An automatic slurry pre-filter switching system

Abstract

The utility model relates to the technical field of polyvinyl chloride preparation, concretely to a slurry prefilter automatic switching system, including polymerization kettle discharge tank, with the discharge port communication of polymerization kettle discharge tank's discharge pipeline, with the discharge port communication of filter unit of discharge pipeline's discharge port, with the discharge port communication of conveying pipeline of filter unit's discharge port, along material flow direction and be located on conveying pipeline's inlet tower pump, slurry heat exchanger, first pneumatic regulating valve, with the discharge port communication of stripping column and DCS control system of conveying pipeline's discharge port, still include flushing unit, be located respectively on discharge pipeline and conveying pipeline pipe section and be used for monitoring pipeline pressure difference's differential pressure transmitter, differential pressure transmitter on conveying pipeline is located in the upstream of inlet tower pump, flushing unit communicates with filter unit, in this system production, when slurry prefilter is blocked, can not stop machine flushing recovery, guarantee production continuity, promote efficiency, system automatic control each valve and inlet tower pump, reduce the labor intensity, give consideration to effect and water saving.

Description

Technical Field

[0001] This utility model relates to the field of polyvinyl chloride preparation technology, specifically to an automatic switching system for slurry pre-filters. Background Technology

[0002] When producing polyvinyl chloride (PVC) resin in a vinyl chloride plant, the slurry needs to pass through a polymerization reactor discharge trough, a slurry pre-filter, an inlet pump, and a stripping tower to remove vinyl chloride from the slurry. During the polymerization process in the polymerization reactor, large self-polymer particles are produced. These particles enter the polymerization reactor discharge trough and are then fed into the inlet filter. The large particles of self-polymer entering the slurry pre-filter clog the filter screen, preventing the PVC resin slurry from passing through the inlet filter.

[0003] A polyvinyl chloride stripping slurry recovery system disclosed in Chinese Patent No. CN213049465U, although capable of recovering finished resin and vinyl chloride from the filter, has the following shortcomings: Firstly, only a single inlet filter operates, and after clogging, the system needs to be shut down for flushing and recovery, making continuous production impossible and affecting production efficiency; secondly, it relies on manual operation of components such as the inlet recovery valve and the flushing water valve to achieve filter flushing and recovery, requiring personnel to observe and judge whether the recovery is clean through a sight glass, which is labor-intensive and the timeliness and accuracy of operation are affected by human experience, easily leading to incomplete or excessive flushing. Utility Model Content

[0004] The purpose of this invention is to provide an automatic switching system for slurry pre-filters, which solves the problems of existing systems where a single inlet filter operates and needs to be stopped for flushing and recovery after clogging, affecting efficiency; and where manual operation of valves and sight glasses is required, resulting in high labor intensity and susceptibility to experience-based issues, leading to incomplete or excessive flushing.

[0005] To achieve the above objectives, this utility model provides the following technical solution: an automatic switching system for slurry pre-filters, comprising a polymerization reactor discharge trough, a discharge pipeline connected to the discharge port of the polymerization reactor discharge trough, a filter unit connected to the discharge port of the discharge pipeline, a conveying pipeline connected to the discharge port of the filter unit, a tower pump, a slurry heat exchanger, an electromagnetic flowmeter, a first pneumatic regulating valve, a stripping tower connected to the discharge port of the conveying pipeline, and a DCS control system, sequentially arranged along the material flow direction on the conveying pipeline; further comprising a flushing unit, and differential pressure transmitters respectively installed on the discharge pipeline and the conveying pipeline for monitoring pipeline pressure differences, wherein the differential pressure transmitter on the conveying pipeline is located upstream of the tower pump; the flushing unit is connected to the filter unit; the... The filtration unit includes a first pneumatic three-way valve connected to the discharge port of the discharge pipeline, a second pneumatic three-way valve connected to the inlet port of the conveying pipeline, two first branches connected to the two outlets of the first pneumatic three-way valve, two second branches connected to the two inlets of the second pneumatic three-way valve, a second electric valve installed on each second branch pipe section, and a slurry pre-filter connected to the corresponding first branch and second branch. The outlet port of the flushing unit is connected to both first branches and both second branches. The two differential pressure transmitters, the first pneumatic three-way valve, the second pneumatic three-way valve, the two second electric valves, the tower pump, the flushing unit, the electromagnetic flowmeter, and the first pneumatic regulating valve are all electrically connected to the DCS control system.

