Abstract: A plurality of substantially parallel filter plates are assembled as a unit and are locatable within a substantially rigid outer shell to provide a closed vessel. Either or both of the unit and the shell are movable relative to the other between a position wherein the unit is sealed within the shell to enable pressurised supply to the shell of medium to be filtered via the plates and a position wherein the unit is at least partially removed from the shell to enable discharge of resultant filter cake from the plates. To improve filter efficiency, reducing the number of plates required and the pressure required, and to allow the removal of the filter plate unit when encrusted with filter cake, substantially impermeable, flexible membrane is provided as a lining to the shell and an additional shell inlet/outlet port is provided and is connected to pressure medium supply means so that a space between the lining and the shell is inflatable by pressure medium for the duration of the filtration operation.

Abstract: A method of separating solid particles from a mixture of solid and liquid components comprises filtering the mixture to provide a damp filter cake and adding a liquid densification aid to the filter cake to promote densification of the cake. The method is useful for separation of inorganic, generally crystalline, materials from aqueous slurries, for example. Suitable densification aids are flocculating agents such as solutions of alginates and gelatin, and surface active agents. The densification aids promote closer packing of solid particles in the filter cake and assist removal of residual liquid component trapped in interstices between particles.

Abstract: In order to wash the lower run of a horizontal belt filter more effectively, and simultaneously provide for tensioning of the lower run, as required when progressing the belt intermittently, a dead weight roller is supported in a bight of the lower run of the filter belt and reciprocates up and down in a wash liquor vessel as a drive roller is alternately extended, so as to advance the upper run of the belt, and retracted. A one way device is located upstream of the dead weight roller to prevent backward movement of lower run. As the bight decreases and increases, rolling action of the dead weight roller rubs the belt and forces wash liquor therethrough. A plurality of dead weight rollers in one or more wash liquor vessels may be provided and they may be guided at their ends in vertical or oblique guide tracks.

Abstract: In horizontal belt filter apparatus wherein the belt is progressed by alternate incremental motion of the upper run and the lower run, wash liquor used for washing the belt in the lower run, e.g. by spraying into a wash box, is recycled and used for washing filter cake on the upper run at several spaced apart locations. Also, in the upper run, a respective compression device is arranged subsequent to each supply of wash liquor in the direction of travel of the upper run, and during compression gas is blown into the filter cake through the pressure plate of each device so as to maximise extraction of liquid. Trays mounted below the belt are connected to vacuum during stationary periods of the upper run and are arranged to ensure separate collection of liquid for successive sections of the upper run, which liquid may optionally be recycled to upstream locations.

Abstract: Batch filtration is carried out within a rockable/rotatable housing, suspension to be filtered being fed in via ports in the upper region onto a curved filter fixed within the housing, and filtrate draining from below, via outlets to which vacuum may be applied. The housing is preferably cylindrical and may be mounted upon rollers or wheels so that rocking or rotating can be effected by belts or chains attached between the housing and a linearly reciprocable member, or by a rotary gear or friction drive wheel acting on the housing circumference, or by rack and pinion means, or a variety of other means. Washing of filter cake, reslurrying, drying by hot gases, and pressurization can all take place "in situ" whilst rocking continues, and discharge of cake is effected via the same ports as for inlet by turning the housing over.

Abstract: The invention provides an improved web guidance mechanism in which the location of a web is detected and any deviation from a desired path is corrected without causing damage to the web material, for example a filter cloth. The improved mechanism includes two tracker units 10 having a pair of rollers 12, 14 defining a nip for an edge margin of a web. The lower roller 14 is acted on by an inflatable actuator 28 in the form of bellows and operative to raise or lower the roller 14 with respect to the upper roller 12. This is achieved by pivotally mounting a bracket 16, which carries the roller 14, and attaching thereto a bar 24 which rests via a contact plate 26 on the actuator 28. The actuator 28 is controlled by a sensor positioned adjacent to an edge of the web and operative to detect the presence or absence of the edge of the web on its desired path. In a preferred embodiment the sensor controls a pneumatic valve operable to inflate or deflate the actuator 28.

Abstract: In a vacuum belt filter, in order to allow for additional washing of filter cake, a plate is mounted in an inclined disposition above the upper run of the belt with its lower end directed upstream so that as the belt is progressed filter cake moves up over said plate. At the top of the plate, the cake drops into a receptacle and is washed and reslurried by liquid from jets before being returned to the belt downstream, preferably immediately below, the inclined plate. As an alternative to immediate return to the belt, reslurried cake may be transported from the receptacle to a reservoir for further washing or prolonged leaching before it is returned.

Abstract: Subsequent to formation of a filter cake upon the surface of belt and further vacuum filtration (via vacuum trays), the cake passed below and is covered by an impervious sheet, and is dried by application of radiation, e.g. microwaves, radio waves, through the sheet, along with further evacuation (via vacuum trays) below the sheet. Because the cake is under suction pressure, the evaporation temperature of the filtrate is lowered to a level which will not adversely affect the cake, and which can be reached very rapidly by application of this form of radiation.

