AU657406B2

AU657406B2 - Device for regulation of spill-over flow rates, water-filtering plant and corresponding methods of use

Info

Publication number: AU657406B2
Application number: AU38392/93A
Authority: AU
Inventors: Michel Badard; Jean-Louis Dufresne
Original assignee: Instrumentation Service S A; OTV Omnium de Traitements et de Valorisation SA
Current assignee: INSTRUMENTATION SERVICE SA; OTV Omnium de Traitements et de Valorisation SA
Priority date: 1992-05-15
Filing date: 1993-05-06
Publication date: 1995-03-09
Anticipated expiration: 2013-05-06
Also published as: AU3839293A; FR2691269A1; FR2691269B1

Description

V I 657406

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Omnium de Traltement et de Valorisatlon OTV S.A.

Service S.A.

AND Instrumentation ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Device for regulation of spill-over flow corresponding methods of use 0* St

S

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*5 S

*SS*

*J rates, water-filtering plant and The following statement is a full description of this invention, including the best method of performing it known to me/us:- BACKGROUND OF THE INVENTION 1. Field of the Invention The field of the invention is that of water treatment.

More specifically, the invention relates to a device for the regulation of the spill-over flow rate for filtration tanks in water treatment installations or plants.

A water treatment plant generally comprises a plurality of filtering tanks supplied in parallel from a common channel or conduit for the supply of water to .e filtered. In each tank, filtering materials (sand or coal for example) lie on a porous bed. Thus, the water to be filtered is poured into the tank, goes through the layer of filtering materials and is collected in a filtered state beneath the porous bed.

In a water treatment plant, it is desired to have an identical flow rate in each of the different filtering tanks.

It is difficult to obtain such a flow rate, for: firstly, the impurities that are held back during the filtration tend to ftfoul the filtering materials of the tanks and hence limit the flow rate of filtered water, and this fouling of the tanks is not uniform within each tank and from one tanrik to another; and secondly, the number of tanks in operation is not constant (each tank becomes unavailable, for example when it is being cleaned).

Despite these difficulties, the final goal is always to provide for the equal distribution of the total quantity of water to be filtered among the different tanks in operation, notably to: guarantee continu.ty of service and homogeneity of water quality at the outlet of each tank; ensure a time-distributed operation of each tank and thus forecast and manage cases of non-availability related to the cleaning of each of the tanks of the plant; obtain hydraulic operation of the entire unit that requires minimum consumption of energy.

In a known way, in order to obtain an identical flow rate in each of the different filtering tanks of a plant, a flow rate regulator is used on each filtration tank.

The basic principle of a flow rate regulator is the creation of an auxiliary load loss (reducing the water flow rate) varying as a function of the fouling of the associated tank. When the tank is clean, the auxiliary load loss is high. By contrast, when the tank is highly fouled (or clogged), the auxiliary load loss is zero.

A flow rate regulator such as this generally comprises a vertical water delivery passage that ends in its upper part in chamber, with controlled depression, for the shedding of the liquid into a discharge well. The level of the neck of the discharge well is slightly higher than the maximum level of water in the tank.

The regulator also includes a liquid jet vacuum pump that is submerged in the water delivery passage and comprises an air suction conduit connected to the depression chamber. This liquid jet vacuum pump makes it possible to create a vacuum and to maintain it, the air contained in the depression chamber being sucked in by the water current going through the vacuum pump.

The vacuum created in the depression chamber is used make the outgoing :-"water from the tank rise in the central water delivery passage up to the chamber in order to obtain a spill-over wave that gets discharged through the discharge well.

The height of the spill-over wave conditions the flow rate of discharge of o the water into the discharge well.

A hydropneumatic regulation system is used to act on this spill-over wave and hence on the flow rate of discharged water, in bringing into play the quantity of air present in the depression chamber.

Regulators of this type nevertheless have numerous drawbacks.

Indeed the hydropncumatic regulatio-i system used to act on the spill-over wave calls for complex implementation means, and notably air circuits at very low pressure over long distances.

