MXPA95004032A - A method and arrangement relating to press filters - Google Patents

Abstract

The present invention relates to a method pertaining to press filters of the kind which include a plurality of press plates (13). Pressure chambers (15), are formed between each pair of plates. A filter cake (16) is formed in each pressure chamber. Upon completion of the dewatering process the cakes are released from the chambers by separation of the press plates. The method is characterized in that emptying of the pressure chambers (15) is achieved by permitting each press plate (13) to rotate freely and swing about an axis (18) which extends generally horizontally through the plane of the plate, under the influence of the released filter cake (16). The press filter is constructed so that each press plate (13) is able to pivot in relation to the rails (14). The pulling devices by means of which the press plates are separated are attached to only one single coupling device (19) on each side of each press plate. The coupling devices (19) are placed on or in the immediate vicinity of th e runner means, in other words in the proximity of the horizontal rail.

Description

A METHOD AND INSTALLATION THAT RELATES TO PRESSURE FILTERS OWNER: SALA INTERNATIONAL AB, Society of Swedish nationality, domiciled at: S-73325 Sala SUECIA.

INVENTORS: JÓRGEN GOLTERMANN, Danish national, residing at: Kldften 2, Nyrad, Dk-4760 Vordingborg, DENMARK HANS GÓRAN HEDLUND, Swedish national, residing at: Gruvángsgatan 7, S-733 36 SALA, SÜECIA, DESCRIPTION OF THE INVENTION The present invention relates to a method and to an installation belonging to pressure filters of the kind including a plurality of press plates, which are brought together towards and in mutual stop contact and pairs of which define a Press chamber between them, in which when an aqueous suspension of solid particles is dehydrated, the solid particles will form a filter cake that is released at the end of the dehydration operation, separating the press plates to empty the pressure chambers. Pressure filters of this kind have been known for a long time. A general problem encountered with such pressure filters has resided in the inability to obtain a sufficiently long cycle time, by which is meant the time between two consecutive dehydration operations. Originally, the pressure chambers in the pressure filters are emptied one at a time, which naturally results in relatively long emptying times. Patent Specifications US-A 4900, 454 and US-A 5,133,884 are described, in connection with methods and installations of pressure filters, which allow that all the filter chambers are emptied generally at the same time and which also treat with the problems that are related to the release of the filter cakes of the pressure chambers. These patent specifications are incorporated herein by way of reference and describe in detail the manner in which such a pressure filter operates and its construction. The latter-mentioned patent specification proposes a method in which the filter cakes are loosened from the filter cloths, lifting the rollers carrying the filter cloths and allowing the rollers to fall against the stationary contact surfaces. , to subject the rolling fabrics to sudden acceleration forces and / or by subjecting the filtering fabrics to cutting forces by moving the lower part of the side filtering fabrics in the direction of the. plane of the fabrics. However, the release of a filter cake from its respective chamber can also become problematic even with a pressure filter of the kind described above, since the filter cake is loosened, the upper part can be loosened first of the filter chamber and thereby cause the loosened filter cake to break or slide down while being held at the lower end of the pressure chamber or while forming a "bridge" at the lower end, thereby which prevents the filter cake from leaving the filter or at least delaying its emptying. Therefore it is necessary to take these problems into account when constructing pressure filters, in whose construction the distances between the plates fully extended or separated, will be large enough to avoid such disturbances or at least reduce the frequency in which such disturbances they happen In practice, an adjustment is made between the disturbances anticipated in the operation and the capacity of the filter, this arrangement greatly limits the possibility of increasing the productivity of the filters per unit volume, since the number of pressure chambers per unit of filter length, is restricted by the distance between the plates of the open press caused by the above reasons and since the risk of operational disturbances can not be completely eliminated. An object of the invention is to provide a method which will solve the problem of emptying the pressure chambers of the loosened filter cakes in a surprisingly simple and effective manner. The method allows old pressure filters and new filters to be easily modified, in such a way that the productivity will be substantially increased compared to the productivity achieved with those filters currently available in commerce. For this purpose, the invention is characterized by the steps and characteristics defined in the following claims. According to the inventive method, the filter cake will leave its respective pressure chambers by virtue of which each press plate is able to rotate freely about a generally horizontal axis and oscillate in a direction through the plane of the plate, under the influence of a filter cake loosened. The horizontal position of the axis of each press side is preferably located in or in close proximity to an imaginary horizontal line, which passes through the center of gravity of the press platen. The press filter is of the kind that includes a plurality of press plates that can be carried towards and away from the abutting contact with each other and pairs of which define between them at least one pressure chamber and in which each plate The press is provided or connected with a rolling roll means which slides out or moves in any other way in the horizontally extending rails and coupling devices for joining the devices separating the press platen. Each pressing plate of the inventive pressure filter is pivotal in a resting position on the horizontal rails. The traction devices which operate to separate the press plates from each other, are mounted in an individual coupling device on each side of the press plate, this coupling device is placed in or on the immediate vicinity