Method for cleaning a precision filter, cleaning system and use

Abstract

This invention discloses a cleaning method, cleaning system, and application for precision filters. The cleaning method includes the following steps: coarsely washing the emptied precision filter with an organic solvent; washing the coarsely washed precision filter with water to remove the organic solvent; after washing, draining the wash water from the precision filter to fill it with water, then heating to perform deep hydrolysis treatment on the gel impurities adhering to the precision filter; after the deep hydrolysis treatment is completed, draining the decomposition liquid from the precision filter; washing with water, and drying to complete the cleaning of the precision filter. This invention's cleaning method uses water for deep decomposition treatment to replace the existing alkaline washing process, achieving efficient decomposition of GPAN, with good cleaning effect, low solid waste generation, and low corrosivity. This invention further improves the water-based deep decomposition treatment process, proposing a reflux self-circulation deep decomposition treatment process and a forced circulation deep decomposition treatment process to further improve the cleaning effect.

Description

Technical Field

[0001] This invention relates to the technical field of filter cleaning, and more specifically, to cleaning methods, cleaning systems, and applications for precision filters. Background Technology

[0002] Filtration of the spinning solution is crucial in carbon fiber production. Impurities in the spinning solution can cause fiber breakage during spinning and oxidation / carbonization processes, affecting production stability and carbon fiber performance. The industry typically uses precision filters to remove most impurities from the spinning solution. As impurities accumulate within the filter element, the filtration pressure differential increases, and the precision filter's ability to retain elastic impurities such as gels deteriorates. Therefore, when the operating pressure differential of the precision filter reaches the design threshold, the system must be shut down and the filter element replaced. Due to the high cost of filter elements, cleaning and reuse are generally considered.

[0003] The main impurities in spinning solutions are polyacrylonitrile gel microparticles (GPANs), primarily low-crosslinked aggregates of polyacrylonitrile. Common solvents such as dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and dimethylacetamide (DMAc) have poor dissolving effects on GPANs, generally only causing swelling. Common methods include ultrasonic-enhanced solvent immersion or circulating cleaning. The principle is that under the action of ultrasound or other external forces, the GPANs further swell and break down. When the size of the fragments is smaller than the pores of the filter media, they are carried away by the fluid; essentially, it is a physical process. However, as the size of the GPANs decreases, the required energy for fragmentation increases. Furthermore, the density distribution of external energy input on the filter media has a significant impact on the cleaning effect; for filter media with complex structures, it is generally difficult to effectively remove deep-seated GPANs.

[0004] To thoroughly clean filter elements, it is usually necessary to use chemical methods to decompose GPAN and to precipitate the polyacrylonitrile (PAN) solids remaining in the pores of the filter media during water washing. Chinese Patent Application No. 201910317228.6 discloses a complex method for cleaning disc precision filters. The method involves sequentially performing disassembly and solvent washing, reassembly and solvent washing, water washing, a second disassembly followed by 30% NaOH or KOH alkaline washing, water washing, drying, inspection, and reassembly. This method requires disassembling and reassembling the filter discs twice.

[0005] Chinese patent application number 202111349727.7 discloses another cleaning method for disc precision filters. This method includes solvent washing with bubble agitation, ultrasonic water washing, ultrasonic NaHCO3 alkaline washing, and water washing, followed by drying, testing, and assembly. While the method introduces bubbling during solvent washing, which increases local disturbance and enhances the cleaning effect to some extent, it also generates a large amount of solvent-containing organic vapor. To avoid using strong alkali, NaHCO3 is used for chemical treatment. However, the inventors found that below 100°C, although the alkaline solution has a significant decomposition effect on PAN, its decomposition effect on GPAN is not ideal. According to the "Corrosion Data and Material Selection Handbook," alkaline solutions at 100°C are corrosive to stainless steel and cannot be used for extended periods.

[0006] Furthermore, existing technologies all require multiple disassemblies and reassemblies of the precision filter, and necessitate the use of specialized ultrasonic auxiliary equipment tailored to the shape of the filter element. This process is complex, time-consuming, labor-intensive, and generates a large amount of waste. Therefore, to address the problems of difficult cleaning of carbon fiber spinning solution precision filters, the complexity of existing cleaning methods, high labor intensity, large amounts of waste, and easy corrosion of metal filter media, a new cleaning method is needed. Summary of the Invention

[0007] To address the problems in existing technologies, this invention proposes a cleaning method, system, and application for precision filters. The invention presents a novel cleaning method that uses water for deep decomposition treatment to replace alkaline washing processes such as NaOH and NaHCO3. This method achieves efficient decomposition of GPAN, provides excellent cleaning results, generates less solid waste, and has minimal corrosiveness to the filter media. Furthermore, this invention improves the water-based deep decomposition treatment process by proposing a reflux self-circulation deep decomposition treatment process and a forced circulation deep decomposition treatment process, which can further enhance the cleaning effect.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] One of the objectives of this invention is to provide a method for cleaning a precision filter, comprising the following steps: first, cleaning the precision filter after slurry discharge with organic solvents, then washing it with water, then performing deep hydrolysis treatment with water, then optionally washing it with water again, and finally drying it to complete the cleaning process.

[0010] In the cleaning method for the precision filter described in this invention, preferably,

[0011] The cleaning method for the precision filter includes the following steps:

[0012] (1) Use organic solvents to coarsely wash the empty precision filter;

[0013] (2) Wash the precision filter after coarse washing with water to remove organic solvents;

[0014] (3) After washing, drain the washing water in the precision filter and replace it with fresh water; or, retain the washing water from the last washing in step (2); after filling the precision filter with water, heat it to perform deep hydrolysis treatment on the gel impurities attached to the precision filter.

[0015] (4) After the deep hydrolysis treatment is completed, drain the decomposition liquid in the precision filter; optionally wash the precision filter with water and dry it to complete the cleaning of the precision filter.

[0016] In the cleaning method for the precision filter described in this invention, preferably,

[0017] In step (1),

[0018] The precision filter is a precision filter for filtering spinning solution; preferably, it is a precision filter for filtering carbon fiber spinning solution; and / or,

[0019] Before coarse washing, pressurization is used to purge the slurry from the precision filter and its pipelines; preferably, protective gas is injected into the precision filter to create a pressurized environment; and / or,

[0020] Before the organic solvent enters the precision filter, the precision filter is first evacuated, and then the organic solvent is injected into the precision filter.