A known approach aimed at overcoming these drawbacks consists in replacing at least a part of the hydropneumatic regulation system by an electronic regulation system, as described in the invention patent application No. FR 2.651.687 published on 15 March 1991.

This document describes a flow rate regulator comprising an imperviously sealed box enclosing a central vertical tube, the lower end of which receives the filtered water coming from the filtration tank. A vacuum is applied to and maintained in a chamber of the box to make the water rise in this box (and more specifically in the tube) before it is discharged through an upper part of the box opening out on to a recovery ditch. The vacuum of the chamber of the box comes from a closed and sealed chamber that is used as a vacuum reserve and is localized on the upper part of the box. First sensors provide information elements on level and water flow rate to regulators which modulate the opening and closing of a regulation value enabling the vacuum of the chamber of the box to be partially breached. Second sensors provide commands for the opening and closing firstly of solenoid valves for placing the chamber of the box in a state of communication with the vacuum reserve chamber and, secondly, of a solenoid valve for placing the box under atmosphere.

Several drawbacks persist however in a flow rate regulation device such as this.

This known device favors a centrifugal discharging of the water (the water comes out of the central tube and is discharged by a ditch placed on the lower part of the box enveloping this central tube) to the detriment of the principle of centripetal discharge of the water (where the water rises in the vertical, peripheral water delivery passage and gets discharged by the central well).

Furthermore, a regulator such as this calls for the use of a complex vacuum reserve system which consumes energy and requires a system of valves that is complex and fallible instead of the principle of a liquid jet vacuum pump that is simple and economical.

4 Furthermore, if the height of the spill-over wave is greatly increased, disturbances arise drawing air into the discharge well (creating a vortex phenomenon). This phenomenon increases the vacuum in the depression chamber, thus increasing the height of the spill-over wave, and the process continues in this way.

There thus arises a divergent phenomenon of an increase in the water flow rate which can be interrupted only by an emergency stoppage of the installation.

The invention is designed notably to overcome these different drawbacks of the prior art.

More specifically, it is an aim of the invention to provide a flow rate regulation device that is compatible with existing devices and that makes use, in a preferred embodiment, of a centripetal discharging of the filtered water.

The invention is also aimed at providing a device such as this that comprises simple, reliable and inexpensive means to set up a vacuum, such as a liquid jet vacuum pump for example.

Another aim of the invention is to provide a device such as this that does not require complex means of hydropneumatic regulation.

A complementary aim of the invention is to provide a device such as this that makes it possible to overcome the above-mentioned situations of runaway or :o •racing of the system, firstly so as to increase the flow rates dischargeable in a given configuration and, secondly, to simplify the return to normal mode of operation S"when the divergent phenomenon of racing has started.

SUMMARY OF THE INVENTION These aims as well as others that shall appear hereinafter are achieved **according to the invention by means of a device for the regulation of the spill-over flow rate, notably for filtration tanks in water treatment plants, of the type comprising a vertical water delivery passage ending at its upper part in a chamber, with controlled depression, for the shedding of the liquid into a discharge well, the device including a liquid jet vacuum pump submerged in the water delivery passage and including a water suction conduit connected to said depression chamber, the air contained in said depression chamber being sucked up by the current of water going through the liquid jet vacuum pump in such a way as to place said chamber in a state of depression, the depression created in the chamber by said liquid jet vacuum pump enabling the water to be made to rise in the vertical delivery passage up to the chamber in order to obtain a spill-over wave which gets discharged by the discharge well, the flow rate of the water discharged into the well being essentially a function of the height of said spill-over wave, and hence of the depression of the chamber, wherein said depression chamber is connected to the atmosphere through a pneumatic valve, said pneumatic valve being driven by: first means for the continuous adjustment of the opening of said pneumatic valve at variable intermediate opening positions, the degree of opening of said valve being notably computed dynamically by said first adjustment means as a function of the flow rate of air sucked in by the liquid jet vacuum pump, each water flow rate value corresponding to a distinct opening position of said pneumatic valve, said opening making it possible, under constant operating conditions, to compensate for the loss of air sucked up by the current of water going through the liquid jet vacuum pump and second means to control the pulses for the opening/shutting of said pneumatic valve; said first continuous adjustment means and said second opening/shutting pulse control means being servo-controlled by control information elements generated by a module for the regulation of the flow rate of water discharged in said discharge well.

