A viscose fiber alkaline solution purification treatment device and method

Abstract

This invention relates to a viscose fiber alkaline solution purification device and method. The viscose fiber alkaline solution purification device includes a plate and frame filter, a metal filter, an ultrafine filter, and a nanofiltration membrane filter. The outlet of the plate and frame filter is connected to the inlet of the metal filter, the outlet of the metal filter is connected to the inlet of the ultrafine filter, and the outlet of the ultrafine filter is connected to the inlet of the nanofiltration membrane filter. This invention fundamentally solves the problems of diverse pulp varieties and high hemicellulose content in viscose fiber production, which makes the use of raw materials difficult. It broadens the range of raw material applications and has a positive promoting effect on the development of viscose enterprises.

Description

Technical Field

[0001] This invention belongs to the field of viscose high-purity fiber production technology, specifically relating to a viscose fiber alkaline solution purification treatment device and method. Background Technology

[0002] With the increasing demand for high-whiteness fibers in medical materials and high-end clothing fabrics, viscose companies are paying more and more attention to the quality of high-whiteness fiber products. However, how to obtain highly clean alkaline solutions directly affects the quality of viscose produced in the viscose manufacturing workshop. Currently, some viscose companies have adopted a combination of plate and frame filters, microporous filters, and nanofiltration membranes to process liquid alkali. However, the ordinary use of plate and frame filters and microporous filters alone cannot obtain highly clean nanofiltration membrane pretreatment alkaline solutions, resulting in severe fouling of nanofiltration membranes and short service life. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a viscose fiber alkaline solution purification device, which fundamentally solves the issues of diverse pulp varieties and high hemicellulose content in viscose fiber production, making its use difficult. This expands the range of raw material applications and has a positive impact on the development of viscose enterprises.

[0004] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: The viscose fiber alkaline solution purification treatment device includes a plate and frame filter, a metal filter, an ultra-micro filter and a nanofiltration membrane filter. The outlet of the plate and frame filter is connected to the inlet of the metal filter, the outlet of the metal filter is connected to the inlet of the ultra-micro filter, and the outlet of the ultra-micro filter is connected to the inlet of the nanofiltration membrane filter.

[0005] Beneficial effects:

[0006] The process involves sequentially filtering the alkali liquor from the viscose fiber production workshop through a plate and frame filter press, a fully automatic metal filter, an ultra-micro filter, and a nanofiltration membrane. This highly purified alkali liquor treatment significantly improves the pretreatment of alkali liquor by nanofiltration membranes, extends their service life, and reduces overall nanofiltration membrane procurement costs. Furthermore, it breaks through the quality constraints of viscose fiber pulp, expands the application of semi-fiber high-density pulp, and promotes and guides the healthy development of the entire viscose fiber industry.

[0007] Preferably, the plate and frame filter is a two-stage cross plate and frame filter structure, with the first-stage plate and frame filter cloth being transverse and the second-stage plate and frame filter cloth being longitudinal.

[0008] The beneficial effects of adopting the above-mentioned further solution are that the two-stage cross-plate and frame filter method solves the short circuit problem of the first-stage plate and frame filter and the second-stage plate and frame filter serves as protection. Secondly, by using the first-stage plate and frame filter cloth as the transverse direction and the second-stage plate and frame filter cloth as the longitudinal direction, fibers with different flow directions are intercepted, thereby further improving the plate and frame filter effect.

[0009] Preferably, the filter screen of the metal filter is made of stainless steel woven mesh, and the diameter of the filter screen is 10μm-20μm.

[0010] The beneficial effect of adopting the above-mentioned further scheme is that it mainly forms a uniform and dense filter cake through self-circulation, and the filtration accuracy can reach 5μm-8μm through the filter cake filtration.

[0011] Preferably, the system further includes a security filter disposed between the ultrafiltration unit and the nanofiltration membrane filter, wherein the inlet of the security filter is connected to the outlet of the ultrafiltration unit and the outlet of the security filter is connected to the inlet of the nanofiltration membrane filter.

