GB2131315A

GB2131315A - Filter press

Info

Publication number: GB2131315A
Application number: GB08234040A
Authority: GB
Inventors: Robert Rory Adolph Fre Macrory
Original assignee: Rugby Portland Cement PLC
Current assignee: Rugby Group Ltd
Priority date: 1982-11-30
Filing date: 1982-11-30
Publication date: 1984-06-20

Abstract

After a slurry, of e.g. cement, has been treated in a filter press, rams 17 and 30 are used to move not only the movable end plate 15 but all the press plates 16 together as a pack to locations spaced from the fixed end plate 13. Then the plates 16 are moved in succession back to their closed positions against end plate 13, discharging the filter cake, and finally end plate 15 is moved to close the press for the next cycle. <IMAGE>

Description

SPECIFICATION A method and apparatus for filtering a slurry This invention relates to a method and apparatus for filtering a slurry.

It is well known in various industrial processes, for example in the manufacture of cement, to filter a slurry in a recessed plate filter press. Such a press comprises a stack of filter plates which are held in a vertical plane and which may be compressed together by a hydraulic ram or rams between a fixed end plate, known as a "King plate", and a moving end plate. The support structure for the press consists of two end supports which are connected either by overhead beams from which the moving plates are suspended or by side bars on which the moving plates slide. The king plate forms an integral part of one of the end supports. The major surfaces of each plate are recessed below the edge flange and are covered with filter cloths so that adjacent plates form a chamber between them when the edge flanges are pressed together.The plates and filter cloths have a central hole through which slurry can be pumped into the press chambers. Drainage channels behind the cloths allow filtrate which passes through the cloths to escape from the press through ports in the edges of the plates.

When filtration is to take place the plates are closed up against the king plate by a hydraulic ram or rams so that they form a solid pack with the fixed king plate. Slurry is pumped under pressure through the central holes in the plates so that it fills the press chambers. The slurry pressure forces filtrate through the cloths and solids are trapped on the cloth surface where they build up and form a filter cake. When the filtration is considered to be complete the slurry pumping ceases. To remove the filter cake from the press, the moving end plate is withdrawn from the pack of plates so that the filter cake between the moving end plate and the adjacent plate can fall out of the end chamber. Each subsequent plate is then moved separately towards the moving end plate so that each filter cake can drop out in its turn.When all the filter cakes have been thus discharged, the whole pack of plates is located against the moving end plate and there is a gap between the plate pack and the king plate. The hydraulic ram or rams are then operated to close the press by moving the moving end plate and the other plates, as a pack, up against the fixed king plate so that the filtration cycle may be repeated.

Such a press will be referred to hereinafter as "a filter press of the kind referred to." Applicants have observed that if, in operating a filter press of the kind referred to, the moving end plate does not remain absolutely square to the longitudinal axis of the press when it is withdrawn to the open position, some sliding movement must occur between two or more of the moving plates if the pack of plates is to be closed up tightly and give full face contact around the periphery of the king plate.This results in one or more of the following disadvantages, namely: (a) Friction between adjacent plates and their covering filter cloths impedes such sliding movement from taking place so that (i) the ram pressure to close the press causes increased stress on the fixed structure and supports of the press because the fixed structure tries to deform so that the king plate can make full face contact with the adjacent plate and (ii) tight full face contact between adjacent plates is not achieved, thereby increasing the chance of slurry leakage between plates during the subsequentfiltration cycle.

(b) Adjacent plates slide across each other as the closing ram pressure is applied so that there is increased wear of the cloths as they are scuffed together between the plate edges.

The object of the present invention is to reduce or eliminate the aforementioned disadvantages.

As viewed from one aspect, the present invention provides a method of filtering a slurry in a filter press of the kind referred to, in which the press is opened by withdrawing the moving end plate to its open position together with all the moving plates as a completed pack, subsequently returning each moving plate separately one by one towards the king plate and to its closed position thereby discharging filter cakes from the respective press chambers, and finally advancing the moving end plate towards the closed stack of moving plates to close the press in readiness for the next filtration cycle.

As viewed from another aspect the invention provides an apparatusforfiltering a slurry, comprising a filter press of the kind referred to, and means for displacing all the moving plates as a pack from the closed position when the moving end plate is withdrawn.

Preferably, said means for displacing the moving plates comprises one or more hydraulic rams mounted on the end support which incorporates the king plate.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a simplified diagrammatical view of an apparatus according to the invention with the press in the closed position; and Figure 2 is similar to Figure 1 but with the press in the open position.

Referring to the drawings, a filter press comprises two end supports 10 and 11 supporting and rigidly connected to an overhead beam 12. The support 10 incorporates a king plate 13. The beam 12 includes flanges, such as 14, constituting carriagewaysfrom which are transportably suspended a moving end plate 15 and a plurality of moving plates 16, only some of which are shown. The moving plates 16, as seen in Figure 1, extend from the king plate 13 to the moving end plate 15 in a tightly packed stack.

Hydraulic rams 17 are mounted on the end support 10 and connected by tie rods 18 to the moving end plate 15 to position the end plate 15 and, in the closed position, to compress the moving plates 16 between the end plates 15 and the king plate 13. An inputforslurryis indicated at 19 and an outlet for filtrate is indicated at 20.

As so far described, the apparatus is a filter press of the kind referred to, is well known, and does not require further description.

In accordance with the apparatus of the present invention, one or more hydraulic rams 30 are mounted to the end support 10 and connected by means 31 so that, when the rams 30 are operated, pressure is applied to the moving plates 16 so as to transport the whole stack of moving plates towards the moving end plate 15, when the latter is with drawn to the open position of the press, shown in Figure 2.

