Cleaning method, cleaning system and application of precision filter

Abstract

The invention discloses a cleaning method, a cleaning system and application of a precision filter. The cleaning method comprises the following steps: roughly cleaning the emptied precision filter by adopting an organic solvent; washing the roughly washed precision filter with water to elute the organic solvent; after washing, draining washing water in the precision filter to enable the precision filter to be filled with water, and heating to perform deep hydrolysis treatment on gel impurities attached in the precision filter; after the deep hydrolysis treatment is completed, completely discharging decomposition liquid in the precision filter; and washing with water and drying to complete cleaning of the precision filter. According to the cleaning method, deep decomposition treatment is conducted with water to replace an existing alkali washing procedure, efficient decomposition of GPAN can be achieved, the cleaning effect is good, the solid waste generation amount is small, and corrosivity is small. The invention further improves the process of deep decomposition treatment with water, provides a backflow self-circulation deep decomposition treatment process and a forced circulation deep decomposition treatment process, and further improves the cleaning effect.

Description

Technical Field

[0001] The present invention relates to the technical field of filter cleaning, and more particularly to a cleaning method, a cleaning system and applications of precision filters. Background Art

[0002] The filtration of spinning solution is very important in the production process of carbon fiber. If there are impurities in the spinning solution, it will cause broken fibers in the spinning process and oxidation and carbonization process, affecting the production stability and performance of carbon fiber. The industry generally uses precision filters to intercept and remove most of the impurities in the spinning solution. As impurities gradually accumulate in the filter element, the filtration pressure difference increases accordingly, and the precision filter's interception effect on elastic impurities such as gel becomes worse. Therefore, when the operating pressure difference of the precision filter reaches the design threshold, the filter element must be stopped and replaced. Due to the high cost of the filter element, it is generally considered to be reused after cleaning.

[0003] The impurities in the spinning solution are mainly polyacrylonitrile gel particles (GPAN for short), which are mainly low-crosslinked aggregates of polyacrylonitrile. General solvents such as dimethyl sulfoxide (DMSO), dimethylformamide (DMF) and dimethylacetamide (DMAc) have poor dissolution effects on GPAN and can generally only swell it. The commonly used method is ultrasonic enhanced solvent immersion or circulation cleaning. The principle is to further swell and break GPAN under the action of ultrasound or other external forces. When the size of the fragments is smaller than the pores of the filter material, they are carried away by the fluid. It is essentially a physical process. However, as the scale of GPAN decreases, the required crushing energy becomes higher and higher. On the other hand, the density distribution of the external input energy on the filter material has a greater impact on the cleaning effect. For filter materials with complex structures, it is generally difficult to effectively remove GPAN in the deep layer of the filter material.

[0004] In order to thoroughly clean the filter element, it is usually necessary to use chemical methods to decompose GPAN and precipitate the polyacrylonitrile (PAN) solids remaining in the pores of the filter material during the water washing process. The Chinese patent application number 201910317228.6 discloses a complex disc precision filter cleaning method. The method is carried out in sequence: disassembly solvent washing, assembly solvent washing, water washing, secondary disassembly and 30% concentration NaOH or KOH alkaline washing, water washing, drying, inspection and assembly. This method requires disassembly and assembly of the filter disc twice.

[0005] The Chinese patent with application number 202111349727.7 discloses another method for cleaning disc precision filters. It includes solvent boiling washing with bubble agitation, ultrasonic water washing, ultrasonic NaHCO3 alkaline washing and water washing, and then drying, testing and assembly. This method introduces bubbling during solvent boiling and washing. Although it increases the local disturbance to a certain extent and enhances the cleaning effect, it also produces a large amount of organic vapor containing solvent. In order to avoid the use of strong alkali, NaHCO3 is used for chemical treatment. However, the inventors and others have found that below 100°C, although the alkali solution has a significant decomposition effect on PAN, the decomposition effect on GPAN is not ideal. According to the "Corrosion Data and Material Selection Manual", the alkali solution is corrosive to stainless steel at 100°C and cannot be used for a long time.

[0006] In addition, the existing technologies all require the precision filter to be disassembled and assembled multiple times, and require special ultrasonic auxiliary equipment that matches the shape of the filter element. The procedures are complicated, time-consuming and labor-intensive, and a large amount of three wastes is generated. Therefore, in view of the problems that the precision filter of carbon fiber spinning solution is not easy to clean, the existing cleaning methods are complicated, labor-intensive, and the amount of three wastes to be treated is large, and the metal filter material is easily corroded, a new cleaning method needs to be proposed. Summary of the invention

[0007] In order to solve the problems in the prior art, the present invention proposes a cleaning method, a cleaning system and an application of a precision filter. The present invention proposes a new cleaning method. The cleaning method of the present invention uses water for deep decomposition treatment to replace the alkaline washing process such as NaOH and NaHCO3, and can also achieve efficient decomposition of GPAN, with good cleaning effect, less solid waste generation, and low corrosion to the filter material. The present invention further improves the process of deep decomposition treatment with water, and proposes a reflux self-circulation deep decomposition treatment process and a forced circulation deep decomposition treatment process, which can further improve the cleaning effect.

[0008] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows:

[0009] One of the purposes of the present invention is to provide a method for cleaning a precision filter, comprising the following steps: first, the precision filter after pulping is sequentially cleaned with an organic solvent, then washed with water, and then subjected to a deep hydrolysis treatment with water, and then optionally washed with water, and the cleaning is completed by drying.