[0006] Furthermore, the flushing unit includes a flushing water supply tank, a forward flushing pipeline connected to the outlet port of the flushing water supply tank, a second pneumatic regulating valve installed on the forward flushing pipeline section, two flushing branches connected to the outlet port of the forward flushing pipeline via a three-way valve, a first electric valve installed on each flushing branch section, two backflushing pipelines connected to the outer wall of the forward flushing pipeline and located downstream of the second pneumatic regulating valve, a third electric valve installed on the backflushing pipeline section, and a wastewater recovery and treatment unit connected to the drainage ports of both slurry pre-filters; the outlet port of the wastewater recovery and treatment unit is connected to the inlet port of the flushing water supply tank; the outlet ports of the two flushing branches are respectively connected to the outer walls of the two first branch lines, and the outlet ports of the two backflushing pipelines are respectively connected to the outer walls of the two second branch lines and located upstream of the corresponding second electric valves; the second pneumatic regulating valve, the two third electric valves, and the two first electric valves are all electrically connected to the DCS control system.

[0007] Further, the slurry pre-filter includes a filter tank, an inlet and an outlet respectively connected to the two sides of the filter tank, a drain outlet connected to the lower side of the filter tank, an installation plate inside the filter tank, a filter basket located on the upper side of the installation plate and extending downward to the lower side of the installation plate, a drain outlet connected to the center of the lower side of the filter basket, an electric push rod located on the upper side of the filter tank, a connecting rod coaxially connected to the output end of the electric push rod and extending into the filter tank, a sealing plate connected to the lower end of the connecting rod and tightly fitted to the lower side of the filter basket, and a sealing block integrally formed with the lower side of the sealing plate and adapted to the interior of the drain outlet; the inlet is located below the installation plate, and the inlet is sealed to the outlet port of the first branch through a flange; the outlet is located above the installation plate, and the outlet is sealed to the inlet port of the second branch through a flange; the electric push rod is electrically connected to the DCS control system.

[0008] Furthermore, the wastewater recycling and treatment unit includes a drain pipe that is sealed to the drain outlets of the two filter tanks via flanges, a fourth electric valve installed on each drain pipe section, a main pipe that connects to the outlet ports of the two drain pipes, a wastewater recycling tank connected to the outlet port of the main pipe, a circulation pipe connected to the outlet port of the wastewater recycling tank, and a delivery pump, a cartridge filter, and a sixth electric valve sequentially installed on the circulation pipe along the water flow direction; the outlet port of the circulation pipe is connected to the inlet port of the flushing water supply tank; the two fourth electric valves, the delivery pump, and the sixth electric valve are all electrically connected to the DCS control system.

[0009] Furthermore, each of the two sewage pipe sections is equipped with a turbidity sensor, which is located downstream of the corresponding fourth electric valve; both turbidity sensors are electrically connected to the DCS control system.

[0010] Furthermore, the outer wall of the circulation pipe is connected to a discharge pipe, which is located between the cartridge filter and the sixth electric valve, and a fifth electric valve is provided on a section of the discharge pipe; a water hardness sensor is provided on a section of the circulation pipe, which is located between the cartridge filter and the discharge pipe; both the water hardness sensor and the fifth electric valve are electrically connected to the DCS control system.

[0011] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model's automatic switching system for slurry pre-filters utilizes a two-filter configuration, one operational and one standby. Combined with the linkage control of a first pneumatic three-way valve, a second pneumatic three-way valve, and a differential pressure transmitter, the DCS control system automatically switches to the standby filter based on the differential pressure signal when the currently operating pre-filter becomes clogged. This allows for flushing and recovery of the clogged filter without shutdown, ensuring continuous production and improving efficiency. Simultaneously, the system automates the control of all pneumatic three-way valves, electric valves, pneumatic regulating valves, and the inlet pump via the DCS control system. This eliminates the need for manual operation of valves or observation of the flushing status through sight glasses, reducing the workload of personnel and controlling the flushing path, duration, and flow rate. This avoids incomplete or excessive flushing due to manual experience, balancing flushing effectiveness with water conservation. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the automatic switching system for slurry pre-filters of this utility model; Figure 2 This is a cross-sectional schematic diagram of the slurry pre-filter of this utility model.