In a preferred embodiment, there is a centripetal discharge of the water.

In this case, the discharge well is in the center and is surrounded concentrically by the central water delivery passage.

Furthermore, the vacuum in the controlled depression chamber is obtained by means of a liquid jet vacuum pump, which is simple to implement and inexpensive.

The pneumatic valve for placing the depression chamber under atmosphere is driven by the following complementary means: firstly, the first continuous adjustment means are used for a controlled opening of the pneumatic vale compensating, by continuous variation, for the loss of air sucked up by the liquid jet vacuum pump. As shall be seen hereinafter, these first continuous adjustment means are used also to modify the height of the spillover wave aad hence the flow rate of discharged water.

secondly, the second means, to control the pulses for the opening/shutting of the pneumatic valve, make it possible to interrupt the divergent phenomenon corresponding to a runaway of the device, making it necessary to stop the installation.

In an advantageous embodiment of the invention, said pneumatic valve is constituted by: a first adjustment pneumatic valve driven by said first means for the continuous adjustment of the opening of said pneumatic valve to variable intermediate opening positions; iee a second fast pneumatic valve, driven by said second means to C. control the pulse for the abrupt opening/shutting of said pneumatic oC .valve.

Advantageously, said regulation module gives said control information elements as a function: firstly of an information element on height of spill-over wave given by a water level sensor mounted in said depression chamber, said information element on height of spill-over wave representing the flow rate of discharged water, and secondly, a predetermined value of the flow rate of discharged water.

Advantageously, said predetermined value of the flow rate of water is given by a control module located upstream with respect to said filtration tank, on the basis of an information element representing the flow rate of water feeding said filtration tank.

The invention also relates to a water filtration plant of the type comprising a plurality of filtration tanks fed in parallel from a common conduit for the feeding of water to be filtered, wherein each of said filtration tanks comprise, downstream, a regulation device according to the invention, and wherein said control module gives a same predetermined value for each of the devices.

Finally, the invention relates to methods for the use of a flow rate regulation device according to the invention.

In a first method of use, enabling an increase in the flow rate of water discharged by a device according to the invention, said regulation module generates control information elements such that said first continuous adjustment means: shut the pneumatic valve during a first period of time computed as a function of a value of flow rate to be attained, in such a way that the vacuum in the chamber increases, the height of the spill-over wave increases and hence the water flow rate increases; gradually increase the opening of the pneumatic valve, during a second period of time, so that the vacuum in the chamber decreases, the flow rate continuing to increase up to said value of flow rate to be attained; maintain the open position of the pneumatic valve obtained at the 9 end of the second period of time, in enabling compensation for the loss of air sucked up by the current of water crossing the liquid jet vacuum pump for said flow rate value to be attained.

e 25 In a second method of use, enabling a decrease in the flow rate of water discharged by a device according to the invention, said regulation module generates s* control information elements such that said first continuous adjustment means: increase the opening of the pneumatic valve, during a first period of time computed as a function of a value of flow rate to be attained, in such a way that the vacuum in the chamber decreases, 8 the height of the spill-over wave decreases and hence the water flow rate decreases; gradually decrease the opening of the pneumatic valve, during a second period of time, so that the vacuum in the chamber increases, the flow rate continuing to decrease down to said value of flow rate to be attained; maintain the open position of the pneumatic valve obtained at the end of the second period of time, in enabling compensation for the loss of air sucked up by the current of water crossing the liquid jet vacuum pump for said flow rate value to be attained.

