Known is a pressure filter (SU Inventor's Certificate 1717176 B 01 D 25/12,1992) that contains filtering plates with a filtering fabric between them, a filtered effluent removal collector with feeding channels in the plates and a suspension feeding line with suspension and flushing water drain vents.

Disadvantage of said design is its low efficiency and hence high product costs.

Also known is a pressure filter (RU patent 2156639 B 01 D 25/12, 2000) that contains filtering plates with a filtering fabric between them, a filtered effluent removal collector with feeding channels in the plates, a suspension feeding line with suspension and flushing water drain vents a flushing water feeding line and an additional filtered effluent removal collector, wherein said filtering plates have cavities at both sides, one of the collectors is connected with at least one channel to the cavities at only one side of each of said filtering plates, the other collector is connected with at least one channel to the cavities at the other side of each of said filtering plates, said suspension feeding line has an air drain vent, said flushing water line has ap air feeding vent and is connected to at least one filtered effluent removal collector, and both collectors are interconnected in a detachable manner.

Disadvantage of said design is its low efficiency and hence high product costs.

Also known is a pressure filter (RU patent 2104742 B 01 D 25/12, 2001) that contains a front and rear posts connected with a beam on the top and bottom side brace rods. The top beam that connects said posts bears a set of filtering plates and a die that is in contact with the clamping mechanism. The filtering plates are equipped with filtering screens and attached to the top beam with brackets. Said filtering plates are interconnected, and the first and last plate of the set are connected to the die and the front post, respectively, with stop plates. Said pressure filter also contains a fabric regenerator and a sludge removal mechanism made in the form of tie rods and moving pulleys to which guides and unloading rollers are attached, and filtering plates are installed between the rollers in a zigzag pattern.

Disadvantage of said design is its low efficiency and hence high product costs.

Known is a pressure filter (US patent 4351725 B 01 D 25/12, 1982) that contains a front post with a thrust plate and a rear post with a plate clamping mechanism that are both in contact with a die, top beams and top side brace rods. Between the thrust plate and the die of the pressure filter there is a set of vertical filtering plates with filtering screens. Each filtering plate is attached to the top beam with roller mounted brackets displaced one relative to another about the pressure filter axis and, moreover, the pressure filter contains a filtering plate moving mechanism.

Disadvantage of said design is its low efficiency and hence high product costs.

The object of the present invention was to provide a high efficiency pressure filter.

Another object of the present invention was to reduce the product cost of processed suspension per unit volume.

The objects of the present invention can be achieved using a pressure filter that contains a front post with a thrust plate and a rear post with a plate clamping mechanism that are both in contact with a die, wherein between the thrust plate and the die of the pressure filter there is a set of vertical filtering plates with filtering screens arranged to be able to move horizontally if driven by the filtering plate moving mechanism. Moreover, said pressure filter contains a suspension processing reagent feeding unit that contains a suspension feeding line to which a flocculant feeding line and a coagulant feeding line are connected, a suspension buffer tank the first inlet of which is connected to the suspension feeding line and the outlet is connected both to the pressure filter inlet and to the second inlet of the suspension buffer tank, wherein said suspension feeding line is connected to the mixer installed parallel to said suspension buffer tank via the first inlet and to the suspension tank, wherein the outlet of the contact mixer is connected to the outlet of the suspension tank and to the suspension feeding line upstream the suspension buffer tank inlet, and the outlet of the suspension tank is connected, together with the sorbent feeding line, to the second inlet of the mixer, further wherein the outlet of the contact mixer is separated from the suspension feeding line and the suspension tank by vents, another vent is installed upstream the first inlet of the contact mixer, upstream the suspension buffer tank in the suspension feeding line there are inlets from a clean water feeding line for diluting the source suspension, a coagulant metal salt solution tank and a suspension alkalization system that contains a solid alkaline reagent feeding line connected to the first inlet of a collector to the second inlet of which the water feeding line is connected, the outlet of the collector is connected via a conveyor to the first inlet of the mixer to the second inlet of which the water supply line is connected, the outlet of the mixer is connected to the suspension feeding line, the clean water and salt solution feeding lines have vents, the suspension feeding line has an inlet from the flocculant feeding line downstream the suspension buffer tank outlet, the unit further contains a filtered effluent acidation line that contains an acid tank, the acidation line outlet is connected via a vent to the first inlet of the dilution unit to the second inlet of which the water feeding line is connected via a vent, and the outlet of the dilution unit is connected to the filtered effluent removal line from the pressure filter. The filtering plate has cavities at both sides that form a sludge collection chamber when the plates are assembled, wherein the plate center has a through opening for suspension feeding, the plate corners have filtered effluent removal channels, the bottom of the cavities is corrugated, each filtered effluent removal opening allows filtered effluent draining to a drain line, wherein the suspension feeding opening diameter is 0.04 to 0.80 m, the filtered effluent removal opening diameter is 0. 025 to 0. 5 m and the diameter of the channel in the bottom part of the plate that connects the filtered effluent draining openings to the drain line is 0.02 to 0.20 m. The filtered effluent drain to the drain line is made with flexible hoses between the filtered effluent removal openings in the filtering plate and the drain line connection. The drain line preferably allows air draining by means of a control valve or an upward tube connected to the adsorbent filter. The flocculant solution feeding line inlet to the suspension feeding line preferably provides for maximally rapid mixing of the flocculant solution and the suspension by means of feeding the flocculant solution via circularly arranged connections, tangential feeding, feeding to a turbulator etc.

