Filter press for producing polyaluminum chloride and filter pressing method thereof
By embedding electrode plates and heating plates inside the filter press, selective enrichment and recovery of calcium salts are achieved using electrophoresis effect and mechanical weak layer technology. This solves the problem of decreased Ca²⁺ concentration in the clarified liquid, reduces raw material costs, and meets basicity requirements.
Patent Information
- Application Number
- CN202511314108.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-15
- Publication Date
- 2025-10-21
AI Technical Summary
In existing pressure filtration processes, undissolved calcium sources are removed along with the filter cake, resulting in a decrease in Ca²⁺ concentration and basicity in the clarified liquid, which increases raw material costs and wastes resources. There is a lack of effective calcium recovery solutions.
Alternating positive and negative electrode plates are embedded in the filter press plates to form an electric field that drives the migration of calcium particles. Through a sequence of actions including heating with an electric heating plate and diaphragm control, the selective enrichment and separation of calcium particles are achieved. The in-situ separation and recovery of calcium salts are completed by utilizing the electrophoretic effect and the tearing technology of the mechanical weak layer.
Selective surface enrichment and recovery of calcium salts were achieved, avoiding the loss of basicity in the clear liquid, reducing raw material waste, and directly replenishing the reaction system, meeting national standards and avoiding a vicious cycle of uncontrolled basicity.
Smart Images
Figure CN120815366A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of filter presses, in particular to a filter press for producing polyaluminium chloride and a filtration method thereof. Background Art
[0002] In existing technology, after the aging reaction of polyaluminium chloride (PAC) is completed, it must be separated into solids and liquids through a filter press to obtain a liquid product that meets basicity specifications. However, this filtration process presents the following common industry issues: To adjust the basicity of PAC, calcium aluminate powder (CaO·Al2O3) is typically added to the reaction system. This calcium aluminate powder only partially dissolves during the aging stage, and the undissolved calcium source (CaO, Ca(OH)2, CaCO3) enters the filter press as 10-40µm particles, forming a calcium-rich filter cake layer. However, the existing filter press process discharges the filter cake as a whole, resulting in the removal of undissolved calcium sources along with the filter cake. This causes a decrease in the Ca²⁺ concentration in the clear liquid, which directly manifests as a 3%-5% drop in the basicity of the finished product, falling below the national standard lower limit. Therefore, to compensate for the loss of basicity, companies are forced to add additional calcium aluminate powder, which not only increases raw material costs but also introduces new solid phases, creating a "vicious cycle." Existing cake removal mechanisms only focus on clean discharge. There is currently no "calcium recovery" solution for the PAC filter press process, resulting in wasted resources and fluctuating indicators. Summary of the Invention
[0003] The object of the present invention is to provide a filter press and a filtration method thereof for the production of polyaluminium chloride, so as to solve at least one technical problem existing in the above-mentioned prior art.
[0004] To achieve the above object, the present invention provides the following technical solution: a filter press for the production of polyaluminium chloride, comprising a plurality of plate frames slidably mounted on a crossbeam, wherein the plate frames are composed of two detachable left and right shell plates, and a cavity is provided between the two shell plates, and further comprising: The electrode sheets are arranged in the cavity, the electrode sheets are divided into positive and negative electrodes, and the electrode sheets in adjacent plate frames are designed with positive and negative electrodes crossed; An electric field with an electrophoretic effect is formed in the filter cavity formed between the adjacent plates and frames, and the electric field drives the positively charged calcium particles in the PAC slurry to migrate; An electric heating plate is arranged in the cavity, and the electric heating plate is used to heat the calcium-rich layer formed by the migration of calcium particles.
[0005] Optionally, filter cloths are attached and fixed to the outer walls of both sides of all the plate frames, and a diaphragm is also fixed to the outer wall of the plate frame with the positive electrode, and the diaphragm is located inside the filter cloth and forms a closed space between the plate frame and the plate frame; The filter press also includes an air pipe connected to an external pressure control device, a connecting pipe is connected between the air pipe and the outer wall of the plate frame with the positive electrode, and the connecting pipe is connected to the cavity between the diaphragm and the outer wall of the plate frame.