In a third method of use enabling the flow rate of water discharged by a device according to the invention to be decreased swiftly,in reaction to a divergent phenomenon of increase in the flow rate of water, said regulation module generates control information elements according to the following cycle: said second means for controlling the opening!shutting pulses open the pneumatic valve in an essentially total way for a very short period of time so that the vacuum in the chamber decreases sharply, the height of the spill-over wave decreases sharply and hence the 20 flow rate of water attains a value that is low enough to interrupt 0°• **said divergent phenomenon; said first continuous adjustment means, after said very short period of time, maintain a position of opening of the pneumatic valve, S "enabling compensation for the loss of air sucked up by the current of water going through the liquid jet vacuum pump for said flow rate value to be attained.

Advantageously, said cycle is reproduced repetitively, so as to break the divergent phenomenon while at the same time maintaining a high flow rate of discharged water.

BRIEF DESCRIPTION OF THE DRAWINGS 9 Other characteristics and advantages of the invention shall appe from the following description of a preferred embodiment of the invention, given by way of an non-restrictive example, and from the appended drawings, of which: Figure 1 presents a simplified drawing of a water filtration plant according to the invention; Figure 2 presents a simplified drawing of a preferred embodiment of a flow rate regulation device according to the invention; Figures 3A, 3B and 3C present curves representing repectively the water flow rate, the pressure of the chamber and the opening position of the pneumatic valve as a function of time, in the following three cases: increase in the flow rate of discharged water; decrease in the flow rate of discharged water; interruption of a divergent phenomenon of increase in the flow rate of water; .o figures 4A and 4B respectively show the principle of the centripetal flow of water, as implemented in the device according to the invention, and the principle of centrifugal flow of water, as implemented in the prior art device.

MORE DETAILED DESCRIPTION e •ago Figure 1 shows a simplified drawing of a water filtering plant or installation according to the invention. A plant such as this generally comprises a plurality of filtering tanks 1A to 1F, fed in parallel from a common conduit 3 for the feeding of water to be filtered. Each tank 1A to 1F has, downstream, a regulation device 2A to 2F according to the invention. All the water that is filtered by the set of tanks 1A to 1F whose flow rate of discharged water is regulated by the regulation devices according to the invention is brought together in one and the same outlet channel 4.

Each filtration tank 1A to 1F may be isolated or cut off from the feeder channel 3 by means of a solenoid valve 5A to 5F. This isolation takes place, for example, during the cleaning of a tank. A tank 2A (a part of which is shown in figure 2) comprises filtering materials 11 (sand or coal =or example) lying on a porous bed 12. The water to be filtered, coming into the tank 2A by the feeder channel 3 partially fills this tank up to a level 10, and then crosses the layer of filtering materials 11 and is finally collected in a filtered state in the bottom 13 of the tank located beneath the porous bed 12.

The impurities held back during this filtering operation clog the filtering materials 11, thus reducing the flow rate of water that can be filtered.

The device for the regulation of the flow rate of filtered water located downstream with respect to each tank 1A to 1F makes it possible to get rid of the variations in flow rate du., firstly, to the fouling of the corresponding tank and, secondly, to the unavaiLilty of this tank, for example when it is being cleaned.

Figure 2 shows a simplified drawing of a flow rate regulation device according to the invention, the corresponding tank being also visible.

A solenoid valve 5A (or siphon) enables the feeder channel 3 to be connected to the filtration tank 1A (or enables the filtration tank 1A to be isolated).

A solenoid valve 14 enables the tank 2A to be isolated from the regulation device according to the invention.

The flow rate regulation device comprises a li::,ical water delivery passage terminated at its upper part by a chamber 18, with czntrolled depression, for the shedding of the liquid into a discharge well 16.

This device also includes a liquid jet vacuum pump 19 submerged in the S water delivery passage 15. This liquid jet vacuum pump 19 comprises a water suction conduit 20 connected (21) to the depression chamber 18. The air contained in the chamber 18 is sucked up by the current of water which goes through the vacuum pump 19. Thus, the vacuum created in the chamber 18 by the liquid jet vacuum pump 19 enables the water to be made to rise in the vertical water delivery passage 15 up to the chamber 18 in order to obtain a spill-over wave 22 which gets discharged through the discharge well 16.

