are used which are attached or attached to the diffusing element, and these sealing means can be clamped or glued in place, or of the non-adhesive, non-attached type. Closing means that are neither attached nor attached to the diffuser element are preferred in the present invention, and can be carried out by the structure of the holder, by the structure of the above-mentioned holding means, by the structure of the diffuser element itself and by a combination of these structures. It is preferable to hold it in an element. The blocking means can be arranged at the periphery of the diffusing element, which can be arranged inside and/or outside the contour of the element in plan view, and above, below and/or along the sides of the element, but as follows: Conveniently, the sealing member contacts the upper edge of the vertical (including near-vertical) sides of the element, as described in detail in .

Diffusing elements can be formed from a variety of materials and in a variety of shapes. Generally, the invention may be practiced using a porous diffusion element having a number of closely spaced passageways or pores of small diameter that define a path for the release of gas into a liquid medium. The shape, size, and length of these holes or passageways can be arbitrary, and the shape is determined in part by the method of forming the element. For example, a porous body is formed by solidifying a shaped mixture of a water-insoluble molten material and water-soluble solid particles, and then dissolving and releasing the water-soluble particles. Alternatively, the porous body can be formed by overlapping fabrics formed from fibers or filaments. However, the diffusion element and the formation of pores in the diffusion element combine solid particles into agglomerates, and the gaps between the bonded particles of this agglomerate form pores. The particles can be bonded with or without adhesive.

The elements can be made of, for example, particulate and/or fibrous organic or inorganic materials. Examples of organic materials include particles of soluble polymeric materials as described in US Pat. No. 3,970,731. Examples of inorganic materials include metal and ceramic powders such as alumina, silica, mullite, and various clays. The finely divided material can be shaped and solidified by applying pressure, and optionally heated or sintered to create the required bonding strength. It is also possible to bond with organic or inorganic binders, and the fine particles and/or fibers can be bonded to each other by organic adhesives, ceramic or melt bonding, or by sintering.

The diffusing element can be formed into any suitable shape. For example, it can be in the shape of a plate defining a flat or curved surface, or a tube or dome. Applicable shapes include circular, elliptical, square, rectangular, polygonal, and irregular shapes in plan view, and those with a nearly horizontal cross section. There are those that are truly flat and those that are non-horizontal but nearly horizontal in the sense that they have parts that extend partially horizontally.
The edge of the element can be flat and vertical or sloped, or can be stepped or unstepped, with slopes, roundings, grooves, etc. can be provided.

Commonly applicable elements include U.S. Pat.
Provide an effective gas release surface without large openings to release air bubbles as described in No. 3,970,731. Preferably, fine bubbles are generated from any position on the gas release surface. 0.3T on the gas inflow surface of the element
(T is the average thickness of the element considered based on area)
It should not have air permeation holes larger than the above. Large pores are pores that are larger than would normally occur due to consolidation of the particulate material. Advantageously, all gas paths through the body of the element to the gas ejection surface attached to the plenum or holder are approximately the same length. Furthermore, the bubble release pressure is approximately 50.8 mm to 508 in water column pressure.
mm (2 to 20 inches), preferably about 76.2 mm to 381 mm
(3 to 15 inches), more preferably about 101.6 mm to 254 mm
(4 to 10 inches) diffusing elements may be used.
The optimum bubble release pressure is believed to be approximately 7 inches (177.8 mm) of water column pressure. The predetermined value is at the time of manufacture,
That is, the bubble release pressure of the new device in water before use. Techniques for determining bubble release pressure and other suitable characteristics of diffusion elements for use in the present invention are described in US Pat. No. 9,528,928. Furthermore, it is preferable to form the element of a hydrophilic material. That is, it is preferable that the element be made of a material that exhibits hydrophilic properties during manufacture and before use. In addition, the sides (including extreme vertical edges, vertical or near-vertical surfaces of steps adjacent to the periphery of the element) are made porous and at least semi-permeable, with an adhesive to prevent bubble formation. It is best to make sure there are no substances. When the element was new, the water column was 50.8 mm.
Approximately 1.62×10 ⁵ to 5.4×10 ⁶ cm ³ / at a pressure of (2 inches)
It is preferable to have a transmittance of min. (6 to 200 SCFM). The thickness of the element may be uniform throughout, or may vary when viewed in horizontal section. A particularly preferred characteristic of suitable diffusion elements is that the bubble release pressure is relatively uniform across the gas exit surface of the element. Such uniformity can be obtained by any suitable method, for example as described in U.S. Pat.
There is a technique described in No. 952892.

According to a preferred embodiment of the invention, the standard deviation of at least five bubble release pressure measurements taken along two mutually orthogonal straight lines at the outflow face of the diffusion element is preferably 0.25 or less. Should be 0.05 or less. Further suitable diffusing elements are disclosed in the above-mentioned US Pat.
It is formed from particles that are sintered or bonded using the techniques described in No. 952892 and No. 952862. Diffusion elements can be selected that have any one or all of the preferred characteristics described above.

Regardless of the type of holder and diffuser element configuration employed, all parts of the element that allow air to escape into the surrounding liquid are readily accessible to the water, maintaining contact with the water in the outflow area and reducing surface tension. It is preferable to support the element so that it is affected. Therefore, it is preferable to avoid a situation in which the side surfaces of the element are in close proximity to voids that would exclude water by air released from the side surfaces of the element. Air exiting the element adjacent to the air gap does not have to overcome surface tension, so the air is preferentially directed to this part of the element, adversely affecting the uniform flow distribution from the element. However, if the support means and other structures are formed and placed in a shape and position that allows easy access to the liquid, any exposed surfaces that allow the air of the element to flow into the liquid can be eliminated, and the above-mentioned distribution defects can be eliminated. . Alternatively, the part of the diffuser element that releases air into the above-mentioned voids can be sufficiently compressed by proper positioning of a closure member shorter than the element, or by applying an impermeable coating to the surface, or by sufficiently compressing the sides or parts that come into contact with the water. It can be blocked by making it nearly impermeable. However, suitable diffusing elements include porous, at least semi-permeable, free of sticky substances that inhibit the formation of bubbles, and "vertical" (including near vertical, e.g., inclined at about 20° from vertical). ). Further preferably such vertical or nearly vertical edges are covered by a combined structure of plenum, closure means and retention means. According to a preferred embodiment of the invention, which will be described in detail below, the closure means is shorter than the length of the diffusing element and is formed by the intersection of a vertical or nearly vertical side surface with an upper opposing portion of the upper gas emitting surface of the element. located at the upper edge defined.

Diffusion elements are commonly installed in natural or man-made reservoirs, such as lakes, lagoons, or tanks, most commonly large tanks of concrete construction for activated sludge treatment of domestic sewage. The diffusion elements are arranged in one or more rows in the reservoir and connected to the gas distribution network, supported at various heights and provided with suitable pressure or flow control devices, or separate compressors, to provide various Ensuring proper distribution of aeration gas to the elements at height. Preferably, however, all elements communicating with the same gas distribution network within a given tank are mounted at approximately the same height.

1-18 illustrate particularly preferred embodiments of apparatus for use in connection with the present invention. In Figure 1 a sewage aeration tank 1 is shown, which tank is provided with a bottom wall 2, side walls 3 and end walls 4 for containing the sewage to be aerated. A compressor 5 is provided, and the air passing through the atmosphere is collected through a valve 6A, a flow rate indicator 7A, and a branch pipe 1.
It is supplied to the air main pipe 8 through 8A. storage tank 1
9 contains a high pressure cleaning gas which is discharged via valve 6B, flow indicator 7B and branch pipe 18B into main pipe 8 for controlled or predetermined mixing with compressed air. The operation of the valves 6A, 6B starts, stops and controls the discharge of aeration and cleaning gas, so that the above-mentioned elements are used to supply the aeration gas to the distribution network and also to supply a mixture of aeration and cleaning gases. The means for supplying the distribution network either continuously or intermittently is provided.

It is common practice to provide a main air pipe 8 in the distribution network, which is supported above the liquid level in the tank 1, and which is connected to a lower feed pipe 9. extends vertically from the main air pipe 8 to a distribution pipe 10 supported substantially horizontally slightly above the bottom wall 2. By the distribution pipe 10,
It also feeds into a parallel array of terminal tubes 11 supported slightly above the bottom wall 2. The spacing between the terminal tubes 11 and the diffusers or differential users 12 arranged on a horizontal plane is determined based on criteria known to those skilled in the art.

In a preferred embodiment, the main pipe 8 and the lower pipe 9 are made of metal, and the distribution pipe 10 and branch pipe 18B are made of synthetic resin. The lower feed pipe 9 and the pipe 10 are connected by a gas-tight pipe joint (not shown). In such embodiments, the branch pipe 18B is
As shown in the figure, it is inserted into the main pipe 8 at the intersection with the main pipe 8, but it is not communicated with the main pipe 8, but is extended continuously within the main pipe 8 and the lower feed pipe 9, and is inserted into the downstream area of the joint and the tank. It reaches the discharge outlet of the tube 10 below the liquid level. Alternatively, the branch pipe 18B can be connected separately from the main pipe 8 directly to the pipe 10 in a submerged position downstream of the joint.

In FIG. 2, an enlarged partial perspective view of the terminal tube 11 including the differential user 12 is shown.

As shown in FIGS. 3 and 4, the terminal pipe 11 is provided with outflow openings 13, and these openings are formed at regular intervals along the center line of the top surface to direct air to the differential user 1.
2 plenums 14. Each plenum 14 is provided with lower wall means 15. The cross-sectional shape of all or most of this lower wall means is circular and adapted to the outer surface 16 of the tube 11. Connect the lower wall 15 to the pipe 11
are closely interlocked in various ways as well as in various mechanical configurations. For example, clamps or straps can be used, but are preferably adhesively bonded to the tube. Generally any bonding technique can be used, but if the tube is made of polymeric material (which is the preferred material) it may also be attached by melt bonding or thermal shock (including ultrasonic) bonding. can. Thermal shock bonding is advantageous in terms of simplicity and economy. Depending on the type of attachment means used, the plenum is sealed off to the tube either by the same means or by diffusion means. An elastomeric sealing member may also be provided between the plenum bottom wall means and the outer surface 16 of the tube, and the sealing may be by welding or gluing as described above.

When using polymeric tubes and polymeric material plenums from a structural integrity standpoint, the lower wall means 1
Advantageously, 5 can closely engage the longitudinal and cross-sectional portions of the outer surface 16 of the tube.
The adaptation of the lower wall 15 to the cross-section of the tube is at least approximately 20°, at least in the intermediate section 17 of the lower wall means;
Preferably, the fit spans an arc of about 45°, more preferably about 70°. In the preferred embodiment shown in FIGS. 3 and 4, it is approximately 90 degrees.

As shown in FIGS. 3 and 4, the lower wall means 15 is provided with an air inlet 22, and around the inlet a slightly protruding boss 23 is provided on the inner surface of the plenum lower wall means 15. Air outflow opening 13 and inflow opening 22
keep them aligned with each other.

In accordance with the invention, a flow regulating device or regulator is provided, one embodiment of which device is designated at 24.
According to a preferred embodiment, the tube, the bottom wall means 15, and the flow regulator or sleeve member 25 for attachment to the flow regulator form a combined joint assembly. For example, all of these parts can be glued or welded at the same time, which saves considerable manufacturing steps and costs. Flow rate adjustment device 24
and various modifications of this member will be explained in detail below. The lower wall means 15 can have any desired shape in plan view. For example, the outline can be square, rectangular, circular, oval,
An oval shape is preferred. Air inflow opening 22 and flow rate regulator (hereinafter referred to as "regulator") 24
It is advisable to place both of them within this outline when viewed from a plan view.

In FIG. 5, a longitudinal cross-sectional view of the regulator 24 of FIGS. 3 and 4 is shown. In this embodiment, the regulator is a plug member with a central cavity that communicates with the interior of the tube 11 through the open bottom wall of the sleeve 25. A pair of horizontal orifices 33 extend laterally from the cavity 32 and communicate with the interior of the plenum 14. These orifices 33 communicate directly with the interior of plenum 14 as shown in FIGS. 3 and 4. However, if the outer end of the orifice 33 is covered with an elastic band 34 as shown in FIG. 5, it has unidirectionality, ie, acts as a check valve. This characteristic is useful when there is a temporary loss of air pressure in the end tube 11. The unidirectionality of the regulator maintains the pressure in the plenum 14 and prevents liquid outside the differential user from flowing back into the plenum through the diffusion element 35. This also reduces the difficulty in starting up the device when pressure is restored. Backflow of sewage through the diffusion element 35 or regulator 24 may clog these components, completely clogging the flow through the element and/or the device, or impairing flow distribution when pressurized air flow is restored. Make it uniform.

In FIG. 5A a so-called "duck-bill" unidirectional flow regulator is shown. This duckbill is made of a flexible and elastic material and is shaped like a duck's beak and has a lip with a normally closed slit. In this embodiment, the duckbill is attached to the sleeve 25A contained within the lower plenum wall 15 and the end tube 11, and the majority of the duckbill is located inside the contour of the end tube 11. A cylindrical body 37 and a horizontal slit 3 in the duck building.
A lip 38 ending at 9 and an annular flange 40 are provided, and the annular flange 40 is closed within the sleeve 25A by a concentric collar 41 secured to the sleeve 25A. An inward flange 42 forming a central opening 43 at the lower end of the sleeve 25A supports the duckbill from below and communicates with the inside of a cylindrical body 37, which allows the inside of the tube, between the lips 38 and Air can be communicated to the interior of the plenum 14 via the slits 39.
The orifice created upon opening of the slit 39 changes in response to pressure and closes when flow toward the plenum ceases. Therefore, it functions as a check valve like the modified example shown in FIG.

