Multi-level membrane filtration assembly and process for chemical purification

Abstract

The invention discloses a multi-level membrane filtration assembly and process for chemical purification. The assembly integrates three layers of filter elements, adopts a forward cross-flow filtration mode, does not need backwashing, and maintains stable operation of the device by regularly replacing the first layer of filter element. The invention shortens the filtration process, reduces the land occupation and equipment investment, lowers the energy consumption and maintenance cost, adjusts the operating temperature through the internal cooling system to ensure the high-flux filtration of the solvent, and is suitable for common solvents and extreme chemical environments such as strong acid, strong alkali and high salt systems.

Description

Technical Field

[0001] The invention relates to the field of filtration technology, and in particular to a multi-level membrane filtration component and process for chemical purification. Background Art

[0002] In the semiconductor manufacturing, high-end chemical analysis, biopharmaceutical and other industries, the purity of ultrapure solvents directly affects product quality and experimental results. Traditional multi-stage filtration devices have obvious shortcomings when dealing with ultrapure solvents in strong acid, strong alkali and high salt systems. Traditional multi-stage filtration devices use dead-end filtration or simple filtration methods. As the filtration proceeds, impurities accumulate on the surface of the filter medium, resulting in a rapid increase in filtration resistance and a sharp drop in filtration flux. In order to maintain the filtration effect, frequent backwashing is required, which not only consumes a lot of water resources and electricity, increases energy consumption costs, but also frequently backwashes easily cause mechanical damage to the filter membrane, shorten the service life of the membrane, and greatly increase maintenance costs. At the same time, the multi-stage filtration device has a complex structure, is connected in sequence by multiple independent filtration units, occupies a large area, has high equipment investment costs, and the chemical solution is susceptible to secondary contamination during long-distance transmission. Although some existing improved filtration technologies have solved some problems to a certain extent, they have not fundamentally broken through the limitations of traditional filtration methods.

[0003] CN118142250A discloses an electronic-grade hydrogen peroxide filtration device and filtration process, which uses a pleated filter layer to wrap a resin layer to solve the problem that the cylindrical filtration area is small, particulate impurities are easily and evenly attached to the surface, and the filter element needs to be replaced frequently, affecting the overall filtration efficiency. CN119241008A discloses a pharmaceutical wastewater treatment process and treatment device, which sequentially undergoes an electric flocculation process, an ozone catalytic oxidation process, a ceramic membrane separation process, and a reverse osmosis process to achieve the simultaneous removal of suspended matter and organic matter. CN119215666A discloses an easily disassembled ceramic membrane device for sewage treatment, which improves the convenience of maintenance and reduces maintenance costs by evenly arranging ceramic membranes inside the sewage treatment device and replacing a single damaged membrane tube. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a multi-level membrane filtration component and process for chemical purification, which is used to solve the problems of low efficiency, easy pollution, long process, high equipment investment and maintenance, and high energy consumption in traditional multi-stage filtration devices in solvent filtration, and realize high-efficiency, high-precision, and low-cost filtration of ordinary chemical solutions and chemical solutions in extreme chemical environments such as strong acids, strong alkalis, and high salt systems.

[0005] The technical solution of the present invention is as follows: a multi-level membrane filtration component for chemical purification, comprising an outer shell, a first-level filter membrane, a second-level filter membrane, a third-level filter membrane, a pressure control system, a flow control system, a guide plate, a circulating cooling system, and a supporting frame; the outer shell comprises a solvent inlet, a solvent outlet, and a purified liquid outlet; the first-level filter membrane, the second-level filter membrane, and the third-level filter membrane are arranged concentrically from the inside to the outside; the first-level filter membrane is connected to the supporting frame, the upper end cover is aligned with the solvent inlet, the lower end cover is connected to the solvent outlet, and the two ends are sealed by sealing gaskets and buckles; the second-level filter membrane and the third-level filter membrane are connected to the supporting frame, and the two ends are sealed by sealant; the pressure control system comprises a pressure sensor, a pressure regulating valve, a pressure pipeline, and a pressure controller; the pressure sensor is connected by a method The flange is connected to the outer shell, the pressure regulating valve is located at the upper end of the solvent inlet, the pressure pipeline connects the pressure sensor and the pressure regulating valve, and the pressure controller is located on the upper part of the pressure sensor; the flow control system includes a flow sensor and a flow regulating valve, the flow sensor is connected to the flow regulating valve, and the flow regulating valve is located on the side of the solvent inlet and the solvent outlet; the guide plate is arranged on the surface of the first-level filter membrane, the second-level filter membrane, and the third-level filter membrane through a snap connection; the circulating cooling system includes a spiral pipe, a temperature sensor, and a cooling pump. The spiral pipe is arranged in the first-level filter membrane and is connected to the support frame through a sealing joint. The temperature sensor is installed at the solvent outlet and the purified liquid outlet. The cooling pump is arranged outside the outer shell and is connected to the spiral pipe and the temperature sensor; the support frame is fixed to the upper and lower ends of the inner part of the outer shell by bolts.