The filtering plate preferably has a rectangular shape and can be sized from 0.8 x 0.8 m to 2.0 x 2.0 m with thickness of 0.04 to 0.5 m. The filtering plate can be made from cast iron, stainless steel, non-ferrous metal alloys or polypropylene. The plate cavity bottom corrugation can have a pattern consisting of alternating lines or regularly or irregularly arranged conical shapes. Preferably, the walls of the cavities are at 15-35° to the plate surfaces. The reagent feeding device can further contain instrumentation, e. g. densitometers or pH sensors. It can also contain servo drives for supplying the necessary amounts of reagents to the suspension feeding line and for moving the suspension or at least its part to different branches of the suspension feeding line, e. g. pumps or remote controlled vents. Preferably, the filtered effluent drain to the drain line is made with flexible hoses between the filtered effluent removal openings in the filtering plate and the drain line connection. The drain line usually allows air draining by means of a control valve or an upward tube that can be closed by the adsorber.

The flocculant solution feeding line inlet to the suspension feeding line usually provides for maximally rapid mixing of the flocculant solution and the suspension by means of feeding the flocculant solution via circularly arranged connections, tangential feeding, feeding to a turbulator etc.

Said objects are achieved due to the corrugated bottom of the cavities in the filtering plates that reduces the sludge adhesion to the plate surface and provides for the removal of the solid sludge (the solid phase of the suspension) from the chambers formed by the filtering plate cavities between each pair of filtering plates. The filtered effluent removal openings at the corners of the plates accelerates the drying of the suspension solid phase. Experimental choice of the plate opening size maximizes the suspension dewatering rate and increases the process efficiency. Also, to achieve said objects it is necessary to provide a reagent preparation device. This necessity is because the source suspension may contain different ratios of the solid and liquid phases, thus if a suspension containing a higher than acceptable solid phase content is fed, this suspension is diluted with water. This allows further optimization of suspension processing, separation of large part of the liquid phase before the pressure filter and thereby increasing the process efficiency. The addition of metal salt solutions provides for gel like sludge extraction from the liquid phase of the suspension and for more efficient separation of the solid and liquid phases of the suspension, this in turn also allowing separation of large part of the liquid phase before the pressure filter and thereby increasing the process efficiency. The addition of an alkalizing agent to the suspension provides for more efficient separation of the solid and liquid phases of the suspension and allows separation of large part of the liquid phase at least before the pressure filter and/or in the inlet portion of the pressure filter, thereby increasing the process efficiency. After feeding to the suspension buffer tank part of the bound water is released. Where necessary, if the addition of metal salt solution and alkalizing agent failed to provide for sufficient separation of the solid and liquid phases of the suspension, the latter is either run through the suspension tank and then through the mixer in order to increase the time of its interaction with the reagents, where the suspension interacts with the adsorbents, or run through the mixer, the suspension tank and then back through the mixer. In either embodiment of the device the buffer tank provides for the separation of at least 80% of the liquid phase from the suspension. The addition of the flocculant to the suspension provides for the separation of a large part (to 80%) of the bound water that is further removed and for the formation of a solid phase sludge that is further easily separated with the pressure filter. Where it is necessary to increase the time of suspension interaction with the flocculant, at least part of the suspension can be returned to the suspension buffer tank for further separation of the liquid phase. The filtered effluent can be an alkaline medium due to the addition of alkalizing reagents. For this reason it can be neutralized with an acid reagent before draining to the sewage line.