[0006] Optionally, the filter press also includes hook machines installed on both sides thereof through slide rails and capable of reciprocating movement. A two-dimensional moving system is installed between the two hook machines, and the two-dimensional moving system has two symmetrical designs and can move and adjust adjustment sliders in a plane space. Venturi tubes are installed on the outer walls of the two adjustment sliders, and the Venturi tubes are connected to an external vacuum pump. A flat suction nozzle is provided at the end of the Venturi tube.
[0007] Optionally, the cavity between the two shell plates is divided into an outer ring and an inner ring, and insulating ribs are spaced apart inside the outer ring and the inner ring. The electrode sheet is embedded in the outer ring, and the electric heating plate is embedded in the inner ring.
[0008] Optionally, the fitting surfaces of the two shell plates are respectively provided with a butt joint edge and a groove for the butt joint edge to be engaged and embedded, and the butt joint edge is asymmetrically designed.
[0009] Optionally, the two-dimensional moving system includes a gantry fixed between the two hook machines, and two vertical rails are installed on the gantry through a horizontal electric slider, and the two adjustment sliders are respectively slidably installed in the two vertical rails.
[0010] Optionally, the filter press further includes a drain pipe, and a conduit is connected between the bottom of each plate frame and the drain pipe, and the conduit is used to drain the clear liquid in the filter cavity formed by the combination of the two plate frames.
[0011] Optionally, the filter press also includes a control system, and the control system includes a PLC timer, which is used to control the start-up sequence of the electric heating plate and the pressure control device, and first controls the heating of the electric heating plate, and then the pressure control device first inflates the space between the plate frame and the diaphragm, and finally instantly converts the space between the plate frame and the diaphragm into vacuum, so that the internal pressure is instantaneous.
[0012] Optionally, the filter press further includes a thrust plate and a compression plate, and the compression plate is driven to move by a hydraulic cylinder and together with the thrust plate and the plate frame constitutes a filter press system.
[0013] A filter press method for producing polyaluminium chloride, comprising the filter press for producing polyaluminium chloride, is specifically divided into the following steps: S1. Pump the PAC matured slurry into the filter press, where the adjacent plates and frames are alternately embedded with positive and negative electrodes. The electric field formed guides the positively charged calcium particles in the slurry to move toward the negative electrode frame, forming calcium-rich shells on both sides of the negative electrode frame. S2. When the slurry pump pressure is about to end, the PLC sequencer starts, first controlling the electric heating plate to heat the negative electrode frame, so that the temperature of the side where the filter cake and the plate frame are in contact increases, accelerating the evaporation of water and further reducing its water content, so that a mechanical weak layer is formed between the calcium-rich layer and the filter cake; S3. Secondly, the PLC sequencer controls the pressure control device to first inflate the diaphragms on both sides of the positive electrode frame, causing them to expand and squeeze the filter cake toward the negative electrode frame. At the same time, the expanded curved surface of the diaphragm weakens its adhesion to the filter cake, while increasing the adhesion between the calcium-rich layer and the filter cloth on the negative electrode frame. S4. Finally, the PLC sequencer controls the pressure control device to switch to air extraction, so that an instantaneous negative pressure is formed between the positive electrode frame and the diaphragm. The instantaneous contraction of the diaphragm is used to pull the filter cake back after the impact. The pulling back effect causes the calcium-rich layer and the filter cake to tend to break or directly break from the formed mechanical weak layer. S5. After the frame is opened, the main cake falls off by its own weight, and the calcium-rich layer remains on the negative electrode frame, completing the calcium salt separation of the filter cake, and then it is recovered. The recovered calcium salt is then returned to the furnace to compensate for the calcium salt in the separated clear liquid in the future and make up for the loss of basicity in the clear liquid.
[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention embeds alternating positive and negative electrodes inside the plate frame to form a controllable electric field within the filter cavity. Utilizing the principle of electrophoresis, the positively charged calcium particles are directed and concentrated on the negative electrode frame side. This achieves "selective surface enrichment of calcium" for the first time, allowing calcium to be separated from the main filter cake in advance, laying a physical foundation for subsequent local recovery, thereby avoiding the loss of clear liquid Ca²⁺ and basicity caused by traditional overall cake removal.