[0006] Furthermore, the first-level filter membrane adopts a plug-in or rotary connection structure, is made of PP, PES, or PTFE, and has a pore size of 0.01-0.1 μm.

[0007] Furthermore, the second-level filter membrane is made of PVDF, PTFE, or PES, and has a pore size of 1-10 nm.

[0008] Furthermore, the third-level filter membrane is made of PVDF, PTFE, PES, and has a pore size of 1-5 nm.

[0009] Furthermore, the number of guide plates on each level of the first-level filter membrane, the second-level filter membrane, and the third-level filter membrane is 4-16.

[0010] Furthermore, the length of the guide plate is 0.6-0.8 times the spacing between each level of filtration membranes, and the angle is between 30° and 90°.

[0011] The chemical purification process of the multi-level membrane filtration assembly comprises the following steps: The solvent adjusts the feed flow rate through the flow control system. After entering from the solvent inlet, it flows to the first-level filter membrane at a suitable angle through the guide plate, and forms a purer filtrate through the micropores of the first-level filter membrane to enter the second-level filter membrane. A small part of the solvent flows along the surface of the first-level filter membrane, carrying unfiltered tiny particles, and is discharged through the solvent outlet and flows back to the feed inlet. The solvent filtrate enters the third-level filter membrane from the second-level filter membrane, and is discharged from the purified liquid outlet after being filtered by the third-level filter membrane. The pressure control system adjusts the solvent filtration pressure, and the circulating cooling system monitors and adjusts the membrane filtration temperature in real time.

[0012] Furthermore, during the forward cross-flow filtration, the flow rate of the chemical solution on the surface of the first-level filter membrane is 0.3-1m / s, the flow rate on the surface of the second-level filter membrane is 0.2-0.8m / s, and the flow rate on the surface of the third-level filter membrane is 0.1-0.6m / s. The flow rate difference between the membrane surfaces of each level ranges from 0-10%.

[0013] Furthermore, the pressure of the forward cross-flow filtration is controlled at 0.3-0.6 MPa.

[0014] Furthermore, the substance introduced into the circulating cooling system is cold air or condensed water.

[0015] Beneficial effects: The forward cross-flow filtration multi-level filter element adopted in the present invention enables the chemical solution to form a dynamic flow on the membrane surface, effectively reducing the deposition of impurities, greatly improving the filtration efficiency, reducing the direct impact and clogging of impurities on the membrane, reducing the risk of membrane damage, effectively extending the service life of each level of filtration membrane, and improving the overall reliability and stability of the equipment. Compared with traditional dead-end filtration, the filtration flux is stable and the filtration time is greatly shortened, which can meet the needs of large-scale production and experiments for rapid filtration of chemical solutions. The modular design of the first-level filtration membrane is easy to replace and does not require backwashing, avoiding the consumption of a large amount of water resources and electricity, and reducing energy consumption costs. The internal circulation cooling system of the component reduces the viscosity of the fluid by controlling the solvent temperature, thereby increasing the membrane flux and shortening the time for chemical purification. At the same time, the integrated multi-level membrane device has a compact structure, which reduces the equipment footprint and procurement costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1This is a schematic diagram of a multi-level membrane filtration assembly and process for chemical purification of the present invention, wherein: 1-outer shell 2-first level filter membrane 3-second level filter membrane 4-third level filter membrane 5-pressure control system 6-flow control system 7-guide plate 8-circulating cooling system 9-support frame 101-solvent inlet 102-solvent outlet 103-purified liquid outlet 201-upper end cover 202-lower end cover 501-pressure sensor 502-pressure regulating valve 503-pressure pipeline 504-pressure controller 601-flow sensor 602-flow regulating valve 801-spiral pipeline 802-temperature sensor 803-cooling pump.