of the roller means of rolling, ie in the vicinity of the horizontal lane. The rolling roller means is conveniently placed on generally the same horizontal level as the center of gravity of the press plate or slightly above this level. The traction device on the respective sides of each press plate, has the form of a chain or a system of links, which is attached to the individual coupling devices of all the press plates. In the simplest case, the press plate is able to pivot about an imaginary axis on the sliding surface of the rolling roller means, which in the case of the illustrated embodiment has a curved shape, for example a circular shape, to facilitate the pivoting of the press plate. Alternatively, the construction may be such as to cause the plate to pivot in relation to a rolling roller means having a horizontal sliding surface, for example providing a circular pivot pin which is rotatably positioned in a corresponding recess in a medium of rolling roller, which has the shape of a bearing cup. It should be understood that other structural variations, which will allow the plate to oscillate freely within the scope of the invention. Because the inventive pressure filter plate traction devices are attached to a single coupling device on each side of each press plate in the vicinity of the rolling roller means and the rail, the traction devices will not prevent that the plates oscillate freely during a process of emptying the filter or even prevent such movement, as is the case when the traction devices of the plate are arranged in pairs on both sides of the rail in the pressure filters known hitherto. The invention will now be described in greater detail with reference to the accompanying drawings, in which Figure 1 is a main side view of a full pressure filter.; and Figure 2 is a view corresponding to that of Figure 1, but showing the filter during a pouring step. Figure 1 is a main illustration of a pressure filter 10 having a fixed end plate 11 and a movable end plate 12. Located between the end plates are a number of filter plates 13, which because the filter 10 is assumed to be full, are shown in abutting contact with each other. As indicated by the arrows pointing left in the Figure, the movable end plate 12 presses the press plates 13 together, so that the plates will be hermetically placed against each other, a chamber 15 having been formed. of pressure between each pair of press plates 13-13. In this operational state, the pressure filter 10 is filled with an aqueous suspension of solid particles, by introducing the suspension under pressure into the respective pressure chambers 15 and causing the liquid in suspension to pass through the filter cloths and exit the drainage channels (not shown) in the press platens 13 and the outlet conduits (not shown) connected to the platens. The solid particles in the suspension form a filter cake 16 in each pressure chamber. The movable end plate 12 and each press plate 13 is placed on the horizontal rails 17 mounted on the respective sides of the plates. Figure 2 illustrates the pressure filter 10 of Figure 1 as the pressure chambers 15 are emptied. In this step, the movable end plate 12 is moved away from the press plates 13, as indicated by the arrows that point to the right in the Figure. Because the press plates 13 are connected to each other by tensile devices and because the plate proximal to the movable end plate 12 is also connected to it as for example with the help of chains or connecting means attached to a device 19 individually engaging on each side of the plates, the presser plate ~ 13 will move outwards in succession, ie it will move in the direction of movement of the movable end plate 12. Each pressure chamber 15 will be sequentially emptied from the right to the left in the Figure. When the opening defined by two mutually adjacent press plates 13 becomes sufficiently large, the filter cake 16 present in the pressure chamber 15 defined by these plates 13 will be loosened. As the filter cake loosens, a force acting downward and outwardly on the press plates 13 defining the pressure chamber 15 is established. As a result of this pressure, the lower part of the chamber 15 is forced to expand. This widening of the lower part of the chamber 15 is achieved by virtue of the released cake causing the press plaque, referenced 13A and shown to the right in the Figure, to pivot or oscillate around a horizontal axis 18 located in the proximity of the center of gravity of the dish or immediately above it. The press platen 13A of this form will tend to pivot counterclockwise about its pivotal axis 18 under the influence of the weight of the filter cake 16, thereby rapidly releasing the bottom of the cake 16. filter of the pressure chamber 15 in a simple way. The filter cake 16 is released from the pressure chamber 15 and the press plates 13, 13A that define the chamber and gravitationally wait from the chamber, as indicated by the position of the filter cake 16 shown in the Figure. Because the movable end plate 12 is moved along the rails 14 until all the press plates 13 are separated from each other to the extent allowed by the chains or other traction devices attached to the two devices 19 of coupling in each press plate 13, that is to say in each side edge of the respective press plates 13, each pressure chamber 15 will be emptied in a simple and effective manner without the risk of the filter cake 16 between the respective press plates 13 becoming compacted or forming "bridges" in the pressure chambers. The present invention allows the length of the chain of the traction devices between the two press plates 13, ie the length determining the distance between the press plates, to be considerably shortened, by which it allows the number of Pressure chambers will be greatly increased per unit length of the filter. In this way the invention allows the productivity to be increased considerably with respect to the amount of dehydrated product with each filter with the other filter data remaining unchanged, partly because the number of press platens or pressure chambers may be increased by at least 10-15% and partly because the risk of operational disturbances caused by the block (formation of "bridges") is greatly reduced. The extent to which the production can be increased will largely depend on the tendency of the material to be dehydrated, which blocks the filter forming bridges in it. Having described the invention as above, property is claimed as contained in the following:

Claims (6)

1. A method that relates to pressure filters of the kind which includes a plurality of press plates that can be brought into mutual abutment contact and pairs of which define between them at least one pressure chamber, wherein when dehydrates an aqueous suspension of solid particles, a filter cake consisting of suspended solids is formed in each pressure chamber, so that upon completion of the dehydration process, the press platens are separated from each other to release the filter cake and Allowing the pressure chamber to empty itself, the method is characterized in that by emptying the respective pressure chambers allowing each press plate to be rotated freely under the influence of a released filter cake and to oscillate around a generally horizontal axis, which extends through the plane of the plate.

2. The method in accordance with the claim 1, characterized in that each horizontal press plate is placed on the pivot axis on or adjacent to an imaginary horizontal line, which passes through the center of gravity of the press plate.

3. A pressure filter for carrying out the method according to claim 1 or claim 2, for pressing liquid from a liquid suspension of solid particles, wherein the filter comprises a plurality of press plates that can be carried in and out of the mutual abutting contact and pairs of which define between them at least one pressure chamber, in which each press plate is provided with or connected to a rolling roller means which slides or rolls on rails that are horizontally extending and coupling devices for connecting traction devices, which function to mutually separate the plates, the pressure filter is characterized in that each press plate is pivotal in its position on the rail; because the traction devices, which function to separate the plates that are connected to an individual coupling device on each side of each plate; and in that the coupling device is placed on or in the immediate vicinity of the rolling roller means, ie in the vicinity of the horizontal rail.

4. The pressure filter according to claim 3, characterized in that the rolling roller means is generally placed at the same horizontal level as the center of gravity of the press plate originally above it.

5. The pressure filter according to claim 3 and 4, characterized in that each traction device has the form of a chain or a system of links attached to the individual coupling device of all the press plates.

6. The pressure filter according to claims 3-5, characterized in that the sliding surface on the rolling roller means is configured to facilitate the pivoting of the press plate. SUMMARY OF THE INVENTION The present invention relates to a method belonging to the pressure filters of the class including a plurality of press plates that can be carried towards and in mutual abutment contact and pairs of which form at least one chamber between them. pressure, in which it is formed in each pressure chamber, as the aqueous suspension of solid particles is dehydrated, a filter cake in which at the end of the dehydration process, is released from the chamber separating the press plates from such that the camera will empty itself of its contents. The method is characterized in that the emptying of the pressure chambers is achieved by allowing each press plate to freely rotate and oscillate about an axis, which generally extends horizontally through the plane of the plate, under the influence of the cake of filter released. The pressure filter is constructed in such a way that each pressure plate is capable of pivoting in relation to the rails. The pulling devices by means of which the press plates are separated, are attached to only one individual coupling device on each side of each press plate, this coupling device is placed on or in the immediate vicinity of the roller means rolling, in other words in the proximity of the horizontal rail. Under protest to tell the truth, the best known method for putting the present invention into practice is the one indicated in the description of this application. In testimony of which we sign the present in: Mexico, D.F., to September 21, 1995. SALA INTERNATIONAL AB