[0015] 2. The present invention further introduces an electric heating plate-diaphragm coupling action sequence on the negative electrode frame side: first, heating is performed to produce a calcium-rich layer with a low-water "hard shell", and then the positive electrode frame diaphragm is "inflated-instantaneously evacuated". The filter cake is accurately torn at the mechanically weak layer by a three-step process of expansion-impact-pullback, so that the entire calcium-rich shell remains on the frame and the main cake falls off completely. This set of actions is completed in the filter press without the need for additional equipment, realizing the "in-situ separation and online recovery" of calcium salts. The salt basicity of the clear liquid can be brought back to the upper limit of the national standard by directly replenishing the reaction system, eliminating the waste of raw materials and avoiding the "vicious cycle" of uncontrolled salt basicity. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is the front view of the present invention; Figure 2 This is a schematic diagram of the three-dimensional structure of the present invention from the right side; Figure 3 This is a schematic diagram of the left side stereoscopic structure of the present invention; Figure 4 This is a schematic diagram of the rear-view stereoscopic structure of the present invention; Figure 5 This is a schematic diagram of the exploded three-dimensional structure of the plate frame of the present invention; Figure 6 Schematic diagram of the positions of the plate frame, the diaphragm and the filter cloth thereon; Figure 7 A simplified view of the diaphragm of the present invention after expansion; Figure 8 This is a functional schematic diagram of the panel frame of the present invention; Figure 9 It is a flowchart of the present invention.
[0017] In the figure: 1. crossbeam; 2. thrust plate; 3. plate frame; 31. shell plate; 4. pressing plate; 5. hydraulic cylinder; 6. outer ring; 7. inner ring; 8. insulating rib; 9. electrode sheet; 10. electric heating plate; 11. sealing ring; 12. docking edge; 13. diaphragm; 14. filter cloth; 15. gas pipe; 16. connecting pipe; 17. drain pipe; 18. hook machine; 19. two-dimensional moving system; 20. adjusting slider; 21. venturi tube; 22. flat suction nozzle; 23. filter cake; 23a. main filter cake; 23b. calcium-rich layer. DETAILED DESCRIPTION
[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0019] Example 1: See also Figures 1 to 9 The present invention provides a technical solution: a filter press for the production of polyaluminium chloride, comprising a plurality of plate frames 3 slidably mounted on a crossbeam 1, the plate frames 3 comprising two detachable left and right shell plates 31, with a cavity provided between the two shell plates 31, and further comprising: The electrode sheet 9 is arranged in the cavity. The electrode sheet 9 is divided into a positive electrode and a negative electrode, and the electrode sheets 9 in adjacent plate frames 3 are designed with positive and negative electrodes crossed; An electric field with an electrophoretic effect is formed in the filter cavity formed between adjacent plates and frames 3, and the electric field drives the positively charged calcium particles in the PAC slurry to migrate; An electric heating plate 10 is arranged in the cavity, and the electric heating plate 10 is used to heat the calcium-rich layer formed by the migration of calcium particles.
[0020] Among them, filter cloth 14 is attached and fixed to the outer walls of both sides of all plate frames 3, and a diaphragm 13 is also fixed to the outer wall of the plate frame 3 with the positive electrode, and the diaphragm 13 is located inside the filter cloth 14 and forms a closed space between the plate frame 3; The filter press also includes an air pipe 15 connected to an external pressure control device. A connecting pipe 16 is connected between the air pipe 15 and the outer wall of the plate frame 3 with the positive electrode, and the connecting pipe 16 is connected to the cavity between the diaphragm 13 and the outer wall of the plate frame 3.
[0021] The filter press also includes a control system, and the control system includes a PLC timer, which is used to control the start-up sequence of the electric heating plate 10 and the pressure control device, and first controls the electric heating plate 10 to heat, and then the pressure control device first inflates the space between the plate frame 3 and the diaphragm 13, and finally instantly converts the space between the plate frame 3 and the diaphragm 13 into vacuum, so that the internal pressure is instantaneous.