[0010] In the cleaning method of the precision filter of the present invention, preferably,

[0011] The cleaning method of the precision filter comprises the following steps:

[0012] (1) Roughly wash the emptied precision filter with an organic solvent;

[0013] (2) washing the fine filter after rough washing with water to remove the organic solvent;

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

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

[0016] In the cleaning method of the precision filter of the present invention, preferably,

[0017] In step (1),

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

[0019] Before rough washing, the slurry in the precision filter and its pipeline is emptied by pressurization; preferably, a protective gas is injected into the precision filter to form a pressurized environment; and / or,

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

[0021] In the present invention, the specific forms of 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 discs, metal felt sintered filter discs, metal powder sintered filter plates, ceramic membranes, etc.

[0022] In the cleaning method of the precision filter of the present 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 of the rough washing is below 120°C, preferably 25 to 120°C, more preferably 65 to 90°C; and / or,

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

[0027] Preferably, when the solid content of impurities in the organic solvent for circulating 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 part of the organic solvent in the precision filter is replaced with fresh organic solvent, and then the circulation cleaning is performed again;

[0028] Further preferably, the solid content of impurities in the organic solvent to be circulated and cleaned does not increase significantly, and the solid content of impurities in the organic solvent to be circulated and cleaned is below 5%, and the circulation cleaning of the organic solvent is stopped; further preferably, the solid content of impurities in the organic solvent to be circulated and cleaned does not increase significantly, and the solid content of impurities in the organic solvent to be circulated and cleaned is below 1%, and the circulation cleaning of the organic solvent is stopped; more preferably, the solid content of impurities in the organic solvent to be circulated and cleaned does not increase significantly, and the solid content of impurities in the organic solvent to be circulated and cleaned is below 0.5%, and the circulation cleaning of the organic solvent is stopped;

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

[0030] Circulation cleaning should be understood as the solvent constantly circulating in the filter, and the impurities adhering to the filter are constantly dissolved in the solvent, so the solid content of the cleaning liquid is gradually increasing. 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 time, if the impurity content in the cleaning liquid is too high, it is necessary to open the fresh solvent valve and the cleaning liquid discharge valve to replace all or part of the cleaning solvent, and then circulate for a certain period of time after replacement to reach the rough cleaning index.

[0031] In the cleaning method of the precision filter of the present invention, preferably,

[0032] In step (2), during water washing, the precision filter is circulated and cleaned by water;

[0033] Preferably, during the circulation cleaning, 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 circulation cleaning is performed again; or, during the circulation cleaning, the cleaning water is discharged while fresh water is injected; that is, after the water circulation cleaning of the present invention is performed once, the water is discharged, and then new water is added, the water is circulated again, and then the water is discharged; or the cleaning water can be discharged while new water is injected;

[0034] Further preferably, the organic solvent content in the water to be circulated for cleaning has not increased significantly, and the organic solvent content in the circulating cleaning water is below 10%, and the water circulation cleaning is stopped; Still further preferably, the organic solvent content in the water to be circulated for cleaning has not increased significantly, and the cleaning solvent content in the circulating cleaning water is below 1%, and the water circulation cleaning is stopped;

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

[0036] In the cleaning method of the precision filter of the present invention, preferably,

[0037] Step (3),

[0038] The temperature of the deep decomposition treatment is 150-350°C, preferably 200-300°C, more preferably 240-280°C; and / or,

[0039] The time for deep decomposition treatment is 0.1 to 24 hours, preferably 0.25 to 12 hours, and more preferably 0.5 to 8 hours.

[0040] In the cleaning method of the precision filter of the present invention, preferably,

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

[0042] Method 1:

[0043] During deep decomposition treatment, the precision filter is closed. After the deep decomposition treatment is completed, the precision filter is cooled to normal temperature and pressure to drain the decomposition liquid in the precision filter;

[0044] Method 2: The precision filter is closed, but the decomposed water during the deep decomposition treatment can overflow from the precision filter into the hydrolyzate tank, which is pre-stored with water and is under heating conditions; the decomposed water sent to the hydrolyzate tank escapes partially or completely in the form of steam, and the escaped steam condenses to form condensed water, which is used as supplementary water to be replenished into the precision filter again for deep decomposition treatment to form 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 decompression; the water sent to the flash evaporator escapes partially or completely in the form of steam, and 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 added to the water tank as make-up water; the pressurized water after heat exchange is added to the precision filter for deep decomposition treatment, forming a forced cycle;

[0046] In the present invention, the self-circulation entering the hydrolyzate tank is a connected system, the pressure is equal, and the circulation flow is controlled by the heat flow during evaporation and condensation; the decomposed water entering the hydrolyzate tank, impurities are precipitated, and the water escapes in the form of steam, which is condensed and then replenished into the precision filter as supplementary water for deep decomposition treatment, forming a reflux self-circulation. In the forced circulation, the steam entering the flash evaporator is used to heat the water introduced from the water tank by the high-pressure pump; the water introduced from the water tank is pressurized by the high-pressure pump and heated by the steam from the flash evaporator, and then replenished into the precision filter.