[0021] In this invention, the specific forms of the filter elements in the precision filter include, but are not limited to, metal mesh wound filter elements, metal plate mesh sintered filter elements, metal felt sintered filter elements, metal powder sintered filter elements, wedge-shaped metal mesh filter elements, metal plate mesh sintered filter sheets, metal felt sintered filter sheets, metal powder sintered filter plates, ceramic membranes, etc.

[0022] In the cleaning method for the precision filter described in this invention, preferably,

[0023] In step (1),

[0024] The organic solvent is selected from polar organic solvents; preferably, the polar organic solvent is selected from at least one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and ethylene carbonate; and / or,

[0025] The temperature for rough washing is below 120°C, preferably 25–120°C, more preferably 65–90°C; and / or,

[0026] During the rough cleaning, an organic solvent is used for circulating cleaning, and the direction of solvent circulation is the same as the filtration direction of the precision filter;

[0027] Preferably, when the solid content of impurities in the organic solvent used for cyclic cleaning is greater than 5%, the circulation is stopped, the organic solvent in the precision filter is discharged and replaced with fresh organic solvent, or a portion of the organic solvent in the precision filter is replaced with fresh organic solvent before cyclic cleaning is performed.

[0028] Further preferably, the organic solvent to be circulated for cleaning does not show a significant increase in the impurity solid content, and the impurity solid content in the organic solvent to be circulated for cleaning is below 5%, at which point the organic solvent circulation cleaning is stopped; even further preferably, the organic solvent circulation cleaning is stopped, and ...

[0029] Most preferably, the cyclic cleaning time is 1 to 24 hours, more preferably 2 to 8 hours.

[0030] Circulation cleaning should be understood as the solvent continuously circulating within the filter, while impurities adhering to the filter are continuously dissolved into the solvent. Therefore, the solid content of the cleaning solution gradually increases. After a certain period of circulation, the impurities in the filter are no longer significantly dissolved, and the circulation cleaning reaches its limit. At this point, if the impurity content in the cleaning solution is too high, it is necessary to open the fresh solvent valve and the cleaning solution discharge valve to completely or partially replace the cleaning solvent. After replacement, the solution should be circulated again for a certain period of time to achieve the rough cleaning target.

[0031] In the cleaning method for the precision filter described in this invention, preferably,

[0032] Step (2), during water washing, the precision filter is cleaned by circulating water;

[0033] Preferably, during the circulating cleaning process, when the organic solvent content in the circulating cleaning water is greater than 10%, the circulation is stopped, all the water in the precision filter is discharged and replaced with fresh water, and then the circulating cleaning is performed again; or, during the circulating cleaning process, the cleaning water is discharged while fresh water is injected; that is, after the water of the present invention is circulated and cleaned once, the water is discharged, then new water is added, the circulation is repeated, and then the water is drained; or the cleaning water can be discharged while new water is added.

[0034] More preferably, the organic solvent content in the water to be circulated for cleaning does not increase significantly, and the organic solvent content in the circulating cleaning water is below 10%, at which point the water circulation cleaning is stopped; even more preferably, the organic solvent content in the water to be circulated for cleaning does not increase significantly, and the cleaning solvent content in the circulating cleaning water is below 1%, at which point the water circulation cleaning is stopped.

[0035] Most preferably, during the circulating cleaning process, the temperature of the circulating water is 0–100°C, more preferably 60–80°C.

[0036] In the cleaning method for the precision filter described in this invention, preferably,

[0037] Step (3),

[0038] The temperature for deep decomposition treatment is 150–350℃, preferably 200–300℃, and more preferably 240–280℃; and / or,

[0039] The deep decomposition processing time is 0.1–24 h, preferably 0.25–12 h, and more preferably 0.5–8 h.

[0040] In the cleaning method for the precision filter described in this invention, preferably,

[0041] Step (3), the deep decomposition processing method is selected from at least one of the following methods:

[0042] Method 1:

[0043] During the deep decomposition process, the precision filter is sealed. After the deep decomposition process is completed, the precision filter is cooled to room temperature and pressure, and the decomposition liquid inside the precision filter is drained.

[0044] Method 2: The precision filter is closed, but the decomposition water during the deep decomposition treatment can overflow from the precision filter into the hydrolysis product tank. The hydrolysis product tank is pre-stored with water and is under heating conditions. The decomposition water sent into the hydrolysis product tank escapes partially or completely in the form of steam. The escaped steam condenses to form condensate, which is then used as makeup water to replenish the precision filter for deep decomposition treatment, forming a reflux self-circulation.

[0045] Method 3: The precision filter is closed, but the decomposed water during the deep decomposition treatment can be discharged from the precision filter and sent to the flash evaporator after depressurization. The water sent to the flash evaporator partially or completely escapes in the form of steam. The escaped steam is pressurized and used as a heat source to exchange heat with the pressurized water from the water tank. The steam after heat exchange is condensed and used as makeup water to replenish the water tank. The pressurized water after heat exchange is then fed into the precision filter for deep decomposition treatment, forming a forced circulation.

[0046] In this invention, the self-circulating system entering the hydrolysis product tank is a connected system with equal pressure, and the circulation flow rate is controlled by the heat flux during evaporation and condensation. In the hydrolysis product tank, decomposed water undergoes impurity precipitation, and the water escapes as steam. After condensation, it is used as makeup water to replenish the precision filter for further decomposition treatment, forming a reflux self-circulation. In forced circulation, the steam exiting the flash evaporator is used to heat water introduced from the water tank by a high-pressure pump. The water introduced from the water tank, after being pressurized by the high-pressure pump and heated by the steam from the flash evaporator, is then replenished into the precision filter.

[0047] Impurities in precision filters that cannot be dissolved by solvents are generally attached to the pores of the filter element. During static, closed-loop hydrolysis, these impurities can only be removed after complete hydrolysis, and they typically only diffuse into the main water stream. When there is circulating flow, convective mass transfer helps the hydrolysis products dissolve in the water, and impurities smaller than the pore size can be carried away by the main flow, which can improve the cleaning effect to some extent. Compared with reflux self-circulation, forced circulation can increase the circulation volume during deep decomposition, thereby accelerating the cleaning process.

[0048] In the cleaning method for the precision filter described in this invention, preferably,

[0049] Step (4): Wash with water until there are no hydrolysates in the washing water; and / or, dry by vacuum drying; In this invention, vacuum does not affect cleaning, the purpose of vacuum is to accelerate drying and accelerate the discharge of protective gas when the precision filter is put into use after cleaning.