Abstract: A double valve arrangement is installed in intermittently operating vacuum filter apparatus in a pipeline connecting the filter means to a vacuum source to vent the line to atmosphere whenever the vacuum is shut off. This valve arrangement comprises a pipe section provided with a lateral opening, connected to the filter means, and with internal mutually facing annular shoulders disposed at respective sides of the lateral opening, and a piston-mounted sealing disc which is of smaller diameter than the pipe section and is reciprocable inside same to abut sealingly the one or the other of the shoulders and thereby bring the lateral opening into communication with the respective opposing end of the pipe section, which is connected, respectively, either to the vacuum source or to atmosphere. An annular gap is always present between the peripherly of the disc and the internal surface of the pipe section so that movement of the disc, e.g. at a frequency of 5 to 20 cycles per minute, is not impeded by rubbing.

Abstract: An endless filter belt is guided and supported by rollers or non-rotatable guide bars so as to have an upper run which extends above a substantially horizontal drainage plate to which a vacuum may be applied to draw liquid downwards therethrough. The upper run of the belt is shaped by movable guide means, e.g. pivotal arms which raise and lower the respective ends of the upper run and elements which depress a central region of the upper run into contact with the drainage plate, so as to form a receptacle into which a batch of material to be filtered can be placed. After filtration, when vacuum is no longer applied to the plate, the belt is progressed and any filter cake is removed at another location, a fresh section of belt then being available to form another receptacle.

Abstract: A filter belt is progressed stepwise over successive vacuum boxes by a guide roller at the forward end of the upper run being extended from its retracted position to its full line position while vacuum to the boxes is shut off. A displaceable roller permits this by taking up any slack in the belt and return movement of the belt upon retraction of the foremost guide roller is prevented by a unidirectional arrangement in at least one of the rollers guiding the lower return run of the belt. Slurry is fed onto the belt by a first nozzle, optional wash liquor is fed onto the resultant filter cake by a second nozzle and optional recirculated wash liquor is fed by a third nozzle all under the influence of a control which provides for such feed only for a predetermined period of time during the actual movement of the belt.

Abstract: Slurry is fed (at 52) onto the upper run 46 of endless filter belt 48 and is dewatered by intermittently-operating means e.g. vacuum box 54, press assembly 56 and/or gravity box 66. The belt 48 is guided by a number of transverse guide bars 44, 76, 82, 84, 86, 88 and is progressed intermittently by a displaceable guide bar 74 whose forward movement extends the upper run 46. The bar 74 is coupled (e.g. by cables 106) with a slack-compensating guide bar 104 cooperating with the return run of the belt 48 and unidirectional means (e.g. arrester guide 94 and arrester roller 98) located therebetween allows movement of belt 48 only in the forward direction (arrow 114).Because this belt filter incorporates well supported guide bars instead of conventional rollers, the belt 48 can be much wider than has hitherto been practicable and the overall length of the filter may be correspondingly reduced, further obviating guiding problems.

Abstract: In order to progress belt 10 in stepwise manner without the need for a heavy tensioning roller towards the end of return run 19, ram 58 is displaced to the left thereby moving first stepping roll 55 to its dotted line position and extending bight 59 to draw the forward end of upper run 13 into said bight 59. Movement in the opposite direction of belt 10 is prevented by a unidirectional devices, e.g. pawl and ratchet mechanisms (not shown), on rollers 53, 54. Simultaneously, second stepping roll 56 is noved to its dotted line position to correspondingly reduce the extent of bight 60, thereby permitting part of return run 19 of belt 10 to move back into upper run 13. Subsequently, ram 58 is displaced to the right to return rolls 55 and 56 to their initial positions, reduce bight 59 and extend bight 60.

Abstract: Belt 21 on which a residual filter cake has been formed by the action of a suction box (16, FIG. 1) on a slurry, is brought over a filter grid 46 superimposed on a membrane 42 inflation of which causes the filter cake to be compressed upwards against stationary pressure plate 53 for further dewatering. The grid 46 has parallel grooves in its top surface and further parallel grooves in its under-surface, and intersecting with and communicating with those in the top surface, to permit suction to be applied by way of suction pipe 146 and drain duct 45. The belt 21 is intermittently driven, but the arrangement may be such that the belt moves continuously and the grid 46, membrane 42 and pressure plate 53 move in sequence, forwards from a starting position for a certain distance in contact with the belt while applying pressure to the filter cake and then backwards to the starting position out of contact with the belt.

Abstract: Slurry required to be filtered is supplied to a downwardly inclined feed section of intermittently-moving belt 25 by way of supply pipe 20. Inclination of succeeding vacuum section of belt 25, over vacuum boxes 17, ensures even distribution of thin layer of slurry over belt 25, dependent upon angle of inclination, in range 4.degree. to 20.degree. to horizontal (an angle of 8.degree. being illustrated).Subsequently resultant filter cake layer is subjected to mechanical dewatering by an expansible membrane of a lower pressure plate 23 being expanded to press belt 25 with filter cake thereon against underside of counterplate 24.