[0022] Currently, after the aging reaction of polyaluminium chloride (PAC) is completed, it needs to be separated into solid and liquid by a filter press to obtain a liquid product that meets the basicity index. To adjust the basicity of PAC, calcium aluminate powder (CaO·Al2O3) is usually added to the reaction system. However, the calcium aluminate powder only partially dissolves during the aging stage, and the undissolved calcium source (CaO, Ca(OH)2, CaCO3) enters the filter press in the form of 10-40µm particles, forming a calcium-rich filter cake. If the filter cake is discharged as a whole after filtration, the undissolved calcium source will be removed along with the filter cake, resulting in a decrease in the Ca²⁺ concentration in the clear liquid. This directly manifests as a drop in the basicity of the finished product, which in turn falls below the national standard limit. Therefore, a PAC-specific filter press technology that can selectively concentrate calcium on the surface of the filter cake and mechanically recover only the surface is urgently needed to solve the above-mentioned problems of uncontrolled basicity, raw material waste, and increased environmental costs. The specific method is as follows: During production and use of the filter press, after the plates and frames 3 are pressed together, the PAC matured slurry is pumped into the filter press. Positive and negative electrodes are alternately embedded between adjacent plates and frames 3. The resulting electric field uses electrophoresis to guide the positively charged calcium particles in the slurry toward the negative electrode frame, forming calcium-rich layers on both sides. As a result, during the formation of the filter cake, the calcium particles in the filter cake selectively move to one side and are separated from the calcium-poor layer. Secondly, when the slurry pumping is about to end, the PLC sequencer starts, first controlling the electric heating plate 10 to heat the negative electrode frame, so that the temperature of the surface where the filter cake contacts the plate frame 3 is increased, accelerating the evaporation of water in the calcium-rich layer and further reducing its water content, so that a mechanically weak layer is formed between the calcium-rich layer and the filter cake. At the same time, the calcium-rich layer also forms a calcium-rich shell due to the reduction of water content. Furthermore, the PLC sequencer controls the pressure control device to inflate the diaphragms on both sides of the positive frame, causing them to expand and squeeze the filter cake toward the negative frame. At the same time, the expansion curve of the diaphragm weakens its adhesion to the filter cake, while the adhesion between the calcium-rich shell and the filter cloth on the negative frame increases. Figure 7The schematic diagram shown in FIG. 23a is the main filter cake, 23b is the calcium-rich layer, and the diaphragm 13 and the filter cloth 14 can also be designed in the form of an existing diaphragm filter press, which is not further limited here; Subsequently, the PLC sequencer controls the pressure control device to switch to air extraction, forming an instantaneous negative pressure between the positive electrode frame and the diaphragm. The expansion and instantaneous contraction of the diaphragm are used to impact and crack the filter cake, and the pull-back effect causes the calcium-rich layer and the filter cake to tend to break or directly break at the mechanically weak layer formed. Finally, when the plate frame 3 is opened, the calcium-poor main cake falls off by its own weight, while the calcium-rich shell formed by the calcium-rich layer remains on the negative electrode frame, completing the calcium salt separation of the filter cake. The recovered calcium salt is then recycled and returned to the furnace to compensate for the calcium salt in the separated clear liquid in the future, thereby increasing the basicity of the clear liquid.
[0023] In this way, by recovering the calcium salt in the filter cake, not only can the loss of basicity be compensated, but the cost of raw materials can also be reduced, avoiding the formation of a "vicious cycle".
[0024] Example 2, based on Example 1, provides an implementation method for recycling the calcium-rich shell remaining on the negative electrode frame; The filter press also includes a hook machine 18 installed on both sides thereof by a slide rail and capable of reciprocating movement. A two-dimensional moving system 19 is installed between the two hook machines 18. The two-dimensional moving system 19 has two symmetrical designs and an adjusting slider 20 that can be moved and adjusted in a plane space. Venturi tubes 21 are installed on the outer walls of the two adjusting sliders 20, and the Venturi tubes 21 are connected to an external vacuum pump. A flat suction nozzle 22 is provided at the end of the Venturi tube 21.
