WO2010064913A1

WO2010064913A1 - Cellular filter and cleaning method

Info

Publication number: WO2010064913A1
Application number: PCT/NL2009/050737
Authority: WO
Inventors: Lukas Schoenmakers; Arjan Addink
Original assignee: Visser & Smit Hanab Bv
Priority date: 2008-12-03
Filing date: 2009-12-03
Publication date: 2010-06-10
Also published as: NL2003887C2; NL2003887A

Abstract

The invention relates to a cellular filter with an across the row of cells riding flushing bridge that is provided with the means for the water and air flushing and with along the cells advancing injection nozzle for flushing water and air. There are adjusting means providing a movement of the nozzle perpendicular to the advancing direction along the cells to press the nozzle onto the injection port during cell treatment and to keep it spaced from the cells during advancement. The with the injection nozzle provided injection tube is pivoting mounted and the adjusting means provide a forced pivoting of the injection tube.

Description

Cellular filter and cleaning method.

This invention relates to a system and method to process pre cleaned waste water with a cellular filter (also called 5 backwash filter or Traveling Bridge Filter) .

Basically such filter is comparable to the original design such as e.g. disclosed in GB1056115A, published 25 January 1967. As an example, NL1032237 (Grontmi j /Wortel) , published 29 January 2008, and its cited US2002139738A, published 03 March 10 2002, disclose cleaning of the filter by a combination of air and water. For further technical background reference is made to these disclosures. This invention adds to this prior art. By cleaning by using a combination of water and air, the particles clean each other by mutual rubbing such that an 15 improved cleaning effect is obtained compared to cleaning with only water.

With this invention one or more of the following is proposed for improvement:

20 1. The cell that is being cleaned, is better isolated from its environment during flushing, to increase the effectiveness of in particular the air flushing;

2. The injection nozzle advancing along the cells for flushing water and air is better protected against wear while

25 a complete sealing of the temporary connection between injection nozzle and injection port is ensured..

3. The across the cells driving flushing bridge having means for the water and air flush, is provided with means to better avoid a deviation from the desired positioning relative to the

30 cells. Because of that the flushing result can be improved and wear of the filter is avoided.

4. Another shape of the cellular filter.

5. The cellular filter is provided with means to control the fluid velocity through the filter bed. Thus changes in the

35 supply can be attacked, more time can be given for flocculation in the water layer on top of the filter bed or with increasing rate of contamination the fluid velocity through the filter bed can be kept constant such that the time at which flushing the cell must be started can be delayed. 6. The flushing process is optimised.

The features associated with each of the above items are as follows: 1. Each cell is substantially at the level at the lower edge of the flushing hood during flushing provided with a seal which sealingly engages the hood if the latter is in the flushing position. This seal extends preferably completely around to circumferentially sealingly engage the flushing hood. Preferably the seal is part of the supporting edge at which the flushing hood in the flushing position will rest. 2. The along the cells advancing injection nozzle for flushing water and air is by actuating means pressed against the injection port and during advancing is kept spaced from the cells. The actuating means provide a movement of the injection nozzle transverse to the advancing direction along the cells. Preferably the with the injection nozzle provided injection tube is for that swivelling mounted and the actuating means provide a forced pivoting of the injection tube. 3. (a) the flushing bridge is provided with running wheels with a soft running surface, e.g. of rubber or rubber like material, because of which slip with the underground is decreased.

(b) the running wheels of the flushing bridge ride at a concrete surface. The typical steel rails supporting the running wheels are thus superfluous.

(c) the flushing bridge has two or more independently driven wheels.

(d) two or more running wheels, preferably of the non driven type of the flushing bridge are provided with sensors with which the distance covered by the relevant running Wheel is determined and the sensors are connected to a control unit which generates commands from the data from the sensors which are given to the driving system connected to the control motors of the driving running wheels to apply a position correction to the flushing bridge. 4. In stead of in a straight line next to each other the cells are located in a circle such that the flushing bridge can continuously ride in the same direction such that its propulsion can be simplified, wear of the filter decreases and the flushing result is improved. 5. In the supply or exhaust of water to or from, respectively the filter, a control member, such as a valve or slide, is applied to control the water level of the water layer on top of the filter bed and/or the filtrate. Preferably the control member is connected to a control unit which e.g. controls the control member on the basis of measurement data coming from a to the control unit connected sensor that is sensitive to the water level, e.g. the water level of the water layer on top of the filter bed. Preferably a vertically adjustable overflow slide is used, preferably in the exhaust channel for filtrate. With this proposal one can also avoid that the filter is drained empty in case supply of water to be cleaned is absent. 6. The filter, preferably the flushing bridge (also called flushing arm) of it, is provided with one or more measuring implements to measure the flow resistance of the filter bed of a cell. E.g. one measures at the level of the exhaust from a filter cell. Preferably the measurement is carried out during a flushing process, before the actual flushing takes place. Dependent from the measured flow resistance (e.g. the pressure head) the flushing process is adjusted. E.g. a selection is made between two or more predetermined flushing programs, e.g. a short and a long flushing program, or the control unit decides during the flushing process that the relative filter cell to which the measurement is just carried out, will not be subjected to a flushing treatment during the actual flushing process. The control unit will then measure the next filter cell, such that during a flushing process wherein subsequently all filter cells are participate, it can happen that of three subsequent filter cells which are each subsequently subjected to the measurement, the central of the three is not treated by flushing, while the immediate previous and the immediate next filter cell are indeed treated by flushing. A further elaboration of aspect 3 (d) above is as follows:

