GB2227184A

GB2227184A - Filter press cloth washing devices

Info

Publication number: GB2227184A
Application number: GB8901207A
Authority: GB
Inventors: Douglas William Brown; Eric Paul Austin; Michael J Hn Gribbin
Original assignee: Coal Industry Patents Ltd; Simon Hartley Ltd
Current assignee: Coal Industry Patents Ltd; Simon Hartley Ltd
Priority date: 1989-01-19
Filing date: 1989-01-19
Publication date: 1990-07-25
Also published as: GB8901207D0

Abstract

The cloths 3, 31 on the separated plates of a filter press are washed by one or more descending spray tubes 5. To compensate for the cloths being partly pulled away from the plates, the tubes 5 are guided so as to remain at a uniform distance from the cloths. As shown tube 5 is constrained to follow a cam 10 shaped to match the cloth 31. Alternatively the gap between cloth and tube may be monitored by optical or electronic means which automatically adjust the tube to maintain the gap constant. <IMAGE>

Description

IMPROVEMENTS RELATING TO FILTER PRESS CLOTH WASHING MACHINES This invention relates to a filter press cloth washing machine of the kind in which the press comprises a plurality of filter plates each covered on either side by removable filter cloths, the plates being held together firmly in operation to filter out solids material from a suspension of material which is passed through the press, and including washing means arranged to traverse the cloths between adjacent plates to spray the cloth with a liquid to remove the cake particles attached thereto.

One of the most popular forms of filter press is a side bar press where a large number of plates, each covered with a filter cloth, are clamped together by a hydraulic or mechanical racking arrangement which presses the plates hard against each other as the liquid to be filtered is passed through them. Such processes will operate continually for a relatively long time depending upon the nature of the suspended material being filtered. The filtered material adheres to the filter cloth and becomes a cake and the cleaned liquid or filtrate flows out of the machine. As time goes on the chambers between the plates become filled with material and it is necessary to remove this filtered cake periodically.

To remove the cake, the press is opened and a side mounted ratchet arrangement serially moves the plates apart, so that access can be had to the filter cloths covering each plate and the cake adhering to these cloths removed. When filter cloths are new or have been freshly cleaned all cakes discharge from the press freely and without assistance. After several cycles the cloths may blind with entrapped fines in the cloth weave and assistance is required to aid discharge.

One of the ways of removing this cake is physically to take a spatula and lever the cake off the cloth. This is very hard physical work for an operator and there is the risk that the cloth may be damaged by the spatula tearing at the cloth material. An alternative way of dealing with a cake has been suggested, which is to vibrate the cloth and cause the cake to break away from the face of the cloth. A third way is to use a cake release device which pulls the filter cloths away from the plates, pulling the cake with it and hence discharging it. This is not always successful, particularly if the filter cloths are blinded and often the spatula has to be used to assist stubbornly adhering pieces of cake, even when using cake release devices.

A more effective way is to ensure the filter cloths are efficiently cleaned at frequent intervals. This can be done by using high pressure hoses which an operator sprays onto the exposed face of the cloth and the cake is washed away. Recently, cloth washing machines for filter presses have been proposed where the cloth is washed automatically by sparge pipes with jets of water emanating from them traversing the face of the cloth. The use of such cloth washing machines presents problems of its own, since the machines usually have to be situated above the filter press and introduced into the limited space between the filter cloths. If the cloths are held to the filter plates while the washing machine.

traverses their length, then cleaning is reasonably efficient.

However, with most types of filter press where the cloth is pulled away from the face of the plates to assist in washing it is difficult to get an efficient wash of the cloths, because of the angle at which the filter cloths are held. As the washing machine sparge pipes pass between the cloths, they exert a high pressure on the parts of the cloth nearest to the machine, but are not so effective on the parts of the cloth furthest from the machine.

It is an object of the present invention to provide an improved cloth washing machine which effectively deals with the problems currently incurred using angled filter cloths.