[0047] Impurities in precision filters that cannot be dissolved by solvents are generally attached to the gaps in the filter element. During static closed hydrolysis, the impurities can only be removed after complete hydrolysis, and generally only diffuse into the main water. When there is a circulating flow, convective mass transfer helps the hydrolysis products dissolve in water, and when the impurities are smaller than the gaps, they may be carried away by the main flow, which can improve the cleaning effect to a certain extent. Compared with reflux self-circulation, forced circulation can increase the circulation volume during deep decomposition, thereby speeding up cleaning.

[0048] In the cleaning method of the precision filter of the present invention, preferably,

[0049] Step (4), washing with water until there is no hydrolyzate in the washing water; and / or, drying is vacuum drying; in the present invention, vacuum does not affect the washing, and the purpose of vacuum is to accelerate the drying and accelerate the discharge of protective gas when the precision filter is put into use after washing;

[0050] In step (2) and step (4), when water is used for washing, the water used is independently selected from at least one of domestic water and desalted water, preferably desalted 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 after washing 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 processed.

[0054] The second object of the present 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 feed unit is connected to the precision filter and feeds the material into the precision filter to clean the precision filter; 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 feed material of the feed unit is an organic solvent or water;

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

[0058] In the cleaning system of the precision filter of the present invention, preferably,

[0059] The feeding unit comprises an organic solvent feeding pipeline and a water feeding pipeline; preferably,

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

[0061] The organic solvent feed pipeline, the circulation pump, the precision filter, and the organic solvent circulation pipeline are sequentially connected to form an organic solvent circulation cleaning loop;

[0062] The water feed pipeline, the circulation pump, the precision filter and the water circulation pipeline are connected in sequence to form a water circulation cleaning loop.

[0063] In the cleaning system of the precision filter of the present invention, preferably,

[0064] The cleaning system further comprises 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, so as to generate a negative pressure environment in the precision filter;

[0066] The air intake unit is connected to the precision filter before the material in the precision filter is discharged, so as to generate a high-pressure environment in the precision filter.

[0067] In the cleaning system of the precision filter of the present invention, preferably,

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

[0069] The reflux self-circulation unit includes a hydrolyzate tank and a condenser; the discharge end of the precision filter, the hydrolyzate tank, the condenser, and the feed end of the precision filter are sequentially connected 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 pipe of the heat exchanger, and the feed end of the precision filter are connected in sequence through pipelines; forming a forced circulation loop.

[0071] The third object of the present invention is to provide an application of a cleaning method as described in any one of the objects of the present invention or a cleaning system as described in any one of the objects of the present invention in the cleaning of precision filters, preferably in the cleaning of precision filters used for spinning solution filtration.

[0072] The present invention first performs pulp removal and organic solvent cleaning on the precision filter that reaches the switching threshold, then performs water washing, and then performs deep hydrolysis treatment, and then washes the precision filter with water, and completes the cleaning by drying. The organic solvent and washing water after cleaning are removed from the solvent recovery system, and the decomposition liquid after deep hydrolysis treatment is removed from the drying recovery system, which effectively reduces the amount of three wastes generated compared to the existing cleaning method.

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

[0074] (1) Switching and discharging of the raw liquid precision filter

[0075] When the operating pressure difference of the precision filter reaches the specified threshold, the standby precision filter is switched. Through the air inlet and slurry discharge port set on the precision filter, the slurry remaining in the precision filter tank, filter element assembly and its connected pipeline to be cleaned is discharged into the re-slurry intermediate tank. The material in the re-slurry intermediate tank is degassed and sent to the material inlet of the standby precision filter. This greatly reduces material waste and solid waste generation.

[0076] (2) Circulate and clean the precision filter with organic solvent

[0077] When the residual slurry is drained, the precision filter is evacuated, the organic solvent for cleaning is sucked in, and the circulation pump is turned on for cleaning. The direction of solvent circulation is the same as the direction of stock liquid filtration, that is, no backwashing is performed to prevent impurities from entering the downstream pipeline of the precision filter. After cleaning with organic solvent, the soluble PAN adhering to the filter element is basically dissolved. The content of PAN in the cleaning liquid is determined to determine whether the next step of water washing can be carried out. After meeting the water washing conditions, the cleaning liquid is transferred to the organic solvent cleaning liquid buffer tank, and most of the residual cleaning liquid on the filter element is blown off with inert gas.

[0078] (3) Use water to wash the precision filter

[0079] Cut off the organic solvent cleaning pipeline and switch to the water washing pipeline for water washing. A small amount of PAN and deep GPAN will precipitate in the filter material in solid form during this process. The washing water is transferred to the intermediate tank and used again in the next batch of cleaning until the full liquid level goes to the solvent recovery system.

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

[0081] After draining the washing water, fresh water is injected into the precision filter or the washing water at the end of washing is directly used, the pipeline is switched, and high-temperature hydrolysis (i.e., deep hydrolysis treatment) is performed, and the temperature is raised to the hydrolysis temperature. If the deep hydrolysis circulation treatment unit is adopted, when the self-circulation unit is refluxed, the hydrolyzate in the precision filter can be continuously transferred to the hydrolyzate tank by arranging the hydrolyzate tank on the pipeline, and the condenser is refluxed at the same time, and the water in the hydrolyzate tank can be condensed and refluxed, and the clean distilled water formed by reflux can be supplemented in the precision filter, and the hydrolyzate concentration in the precision filter is continuously diluted. When the sufficient processing time is reached, only distilled water is contained in the precision filter, thereby completing the online deep cleaning. When the precision filter is processed separately, the temperature is lowered after hydrolysis for a certain period of time, and the hydrolyzate is transferred to the hydrolyzate tank, and then the cleaning is completed through several cycles of water washing. In step (4), the deep treatment can make the precision filter operate independently, that is, the closed temperature rise treatment of the precision filter is made for a certain period of time, and it can also be operated in conjunction with the hydrolyzate tank and the condenser.