[0012] The beneficial effect of adopting the above-mentioned further solutions is to extend the service life of nanofiltration membranes and further remove fine particles from alkaline solutions.

[0013] A second objective of this invention is to provide a method for purifying viscose fiber alkaline solution using the aforementioned viscose fiber alkaline solution purification device, comprising the following steps:

[0014] S1: Pressed alkali is filtered by a plate and frame filter press, and larger pieces of alkali are intercepted to obtain primary alkali solution;

[0015] S2: The primary alkaline solution enters a metal filter to remove larger particles, resulting in the secondary alkaline solution.

[0016] S3: Clean the metal filter, mix the resulting metal filter cleaning solution with pressing alkali as the feed liquid for the plate and frame filter, and repeat step S1.

[0017] S4: The secondary alkaline solution enters the ultrafiltration machine for filtration to remove fine particles in the alkaline solution, resulting in the tertiary alkaline solution;

[0018] S5: Clean the ultra-micro filter, and mix the obtained ultra-micro filter cleaning solution with the primary alkaline solution as the feed solution for the metal filter. Repeat step S2.

[0019] S6: The three-stage alkaline solution enters the nanofiltration membrane filter for filtration, removing semi-fiber impurities and obtaining clean alkaline solution.

[0020] Beneficial effects:

[0021] The process involves sequentially filtering the alkali liquor from the viscose fiber production workshop through a plate and frame filter press, a fully automatic metal filter, an ultra-micro filter, and a nanofiltration membrane. This results in a highly purified alkali liquor treatment process that significantly improves the pretreatment of alkali liquor by nanofiltration membranes, extends the service life of nanofiltration membranes, and reduces the company's overall nanofiltration membrane procurement costs. Furthermore, it breaks through the quality constraints of viscose fiber pulp, expands the application of semi-fiber high-density pulp, and promotes and guides the healthy development of the entire viscose fiber industry.

[0022] Preferably, in step S2, the metal filter forms a filter cake through self-circulation and uses the filter cake for filtration, achieving a precision of 5μm-8μm.

[0023] The beneficial effect of adopting the above-mentioned further solution is that the filtration effect is good.

[0024] Preferably, in step S2, the metal filter is a fully automatic cleaning device, and there is a pressure difference between the inlet and outlet of the metal filter. In step S3, the metal filter cleaning fluid is a secondary alkaline solution obtained by filtering the metal filter to clean the metal filter.

[0025] The advantages of adopting the above-mentioned further solution are good filtration effect, using the filtrate from each step of the filter as the cleaning liquid, no consumption of production water, and easy operation as it only uses a plate and frame filter press for slag removal.

[0026] Preferably, in step S4, the particle size of the fine particles filtered by the ultrafiltration machine is 1μm-3μm.

[0027] The beneficial effect of adopting the above-mentioned further solution is that the filtrate from the metal filter is filtered by ultrafiltration to remove fine impurities, resulting in a good filtration effect.

[0028] Preferably, in step S5, the ultrafiltration machine is cleaned with the three-stage alkaline solution obtained by the ultrafiltration machine.

[0029] The beneficial effect of adopting the above-mentioned further solution is that the tertiary alkaline solution obtained by ultrafiltration is used as a cleaning solution and mixed with the primary alkaline solution for filtration again, thereby improving the filtration effect.

[0030] Preferably, in step S6, the tertiary alkaline solution passes through a security filter and enters a nanofiltration membrane filter.

[0031] The beneficial effects of adopting the above-mentioned further solutions are to improve the purity of the alkaline solution entering the nanofiltration membrane, while adding a security filter to cope with unexpected production situations. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0034] Example 1:

[0035] like Figure 1As shown in this embodiment, a viscose fiber alkaline solution purification treatment device includes a plate and frame filter, a metal filter, an ultra-micro filter, and a nanofiltration membrane filter. The outlet of the plate and frame filter is connected to the inlet of the metal filter, the outlet of the metal filter is connected to the inlet of the ultra-micro filter, and the outlet of the ultra-micro filter is connected to the inlet of the nanofiltration membrane filter.