According to the present invention, a filter press cloth washing machine of the kind described includes guide means provided to guide the washing means along a path parallel to the surface of the cloth being washed.

These guide way means preferably comprise a profiled arm which is traversed by a follower connected to the washing means. The profiled arm is provided with a surface which is profiled to follow the surface of the filter cloth. By the use of the profiling arrangement, the sparge arms are ensured as being kept a constant distance from the face of the cloth and can therefore be positioned to give a maximum washing effect to the cloth over the whole of its length.

Although mechanical means may be the preferred means for guiding the washing means, it is possible that in certain configurations of washing machines, it is not convenient to include a cam and follower arrangement. In these circumstances, either optical responsive or electronically responsive control means may be instituted, which detect the distance of the sparge pipes from the face of the cloth at any one point and using suitable comparative means operate control signals to control the exact position of the sparge arms relative to the filter cloths.

The filter cloths may also include vibrator means to vibrate the cloth while it is being washed to assist in the removal of fine particles entrapped in the weave of the cloth.

In order that the invention may be readily understood, an example of a filter press cloth washing machine, in accordance therewith, will now be described with reference to the four schematic drawings.

In the drawings Figure 1 shows a device for operating the machine mechanically to follow the profile of the cloth, Figure 2 shows a variation of the device of Figure 1 for applying to a cloth on either side of a filter plate, Figure 3 shows the use of the invention in respect to inclined plates and Figure 4 shows the machine in co-operation with deflector means to enable the washing device to enter between the filter cloths.

Referring now to the drawings, the washing machine of the invention is in this example applied to a conventional side bar filter press and is situated above the press and is moved in steps progressively from one end to the other when cleaning is to take place. The washing machine comprises a pair of sparge arms horizontally arranged which drop down between two filter plates when the press is opened, washes the cloths hanging from those plates and then are withdrawn from the press and moved on as the next plates are moved apart to position itself above the gap and then to repeat the operation between the next set of plates.

As the plates of the press are moved apart the cloth is pulled away from the face of the plate and hangs at an angle thereto. If reference is now made to Figure 1, this shows schematically a plate (1) of a series of plates (not shown) in the filter press. The plate (1) is of the kind having a feed port aperture (2) and a cloth (3) is provided on each side of the plate (1). It can be seen that the top part of the cloth (31) on the side of the plate which is to be presented to the washing machine is pulled out at an angle as the hangers (4), from which it is suspended, are moved as the plates are separated. A washing machine having sparge pipes (5) is lowered between plates (1) and as can be seen from Figure 1, each sparge pipe is carried at the end of an articulated arm (6) which has a follower arm (7) which carries at its free end a roller (8) passing over the profiled face (9) of an arm (10) adjacent the end of the washing machine.

Normally the sparge arm (5) would descend in the direction A and would spray water on to the cloth (3). It would be appreciated that as the arm (5) descended, it would become further and further away from the cloth (3) and therefore the effect of the spray would become less as it reached the centre of the plate (1) where it would be at a minimum over the lower half of the plate. However, due to the fact that the roller (8) follows the profile (9) of the arm (10), the articulated arm (6) holds the sparge arm (5) at a constant distance from the face of the cloth over its angled portion (31), and then for its lower portion it maintains a same distance as it drops horizontally. On the return journey, the sparge arm follows the same profile and washes on the way back.By this means the maximum use is made of the pressure of the water emanating from the sparge arm (5) and the whole of the cloth face presented to this sparge arm receives a same maximum washing pressure.

In practice, the washing machine is passing between two plates and the cloths (3) are pulled away on each side, the machine has two sparge arms which wash the cloths (3) between the two adjacent plates and when the washing cycle is completed, the sparge arms are withdrawn from the machine and the plates are closed together to expose further plates. Each washing sparge arm follows a profiled path as in Figure 1. The washing machine is then moved along the top of the filter press, and lowered to wash the next set of cloths in a similar manner.