5B and 5C, a regulator is shown having a plurality of passages having a high length to cross-sectional area ratio. The regulator of FIG. 5B is provided with a stepped cylindrical housing 47 at the lower end 4 of the housing.
8 can be reduced in cross-section and its lower end can be tightly fitted into the air outlet openings 13 and inlet openings 22 of the end tube 11 and the lower plenum wall 15, and these components can be welded into an integral assembly. The housing 47 has a circular lower bottom 49 with an air inlet 50 as shown in FIG. It projects upwardly beyond the top of the housing 47. An annular porous plug 52 is arranged in the large diameter part of the housing 47, and this plug connects the support column 51 and the housing 4.
7 fills the space between the side walls. O-rings 52 and 53 prevent airflow from bypassing between the outer periphery of the plug 52 and the inner wall of the housing 47;
This O-ring 53 is placed adjacent to the plug and compressed between the plug and the step of the housing 47. A flexible sealing wing 54 prevents air from bypassing the center hole of the plug 52 between the plug and the strut 51, and a nut 58 screwed into the washer 55 and the strut 51 connects the wing 54 to the upper surface of the plug. The central part of the block is interlocked. The flexibility of the winglets 54 allows the outer edges of the winglets to rise when air passes from the interior of the terminal tube 11 through the porous plug 52 to the upper surface of the plug. Air exiting from the top surface of the porous plug thus passes between the upper edge of the housing 47 and the wing edge edge 57, which acts as a unidirectional valve. When flow through the porous plug 52 ceases, or when flow begins in the opposite direction, the wings close, preventing gas from flowing back into the end tube 11.
Alternatively, the bypass effect described above can be controlled by providing an impermeable coating to the central hole and surrounding walls of the plug 52.

Similar to FIGS. 3, 4, and 5, FIG. 5D shows a regulator that can be easily removed and replaced. In this embodiment, a portion of the regulator is placed within the plenum 14 and another portion within the tube 11. The sleeve 25B is connected to the terminal pipe 11 and the air outflow opening 13 and inflow opening 22 of the plenum lower wall 15.
Place it in Similar to the regulators of FIGS. 3, 4 and 5, the regulator of FIG. 5D is provided with a cylindrical cavity 32 which is open at the bottom and communicates with a horizontal orifice 33. The cylindrical body 60 of this regulator is snugly fitted into the cylindrical hole of the sleeve 25B, and the body 60 is provided with two annular grooves, an upper groove 61 and a lower groove 62, each of which has an O-ring 63. , 64 are installed. The outer diameter of the upper O-ring 63 is made slightly larger than the inner diameter of the sleeve 25B to block the flow from the terminal tube 11 to the inside of the plenum 14 through the space between the cylindrical body 60 and the inner surface of the sleeve 25B. The outer diameter of the lower O-ring 64 is made slightly larger to perform the function of holding the regulator in place.
The O-ring 64 is made sufficiently compressible, the groove 62 has a large space, and the O-ring 64 is placed at a predetermined position in the groove 62.
A cylindrical body 60 having a ring 64 is attached to the sleeve 2
5B and pushed into the sleeve 25B to the position shown in FIG. 5D, where the O-ring 64 expands and crimps against the tapered lower inner surface 65 forming a detent at the lower end of the sleeve 25B. be able to do so. O-ring 64
The outer diameter of the regulator is large enough to hold the regulator in place under normal operating pressures, but also to allow for withdrawal of the regulator without destroying the regulator or sleeve 25B, and to provide different flow characteristics. It can be replaced with a regulator that has one. This means that the diffusion element 35
This is advantageous when it becomes necessary to replace the (see FIGS. 3 and 4) with an element of a different head loss, or when it is desired to change the overall operating characteristics of the aerator.

In Figures 3, 4, 5 and 5A-5D above, several regulator embodiments are shown that attach to the cross-sectional area of the plenum and/or end tubes. However, the various flow regulating devices or regulators described herein have in common that they are disposed within a member that terminates below the diffuser element 35. Those skilled in the art will readily be able to mount various regulators in a variety of ways.

The side wall means 26 is connected to the periphery of the lower wall means 15 as shown in FIGS. 3-5. This side wall can be sloped vertically or inwardly or outwardly from the lower wall means. Preferably the side wall means are connected to the entire periphery of the lower wall means and slope inwardly or outwardly from the lower wall means. Diffusing element support means is provided on the side wall means spaced upwardly and outwardly from the bottom wall means. Such a support means is provided with a horizontal annular shelf 27 whose inner and outer diameters are smaller and larger than the diameter of the lower edge of the diffusing element 35, respectively. If desired, the shelf 27 is part of a step of the side wall means 26, with a cylindrical, generally vertical wall 21 provided below the step. Although the diffusing element support means can be located at any location on the side wall means 26, it is preferably located at the uppermost and most outwardly protruding portion of the side wall means 26. More preferably the side wall means are conical.

In accordance with the preferred embodiment of the invention shown in FIGS. 3-4, the plenum is provided with an integral, substantially vertical upright wall 28 which, when viewed in plan, provides diffuser support means, such as a horizontal annular shelf. The section 27 is surrounded.
If the wall 28 is provided (it is preferable to provide it),
The height of the upright wall 28 is made approximately equal to the height of the diffusion element 35. Wall 28 is provided with a generally upright inner surface 29, a top edge 30, and a threaded outer surface 31. In a preferred embodiment, shelf 27 and upright wall 28 define a socket for receiving a diffusing element 35 within which is shown in FIG. 3 and enlarged in FIG. accommodate the whole.

The most preferred diffuser element is a circularly contoured ceramic plate with stepped edges and a circular flat central area 7, as shown in FIGS.
0, an annular inclined edge 71, an annular flat surface 72,
An outer annular inclined surface 73 and a horizontal annular surface 74 are provided, and the outer diameter of these portions is 11.43 cm (4.5 cm).
inches), 16.51cm (6.5 inches), 19.30cm (7.6 inches), 22.10cm (8.7 inches), and 23.50cm (9.25 inches). The angle of inclination of the outer annular inclined surface 73 with respect to the horizontal plane is 25°. The heights of the horizontal annular surface 74, the top edge of the vertical side surface 75, and the annular flat surface 72 are 1.27 cm (0.5 inch), 1.78 cm (0.7 inch), and 2.54 cm (1.0 inch), respectively.

The plates have an average transverse and longitudinal dimension of 0.51 mm (0.020 inch) and 0.81 mm, respectively.
(0.032 inch) and a ceramic binder that accounts for 20% of the weight of the alumina particles as 100%.
Press with ram with flat surface and diffusion element 35
This mixture can be consolidated by means of a cylindrical die cavity having a bottom wall of a shape corresponding to the top surface of the die.

The sides of the die cavity and the ram are made to correspond to the diameter of the peripheral edge 76 of the diffusion element 35, and the height from the bottom of the die cavity to the top edge is 3.81 cm.
(1.5 inches). Pour this mixture into the cavity in a heaping amount and scrape it down to the level of the top of the die, then approximately 63.28Kg/cm ² (900Psi)
Compress to the specified dimensions with a pressure of After the compacted material is removed from the press, it is baked in an oven at a temperature sufficient to melt the binder, and then slowly cooled. This result is 6.75×10 ⁵ ±8.1×14 ⁴ cm ³ /min
A uniform porous ceramic diffusion element with a permeability of (25SCFM±3SCFM) is produced.

A diffusing element, which may or may not be of the preferred type described above, is supported within the plenum on support means. a sealing means is provided adjacent to the periphery of the diffusion element;
Prevent air from leaking through the periphery of the element.

In the preferred embodiment shown in FIGS. 3, 4 and 7, a polyisoprene O-ring 80 having a shore A durometer of approximately 40±3 is placed in an annular step formed around the upper portion of the circumferential surface of the diffusing element 35. . O
The diameter of the cross section of ring 80 is determined by the diameter of the cross section of ring 80.
6. Slightly greater than both the spacing between the inner surface 29 of the upright wall 28 and the vertical or nearly vertical side surface 75 of the element 35 opposite this inner surface, and the height of the vertical or nearly vertical side surface 75.

The preferred retaining means of the present invention, shown in FIGS. 3, 4 and 7, is an internally threaded clamp ring 84 which includes a cylindrical portion 86 having internal threads 86.
5 and whose internal threads 86 align with the external threads 31 of the upright walls 28 of the plenum. A flange 88 is attached to the cylindrical portion 85 above the screw 86,
This flange projects inwardly into the upright walls of the plenum and covers at least a portion of the top surface of the sealing means or O-ring 80. According to the preferred embodiment, this flange 88 does not cover the inner upper quadrant of the cross-section of the O-ring 80 (as shown in detail in FIG. It tightly engages the top of side surface 75 proximate edge 89 between 75 and the adjacent upwardly sloping surface 73, thereby preventing the formation of voids in the side surfaces of the diffusing element. When this gap is created, communication is created with the water above, and the gap itself allows gas to flow out.

In FIGS. 8 to 14, a plenum, a diffusion element,
Figure 5 shows various other embodiments of combinations of closure means and retention means; In each of these embodiments, a plenum sidewall means 26, a horizontal annular shelf 27, and a generally vertical upright wall means 28 are provided, the upright wall means having a height approximately equal to the height of the diffusing element ( 35 and 35A to 35G)). For example, in the embodiment of FIG. 8, the upright wall 28 includes a peripheral flange 90.
Bolt holes 91 are provided that are spaced apart from each other in the circumferential direction, bolts 93 are passed through these bolt holes, and a plurality of clips 92 that are spaced from each other in the circumferential direction are fastened to the flange 90 and the upper surface of the diffusion element 35A. An elastomeric band or hoop 95 acts as a sealing means. The unstretched inner diameter of the hoop or band is approximately 85% of the outer diameter of the diffuser element 35A, and the width is slightly greater than the vertical thickness of the diffuser element. When placed around the diffusion element 35A and in an expanded state, the width of the band expands to form an inwardly facing upper edge 97;
It produces an inwardly directed lower edge 98 and a cylindrical center 96 surrounding the upper and lower edges 99, 100 of the element. Inward lower edge 9 crimped onto horizontal annular shelf 27
8, the interior of the plenum is divided into upright walls 28 and elements 35.
Seal off from the vertical space between A and A. The central portion 96 of the elastomer band allows air to diffuse into the diffusion element 35.
A and prevent it from penetrating into the gap between the element and the upright wall 28. This is an example in which the retaining means only engage the element and not the sealing means, so that contact does not occur over the entire periphery of the element.

In the embodiment of FIG. 9, a second
A horizontal shelf 105 is provided and an outwardly projecting horizontal flange 106 is provided at the upper edge of the upright wall. Diffusion element 35B
A non-permeable coating 107 is provided on the peripheral edge of the element, extending to the height of the circumference or side surface of the element, and the side surface of this coating 107 is crimped onto an O-ring sealing means 80 disposed on the shelf 105. This sealing means 80 is tightly fitted between the diffusion element 35B and the upright wall 28.
The O-ring 80 is held in place, i.e. prevented from moving upwardly, by a cylindrical retaining ring 108, which is provided with a plurality of circumferentially spaced inward protrusions 110 on its inner surface 109;
These protrusions are crimped onto the upper surface of the element 35B at limited protrusions at wide intervals. The retaining ring 108 further includes an annular flange 111 that integrally projects outward.
, and the flange 111 is substantially coincident with and located on the outwardly projecting flange 106 connected to the upright wall 28 . These two flanges are held together by a split ring clamp 116 of approximately C-shaped cross section, which is provided with lips 112, 113 having curved inner surfaces, the inner surfaces of these lips being formed on the upper and lower surfaces of the flanges, respectively. The annular pawls 114 and 115 are engaged with each other. The vertical flexibility of the lips 112, 113 and the radial division (not shown) of the split ring clamp 116 allows the ring clamp to firmly hold the flanges 111 and 106 with a snap action, while the protrusion 110 Diffusion element 35B
in place, the underside of ring 108 does not clamp O-ring 80, but prevents upward movement of O-ring 80.

In the embodiment of FIG. 10, another embodiment is shown which is identical in many respects to the embodiment of FIG. Diffusion element 3
A non-permeable coating 107 is provided on the side surface of 5C to face the upright wall 28. As in the embodiment of FIG. 9, a second horizontal annular shelf 105 is provided on the upright wall 28, an O-ring 80 is disposed on this shelf, and this O-ring is held in place by a retaining ring 108. The ring 108 is provided with an inner surface 109 and a protrusion 110. However, instead of the above-mentioned flange 106, an integral pawl portion 120 is provided which is formed around the entire circumference of the outer surface 121 of the upright wall 28, and the retaining ring 108 is provided with an outer portion spaced apart from each other in the circumferential direction in order to engage the pawl 120. A downwardly directed and then inwardly projecting hook 122 is provided to hold ring 108 in place, prevent upward movement of O-ring 80, and protrusion 110 securely holds diffuser element 35C.

In FIG. 11, the horizontal annular shelf 27 is provided with an inwardly upright lip 27A which holds in place a generally rectangular cross-section sealing means 125 on which the lower surface of the diffusing element 35D is shown. Place the periphery of. The side surface 127 of the element 35D is opposed to the upright wall 28 with a narrow gap 131 in between. However, the side surface 27 is covered with a non-permeable layer to form the void 1.
31 and this layer is provided with an annular portion 126 above the sealing means 125 and a peripheral edge 128 on the side of the element adjacent to the cavity 131. Element 35D connects internally threaded clamp ring 129 to upright wall 28.
by engaging the threads on the outer surface of the sealing means 125 to firmly hold it in place against the sealing means 125.

FIG. 12 shows an embodiment, similar to FIG. 7, in which the sealing means are arranged at the edge portion between the side surface of the element and the upwardly directed annular inclined surface. As shown in FIG. 12, the diffusing element 35E is placed directly on the horizontal annular shelf 27 and is provided with a non-permeable peripheral coating 128, which allows the element to escape from the air gap 131 created between the element and the upright wall 28. Seal the sides. In this embodiment, the closure means 133 has a hybrid cross-section, with a semi-circular profile in the upper part and a rectangular profile in the lower part. The semi-circular portion of the closure means 133 is engaged by the correspondingly shaped underside of the annular flange 134 of an internally threaded clamp ring 135, which engages a thread 136 formed on the outer surface of the upright wall 28. Drooping short lip 13 at the lowermost edge of the flange 134
7 forces the closure means 133 outwards and downwards so that the flat outer surface 139 and the flat bottom surface 1 of the closure means
38 to the inner surface of the upright wall 28 and the upper surface 1 of the diffusion element.
40, especially the edge 141 where the top surface intersects the side surface 142 of the element.