To ensure simultaneous running and distance determination, one preferably operates as follows: the flushing bridge is at both sides provided with a driven running Wheel and at the one side with a free rotating running wheel with incremental encoder and at the other side with a free rotating running wheel with an absolute encoder. Thus the measurement is carried out at the wheels which are not driven.

The control has a master and a slave frequency regulator. The incremental encoder is connected to both the master and the slave frequency regulator. The absolute encoder is merely connected to the slave frequency regulator. Further the driven running wheel (master) at the side of the incremental encoder is connected to merely the master frequency regulator while the driven running wheel (slave) at the side of the absolute encoder is connecter to only the slave frequency regulator.

If the slave frequency regulator detects a speed change through the incremental encoder it will control the driving motor of the slave running wheel such that the absolute encoder will detect exactly the same speed.

The covered distance is determined from the slave frequency regulator.

With e.g. a PLC the start and stop times can be determined and with it the flushing bridge is located. By means of e.g. a profibus both frequency regulators are started and stopped.

With preferably a selector switch in the position for automatic operation the speed control of the flushing bridge will operate as above described. In the position for manual operation the drive motors can be controlled manually.

The following is furthermore said:

The invention is preferably applied to a cellular filter and method to clean a cellular filter wherein a cell is flushed in a first step with water, preferably thereafter in a second step with air and possibly thereafter in a third step again with water, while the other cells of the filter remain in filtering operation. It is also feasible to simultaneously subject the filter to a water and air flushing.

Each cell is filled with one or more types granular material like sand. Flushing takes place by isolating a filter cell and withdrawing flushing fluid from above the filter cell 5 and/or supplying it below the cell such that the cell is flushed from bottom to top by flushing fluid, opposite to the direction of the fluid stream through the filter cell during filtering operation, such that accumulated contamination is flushed away and is discharged.

10 The filter bed has in practise typically a height between 1 and 1.2 metres. It is feasible to Carry out flushing with air at a frequency which differs, preferably is smaller, then that for flushing with water. E.g. after a filter cell has been flushed 5 times with water, the cell is flushed once with a

15 combination of water and air. Supplying of flushing fluid preferably takes place below the filter bottom. The filter bottom can be designed as flushing caps bottom. During flushing a preferably upward fluid flow is provided within the filter cell. The speed of this upward fluid flow is preferably between

20 40 and 90 metres per hour. The rate of this upward fluid flow can be between e.g. 70,000 and 90,000 litres per hour for each square metre surface area of the filter bed. The flushing fluid can be supplied in many different ways. Preferably through a from the flushing bridge external from the filter cell downward

25 extending tube which at low level can be temporarily connected to the relevant filter cell to be flushed. Alternatively flushing lances are from above from the bridge temporarily inserted into the filter bed, or a fixed network of flushing pipes provided with for each filter cell separate controlled

30 valves, such that from a central supply pipe selectively by switching of the valves the flushing pipes of a filter cell can be supplied without supplying the flushing pipes of the other filter cells.

During flushing preferably a suction hood is located

35 within the water above the filter bed to provide above the filter bed a limited with water filled suction space within which the contamination together with flushing fluid is collected and discharged. This suction hood is preferably suspended from the flushing bridge, preferably adjustable in height.

Description of an example. The enclosed drawing shows a sectional end view of a preferred, the claimed coverage of the invention however not limiting embodiment of the cellular filter of the invention. The not illustrated left hand part is the mirror image of the in the drawing illustrated right hand part. The line 100 central through the wall 10 provides a mirror line.

The cellular filter is made as usual from filter cells 1 which in two straight rows with each 43 filter cells are located next to each other. Depending from the supply flow to be cleaned, this number can be higher or lower then 43. Each cell 1 is in top view substantially right angled and has a bottom 2 and four to the bottom joined, upward extending walls, comprising the outer wall 3 and the inner wall 4. At a distance above the bottom 2 there is a filter plate 5 limiting a filtrate space 6 there below and a with granules filled filter space 7 there above.