[0050] In steps (2) and (4), when water is used for rinsing, the water used is independently selected from at least one of domestic water and desalinated water, preferably desalinated water; and / or,

[0051] In step (1), when the precision filter is emptied, the discharged slurry is collected for later use; and / or,

[0052] In step (2), the washing water is collected for later use; and / or,

[0053] In step (4), after the deep hydrolysis treatment is completed, the decomposition liquid discharged from the precision filter is collected and treated.

[0054] A second objective of this invention is to provide a cleaning system for a precision filter, the cleaning system comprising a feeding unit, a precision filter, and a discharging unit;

[0055] The feeding unit is connected to the precision filter and feeds material into the precision filter to clean it; after cleaning, the material in the precision filter is discharged through the discharge unit; a heating device is also provided on the outside of the precision filter.

[0056] The feeding unit feeds organic solvents or water;

[0057] The cleaning method described in any one of the objectives of this invention preferably uses the cleaning system to clean the precision filter.

[0058] In the cleaning system for the precision filter described in this invention, preferably,

[0059] The feeding unit includes an organic solvent feeding pipe and a water feeding pipe; preferably,

[0060] The feeding unit also includes a circulating pump, an organic solvent circulating pipeline, and a water circulating pipeline;

[0061] The organic solvent feed pipe, circulation pump, precision filter, and organic solvent circulation pipe are connected in sequence to form an organic solvent circulation cleaning loop;

[0062] The water inlet pipe, circulating pump, precision filter, and water circulation pipe are connected in sequence to form a water circulation cleaning loop.

[0063] In the cleaning system for the precision filter described in this invention, preferably,

[0064] The cleaning system also includes an air intake unit and / or a vacuum unit;

[0065] The vacuum unit is connected to the precision filter before the feeding unit feeds the material, in order to create a negative pressure environment inside the precision filter.

[0066] The intake unit is connected to the precision filter before the material is discharged from the precision filter, in order to create a high-pressure environment inside the precision filter.

[0067] In the cleaning system for the precision filter described in this invention, preferably,

[0068] The cleaning system further includes a deep hydrolysis circulation treatment unit; the deep hydrolysis circulation treatment unit is selected from either a reflux self-circulation unit or a forced circulation unit.

[0069] The reflux self-circulation unit includes a hydrolysis product tank and a condenser; the discharge end of the precision filter, the hydrolysis product tank, the condenser, and the feed end of the precision filter are connected in sequence through pipelines to form a circulation loop;

[0070] The forced circulation unit includes a pressure reducing valve, a flash evaporator, a steam compressor, a heat exchanger, a pressurized circulation pump, a water tank, and a condenser. The discharge end of the precision filter, the pressure reducing valve, the flash evaporator, the steam compressor, the heat medium pipe of the heat exchanger, the condenser, and the feed end of the water tank are connected in sequence through pipelines. The discharge end of the water tank, the pressurized circulation pump, the heat exchange tube of the heat exchanger, and the feed end of the precision filter are connected in sequence through pipelines, forming a forced circulation loop.

[0071] A third objective of this invention is to provide an application of the cleaning method described in any one of the objectives of this invention or the cleaning system described in any one of the objectives of this invention in the cleaning of precision filters, preferably in the cleaning of precision filters used for filtering spinning solutions.

[0072] This invention first drains the slurry from the precision filter that has reached the switching threshold, then cleans it with organic solvents, followed by water washing, and then deep hydrolysis treatment. The filter is then washed again with water and dried to complete the cleaning process. The organic solvents and cleaning water are sent to a solvent recovery system after cleaning, and the decomposed liquid from the deep hydrolysis treatment is sent to a drying and recovery system. Compared to existing cleaning methods, this effectively reduces the amount of waste generated.

[0073] The specific steps of the present invention are as follows:

[0074] (1) Switching the raw material precision filter to standby and discharging slurry

[0075] When the operating differential pressure of the precision filter reaches the specified threshold, the standby precision filter is switched on. The residual slurry in the precision filter tank, filter element assembly, and connected pipelines to be cleaned is discharged into the intermediate slurry return tank through the air inlet and slurry outlet on the precision filter. The material in the intermediate slurry return tank is then degassed and sent to the material inlet of the standby precision filter. This significantly reduces material waste and solid waste generation.

[0076] (2) Clean the precision filter with an organic solvent in a circulating manner.

[0077] After the residual slurry is drained, the precision filter is evacuated and filled with cleaning organic solvent. A circulation pump is then started for cleaning, with the solvent circulating in the same direction as the original filtration, i.e., backwashing is not performed to prevent impurities from entering the downstream pipes of the precision filter. After cleaning with the organic solvent, most of the soluble PAN adhering to the filter elements is dissolved. The PAN content in the cleaning solution is measured to determine whether the next step of water washing can proceed. Once the water washing conditions are met, the cleaning solution is transferred to an organic solvent cleaning solution buffer tank, and most of the residual cleaning solution on the filter elements is blown off with inert gas.

[0078] (3) Wash the precision filter with water to remove the solvent.

[0079] Disconnect the organic solvent cleaning line and switch to the water washing line for rinsing. During this process, a small amount of PAN and deep GPAN precipitate out in solid form inside the filter material. The wash water is transferred to an intermediate tank for reuse in the next batch of cleaning until it reaches full level and is then sent to the solvent recovery system.

[0080] (4) High-temperature deep hydrolysis of GPAN

[0081] After draining the wash water, inject fresh water into the precision filter or directly use the washing water at the end of the wash. Switch the pipeline and perform high-temperature hydrolysis (i.e., deep hydrolysis treatment) to raise the temperature to the hydrolysis temperature. If a deep hydrolysis circulation treatment unit is used, such as a self-circulating unit, a hydrolysis product tank can be set on the pipeline to continuously transfer the hydrolysis products in the precision filter to the hydrolysis product tank. At the same time, a condenser is set up for reflux to condense and reflux the water in the hydrolysis product tank. The clean distilled water formed by the reflux can be added to the precision filter to continuously dilute the concentration of hydrolysis products in the precision filter. When a sufficient treatment time is reached, the precision filter contains only distilled water, thus completing the online deep cleaning. When the precision filter is treated alone, it is cooled after hydrolysis for a certain time, and the hydrolysate is transferred to the hydrolysis product tank. Then, it is cleaned by several cycles of water washing. In step (4), the deep treatment can be performed independently by heating the precision filter in a closed manner for a certain time, or it can be combined with the hydrolysis product tank and condenser.