11 A modification of vacuum in the chamber 18 enables the varying of the height h of the spill-over wave 22 and hence the varying of the flow rate of discharged water.

The liquid jet vacuum pump 19 comprises a hydraulic valve 25 for the regulation of the flow rate of the current of water going through it. This hydraulic valve 25 is either open (liquid jet vacuum pump in operation) or shut (liquid jet vacuum pump stopped).

The depression chamber 18 is connected to the atmosphere through a pneumatic valve constituted, in this embodiment, by: a first adjusting pneumatic valve 23 driven by first means 26 for the continuous adjustment of the opening of this pneumatic valve at variable intermediate positions of opening; a second fast pneumatic valve 24, driven by second means 28 to S"control the pulses for the abrupt opening/shutting of the pneumatic 15 valve.

ft ftIt is also possible to use only one valve having both high precision during S the fine adjustments of the degree of opening and high speed of opening/shutting during the abrupt control pulses.

The first continuous adjustment means 26 and the second opening/shutting pulse control means 28 are servo-controlled by control information elements (33, 34 respectively) generated by a module 30 for the regulation of the flow rate of the water discharged into the discharge well 16.

Each water flow rate value corresponds to a distinct position of opening of the pneumatic valve. This opening makes it possible to compensate for the loss of air sucked up by the water current crossing the liquid jet vacuum pump 19.

This principle of the dynamic maintaining of the vacuum in the depression chamber makes maximum use of the possibilities of electronic regulation unlike, for example, the vacuum reserve type of static systems used in the prior art (which, furthermore, consume more energy).

The regulation module 30 supplies the control information elements 33, 34 as a function of: firstly, an information element 32 on height h of the spill-over wave 22, this information element 32 on the height h of the wave being given by a water level sensor 27 mounted in the depression chamber 18, and, secondly, a predetermined value 39 of the flow rate of water to be filtered, this predetermined value being given by a control module 36 located upstream with respect to the filtration tank 1A, on the basis of an information element 37 (given by a sensor 38) representing the flow rate of water feeding all the filtration tanks 1A.

The information 32 on height h of the spill-over wave 22 represents the discharged water flow rate.

The hydraulic valve 25 and the solenoid valves 5A and 14 are driven by an automatic control module (not shown) for putting the filtration tank into operation and stopping it.

The regulation module 30 works without outside intervention when the filtration tank is put into operation or stopped.

The filtered water, removed by the well 16 which is surrounded by the water delivery passage 15, reaches a conduit 17 of filtered water receiving filtered water through all the tanks of the installation.

The height of the spill-over wave, which determines the value of the flow rate of discharged water, has a certain degree of instability due notably to the effect S wherein the water discharged by the central well carries along air.

A characteristic coefficient of this instability is, for example c h/R, where n is the height of the spill-over wave, and R is the width available for the spill-over.

The following numerical example, explained with reference to figures 4A and 4B, can be used to compare centripetal and centrifugal flows of water in a regulation device of the type used in the invention.

13 Figure 4A corresponds to the case of centripetal flow. The water rises in the central tube 42 and gets discharged, in the direction indicated by the arrows 41, by the external tube 43.

Figure 4B corresponds to the case of centrifugal flow. The water rises in the central tube 43 and gets discharged, in the direction indicated by the arrows 44, by the external tube 43.

In these two cases: the diameter of the external tube 42 is 120 centimeters; the diameter of the central tube 43 is 90 centimeters.

Consequently, the width R available for the spill-over is 45 cm in the centripetal case and 15 cm in the centrifugal case.

The coefficient u is therefore, with a wave height equal to 10 cm: 2: a 10/45 in the centripetal case; S- a0 2 10/15 in the centrifugal case.

We have a 1 r 2 which means that the instability is greater in the centrifugal case.