In Figures 7 and 12 an embodiment is shown in which the height of the sealing means is considerably lower than the height of the diffusion element and is arranged at the edge where the side surface of the diffusion element meets the top surface from which the gas is released. Further, in these two types of embodiments, an example is shown in which the electrodes are arranged adjacent to the lower side of this edge, and adjacent to the upper side of this edge. However, it is also possible to provide sealing means that cover part of the element above and below this edge. These various suitable shapes make it possible to eliminate the drawbacks caused by the above-mentioned voids. That is, the voids allow water to freely pass through, reducing the surface tension of the portion of the device adjacent to the voids, thereby disrupting the uniformity of air distribution through the device. The sealing means at such edges may be replaced by means for reducing the permeability of the sides of the element, such as bands 95 and 9 of FIG.
It is particularly advantageous when used in combination with the non-permeable coatings 107 and 128 of FIGS. 12-12 or the stepped sides of FIG. In the case of a stepped configuration, the material of the diffusion element below the horizontal annular surface 74 and adjacent to the circumferential surface or side surface 76 is sufficient to reduce the permeability compared to the upwardly directed surfaces 72, 73 that emit gas. undergoes compression. The circumferential surface 76 may be merely of reduced permeability compared to the upwardly directed gas ejection surface, or it may be substantially non-permeable. The property of having less permeability compared to upwardly directed gas release surfaces (which may also be substantially non-permeable) is advantageous in combination with the edge-located sealing means described above. This combination eliminates the drawbacks mentioned above due to air gaps and short circuits in which air passes from the plenum to the emitting surface of the element along air channels of different lengths. Therefore, the combination of the reduced permeability flanks and the closure means at the edges described above is a preferred embodiment of the invention.

In FIG. 13, an embodiment similar to that described above is shown, in which the diffusing element 35F is placed directly on the horizontal annular shelf 27. In this example, element 35F
An annular recess 143 is provided at the upper edge of the side surface 144 of. Side surface 144 and lower part 14 of recess 143
5 and the upper part 146 are covered with a non-adhesive cover or an impermeable coating 147. An O-ring sealing means 80 is placed within the recess 144 and tightly fits the impermeable covering 147 and the inner surfaces of the upright wall 28 and engages the curved surface between the upper and lower portions 145 of the recess. O-ring sealing means 80 is tightly clamped in place by an internally threaded sealing ring 149 that engages threads 150 on upright wall 28, thus holding diffuser element 35F in place.

In the embodiment of FIG. 14, the diffusion element 35G
A step 151 is provided on the side surface of the step, and this step includes a substantially horizontal annular surface 152 and a vertical cylindrical surface 153.
Cover both sides with non-adhesive cover or non-transparent cover 1
Covered by 54. The remaining portion of the side surface of the element 35G is a lower cylindrical surface 155, and this cylindrical surface does not necessarily need to be provided with a non-transparent coating. In this case, the O-ring closure means 80 are arranged on four sides: the surfaces 152, 155 of the diffusion element, the horizontal annular ledge 27;
and is pressed against the inner surface of the upright wall 28 and compressed. The step 151 rests on the O-ring 80 and is therefore not directly supported by the diffusion element support means. The diffusing element is clamped in place by an internally threaded clamp ring 156 that engages threads 157 on the upright wall 28. The annular flange 158 of the clamp rig 156 is provided with an inner surface 159 of approximately the same diameter as the side surface 153 of the diffuser element. Projections 160 provided spaced apart from each other in the circumferential direction of this inner surface 159 are made to slightly protrude toward the upper surface of the element 35G.
Holding 5G in place. In this way, the diffusion elements 35G are clamped only at positions spaced apart from each other on the periphery.

As shown in FIG.
1 , such that the surface 16 forms the lower wall of the plenum 14 .

In the embodiment shown in FIGS. 16, 17 and 18, the differential user 175 is provided with a vertical side wall 181. As shown in FIG.
, which forms the lower wall of the plenum 182. Although the wall cross section is shown as having a rectangular shape, it can also have a curved shape, including circular, elliptical, or irregular shapes.

In FIG. 19, a suitable apparatus for obtaining hydraulic pressure and/or network backpressure at any point under various operating conditions is shown. This device allows setting standards for comparison in other conditions. In this figure a longitudinal section through the terminal tube and the regulator and associated plenum and diffusion elements is shown, showing the location of the pressure taps, bubble tubes and auxiliary equipment necessary to obtain the pressure in question. A pressure tap and a series of line-supplied manometers or other suitable pressure measurement locations are used to take the various desired pressure readings. Air source A can be a separate compressor or a tap to an aerator, and this air source allows bubble tube B to be
The lower open end of the bubble tube is placed at the same level as the emission surface of the diffuser element. The pressure detected in line 1 represents the hydrostatic head applied to the diffusion element. Apply this pressure to line 1
read from a pressure gauge connected between the air pressure and the atmosphere. Dynamic pressure is read from pressure gauges connected to line 1 and line 2. If a flow regulator or regulator with a gas orifice or gas opening with known pressure/flow characteristics is used, and if the atmospheric pressure and other information necessary to make the necessary calculations are available, the flow rate through the element will be within the line. It can be calculated based on the pressure read from a pressure gauge using 2,3. temperature measuring means, such as thermometers or transducers, at any convenient location, submerged or non-submerged, within or outside the gas distribution network, sufficiently related to the temperature of the gas passing through the above-mentioned regulator;
Temperature information representing this temperature is obtained so that the flow can be calculated with the necessary accuracy. It is preferably located adjacent to (including immediately upstream of) the regulator used to read the pressure of the diffusion element, or as close as possible to this regulator.

At Nos. 20, 20A and 20B, an apparatus for measuring bubble release pressure is shown. In FIG. 20, a plan view of the diffusion element is shown in the upper part of the drawing, and a longitudinal section of the element is shown in the lower part of the drawing. The element is provided with an annular peripheral region 229 (see FIG. 20B), a vertical cylindrical edge 230, a horizontal annular surface 231, a vertical side surface 232, a gas inlet surface 234 and a gas outlet surface 233. However, the gas outlet surface 233 can also be used as a gas inlet surface, in which case the surface 234 becomes the gas outlet surface. FIG. 20 further shows the method for testing the bubble release pressure of this plate. Apparatus for performing such a test is shown in the lower part of FIG. 20 and in FIG. 20A.

In this embodiment of the test device, a tank 240 with a bottom wall 241 and side walls 242, 243
(See Figure 20). Support members 244 and 255 are rested on the bottom wall 241, and the diffusion element is supported on these support members with the gas emitting surface 233 of the diffusion element facing upward below the water surface level 246. The compressor C is connected to the first hose 254 via a conduit 251, a pressure regulating valve 252 and a flow meter 253. This first hose is connected to the first horizontal leg 256 of the T-tube 255 . The T-tube is further provided with a second horizontal leg 257 and a vertical leg 258. A sealing ring 259 is provided around the open bottom end of vertical leg 258. The second horizontal leg portion 257 is connected to the second hose 26
3 to a pressure gauge 264, and this pressure gauge is provided with a scale 265. Liquid level 266 and 26
7 on the scale 265, the pressure inside the device can be measured. The test equipment is assembled carefully to ensure that all connections between the components are gas-tight.

T-tube 25 as detailed in FIG. 20A.
5 vertical legs 258 and sealing ring 259 constitute a test probe. The probe is formed, for example, from a standard laboratory glass T-tube and has a sufficient internal diameter to readily permit the required gas flow in and out through the standard rubber sealing ring or stopper shown. The bottom of this stopper constitutes the end of the probe, and the outer diameter 259A and inner diameter 259B of this end are 3/8 inch and 3/16 inch, respectively. When manually pressing the probe against the gas emitting surface 233 of the diffuser element, the area to be tested is limited. surface 233 by the underside of sealing ring or stop 259.
This stopper 25 forms a gas-tight seal against
Air passing through the lower adjacent element portion 9 is released into the liquid in the test area as bubbles 260. The stopper 259 is non-adhesive to the surface 233 so that the probe can be easily moved from one test position to another to take a series of pressure readings from which the bubble release pressure can be calculated. I can do it.

Reference lines 271 and 272 that are orthogonal to each other are drawn on the gas emitting surface 233 of the diffusion element (see FIG. 20). equidistantly spaced reference marks 273 are placed along the reference lines 271, 272 to indicate the probe position for locating the open end of the above-described probe shown in FIG. 20A;
This positioning is done in such a way as to produce a positive seal as described above. The regulating valve 252 is adjusted to produce a relatively low flow rate in response to the relatively high pressure from the compressor C, for example, 54 cm ³ /min (2×10 ⁻³ CF
Adjust so that it becomes M). As the gas bubble 260 is generated through the portion of the gas ejection surface adjacent to the probe, the pressure of the device is read from the scale of the pressure gauge 265. The bubble release pressure at the test point can be obtained by subtracting the hydrostatic head H between the gas discharge surface 233 and the water surface level 246 from the pressure read from the pressure gauge. By taking measurements of the bubble release pressure at a number of equally randomly set locations on the gas release surface 233, the bubble release pressure of this surface can be determined. However, in practice it has been found suitable and convenient to establish the pressure test position along the two mutually orthogonal reference lines shown. By testing along two such reference lines on a carefully manufactured diffusion element, a reasonably accurate approximation of the uniform distribution of airflow over the gas emitting surface can be obtained.

In the middle part of FIG. 2, a scale 27 corresponding to the position of the reference mark 273 on the reference line 271
A graph is shown having a horizontal coordinate axis 274 labeled 4A. A corresponding scale of pressure values is provided on the vertical coordinate axis 275 of this graph, and the pressure values read at the reference mark 273 of the reference line 271 are blotted onto the coordinates to draw a bubble release pressure curve 276. side wall 24
In tanks 240 where the spacing between 2,243 and the side surface of the diffusing element is large enough, the vertical cylindrical edge 230,
At the horizontal annular surface 231 and the vertical side surface 232, a gas release surface 233 adjacent to the vertical side surface 232
The bubble release pressure can be read similarly to the point above. Refer to the test position on the diffusion element and the corresponding position of the pressure plotted on the graph by dotted lines 280A, 28.
0B (vertical cylinder edge 230), 281A, 281B
(horizontal annular surface 231), 282A, 282B (vertical side surface 232), and 283A, 283B (edge of gas release surface 233). The test plot locations described above are shown in more detail in FIG. 20B.

Bubble release pressure indicates the pressure required to overcome surface tension when a bubble is released from the holes in the plate. It has been found that this pressure condition can be made considerably greater than the pressure loss due to friction in forcing gas from the air inflow surface of the plate to the gas discharge surface. This is especially true when the plate is formed from a hydrophilic material that is more easily wetted by water than a hydrophobic material.

It can be seen from the graph of FIG. 20 that the central region of the diffusion element exhibits the lowest bubble release pressure (BRP). The bubble release pressure gradually increases toward the peripheral region of the element, and the reference line 238A,
Maximum value 285A, 285B as shown by 238B
heading to This maximum value is based on testing at the gas release surface 233 adjacent the vertical side 232. Bubble release pressure testing at side 232, indicated by reference lines 282A, 282B, shows that the bubble release pressure reaches a second minimum value 286A, 286B in this region. Reference lines 281A, 281
Bubble release pressure measurements in the horizontal annular plane 231, indicated by B, yield a second maximum value 287 in this region.
It can be seen that the value reaches A, 287B. Finally, the vertical cylindrical edge 2 indicated by reference lines 280A and 280B
30, the second maximum value 287A, 28
It can be seen that the bubble release pressure in this region is slightly lower than that in 7B. The second bubble release pressure curve 276
Vertical side 2 indicated by minimum values 286A, 286B
The existence of a low bubble release pressure region at 32 was unexpected. The data collected along reference line 272 also allows a bubble release curve (not shown) to be drawn along reference line 272.

Since the amount of gas passing through a certain region of the diffusion element is an inverse function of the bubble release pressure in this region, a flow curve 277 can be drawn, which curve 277 shows the flow curve of the plate along reference line 271. shall be taken as a thing. Actual flow data for the center of the element is obtained by activating the element for a specified period of time using a reverse scale cylinder placed in the test area.
At the edge of the element, the flow rate is calculated based on the bubble release pressure. It can be seen that analysis of the flow curves thus obtained gives an indication of the uniformity of the gas flow distribution across the element. As shown in the gas flow curve 277, the peak value of the flow rate occurs in the central region of the diffusion element, and the gas ejection surface 233
The first minimum value 290A, 290 near the outer edge of
B (corresponding to the maximum bubble release pressure values 285A and 285B). Furthermore, second minimum values 286A, 286B and second maximum values 287A,
The peak value of flow rate 2 corresponds inversely to 287B.
91A, 291B and second minimum value 292A, 2
92B. The testing technique shown in FIG. 20 thus provides a much clearer and more accurate representation of the flow curve of the diffuser element than is practiced in the industry. Furthermore, it can be seen that the flow rate per unit area is large in the central region of such a diffusion element, and that other regions are also used for outflow. Excessive gas flow passing through one or more regions of the device can create very large bubbles and adversely affect the oxygen transfer efficiency of the device.

21-31, various shapes of diffusing elements are shown which eliminate the above-mentioned drawbacks. These elements are rigid, single-layer, porous diffusion elements, and the volume compression ratio is extremely high in the center and/or periphery of the permeation. The elements are formed from solid particles that are bonded or sintered into a porous compacted shape to provide shaping, compaction, and bonding strength.
As shown in the cross-sectional view, the element has approximately 1.62 x 10 ⁵ to 5.4 x 10 ⁶ cm ³ / at a pressure of 5.08 cm (2 inches) of water column.
Provide a horizontal section with a specific transmittance in the range of min (6-200 SCFM). The ratio of the maximum horizontal dimension of this horizontal section to the thickness of this section is approximately 4:1. Furthermore, an upper gas release surface is provided in this part, and this gas release surface is made almost horizontal so that the bubble release pressure in the water is approximately 5.08 to 50.8 cm (2 to 20 cm) in the water column.
inches). The center and border regions are located below the upper gas release surface. Pressure is applied to the solid particles within one or both of these regions, e.g. in the outer region between the central region below the gas emitting surface and the boundary region, with a volumetric compression ratio that is significantly greater than the material in the adjacent parts of the element. . Furthermore, the diffuser element is provided with a peripheral region in which it is provided with a lower permeability, or a greater density, or a lower height than the part surrounded by the above-mentioned boundary region or the part of the gas release surface.