[0082] (5) Recovery of decomposition solution

[0083] The material in the hydrolysis product tank or flash evaporator is further evaporated and dried. The hydrolysis products of GPAN and PAN are treated as solid waste. The evaporated condensate can be reused in the above steps (3) or (4).

[0084] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0085] Compared with the prior art, the present invention has the following advantages:

[0086] 1) The precision filter is cleaned with organic solvent circulation to remove non-gel soluble PAN stock solution, reducing the difficulty and labor intensity of disassembling the filter element assembly, and the solvent is used in stages to reduce the amount of waste liquid.

[0087] 2) Compared with existing technologies, no additional alkali or acid is added. Water is used as the gel decomposition liquid. The degree of gel cleaning is controlled by temperature and time, which reduces the corrosiveness to metal filter materials. The gel impurities are removed to a high degree, and the precision filter can be reused effectively.

[0088] 3) The complete cleaning process design ensures that impurities and water will separate on their own during the flash evaporation process in the flash evaporator or the evaporation process in the hydrolysis product tank in the deep hydrolysis circulation treatment unit. All residual water in the decomposition liquid is reused, and deep cleaning only generates a small amount of solid waste.

[0089] In summary, the cleaning method for the precision filter of this invention removes most of the attached PAN stock solution through organic solvent cleaning, significantly reducing the amount of polymer to be hydrolyzed. Using water as a decomposing agent, the nitrile groups in PAN and GPAN react rapidly under high temperature and pressure, resulting in main chain scission. GPAN and PAN can be rapidly hydrolyzed in water into water-soluble low-molecular-weight polymers such as amides and carboxylic acids, transforming gel-like impurities attached to the deep pores of the filter media into water-soluble amides and carboxylic acids, achieving deep hydrolysis. Therefore, this invention eliminates the need for disassembling and assembling the filter element, achieving fully automated online cleaning with a simple process. The method of this invention provides significant cleaning results without the addition of additional alkali or acid, extending the service life of the filter element, reducing labor intensity, meeting occupational health requirements, and reducing environmental pollution. It features fewer cleaning procedures, shorter time, lower labor intensity, less waste generation, high degree of decomposition of impurities such as GPAN, and low corrosivity of the filter media. Attached Figure Description

[0090] Figure 1 This is a schematic diagram of a cleaning system according to the present invention;

[0091] Figure 2 This is a schematic diagram of another cleaning system according to the present invention.

[0092] Explanation of reference numerals in the attached figures:

[0093] Figure 1 In the middle, 1-organic solvent feed pipe, 2-water feed pipe, 3-precision filter, 3-1-precision filter heat transfer oil jacket, 4-organic solvent circulation pipe, 5-water circulation pipe, 6-air inlet unit, 7-vacuum unit, 8-hydrolysis product tank, 8-1-hydrolysis product tank heat transfer oil jacket, 9-condenser, 16-spinning solution feed pipe, 17-liquid discharge unit, 18-solid waste discharge pipe, 19-spinning section feed pipe.

[0094] Figure 2 In the middle, 1-organic solvent feed pipe, 2-water feed pipe, 3-precision filter, 3-1-precision filter heat transfer oil jacket, 4-organic solvent circulation pipe, 5-water circulation pipe, 6-air inlet unit, 7-vacuum unit, 10-pressure reducing valve, 11-flash evaporator, 11-1-flash evaporator heat transfer oil jacket, 12-steam compressor, 13-heat exchanger, 14-condenser, 15-water tank, 16-spinning solution feed pipe, 17-liquid discharge unit, 18-solid waste discharge pipe, 19-spinning section feed pipe. Detailed Implementation

[0095] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0096] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0097] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0098] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0099] Example 1

[0100] like Figure 1 The diagram shows a cleaning system for a precision filter according to the present invention, comprising a feeding unit, a precision filter, and a discharging unit; the feeding unit is connected to the precision filter and feeds material into the precision filter to clean it; after cleaning, the material in the precision filter is discharged through the discharging unit; the feeding unit includes an organic solvent feeding pipe, a water feeding pipe, a circulating pump, an organic solvent circulating pipe, and a water circulating pipe;

[0101] Organic solvent feed pipe 1, circulation pump p1, precision filter 3, and organic solvent circulation pipe 4 are connected in sequence to form an organic solvent circulation cleaning circuit.

[0102] Water inlet pipe 2, circulation pump p2, precision filter 3, and water circulation pipe 5 are connected in sequence to form a water circulation cleaning circuit.

[0103] The cleaning system also includes an air intake unit 6 and / or a vacuum unit 7; the vacuum unit 7 is connected to the precision filter 3 through valve V2 before the material is fed into the feed unit, so as to create a negative pressure environment inside the precision filter. After the negative pressure environment meets the requirements, valve V2 is closed; the air intake unit 6 is connected to the precision filter through valve V1 before the material is discharged from the precision filter, so as to inject gas into the precision filter and create a high pressure environment inside the precision filter.

[0104] The cleaning system also includes a deep hydrolysis circulation treatment unit; the deep hydrolysis circulation treatment unit is selected from the reflux self-circulation unit; the reflux self-circulation unit includes a hydrolysis product tank 8 and a condenser 9; the discharge end of the precision filter 3, the hydrolysis product tank 8, the condenser 9, and the feed end of the precision filter 3 are connected in sequence through pipelines to form a circulation loop.

[0105] The cleaning system of the precision filter of the present invention operates as follows:

[0106] (1) The spinning solution feed pipe 16 feeds the material into the precision filter. The filtered material is sent to the spinning section feed pipe 19 through switch v5. When the precision filter 3 needs to be cleaned, close or switch the relevant valves to make the precision filter independent. Open the two three-way valves v1, v12 and v13 to switch to the direction of the raw solution to the recovery tank. Pressurize and discharge the raw solution as much as possible through the liquid discharge pipe 17.

[0107] (2) Close v1, keep v12 unchanged, switch v3, v9, v10 and v13 to the organic solvent circulation cleaning pipeline, open v2, evacuate the system and then close v2;

[0108] (3) Open V16, the cleaning solvent enters the system, turn on the circulation pump P1, and when the system is full of solvent, turn off V16 to start circulation.

[0109] (4) After solvent washing is complete, stop p1, switch v13 to the discharge direction ac, open v1 to pressurize, and use nitrogen to discharge the cleaning liquid. After discharge, close v1 valve.