[0082] (5) Recovery of decomposition liquid

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

[0084] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

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

[0086] 1) The organic solvent circulation cleaning of precision filters removes non-gel soluble PAN stock solution, reduces the difficulty and labor intensity of disassembling the filter element assembly, and the solvent classification application reduces the amount of waste liquid.

[0087] 2) Compared with the prior art, no additional alkali or acid is added, and only water is used as the gel deep decomposition liquid. The degree of gel cleaning is controlled by temperature and time, which reduces the corrosiveness to the metal filter material. The degree of gel impurity removal is high, and the precision filter has a good reuse effect.

[0088] 3) Complete cleaning process design: impurities and water will separate automatically during the flash evaporation in the flash evaporator or the evaporation in the hydrolysis product tank in the deep hydrolysis circulation treatment unit, and all the residual water in the decomposition liquid will be reused, and deep cleaning will only produce a small amount of solid waste.

[0089] In summary, the cleaning method of the precision filter of the present invention removes most of the attached PAN stock solution through organic solvent cleaning, greatly reducing the amount of polymer to be hydrolyzed. With water as a decomposing agent, the nitrile groups in PAN and GPAN react rapidly under high temperature and high pressure and undergo a main chain scission reaction. GPAN and PAN can be rapidly hydrolyzed into water-soluble low molecular weight polymers such as amides and carboxylic acids in water, so that the gel impurities attached to the deep voids of the filter material are converted into water-soluble amides and carboxylic acid low molecular weight polymers, achieving deep hydrolysis treatment. Therefore, the present invention can eliminate the disassembly and assembly of the filter element, realize fully automatic online cleaning, and the process is simple. The method of the present invention has an obvious cleaning effect, no additional alkali or acid is added, and the service life of the filter element can be extended, the labor intensity can be reduced, the occupational health requirements can be met, and environmental pollution can be reduced; it has the characteristics of fewer cleaning procedures, shorter time, lower labor intensity, less production of three wastes, higher decomposition degree of impurities such as GPAN, and lower corrosion of the filter material. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 A schematic diagram of a cleaning system of the present invention;

[0091] Figure 2 It is a schematic diagram of the flow of another cleaning system of the present invention.

[0092] Description of reference numerals:

[0093] Figure 1 Among them, 1-organic solvent feeding pipeline, 2-water feeding pipeline, 3-precision filter, 3-1-precision filter thermal oil jacket, 4-organic solvent circulation pipeline, 5-water circulation pipeline, 6-air intake unit, 7-vacuum unit, 8-hydrolyzate tank, 8-1-hydrolyzate tank thermal oil jacket, 9-condenser, 16-spinning solution feeding pipeline, 17-liquid discharge unit, 18-solid waste discharge pipeline, 19-spinning section feeding pipe.

[0094] Figure 2 Among them, 1-organic solvent feed pipeline, 2-water feed pipeline, 3-precision filter, 3-1-precision filter thermal oil jacket, 4-organic solvent circulation pipeline, 5-water circulation pipeline, 6-air intake unit, 7-vacuum unit, 10-pressure reducing valve, 11-flash evaporator, 11-1-flash evaporator thermal oil jacket, 12-steam compressor, 13-heat exchanger, 14-condenser, 15-water tank, 16-spinning solution feed pipeline, 17-liquid discharge unit, 18-solid waste discharge pipeline, 19-spinning section feed pipe. DETAILED DESCRIPTION

[0095] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall 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 specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0097] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0098] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0099] Example 1

[0100] like Figure 1 As shown, a cleaning system of a precision filter of the present invention comprises a feed unit, a precision filter, and a discharge unit; the feed unit is connected to the precision filter, and feeds materials into the precision filter to clean the precision filter; after cleaning, the materials in the precision filter are discharged through the discharge unit; the feed unit comprises an organic solvent feed pipeline, a water feed pipeline, a circulation pump, an organic solvent circulation pipeline, and a water circulation pipeline;

[0101] The organic solvent feed pipeline 1, the circulation pump p1, the precision filter 3, and the organic solvent circulation pipeline 4 are sequentially connected to form an organic solvent circulation cleaning loop;

[0102] The water feed pipeline 2, the circulation pump p2, the precision filter 3, and the water circulation pipeline 5 are connected in sequence to form a water circulation cleaning loop.

[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 a valve V2 before the feeding unit feeds materials, so as to create a negative pressure environment in the precision filter. After the negative pressure environment meets the requirements, the valve V2 is closed; the air intake unit 6 is connected to the precision filter through a valve V1 before the material in the precision filter is discharged, and gas is injected into the precision filter to create a high-pressure environment in the precision filter.