The acid reagent is added to the filtered effluent removal line downstream the pressure filter. Along with said components the device may further contain instrumentation (preferably, densitometers and pH sensors) for monitoring of the suspension parameters along its passage through the device. The device may also contain servo drives, e. g. pumps or remote controlled vents, for supplying the necessary amounts of reagents to the suspension feeding line and for moving the suspension or at least its part to different branches of the suspension feeding line. Said technical result is considerably enhanced due to the attributes included into the dependent claims.

Figure 1 shows the pressure filter according to the present invention in its basis embodiment, Figure 2 shows a view of the filtering plate and Figure 3 shows schematic of the reagent preparation device. The following notations are used in the Figures: front post (1), rear post (2), set of vertical filtering plates (3), suspension processing reagent feeding device (4), filtering plate bottom (5), filtering plate suspension feeding opening (6), filtering plate filtered effluent removal opening (7), filtered effluent drain channel (8), filtering plate bottom cavity (9), filtering plate cavity bottom corrugation (10), suspension feeding line (11), clean water feeding line (12), metal salt solution tank (13), metal salt solution feeding line (14), alkalizing agent mixer (15), alkalizing agent feeding line (16), suspension buffer tank (17), mixer (18), suspension tank (19), flocculant tank (20), flocculant feeding line (21), acid dilution unit (22), acid feeding line (23), filtered effluent removal line (24) and pressure filter (25).

The basic embodiment of the pressure filter operates as follows. A suspension of sewage water from the settling pit containing 97% of the liquid phase and 3% of the solid phase is fed through the suspension feeding line (11). The suspension dewatering process is designed for the above or approximately the above liquid to solid phase ratios. Thus, in the case considered, adding clean water to the suspension through the clean water feeding line (12) is not necessary. A 5% solution of iron chloride is fed from the tank (13) through the line (14) to the line (11).

After the addition of the coagulant the suspension pH is 7.5, therefore the alkalizing solution is fed from the mixer (15) through the line (16) to the line (11) in order to achieve a suspension pH of 8.0-8. 5 in the line (11). This suspension pH provides for the most efficient separation of the liquid and solid phases in the suspension buffer tank (17). Downstream the suspension buffer tank (17) the liquid and solid phase contents in the suspension are 95% and 5%, respectively. A 0. 1% flocculant solution is fed from the tank (20) through the line (21) to the line (11), and approximately 20% of the suspension is returned to the suspension buffer tank (17) for further liquid phase separation. Before the feeding of the suspension to the pressure filter the liquid and solid phase contents in the suspension are 80% and 20%, respectively. This allows a 2. 5-fold increase in the pressure filter efficiency. As far as the filtered effluent pH is 8.2 the addition of a neutralizing agent is not necessary. The final suspension is fed through the suspension feeding filtering plate opening (6) to the set of filtering plates where it passes through the filtering fabric. The solid phase sludge remains in the filtering plate cavities, and the filtered effluent is removed to the drain lines through the filtered effluent removal filtering plate openings (7) and the filtered effluent removal channels (8). As the chambers formed by the filtering plate bottom cavities (9) become filled with the sludge the suspension feeding is stopped, the sludge is removed from the chambers, the chambers are flushed with water and the process is repeated.

The attributes included into the dependent claims allow a 2.5- fold increase in the pressure filter efficiency.