[0025] For details, please refer to Figure 1-4 First, the main function of the hook plate machine 18 of the filter press is to pull the plate frame 3 apart in sequence when opening the frame, so it will not be described in detail in this case. By installing a two-dimensional moving system 19 between the two hook plate machines 18, when the two hook plate machines 18 pull the plate frame 3 apart, they can stay at the position of the negative electrode frame, and make the two adjustment sliders 20 on the two-dimensional moving system 19 be located on both sides of the plate frame 3 respectively. Then, when the adjustment sliders 20 move downward and move along the two side planes of the negative electrode frame, the flat suction nozzle 22 at the end of the venturi tube 21 can suck the calcium-rich shell attached to the filter cloth 14 of the negative electrode frame back into the furnace, thereby achieving the purpose of simultaneously recovering the calcium-rich shell on both sides of the negative electrode frame. In summary, the recycling process can be completed by pulling the plate frames 3 apart in sequence through the plate hook machine 18 and stopping at the corresponding position of the negative electrode frame without adding any additional steps.
[0026] In one of the more preferred embodiments, a method for mounting the electrode sheet 9 and the electric heating plate 10 is provided; The cavity between the two shell plates 31 is divided into an outer ring 6 and an inner ring 7 , and insulating ribs 8 are arranged at intervals in the outer ring 6 and the inner ring 7 . The electrode sheet 9 is embedded in the outer ring 6 , and the electric heating plate 10 is embedded in the inner ring 7 .
[0027] For details, please refer to Figure 5 By designing the inner and outer rings, the electrode sheet 9 and the electric heating plate 10 can be designed in the same layer, which can make the electric field strength and heating degree more uniform. At the same time, the embedded installation method is also convenient for installation and removal. A sealing ring 11 is also installed at the center hole of the shell plate 31 to improve the sealing performance of the cavity, avoid leakage of slurry and corrosion of the electrode sheet 9 or the electric heating plate 10, and extend the service life; It is worth mentioning that the insulating ribs 8 spaced apart between the inner and outer rings can effectively improve the pressure-bearing capacity of the cavity position and improve its mechanical strength. Moreover, the circuit arrangement of the electrode sheet 9 and the electric heating plate 10 can be achieved by opening a circuit channel in the insulating rib 8 and extending the terminal to the outside of the shell to facilitate power connection. At the same time, it will not affect the disassembly and assembly of the two shell plates 31, and the two shell plates 31 can be assembled by screwing them together.
[0028] The mating surfaces of the two shell plates 31 are respectively provided with a butt joint edge 12 and a groove for the butt joint edge 12 to be engaged and embedded, and the butt joint edge 12 is asymmetrically designed.
[0029] See for details Figure 5 The corresponding design of the butt edge 12 and the groove can play a positioning role when the two shell plates 31 are combined. At the same time, its asymmetric anti-foolproof design can also prevent the direction from being wrong.
[0030] In one of the more preferred embodiments, a specific structure of a two-dimensional mobile system is provided; The two-dimensional moving system 19 includes a gantry fixed between the two hook machines 18, and two vertical rails are installed on the gantry through horizontal electric sliders, and two adjustment sliders 20 are slidably installed in the two vertical rails respectively.
[0031] For details, please refer to Figure 1-4 By adjusting the horizontal sliding of the horizontal electric slider and the vertical sliding of the adjusting slider 20 in the vertical track, the Venturi tube 21 can be driven to move arbitrarily in the plane, thereby recovering the calcium-rich shell. Both the horizontal and vertical sliders adopt existing electric drives, such as motors and screws, and the specific methods will not be repeated in this case.
[0032] The filter press further includes a drainage pipe 17 , and a conduit is connected between the bottom of each plate frame 3 and the drainage pipe 17 , and the conduit is used to drain the clear liquid in the filter cavity formed by the two plate frames 3 .
[0033] The filter press further comprises a thrust plate 2 and a pressing plate 4 , and the pressing plate 4 is driven to move by a hydraulic cylinder 5 and together with the thrust plate 2 and the plate frame 3 forms a filter press system.
[0034] The drain pipe 17, the thrust plate 2 and the pressure plate 4 are all implemented in the existing way. They are not improved in this case, so they will not be described in detail here. It is worth mentioning that since the plate frame 3 is a combined type, conduits are provided on both shell plates 31, and the two conduits are not connected to or interfere with each other.