[0036] The beneficial effects of this embodiment are as follows: the alkaline solution from the viscose fiber production workshop is sequentially filtered through a plate and frame filter press, a fully automatic metal filter press, an ultra-micro filter press, and a nanofiltration membrane to obtain a high-purity alkaline solution treatment process. This greatly improves the pretreatment of alkaline solution by nanofiltration membranes, extends the service life of nanofiltration membranes, and reduces the overall procurement cost of nanofiltration membranes. At the same time, it can break the quality constraints of viscose fiber pulp, expand the application of semi-fiber high-quality pulp, and promote and guide the healthy development of the entire viscose fiber industry.

[0037] Among them, the liquid alkali flow rate in the glue-making workshop of the single-line 60,000-ton viscose fiber production line is 80m³. 3 / h-90m 3 / h, temperature is 50℃-53℃, hemicellulose content is 32%-34%.

[0038] Example 2

[0039] Preferably, based on Example 1, the plate and frame filter is a two-stage cross plate and frame filter structure, with the first-stage plate and frame filter cloth being transverse and the second-stage plate and frame filter cloth being longitudinal.

[0040] The beneficial effects of this embodiment are: by adopting a two-stage cross-plate and frame series method, firstly, it solves the problem of short circuit in the first-stage plate and frame filtration, and secondly, it uses the first-stage plate and frame filter cloth as the transverse direction and the second-stage plate and frame filter cloth as the longitudinal direction to intercept fibers flowing in different directions, thereby further improving the plate and frame filtration effect.

[0041] The precision of the filter cloth in the plate and frame filter press is between 20μm and 30μm.

[0042] It should be noted that, since the pressing process involves pressing the soaked pulp to extract alkali, the extracted alkali inevitably contains unreacted fibers and incompletely reacted lumps. Currently, the viscose industry uses a single-stage plate and frame filter press for alkali extraction. Considering the clogging caused by lumps, frequent table turning and cleaning, and the susceptibility to short circuits in the first-stage plate and frame filter press, and the fact that fibers are long and strip-shaped, a single-direction filter cloth cannot trap impurities from fibers in multiple directions, thus affecting the filtration effect, a two-stage cross-plate and frame filter press is adopted. This serves two purposes: firstly, it solves the problem of short circuits in the first-stage plate and frame filter press, and secondly, it provides protection. Furthermore, by utilizing the transverse direction of the first-stage plate and frame filter cloth and the longitudinal direction of the second-stage plate and frame filter cloth, fibers flowing in different directions are trapped, further improving the filtration effect of the plate and frame filter press.

[0043] Example 3

[0044] Preferably, based on Examples 1-2, the filter screen of the metal filter is made of stainless steel woven mesh, and the diameter of the filter screen is 10μm-20μm.

[0045] The beneficial effect of this embodiment is that the metal filter screen uses stainless steel woven mesh, and the effective area of ​​the filter screen is 0.5m². 2 The filter screen has a precision of 10μm-20μm and mainly forms a uniform and dense filter cake through self-circulation. Through filter cake filtration, a precision of 5μm-8μm can be achieved.

[0046] Furthermore, the metal filter is a fully automatic device that can perform automatic cleaning. The automatic cleaning of the metal filter is controlled by the pressure difference between the inlet and outlet, with the pressure controlled between 0.8 bar and 1.0 bar.

[0047] Example 4

[0048] Preferably, based on embodiments 1-3, a security filter is further included. The security filter is disposed between the ultrafiltration unit and the nanofiltration membrane filter. The inlet of the security filter is connected to the outlet of the ultrafiltration unit, and the outlet of the security filter is connected to the inlet of the nanofiltration membrane filter.