[0104] The cleaning system also includes a deep hydrolysis circulation treatment unit; the deep hydrolysis circulation treatment unit is selected from a 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 working process of the cleaning system of the precision filter of the present invention is as follows:

[0106] (1) The spinning stock solution feed pipe 16 feeds the material into the precision filter, and 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, the relevant valves are closed or switched, the precision filter is isolated, the valve v1 is opened, and the two three-way valves v12 and v13 are switched to the direction of the stock solution to the recovery tank, and the stock solution is discharged as much as possible through the liquid discharge pipe 17 under pressure;

[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, and the circulation pump p1 is turned on. When the system is full of solvent, close v16 to start circulation;

[0109] (4) After the solvent washing is completed, stop p1, switch v13 to the discharge direction ac, open v1 to increase the pressure, use nitrogen to discharge the cleaning liquid, and close v1 valve after discharge;

[0110] (5) Switch the pipeline to the cleaning water circulation route, that is, 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, and v4 is in the ab direction. Confirm that v17 is closed, open v2 to draw a vacuum, close v2, open v17 to inject water, close v17 after it is full, start the circulation, and end the water washing. Switch v13 to the ac direction, open v1 to pressurize and drain water, and repeat (5) until the requirements are met;

[0111] (6) Switch the pipeline to the hydrolysis self-circulation route, that is, v12 switches to the bc direction, v3 maintains the bc direction, v4 switches to the ac direction, v5 switches to the ba direction, open v7, v11 and v17, add 50% liquid level water to the product decomposition tank 8, close v11 and v17, and switch v12 to the ba direction. Confirm that v1, v2, v6, v8, and v14 are closed, increase the temperature for hydrolysis, and 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 product accumulates in the tank) to the condenser. After condensation, the liquid level in the tube gradually increases and flows back to the filter. The condensed water will dissolve the hydrolyzate and overflow to the hydrolysis product tank through the top of the filter. The content of hydrolysis product in the filter will gradually decrease. As long as the heat supply is sufficient, the self-circulation time is sufficient, and there is only clean water in the filter in the end), the deep decomposition treatment is set up with a condenser (or compressor) reflux, the hydrolyzate in the precision filter can be continuously transferred to the hydrolyzate tank (or flash evaporator), and the concentration of the hydrolyzate in the precision filter can be continuously diluted.

[0112] (7) After a certain period of time, or after washing with clean water or self-circulating for a sufficient time, after the deep hydrolysis treatment is completed, cool the precision filter for a period of time, then turn the valve v12 to the ca direction to discharge the water in the precision filter, and detect the pH value in the water. If it is almost neutral, do not wash the precision filter with water anymore, and vacuum dry it. Otherwise, wash the precision filter with water again, and vacuum dry it 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 thermal oil jacket 3-1, and the hydrolyzate tank 8 is heated by the hydrolyzate tank thermal oil jacket 8-1.

[0114] Example 2

[0115] It is basically the same as the cleaning system of Example 1, except that it does not include a hydrolyzate tank and a condenser and related connecting pipes and valves. During deep hydrolysis treatment, the valves of the precision filter are closed. After a period of deep hydrolysis treatment, the valve v12 is turned to the ca direction to drain the water in the precision filter, and the precision filter is washed with water several times and vacuum dried to complete the cleaning.

[0116] Example 3

[0117] like Figure 2As shown, a cleaning system of a precision filter of the present invention comprises a feed unit, a precision filter, and a discharge unit; the feed unit is connected to the precision filter, and feeds materials into the precision filter to clean the precision filter; after cleaning, the materials in the precision filter are discharged through the discharge unit; the feed unit comprises an organic solvent feed pipeline, a water feed pipeline, a circulation pump, an organic solvent circulation pipeline, and a water circulation pipeline;

[0118] The organic solvent feed pipeline 1, the circulation pump p1, the precision filter 3, and the organic solvent circulation pipeline 4 are sequentially connected to form an organic solvent circulation cleaning loop;

[0119] The water feed pipeline 2, the circulation pump p2, the precision filter 3, and the water circulation pipeline 5 are connected in sequence to form a water circulation cleaning loop.

[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 a valve V2 before the feeding unit feeds materials, so as to create a negative pressure environment in the precision filter. After the negative pressure environment meets the requirements, the valve V2 is closed; the air intake unit 6 is connected to the precision filter through a valve V1 before the material in the precision filter is discharged, and gas is injected into the precision filter to create a high-pressure environment in the precision filter.

[0121] The cleaning system also includes a deep hydrolysis circulation treatment unit; the deep hydrolysis circulation treatment unit is selected from a 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 pipe 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 working process of the cleaning system of the precision filter of the present invention is as follows:

[0123] (1) The spinning stock solution feed pipe 16 feeds 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, the relevant valves are closed or switched, the precision filter is independent, the valves v1 and v13 are opened, and the v13 three-way valve is switched to the direction of the stock solution to the recovery tank, and the stock solution is discharged as much as possible through the liquid discharge pipe 17 under pressure;

[0124] (2) Close v1 and v13, open v2, evacuate the system, close v2, and switch v9, v11, and v12 to the organic solvent circulation cleaning pipeline;

[0125] (3) Open v7, the cleaning organic solvent enters the system, and the circulation pump p1 is turned on. When the system is full of solvent, close v7 to start circulation;

[0126] (4) After the solvent washing is completed, stop the pressurized circulation pump p1, open v13 to the discharge direction, open v1 to pressurize, use nitrogen to discharge the cleaning liquid, and close the v1 valve after discharge;

