DE4016915A1 - METHOD AND DEVICE FOR MECHANICALLY SEPARATING SOLIDS FROM A FLUID - Google Patents

Description

The invention relates to a method for mechanical Separation of solids from a fluid, in particular for the purification of waste water, especially of municipal or from industrial wastewater, the solids containing fluid one by a drive in rotation offset, roller-shaped rotary screen, with one part a peripheral wall of its peripheral surface Inlet basin forms, is supplied from the outside, the Solids adhere to the surface of the rotary screen and be lifted off the rotary screen and taken away while the cleaned fluid through the openings of the rotary screen in whose interior reaches and is mechanically cleaned is subtracted. The invention also relates to a Device for performing such a method.

Such a method and devices for Implementation of such processes are state of the art known. Such processes result in considerable Problems when the amount of fluid flowing in the hereinafter referred to as wastewater, as well as how Amount and composition of the wastewater Fabrics within a short period of time like seconds, Minutes or even considerably in the course of a day changes, like this for example at municipal or also industrial wastewater to a large extent.

It has been shown that in known methods  Quality of the cleaning effect fluctuates widely and frequently is deficient, with the rotary screen also frequently disturbed Disconnect function and can also clog. How to has shown is one of the common malfunctions due to the fact that on the lateral surface of the Rotary screen gradually a roller-shaped mud roll trains who are separated from the already Sieve layer feeds and rolls back again and again and can grow so much that the machine is switched off must become. Another common disorder is "Spillover" of the sieve, d. H. of overshooting the Inlet over the upper edge of the screen z. B. with sudden Increase in the amount of water or in the event of an extreme increase in Pollution.

The object of the invention is the method to improve the type mentioned in such a way that a trouble-free mechanical cleaning of a fluid regardless of large fluctuations in quantity and composition of the fluid containing solids guaranteed and a significant increase in separation of fine particles is made possible.

To solve this problem, the method is according to Invention characterized in that the water level in the Inlet basin by changing the speed of rotation of the Rotary screen between a maximum and a minimum is regulated, the minimum of the water level so high is set that the adhesive effect of the solids the jacket of the rotary screen is sufficient to remove the solids take the coat with you, without there being any on the coat constantly rolling back sludge roll forms and that Maximum is set to such a value that no Spillover takes place.  

According to the features of the invention Speed of rotation of the rotary screen used, the To optimally regulate the fill level in the inlet basin, and it on the other hand, such a fill level in the inflow basin ensures that sludge roll formation is prevented becomes. This can e.g. B. can be achieved if the Level no more than 20% of the radius of the Rotary sieve below the top vertex of the roller shell sinks. However, the conditions depend on various factors, so that the indication only as Example to be evaluated.

With this automatic scheme, not only can reliably prevent sludge roll formation, rather, the possibility is created of a build up even filter auxiliary layer. Because such Auxiliary filter layer is built up automatically, are all Operating conditions included. With strong fluctuations in The control system can automatically supply the take into account different amounts of wastewater. It also eliminates the need for an additional Bypass circuit to provide, as in known methods or devices is required to overflow to prevent using the rotary screen. In the invention There can also be no overflow, because by increasing the speed an increased amount of Dirty water or dirt automatically taken into account can be. Therefore, for example, no one is needed Clarifier attendants for the operation of the plant to be constantly against.

Another very great advantage of the invention The process can be seen in the fact that for everyone in practice Operation occurring cases the maximum level so can be chosen that always an optimal use the maximum possible screen area is guaranteed. The  is called the sieve area until shortly before the overflow point be covered, d. H. 80% -95% of the area before Overflow point can be used as an effective screen area all the time be exploited. This enables a constant Cleaning quality regardless of the amount of wastewater or Accumulation of dirt.

Another advantage of the invention is that the automatic control a rotary screen of a certain Size for a large number of different If necessary, can be used.

In such prior art methods, it is on the other hand required, for example with several smaller and more expensive rotary screens side by side work when the amount of water or cleaning capacity should be increased such. B. when expanding a Industrial plant, with an adjustable sieve essential is cheaper.

In the method according to the invention, this can be done simply by Increase the speed of the rotary screen taken into account will.

In an advantageous embodiment of the invention the water level continuously between a maximum and regulated a minimum, when reaching the maximum driving the rotary screen to a larger one Speed and when descending until reaching the Minimums to reduce the turning speed is regulated. With these measures, one area optimal screening or filtering, and at the same time the sludge roll formation is reliable is prevented, the regulation then as Two-point control (maximum / minimum) is designed. At  increasing quantity and / or pollution increases Water level in the inlet area up to the specified one Maximum, which is designed so that the waste water is still cannot run over the sieve. By an increase the rotating speed of the rotary screen comes more free Screen area per unit of time is used, whereby the Flow rate per unit of time is increased or more Dirt is removed through the sieve. The Water level in the inflow basin decreases after the Shock load again so that the speed is reduced, to maintain the maximum possible screen area. The extreme case of a critical lower value at which the roller-shaped formation of the accumulated dirt and Mud begins, the roller over and over again would roll back and the dirt would not come out of the Inlet basin would not even be reached. By arranging the minimum accordingly high Water level is namely the circulation speed of the Rotary sieve reduced so early that the water level in the Inlet basin never in the critical lower area Value can decrease.