[0049] The beneficial effects of this embodiment are: the filtrate from the ultrafiltration machine passes through a security filter with a precision of 1μm-3μm and then enters the nanofiltration membrane filter, which improves the purity of the alkaline solution entering the nanofiltration membrane and at the same time increases the security filter to cope with sudden production situations.

[0050] Example 5

[0051] Preferably, based on Examples 1-4, a method for purifying viscose fibers with alkaline solution includes the following steps:

[0052] S1: Pressed alkali is filtered by a plate and frame filter press, and larger pieces of alkali are intercepted to obtain primary alkali solution;

[0053] S2: The primary alkaline solution enters a metal filter to remove larger particles, resulting in the secondary alkaline solution.

[0054] S3: Clean the metal filter, mix the resulting metal filter cleaning solution with pressing alkali as the feed liquid for the plate and frame filter, and repeat step S1.

[0055] S4: The secondary alkaline solution enters the ultrafiltration machine for filtration to remove fine particles in the alkaline solution, resulting in the tertiary alkaline solution;

[0056] S5: Clean the ultra-micro filter, and mix the obtained ultra-micro filter cleaning solution with the primary alkaline solution as the feed solution for the metal filter. Repeat step S2.

[0057] S6: The three-stage alkaline solution enters the nanofiltration membrane filter for filtration, removing semi-fiber impurities and obtaining clean alkaline solution.

[0058] The beneficial effects of this embodiment are as follows: the alkaline solution from the viscose fiber production workshop is sequentially filtered through a plate and frame filter press, a fully automatic metal filter press, an ultra-micro filter press, and a nanofiltration membrane to obtain a high-purity alkaline solution treatment process. This greatly improves the pretreatment of alkaline solution by nanofiltration membranes, extends the service life of nanofiltration membranes, and reduces the company's overall nanofiltration membrane procurement costs. At the same time, it can break the quality constraints of viscose fiber pulp, expand the application of semi-fiber high-quality pulp, and promote and guide the healthy development of the entire viscose fiber industry.

[0059] Among them, the online cleaning of metal filters allows a single unit to achieve continuous production, requiring only a thorough cleaning every 2-3 months.

[0060] Example 6

[0061] Preferably, based on Example 5, in step S2, the metal filter forms a filter cake through self-circulation and uses the filter cake for filtration, with an accuracy of 5μm-8μm.

[0062] The beneficial effect of this embodiment is that it has a good filtration effect.

[0063] Example 7

[0064] Preferably, based on Examples 5-6, in step S2, the metal filter is a fully automatic cleaning device, and the pressure difference between the inlet and outlet of the metal filter enables automatic backwashing. In step S3, the cleaning fluid for the metal filter is a secondary alkaline solution obtained from the filtration of the metal filter to clean the metal filter.

[0065] The advantages of this embodiment are: good filtration effect, automatic backwashing, and easy operation.

[0066] Example 8

[0067] Preferably, based on Examples 5-7, in step S4, the particle size of the fine particles filtered by the ultrafiltration machine is 1μm-3μm.

[0068] The beneficial effect of this embodiment is that the filtrate from the metal filter is filtered through ultrafiltration to remove fine impurities, resulting in a good filtration effect.

[0069] Furthermore, the ultrafiltration unit adopts a tangential cross-flow wide-channel spiral wound membrane, which further increases the filtration flow rate and delays clogging time.

[0070] Example 9

[0071] Preferably, based on Examples 5-8, in step S5, the ultrafiltration machine is cleaned with the three-stage alkaline solution obtained by the ultrafiltration machine.

[0072] The beneficial effect of this embodiment is that the tertiary alkaline solution obtained by ultrafiltration is used as a cleaning solution and mixed with the primary alkaline solution for filtration again, thereby improving the filtration effect.