[0017] Figure 2 This is a curve chart showing the change of filtration flux versus filtration time in chemical purification in Example 1.

[0018] Figure 3 This is a curve chart showing the change of filtration flux versus filtration time in chemical purification in Example 2.

[0019] Figure 4 This is a curve chart showing the change of chemical purification filtration flux versus filtration time in Example 3. DETAILED DESCRIPTION Example 1

[0020] In order to more intuitively and completely understand the technical solution of the present invention, a non-limiting feature description is now provided in conjunction with the accompanying drawings of the present invention as follows: like Figure 1As shown, a multi-level membrane filtration component for chemical purification includes an outer shell 1, a first-level filter membrane 2, a second-level filter membrane 3, a third-level filter membrane 4, a pressure control system 5, a flow control system 6, a guide plate 7, a circulating cooling system 8, and a support frame 9; the outer shell 1 includes a solvent inlet 101, a solvent outlet 102, and a purified liquid outlet 103, the first-level filter membrane 2, the second-level filter membrane 3 and the third-level filter membrane 4 are arranged concentrically from the inside to the outside, the first-level filter membrane 2 is connected to the support frame 9, the upper end cover 201 is aligned with the solvent inlet 101, the lower end cover 202 is connected to the solvent outlet 102, and the two ends are sealed by sealing gaskets and buckles, the second-level filter membrane 3 and the third-level filter membrane 4 are connected to the support frame 9, and the two ends are sealed by sealants; the pressure control system 5 includes a pressure sensor 501, a pressure regulating valve 502, a pressure pipeline 503, and a pressure controller 504, the pressure sensor 501 is connected to the outer shell 1 through a flange, and the pressure regulating valve 502 Located at the upper end of the solvent inlet 101, the pressure pipe 503 connects the pressure sensor 501 and the pressure regulating valve 502, and the pressure controller 504 is located at the upper part of the pressure sensor 501; the flow control system 6 includes a flow sensor 601 and a flow regulating valve 602, the flow sensor 601 is connected to the flow regulating valve 602, and the flow regulating valve 602 is located on the side of the solvent inlet 101 and the solvent outlet 102; the guide plate 7 is arranged on the surface of the first-level filter membrane 2, the second-level filter membrane 3, and the third-level filter membrane 4 through a snap connection; the circulating cooling system 8 includes a spiral pipe 801, a temperature sensor 802, and a cooling pump 803, the spiral pipe 801 is arranged in the first-level filter membrane 2, and is connected to the support frame 9 through a sealing joint, the temperature sensor 802 is installed at the solvent outlet 102 and the purified liquid outlet 103, and the cooling pump 803 is arranged outside the outer shell 1, and is connected to the spiral pipe 801 and the temperature sensor 802; the support frame 9 is fixed to the upper and lower ends of the inner part of the outer shell 1 by bolts.

[0021] The first-level filter membrane 2 adopts a plug-in connection, is made of PP, and has a pore size of 0.1 μm.

[0022] The second-level filter membrane 3 is made of PTFE and has a pore size of 10 nm.

[0023] The third-level filter membrane 4 is made of PTFE and has a pore size of 5 nm.

[0024] The number of guide plates 7 on each level of the first level filter membrane 2 , the second level filter membrane 3 , and the third level filter membrane 4 is 8.

[0025] The length of the guide plate 7 is 0.8 times the spacing between each level of filtration membranes, and the angle is 60°.