If the regulation takes the form of a one-point regulation in Area of the maximum is formed, so is already at a slight drop in the water level below the maximum by reducing the speed correspondingly as the optimal Water level found water level adjusted to to achieve a maximum impact of the trapping layer. The Regulation happens in an advantageous manner for training the trapping layer so that the minimum of Circumferential speed of the rotary screen is designed so that the finest on the surface of the rotary screen Trapping layer retaining dirt particles if possible forms large areas and being the maximum of Peripheral speed of the rotary screen is designed so  that the catch layer even at this peripheral speed does not tear off, but never the sieve spills over. This trapping layer, which is mostly sand withholds, is formed by the fact that the separated larger parts and particles as a filter for the smaller dirt particles act, so that with the help of Grain size can also be eliminated, which are smaller than the openings of the rotary screen. At there are many of these small particles Waste water - usually for all municipal waste water - especially about sand. This is through the method according to the invention to such a high degree secluded that there is usually even a sand trap, as he does in such plants with such procedures So far it has been common practice to dispense with what significant investment and a big one Maintenance work can be omitted. The scheme can of course be steamed, so not current riots in the inflow basin - such as B. that Switching on a pump - lead to unnecessary regulation.

To solve the problem is one Device according to the invention for performing the Method characterized in that the device comprises a control device which for controlling the Water level to a certain value or to a certain range of values at least one Has water level sensor in operative connection with the Drive the rotary screen in the sense of a reduction or Increase the speed of the rotary screen.

The so equipped with a control device Device has the great advantage that it is for systems different sizes can be used because the Speed of the drive of the rotary screen within wide limits  is variable. Despite different throughputs or also strong fluctuations in the supplied dirt an optimal cleaning effect is always achieved because the fill level in the inlet tank to an optimal value can be adjusted.

The control device can be a single-point control or be designed as a two-point control. At a Training as a single point control can act as a sensor pressure sensitive membrane sensor in the range of Inlet basin arranged from the Membrane deflection to draw a conclusion on the water level pull allowed. With this membrane sensor, the Motor of the rotary screen can be controlled.

A light and in is preferred as the drive of the rotary screen hydraulic motor or a wide range frequency controlled electric motor used. Such a Motor can and is practically trouble-free especially the special conditions in the wet area customized. It is also particularly suitable for use in the inlet area to be protected against gas explosion Sewage treatment plant. Of course, you can also use a correspondingly higher one Encapsulation effort electrical or other Drive motors are used. In another an advantageous embodiment of the invention provides that above the maximum water level one on the Circumferential surface and the solid layer adhering there pressurized roller is arranged. These Pinch roller evens out the solid layer or Trapping layer and squeezes the water content out of the Trapping layer. If it is sealed on the side, permitted they also cause a higher water level in the inflow pool leads to a larger usable area of the sieve.  

The pressing can also be carried out with a roller Tape.

The invention is based on the in the Drawing shown embodiment further explained and described.

Fig. 1 is a schematic representation of a side view of a device according to the invention,

Fig. 2 shows a variant in which a press belt is used instead of a pressure roller.

The device generally has a rotary screen 1 which rotates about an approximately horizontal axis A, the outer surface of which is provided with openings which have, for example, a gap distance of approximately 1 mm. With regard to the slot shape, a self-cleaning slot sieve with wedge-shaped inwardly widening sieve holes is preferably used as the sieve, as is known per se in the prior art.

The roller-shaped rotary screen 1 is rotated in the direction of arrow P by means of the motor M.

As the figure shows, the rotary screen 1 forms with part of its circumferential surface a lateral boundary wall of the inlet basin 2, which is fed with dirty water containing fine and coarse dirt particles through an inlet 3 . In the region of the side wall 4 of the inlet basin, a sensor 5 is arranged, which can be designed, for example, as a membrane sensor and determines the pressure of the water column formed by the waste water in the inlet basin 2 . The level can then be measured using the pressure. The signal from the sensor 5 is sent to a controller 6 , which controls the speed of the motor M as a function of the measured level signal and thus the speed of the sieve 1 . In the area above the permissible maximum of the filling level F _S , a schematically indicated pressure roller 7 is arranged, which is acted upon by a spring 8 and is pressed against the trap layer 9 formed, and thus press this trap layer in advance. Opposite the inlet basin 2 there is a scraping device 10 which detaches the catch layer 9 from the rotary sieve, so that this catch layer can then fall into a collecting container 11 arranged underneath, from where it is compressed, for example by means of the piston 12, then transported away for further storage.