In the preferred embodiment of the invention, as shown in figure 2, the flow of the water is centripetal, the discharge well being central and surrounded S concentrically by the vertical water delivery passage.

It is clear, however, that many other embodiments of the invention, bringing into play notably a centrifugal flow of water, can be contemplated without going beyond the scope of the invention.

In the case of a centrifugal flow of watcr, the term "discharge well" is taken to mean the crown located between the central tube 43 and the external tube 42.

The methods for using a flow rate regulation device such as the one shown in figure 2 are presented in relation to figures 3A, 3B and 3C. These figures show curves representing respectively the water flow rate, the pressure of the chamber, the opening position of the pneumatic valve, as a function of time. The methods explained correspond to the following three cases: increasing of the discharged water flow rate (I) 14 interruption of the divergent phenomenon of an increase in the water flow rate (II); decreasing of the discharged water flow rate (III).

The pressure in the chamber (figure 3B) is always between zero atmosphere, namely conditions of perfect vacuum, and one atmosphere, namely conditions of being under open air.

The opening position of the pneumatic valve may vary between an open position and a shut position, this variation being continuous through the first means for the continuous adjustment of this opening.

The first case relates to an increase in the flow rate of water removed by a device according to the invention, and corresponds to the following method: The regulation module generates control information elements such that the first means for the continuous adjusting of the opening of the pneumatc valve at variable intermediate opening positions shut the pneumatic valve during a first C.•me e period of time that is computed as a function of a flow rate value to be attained.

In this way, the vacuum in the chamber increases, makes the water rise in the vertical delivery passage and, consequently, the height of the spill-over wave also increases. This increasing of the height of the spill-over wave leads to an increase in the discharged water flow rate.

After this first period of time, the first continuous adjustment means gradually increase the opening of the pneumatic valve, during a second period of time. In this way, the vacuum in the chamber decreases gradually while the flow rate continues to increase slowly up to the value of the flow rate to be attained.

Finally, the first adjusting means maintain the opening pCsition of the pneumatic valve obtained at the end of the second period of time. This opening is such that it makes it possible to compensate for the loss of air sucked up by the current of water going through the liquid jet vacuum pump for the flow rate value attained at the end of the second period of time.

The third case (III) relates to a decrease in the flow rate of water removed by a device according to the invention, and corresponds to the following method: The regulation module generates control information elements such that the first means for the continuous adjusting of the opening of the pneumatic valve at variable intermediate opening positions increase this opening, during a first period of time that is computed as a function of a flow rate value to be attained.

In this way, the vacuum in the chamber decreases, and so does the height of the spill-over wave, and consequently the flow rate of water decreases.

After this first period of time, the first continuous adjustment means gradually decrease the opening of the pneumatic valve, during a second period of time. In this way, the vacuum in the chamber increases, while the flow rate continues to increase up to the value of the flow rate to be attained.

Finally, the first continuous adjusting means maintain the opening position of the pneumatic valve obtained at the end of the second period of time. This :opening position is such that it makes it possible to compensate for the loss of air 9 O' sucked up by the current of water going through the liquid jet vacuum pump for the 15 flow rate value attained at the end of the second period of time.

The implementation of these two methods is possible only if the regulation device comprises means that enable the continuous adjusting of the opening of the pneumatic valve, The first case and the third case correspond to the standard situations of the changing of the flow rate due to a fouling of the tanks and/or the unavailability of one or more tanks for reasons of cleaning. These cases are perfectly known and 9 9 managed.

The second case (II) relates to a swift decrease in the flow rate of water discharged by the device in order to interrupt a divergent phenomenon of an increase in the flow rate of water. A phenomenon of this kind occurs for example if the height of the spill-over wave is greatly increased. Indeed, there occur disturbances (the vortex or whirlpool phenomenon) that carry along air into the discharge well, thus increasing the vacuum in the depression chamber and causing an increase in the height of the spill-over wave. This increase in the height of the spill-over wave gives rise firstly to an increase in the flow rate of discharged water 16 and, secondly, to an increase in the quantity of air carried along into the discharge well. There is then a divergent phenomenon of an increase in the flow rate of water that cannot be interrupted, in a standard way, except by an emergency stoppage of the plant.