[0127] (5) After adjusting v9, v11 and v12 to switch to the cleaning water circulation route, close v12, open v2 to evacuate, close v2, open v8 to fill with water, close v8 after filling, start the circulation pump p2, open v3, start the circulation, finish the water washing, open v13 to the discharge direction, open v1 to pressurize and drain, and repeat (5) until the requirements are met;

[0128] (6) Open v8 to inject water. After it is full, close v8 and switch the pipeline to a forced circulation route, i.e. close it. Make sure that v1, v2 and v11 are closed. Increase the temperature for hydrolysis. Send the decomposed water in the precision filter to the flash evaporator through the pressure reducing valve. The water sent to the flash evaporator escapes partially or completely in the form of steam. The escaped steam is pressurized and used as a heat source to exchange heat with pressurized water from the water tank. The steam after heat exchange is condensed and then added to the water tank as make-up water. The pressurized water after heat exchange is added to the precision filter through valve v12 for deep decomposition treatment, thus forming a forced circulation.

[0129] (7) After a certain period of time, or after washing with clean water or self-circulating for a sufficient time, after the deep hydrolysis treatment is completed, the precision filter is cooled for a period of time, and then the valve v13 is opened to discharge the water in the precision filter, and the pH value in the water is tested. If it is almost neutral, the precision filter is no longer washed with water and vacuum dried. Otherwise, the precision filter is washed with water again and vacuum dried. After the cleaning is completed, 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 the precision filter. A six-core candle-type precision filter made of sintered metal fiber felt with a filtration accuracy of 2 μm was cleaned. The total filtration area was about 2 m 2 , the apparent viscosity of the filtration is 68Pa.s (60℃, 1s -1) of spinning stock solution, the flow rate is 30kg / h, and the designed pressure difference threshold is 0.5MPa. When the filtration pressure difference reaches 0.4MPa, the online switching program is entered. When the standby precision filter meets the spinning conditions, the precision filter to be cleaned is short-circuited, and the slurry discharge operation is performed. Use nitrogen to pressurize the outlet of the precision filter to 0.3MPa, so that the slurry slowly flows from the slurry discharge ports on the filter and the feed pipeline to the re-slurry intermediate tank. When the nitrogen flow rate continues to increase or the pressure cannot be maintained, it can be judged that the slurry is basically discharged.

[0133] The precision filter is vacuumed and the dimethyl sulfoxide cleaning solvent is sucked from the cleaning liquid buffer tank. The precision filter is heated to 75°C and the circulating diaphragm pump is turned on at 2.5m 3 / h flow rate for 8 hours to clean the precision filter and its front and rear pipes. Sample the cleaning liquid every 2 hours and measure the solid content of PAN in the cleaning liquid. When it reaches 0.11%, it will no longer increase significantly. Use nitrogen to purge the filter element assembly, drain the cleaning liquid into its buffer tank, and cool it down to room temperature.

[0134] Use desalted water to clean the precision filter three times at 60°C, each cycle lasting 15 minutes. Keep the third cleaning water and add some desalted water to make the hydrolysis product tank reach a certain liquid level. Raise the temperature to 250°C and start the treatment for 4 hours from the time it reaches 250°C. Cool down after the decomposition treatment and transfer the decomposed liquid to the hydrolysis product tank. Replace the precision filter with cleaning water and repeat the operation three times. The pH value of the last cleaning water was measured to be 6.7, which is the same as that of fresh desalted water. Vacuum dry the filter element at 80°C for 2 hours to complete the cleaning.

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

[0136] Refer to GB / T 31909-2015 Determination of air permeability in permeable sintered metal materials, and conduct air permeability test with water-free and oil-free compressed air at room temperature. The air permeability results of the filter element after cleaning by the above method are shown in Table 1.

[0137] Embodiments 5 to 7

[0138] The original liquid process with a viscosity similar to that of Example 1 (deviation ±2Pa.s) was used for filtration, and the precision filter was cleaned after reaching the same threshold. The only difference was the hydrolysis process, which was as follows:

[0139] In Example 5, the temperature was controlled at 250°C and the hydrolysis time was controlled at 6h;

[0140] In Example 6, the temperature was controlled at 230° C. and the hydrolysis time was controlled at 8 h.

[0141] In Example 7, the hydrolysis temperature is controlled at 210° C. and the hydrolysis time is controlled at 8 h.

[0142] The remaining steps are the same as those in Example 1, and the decomposed liquid is subjected to rotary evaporation to obtain low molecular weight polymer solid waste with amide and carboxyl side groups, and the specific amount is 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, 1s -1 ) of the spinning solution, the flow rate is also 30kg / h, and the designed pressure difference threshold is 0.5MPa. When the filtration pressure difference reaches 0.46MPa, the online switching program is entered. When the standby precision filter meets the spinning conditions, the precision filter to be cleaned will be short-circuited, and the pulping operation will be performed. The pulping, solvent cleaning and washing water circulation washing operations are the same as those in Example 1. After the circulating water washing is completed, continue to add water to the hydrolyzate tank until it reaches half the liquid level of the hydrolyzate tank. At this time, the filter is full. Heat the precision filter and the hydrolyzate tank to 250°C, control the condenser (shell and tube type, 0.5m 2 ) The cooling water inlet flow rate is adjusted to make the condensate temperature of the condenser reach 200°C, thereby establishing a circulating hydrolysis system between the precision filter, the hydrolysis product tank and the condenser. After continuous circulation cleaning for 6 hours, it is cooled to room temperature. The pH value of the aqueous solution in the filter was measured to be 7.1, indicating that the solution in the filter still contains a small amount of hydrolysis product. Drain the aqueous solution in the filter, wash it with clean water once, and complete the filter cleaning after drying. The decomposition product in the hydrolysis product tank is rotary evaporated to obtain low molecular weight polymer solid waste with amide and carboxyl side groups. The specific amount is shown in Table 1. The air permeability results of the filter element after cleaning by the above method are shown in Table 1.