[0035] A filter press method for producing polyaluminium chloride, comprising a filter press for producing polyaluminium chloride, is specifically divided into the following steps: S1. Pump the PAC matured slurry into the filter press, where the adjacent plate frames 3 are alternately embedded with positive and negative electrodes. The electric field formed guides the positively charged calcium particles in the slurry to move toward the negative electrode frame, forming calcium-rich shells on both sides of the negative electrode frame. S2. When the slurry pumping is about to end, the PLC sequencer starts, first controlling the electric heating plate 10 to heat the negative electrode frame, so that the temperature of the side where the filter cake contacts the plate frame 3 is increased, accelerating the evaporation of water and further reducing its water content, so that a mechanically weak layer is formed between the calcium-rich layer and the filter cake; S3. Secondly, the PLC sequencer controls the pressure control device to first inflate the diaphragms on both sides of the positive electrode frame, causing them to expand and squeeze the filter cake toward the negative electrode frame. At the same time, the expanded curved surface of the diaphragm weakens its adhesion to the filter cake, while increasing the adhesion between the calcium-rich layer and the filter cloth on the negative electrode frame. S4. Finally, the PLC sequencer controls the pressure control device to switch to air extraction, so that an instantaneous negative pressure is formed between the positive electrode frame and the diaphragm. The instantaneous contraction of the diaphragm is used to pull the filter cake back after the impact. The pulling back effect causes the calcium-rich layer and the filter cake to tend to break or directly break from the formed mechanical weak layer. S5. After the frame is opened, the main cake falls off by its own weight, and the calcium-rich layer remains on the negative electrode frame, completing the calcium salt separation of the filter cake, and then it is recovered. The recovered calcium salt is then returned to the furnace to compensate for the calcium salt in the separated clear liquid in the future and make up for the loss of basicity in the clear liquid.
[0036] The standard parts used in this embodiment can be purchased directly from the market, and the non-standard structural components recorded in the specification and drawings can also be directly processed according to existing technical common sense without any doubt. At the same time, the connection method of each component adopts the mature conventional means in the existing technology, and the machinery, parts and equipment all adopt conventional models in the existing technology, so no specific description will be given here.
[0037] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.
Claims
1. A filter press for the production of polyaluminium chloride, comprising a plurality of plate frames (3) slidably mounted on a beam (1), characterized in that: The plate frame (3) is composed of two detachable shell plates (31) on the left and right, and a cavity is provided between the two shell plates (31), and further comprises: An electrode sheet (9) is provided in the cavity, wherein the electrode sheet (9) is divided into a positive electrode and a negative electrode, and the electrode sheet (9) in the adjacent plate frame (3) is designed to have a positive and negative crossover; An electric field with an electrophoretic effect is formed in the filter cavity formed between the adjacent plates and frames (3), and the electric field drives the positively charged calcium particles in the PAC slurry to migrate; An electric heating plate (10) is arranged in the cavity, and the electric heating plate (10) is used to heat the calcium-rich layer formed by the migration of calcium particles.
2. The filter press for polyaluminium chloride production according to claim 1, wherein: Filter cloths (14) are attached and fixed to the outer walls of both sides of all the plate frames (3), and a diaphragm (13) is also fixed to the outer wall of the plate frame (3) with the positive electrode, and the diaphragm (13) is located inside the filter cloth (14) and forms a closed space between the diaphragm and the plate frame (3); The filter press further comprises an air supply pipe (15) connected to an external pressure control device, a connecting pipe (16) is connected between the air supply pipe (15) and the outer wall of the plate frame (3) with the positive electrode, and the connecting pipe (16) is connected to the cavity between the diaphragm (13) and the outer wall of the plate frame (3).
3. The filter press for polyaluminium chloride production according to claim 1, wherein: The filter press also includes hook machines (18) installed on both sides thereof via slide rails and capable of reciprocating movement. A two-dimensional moving system (19) is installed between the two hook machines (18), and the two-dimensional moving system (19) has two symmetrically designed adjusting sliders (20) that can be moved and adjusted in a plane space. Venturi tubes (21) are installed on the outer walls of the two adjusting sliders (20), and the Venturi tubes (21) are connected to an external vacuum pump. A flat suction nozzle (22) is provided at the end of the Venturi tube (21).