The method according to the invention corresponding to this second case (II) is the following one. The regulation module generates control information elements such that: the second open-shut pulse control means open the pneumatic valve completely during a very short period of time (equal to a Dirac pulse). In this way, the vacuum in the chamber falls sharply, and so does the height of the spill-over wave, and consequently the water flow rate reaches a value that is low enough to interrupt the :divergent phenomenon.

after the foregoing very short period of time, the first continuous 15 adjusting means maintain an opening position of the pneumatic *:•::valve that makes it possible to compensate for the loss of air sucked S. up by the current of water going through the liquid jet vacuum .pump for the value of the flow rate attained, so as to recover stable operating conditions.

Through this principle of using pulses to activate the placing of the depression chamber under atmospheric pressure,. the phenomenon by which the divergent process is triggered can be controlled with ease. If necessary, several *successive pulses, adequately spaced out in time, according to a periodicity established by the regulation means (which those skilled in the art could program adequately for this purpose) enable the stability of the flow system to be preserved, which at the same time providing for major flow rate values.

Thus, according to the tests made, the device according to the invention can carry out flow rate regulation to a level of up to 100% of the maximum flow rate whereas the known prior art devices cannot go beyond 80% of the maximum flow rate, i.e. beyond the upper limit of the triggering of the divergent process.

17 Indeed, beyond 80%, these devices are no longer capable of interrupting thle divergent phenomenon without interrupting the working of the plant.

00.* *&Mt 0000

Claims

1. A device for the regulation of the spill-over flow rate, not,bly for filtration tanks in water treatment plants, of the type comprising a vertical water delivery passage ending at its upper part in a chamber, with controlled depression, for the shedding of the liquid into a discharge well, the device including a liquid jet vacuum pump submerged in the water delivery passage and including a water suction conduit connected to said depression chamber, the air contained in said depression chamber being sucked up by the current of water going through the liquid jet vacuum pump in such a way as to place said chamber in a state of depression, the depression created in the chamber by said liquid jet vacuum pump enabling the water to be made to rise in the vertical delivery passage up to the chamber in order to obtain a spill-over wave which gets discharged by the discharge well, the flow Oe rate of the water discharged into the well being essentially a function of the height 15 of said spill-over wave, and hence of the depression of the chamber, 'wherein said depression chamber is connected to the atmosphere through a pneumatic valve, said pneumatic valve being driven by: first means for the continuous adjustment of the opening of said pneumatic valve at variable intermediate opening positions, the degree of opening of said valve being notably computed dynamically by said first adjustment means as a function of the flow rate of air sucked in by the liquid jet vacuum pump, each water flow rate value *corresponding to a distinct opening position of said pneumatic valve, said opening making it possible, under constant operating conditions, to compensate for the loss of air sucked up by the current of water going through the liquid jet vacuum pump and second means to control the pulses for the opening/shutting of said pneumatic valve; said first continuous adjustment means and said second opening/shutting pulse control means being servo-controlled by control information elements generated by 19 a module for the regulation of the flow rate of water discharged in said discharge well.

2. A device according to claim 1, wherein said pneumatic valve is constituted by: a first adjustment pneumatic valve driven by said first means for the continuous adjustment of the opening of said pneumatic valve to variable intermediate opening positions; a second fast pneumatic valve, driven by said second means to control the pulse for the abrupt opening/shutting of said pneumatic valve.

3. A device according to claim 1, wherein said regulation module gives said control information elements as a function: firstly of an information element on height of spill-over wave given by a water level sensor mounted in said depression chamber, said information element on height of spill-over wave representing the rate of discharged water, and "secondly, a predetermined value of the flow rate of discharged water.

4. A device according to claim 3, wherein said predetermined value of the flow rate of water is given by a control module located upstream with respect to said filtration tank, on the basis of an information element representing the flow rate of water feeding said filtration tank.