[0145] Example 9

[0146] Using the example 3 (i.e. Figure 2 The cleaning system (as shown) is used to clean the precision filter. The apparent viscosity of the precision filter is 64.8Pa.s (60℃, 1s -1) of the spinning solution, the flow rate is also 30kg / h, and the designed pressure difference threshold is 0.5MPa. When the filtration pressure difference reaches 0.46MPa, the online switching program is entered. When the standby precision filter meets the spinning conditions, the precision filter to be cleaned will be short-circuited, and the pulping operation will be performed. The pulping, solvent cleaning and washing 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. When the temperature stabilizes, start the pressurized circulation pump p4 (such as a high-pressure water replenishment plunger pump), and gradually open the pressure reducing valve 10. The hydrolyzed solution in the filter flashes in the flash evaporator 11 through the pressure reducing valve 10. The flash steam is compressed by the steam compressor 12 and then goes through the shell of the heat exchanger 13 to preheat the make-up water from the pressurized circulation pump p4 (which goes through the heat exchange tube of the heat exchanger 13), and finally 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 make-up water flow is adjusted by the pressure reducing valve. Maintain the precision filter at 250°C with a temperature of 0.15 m 3 / h flow rate replenishment cycle for 6 hours and then cool to room temperature. The pH value of the aqueous solution in the filter was measured to be 6.8, indicating that the decomposition products in the precision filter have been basically removed. Drain the aqueous solution in the filter, wash it with clean water once, and complete the filter cleaning after drying. The decomposition products in the hydrolysis product tank are rotary evaporated to obtain low molecular weight polymer solid waste with amide and carboxyl side groups. The specific amount is shown in Table 1. The air permeability results of the filter element after cleaning by 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 hydrolyze the gel with alkaline solution at 60°C, and the hydrolysis time was controlled to be 6 hours. After hydrolysis, the hydrolyzate was drained, and then it was washed by multiple cycles at 60°C, each washing for 20 minutes. When the pH value of the desalted water washing liquid is basically the same as that of fresh water, the washing is completed. The washing liquid is rotary evaporated to obtain solid waste containing NaOH. The air permeability results of the filter element after cleaning by the above method are shown in Table 1.

[0149] Table 1 summarizes the results of the air permeability measurements of the examples, comparative examples, and new filter elements. It can be seen that the high-temperature hydrolysis cleaning method is effective, and even GPAN that is deeply attached to the internal voids of the filter element and has undergone certain cross-linking can be easily and thoroughly decomposed. Although the effect of NaOH hydrolysis is also good, it is difficult to separate the hydrolysis product from NaOH. When the decomposition liquid is reused, the hydrolysis product accumulates, and the increased viscosity of the cleaning liquid affects the cleaning effect. The amount of solid waste generated by high-temperature hydrolysis is far less than that of the alkaline solution cleaning method.

[0150] Table 1

[0151]

[0152] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached 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 conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0154] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0155] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A method for cleaning a precision filter, comprising the following steps: The precision filter after pulping is first cleaned with an organic solvent, then washed with water, and then subjected to a deep hydrolysis treatment with water, and then optionally washed with water, and the cleaning is completed by drying.

2. The cleaning method of the precision filter according to claim 1, characterized in that: The cleaning method of the precision filter specifically comprises the following steps: (1) Roughly wash the emptied precision filter with an organic solvent; (2) washing the fine filter after rough washing with water to remove the organic solvent; (3) After washing, drain the washing water in the precision filter and replace it with fresh water; alternatively, retain the washing water from the last washing in step (2); after the precision filter is filled with water, increase the temperature to perform deep hydrolysis treatment on the gel impurities attached to the precision filter; (4) After the deep hydrolysis treatment is completed, the decomposition liquid in the precision filter is drained; the precision filter is optionally washed with water and dried to complete the cleaning of the precision filter.

3. The cleaning method of the precision filter according to claim 2, characterized in that: In step (1), The precision filter is a precision filter for filtering spinning solution; preferably a precision filter for filtering carbon fiber spinning solution; and / or, Before rough washing, the slurry in the precision filter and its pipeline is emptied by pressurization; preferably, a protective gas is injected into the precision filter to form a pressurized environment; and / or, Before the organic solvent enters the precision filter, the precision filter is first vacuumed, and then the organic solvent is injected into the precision filter.