[0026] The solvent adjusts the feed flow rate through the flow control system 6, enters from the solvent inlet 11, passes through the guide plate 7 at a suitable angle to the first-level filter membrane 2, forms a purer filtrate through the micropores of the first-level filter membrane 2, and enters the second-level filter membrane 3. A small part of the solvent flows along the surface of the first-level filter membrane 2, carrying unfiltered tiny particles, and is discharged through the solvent outlet 12 to flow back to the feed port. The solvent filtrate enters the third-level filter membrane 4 from the second-level filter membrane 3, is filtered by the third-level filter membrane 4, and is discharged from the purified liquid outlet 13. The pressure control system 5 adjusts the solvent filtration pressure, and the circulating cooling system 8 monitors and adjusts the membrane filtration temperature in real time.

[0027] During forward cross-flow filtration, the flow rate of the chemical solution on the surface of the first-level filter membrane 2 is 0.5 m / s, the flow rate on the surface of the second-level filter membrane 3 is 0.48 m / s, and the flow rate on the surface of the third-level filter membrane 4 is 0.45 m / s. The flow rate difference between the membrane surfaces of each level ranges from 4% to 6.25%.

[0028] The pressure of forward cross-flow filtration was controlled at 0.5 MPa.

[0029] The material introduced into the circulating cooling system 8 is condensed water.

[0030] The curve of chemical purification filtration flux changing with filtration time is as follows Figure 2 shown.

[0031] Table 1 Comparison of forward cross-flow filtration and dead-end filtration flux

[0032] Table 2 Comparison of energy consumption between forward cross-flow filtration and dead-end filtration Filter method Backwash water consumption Electricity Forward Cross Flow 0 12.5kWh Dead-end filtration <![CDATA[0.5m 3 / h]]> 15kWh Example 2

[0033] In order to more intuitively and completely understand the technical solution of the present invention, a non-limiting feature description is now provided in conjunction with the accompanying drawings of the present invention as follows: like Figure 1As shown, a multi-level membrane filtration component for chemical purification includes an outer shell 1, a first-level filter membrane 2, a second-level filter membrane 3, a third-level filter membrane 4, a pressure control system 5, a flow control system 6, a guide plate 7, a circulating cooling system 8, and a support frame 9; the outer shell 1 includes a solvent inlet 101, a solvent outlet 102, and a purified liquid outlet 103, the first-level filter membrane 2, the second-level filter membrane 3 and the third-level filter membrane 4 are arranged concentrically from the inside to the outside, the first-level filter membrane 2 is connected to the support frame 9, the upper end cover 201 is aligned with the solvent inlet 101, the lower end cover 202 is connected to the solvent outlet 102, and the two ends are sealed by sealing gaskets and buckles, the second-level filter membrane 3 and the third-level filter membrane 4 are connected to the support frame 9, and the two ends are sealed by sealants; the pressure control system 5 includes a pressure sensor 501, a pressure regulating valve 502, a pressure pipeline 503, and a pressure controller 504, the pressure sensor 501 is connected to the outer shell 1 through a flange, and the pressure regulating valve 502 Located at the upper end of the solvent inlet 101, the pressure pipe 503 connects the pressure sensor 501 and the pressure regulating valve 502, and the pressure controller 504 is located at the upper part of the pressure sensor 501; the flow control system 6 includes a flow sensor 601 and a flow regulating valve 602, the flow sensor 601 is connected to the flow regulating valve 602, and the flow regulating valve 602 is located on the side of the solvent inlet 101 and the solvent outlet 102; the guide plate 7 is arranged on the surface of the first-level filter membrane 2, the second-level filter membrane 3, and the third-level filter membrane 4 through a snap connection; the circulating cooling system 8 includes a spiral pipe 801, a temperature sensor 802, and a cooling pump 803, the spiral pipe 801 is arranged in the first-level filter membrane 2, and is connected to the support frame 9 through a sealing joint, the temperature sensor 802 is installed at the solvent outlet 102 and the purified liquid outlet 103, and the cooling pump 803 is arranged outside the outer shell 1, and is connected to the spiral pipe 801 and the temperature sensor 802; the support frame 9 is fixed to the upper and lower ends of the inner part of the outer shell 1 by bolts.