[0073] Example 10

[0074] Preferably, based on Examples 5-9, in step S6, the tertiary alkaline solution passes through a security filter and enters a nanofiltration membrane filter.

[0075] The beneficial effects of this embodiment are: the filtrate from the ultrafiltration machine passes through a security filter with a precision of 1μm-3μm and then enters the nanofiltration membrane filter, which improves the purity of the alkaline solution entering the nanofiltration membrane and at the same time increases the security filter to cope with sudden production situations.

[0076] It should be noted that both metal filters and ultrafiltration machines require cleaning. Water or other prepared cleaning solutions can be used, but this is not ideal. Using water or fresh alkali solution for cleaning will increase the cost of soft water and fresh alkali solution. At the same time, using the filtrate from each stage as a cleaning solution has the following advantages: first, it reduces the consumption of soft water and fresh alkali; second, it utilizes the temperature of the cleaning solution (around 50°C), reducing the cost of heating soft water and fresh alkali to 50°C.

[0077] The following is a field test experiment:

[0078] Experimental Example 1

[0079] (1) The flow rate of liquid alkali in the rubber-making workshop of a single-line 60,000-ton viscose fiber production line is 80 m³ / h. 3 / h, temperature is 50℃, sodium hydroxide 200g / l, hemicellulose content is 32%, through two-stage cross plate and frame filtration, the first stage plate and frame filter cloth is transverse, the second stage plate and frame filter cloth is longitudinal;

[0080] (2) The filtrate after two-stage plate and frame filter press filtration is directly fed into a metal filter press for filtration treatment;

[0081] (3) The automatic cleaning of the metal filter is controlled by the inlet and outlet pressure difference, with the pressure controlled at 1.0 bar. The effective area of ​​the metal filter screen is 0.5 m². 2 It uses a filter screen with a precision of 10μm, and forms a filter cake through self-circulation of the filter. The filter cake is used for filtration, and the precision can reach 5μm.

[0082] (4) The cleaning solution for metal filters can be mixed with the pressing alkali solution as feed for the secondary frame filter, repeating step (1);

[0083] (5) The filtrate from the metal filter is filtered through ultra-microfiltration to remove fine impurities with a particle size of 1μm, further purifying the alkaline solution.

[0084] (6) The cleaning solution of the ultrafiltration machine is mixed with the filtrate of the plate and frame filter press and used as the feed liquid of the ultrafiltration machine, repeating step (2);

[0085] (7) The filtrate from the ultrafiltration machine passes through a security filter with a precision of 1μm and enters the nanofiltration membrane treatment system to ensure that the alkaline solution entering the nanofiltration membrane is clean, reduce nanofiltration membrane fouling, extend the service life of the nanofiltration membrane from 3 years to 5 years, and raise the alkaline solution hemicellulose in the glue-making system to 35%, achieving stable production.

[0086] Among them, the clean alkaline solution obtained by nanofiltration membrane treatment is a high-purity alkaline solution that is reused in the impregnation system, and the nanofiltration membrane concentrate is used as a dissolving alkali for preparation and reuse in the system.

[0087] Experiment Example 2

[0088] (1) The flow rate of liquid alkali in the rubber-making workshop of a single-line 60,000-ton viscose fiber production line is 90 m³ / h. 3 / h, temperature is 53℃, sodium hydroxide 220g / l, hemicellulose content is 34%, through two-stage cross plate and frame filtration, the first stage plate and frame filter cloth is transverse, the second stage plate and frame filter cloth is longitudinal;

[0089] (2) The filtrate after two-stage plate and frame filter press filtration is directly fed into a metal filter press for filtration treatment;

[0090] (3) The automatic cleaning of the metal filter is controlled by the inlet and outlet pressure difference, with the pressure controlled at 0.8 bar and the effective area of ​​the metal filter screen being 0.5 m². 2 It uses a filter screen with a resolution of 20μm, and forms a filter cake through self-circulation of the filter. The filter cake is used for filtration, and the resolution can reach 8μm.