[0110] (5) Switch the pipeline to the cleaning water circulation route, i.e., v9 is in the bc direction, v10 is in the ac direction, v13 is in the ba direction, v12 is in the ca direction, v3 is in the cb direction, v4 is in the ab direction, confirm that v17 is closed, open v2 to draw a vacuum, close v2, open v17 to fill with water, close v17 after it is full, start circulation, when the water washing is finished, switch v13 to the ac direction, open v1 to pressurize and drain, repeat (5) operation until the requirements are met;

[0111] (6) Switch the pipeline to the hydrolysis self-circulation route, i.e., switch V12 to the bc direction, keep V3 in the bc direction, switch V4 to the ac direction, switch V5 to the ba direction, open V7, V11, and V17, add water to the product decomposition tank 8 to 50% of its capacity, close V11 and V17, and switch V12 to the ba direction. Confirm that V1, V2, V6, V8, and V14 are closed, and heat up for hydrolysis. Note that the liquid inlet of the hydrolysis product tank must be higher than the precision filter to ensure that the filter is full. The reflux self-circulation process is as follows: When the precision filter is connected to the hydrolysis product tank, the water in the hydrolysis product tank evaporates (the hydrolysis products accumulate in the tank) to the condenser. After condensation, the liquid level in the pipe gradually increases and flows back to the filter. This condensate will dissolve the hydrolysate and overflow through the top of the filter to the hydrolysis product tank. The content of hydrolysate in the filter will gradually decrease. As long as the heating supply and self-circulation time are sufficient (the filter will eventually contain only clean water), the deep decomposition treatment is set to condenser (or compressor) for reflux, which can continuously transfer the hydrolysis products in the precision filter to the hydrolysis product tank (or flash evaporator), while continuously diluting the concentration of the hydrolysis products in the precision filter.

[0112] (7) After a certain period of time, the filter is either rinsed with clean water or circulated for a sufficient time. After the deep hydrolysis treatment is completed, the precision filter is cooled down for a period of time. Then, the valve is turned from v12 to ca to drain the water from the precision filter. The pH value of the water is tested. If it is almost neutral, the precision filter is not rinsed with water again and is vacuum dried. Otherwise, the precision filter is rinsed with water again and vacuum dried to complete the cleaning. The material in the product decomposition tank 8 is discharged from the system through the solid waste discharge pipe 18.

[0113] In the invention, the precision filter 3 is heated by the precision filter heat transfer oil jacket 3-1, and the hydrolysis product tank 8 is heated by the hydrolysis product tank heat transfer oil jacket 8-1.

[0114] Example 2

[0115] It is basically the same as the cleaning system in Example 1, except that it does not include the hydrolysis product tank, condenser, and related connecting pipes and valves. During the deep hydrolysis treatment, all valves of the precision filter are closed. After a period of deep hydrolysis treatment, the valves are turned from V12 to CA to drain the water from the precision filter. The precision filter is then rinsed with water multiple times and vacuum dried to complete the cleaning.

[0116] Example 3

[0117] like Figure 2The diagram shows a cleaning system for a precision filter according to the present invention, comprising a feeding unit, a precision filter, and a discharging unit; the feeding unit is connected to the precision filter and feeds material into the precision filter to clean it; after cleaning, the material in the precision filter is discharged through the discharging unit; the feeding unit includes an organic solvent feeding pipe, a water feeding pipe, a circulating pump, an organic solvent circulating pipe, and a water circulating pipe;

[0118] Organic solvent feed pipe 1, circulation pump p1, precision filter 3, and organic solvent circulation pipe 4 are connected in sequence to form an organic solvent circulation cleaning circuit.

[0119] Water inlet pipe 2, circulation pump p2, precision filter 3, and water circulation pipe 5 are connected in sequence to form a water circulation cleaning circuit.

[0120] The cleaning system also includes an air intake unit 6 and / or a vacuum unit 7; the vacuum unit 7 is connected to the precision filter 3 through valve V2 before the material is fed into the feed unit, so as to create a negative pressure environment inside the precision filter. After the negative pressure environment meets the requirements, valve V2 is closed; the air intake unit 6 is connected to the precision filter through valve V1 before the material is discharged from the precision filter, so as to inject gas into the precision filter and create a high pressure environment inside the precision filter.

[0121] The cleaning system also includes a deep hydrolysis circulation treatment unit; the deep hydrolysis circulation treatment unit is selected from the forced circulation unit; the forced circulation unit includes a pressure reducing valve 10, a flash evaporator 11, a steam compressor 12, a heat exchanger 13, a condenser 14, a water tank 15, and a pressurized circulation pump P4; the discharge end of the precision filter 3, the pressure reducing valve, the flash evaporator, the steam compressor, the heat medium pipe of the heat exchanger, the condenser, and the feed end of the water tank are connected in sequence through pipelines; the discharge end of the water tank, the pressurized circulation pump, the heat exchange tube of the heat exchanger, and the feed end of the precision filter are connected in sequence through pipelines; forming a forced circulation loop.

[0122] The cleaning system of the precision filter of the present invention operates as follows:

[0123] (1) The spinning solution feed pipe 16 supplies material to the precision filter, and the pump p3 provides power. The filtered material is sent to the spinning section feed pipe 19 through the switch v5. When the precision filter 3 needs to be cleaned, close or switch the relevant valves to make the precision filter independent. Open valves v1 and v13. Switch the v13 three-way valve to the direction of the raw solution to the recovery tank. Pressurize and discharge the raw solution as much as possible through the liquid discharge pipe 17.

[0124] (2) Close v1 and v13, open v2\ Evacuate the system and then close v2. Switch v9, v11 and v12 to the organic solvent circulation cleaning pipeline.

[0125] (3) Turn on V7, the cleaning organic solvent enters the system, turn on the circulation pump P1, and when the system is full of solvent, turn off V7 to start circulation;

[0126] (4) After solvent washing is completed, stop the pressurized circulation pump P1, open V13 to the discharge direction, open V1 to pressurize, and use nitrogen to discharge the cleaning liquid. After discharge, close the V1 valve.

[0127] (5) After adjusting v9, v11 and v12 to switch to the cleaning water circulation route, close v12, open v2 to draw a vacuum, close v2, open v8 to fill with water, close v8 after filling, turn on circulation pump p2, open v3 to start circulation, when the water washing is finished, open v13 to the discharge direction, open v1 to pressurize and drain, repeat (5) until the requirements are met.