[0034] The first-level filter membrane 2 is connected in a rotary manner, made of PES, and has a pore size of 0.1 μm.

[0035] The second-level filter membrane 3 is made of PVDF and has a pore size of 5 nm.

[0036] The third-level filter membrane 4 is made of PTFE and has a pore size of 2 nm.

[0037] The number of guide plates 7 on each level of the first level filter membrane 2 , the second level filter membrane 3 , and the third level filter membrane 4 is 6.

[0038] The length of the guide plate 7 is 0.6 times the spacing between each level of filtration membranes, and the angle is 45°.

[0039] The solvent adjusts the feed flow rate through the flow control system 6, enters from the solvent inlet 11, passes through the guide plate 7 at a suitable angle to the first-level filter membrane 2, forms a purer filtrate through the micropores of the first-level filter membrane 2, and enters the second-level filter membrane 3. A small part of the solvent flows along the surface of the first-level filter membrane 2, carrying unfiltered tiny particles, and is discharged through the solvent outlet 12 to flow back to the feed port. The solvent filtrate enters the third-level filter membrane 4 from the second-level filter membrane 3, is filtered by the third-level filter membrane 4, and is discharged from the purified liquid outlet 13. The pressure control system 5 adjusts the solvent filtration pressure, and the circulating cooling system 8 monitors and adjusts the membrane filtration temperature in real time.

[0040] During forward cross-flow filtration, the flow rate of the chemical solution on the surface of the first-level filter membrane 2 is 0.3 m / s, the flow rate on the surface of the second-level filter membrane 3 is 0.28 m / s, and the flow rate on the surface of the third-level filter membrane 4 is 0.26 m / s. The flow rate difference between the membrane surfaces of each level ranges from 6.67% to 7.14%.

[0041] The pressure of forward cross-flow filtration was controlled at 0.3 MPa.

[0042] The material introduced into the circulating cooling system 8 is condensed water.

[0043] The curve of chemical purification filtration flux changing with filtration time is as follows Figure 3 shown.

[0044] Table 3 Comparison of forward cross-flow filtration and dead-end filtration flux

[0045] Table 4 Comparison of energy consumption between forward cross-flow filtration and dead-end filtration Filter method Backwash water consumption Electricity Forward Cross Flow 0 12.5kWh Dead-end filtration <![CDATA[0.5m 3 / h]]> 15kWh Example 3

[0046] In order to more intuitively and completely understand the technical solution of the present invention, a non-limiting feature description is now provided in conjunction with the accompanying drawings of the present invention as follows: like Figure 1As shown, a multi-level membrane filtration component for chemical purification includes an outer shell 1, a first-level filter membrane 2, a second-level filter membrane 3, a third-level filter membrane 4, a pressure control system 5, a flow control system 6, a guide plate 7, a circulating cooling system 8, and a support frame 9; the outer shell 1 includes a solvent inlet 101, a solvent outlet 102, and a purified liquid outlet 103, the first-level filter membrane 2, the second-level filter membrane 3 and the third-level filter membrane 4 are arranged concentrically from the inside to the outside, the first-level filter membrane 2 is connected to the support frame 9, the upper end cover 201 is aligned with the solvent inlet 101, the lower end cover 202 is connected to the solvent outlet 102, and the two ends are sealed by sealing gaskets and buckles, the second-level filter membrane 3 and the third-level filter membrane 4 are connected to the support frame 9, and the two ends are sealed by sealants; the pressure control system 5 includes a pressure sensor 501, a pressure regulating valve 502, a pressure pipeline 503, and a pressure controller 504, the pressure sensor 501 is connected to the outer shell 1 through a flange, and the pressure regulating valve 502 Located at the upper end of the solvent inlet 101, the pressure pipe 503 connects the pressure sensor 501 and the pressure regulating valve 502, and the pressure controller 504 is located at the upper part of the pressure sensor 501; the flow control system 6 includes a flow sensor 601 and a flow regulating valve 602, the flow sensor 601 is connected to the flow regulating valve 602, and the flow regulating valve 602 is located on the side of the solvent inlet 101 and the solvent outlet 102; the guide plate 7 is arranged on the surface of the first-level filter membrane 2, the second-level filter membrane 3, and the third-level filter membrane 4 through a snap connection; the circulating cooling system 8 includes a spiral pipe 801, a temperature sensor 802, and a cooling pump 803, the spiral pipe 801 is arranged in the first-level filter membrane 2, and is connected to the support frame 9 through a sealing joint, the temperature sensor 802 is installed at the solvent outlet 102 and the purified liquid outlet 103, and the cooling pump 803 is arranged outside the outer shell 1, and is connected to the spiral pipe 801 and the temperature sensor 802; the support frame 9 is fixed to the upper and lower ends of the inner part of the outer shell 1 by bolts.