[0091] (4) The cleaning solution for metal filters can be mixed with pressing alkali as feed for secondary frame filters, repeating step (1);

[0092] (5) The filtrate from the metal filter is filtered through ultra-microfiltration to remove fine impurities with a particle size of 3μm, further purifying the alkaline solution.

[0093] (6) The cleaning solution of the ultrafiltration machine is mixed with the filtrate of the plate and frame filter press and used as the feed liquid of the ultrafiltration machine, repeating step (2);

[0094] (7) The filtrate from the ultrafiltration machine passes through a security filter with a precision of 3μm before entering the nanofiltration membrane treatment system, ensuring that the alkaline solution entering the nanofiltration membrane is clean, reducing nanofiltration membrane fouling, and extending the service life of the nanofiltration membrane.

[0095] Among them, the clean alkaline solution obtained by nanofiltration membrane treatment is a high-purity alkaline solution that is reused in the impregnation system, and the nanofiltration membrane concentrate is used as a dissolving alkali for preparation and reuse in the system.

[0096] Experimental Example 3

[0097] (1) The flow rate of liquid alkali in the rubber-making workshop of a single-line 60,000-ton viscose fiber production line is 85 m³ / h. 3 / h, temperature is 52℃, sodium hydroxide 210g / l, hemicellulose content is 35%, through two-stage cross plate and frame filtration, the first stage plate and frame filter cloth is transverse, the second stage plate and frame filter cloth is longitudinal;

[0098] (2) The filtrate after two-stage plate and frame filter press filtration is directly fed into a metal filter press for filtration treatment;

[0099] (3) The automatic cleaning of the metal filter is controlled by the inlet and outlet pressure difference, with the pressure controlled at 0.9 bar and the effective area of ​​the metal filter screen being 0.5 m². 2 It uses a filter screen with a resolution of 15μm, and forms a filter cake through self-circulation of the filter. The filter cake is then used for filtration, and the resolution can reach 7μm.

[0100] (4) The cleaning solution for metal filters can be mixed with pressing alkali as feed for secondary frame filters, repeating step (1);

[0101] (5) The filtrate from the metal filter is filtered through ultra-microfiltration to remove fine impurities with a particle size of 2μm, further purifying the alkaline solution.

[0102] (6) The cleaning solution of the ultrafiltration machine is mixed with the filtrate of the plate and frame filter press and used as the feed liquid of the ultrafiltration machine, repeating step (2);

[0103] (7) The filtrate from the ultrafiltration machine passes through a security filter with a precision of 2μm before entering the nanofiltration membrane treatment system. This ensures that the alkaline solution entering the nanofiltration membrane is clean, reduces nanofiltration membrane fouling, and extends the service life of the nanofiltration membrane.

[0104] Among them, the clean alkaline solution obtained by nanofiltration membrane treatment is a high-purity alkaline solution that is reused in the impregnation system, and the nanofiltration membrane concentrate is used as a dissolving alkali for preparation and reuse in the system.

[0105] Comparative Example

[0106] The flow rate of liquid alkali in the rubber-making workshop of a single 60,000-ton viscose fiber production line is 85 m³ / h. 3 The process involves a filter press, a microporous filter, a security filter, and a nanofiltration membrane. The filter is made of high-molecular-weight polypropylene. The replacement cost for a single 80m² filter is 12,000 yuan, and 12 filters need to be replaced annually. Furthermore, the replacement of the lower filter rod is classified as hazardous solid waste, with a disposal cost of 3,000 yuan per unit. This process is also harmful to the environment, and the replacement and disassembly require significant manpower.

[0107] Among them, the plate and frame filter uses a single-stage plate and frame filter. The filtrate at the outlet of the plate and frame filter is tested and the particle size is above 20μm. Occasionally, short circuits occur. In order to ensure the normal operation of the nanofiltration membrane filter, the plate and frame filter cleaning cycle is 1 day.