4. The cleaning method of the precision filter according to claim 2, characterized in that: In step (1), 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, The temperature of the rough washing is below 120°C, preferably 25 to 120°C, more preferably 65 to 90°C; and / or, During rough cleaning, organic solvent is used for circulating cleaning, and the direction of solvent circulation is the same as the filtering direction of the precision filter; Preferably, when the solid content of impurities in the organic solvent for circulating 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 part of the organic solvent in the precision filter is replaced with fresh organic solvent, and then the circulation cleaning is performed again; Further preferably, the solid content of impurities in the organic solvent to be circulated and cleaned has not increased significantly, and the solid content of impurities in the organic solvent for circulated cleaning is below 5%, and the circulating cleaning of the organic solvent is stopped; still further preferably, the solid content of impurities in the organic solvent to be circulated and cleaned has not increased significantly, and the solid content of impurities in the organic solvent for circulated cleaning is below 1%, and the circulating cleaning of the organic solvent is stopped; more preferably, the solid content of impurities in the organic solvent to be circulated and cleaned has not increased significantly, and the solid content of impurities in the organic solvent for circulated cleaning is below 0.5%, and the circulating cleaning of the organic solvent is stopped.

5. The cleaning method of the precision filter according to claim 2, characterized in that: In step (2), during water washing, the precision filter is circulated and cleaned by water; Preferably, during the circulation cleaning, 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 circulation cleaning is performed again; or, during the circulation cleaning, the cleaning water is discharged while fresh water is injected; Further preferably, the organic solvent content in the water to be circulated for cleaning has not increased significantly, and the organic solvent content in the circulating cleaning water is below 10%, and the water circulation cleaning is stopped; Still further preferably, the organic solvent content in the water to be circulated for cleaning has not increased significantly, and the cleaning solvent content in the circulating cleaning water is below 1%, and the water circulation cleaning is stopped; Most preferably, during circulation cleaning, the temperature of the circulating water is 0 to 100°C, preferably 60 to 80°C.

6. The cleaning method of the precision filter according to claim 2, characterized in that: Step (3), The temperature of the deep decomposition treatment is 150-350°C, preferably 200-300°C, more preferably 240-280°C; and / or, The time for deep decomposition treatment is 0.1 to 24 hours, preferably 0.25 to 12 hours, and more preferably 0.5 to 8 hours.

7. The cleaning method of the precision filter according to claim 2, characterized in that: In step (3), the method of deep decomposition treatment is selected from at least one of the following methods: Method 1: During the deep decomposition treatment, the precision filter is closed. After the deep decomposition treatment is completed, the precision filter is cooled to normal temperature and pressure to drain the decomposition liquid in the precision filter; Method 2: The precision filter is closed, but the decomposed water during the deep decomposition treatment can overflow from the precision filter into the hydrolyzate tank, which is pre-stored with water and is under heating conditions; the decomposed water sent to the hydrolyzate tank escapes partially or completely in the form of steam, and the escaped steam condenses to form condensed water, which is used as supplementary water to be replenished into the precision filter again for deep decomposition treatment to form a reflux self-circulation; Method three: 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 decompression; the water sent to the flash evaporator escapes partially or completely in the form of steam, and the escaped steam is pressurized and used as a heat source to exchange heat with the pressurized water from the water tank, and the steam after heat exchange is condensed and added to the water tank as make-up water; the pressurized water after heat exchange is added to the precision filter for deep decomposition treatment, forming a forced circulation.

8. The cleaning method of the precision filter according to claim 2, characterized in that: Step (4), washing with water until no hydrolyzate is contained in the washing water; and / or, drying is vacuum drying; In step (2) and step (4), when water is used for washing, the water used is independently selected from at least one of domestic water and desalted water, preferably desalted 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 after washing 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 processed.

9. 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 feed unit is connected to the precision filter and feeds the material into the precision filter to clean the precision filter; 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 feed material of the feed unit is an organic solvent or water; The cleaning method described in any one of claims 1 to 8 preferably uses the cleaning system to clean the precision filter.

10. The cleaning system for the precision filter according to claim 9, characterized in that: The feeding unit comprises an organic solvent feeding pipeline and a water feeding pipeline; preferably, The feeding unit also includes a circulation pump, an organic solvent circulation pipeline and a water circulation pipeline; The organic solvent feed pipeline, the circulation pump, the precision filter, and the organic solvent circulation pipeline are sequentially connected to form an organic solvent circulation cleaning loop; The water feed pipeline, the circulation pump, the precision filter and the water circulation pipeline are connected in sequence to form a water circulation cleaning loop.

11. The cleaning system for the precision filter according to claim 9, characterized in that: The cleaning system further comprises 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, so as to generate a negative pressure environment in the precision filter; The air intake unit is connected to the precision filter before the material in the precision filter is discharged, so as to generate a high-pressure environment in the precision filter.

12. The cleaning system for the precision filter according to claim 9, characterized in that: The cleaning system further comprises a deep hydrolysis circulation treatment unit; the deep hydrolysis circulation treatment unit is selected from a reflux self-circulation unit or a forced circulation unit; The reflux self-circulation unit includes a hydrolyzate tank and a condenser; the discharge end of the precision filter, the hydrolyzate tank, the condenser, and the feed end of the precision filter are sequentially connected 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 pipe of the heat exchanger, and the feed end of the precision filter are connected in sequence through pipelines; forming a forced circulation loop.

13. Use of the cleaning method according to any one of claims 1 to 8 or the cleaning system according to any one of claims 9 to 12 in cleaning of precision filters, preferably in cleaning of precision filters used for filtering spinning solution.

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