In the above-mentioned element, the significant volume compression ratio of the central region is increased by distributing the above-mentioned particles before or during pressing. That is, the amount of particles per unit area in the central region is made larger than the amount of particles per unit area in the outer region.
The distribution of particles before or during pressing is achieved by increasing the amount of particles per unit volume in the central region. Furthermore, the amount of particles per unit area can be increased by pressing with a die that has a cavity, and the center of the cavity and the surrounding area are filled with particles deeply and shallowly, respectively. It will be done.

In these elements having a central region and an outer region, a significant volume compression ratio is obtained by making the thickness reduction ratio in the central region and the outer region, respectively, relatively large and relatively small during pressing. This can be done whether before or during pressing the height of the grain parts relative to the central region is the same or different, for example higher than the height of the grain parts corresponding to the outer regions. Larger and smaller rates of thickness reduction are achieved by press molds with ram and die cavities, in which the opposing compression surfaces have small and large clearances between the central region and the outer parts, respectively. This small clearance can be created by providing a ridge on the compression surface of the die cavity or by other means.

A large volumetric compression ratio within the boundary area of an element with a boundary area can be achieved in various ways, by applying relatively large thicknesses to the boundary area and to other parts of the element surrounded by this boundary area, for example to the above-mentioned outer areas, respectively. A thickness reduction rate and a relatively small thickness reduction rate are applied during pressing. In this case again a press is used which is provided with a ram and die cavity with opposing compression surfaces with relatively small and relatively large clearances relative to the boundary area and the other parts mentioned above. Small and large clearances can be created by ridges on the compression surface of the die cavity or the compression surface of the ram or by other means.

The elements described above can be formed in a variety of shapes, including, for example, those with flat surfaces and those with recesses in the upper or lower surfaces of the central region spaced inwardly from the periphery of the element. That is, the element can be provided with a central recess, ie, the gas inlet surface or the gas outlet surface or both can be provided with a recess. However, such a recess may or may not be provided over the same extent as the central region. The depth and area of the recess may be varied as required to enhance the uniformity of gas distribution across the horizontal gas emitting surface of the element, and the depth may be varied in portions or throughout the recess. You can also do it. It is also possible to provide one or more non-recessed areas within the contour of the recess. Furthermore, the above-mentioned high volume compression ratios can be obtained by sloping the gas emitting surface of the element above the boundary region outwardly and downwardly at an angle in the range of about 10 DEG to 80 DEG with respect to the horizontal plane.

The above-mentioned features assist in obtaining a diffusion element in which the gas emission characteristics are substantially uniform over the gas emission surface of the element and the coefficient of variation is approximately 0.25 or less, and this coefficient of variation passes through the center of the gas emission surface. The bubble release pressure is calculated based on measurements of bubble release pressure at at least about five equally spaced locations along each of the orthogonal reference lines.

The above-described elements can be manufactured in any convenient manner. However, various manufacturing methods are shown in Figures 21-29.

These methods are variations of the methods described above. Similar to the methods described above, these variations also include a die 30 having a cylindrical cavity 302 defined by a compression surface or bottom wall 303 and side walls 304, 305.
Use 1. The die is filled with a mutually liberated mixture of solid organic or inorganic particles, which can be compressed and may or may not contain a binder to create a cohesive force. For example, bead-like particles or granular particles of synthetic resins such as polyethylene or polystyrene, glass beads, granular particles of metals, inorganic substances such as alumina, mullite, silica, etc. can be used. Organic and inorganic binders can also be included in the mixture. The mixture is compounded to create a bond by compression, sintering and/or bonding, for example by organic adhesive bonding, glass bonding, or ceramic bonding.

What is common to the known techniques is that the upper surface 306 and above of the die 301 are filled with particles 310 of solid material that are separated from each other. Next, the excess portion is scraped off with a screed. A ram with a compression surface 318 is then moved toward and engages the particulate material. Further, by moving the ram 317, the particles 310 within the cavity 302 are compressed and deformed into various compacted shapes. Ram 3
17 and the compressed body is taken out from the cavity 302. Based on the mixture used, the compact is baked to obtain the finished element.

According to a first embodiment of the modification method shown in FIGS. 21-23, starting with removing shaping ring 400, die cavity 302 is opened. Enough particle material is injected into the cavity 302 to fill it, and the raised portion above the die top surface 306 is leveled. A shaping ring 400 is placed on this surface, and this ring 400 has a flat upper surface 401 and a flat lower surface 40.
2, and a vertical circumferential surface 403 forming an outer edge. This ring is further provided with an inner conical surface 404,
The conical surface 404 defines a frusto-conical central chamber with an open top and bottom. This center chamber is empty since the particle material has been leveled to the level of the die top surface 306. The interior central chamber of this inner conical surface 404 is filled with excess particulate material 405 and then ground down by screed 312 to a surface 406 at the level of top surface 401 of shaping ring 400. Carefully remove the shaping ring and remove the cavity 3.
02 remains a particle body 407 having a raised central portion 408 consisting of a flat top surface 409 and a conical side surface 410.
However, this central portion 408 can have a variety of shapes.

The particles 407 and the technique described above for preparing the particles are one example of providing a greater amount of particles per unit horizontal area in the central region than in the outer surrounding area. In this case, a large amount of particles per unit horizontal area is obtained by filling the die part deeper than the surrounding part.

However, a large amount of particles per unit area can also be obtained by filling the center of the die with particles at a high density. For example, the die cavity may be filled, leveled to the top surface of the cavity, and then locally vibrated or pressure applied to the center region of the die to increase particle density. This causes the material in this area to sink more than the material in the surrounding area. The resulting depressions are replenished with particulate material before pressing. This method is an example of distributing a larger amount of particles per unit volume in the central area than in the outer surrounding area before or during pressing.

Regardless of whether the central region of the die is packed to a high height and/or high density, it is then compacted as shown in FIG. As a result, an element is obtained in which the volume compression ratio in the central region 413 (the region demarcated by the reference lines 413A and 413B) is higher than the volume compression ratio in the outer region 414, and in this case, the outer regions are indicated by the reference lines 413A and 413B. This results in an annular region delimited by the inner edge and the peripheral edges 414A, 414B of the element.

24 to 29 show other preferred embodiments that increase the volumetric compression ratio. In these drawings,
In particular, techniques are shown which produce relatively large and relatively small rates of thickness reduction in the aforementioned central and outer regions, respectively, during pressing.

One preferred embodiment is shown in FIGS. 24 and 25, in which a circular insert 421 forms a ridge on the compression surface 303 of the die cavity 302.
By arranging , a relatively large thickness reduction rate and a relatively small thickness reduction rate can be obtained. The insert 421 is provided with a cylindrical downward projection 422 which aligns with a corresponding socket 420 in the lower die wall 303. The upper part of the insert 421 has a conical surface 42
The shaping member has a flat top surface 424 surrounded by 5. Die cavity 302 in Figure 24
When filled, leveled with the contents to the level of top surface 306, and then compressed as shown in FIG.
30, resulting in a generally horizontal air discharge surface 431 having a central recess 432 consisting of a flat portion 433 and an angled edge 434. This method is an example of increasing the volume compression ratio of the central region of the diffuser element by creating relatively large and relatively small thickness reductions in the central and outer regions, respectively, during pressing. In this case, comparatively large and comparatively small thickness reductions are obtained by means of a press consisting of a ram and die cavity with opposed compression surfaces having small and large clearances for the center and surrounding parts, respectively. . In this case, the small clearance is obtained by the raised part of the insert 421 in the die cavity. However, the method can also be implemented with a die cavity with a flat bottom wall and a ridge on the compression surface of the ram.

Various modifications can be made to the manufacturing method shown in FIGS. 24 and 25. The shape, depth, and area of the recess 432 corresponds to the gas emitting surface 43 of the element.
1 can be freely varied to obtain the desired level of uniformity. The shape of the recess can be any desired profile that provides uniform distribution of airflow. Preferably, however, the contour of the recess resembles the contour of the element. The cross-sectional shape can be varied within the contour of the recess. The bottom of the recess can be constructed entirely of straight or curved surfaces or by a combination of straight and curved surfaces. The center of the recess may be flat as shown, or may be slightly curved throughout, or may be very flat, conical, or any other convenient and preferred shape to achieve the objectives of the invention. can do. Although a recess with a flat portion and sloped edges as shown is simple and preferred, it is not limited thereto.

As mentioned above, the area of the central recess does not necessarily have to be the same area as the central area of the element. The recesses can terminate within or outside the area defining the central region. However, it is preferred to define the recessed area to the same extent as the area that defines the central area.

The area and average depth of the recesses can be selected in combination to be sufficient to enhance the uniformity of gas distribution across the gas emitting surface of the element. For example, the area of the recess is about 10 to 80%, preferably about 25 to 70%, more preferably about 45 to 65% of the total area of the gas emitting surface of the element or the total area of the element, and the average of the recess is The depth is about 2 to 20% of the average thickness of the horizontal part of the element,
It can be suitably 4 to 15%, more preferably 5 to 10%.

The depth of the element can be varied within the contour,
That is, it can be changed stepwise or gradually, but the latter is preferable. Furthermore, it is also possible to provide some portions within the contour of the recess that do not form a depression. This embodiment is shown in FIG.

FIG. 26 shows an element that can be formed by a modification of the technique shown in FIG. 25. In this case instead of the insert 421 an annular insert 44
0, and the lower surface of the annular insert is provided with an annular rib 441 that engages a correspondingly shaped annular groove 442 formed in the bottom wall 303 of the die cavity 302. The annular insert 440 is provided with a flat top surface 443 having a beveled outer edge 444 and a beveled inner edge 445. When such a die cavity is used, as shown in the upper part of FIG.
2 can be done. The circular element is thus formed with a circular central region delimited by border lines 413A, 413B, which is surrounded by an outer region which is surrounded by border lines 413A, 413B.
From there, it reaches the peripheral surfaces 414A and 414B of the element.

In some cases, as in the embodiment shown in FIG. 27, the outer region of the element does not necessarily reach the peripheral edge. In this embodiment, the bottom wall 303 of the cylindrical die cavity 302 is provided with a circular insert 421 . A step is formed on the periphery of a portion of the bottom wall 303 adjacent to the side walls 304 and 305, and a vertical cylindrical surface 324 is formed on this step.
and a horizontal annular surface 325. With such a die, an element as shown in the upper part of FIG. 27 can be produced. This element includes a central region boundary line 413A,
Within the area 413B there is a gas release surface 431 having a recess 432 with a beveled edge 434. The vertical cylindrical surface 324 and horizontal annular surface 325 of the die form a vertical cylindrical edge 23 at the periphery of the element.
0, a horizontal surface 231, and a vertical side surface 232, defining a step at the edge of the element. Planar air inflow surface 430, vertical cylindrical edge 230, horizontal annular surface 2
31. The volume of the element bounded by reference lines 460A, 460B has less permeability, higher density, and lower average height than the permeability, density, and average height of the inner adjacent portion of the element. An annular peripheral region is defined. In this element, the outer region is defined by reference lines 413A, 413B on the inside and reference lines 460A, 460B on the outside.

FIG. 27 shows a method for improving the uniformity of air distribution in a porous gas diffusion element as shown in FIG. 20. Creating a peripheral region of low height, high density, and low permeability not only affects the flow properties of the peripheral region itself, but also of the relatively inner parts of the element. , resulting in a tendency for the flow to concentrate in the central region. By increasing the volumetric compression ratio in the central region, the above-mentioned tendency is counteracted, equalized, and eliminated.

In Figure 28 it is shown how a border region is provided adjacent to the peripheral region of the diffusing element.
As can be seen from the description of the unrecessed element in FIG. 20 and the testing of the element in FIG.
A, 286B is shown, and the corresponding dotted line 282
As shown by A and 282B, the flow rate curve 277 shows peak values 291A and 291B. The tendency for flow to peak in this region of the device is considered undesirable based on a number of factors. This is due to the configuration of the holder and sealing means used to attach the element to the diffuser. Vertical side 232
If the element is mounted in such a way that the air bubbles freely emit into the medium to be aerated, this side tends to produce undesirably large air bubbles and flows.
Additionally, if surface 232 releases air bubbles into the voids through which water freely passes (and therefore has no surface tension),
A disproportionately large amount of the total air volume is transferred to this surface. This tendency can be counteracted and evened out by a combination of various techniques, such as covering the surface 232 with an impermeable layer held in place or deposited, properly designed. Use of sealing means and diffusive element holders, No. 28
This tendency can be addressed by modifications as shown in the figure, by a combination of these methods, or by any other necessary means.

FIG. 28 shows an embodiment of a diffusion element in which a boundary region is provided adjacent to the inner side of a peripheral region, and the volume compression ratio of this boundary region is made larger than the volume compression ratio of the above-mentioned outer region to compress solid particles. shows. This is achieved by changing the die cavity 302, with a vertical cylindrical surface 324 and a horizontal annular surface 324.
An annular band 461 is provided on the inner surface of the bottom of the stepped portion formed by 5 and 5. This annular band forms an angle in the range of about 10 DEG to 70 DEG in the horizontal plane or in the plane of the aforementioned outer region (particularly if the plane of this outer region is not horizontal). In other respects the die of FIG. 28 is identical to that of FIG. 27. The embodiment of FIG. 28 is therefore a press consisting of a ram and die cavity having mutually opposing compression surfaces with relatively small and relatively large clearances between the compression surfaces corresponding to the boundary region of the diffusion element and parts of the above-mentioned outer regions. This is an example in which a relatively large thickness reduction rate and a relatively small thickness reduction rate are obtained by press molding. In this case, the small clearance is obtained by the bulge produced by the annular band 461 on the compression surface of the die cavity.