A motor is used as the motor M, which is widely used Ranges, for example, over a ratio range of 1:20 is continuously variable in speed. A Hydromotor is particularly suitable for this. of course is it is also possible to work with other motors that do Provide opportunity with changeable across wide areas Speeds to work.

As mentioned, the sensor 5 can be a membrane sensor, but any type of sensor can be used insofar as this makes it possible to carry out a level measurement. It is also possible to work with two sensors that allow the maximum and minimum fill level to be recorded.

With the device shown schematically can now mechanical pre-cleaning according to the invention strong polluted wastewater can be carried out as follows:

When the system is at a standstill, there is no dirty water to be cleaned in the inlet tank 2 . After the dirty water has run in, the system is put into operation in that when a certain filling level is reached, the sensor 5 emits a signal which sets the motor M in motion. The speed of the rotary screen 1 is now controlled via the sensor 5 and the control device 6 so that the fill level F _{S is} so high that it extends as far as possible to the overflow point 13 . Expressed in percentages, the filling height FH measured in the feed tank 2 from an imaginary line at the height of the axis A upwards (see F _H in the drawing) should be at least 80% of the radius r of the rotary sieve. This measure represents the minimum fill level F _S that ensures reliable formation of the trap layer and also prevents the formation of a sludge roller that rolls back again and again. When regulating the fill level to this high value, the sludge particles are reliably entrained with the roller jacket due to their adhesive action, and then pressed out by the pressure roller 7, forming the trapping layer.

If suddenly a large amount of wastewater occurs, the level F _S in the inlet tank 2 rises. This is accompanied by an increase in pressure, which is detected by the sensor 5 . The sensor 5 transmits this signal to the control device 6 , which then correspondingly increases the speed of the motor M and thus the speed of the rotary screen 1 , with the result that the rotary screen provides a larger screen area per unit of time. Conversely, if the amount of dirty water becomes less, the control device 6 acts on the motor in the sense of slowing the speed of the rotary screen 1 so that a constant level control of the level F _S to an optimal value is possible within wide limits. Due to the high level, a trapping layer also forms on the rotary screen 1 over the circumference of the rotary screen that serves as the boundary wall of the inlet basin 2 , with the result that particles smaller than the actual screen diameter of a screen hole can also be captured, in particular sand can also be cleaned reliably. The optimal trapping layer formation is favored by the fact that, due to the high water level, a hydrostatic pressure leads to the particles being pressed onto the sieve surface, which considerably improves the cleaning effect compared to systems which work with a lower fill level.

If the fill level drops below a certain minimum value due to the absence of wastewater, so that the optimal fill level F _S can no longer be adjusted even with very slow movement of the rotary screen, the system is switched off completely.

The maximum speed of rotation of the rotary screen is against it designed so. that the catch layer also at maximum peripheral speed of the rotary screen is not tears off or according to the amount of water on ingredients as much as possible is retained.

The wastewater presses through the trap layer and flows through the openings of the rotary sieve, the solids adhering to the outer surface or the trap layer of the rotary sieve 2 as explained and taking part in the rotation of the rotary sieve, that is to say then being raised together with the outer surface, above the apex 13 of the rotary screen 2 are conveyed away and finally dropped according to the arrow into the discharge conveyor 11 , 12 .

The wastewater 14 which passes through the sieve and reaches the inside of the rotary sieve 1 and which is then freed to a large extent from solids up to the size of the grain of sand, passes under gravity to the lower vertex of the rotary sieve and there approximately at the position of the arrow 14 from the rotary sieve out. At this outlet, the openings in the rotary screen, ie the screen holes, are automatically cleaned. This water 14 can then be fed to a further purification, for example a biological purification stage.