[0047] The first-stage filter membrane 2 adopts a plug-in connection, is made of PTFE, and has a pore size of 0.05 μm.

[0048] The second-level filter membrane 3 is made of PTFE and has a pore size of 10 nm.

[0049] The third-level filter membrane 4 is made of PTFE and has a pore size of 5 nm.

[0050] There are 10 guide plates 7 on each level of the first level filter membrane 2 , the second level filter membrane 3 , and the third level filter membrane 4 .

[0051] The length of the guide plate 7 is 0.7 times the spacing between each level of filtration membranes, and the angle is 30°.

[0052] The solvent adjusts the feed flow rate through the flow control system 6, enters from the solvent inlet 11, passes through the guide plate 7 at a suitable angle to the first-level filter membrane 2, forms a purer filtrate through the micropores of the first-level filter membrane 2, and enters the second-level filter membrane 3. A small part of the solvent flows along the surface of the first-level filter membrane 2, carrying unfiltered tiny particles, and is discharged through the solvent outlet 12 to flow back to the feed port. The solvent filtrate enters the third-level filter membrane 4 from the second-level filter membrane 3, is filtered by the third-level filter membrane 4, and is discharged from the purified liquid outlet 13. The pressure control system 5 adjusts the solvent filtration pressure, and the circulating cooling system 8 monitors and adjusts the membrane filtration temperature in real time.

[0053] During forward cross-flow filtration, the flow rate of the chemical solution on the surface of the first-level filter membrane 2 is 0.4 m / s, the flow rate on the surface of the second-level filter membrane 3 is 0.38 m / s, and the flow rate on the surface of the third-level filter membrane 4 is 0.36 m / s. The flow rate difference between the membrane surfaces of each level ranges from 5% to 5.26%.

[0054] The pressure of forward cross-flow filtration was controlled at 0.4 MPa.

[0055] The circulating cooling system 8 is fed with cold air.

[0056] The curve of chemical purification filtration flux changing with filtration time is as follows Figure 4 shown.

[0057] Table 5 Comparison of forward cross-flow filtration and dead-end filtration flux

[0058] Table 6 Comparison of energy consumption between forward cross-flow filtration and dead-end filtration Filter method Backwash water consumption Electricity Forward Cross Flow 0 12.5kWh Dead-end filtration <![CDATA[0.5m 3 / h]]> 15kWh