When an element is press-molded using the die of FIG. 28, the molded element shown in the upper part of FIG. 28 has an inclined edge 462 forming an angle α with respect to the horizontal plane. A 25° angle is optimal for a plate of the type shown in FIG. The advantage of providing the sloped edge 462 could not have been anticipated when the idea of increasing the volumetric compression ratio of the central portion was conceived. However, the idea of forming the central recess and the experience gained from working with the bubble release pressure measurement technique described above have led to some hypotheses regarding the effectiveness of the beveled edge 462.

Bubble release pressure curve 276 of FIG. 20 as described above.
It is unexpected that a region of low bubble release pressure exists on the vertical side 232, as shown by second minimum values 286A, 286B. However, it seems that this phenomenon can be retrospectively explained by theoretically considering the flow of particles within the die cavity. That is, the solid particles between the ram compression surface 318 and the horizontal annular surface 325 experience greater compression than the adjacent solid particles between the ram compression surface 318 and the soybean bottom wall 303, so that the material above the surface 325 is inwardly compressed. A vector component of the downward force is generated, and some of the particles in this region are compressed and moved inward and downward. Vertical side surface 232, on the other hand, is somewhat shielded from such force vectors by the inner edge of horizontal annular surface 325, so that the material along surface 232 is compressed less than the material along surface 231, and thus the surface 232 would be given greater transparency and surface 231 would be given less transparency.

This annular band causes the material above the annular band 461 in the die of FIG. The inner edge of the boundary area is separated by reference lines 463A, 463B. This is believed to make the bubble release pressure and flow rate of surface 232 more balanced relative to the rest of the element (which is reflected in a reduction in the permeability differences discussed above). .

Another embodiment is shown in FIG. 29 that provides a relatively large thickness reduction and a relatively small thickness reduction. In this embodiment, the small clearance is obtained by providing a projection on the compression surface 318 of the ram 317. For example, as shown in FIG.
An annular rib is provided on the compression surface 318 of No. 17, and this rib protrudes over the entire circumference at a position slightly spaced inward from the periphery of the compression surface 318. The cross section of this rib can be of any desired shape, but an arcuate shape is preferred. The depth of this rib is suitable to match the periphery of the element and to increase the volumetric compression ratio to the desired level. A typical depth is similar to the depth of the central recess 432 described above.

In this example, die cavity 302
Although the annular band 461 of FIG. 28 may be provided, it is preferred to have a die cavity similar to that of FIG. 27 with a step defined by the insert 421 and faces 324, 325. When using the die cavity and ram 317 shown in FIG. 29, the elements formed are shown in the center of FIG. 29. The annular rib 466 creates a corresponding annular groove 467 in the air inlet surface 430 of the element. The position of the groove 467 is such that the contour of the groove shape intersects or is slightly inwardly aligned with the edge of the peripheral region or the extension of the vertical side surface 232. The annular groove 467 is therefore at least partially located within the boundary area of the element and slightly within the annular peripheral area 229.
stand out. The element having the annular groove 467 at the position shown in FIG. 29 is similar to the element shown in FIG.
Reference lines 413A, 413B; 463A, 463
B; central area separated by 460A and 460B,
An outer region, a border region, and an annular peripheral region and a cylindrical edge 230 are formed.

Elements with border regions are shown in FIGS. 28 and 29, and such elements have the advantage of increased bubble release pressure on the sides 232. Therefore, the 20th~
The drawbacks described for the device shown in FIG. 27 can be substantially or completely eliminated. Therefore, regardless of whether or not the central region has an increased volume compression ratio, and whether the peripheral region is semi-permeable or nearly opaque, the boundary regions inwardly adjacent to the peripheral region are By increasing the volume compression ratio, the characteristics of the device can be improved.

The advantages of providing a boundary area are explained in the 30th and 3rd section.
These figures are shown in the graph of Figure 1, respectively.
Diffusion element of Fig. 7 (no boundary area) and Fig. 28
The elements of the figure (with border regions) are shown. In this case, using the bubble release pressure test method shown in Figure 20 and the same graphical format as in Figure 20, the bubble release pressure (BRP) curves A and B for each element, respectively.
get. Comparing these curves shows that in the absence of a boundary region, there is a minimum in the bubble release pressure curve at the vertical side 232 of the element.
Providing a boundary region results in an increase in bubble release pressure at surface 232, as shown by curve B in FIG. Since the flow rate is inversely proportional to the bubble release pressure,
The presence of the border region can restrict the flow rate from the surface 232 to less than the flow rate through the center of the element.

Although the benefits of border regions have been illustrated by their effect on vertical sides 232, it can be seen that vertical sides are not required. For example, the upper surface of the boundary region is a non-vertical surface, and the entire surface from the upper surface of the element to the upper surface of the peripheral region is an outwardly downwardly inclined surface, for example, about 30° to 70° with respect to the horizontal plane, more preferably 35°. It can be made to form an angle of ˜60°.

In FIGS. 23 to 29, reference lines 413A, 4
13B: 460A, 460B; 463A, 463
B and the like have been used to illustrate the diffusing element with demarcation lines of various regions, such as a central region, an outer region, a border region and a peripheral region. These reference lines are not set at a constant ratio, nor are vertical lines actually drawn that clearly separate the regions in the actual product according to the present invention. In the diffusing element according to the invention, it is not possible to draw segment boundaries between regions where there is a large difference in density between the materials of mutually adjacent regions. These boundary lines actually have a certain degree of lateral extent.

According to embodiments of the invention, the volumetric compression ratio of the central region is at least about 2 relative to the volumetric compression ratio of the outer region.
%, preferably 2-20%, more preferably about 3-15%
Use a high diffusion element. These percentages are expressed as differences based on the volumetric compression ratio of the outer region. Similarly, in embodiments of the invention, the volume compression ratio of the boundary region is at least about 10%, preferably about 10 to 35%, relative to other parts (e.g., outer regions) of the diffusion element surrounded by the boundary region. , more preferably about 35-100% higher diffusive elements.

In principle, the present invention does not limit the pore size of the porous diffusion element, but by way of example the pore size may be between about 60 and 600 microns, preferably between about 90 and 400 microns, and more preferably between about 120 microns. In the range ˜300 microns, the size of these pores is calculated by applying the bubble release pressure to the equation D=30γ/P as defined in ASTM E-128. where D = maximum diameter of pore, γ = surface tension of test liquid (dyn/cm),
P=mercury column pressure (mm) In general, the diffusion element according to the present invention has a permeability of about 1.62×10 ⁵ to 5.4×10 ⁶ cm ³ /min (6 to
200SCFM), preferably about 3.24×10 ⁵ to 1.89×10 ⁶
cm ³ /min (12 to 70 SCFM), but approximately 4.05 for alumina and silica sewage aeration diffusion elements.
×10 ⁵ to 9.45 × 10 ⁵ cm ³ /min (15 to 35 SCFM) is optimal.

The bubble release pressure of a diffusion element according to the present invention may be about 2 to 20 inches of water column pressure;
More preferably about 10.2 to 38.1 cm (4 to 15 inches), but for sewage aeration diffusion elements about 12.7 to 38.1 cm (4 to 15 inches).
25.4 cm (5-10 inches) is optimal.

Although the techniques described above to increase the volume compression ratio have been used to improve the uniformity of flow distribution across the diffusion element, it is practically impossible to predict the degree of improvement based on the quality of the equipment used and the technical requirements. be.
However, certain types of diffusive elements can exhibit this effect. That is, the coefficient of variation of the gas release surface is determined based on the values of the bubble release pressure at at least five equally spaced positions on two mutually orthogonal reference lines passing through the center of the element and along the surface of the element. The value should be about 0.25 or less. More preferred diffusing elements have a coefficient of variation in the range of about 0.05 to 0.25, more preferably 0.05 or less.

As mentioned above, the solid particles in the boundary region of the diffusion element according to the present invention are compressed to a larger volume compression ratio than the particles in the outer region, giving the gas ejection surface above the boundary region an outward downward slope; This inclination is approximately 20° to 70°, preferably approximately 25° to the horizontal plane.
65 degrees, but a suitable sewage aeration diffusion element is optimally inclined at an angle of about 25 degrees.

At least a portion, preferably at least a majority, of the diffusion elements in a gas treatment apparatus are mounted in a separate plenum and each plenum and element in this section is provided with process gas and When supplying the cleaning gas, an effect occurs with respect to gas distribution and/or contamination rate and/or cleaning efficiency. The amount of gas released per unit area of a porous diffusion element influences the size of the bubbles formed and the efficiency of the diffusion element expressed as a fraction of oxygen or other process gas absorbed, e.g. oxygen transfer efficiency (OTE). . Large flow rates generally reduce this efficiency. Furthermore, when supplying a certain amount of air to a certain number of elements, efficiency is maximized when all diffusion elements operate at a uniform flow rate. However, in the manufacturing of diffusion elements, it is common for errors to occur in characteristics such as permeability and hydrodynamic pressure. Moreover, individual diffusing elements, usually manufactured by the same method and to the same specifications, differ significantly with respect to transmission and other properties. In Figures 32A-32B it is shown how the pressure/flow relationships for such elements can vary widely.

Assume that there are two diffusing elements and one element has a transmittance of approximately 12 and the other element has a transmittance of approximately 9. Furthermore, each of these elements is attached to an individual flow regulating means, and air is supplied through a common plenum at approximately the same pressure, so that each element has a flow rate of approximately 3.51×10 ⁴ .
Assume that a total air volume of approximately 7.02×10 ⁴ cm ³ /min (2.6 SCFM) is delivered for an average flow rate of cm ³ /min (1.3 SCFM).

Curves AB and CD in FIG. 32A show the air content of the above-described device at various pressure drops (measured in water column pressure), and the intermediate curve shows similar data for a device with an average permeability of 10.5. The flow rate through a permeability 9 element at a typical pressure drop of approximately 7 inches of water column pressure is approximately 1.62×
10 ⁴ cm ³ /min (0.6SCFM), and it can be seen that the flow rate of an element with a permeability of 12 is approximately 5.4×10 ⁴ cm ³ /min (2.0SCFM).

Figure 32B shows a plot of the pressure/flow characteristics of the two above-mentioned elements installed in separate plenums supplied with air from a common distribution pipe. supply is
This is done through a 7.93mm (5/16 inch) control orifice. In Figure 32B, curves A'B' and
C'D' indicates the air content of the two elements described above at various pressure drops, respectively, and similar data for an element with the average permeability of the two elements is shown by the intermediate curve. From two diffusion elements from the drawing
7.02×10 ⁴ cm ³ /min (2.6SCFM) flow rate (average
1.3 SCFM), the pressure drop is approximately 27.94 cm in water column pressure due to the action of orifice control.
(11 inches). Correspondingly, the flow rate through an element with a permeability of 9 is approximately 3.24×
10 ⁴ cm ³ /min (1.2SCFM), and the flow rate through an element with a permeability of 12 is approximately 3.78×10 ⁴ cm ³ /min.
(1.4SCFM). The ratio of the flow rates of the two elements in this case is about 3.3:1 in the previous case, whereas
The ratio is approximately 1.2:1. Therefore, it can be seen that it is more effective to use a diffusion element as an individual flow rate adjustment means in order to obtain the necessary air and power.

Other advantages result from the use of separate plenums fed through separate flow regulating means.
In the case of certain organic mucilages (which are known to significantly contaminate diffuser element surfaces at low flow rates), the difference in flow rate between diffuser elements of different permeability may be significantly reduced when the elements are mounted in a common plenum. The flow rate adjustment means increases faster than when installed in a separate plenum. Furthermore, it has the lowest permeability when cleaning.
Therefore, the elements most in need of cleaning receive the least amount of cleaning gas. Conversely, elements that have high permeability and thus require less cleaning will receive the greatest amount of cleaning gas. Moreover, the unbalanced flow relationships described above become increasingly unbalanced as the number of cleaning cycles progresses and the highly permeable diffusion elements are cleaned.

According to embodiments of the invention, the use of diffusion elements in the individual flow control means as described above results in devices that operate well and that at least about 90% of the diffusion elements (when in good condition) receive gas at a uniform pressure. about
±15% of the average flow rate of all elements when operating at 5.08 cm (2 inches) of water column pressure when new or used and unsubmerged after cleaning (more than 90%), and better still about It is possible to deliver a flow rate per unit area within a range of ±10%.

A particularly preferred embodiment of the invention is shown in FIG.
In this drawing, a part of an aeration device for tank type aeration treatment is diagrammatically shown. Bottom wall 47 on tank 470
1 and a vertical wall 472 for containing a liquid medium in the tank, the liquid level of which is indicated by reference numeral 474. The upper edge 473 of the vertical wall 472 is located at ground level and is provided with a passage (not shown) adjacent to the upper edge, which passage is provided with a conventional guardrail (not shown). In this case, the processing gas device 4
80 is an aeration network having a blower (not shown), which is equipped with a usual filter, pressure regulator, valve device, etc., and in-house piping 481.
connected to supply air. Actuation flange 4
Air is supplied to a lower feed pipe 483 made of stainless steel through a pipe 481 via a
4 to a joint 484 below the liquid level. At fitting 484, a corrosion resistant material, e.g.
Another down pipe, which is a plastic pipe made of PVC or polybutylene, is connected to the first down pipe 483.
This second lower feed pipe 485 is extended further below the tank to a sliding flange 486 and a T-shaped pipe 491, and via this T-shaped pipe, the lower feed pipe 485 is communicated with a substantially horizontal terminal pipe 487, and this terminal The tube is placed approximately perpendicular to the tank wall 472. Terminal tube 487
a plurality of short vertical connecting pipes 48 projecting downward from the
8, the terminal pipe 487 is connected to a plurality of distribution pipes 489 arranged in parallel to each other, and these distribution pipes 48
9 approximately parallel to the tank wall 472. Distribution pipe 4
Appropriate spacing along 89, for example about 30.4 cm ~
A plurality of diffusion devices or differential users 490 are arranged every 121.6 cm (1 to 4 feet), and these differential users have flow rate adjustment means as shown in FIGS. 2 to 6,
It includes a combination of plenum and diffusion elements. The diffuser element shall have the preferred characteristics described above for a porous diffuser element, have the characteristics and dimensions as described for the diffuser elements shown in Figures 3, 4, 28, and 28A, and be 2.54 cm (2.54 cm) thick. inch), area ^369cm2
Average transmission approximately 10.5±15 per (0.41 ft ² ) element
%.