At the external side of the wall 3 there is a along all cells 1 of a row extending supply gutter 11 to supply to be cleaned water to each cell. The water level 13 is equal in the supply gutter 11 and a cell 1. Between the two rows of cells there is a discharge gutter 12. The water level 13 within the gutter 12 is kept lower compared to the level 13 within the gutter 11, such that due to this level difference the water to be filtered sinks through the filter bed 7 and from the filtrate space 6 through the hole 14 it arrives into the discharge gutter 12 as filtrate to be discharged therefrom.

The water level in the discharge gutter 12 is controlled by means of an automatic controlled overflow valve. This control member, which is not visible in the drawing, is common for all cells 1 and is for that located downstream from the outflow opening 14 of all cells 1. With the overflow valve the water level 13 within the channel 12 is controlled. With a constant water level 13 within the supply gutter 11, in this manner the level difference across the filter bed 7 can be controlled. By increasing the level difference with increasing contamination of the filter bed 7 by lowering the overflow slide, the water flow through the filter bed 7 can be kept constant. 5 If the overflow slide arrives in its lowest position, the time has come to start the flushing program.

On top of walls 3 and 4 the flushing bridge 8 rides. Below the bridge 8 the suction hood 9 is suspended from hoisting means . Aside the bridge 8 an injection tube 15 is suspended therefrom.

10 The upright walls of each cell 1 are provided with a ledge or shoulder 16 onto which during flushing the lower edge of the suction hood bears such that the space below the hood 9 is completely isolated fro the space above it.

The injection tube 15 reaches to the level of the holes

15 14 in the walls 4 of the cells 1. At 17 the injection tube 15 is pivoting mounted to the bridge 8. In this embodiment the pivot point 17 is provided at a ridgedly to the bridge fixed bracket. At a distance to the pivot 17 an actuator 18 is mounted between the tube 15 and the bridge 8 to provide pivoting of

20 the tube 15 such that the injection nozzle 19 is moved to and from the wall 4 such that the nozzle 19 is temporarily coupled with the hole 14 to flush the relevant cell 1.

During flushing water and/or air are supplied to the space 6 through the tube 15 and contamination, water and possibly

25 air are sucked by suction 20 from the space below hood 9 and above the filter bed 7 and collected in an along all cells of a row extending discharge channel 21 to be further discharged from there.

Claims

1. Cellular filter for water purification with an across the row of cells riding flushing bridge (8) which is adapted to clean the filter bed of an individual cell while the filter operation of all other cells of the row continues, which bridge (8) is provided with means for cleaning the filter bed (7) by flushing and with an along the cells advancing injection tube (15) with injection nozzle (19) for supplying flushing water and air to a cell, comprising adjusting means that provide a movement of the injection nozzle transverse to the advancing direction along the cells to press the injection nozzle onto an in a side wall (4) of the cells provided injection port (14) during treatment of a cell by flushing and to keep the nozzle (19) spaced from the side wall (4) of the cells during advancing of the flushing bridge along the row of cells.

2. Filter according to claim 1, wherein the tube (15) which is provided with the nozzle (19) is pivoting (17) mounted and the adjusting means (18) provide a forced pivoting of the tube (15) to provide the movement of the nozzle (19) towards and away from the side wall (4) .

3. Cleaning method using a cellular filter according to claim 1 or 2, wherein the adjusting means provide a movement of the nozzle (19) transverse to the advancing direction of the bridge (8) along the cells to press the nozzle (19) onto the port (14) during treatment of a cell by flushing and to keep the nozzle (19) spaced from the side wall (4) of the cells during advancing of the flushing bridge along the row of cells.

4. Cellular filter, possibly according to any of claims 1-3, wherein each cell substantially at the level of the lower edge of the hood (9) during flushing is provided with a seal that sealingly engages the hood if said hood is in the flushing position .

5. Cellular filter, possibly according to any of claims 1-4, with one or more of: the bridge (8) is provided with running wheels with soft track, the running wheels of the bridge ride across a concrete surface; the bridge has two or more independently driven wheels; two or more running wheels of the bridge are provided with sensors with which the by the relevant wheel covered distance is determined and the sensors are connected to a control unit which generates commands from the data from the sensors which are provided to the to the control motors connected drive unit of the propulsion wheels to apply a position correction to the bridge.

6. Cellular filter, possibly according to any of claims 1-5, wherein the cells are located in a circle.

7. Cellular filter, possibly according to any of claims 1-6, wherein the supply or discharge of water to and from, respectively, the cellular filter contains a control member to control the water level of the layer on top of the filter bed (7) and/or the filtrate.

8. Filter according to claim 7, wherein the control member is connected to a control unit that controls the member on the basis of measurement data from a to the control unit connected sensor which is sensitive to the water level.

9. Filter, possibly according to any of claims 1-8, provided with one or more measuring implements to measure the flow resistance of the filter bed of a cell.