4. The filter press for polyaluminium chloride production according to claim 2, wherein: The cavity between the two shell plates (31) is divided into an outer ring (6) and an inner ring (7), and insulating ribs (8) are provided at intervals in the outer ring (6) and the inner ring (7). The electrode sheet (9) is embedded in the outer ring (6), and the electric heating plate (10) is embedded in the inner ring (7).
5. The filter press for polyaluminium chloride production according to claim 2, wherein: The fitting surfaces of the two shell plates (31) are respectively provided with a butt joint edge (12) and a groove capable of being engaged and embedded in the butt joint edge (12), and the butt joint edge (12) is of an asymmetrical design.
6. The filter press for polyaluminium chloride production according to claim 3, wherein: The two-dimensional moving system (19) includes a gantry fixed between the two hook machines (18), and two vertical rails are installed on the gantry via a horizontal electric slider, and the two adjustment sliders (20) are respectively slidably installed in the two vertical rails.
7. The filter press for polyaluminium chloride production according to claim 1, wherein: The filter press further comprises a drainage pipe (17), and a conduit is connected between the bottom of each plate frame (3) and the drainage pipe (17), and the conduit is used to drain the clear liquid in the filter cavity formed by the combination of the two plate frames (3).
8. The filter press for polyaluminium chloride production according to claim 2, wherein: The filter press also includes a control system, and the control system includes a PLC timer, and the PLC timer is used to control the start-up sequence of the electric heating plate (10) and the pressure control device, and first controls the electric heating plate (10) to heat, and then the pressure control device first inflates the space between the plate frame (3) and the diaphragm (13), and finally instantly converts the space between the plate frame (3) and the diaphragm (13) into exhaust, so that the internal pressure is instantaneously negative.
9. The filter press for producing polyaluminium chloride according to any one of claims 1 to 8, characterized in that: The filter press further comprises a thrust plate (2) and a pressing plate (4), and the pressing plate (4) is driven to move by a hydraulic cylinder (5) and together with the thrust plate (2) and the plate frame (3) form a filter press system.
10. A filter press method for producing polyaluminium chloride, comprising the filter press for producing polyaluminium chloride according to claim 8, characterized in that: The specific steps are as follows: S1. Pumping the PAC matured slurry into the filter press, wherein the adjacent plate frames (3) are alternately embedded with positive and negative electrodes, and utilizing the formed electric field to guide the positively charged calcium particles in the slurry to move toward the negative electrode frame, and forming a calcium-rich layer on the filter cake in the filter cavity near the negative electrode frame; S2. When the slurry pump pressure is about to end, the PLC sequencer starts, first controlling the electric heating plate (10) to heat the negative electrode frame, so that the temperature of the side where the filter cake and the plate frame (3) are in contact increases, accelerating the evaporation of water and further reducing its water content, so that a mechanically weak layer is formed between the calcium-rich layer and the filter cake; S3. Secondly, the PLC sequencer controls the pressure control device to first inflate the diaphragms (13) on both sides of the positive electrode frame, causing them to expand and squeeze the filter cake toward the negative electrode frame. At the same time, the expanded curved surface of the diaphragm (13) also weakens the adhesion between it and the filter cake, while increasing the adhesion between the calcium-rich layer and the filter cloth on the negative electrode frame. S4. Finally, the PLC sequencer controls the pressure control device to switch to air extraction, so that an instantaneous negative pressure is formed between the positive electrode frame and the diaphragm (13), and the instantaneous contraction of the diaphragm (13) is used to pull back the filter cake after the impact, and the pulling back effect is used to cause the calcium-rich layer and the filter cake to tend to break or directly break from the formed mechanical weak layer; S5. After the frame is opened, the main cake falls off by its own weight, and the calcium-rich layer remains on the negative electrode frame, completing the calcium salt separation of the filter cake, and then it is recovered. The recovered calcium salt is then returned to the furnace to compensate for the calcium salt in the separated clear liquid in the future and make up for the loss of basicity in the clear liquid.