In this embodiment, the gas cleaning device 500 is provided with a movable scale 501 comprising rollers, which is movable along the above-mentioned path of the tank edge 473, and is also provided with an indicator 502. A cylinder 503 for storing and discharging cleaning gas is rested on the traveling scale 501 and is connected to a gas regulator 504 and a valve 50.
5,506, flow meter 507, plastic pipe 50
8, and is connected via an elbow 509 to a portion 485 formed of plastic material of the lower conduit and located below the liquid level 474. Although the plastic pipe 508 is shown separated from the lower feed pipes 483 and 485 in this diagram, in reality it is advantageous to attach the plastic pipe 508 to the outside of the lower feed pipe or to pass it through the inside of the lower feed pipe. It is.

The combination of cylinder 503 and scale 501 described above is currently considered to be the most convenient configuration for supplying cleaning gas. However, various alternatives can be applied. For example, the cylinder 503 can be replaced by a burner, which burns a fuel such as oxidizable sulfur to generate a cleaning gas, such as sulfur dioxide. Alternatively, a liquid-gas contactor may be used instead of a cylinder, in which a liquid cleaning gas source, e.g. an acidic aqueous solution, is sprayed into the process gas stream in the same direction or in opposite directions, thereby treating the cleaning gas by vaporization or dispersion. Can be introduced into the gas.
When using carbon dioxide as a cleaning gas, it can be obtained from anaerobic digestion gas, which typically has carbon dioxide and methane, and the carbon dioxide can be extracted from the digestion gas and used as cleaning gas. I can do it. Furthermore, the combustibility of methane yields energy, water and carbon dioxide, which can also be used as a cleaning gas.

However, in terms of efficacy, cost and availability
It seems best to use HCl. The molar fraction of HCl gas with respect to air is approximately 7.5 × 10 ^-5 ~ 3.1
Use in the range of ×10 ^-2 . For contaminants similar to those mentioned above, HCl gas added at a molar fraction of approximately 3.1 × 10 ^-2 requires a cleaning cycle of approximately 30 to 40 ^minutes ; For mole fractions, it is necessary to spend about four times as long. The total amount of gas consumed in either case will be approximately 0.11 kg (0.25 lb) per diffuser element.
At a gas cost of about $0.50 per pound, the material cost to clean one diffuser element is about $0.125. It can be seen that this cost is advantageous when compared with the cost of re-firing the diffusion element. The cost to refire the devices is estimated to be as high as $7 per piece. Of course, the time and gas consumption mentioned above will vary depending on the nature of the contaminant.

However, if the above-mentioned diffusion element with an area of 369 cm ² (0.41 ft ² ) is used at a rate of about 6.75×10 ⁴ cm ³ /min to 8.1×10 ⁴ per element,
It is best to flush at a flow rate of 2.5 to 3 SCFM (cm ³ /min), which is approximately 1.62 x 10 ⁵ cm ³ /min to 2.16 x 10 ⁵ cm ³ per 900 cm ² (1 ft ² ) of effective discharge area. /min
(6 to 8 SCFM). Typically the molar fraction of HCl is greater than or equal to about 4 x 10 ^-5 , preferably about 8.6 x 10 ^-5
more preferably about 4×10 ^-4 or more, particularly about about 4×10 −4 or more;
Range of 5.7× ^10-5 to 3.1× ^10-2 and 6.6× ^10-3 to 3.1
A range of ×10 ⁻² is more suitable. All mole fractions mentioned above are applicable at atmospheric pressure. If the gas pressure at the bubble release point is different from atmospheric pressure, the value should be corrected by first multiplying by 760 and then dividing by the total gas pressure at the bubble release point in mm of mercury. .

Experimental Example Next, an experimental example of the present invention will be described (the present invention is not limited to this experimental example). This example experiment was carried out using the experimental setup diagrammatically shown in Figure 34, which provided an environment in which ceramic diffusion elements were contaminated by inorganic precipitation of calcium and ions at a rate higher than that normally occurring in the field. It is designed and operated to create. A small test device with a uniform thickness of approximately 6.45 cm ² (1 square inch)
A diffuser element having an effective outgassing area of an area of It was cut out from Sanitaire, a product of the diffusion element. Such elements were placed in the environment described above and operated under controlled conditions to observe the relative amount of increase in hydraulic pressure applied to the element and the relative results of various operating and cleaning techniques.

Milwaukee water taken from Lake Michigan is introduced into the apparatus shown in FIG. 34 using a bellows pump 521 at a flow rate of about 250 to 280 c.c./sec. The water is delivered via conduit 522 to a closed contacting chamber 523 to which gaseous CO ₂ is added at a flow rate of approximately 2.4 scc/sec. Cylinder 528 containing compressed CO ₂ as a CO ₂ source
Approximately 0.70Kg/cm ² in the upstream area of the tachometer 530 of appropriate dimensions by the regulator 529.
Adjust to output a pressure of (10Psi). The flow from tachometer 530 is regulated by regulating valve 531 and supplied to contact chamber 523 via conduit 532 . In this chamber, _CO2 gas is bubbled through the incoming water from the conduit. Both water and _CO2 are introduced near the bottom of the chamber and exit near the top of the chamber, which is covered with a cover to promote dissolution of the _CO2 into the water. The CO ₂ -dissolved water is then introduced from the feed line 537 into the bottom of the tube column containing limestone fragments, ie, the limestone column 538 , causing the limestone column to rise and flowing out near the top of the limestone column. This water is sent to the aeration tank 552 via a supply pipe 539.

Reagent tank 545 contains FeSO ₄ prepared by oxidizing FeCl ₃ with H ₂ SO ₄ . FeSO ₄ is taken out from the tank 545 by an extraction pipe 546 and a regulating pump 547, sent through a supply line 548 to the connection point with the supply pipe 539, mixed, and water containing 5 mg/Fe ⁺⁺ ions is sent to the aeration tank 552. to be introduced. This tank has a bottom wall 5
53, side walls 554, and an open top sized to hold a liquid bath 555 with an average retention time of about 2 hours. The liquid is introduced at one end of the liquid level of the tank, and is passed through the floor drain 5 from the weir 556 at the other end of the liquid level.
57 to be discharged.

The aeration test device 580 described above is installed in the aeration tank 552.
Place it at the bottom of the Each aeration device has a short cylindrical
PVC pipe 581, flat PVC top plate 583, bottom plate 5
A plenum formed by 82 is provided. Width approx.
A one inch long, one inch thick ceramic porous structure is attached to the top of each plenum 580. Each plenum is provided with air inlet and liquid outlet lines (not shown) and contains sufficient lead ballast and is secured to the tank bottom wall 553. The air source 560 for each ceramic specimen is an air compressor 562;
Air is taken in from the air filter 561 and discharged through the storage tank 563 to the pressure regulator 564, and the air pressure in the upstream region of the flow valve 565 is approximately
2.81~3.52Kg/ ^cm2 (40~50Psi). This valve delivers a controlled amount of air via conduit 566 to an air manifold 570, which is common to all test plenums. Branch line 57
Valve 574 regulates air flow from 1 to each test plenum.
individually controlled by Additionally, means (not shown) are provided for imparting a controlled level of moisture to the gas mixture introduced into the plenum. Valve control taps 590 are used on branch pipes 571 upstream of each plenum to monitor hydraulic pressure throughout the experimental course. This dynamic water pressure (DWP) is connected via a common conduit 596 to a tap 590 and a pressure gauge 597 filled with water.
Determined by. DWP is equal to the total differential pressure (ΔP) that is the pressure on the element minus the height of the liquid above each test device in test bath 555.

A valve control tap 603 is provided in the branch line 571 downstream of the pressure tap 590 and upstream of the plenum, through which the cleaning gas is introduced into the branch line 571 and mixed with the process gas, and the mixed gas is transferred to the plenum. and diffuses from the ceramic element. Cleaning gas source is compressed HCl
A cylinder 601 houses the CO ₂ gas, and the gas flow is controlled by a valve control tap 603 through a pressure regulator 602 and a tachometer (not shown), similar to the CO 2 gas.

Alternatively, an aqueous solution containing an activator, for example HCl, may be used and the cleaning gas produced by separating air or other gases from the aqueous solution. The cleaning gas is prepared in this way by carefully controlling the ratio of cleaning gas to process gas, thereby allowing an estimate of the effective limit of the cleaning gas in terms of the period of addition required to obtain an acceptable reduction in DWP. In the experiment diagrammatically shown in Fig. 34, an aqueous solution separation gas generation method was used, and the flow rate was adjusted to be relatively small compared to the flow rate of the processing gas supplied to the ceramic element, for example, 15 to 22 scc/sec. , the cleaning gas flow rate is on the order of a small fractional value of 3% of 1% of the process gas flow. The small amount of cleaning gas is released by bubbling the process gas (in this case air) stream into an aqueous cleaning gas solution of suitable concentration, for example an acidic solution of hydrogen chloride, the concentration of which changes over time. It changes very slowly, which allows a substantially constant molar ratio of cleaning gas to process gas to be maintained over a relatively long period of time.

Representative data obtained in the experimental program described above is shown in the graph of FIG.
It is a plot of the logarithm of DWP (inches of water column). Curve #1 is the initial stage before starting gas cleaning.
A control policy to increase DWP to about 3.5 times the DWP value is shown, and curve #2 shows a control policy to increase DWP by 1.5 times the initial value before cleaning.

Curve #1 The portion of the curve from points A to B shows the gradual deposition of contaminants on the surface of the test diffusive element and the gradual increase in DWP until a critical condition of 3.5 times the initial DWP is reached. . Approximately 1100 hours have passed at point B, and the state in which gas cleaning was performed using chlorine gas (Cl ₂ ) is shown by curve B-C.
A more detailed plot of curve B-C is shown in the graph of FIG. 36, which is shown on an enlarged time scale. Before adding chlorine gas to the process gas, carefully purge any liquid from the plenum by removing the plenum unit from the aeration tank and carefully tilting the unit to allow the process gas to flow through the purge line (not shown). ) to drain the liquid. After repositioning the unit in the aeration tank and prior to gas flushing, carefully observe the air flow rate through the unit's diffusion element and adjust as necessary before measuring DWP. This DWP is approximately equal to the pressure of 28 inches of water at time zero in FIG. 36, which corresponds to point B in FIG. At this time, approximately 9.25% of the chlorine gas is added to the processing gas stream.
The amount is introduced to give a molar ratio of ×10 ⁻³ . A cylinder of compressed chlorine gas (not shown) was used in place of the HCl cylinder 601 for this portion of the experiment. After approximately 540 minutes of continuous chlorine addition, the DWP decreased from an initial value of 28.0 inches of water column to approximately 12 inches at the time corresponding to point C in FIG.

Since point B is 20 inches higher in water column pressure than the initial DWP and point C is 4 inches higher than the initial DWP, the DWP reduction due to chlorine gas is 20-4/20 x 100 or 80% of the DWP increase. equal.

No cleaning gas is supplied to the unit between point C and point D. At point D, gas scrubbing with HCl begins, which reduces the DWP from about 14.4 inches of water column pressure at point D to about 8 inches of water column pressure at point E. HCl for process gas during this period
The molar ratio is approximately 6.5×10 ⁻³ compared to the Cl ₂ molar ratio of 9.2×10 ⁻³ between points BC. Therefore, as is clear from Figures 35 and 36, by using HCl, and from the DWP value obtained with chlorine gas alone, the DWP standard condition of the element, that is, 8.0 inches of water column pressure, can be improved.
Can be reduced to DWP.

Curve #1 in Figure 35 shows the situation for two additional contamination and cleaning cycles. Curves E-F and G
-H is similar to curve A-B; during these periods, the addition of process gas alone causes contaminants to accumulate on the device, resulting in an increase in DWP.

Curves F-G, H-I show two wash cycles similar to the cycle described between points D and E;
In this case, the cleaning gas was HCl, and the molar ratio of HCl to the processing gas was approximately 6.5×10 ⁻³ . These 2
The washing cycles are again shown in the graph of FIG. 36, which shows that not only in terms of chemical quantity required, but also in terms of degree of recovery.
It can be seen that it is much more effective than chlorine at a molar ratio of 9.2×10 ^-3 and takes less time to reach the equivalent condition for DWP.

The deposition cycle, shown by the time intervals between points A and B, between points E and F, and between points G and H, continues relatively regularly, and successive cleanings have the same effect, and this cleaning cycle can be It is important to show that there is no loss of performance even after multiple repetitions.

Curve #2 The cleaning policy for the sample shown in curve #2 is to clean the ceramic element when the DWP level reaches about 1.3 times the initial value of 8 inches of water column pressure.
Figure 35 is plotted over time, so curve #2
It can be seen that the unit shown by is started approximately 1900 hours after the start of the experiment itself. The general characteristics of curves #1 and #2 are similar. However, curve #2 shows five contamination and cleaning cycles, each cleaning cycle using HCl gas at a molar ratio of approximately 6.5 x 10 ^-3 to process gas, which is similar to cleaning cycle D in curve #1. -E, FG, and HI. FIG. 36 shows an enlarged view of the characteristics of the cleaning cycle of curve #2. In this case, it can be seen that all cleaning cycles have the same DWP that decreases over time, and each cycle completely recovers to the initial DWP value, similar to the HCl gas cleaning in curve #1.

Similar to curve #1, the relative duration of the contamination cycle for curve #2 varies slightly. However, there is no consistent tendency for the interval to decrease or increase from the baseline state to the limit DWP. Under conditions of in-situ deposition and/or organic contamination, one of the cleaning strategies shown by curves #1 and #2 is preferred over the other, and this depends on a number of factors, such as power cost, DWP rise, and based on aeration effect loss over time.