The washing machine can be of a type which washes the filter cloths on both sides of the same plate at once. This makes no difference to the principle of operation of the invention and the profiled arm (10) can be presented on either side of the arm as the sparge pipes traverse each side of the plate (1). An example of this is shown in Figure 2.

Similarly, in filter presses where the cloth is not pulled away from the plates but the plates are merely inclined apart, as is shown in Figure 3, the arms will work equally effectively.

In the example of Figure 4, where the washing machine washes cloths attached to two plates at the same time, it is necessary to introduce the washing machine by forcing apart the hangers (4) for carrying the cloths (3). This is done by deflector plates (15) shown in Figure (4) as being positioned above the hangers (4).

These deflector plates in their position as shown positioned above the press form effectively a wedge, which when the washing machine is lowered, forces the hangers apart so that the sparge pipes (5) can be positioned adjacent the cloths (3). The sparge pipes are under the control of an hydraulic arrangement (16) which operates to move pipes (5) to follow the profile of the cloth portion (31). In Figure 4 the cam rollers (8) can be seen in their parked position before they can engage the arm (10) (not shown in this Figure).

The use of the invention enables filter cake to be thoroughly removed from a filter press and for the cleaning operation to be effectively and speedily carried out each time the press needs to be cleaned. There is no risk of damage to the filter cloth through the use of any mechanical device. In order to assist with the removal, vibrators may be attached to the cloth hangers (4) so as to shake the cloth as it is washed and to speed even further the cleaning of the cloth.

Claims

CLAIMS:

1. The filter press cloth washing machine of the kind in which the press comprises a plurality of filter plates, each covered on either side by a removable filter cloth, the plates being held together firmly in operation to filter out material from the suspension of material which is passed through the press and including washing means arranged to traverse the cloths between adjacent plates to spray the cloths with a liquid to remove the cake attached thereto, in which guide means are provided to guide the washing means along a path parallel to the surface of the cloth being washed.

2. A machine as claimed in Claim 1, in which the guide means are constituted by a profiled arm having a surface profiled to follow the surface of the cloth and a cam follows the profile of the arm to control the position of the washing means.

3. A machine as claimed in Claim 1, in which the guide means are optically responsive to the distance of the washing means from the cloth.

4. A machine as claimed in Claim 1, in which the guide means are electronically responsive to the distance of the washing means from the cloth.

5. A machine as claimed in Claim 3 or Claim 4, in which the responsive means are connected to an electronic circuitry arranged to correct the position of the washing means and to keep it positioned at a set distance from the filter cloth.

6. A machine as claimed in any preceding Claim, in which a plurality of washing means is insertable between two separated plates of the filter press and each washing means follows its own profiled path to wash the associated filter cloth on each of the facing sides of the plates.

7. A machine as claimed in any of Claims 1 to 5, in which a plurality of washing means is arranged each to wash the associated cloth on both sides of a single plate at the same time.

8. A machine as claimed in any of Claims 1 to 6 and including deflector means for enabling the washing means to pass between a pair of suspended cloths.

9. A machine as claimed in any one of Claims 1 to 6, in which the plates are set at an angle to each other during the washing process.

10. A filter press cloth washing machine substantially as hereinbefore described with reference to Figures 1 or 2 or 3 or 4 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A filter press cloth washing machine of the kind in which the press is a side bar filter press and comprises a plurality of filter plates, each covered on either side by a removable filter cloth, the plates being held together firmly in operation to filter out material from the suspension of material which is passed through the press and including means at the side of the press to enable the plates successively and serially to be separated to release filtered material from between adjacent cloths and further including overhead washing means arranged successively to descend between opened plates to traverse the cloths between adjacent plates to spray the cloths with a liquid to remove the cake attached thereto, in which guide means are provided to guide the washing means along a path parallel to the surface of the cloth being washed.

5. A machine as claimed in Claim 3 or Claim 4, in which the responsive means are connected to electronic circuitry arranged to correct the position of the washing means and to keep it positioned at a set distance from the filter cloth.