[0013] In the diagram: 1. Polymerization reactor discharge chute; 2. Discharge pipeline; 3. First pneumatic three-way valve; 4. First branch line; 5. Slurry pre-filter; 6. Second branch line; 7. Second pneumatic three-way valve; 8. Conveying pipeline; 9. Tower inlet pump; 10. Slurry heat exchanger; 11. Electromagnetic flowmeter; 12. First pneumatic regulating valve; 13. Stripping tower; 14. Differential pressure transmitter; 15. Flushing water supply tank; 16. Second pneumatic regulating valve; 17. Forward flushing pipeline; 18. Flushing branch line; 19. First electric valve; 20. Backwashing pipeline; 21. ... 21. Electric valve; 22. Sealing block; 23. Third electric valve; 24. Sewage pipe; 25. Fourth electric valve; 26. Turbidity sensor; 27. Main pipe; 28. Sewage recovery tank; 29. ​​Circulation pipe; 30. Transfer pump; 31. Cartridge filter; 32. Water hardness sensor; 33. Discharge pipe; 34. Fifth electric valve; 35. Sixth electric valve; 36. Filter tank; 37. Inlet; 38. Outlet; 39. Mounting plate; 40. Filter basket; 41. Drainage port; 42. Electric push rod; 43. Connecting rod; 44. Sealing plate. Detailed Implementation

[0014] Please see Figure 1-2An automatic switching system for a slurry pre-filter includes a polymerization reactor discharge trough 1, a discharge pipeline 2 connected to the discharge port of the polymerization reactor discharge trough 1, a filter unit connected to the discharge port of the discharge pipeline 2, a conveying pipeline 8 connected to the discharge port of the filter unit, a tower pump 9 sequentially arranged along the material flow direction on the conveying pipeline 8, a slurry heat exchanger 10, an electromagnetic flowmeter 11, a first pneumatic regulating valve 12, a stripping tower 13 connected to the discharge port of the conveying pipeline 8, and a DCS control system. It also includes a flushing unit and differential pressure transmitters 14 respectively installed on sections of the discharge pipeline 2 and the conveying pipeline 8 for monitoring pipeline pressure differences. The differential pressure transmitter 14 on the conveying pipeline 8 is located upstream of the tower pump 9. The flushing unit is connected to the filter unit. The filter unit includes a filter unit connected to the discharge pipeline 2. The system includes a first pneumatic three-way valve 3 connected to the material port, a second pneumatic three-way valve 7 connected to the inlet port of the conveying pipeline 8, two first branch lines 4 connected to the two outlets of the first pneumatic three-way valve 3, two second branch lines 6 connected to the two inlets of the second pneumatic three-way valve 7, a second electric valve 21 installed on each second branch line 6, and a slurry pre-filter 5 connected to the corresponding first branch line 4 and second branch line 6; the outlet port of the flushing unit is connected to both first branch lines 4 and both second branch lines 6; two differential pressure transmitters 14, the first pneumatic three-way valve 3, the second pneumatic three-way valve 7, the two second electric valves 21, the tower pump 9, the flushing unit, the electromagnetic flowmeter 11, and the first pneumatic regulating valve 12 are all electrically connected to the DCS control system.