Claims

1. A multi-level membrane filtration assembly for chemical purification, characterized in that: The invention comprises an outer shell (1), a first-level filter membrane (2), a second-level filter membrane (3), a third-level filter membrane (4), a pressure control system (5), a flow control system (6), a guide plate (7), a circulating cooling system (8), and a support frame (9); the outer shell (1) comprises a solvent inlet (101), a solvent outlet (102), and a purified liquid outlet (103); the first-level filter membrane (2), the second-level filter membrane (3), and the third-level filter membrane (4) are arranged concentrically from the inside to the outside; the first-level filter membrane (2) is connected to the support frame (9); and the upper end cover (20 1) is aligned with the solvent inlet (101), the lower end cover (202) is butted with the solvent outlet (102), and the two ends are sealed by a sealing gasket and a buckle, the second-level filter membrane (3) and the third-level filter membrane (4) are connected to the support frame (9), and the two ends are sealed by a sealant; the pressure control system (5) includes a pressure sensor (501), a pressure regulating valve (502), a pressure pipeline (503), and a pressure controller (504), the pressure sensor (501) is connected to the outer shell (1) through a flange, and the pressure regulating valve (502) is located on the solvent inlet (101). The pressure pipe (503) is connected to the pressure sensor (501) and the pressure regulating valve (502), and the pressure controller (504) is located on the upper part of the pressure sensor (501); the flow control system (6) includes a flow sensor (601) and a flow regulating valve (602), the flow sensor (601) is connected to the flow regulating valve (602), and the flow regulating valve (602) is located on the side of the solvent inlet (101) and the solvent outlet (102); the guide plate (7) is arranged on the first-level filter membrane (2), the second-level filter membrane (3), and the third-level filter membrane through a snap connection. (4) surface; the circulating cooling system (8) includes a spiral pipe (801), a temperature sensor (802), and a cooling pump (803); the spiral pipe (801) is arranged in the first-level filter membrane (2) and is connected to the support frame (9) through a sealing joint; the temperature sensor (802) is installed at the solvent outlet (102) and the purified liquid outlet (103); the cooling pump (803) is arranged outside the outer shell (1) and is connected to the spiral pipe (801) and the temperature sensor (802); the support frame (9) is fixed to the upper and lower ends of the inner part of the outer shell (1) by bolts.

2. A multi-level membrane filtration assembly for chemical purification according to claim 1, characterized in that: The first-level filter membrane (2) adopts a plug-in or rotary connection structure, is made of PP, PES, or PTFE, and has a pore size of 0.01-0.1 μm.

3. A multi-level membrane filtration assembly for chemical purification according to claim 1, characterized in that: The second-level filter membrane (3) is made of PVDF, PTFE, PES, and has a pore size of 1-10 nm.

4. A multi-level membrane filtration assembly for chemical purification according to claim 1, characterized in that: The third-level filter membrane (4) is made of PVDF, PTFE, PES, and has a pore size of 1-5 nm.

5. A multi-level membrane filtration assembly for chemical purification according to claim 1, characterized in that: The number of guide plates (7) on each level of the first-level filter membrane (2), the second-level filter membrane (3), and the third-level filter membrane (4) is 4 to 16.

6. A multi-level membrane filtration assembly for chemical purification according to claim 1, characterized in that: The length of the guide plate (7) is 0.6-0.8 times the spacing between each level of filtration membranes, and the angle is between 30° and 90°.

7. A chemical purification process using a multi-level membrane filtration assembly for chemical purification according to any one of claims 1 to 6, characterized in that: The solvent is fed through a flow control system (6) to adjust the feed flow rate. After entering from the solvent inlet (11), the solvent passes through the guide plate (7) at a suitable angle to the first filter membrane (2). A purer filtrate is formed through the micropores of the first filter membrane (2) and enters the second filter membrane (3). A small portion of the solvent flows along the surface of the first filter membrane (2), carrying unfiltered tiny particles, and is discharged through the solvent outlet (12) and flows back to the feed inlet. The solvent filtrate enters the third filter membrane (4) from the second filter membrane (3), is filtered through the third filter membrane (4), and is discharged from the purified liquid outlet (13). The pressure control system (5) adjusts the solvent filtration pressure, and the circulating cooling system (8) monitors and adjusts the membrane filtration temperature in real time.

8. The chemical purification process of the multi-level membrane filtration assembly for chemical purification according to claim 7, characterized in that: During the forward cross-flow filtration, the flow rate of the chemical solution on the surface of the first-level filter membrane (2) is 0.3-1 m / s, the flow rate on the surface of the second-level filter membrane (3) is 0.2-0.8 m / s, and the flow rate on the surface of the third-level filter membrane (4) is 0.1-0.6 m / s. The flow rate difference between the surfaces of the membranes at each level ranges from 0 to 10%.

9. The chemical purification process of the multi-level membrane filtration assembly for chemical purification according to claim 7, characterized in that: The pressure of the forward cross-flow filtration is controlled at 0.3-0.6 MPa.

10. The chemical purification process of the multi-level membrane filtration assembly for chemical purification according to claim 7, characterized in that: The material introduced into the circulating cooling system (8) is cold air or condensed water.

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