[0128] (6) Open V8 to fill with water. After filling, close V8 and switch the pipeline to the forced circulation route, i.e., close it. Confirm that V1, V2, and V11 are closed. Heat up and hydrolyze. Send the decomposed water in the precision filter to the flash evaporator through the pressure reducing valve. The water sent to the flash evaporator partially or completely escapes in the form of steam. The escaped steam is pressurized and used as a heat source to exchange heat with the pressurized water from the water tank. The steam after heat exchange is condensed and then used as makeup water to replenish the water tank. The pressurized water after heat exchange is replenished into the precision filter through valve V12 for deep decomposition treatment, forming a forced circulation.

[0129] (7) After a certain period of time, the filter is either rinsed with clean water or circulated for a sufficient time. After the deep hydrolysis treatment is completed, the precision filter is cooled down for a period of time. Then, the valve v13 is opened to discharge the water in the precision filter. The pH value of the water is tested. If it is almost neutral, the precision filter is not rinsed with water again and is vacuum dried. Otherwise, the precision filter is rinsed with water again and vacuum dried to complete the cleaning. The material in the flash evaporator 11 is discharged from the system through the solid waste discharge pipe 18.

[0130] In the invention, the precision filter 3 is heated by the precision filter heat transfer oil jacket 3-1, and the flash evaporator 11 is heated by the flash evaporator heat transfer oil jacket 11-1.

[0131] Example 4

[0132] The cleaning system shown in Example 2 was used to clean a six-core candle-type precision filter made of sintered metal fiber felt with a filtration accuracy of 2 μm. The total filtration area was approximately 2 m². 2 The apparent viscosity of the filter is 68 Pa·s (60℃, 1s). -1The spinning solution has a flow rate of 30 kg / h and a designed differential pressure threshold of 0.5 MPa. When the filtration differential pressure reaches 0.4 MPa, an online switching procedure is initiated. Once the standby precision filter meets the spinning requirements, the precision filter to be cleaned is short-circuited, and a slurry discharge operation is performed. Nitrogen gas is used to pressurize the precision filter outlet to 0.3 MPa, causing the slurry to slowly flow from the discharge ports on the filter and feed pipes to the intermediate slurry return tank. When the nitrogen flow rate continues to increase or the pressure cannot be maintained, it can be determined that the slurry has been basically completely discharged.

[0133] Vacuum the precision filter, draw dimethyl sulfoxide cleaning solvent into the cleaning solution buffer tank, heat the precision filter to 75°C, and start the circulating diaphragm pump at a flow rate of 2.5 m... 3 The precision filter and its upstream and downstream pipelines were circulated and cleaned at a flow rate of / h for 8 hours. The cleaning solution was sampled every 2 hours, and the PAN solid content in the cleaning solution was measured and found to be 0.11%, at which point it stopped increasing significantly. The filter assembly was then purged with nitrogen gas to drain the cleaning solution into its buffer tank, while simultaneously cooling to room temperature.

[0134] The precision filter was circulated and cleaned three times with demineralized water at 60°C, each cycle lasting 15 minutes. The third rinse water was retained, and some demineralized water was added to bring the hydrolysis product tank to a certain level. The temperature was raised to 250°C, and the treatment was started at 250°C and timed for 4 hours. After the decomposition treatment was completed, the temperature was lowered, and the decomposition liquid was transferred to the hydrolysis product tank. The precision filter was replaced with cleaning water and the process was repeated three times. The pH value of the final rinse water was measured to be 6.7, which was the same as that of fresh demineralized water. The filter element was vacuum dried at 80°C for 2 hours to complete the cleaning process.

[0135] The decomposition liquid was subjected to rotary evaporation to obtain low molecular weight polymer solid waste with amide and carboxyl side groups. The specific quantities are shown in Table 1.

[0136] Referring to GB / T 31909-2015, "Determination of air permeability in permeable sintered metallic materials," the air permeability test was conducted at room temperature using anhydrous and oil-free compressed air. The air permeability results of the filter element after cleaning using the above method are shown in Table 1.

[0137] Examples 5-7

[0138] The same stock solution with a viscosity similar to that in Example 1 (deviation ±2 Pa·s) was used for filtration. After reaching the same threshold, the precision filter was cleaned. The only difference was in the hydrolysis process, as follows:

[0139] Example 5: The temperature was controlled at 250℃, and the hydrolysis time was controlled at 6 hours.

[0140] Example 6: The temperature was controlled at 230℃, and the hydrolysis time was controlled at 8 hours.

[0141] In Example 7, the hydrolysis temperature was controlled at 210℃ and the hydrolysis time was controlled at 8h.

[0142] The remaining steps are the same as in Example 1. The decomposition liquid is rotary evaporated to obtain low molecular weight polymer solid waste with amide and carboxyl side groups. The specific quantities are shown in Table 1. The air permeability results of the filter element after cleaning by the above method are shown in Table 1.

[0143] Example 8

[0144] The precision filter was cleaned using the cleaning system shown in Example 1. The apparent viscosity of the precision filter was 67.1 Pa·s (60°C, 1 s). -1 The spinning solution was used at a flow rate of 30 kg / h, with a designed differential pressure threshold of 0.5 MPa. When the filtration differential pressure reached 0.46 MPa, an online switching procedure was initiated. Once the standby precision filter met the spinning requirements, the precision filter to be cleaned was short-circuited, and a slurry discharge operation was performed. The slurry discharge, solvent cleaning, and cleaning water circulation washing operations were the same as in Example 1. After the circulation washing was completed, water was continuously added to the hydrolysis product tank until it reached half the tank level, at which point the filter was full. The precision filter and the hydrolysis product tank were heated to 250°C, and the condenser (tube type, 0.5m) was controlled. 2 The cooling water inlet flow rate was adjusted to raise the condensate temperature in the condenser to 200℃, thus establishing a circulating hydrolysis system between the precision filter, the hydrolysis product tank, and the condenser. After 6 hours of continuous circulation cleaning, the temperature was lowered to room temperature. The pH of the aqueous solution in the filter was measured to be 7.1, indicating that the solution still contained a small amount of hydrolysis products. The aqueous solution in the filter was drained, and the filter was washed once with clean water and dried to complete the filter cleaning. The decomposition products in the hydrolysis product tank were rotary evaporated to obtain low molecular weight polymer solid waste with amide and carboxyl side groups; the specific quantities are shown in Table 1. The air permeability results of the filter element after cleaning using the above method are shown in Table 1.