[0015] This application further proposes that the flushing unit includes a flushing water supply tank 15, a forward flushing pipeline 17 connected to the outlet port of the flushing water supply tank 15 via a flange seal, a second pneumatic regulating valve 16 fixedly installed on a section of the forward flushing pipeline 17 via a flange, two flushing branches 18 connected to the outlet port of the forward flushing pipeline 17 via a three-way valve, a first electric valve 19 fixedly installed on a section of each flushing branch 18 via a flange, two backflushing pipelines 20 connected to the outer wall of the forward flushing pipeline 17 and located downstream of the second pneumatic regulating valve 16, and a third electric valve 19 fixedly installed on a section of the backflushing pipeline 20 via a flange. The system includes a control valve 23 and a wastewater recovery and treatment unit connected to the drain ports (sewage outlets) of the two slurry pre-filters 5; the outlet port of the wastewater recovery and treatment unit is connected to the inlet port of the flushing water supply tank 15; the outlet ports of the two flushing branches 18 are respectively connected to the outer walls of the two first branches 4 by welding or flange sealing, and the outlet ports of the two backwashing pipelines 20 are respectively connected to the outer walls of the two second branches 6 by welding or flange sealing and are located upstream of the corresponding second electric valve 21; the second pneumatic regulating valve 16, the two third electric valves 23, and the two first electric valves 19 are all electrically connected to the DCS control system.

[0016] Specifically, the forward flushing pipe 17 cooperates with the flushing branch 18 to inject flushing water from the feed side (first branch 4) of the slurry pre-filter 5, which forward strips impurities from the surface of the filter basket 40. The backwashing pipe 20 injects flushing water from the discharge side (second branch 6), which reverses the impact on the stubborn impurities remaining in the mesh. The bidirectional flushing improves the cleaning effect and avoids impurity residue affecting the subsequent filtration accuracy. The second pneumatic regulating valve 16 can adjust the total flow rate of the flushing water. The wastewater recycling and treatment unit and the flushing water supply tank 15 form a closed loop, so that the flushing wastewater can be reused after purification, reducing the consumption of fresh water resources.

[0017] This application further proposes that the slurry pre-filter 5 includes a filter tank 36, an inlet 37 and an outlet 38 respectively connected to the two sides of the filter tank 36, a drain port connected to the lower side of the filter tank 36, a mounting plate 39 fixed inside the filter tank 36 by welding, a filter basket 40 installed on the upper side of the mounting plate 39 and extending downward to the lower part of the mounting plate 39, a drain port 41 connected to the center of the lower side of the filter basket 40, an electric push rod 42 installed on the upper side of the filter tank 36, and a component coaxially fixedly installed with the output end of the electric push rod 42 and extending to the filter tank 36. The filter basket 40 has an internal connecting rod 43, a sealing plate 44 that is bolted to the lower end of the connecting rod 43 and fits tightly against the lower side of the filter basket 40, and a sealing block 22 that is integrally formed with the lower side of the sealing plate 44 and fits the interior of the drain port 41; the feed inlet 37 is located below the mounting plate 39 and is sealed to the discharge port of the first branch 4 through a flange; the discharge port 38 is located above the mounting plate 39 and is sealed to the feed port of the second branch 6 through a flange; the electric push rod 42 is electrically connected to the DCS control system.

[0018] Specifically, the filter tank 36 is divided into upper and lower chambers by the mounting plate 39; the filter basket 40 passes through the mounting plate 39 from top to bottom, so that after the slurry enters from the inlet 37, it must pass through the filter basket 40 to be discharged from the outlet 38, effectively intercepting the self-polymer impurities in the polyvinyl chloride slurry; the electric push rod 42, the sealing plate 44, and the sealing block 22 can be automatically controlled by the DCS control system to open and close the drain port 41, so that the impurities remaining in the filter basket 40 can be discharged during the flushing operation, avoiding the accumulation of impurities that affect the filtration effect.

[0019] This application further proposes that the wastewater recycling and treatment unit includes a sewage pipe 24 that is respectively connected to the sewage outlets of two filter tanks 36 via flange sealing, a fourth electric valve 25 fixedly installed on each sewage pipe 24 section via flange, a main pipe 27 that merges with the outlet ports of the two sewage pipes 24 and is connected to them via flange sealing, a wastewater recycling tank 28 that is connected to the outlet port of the main pipe 27 via flange sealing, a circulation pipe 29 that is fixedly connected to the outlet port of the wastewater recycling tank 28, and a transfer pump 30, a cartridge filter 31, and a sixth electric valve 35 that are sequentially fixedly installed on the circulation pipe 29 via flange or threaded interface along the water flow direction; the outlet port of the circulation pipe 29 is connected to the inlet port of the flushing water supply tank 15 via flange sealing; the two fourth electric valves 25, the transfer pump 30, and the sixth electric valve 35 are all electrically connected to the DCS control system.