[0108] Compared with the comparative example, the present invention:

[0109] This invention only produces solid waste residue from plate and frame filter presses, which is classified as solid waste. Other consumables, such as metal filter screens and ultra-micro filter screens, have a service life of more than one year and are made of metal. They can be disposed of as solid waste under normal circumstances. The process is more reasonable. At the same time, due to the improved pretreatment process of nanofiltration membrane filters, the service life of nanofiltration membranes is extended from 3 years to more than 5 years.

[0110] This application employs a two-stage cross-plate and frame filtration system. The first-stage plate and frame filter cloth is transverse, and the second-stage plate and frame filter cloth is longitudinal. The filtrate particle size distribution is less than 15μm. Due to the high cleanliness of the filtrate after passing through the two-stage plate and frame system, the nanofiltration membrane's operating cycle is extended. The cleaning cycle of the first-stage plate and frame is greater than 3 days, and the cleaning cycle of the second-stage first-stage plate and frame is greater than 7 days.

[0111] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying viscose fiber with alkaline solution, characterized in that, The viscose fiber alkaline solution purification treatment device includes the following steps: S1: Pressed alkali is filtered by a plate and frame filter press, and larger pieces of alkali are intercepted to obtain primary alkali solution; S2: The primary alkaline solution enters a metal filter to remove larger particles, resulting in the secondary alkaline solution. S3: Clean the metal filter, mix the resulting metal filter cleaning solution with pressing alkali as the feed liquid for the plate and frame filter, and repeat step S1. S4: The secondary alkaline solution enters the ultrafiltration machine for filtration to remove fine particles in the alkaline solution, resulting in the tertiary alkaline solution; S5: Clean the ultra-micro filter, and mix the obtained ultra-micro filter cleaning solution with the primary alkaline solution as the feed solution for the metal filter. Repeat step S2. S6: The three-stage alkaline solution enters the nanofiltration membrane filter for filtration, removing semi-fiber impurities to obtain a clean alkaline solution; In step S2, the metal filter forms a filter cake through self-circulation and uses the filter cake for filtration, with an accuracy of 5μm-8μm. In step S6, the tertiary alkaline solution is treated by a security filter and then enters a nanofiltration membrane filter. The viscose fiber alkaline solution purification and treatment device includes a plate and frame filter, a metal filter, an ultra-micro filter, and a nanofiltration membrane filter. The outlet of the plate and frame filter is connected to the inlet of the metal filter, the outlet of the metal filter is connected to the inlet of the ultra-micro filter, and the outlet of the ultra-micro filter is connected to the inlet of the nanofiltration membrane filter. The plate and frame filter is a two-stage cross plate and frame filter structure, with the first-stage plate and frame filter cloth being transverse and the second-stage plate and frame filter cloth being longitudinal. The filter screen of the metal filter is made of stainless steel woven mesh, and the diameter of the filter screen is 10μm-20μm. It also includes a security filter, which is disposed between the ultrafiltration unit and the nanofiltration membrane filter. The inlet of the security filter is connected to the outlet of the ultrafiltration unit, and the outlet of the security filter is connected to the inlet of the nanofiltration membrane filter.

2. The method for purifying viscose fiber with alkaline solution according to claim 1, characterized in that: In step S3, the metal filter is a fully automatic cleaning device. There is a pressure difference between the inlet and outlet of the metal filter. In step S3, the metal filter cleaning fluid is a secondary alkaline solution obtained by filtering the metal filter to clean the metal filter.

3. The method for purifying viscose fiber with alkaline solution according to claim 1, characterized in that: In step S4, the particle size of the fine particles filtered by the ultrafiltration machine is 1μm-3μm.

4. The method for purifying viscose fiber with alkaline solution according to claim 1, characterized in that: In step S5, the ultrafiltration machine is cleaned with the three-stage alkaline solution obtained by ultrafiltration.

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