In operation, when filtration has ceased, the closed press as seen in Figure 1 is opened by operating the rams 17 and 30 to transport the moving end plate 15 and the stack of moving plates 16 to the open position as seen in Figure 2. Thereafter the rams 30 are operated to withdraw the means 31 and the moving plate 16 nearest the king plate 13 is moved back to the king plate and correctly located in relation to the king plate. The remainder of the moving plates 16 are then moved, in turn, towards the king plate and correctly located in relation to the adjacent plate. During this procedure, filter cakes are discharged from the press chambers. Finally, the rams 17 are operated to return the end plate 15 to the closed position and close the press for a further filtration cycle.

It will be appreciated that the rams 17 as described above, are double-acting rams. In an alternative form of the apparatus, the rams 17 may be single acting rams which function to return the end plate 15 to the closed position and close the press. In that case, the single-acting rams 30 alone will be oper ated to transport the moving end plate 15 together with the stack of moving plates 16 to the open position.

With the method and apparatus of the invention, the fixed king plate is retained absolutely square to the longitudinal axis of the press to the adjacent plate is square to this axis when it is moved up against the king plate. Similarly, each subsequent plate is moved up against a plate which is truly square and so takes up a truly square position itself.

Thus, the moving end plate is finally closed against a pack of plates each of which is square to the press axis and therefore there is no tendency for the plates to slide across each other when the hydraulic ram pressure is applied to close the press tightly. Furth ermore, there is no tendency for the press structure to twist to accommodate itself to misaligned plates and therefore no unnecessary stresses are induced in the press structure or its supports.

CLAIMS (Filed on 18 Nov. 83) F 1. A method of filtering a slurry in a filter press of the kind referred to, in which the press is opened by withdrawing the moving end plate to its open position together with all the moving plates as a complete pack, subsequently returning each moving plate separately one by one towards the fixed end plate and to its closed position thereby discharging filter cakes from the respective press chambers, and finally advancing the moving end plate towards the closed stack of moving plates to close the press in readiness for the next filtration cycle.

2. Apparatus for filtering a slurry, comprising a filter press of the kind referred to, and means for displacing all the moving plates as a pack from the closed position when the moving end plate is withdrawn.

3. Apparatus as claimed in claim 2, wherein said means for displacing the moving plates comprises one or more hydraulic rams mounted on the end support which incorporates the fixed end plate.

4. A method of filtering a slurry in a filter press of the kind referred to, substantially as herein described.

5. Apparatus for filtering a slurry, substantially as herein described with reference to the accompanying drawings .

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

require further description.

In accordance with the apparatus of the present invention, one or more hydraulic rams 30 are mounted to the end support 10 and connected by means 31 so that, when the rams 30 are operated, pressure is applied to the moving plates 16 so as to transport the whole stack of moving plates towards the moving end plate 15, when the latter is with drawn to the open position of the press, shown in Figure 2.

In operation, when filtration has ceased, the closed press as seen in Figure 1 is opened by operating the rams 17 and 30 to transport the moving end plate 15 and the stack of moving plates 16 to the open position as seen in Figure 2. Thereafter the rams 30 are operated to withdraw the means 31 and the moving plate 16 nearest the king plate 13 is moved back to the king plate and correctly located in relation to the king plate. The remainder of the moving plates 16 are then moved, in turn, towards the king plate and correctly located in relation to the adjacent plate. During this procedure, filter cakes are discharged from the press chambers. Finally, the rams 17 are operated to return the end plate 15 to the closed position and close the press for a further filtration cycle.

It will be appreciated that the rams 17 as described above, are double-acting rams. In an alternative form of the apparatus, the rams 17 may be single acting rams which function to return the end plate 15 to the closed position and close the press. In that case, the single-acting rams 30 alone will be oper ated to transport the moving end plate 15 together with the stack of moving plates 16 to the open position.

With the method and apparatus of the invention, the fixed king plate is retained absolutely square to the longitudinal axis of the press to the adjacent plate is square to this axis when it is moved up against the king plate. Similarly, each subsequent plate is moved up against a plate which is truly square and so takes up a truly square position itself.

Thus, the moving end plate is finally closed against a pack of plates each of which is square to the press axis and therefore there is no tendency for the plates to slide across each other when the hydraulic ram pressure is applied to close the press tightly. Furth ermore, there is no tendency for the press structure to twist to accommodate itself to misaligned plates and therefore no unnecessary stresses are induced in the press structure or its supports.

CLAIMS (Filed on 18 Nov. 83) F 1. A method of filtering a slurry in a filter press of the kind referred to, in which the press is opened by withdrawing the moving end plate to its open position together with all the moving plates as a complete pack, subsequently returning each moving plate separately one by one towards the fixed end plate and to its closed position thereby discharging filter cakes from the respective press chambers, and finally advancing the moving end plate towards the closed stack of moving plates to close the press in readiness for the next filtration cycle.
2. Apparatus for filtering a slurry, comprising a filter press of the kind referred to, and means for displacing all the moving plates as a pack from the closed position when the moving end plate is withdrawn.
3. Apparatus as claimed in claim 2, wherein said means for displacing the moving plates comprises one or more hydraulic rams mounted on the end support which incorporates the fixed end plate.
4. A method of filtering a slurry in a filter press of the kind referred to, substantially as herein described.
5. Apparatus for filtering a slurry, substantially as herein described with reference to the accompanying drawings .