Term Definition Volumetric Compression Ratio The term "volume compression ratio" in this specification refers to two parts of an element formed from solid particles that have been shaped, pressed into a porous compressed shape by bonding or sintering, and a bonding force is generated. Use as a basis for comparing one or more areas. When applied to a certain area,
This ratio is the quotient of the height of the material before pressing divided by the height of the material in this area after pressing. Of course, pressing causes material to move laterally from one area to another, which will have some effect on the observed compression ratio, but in order to address the issue of ``significant'' compression ratios, we Ignore movement. If the height of the material before or during pressing at different locations in an area is different, the average height measured with respect to the plane of the area in the plan view is used. Therefore, if a further height of material is added on top of material that has already been compacted by partial pressing or vibration, the height of the added material is therefore also taken into account. More specifically, in determining the quotient, the divisor is the fully compressed height of the entire material, and the dividend is the uncompacted height of both the initial material and the additional material.

Reference Conditions The term "reference conditions" is used to refer to the hydrodynamic pressure or average bubble release pressure exhibited by the diffusion element at a selected point in the operating history of the porous diffusion element. For example, any of the conditions shown below, or the pressure of the element in the state that finally occurred in the operation history of the element under any of the following conditions, can be used as the reference condition. (a) in the initial state of the treatment operation of the liquid medium containing at least one contaminant; (b) in the final state cleaned by a cleaning gas; and (c) by means other than cleaning gas. (d) a condition that ultimately maintains contact with the liquid medium without releasing gas; (e) the lowest previously recorded pressure.

In a preferred embodiment of the invention, the reference condition for hydraulic pressure or average bubble release pressure is the pressure exhibited by the device at the time of manufacture or when first incorporated into a treatment operation for a liquid medium containing at least one contaminant. . This reference condition can be the state of the device after initial and/or sequential gas cleaning.
According to a preferred embodiment of the invention, therefore, the hydrodynamic pressure or mean bubble release is significantly reduced in the first and at least one sequential gas scrubbing, based on the reference conditions of the diffusion element at the time of manufacture or first use. Calculate. Preferably, a plurality of distinct successive gas scrubbing operations are carried out until a significant reduction in the increased pressure is shown relative to the reference conditions of the diffusion element as manufactured or originally used.

In an initial or sequential gas cleaning, in particular during the first gas cleaning, the hydrodynamic pressure or average bubble release pressure of the element at the time of manufacture or after the last use and the correspondence of these variables when starting the gas cleaning according to the invention. Make this amount of decrease larger than the difference between the value of .

Boundary Region The term "boundary region" refers to a position inwardly adjacent to a peripheral region, if any, between the peripheral region and the outer region, preferably the outer edge of the outer region. The position should be adjacent to . This region is a region in which the volumetric compression ratio of the element gradually increases (continuously or stepwise) in the direction of the peripheral region or towards the vertical surface near the periphery of the element;
The above-mentioned vertical surface refers to a surface inside the peripheral region, at or adjacent to the peripheral region.

Bubble Release Pressure "Bubble Release Pressure" is used to refer to the resistance to the release of gas from a point or area on a diffusion element under a liquid medium, such as water. When applied to a point on an element, it refers to the quasi-static pressure that must be applied to release bubbles from this point on the gas ejection surface. When applied to a region of the active gas release region of the diffusion element, the bubble release pressure is the average of the bubble release pressures measured at a number of randomly or evenly selected points distributed over this region. Bubble release pressure is expressed as the height of the water column pressure (in inches) after subtracting the hydrostatic pressure. Testing is performed using the apparatus described with respect to FIG. 20 herein, or using other apparatus capable of producing data similar to or convertible to an indication of bubble release pressure. The value of the bubble release pressure mentioned above is determined based on "quasi-static pressure" by adjusting the test equipment so that the bubble release pressure observed is approximately equal to that obtained under static pressure conditions by releasing the bubbles slowly enough. do.

Center The term "center" refers to the position of the center of gravity or the center of the figure of the effective gas emitting surface of the element itself when viewed in plan, whether the element is regular or irregular.

Central Region The term "central region" according to the present invention refers to the volume below the central region that constitutes a fixed proportion of the total effective outgassing area of the element, the boundaries of which are defined according to the invention on the surface of the element. It may or may not coincide with the position of the central recess. The "central region" can be applied even if the outline of the diffusing element as seen in a plan view changes, and the outline of the element may be circular, elliptical, square, rectangular, polygonal, irregular, etc. It is equal to the contour of the effective gas emitting surface of the element, and the center of the effective gas emitting surface is the common center. The central area delimiting the central region is approximately 80% of the total effective gas release area, preferably approximately
Typically it is 60%, more preferably about 40%.

Cleaning "Cleaning" means the process of preventing, retarding, or removing the deposition of contaminants on a porous diffusion element by means of a cleaning gas, which process does not affect the potential or actual permeability of the porous diffusion element. This permeation effect is adversely affected by the presence of contaminants in the gas release passageway. By removing the deposits, the increase in hydraulic pressure and/or bubble release pressure above baseline conditions is significantly reduced.

Cleaning Gas In this specification, the cleaning gas refers to cleaning gas that is introduced into the gas discharge passage of the porous diffusion element alone or in a mixture with other gases including a processing gas at a predetermined concentration and amount. means a gas that has sufficient destructive properties against contaminated deposits. Such gases can act in various states. For example, by dissolving the contaminant, especially in the case of deposits of precipitated inorganic salts, or by dissolving the substances that cause the contaminant to adhere to the diffusion element, breaking the bond between the contaminant and the element. can act by killing living organisms and separating them from the diffusing element, especially in the case of biological contaminants;
It is also possible to act in a combination of these operating states. Thus, for example, the cleaning gas may contain one or more gaseous organic and/or inorganic dissolved components or components that can be present as a liquid and the temperature 20
C; Can be a mixture of dissolved components containing components that can exist as gases at standard atmospheric pressure. For example, it can be H ₂ O ₂ , CH ₃ OH, and other volatile organic solvents. However, suitable cleaning gases are those which exist as a gas at 20° C. and which exhibit an acidic reaction when dissolved in water, such as SO ₂ , SO ₃ , CO 2 , Cl ₂ , ClO _{2 ,} HCl, NO _x ,
O ₃ , Br ₂ and the like are preferred, and HCl is particularly preferred.

Coefficient of variation "Coefficient of variation" means the quotient of the "standard deviation" divided by the "average.""Standarddeviation" refers to the root mean square of the difference from the average of a given number of bubble release pressure measurements. "Average" means the arithmetic mean of the bubble release measurements described above. Optimal accuracy is obtained by measuring the bubble release pressure at random points representing nearly the entire gas emitting surface of the element, or along two mutually orthogonal diameters if the element is circular. It has been found that sufficient accuracy of information can be obtained by sampling the bubble release pressure at at least five points equally spaced from each other.

Hydrostatic Head Expressed in height (in inches) of water column pressure, means the hydrostatic head of any liquid medium that is applied to the outflow surface of the diffusion element during gas scrubbing (although it increases at any given time). , regardless of whether it maintains an approximately constant value or decreases) is smaller than the operating head that cleans the equipment in advance.

Hydrodynamic pressure means the pressure difference between the inlet surface of the diffusion element at the point of bubble formation and the hydrostatic head. It is a measure of the resistance to glass flow of a summing element, including the effects of friction at the gas discharge passages of the element and the inlet and outlet ends of such passages, and the effects of surface tension at the outlet ends of the passages. One convenient way to measure hydrodynamic pressure is to calculate the difference between the hydrostatic head of the liquid medium at the outflow surface of the diffusion element and the total gas pressure at the inflow surface of the element, expressed in inches of water column pressure. It's about measuring.

Differential pressure means the difference in hydraulic pressure maintained during gas cleaning,
This differential pressure is greater than the differential that would exist if the only change in equipment and operating conditions was the sequential removal of contaminants from the cleaning gas.

increased level means the difference in hydraulic pressure that occurs during cleaning under changed operating conditions, i.e. with increased pressure differential;
Hydraulic pressure in this case means that which occurs when changes in equipment and operating conditions result in the sequential removal of contaminant deposits by the cleaning gas.

Equilibrium Concentration "Equilibrium concentration" is used to describe the activity of the cleaning gas and process gas mixture. The equilibrium concentration is determined by bubbling the gas mixture through the liquid medium at the temperature at which the wash is introduced. Concentrations are determined by any suitable analytical technique upon saturation of the liquid medium with process and cleaning gases and are expressed as a fraction of the weight of the cleaning component relative to the total weight. When the cleaning agent is acidic, the negative logarithm of the hydrogen ion concentration is measured using a PH meter, and this value is expressed as the equilibrium PH value of the mixed gas.

Contaminants "Contaminants" are those present in the liquid medium and/or process gas and deposited at the inlet and/or outlet of the gas release passages of a porous diffusion element, or within such passages, e.g. Refers to a substance that affects the gas pressure/flow relationship by blocking flow through the elements or disrupting the uniform distribution of process gas.

Contaminants and/or deposits are natural and/or
or synthetic organic matter, organic and/or inorganic;
It may be a mixture of living or non-living and liquid, solid and/or gaseous components. Common contaminants include mushrooms and bacterial species;
Algae, protozoa, rotifers, higher life forms, oil scum, organic matter covering pipes, soap, detergent scum, dust, inorganic salts, rust and metal oxides, hydroxides,
Carbonates and sulfates, ions such as calcium, magnesium, copper, aluminum, etc., are suspended or dissolved in a liquid medium and the process gas is released into the liquid medium at the interface with a porous diffusion element. There are other substances that are also difficult to dissolve.

The term "present" is used in a broad definition to include, for example, contaminants present in any mixture in suspended, dispersed, emulsified, dissolved, and other forms.

A "deposit" generally refers to something that sticks to the diffuser element such that under normal discharge conditions the process gas is not sufficiently removed from the diffuser element to provide the gas permeation effect described above.

Furthermore, the term "deposit" is used in a broader sense to include pasty solid and/or liquid components, semi-solid or solid particles or lumps, such as sludge, scale and other encrustations.

Deposit formation occurs in various forms. For example, rust particles generated by the process gas enter the inlet of the gas discharge passage of the diffusion element and remain there, resulting in mere stagnation; oil droplets and dust particles generated by the process gas stick to each other, and the inflow of the element. increase when it adheres to a surface and gradually grows into a mass that blocks part or all of the inlet of the gas release passage;
Occurs when one or more living organisms living in the liquid medium at the outflow surface of the diffusion element form a layer or network on this surface, blocking the flow of the process gas or disturbing the uniform distribution of the process gas. Suction and treatment when suspended solids in the liquid medium flow into the gas discharge passage due to the growth of the airframe, backflow of the liquid medium into the diffusion element that occurs when the flow of process gas is intentionally or inadvertently stopped. It is formed by precipitates (including crystals) when insoluble inorganic salts are deposited in the gas discharge passage and/or outlet during gas discharge.

Gas As used herein, gas may be a true gas or vapor or a mixture of both, and also includes suspended liquids or solids in the form of fine or colloidal droplets, particulates, or means a gaseous substance or gaseous mixture that is sufficiently gaseous to form gas bubbles when discharged from a porous diffusion element into a liquid medium under the conditions of use; means.

Liquid Medium or Medium “Liquid medium” means a substance (including a single substance or a mixture of substances) that is sufficiently liquid to form gas bubbles when gas is being emitted through a porous diffusion element. means. The liquid phase substance may include, for example, one or more organic liquids, or inorganic liquids, or mixtures of organic and/or inorganic liquids (including miscible and immiscible liquids), and may further emit process gases. It also includes other liquids, gases and solid substances which do not take away the liquid phase of the above-mentioned medium under conditions of. Further, at least one component of the media components, which is a component of the one or more contaminants and/or other components of the media, undergoes a predetermined change in response to the process gas release. . A preferred category of such media is liquid wastewater, e.g. mixed liquids treated with activated sludge processes,
These include refining and brewing wastewater, paper manufacturing wastewater, etc.

Average Bubble Release Pressure means the arithmetic mean of a statistically sufficient number of bubble release pressure measurements at randomly or systematically selected locations on the surface of a diffusion element.

Porous Diffusing Element Large area, e.g. usually at least about 129.0
cm ² (20 square inches), preferably at least about 193.5
cm ² (30 square inches), more preferably at least about
Means an element having an effective gas ejection area of 258.0 cm ² (40 square inches) and having a large number of fine holes closely spaced from each other and arranged either randomly or regularly across the effective gas ejection area. However, it should be understood that only a portion of the number of holes will be permeable to gas under certain operating conditions. On the other hand, it is used in clean water when new or manufactured and has a large number of effective holes per unit area of effective gas release surface under designed operating conditions.

Such elements may have certain optionally added characteristics as required. For example, holes with gas release passages are provided. Although these passages are generally straight, they are actually curved. Although separate passageways are desirable, it is common for a significant number of passageways to be interconnected. Irrespective of the degree of straightness, curvature, or mutual communication, the inlet of the gas discharge passage on the gas inlet face and the outlet of the gas outlet face of the element are separated from each other. The close spacing of the passages in the preferred element is indicated by the average lateral spacing between the holes being less than the average thickness of the element and therefore less than the average length of the gas release passages. This spacing refers to the spacing between all holes in the diffusing element, as well as what is believed to be effective over a range of operating conditions.

Pore size is approximately 60-600 microns, preferably approximately 90
~400 microns, more preferably in the range of about 120-300 microns, this dimension calculated by substituting the average bubble release pressure of the device into the equation D=30γ/p given in ASTME-128. be done. where D = maximum pore diameter, γ = surface tension of test liquid (dyn/cm), and p = pressure (mm of mercury)
shall be.

The shape of the element in plan and longitudinal section may be any shape desired, for example, when viewed in longitudinal section, the ratio of the horizontal portion between the maximum horizontal dimension of the element and the average thickness of the element is at least about 4:1, preferably at least about 6:1, more preferably at least about 8:1.