[0145] Example 9

[0146] Using the method shown in Example 3 (i.e.) Figure 2 The cleaning system (shown) cleans the precision filter. The apparent viscosity of the precision filter is 64.8 Pa·s (60℃, 1s). -1The spinning solution is supplied with a flow rate of 30 kg / h and a design differential pressure threshold of 0.5 MPa. When the filtration differential pressure reaches 0.46 MPa, an online switching procedure is initiated. Once the standby precision filter meets the spinning requirements, the precision filter to be cleaned is short-circuited, and a slurry discharge operation is performed. The slurry discharge, solvent cleaning, and cleaning water circulation washing operations are the same as in Example 1. After the circulating water washing is completed, the precision filter 3 is heated to 250°C. Once the temperature stabilizes, the pressurized circulation pump p4 (such as a high-pressure water supply plunger pump) is started, and the pressure reducing valve 10 is gradually opened. The hydrolyzed solution in the filter flashes through the pressure reducing valve 10 in the flash evaporator 11. The flash steam is compressed by the steam compressor 12 and then flows through the shell of the heat exchanger 13 to preheat the supplementary water from the pressurized circulation pump p4 (which flows through the heat exchanger tubes of the heat exchanger 13). Finally, it is condensed by the condenser 14 and returned to the water tank 15. The temperature inside the precision filter 3 is controlled by the jacket, and the water supply flow rate is adjusted by the pressure reducing valve. Maintain the precision filter at 250°C with a 0.15m... 3 After circulating water at a flow rate of [flow rate] / h for 6 hours, the temperature was lowered to room temperature. The pH of the aqueous solution in the filter was measured to be 6.8, indicating that the decomposition products in the precision filter had been largely removed. The aqueous solution in the filter was drained, and the filter was washed once with clean water and dried to complete the filter cleaning. The decomposition products in the hydrolysis product tank were subjected to rotary evaporation to obtain low molecular weight polymer solid waste with amide and carboxyl side groups, the specific quantities of which are shown in Table 1. The air permeability results of the filter element after cleaning using the above method are shown in Table 1.

[0147] Comparative Example 1

[0148] The original solution process of Example 1 was used for filtration. After reaching the same threshold, the precision filter was cleaned using the same steps (1) and (2) as in Example 1. Then, a 5% NaOH aqueous solution was circulated in the precision filter to allow the gel to undergo alkaline hydrolysis at 60°C for 6 hours. After hydrolysis, the hydrolysate was drained, and the filter was then cleaned multiple times at 60°C for 20 minutes each time. The cleaning was completed when the pH of the deionized water cleaning solution was approximately the same as that of the fresh water. The cleaning solution was then rotary evaporated to obtain solid waste containing NaOH. The air permeability of the filter element after cleaning using the above method is shown in Table 1.

[0149] Table 1 summarizes the results of the examples, comparative examples, and the air permeability measurement of the new filter cartridges. It is evident that the high-temperature hydrolysis cleaning method is significantly effective, easily and completely decomposing even GPAN that is deeply adhered to the internal pores of the filter cartridge and has undergone some cross-linking. Although NaOH hydrolysis is also effective, the hydrolysis products are difficult to separate from NaOH, and the accumulation of hydrolysis products during repeated use of the decomposition solution increases the viscosity of the cleaning solution, affecting the cleaning effect. In terms of solid waste generation, high-temperature hydrolysis is far less than that of the alkaline cleaning method.

[0150] Table 1

[0151]

[0152] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0153] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0154] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application’s filing, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0155] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. A method for cleaning a precision filter, comprising the following steps: First, the precision filter after slurry discharge is cleaned with organic solvents, then washed with water, and then subjected to deep hydrolysis with water, followed by drying to complete the cleaning process; or, the precision filter after slurry discharge is first cleaned with organic solvents, then washed with water, then subjected to deep hydrolysis with water, then washed with water, and then dried to complete the cleaning process. The precision filter is a precision filter for filtering spinning solution; The temperature for deep decomposition processing is 200~300℃; The deep decomposition process takes 4 to 12 hours. The cleaning method is a fully automated online cleaning method.

2. The cleaning method for a precision filter according to claim 1, characterized in that: The cleaning method for the precision filter specifically includes the following steps: (1) Use organic solvents to coarsely wash the emptied precision filter; (2) Wash the precision filter after coarse washing with water to remove organic solvents; (3) After washing, drain the washing water in the precision filter and replace it with fresh water; or, retain the washing water from the last washing in step (2); after filling the precision filter with water, heat it to perform deep hydrolysis treatment on the gel impurities attached to the precision filter. (4) After the deep hydrolysis treatment is completed, drain the decomposition liquid in the precision filter, dry it, and complete the cleaning of the precision filter; or after the deep hydrolysis treatment is completed, drain the decomposition liquid in the precision filter, wash the precision filter with water, dry it, and complete the cleaning of the precision filter.

3. The cleaning method for a precision filter according to claim 2, characterized in that: In step (1), The precision filter is a precision filter for filtering carbon fiber spinning solution; and / or, Before coarse washing, pressure is applied to drain the slurry from the precision filter and its pipelines; and / or, Before the organic solvent enters the precision filter, the precision filter is first evacuated, and then the organic solvent is injected into the precision filter.

4. The cleaning method for a precision filter according to claim 3, characterized in that: In step (1), before coarse washing, protective gas is injected into the precision filter to create a pressurized environment, thereby draining the slurry from the precision filter and its pipeline.

5. The cleaning method for a precision filter according to claim 2, characterized in that: In step (1), The organic solvent is selected from polar organic solvents; and / or, The temperature for rough washing is below 120°C; and / or, During the coarse cleaning, an organic solvent is used for circulating cleaning, and the direction of solvent circulation is the same as the filtration direction of the precision filter.

6. The cleaning method for a precision filter according to claim 5, characterized in that: In step (1), The polar organic solvent is selected from at least one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and ethylene carbonate; and / or, The temperature for rough washing is 25~120℃; and / or, When the solid content of impurities in the organic solvent used for circulating cleaning exceeds 5%, the circulation is stopped, the organic solvent in the precision filter is discharged and replaced with fresh organic solvent, or fresh organic solvent is used to replace part of the organic solvent in the precision filter before circulating cleaning is performed.

7. The cleaning method for a precision filter according to claim 6, characterized in that: The temperature for rough washing is 65~90℃; and / or, If the solid impurity content in the organic solvent to be circulated for cleaning does not increase significantly and the solid impurity content in the organic solvent to be circulated for cleaning is below 5%, then the circulation and cleaning of the organic solvent should be stopped.