The device according to the invention and the method according to the invention, according to which a fill level control is carried out automatically at a relatively high fill level F _S , brings with it many other advantages besides the detailed explanation of the reliable formation of the filter auxiliary layer. The system can work completely independently without the need for an operator to monitor the system. The device is able to process large shock loads with regard to intermittent, high inflow water quantities by automatically increasing the speed of the rotary screen accordingly. The device can be used as a pre-cleaning stage in a wide variety of sewage treatment plants without having to make a specific length selection. No length adjustment and selection of a rotary screen of a certain length is necessary because the most varied amounts of dirty water can be taken into account by changing the speed accordingly. In the solution according to the invention, there is generally no need for a bypass line, which are provided in systems according to the prior art, since in the invention the device responds to an increased supply of dirty water by increasing the speed of the rotary screen, while in systems according to the prior art Technology is not possible or only to an insufficient extent. In the drawing, an alternative embodiment is indicated by dashed lines, the side walls 4 a and 4 b of the inlet container being pulled out beyond the upper apex 13 , so that the rotary screen 1 forms part of the bottom of the inlet container 2 . On the left side wall 4 b in the drawing, a seal 15 is attached at the lower end, which prevents water from escaping. In this variant, too, which can then be operated at a substantially higher level F _S , the level is automatically controlled. A sludge roller formation is prevented in this solution in that the wall 4 b towards the outlet side is already above the apex 13 of the rotary screen 1 , so that rolling back of a sludge roller is in principle not possible. This variant opens up the possibility of working with such a high fill level that the trapping layer is pressed out due to the hydrostatic pressure, so that a well-pressed trapping layer is obtained after the trapping layer has passed under the seal 15 . In a specific embodiment, the seal 15 can also be designed as a spring-loaded, roller-shaped seal, so that it takes over the function of a combined sealing and pressing roller.

Another variant is shown in FIG. 2. There, a spring-loaded roller corresponding to the pressure roller 7 is not used for pressing, but an endless belt 17 guided over two rollers 18 and 19 , the two deflection rollers 18 and 19 being arranged offset in height in such a way that the belt rests under tension on the peripheral surface of the rotary screen and squeezes the cake or the solid layer.

Claims (12)

1. A method for the mechanical separation of solids from a fluid, in particular for the purification of wastewater, in particular municipal or industrial wastewater, by the wastewater being driven by a roller-shaped rotary sieve which is rotated by a drive and which forms a boundary wall of an inlet basin with part of its circumferential surface is fed in, the solids adhering to the outer surface of the rotary screen, are lifted and taken away by the rotary screen, while the water passes through the openings of the rotary screen into its interior and is thus removed mechanically cleaned, characterized in that the water level in the inlet basin by change the speed of rotation of the rotary screen is regulated between a maximum and a minimum, the minimum of the water level being set so high that the adhesive effect of the solids on the jacket of the rotary screen is sufficient to take the solids on the jacket without being on the man tel forms a constantly rolling back sludge roll and the maximum is set to such a value that no spillover takes place. 2. The method according to claim 1, characterized in that the water level between the maximum and the minimum is continuously regulated in such a way that when the Maximum the drive of the rotary screen to a larger one Speed and when the wastewater sinks to Reaching the minimum to reduce the Rotation speed is regulated.   3. The method according to claim 1 or 2, characterized characterized that the minimum peripheral speed of the rotary screen is designed so that on the The surface of the rotary screen is also the finest Trapping layer retaining dirt particles maximum possible area expansion and that the maximum of Peripheral speed of the rotary screen is designed so that the catch layer even at this peripheral speed does not tear off. 4.Device for the mechanical separation of solids from a fluid, in particular for the purification of wastewater, in particular of municipal or industrial wastewater, with an inlet basin, with a rotary screen which forms a boundary wall of the inlet basin with part of its circumferential surface and with a variable-speed drive for the Rotary sieve, characterized in that the device comprises a control device ( 5 , 6 ) which has at least one water level sensor ( 5 ) for controlling the water level (F _S ) to a certain value or to a certain range of values, which sensor is in operative connection with the drive ( M) of the rotary screen ( 1 ) in the sense of reducing or increasing the speed of the rotary screen ( 1 ). 5. The device according to claim 4, characterized in that the control device ( 5 , 6 ) is designed as a single-point control device in the region of the maximum. 6. Apparatus according to claim 4 or 5, characterized in that a pressure-sensitive membrane sensor is arranged in the region of the inlet basin ( 2 ) as the sensor ( 5 ). 7. Device according to one of claims 1-6, characterized in that a hydraulic motor (M) is provided for driving the rotary screen ( 1 ), the speed of which is continuously variable over a large control range. 8. Device according to one of claims 1-6, characterized in that a frequency-controlled or frequency-controlled motor is provided for driving the rotary screen ( 1 ). 9. The device according to at least one of claims 4-7, characterized in that above the maximum of the water level (F _S ) a pressure roller ( 7 ) is arranged on the peripheral surface and the solid layer ( 9 ) adhering there. 10. The device according to claim 1, characterized in that that the role is spring loaded. 11. The device according to at least one of the preceding claims, characterized in that the inlet container ( 2 ) is enlarged by a wall extending above the rotary screen ( 4 b) upwards beyond the rotary screen. 12. The device according to at least one of the preceding claims, characterized in that an endless belt ( 17 ) is provided for pressing, with two vertically offset deflection rollers ( 18 , 19 ) such that the belt rests under tension on the peripheral surface of the rotary screen.