[0020] Specifically, the cartridge filter 31 can remove pollutants such as self-polymerized impurities and suspended solids from wastewater, ensuring the cleanliness of the circulating flushing water and preventing pollutants from re-entering the slurry pre-filter 5, affecting the filtration effect or causing pipeline blockage.

[0021] This application further proposes that turbidity sensors 26 are fixedly installed on the pipe sections of the two sewage pipes 24 through threaded interfaces or flanges. The detection probe of the turbidity sensor 26 extends into the inside of the sewage pipe 24 and is in direct contact with the flushing sewage flowing in the pipe. The turbidity sensor 26 is located downstream of the corresponding fourth electric valve 25. Both turbidity sensors 26 are electrically connected to the DCS control system.

[0022] Specifically, by using turbidity sensor 26 and linking it with the DCS control system, the turbidity changes of each flushing wastewater can be monitored in real time, directly reflecting the flushing effect of the slurry pre-filter 5. When turbidity sensor 26 detects that the wastewater turbidity is lower than the preset threshold, the DCS control system can automatically determine that the slurry pre-filter 5 has met the flushing standard and promptly close the relevant valves of the flushing unit to stop flushing, avoiding water waste caused by excessive flushing. At the same time, if the turbidity data of a certain channel is higher than the threshold for a long time, it can indicate that the slurry pre-filter 5 may have incomplete cleaning or severe clogging of the filter basket 40, which is convenient for maintenance personnel to conduct targeted troubleshooting.

[0023] This application further proposes that the outer wall of the circulation pipe 29 is connected to the discharge pipe 33 by welding. The discharge pipe 33 is located between the cartridge filter 31 and the sixth electric valve 35, and the fifth electric valve 34 is fixedly installed on the pipe section of the discharge pipe 33 by flange sealing. A water hardness sensor 32 is fixed on the pipe section of the circulation pipe 29 by threaded interface. The detection probe of the water hardness sensor 32 extends into the interior of the circulation pipe 29 and is in direct contact with the purified sewage flowing in the pipe. The water hardness sensor 32 is located between the cartridge filter 31 and the discharge pipe 33. Both the water hardness sensor 32 and the fifth electric valve 34 are electrically connected to the DCS control system.

[0024] Specifically, the linkage design of the water hardness sensor 32, the fifth electric valve 34, and the DCS control system can monitor the hardness index of the wastewater after purification by the core filter 31 in real time, preventing high-hardness wastewater from flowing back to the flushing water supply tank 15 for recycling; when the water hardness sensor 32 detects that the hardness of the wastewater exceeds the preset threshold, the DCS control system can respond quickly and control the fifth electric valve 34 to open automatically, so that the substandard wastewater can be discharged in time through the discharge pipe 33.

[0025] Working process and principle: When the system is running, the PVC slurry in the discharge tank 1 of the polymerization reactor is transported to the filtration unit through the discharge pipeline 2. The first pneumatic three-way valve 3 and the second pneumatic three-way valve 7 work together to ensure that the slurry only passes through the first pneumatic three-way valve 3, one of the first branch lines 4, one slurry pre-filter 5, the second branch line 6, and the second pneumatic three-way valve 7 (the other is in standby or flushing state). The filtered slurry passes through the conveying pipeline 8 in sequence through the tower pump 9, the slurry heat exchanger 10, the electromagnetic flowmeter 11, and the first pneumatic regulating valve 12 before entering the stripping tower 13 to complete the stripping process.

[0026] During the process, the differential pressure transmitter 14 on the discharge pipeline 2 and the conveying pipeline 8 monitors the pipeline pressure difference in real time. When the pressure difference exceeds the preset threshold, the DCS control system determines that the currently working slurry pre-filter 5 is blocked, and then controls the first pneumatic three-way valve 3 and the second pneumatic three-way valve 7 to switch the passage, so that the standby slurry pre-filter 5 can be put into operation. At the same time, the flushing unit is started to clean the blocked filter.