8. The cleaning method for a precision filter according to claim 7, characterized in that: If the solid impurity content in the organic solvent to be circulated for cleaning does not increase significantly and the solid impurity content in the organic solvent to be circulated for cleaning is below 1%, then the circulation and cleaning of the organic solvent is stopped.

9. The cleaning method for a precision filter according to claim 8, characterized in that: If the solid impurity content in the organic solvent to be circulated for cleaning does not increase significantly and the solid impurity content in the organic solvent to be circulated for cleaning is below 0.5%, then the circulation and cleaning of the organic solvent is stopped.

10. The cleaning method for a precision filter according to claim 2, characterized in that: Step (2), during water washing, the precision filter is cleaned by circulating water.

11. The cleaning method for a precision filter according to claim 10, characterized in that: During the circulating cleaning process, if the organic solvent content in the circulating cleaning water exceeds 10%, the circulation is stopped, all the water in the precision filter is drained and replaced with fresh water, and then the circulating cleaning is resumed; alternatively, during the circulating cleaning process, the cleaning water is drained while fresh water is injected.

12. The cleaning method for a precision filter according to claim 11, characterized in that: If the organic solvent content in the water to be circulated for cleaning does not increase significantly and the organic solvent content in the circulating cleaning water is below 10%, then the water circulation cleaning should be stopped.

13. The cleaning method for a precision filter according to claim 12, characterized in that: If the organic solvent content in the water to be circulated for cleaning does not increase significantly and the cleaning solvent content in the circulated cleaning water is below 1%, then the water circulation cleaning should be stopped.

14. The cleaning method for a precision filter according to claim 13, characterized in that: During the circulating cleaning process, the temperature of the circulating water is 0~100℃.

15. The cleaning method for a precision filter according to claim 14, characterized in that: During the circulating cleaning process, the temperature of the circulating water is 60~80℃.

16. The cleaning method for a precision filter according to claim 2, characterized in that: Step (3), The temperature for deep decomposition treatment is 240~280℃; and / or, The deep decomposition process takes 4 to 8 hours.

17. The cleaning method for a precision filter according to claim 2, characterized in that: Step (3), the deep decomposition processing method is selected from at least one of the following methods: Method 1: During the deep decomposition process, the precision filter is sealed. After the deep decomposition process is completed, the precision filter is cooled to room temperature and pressure, and the decomposition liquid inside the precision filter is drained. Method 2: The precision filter is closed, but the decomposition water during the deep decomposition treatment can overflow from the precision filter into the hydrolysis product tank. The hydrolysis product tank is pre-stored with water and is under heating conditions. The decomposition water sent into the hydrolysis product tank escapes partially or completely in the form of steam. The escaped steam condenses to form condensate, which is then used as makeup water to replenish the precision filter for deep decomposition treatment, forming a reflux self-circulation. Method 3: The precision filter is closed, but the decomposed water during the deep decomposition treatment can be discharged from the precision filter and sent to the flash evaporator after depressurization. The water sent to the flash evaporator partially or completely escapes in the form of steam. The escaped steam is pressurized and used as a heat source to exchange heat with the pressurized water from the water tank. The steam after heat exchange is condensed and used as makeup water to replenish the water tank. The pressurized water after heat exchange is replenished into the precision filter for deep decomposition treatment, forming a forced circulation.

18. The cleaning method for a precision filter according to claim 2, characterized in that: Step (4): Wash with water until no hydrolysate remains in the washing water; and / or, dry under vacuum. In steps (2) and (4), when water is used for rinsing, the water used is independently selected from at least one of domestic water and desalinated water; and / or, In step (1), when the precision filter is emptied, the discharged slurry is collected for later use; and / or, In step (2), the washing water is collected for later use; and / or, In step (4), after the deep hydrolysis treatment is completed, the decomposition liquid discharged from the precision filter is collected and treated.

19. A cleaning system for a precision filter, characterized in that: The cleaning system includes a feeding unit, a precision filter, and a discharging unit; The feeding unit is connected to the precision filter and feeds material into the precision filter to clean it; after cleaning, the material in the precision filter is discharged through the discharge unit; a heating device is also provided on the outside of the precision filter. The feeding unit feeds organic solvents or water; The cleaning method according to any one of claims 1-18 uses the cleaning system to clean the precision filter.

20. The cleaning system for a precision filter according to claim 19, characterized in that: The feeding unit includes an organic solvent feeding pipe and a water feeding pipe.

21. The cleaning system for a precision filter according to claim 20, characterized in that: The feeding unit also includes a circulating pump, an organic solvent circulating pipeline, and a water circulating pipeline; The organic solvent feed pipe, circulation pump, precision filter, and organic solvent circulation pipe are connected in sequence to form an organic solvent circulation cleaning loop; The water inlet pipe, circulating pump, precision filter, and water circulation pipe are connected in sequence to form a water circulation cleaning loop.

22. The cleaning system for a precision filter according to claim 19, characterized in that: The cleaning system also includes an air intake unit and / or a vacuum unit; The vacuum unit is connected to the precision filter before the feeding unit feeds the material, in order to create a negative pressure environment inside the precision filter. The intake unit is connected to the precision filter before the material is discharged from the precision filter, in order to create a high-pressure environment inside the precision filter.

23. The cleaning system for a precision filter according to claim 19, characterized in that: The cleaning system further includes a deep hydrolysis circulation treatment unit; the deep hydrolysis circulation treatment unit is selected from either a reflux self-circulation unit or a forced circulation unit. The reflux self-circulation unit includes a hydrolysis product tank and a condenser; the discharge end of the precision filter, the hydrolysis product tank, the condenser, and the feed end of the precision filter are connected in sequence through pipelines to form a circulation loop; The forced circulation unit includes a pressure reducing valve, a flash evaporator, a steam compressor, a heat exchanger, a pressurized circulation pump, a water tank, and a condenser. The discharge end of the precision filter, the pressure reducing valve, the flash evaporator, the steam compressor, the heat medium pipe of the heat exchanger, the condenser, and the feed end of the water tank are connected in sequence through pipelines. The discharge end of the water tank, the pressurized circulation pump, the heat exchange tube of the heat exchanger, and the feed end of the precision filter are connected in sequence through pipelines, forming a forced circulation loop.

24. The application of the cleaning method according to any one of claims 1-18 or the cleaning system according to any one of claims 19-23 in the cleaning of a precision filter used for filtering spinning solution.

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