5. A water filtration plant of the type comprising a plurality of filtration 0oCC -tanks fed in parallel from a common conduit for the feeding of water to be filtered, wherein each of said filtration tanks comprise, downstream, a regulation device according to claim 4, and wherein said control module gives a same predetermined value to each of the devices.

6. A method enabling an increase in the flow rate of water discharged by a device according to claim 3, wherein said regulation module generates control information elements such that said first continuous adjustment means: shut the pneumatic valve during a first period of time computed as a function of a value of flow rate to be attained, in such a way that the vacuum in the chamber increases, the height of the spill-over wave increases and hence the water flow rate increases; gradually increase the opening of the pneumatic valve, during a second period of time, so that the vacuum in the chamber decrea- ses, the flow rate continuing to increase up to said value of flow rate to be attained; maintain the open position of the pneumatic valve obtained at the end of the second period of time, in enabling compensation for the loss of air sucked up by the current c, water crossing the liquid jet vacuum pump for said flow rate value to be attained.

7. A method enabling a decrease in the flow rate of water discharged by a device according to claim 3, wherein said regulation module generates control :"information elements such that said first continuous adjustment means: increase the opening of the pneumatic valve, during a first period ~of time computed as a function of a value of flow rate to be attained, in such a way that the vacuum in the chamber decreases, the height of the spill-over wave decreases and hence the water flow rate decreases; gradually decrease the opening of the pneumatic valve, during a second period of time, so that the vacuum in the chamber increases, the flow rate continuing to decrease down to said value of flow rate to be attained; maintain the open position of the pneumatic valve obtained at the end of the second period of time, in enabling compensation for the loss of air sucked up by the current of water crossing the liquid jet vacuum pump for said flow rate value to be attained.

8. A method enabling the flow rate of water discharged by a device 21 according to claim 3 to be decreased swiftly, in reaction to a divergent phenomenon of increase in the flow rate of water, wherein said regulation modx,. generates control information elements according to the following cycle: said second means for controlling the opening/shutting pulses open the pneumatic valve in an essentially total way for a very short period of time so that the vacuum in the chamber decreases sharply, the height of the spill-over wave decreases sharply and hence the flow rate of water attains a value that is low enough to interrupt said divergent phenomenon; said first continuous adjustment means, after said very short period of time, maintain a position of opening of the pneumatic valve, enabling compensation for the loss of air sucked up by the current .of water going through the liquid jet vacuum pump for said flow A15 rate value to be attained.

9. A method according to claim 8, wherein said cycle is reproduced repetitively, so as to break the divergent phenomenon while at the same time maintaining a high flow rate of discharged water. a t o* The steps, features, compositions and compou c osed herein or referred to or indicated in jt ecificainand/or claims of this applica ,vidually or collectively, and any and all c ions of any two or more of said steps or features. DATED this SIXTH day of MAY 1993 Omnium de Traitement et de Valorisation OTV S.A. AND Instrumentation Service S.A. 00 9 0. 0@ 60000 by DAVIES COLLISON CAVE Patent Attorneys for the applicant(s) 0*00 ABSTRACT OF THE DISCLOSURE A device for the regulation of the spill-over flow rate for filtration tanks in water treatment plants is of the type regulating a flow rate by varying the height of a spill-over wave, obtained by making water rise in a vertical delivery passage by means of a depression chamber, the wave being discharged into a well, the chamber being put under depression by nrtans of a liquid jet vacuum pump and being connected to the atmosphere through a pneumatic valve driven by: first means enabling, on the one hand, the adjustment by continuous variation of the opening of the pneumatic valve compensating for the loss of air sucked up by the current of water going through the liquid jet vacuum pump and, one the other hand, the modifying of the height of the spill-over wave and hence the discharged water flow rate, second means to control pulses for the openng/shutting of the 15 pneumatic valve, enabling essentially the interruption of a divergent phenomenon of increase in the flow rate of water. Fig. 2 S 6 0