[0027] When the rinsing unit is working, the rinsing water from the rinsing water supply tank 15 enters the first branch 4 of the pre-filter 5 for the slurry to be cleaned via the forward rinsing pipe 17, the second pneumatic regulating valve 16, the rinsing branch 18, and the first electric valve 19, thus achieving forward rinsing of impurities attached to the outer wall of the filter basket 40. The rinsing wastewater flows into the drain pipe 24 through the drain outlet of the filter tank 36, and then sequentially enters the wastewater recovery tank 28 through the fourth electric valve 25 and the main pipe 27. Subsequently, it is transported by the transfer pump 30 to the cartridge filter 31 for purification. After purification, the water quality is detected by the water hardness sensor 32. If it meets the recycling standard, it is returned to the rinsing water supply tank 15 for reuse through the sixth electric valve 35. If the water quality does not meet the standard, it is discharged from the system through the discharge pipe 33 and the fifth electric valve 34. After forward flushing is completed, the DCS control system closes the first electric valve 19 and simultaneously opens the two third electric valves 23. The flushing water enters the second branch 6 through the backwashing pipeline 20 and the third electric valves 23 to perform backwashing on the slurry pre-filter 5, further removing stubborn impurities attached to the outer wall of the filter basket 40. The discharge port 41 of the slurry pre-filter 5 is controlled by an opening and closing mechanism consisting of an electric push rod 42, a connecting rod 43, a sealing plate 44, and a sealing block 22. When it is necessary to completely drain the impurities inside the filter basket 40, the DCS control system controls the electric push rod 42 to drive the connecting rod 43 to move the sealing plate 44 and the sealing block 22 upward, opening the discharge port 41. After the internal impurities are discharged through the discharge port 41, they flow together with the sewage generated by backwashing through the drain port into the corresponding drain pipe 24, and finally into the main pipe 27. In addition, the turbidity sensor 26 on the sewage pipe 24 monitors the turbidity of the sewage in real time. When the turbidity is detected to be lower than the preset threshold, the DCS control system automatically determines that the flushing meets the standard and then closes the second pneumatic regulating valve 16 to terminate the flushing operation.

[0028] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An automatic switching system for a slurry pre-filter, comprising a polymerization reactor discharge trough (1), a discharge pipeline (2) connected to the discharge port of the polymerization reactor discharge trough (1), a filter unit connected to the discharge port of the discharge pipeline (2), a conveying pipeline (8) connected to the discharge port of the filter unit, a tower pump (9) sequentially arranged along the material flow direction on the conveying pipeline (8), a slurry heat exchanger (10), an electromagnetic flowmeter (11), a first pneumatic regulating valve (12), a stripping tower (13) connected to the discharge port of the conveying pipeline (8), and a DCS control system, characterized in that, It also includes a flushing unit and differential pressure transmitters (14) installed on the discharge pipeline (2) and the conveying pipeline (8) respectively for monitoring the pipeline pressure difference. The differential pressure transmitter (14) on the conveying pipeline (8) is located upstream of the tower pump (9). The flushing unit is connected to the filtration unit. The filtration unit includes a first pneumatic three-way valve (3) connected to the discharge port of the discharge pipeline (2), a second pneumatic three-way valve (7) connected to the inlet port of the conveying pipeline (8), two first branches (4) connected to the two outlets of the first pneumatic three-way valve (3), two second branches (6) connected to the two inlets of the second pneumatic three-way valve (7), a second electric valve (21) provided on each second branch (6) pipe section, and a slurry pre-filter (5) connected to the corresponding first branch (4) and second branch (6); the water outlet of the rinsing unit is connected to both first branches (4) and both second branches (6); The two differential pressure transmitters (14), the first pneumatic three-way valve (3), the second pneumatic three-way valve (7), the two second electric valves (21), the tower pump (9), the flushing unit, the electromagnetic flowmeter (11) and the first pneumatic regulating valve (12) are all electrically connected to the DCS control system.