Additionally, the horizontal portion has an effective gas release surface to average thickness ratio of at least about 10 square inches (64.5 cm ² ) per inch (2.54 cm) of thickness, preferably at least about 20 square inches (129.0 cm ^{2 )} . ), more preferably at least about 40 square inches (258.0 cm ² ).

Further, below the effective gas discharge surface, a horizontal portion is provided with a region where the volume compression ratio is increased. The horizontal part therefore has different regions, namely a central region, an outer region,
It has a border region and a peripheral region, which may or may not be of a visually distinguishable nature; can do. For example, it is preferred that the volume compression ratio of the central region is at least about 2% higher than the volume compression ratio of the outer regions, preferably about 2 to 20%, more preferably 3 to 15%. If a boundary region is provided, the volume compression ratio of the boundary region is at least about 10% relative to the ratio of the outer region, preferably about 10 to 35%, more preferably about 35%.
~100% higher.

The diffusive element can be a variety of organic and inorganic particulate materials, but when it is a soft particle, it has a compressibility of at least about 0.2 x 10 ⁵ psi (0.14 x 10 ⁴ Kg/
cm ² ), more preferably about 0.2×10 ⁵ to 4×10 ⁵ psi (0.14
×10 ⁴ to 0.28 × 10 ⁵ Kg/cm ² ), preferably about 4 × 10 ⁵ to 6 × in the case of hard inorganic materials.
10 ⁶ psi (0.28×10 ⁵ to 0.42×10 ⁶ Kg/cm ² ).

Outer Region The "outer region" refers to all or most of the diffusing element below the total effective gas ejection surface other than the "center region." Compared to the central region, the outer region is located further outward from the center of the element than the central region. In addition to the central region, the element may simply have an outer region, or may have other regions.

Oxygen-containing gas "Oxygen-containing gas" refers to a gas that contains pure oxygen and an appropriate amount of oxygen and can be used as a processing gas.

Peripheral Area "Peripheral Area" refers to the volume along the outermost edge of the effective gas emitting surface of the diffusing element. The peripheral area is
Whether annular or non-annular, the press (including in combination with pressing by other techniques) will result in less permeability (including non-permeability), greater density, and higher density than all or part of the outer region. This refers to the area that is treated as a region with low intensity. A device with a peripheral region may or may not have a border region.

Pre-clean Working Head Expressed in inches of water column pressure, refers to the total amount of hydrostatic head of liquid medium that is applied to the outflow surface of a diffusion element in an apparatus during the period prior to commencing cleaning. For example, it is the time average of the water head during the operating period of 90 days immediately before washing, or preferably the final water head before washing in normal operation, and more preferably the larger of the average water head and the final water head.

SCFM SCFM means gas flow rate in cubic feet per minute corrected for a temperature of 20°C, an absolute pressure of 760 mm of mercury, and a relative humidity of 36%.

Specific Permeability The term "specific permeability" refers to the total amount of gas passing through the diffuser element in the dry state, and is defined as 2 inches of water (50.8
At a driving pressure of 1 inch (25.4 mm)
It is expressed in standard cubic feet per minute (2.7 x 10 ⁴ cm ³ ) per square foot (900 cm ² ) area of an element of %). Specific permeability is calculated from the equation G=Q(t/A), where G is the flow rate (in standard cubic feet per minute), t is the thickness of the element (in inches), and A is the thickness of the element perpendicular to the direction of flow. The average effective gas release area (ft ² ) passing through. The average thickness is used when the gas emitting surface of the diffuser element is on a portion of the element that varies in thickness.

Back Pressure means a measurement of the resistive pressure of flow through an entire gas distribution network or a portion of a gas distribution network when passing a given amount of gas through a diffusion element.
This resistance includes frictional drag and surface tension associated with conduits, diffusion elements and other elements of the network, contaminants, and hydrostatic heads. The network and network portions include a plurality of pneumatically interconnected diffusion elements. These elements share a process gas source and experience a combined resistance to flow along with the conduits and other components of the network;
This combined resistance must be overcome by the pressure of the gas source. In activated sludge treatment equipment, the design back pressure is measured at the outlet of the compressor or blower and is approximately 3~
20psi (0.21~1.41Kg/ ^cm2 ), typically about 4~
15psi (0.28~1.05Kg/ ^cm2 ), typically about 6~10psi
(0.42 to 0.70 Kg/cm ² ) is known.

Tank Processing Tank processing, for aeration or other purposes, means converting the process gas into a liquid medium at least about 2 SCFT, preferably at least about 4 SCFM, more preferably at least about 6 SCFM per 1000 ft ³ of liquid medium.
discharge at a flow rate that is significantly greater than the flow rate applied to the sewage treatment lagoon or pond in which the tubular defuser is installed. Alternatively, the average retention time of the liquid medium is approximately 48 hours or less, typically 24 hours or less.
hours or less, more generally 12 hours or less, which is less than the lagoon or pond retention time described above.

Processing Gas By processing gas is meant a gas which is capable of producing the required changes in at least one constituent of the liquid medium, but which is not as destructive to contaminant deposits as a cleaning gas.

Vertical The term "vertical" applies to the surface of the diffusing element and is intended to include truly vertical, nearly vertical, such as at an angle of about 20° to the vertical.

[Brief explanation of drawings]

Figure 1 is a partial line diagram of the sewage aeration system, Figure 2 is a perspective view showing the terminal pipe and differential user of the equipment in Figure 1, Figure 3 is a vertical sectional view taken along line 3-3 in Figure 2, and Figure 4 The figure is a vertical sectional view orthogonal to FIG. 3, FIG. 5 is an enlarged vertical sectional view showing details of the flow rate adjustment device, and
Figure D is a vertical sectional view of a modified example of the flow rate adjustment device shown in Figure 5, Figure 6 is a plan view of the plenum in Figure 4, and Figure 7
The figure is an enlarged vertical sectional view of a part of the periphery of an embodiment of the diffusion element, FIGS. 8 to 14 are partial enlarged longitudinal sectional views similar to FIG. 7 of various other embodiments of the diffusion element, and FIG. FIG. 2 is a vertical cross-sectional view of the configuration of the terminal tube and differential user, FIGS. Figure 18-
19 is a longitudinal sectional view along line 18, FIG. 19 is a partial cross-sectional view showing a method for measuring pressure and flow data used in the practice of the present invention, and FIG. 20A is an enlarged cross-sectional view of the probe of the device in FIG. 20, and FIG. 20B is a diagram showing the bubble release pressure of a part of the device in FIG. 20. Explanatory diagram showing an enlarged view, No. 21-
29 is a diagrammatic explanatory diagram showing a method of forming a diffusion element according to the present invention, FIG. 28A is a plan view of the diffusion element of FIG. 28, and FIG. 30 is a longitudinal cross-sectional view of the diffusion element according to FIG. An explanatory diagram using a graph showing the bubble release pressure of each part of the element, FIG. 31 is an explanatory diagram similar to FIG. 30 of the diffusion element according to FIG.
Figures 2A and 32B are graphs of pressure/flow characteristics of diffusion elements to illustrate a preferred embodiment in which each diffusion element is provided with individual flow rate adjustment means; Figure 33 is a preferred implementation of a tank-type sewage aeration system according to the present invention; An example diagram, FIG. 34 is a diagram of a porous diffusion element testing device, FIG. 35 is a graph showing the operating state of the tank-type sewage aeration device according to the present invention, and FIG. 36 is a part of FIG. 35. FIG. 2 is an enlarged explanatory diagram. 1... Aeration tank, 5... Compressor, 8...
...Main pipe, 9...Lower pipe, 10...Distribution pipe, 11...
...Terminal pipe, 12,175...Diffusion device or differential user, 14,182...Plenum, 16...Top surface of terminal pipe, 19...Storage tank, 24...Flow rate adjustment device or regulator, 26...Side wall means, 3
5... Diffusion element, 70... Circular flat central region, 8
0...O ring, 84,129,135,156
... Clamp ring, 92 ... Clip, 108
... Retaining ring, 116 ... Split ring clamp, 95, 125, 133 ... Closing means, 10
7,128,147,154... non-permeable coating,
149...Sealing ring, 229...Peripheral area, 2
30... Cylindrical vertical edge, 231... Horizontal annular surface, 232... Vertical side surface, 233... Gas discharge surface, 234... Gas inflow surface, 240... Tank,
255...T-tube, 259...Blocking ring or stopper, 260...Bubble, 271,272...
Reference line, 273... Reference mark, 276...
Bubble release pressure curve, 277...Flow rate curve, 301
... Dice, 302 ... Cavity, 310,4
07...Particle body, 312...Screed, 317
...Ram, 318...Ram compression surface, 400...
Shaping ring, 413... central region, 414... outer region, 421... circular insert, 430...
Air inflow surface, 431... Air discharge surface, 432...
Center recess, 440... Annular insert, 461...
... Annular band, 466 ... Annular rib, 470 ... Tank, 480 ... Processing gas equipment, 481 ... In-house piping, 483, 485 ... Lower pipe, 484 ... Joint, 486 ... Sliding flange, 487 ...Terminal pipe, 489...Distribution pipe, 490...Diffusion device, 5
00... Gas cleaning device, 501... Scale, 50
2... Indicator, 503... Cylinder, 50
8...Plastic pipe, 521...Pump, 52
3...Contact chamber, 537...Limestone column, 545...
Reagent tank, 552... Aeration tank, 580...
Aeration test device, 570...manifold, 590,
603...Valve control tap.

Claims (1)

[Scope of Claims] 1. A method of treating a liquid medium by passing a treatment gas through a porous diffusion element immersed in the liquid medium, the method comprising: a porous diffusion element immersed in the liquid medium; A cleaning gas, alone or mixed with the process gas, is applied to the element to tend to deposit and gradually increase the hydrodynamic pressure and/or average bubble release pressure of the element with respect to the initial reference conditions of the element. In the liquid medium treatment method of cleaning the element in a predetermined position by passing the element through the liquid medium, the hydrodynamic pressure level of the element exceeds a reference condition and the effective gas emitting surface of the element exceeds 9×10 ² cm ² (1 ft ² ). ^{( 2} SCFM) flow rate to limit potential or actual increases in pressure above approximately 635 mm (25 inches) of water column and/or the average bubble release pressure level of said element. Introduce cleaning gas at sufficient frequency and in sufficient quantity, including continuous supply and multiple flow adjustments, to limit any potential or actual increase in water column by more than approximately 635 mm (25 inches) above reference conditions. one or more of the groups of at least about 10 diffusion elements by supplying said cleaning gas to an immersed portion of a gas distribution network having means, a plurality of plenums, and a plurality of diffusion elements. simultaneously supplying a cleaning gas to each of the plenums, wherein said flow rate regulating means is connected to said plenum to supply said gas to said plenum, and said flow regulating means is dimensioned such that substantially the same amount of said gas is supplied to each of said plenums. to the dimensions to be supplied,
or adjusting and connecting each of said plenums directly or indirectly to one or more of said diffusing elements, whereby said diffusing element connected to one of said plenums to another of said plenums; the process gas alone or during an operating cycle consisting of a total number of days of at least about 30 days in which the process gas is passed continuously or intermittently through said element; discharging from said element in admixture with a cleaning gas, such that the cleaning gas is supplied with sufficient frequency and in sufficient quantities to reduce the hydrodynamic pressure and/or the average bubble release pressure to or below said level. A method of treating a liquid medium, characterized in that contamination is limited during the operating cycle by maintaining 2. A treatment method for treating a liquid medium by passing a treatment gas through a porous diffusion element immersed in the liquid medium, wherein contaminants in the medium or treatment gas are deposited on the element or the surface of the element, and the The element is intermittently provided with a cleaning gas alone or mixed with the process gas to tend to gradually increase the hydrodynamic pressure and/or mean bubble release pressure of the element relative to the initial reference conditions of the element. In a liquid medium treatment method in which the element is cleaned in place by passing through the element, the hydrodynamic pressure level of the element exceeds a reference condition to 5.4 per 9 x 10 ² cm ² (1 ft ² ) of the effective gas emitting surface of the element. × 10 ⁴ cm ³ /min. (2 SCFM) when the pressure increases by an amount equal to approximately 25 inches of water, or when the average bubble release pressure level of said element exceeds the reference condition and increases to approximately 635 mm of water. (25 inches)
commencing scrubbing with the scrubbing gas when the pressure increases by an amount equal to the pressure of supplying a cleaning gas to one or more elements of a group of at least about 10 diffusion elements simultaneously, wherein the flow regulating means is connected to the plenum to direct the gas into the plenum; and the flow rate regulating means is sized to supply approximately the same amount of the gas to each of the plenums;
or adjusting and connecting each of said plenums directly or indirectly to one or more of said diffusing elements, whereby said diffusing element connected to one of said plenums to another of said plenums; and reduce said hydraulic pressure to an extent of at least about 0.3 times said increase in said hydraulic pressure, or at least about said increase in said mean bubble release pressure.
A method for treating a liquid medium, comprising supplying the cleaning gas during one or more of the supply unit periods to reduce the average bubble release pressure by a factor of 0.5. 3. A gas distribution network arranged in a tank; introduction means for introducing a process gas into this network and intermittently introducing a cleaning gas either alone or mixed with said process gas; and an immersed part of said network. a plurality of flow rate adjustment means distributed in the plenums, the flow rate adjustment means receiving the gas and discharging the gas at a predetermined flow rate to a plurality of plenums downstream of the flow rate adjustment means; a plurality of porous diffusion elements in communication with each other to receive said gas, each element comprising a number of closely spaced micropores defining a passageway for discharging said gas; a diffusion element in which the hydrodynamic pressure is increased above the reference condition by depositing on the plenum, and each element is connected through a separate plenum to separate flow rate adjustment means in the upstream areas of these plenums. A liquid medium processing device characterized by: 4. The diffusion element is arranged so that the supply of cleaning gas can be started at a sufficient frequency to maintain the hydraulic pressure applied to the diffusion element within a range not exceeding the pressure of about 635 mm (25 inches) of water column above the reference condition. 4. A liquid medium processing apparatus according to claim 3, characterized in that the gas distribution network is provided with measuring means for measuring with sufficient accuracy the pressure and flow rate of the gas passing through at least one of the gases.