2. The automatic switching system for slurry pre-filters according to claim 1, characterized in that, The flushing unit includes a flushing water supply tank (15), a forward flushing pipeline (17) connected to the outlet port of the flushing water supply tank (15), a second pneumatic regulating valve (16) installed on the forward flushing pipeline (17), two flushing branches (18) connected to the outlet port of the forward flushing pipeline (17) via a three-way valve, a first electric valve (19) installed on each flushing branch (18), two backflushing pipelines (20) connected to the outer wall of the forward flushing pipeline (17) and located downstream of the second pneumatic regulating valve (16), and a third electric valve (23) installed on the backflushing pipeline (20). The wastewater recycling unit is connected to the drainage ports of the two slurry pre-filters (5); the outlet port of the wastewater recycling unit is connected to the inlet port of the flushing water supply tank (15); the outlet ports of the two flushing branches (18) are respectively connected to the outer walls of the two first branches (4), and the outlet ports of the two backwashing pipelines (20) are respectively connected to the outer walls of the two second branches (6) and located upstream of the corresponding second electric valves (21); the second pneumatic regulating valve (16), the two third electric valves (23), and the two first electric valves (19) are all electrically connected to the DCS control system.

3. The automatic switching system for slurry pre-filters according to claim 2, characterized in that, The slurry pre-filter (5) includes a filter tank (36), an inlet (37) and an outlet (38) respectively connected to the two sides of the filter tank (36), a drain outlet connected to the lower side of the filter tank (36), an mounting plate (39) located inside the filter tank (36), a filter basket (40) located on the upper side of the mounting plate (39) and extending downward to the lower side of the mounting plate (39), a drain outlet (41) connected to the center of the lower side of the filter basket (40), an electric push rod (42) located on the upper side of the filter tank (36), and a connecting rod (43) coaxially connected to the output end of the electric push rod (42) and extending into the interior of the filter tank (36). The filter basket (40) is connected to the lower end of the connecting rod (43) and is tightly fitted to the lower side of the filter basket (40). The filter basket (40) is integrally formed with the lower side of the sealing plate (44) and is adapted to the interior of the drain port (41). The feed port (37) is located below the mounting plate (39) and the feed port (37) is connected to the discharge port of the first branch (4) through a flange seal. The discharge port (38) is located above the mounting plate (39) and the discharge port (38) is connected to the feed port of the second branch (6) through a flange seal. The electric push rod (42) is electrically connected to the DCS control system.

4. The automatic switching system for slurry pre-filters according to claim 3, characterized in that, The wastewater recycling unit includes a drain pipe (24) that is connected to the drain outlets of two filter tanks (36) via flange seals, a fourth electric valve (25) installed on each drain pipe (24) section, a main pipe (27) that is connected to the outlet ports of the two drain pipes (24), a wastewater recycling tank (28) connected to the outlet port of the main pipe (27), a circulation pipe (29) connected to the outlet port of the wastewater recycling tank (28), and a delivery pump (30), a cartridge filter (31), and a sixth electric valve (35) sequentially installed on the circulation pipe (29) along the water flow direction; the outlet port of the circulation pipe (29) is connected to the inlet port of the flushing water supply tank (15); the two fourth electric valves (25), the delivery pump (30), and the sixth electric valve (35) are all electrically connected to the DCS control system.

5. The automatic switching system for slurry pre-filters according to claim 4, characterized in that, Turbidity sensors (26) are provided on the pipe sections of both sewage pipes (24), and the turbidity sensors (26) are located downstream of the corresponding fourth electric valve (25); both turbidity sensors (26) are electrically connected to the DCS control system.

6. The automatic switching system for slurry pre-filters according to claim 4, characterized in that, The outer wall of the circulation pipe (29) is connected to the discharge pipe (33), which is located between the core filter (31) and the sixth electric valve (35), and a fifth electric valve (34) is provided on the pipe section of the discharge pipe (33); a water hardness sensor (32) is provided on the pipe section of the circulation pipe (29), which is located between the core filter (31) and the discharge pipe (33); the water hardness sensor (32) and the fifth electric valve (34) are both electrically connected to the DCS control system.

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