A carbon fiber solvent recovery pretreatment system and pretreatment method

Abstract

The application discloses a carbon fiber solvent recovery pretreatment system and a pretreatment method. The pretreatment system comprises a buffer tank, a buffer tank discharge pump, a first-stage filter unit, a second-stage filter unit, an ion exchange column feed pump, an ion exchange unit, an online metal ion analyzer, an ion exchange column discharge pump and a third-stage filter unit. The discharge port of the buffer tank is connected to the feed port of the first-stage filter unit through the buffer tank discharge pump. The discharge port of the first-stage filter unit is connected to the feed port of the second-stage filter unit. The discharge port of the second-stage filter unit is connected to the feed port of the ion exchange unit through the ion exchange column feed pump.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber production technology, and more specifically, to a carbon fiber solvent recovery pretreatment system and pretreatment method. Background Technology

[0002] In the carbon fiber production process, polyacrylonitrile (PAN) precursor fibers are typically spun in a dimethyl sulfoxide (DMSO)-water mixed solvent system. To reduce production costs and meet environmental protection requirements, the industry generally adopts processes such as distillation and multi-effect evaporation to recover and reuse the H2O, DMSO, and AN mixed solvent after spinning.

[0003] In the solvent recovery process, the solution contains high-boiling-point substances composed of low-molecular-weight polyacrylonitrile (PAN) from the polymerization and spinning stages, as well as DMSO decomposition products. When heated during recovery, these high-boiling-point substances generate a complex, highly viscous, black, tar-like mixture. Furthermore, metal ions from raw materials, catalysts, equipment corrosion, or process water also affect recovery efficiency. For example, iron ions catalyze the decomposition of AN (acetic acid) and form complexes with DMSO, significantly exacerbating coking and carbonization. These byproducts continuously deposit and coke on the inner walls of critical equipment prone to dead zones, such as reboilers and heat exchangers, forming a black scale layer. This leads to a severe decrease in heat transfer efficiency, an increase in system pressure differential, and frequent blockages in reboiler tubes and pipelines, forcing production line shutdowns for manual or chemical cleaning. This not only significantly increases equipment maintenance costs and safety risks but also severely impacts production continuity and economic efficiency due to the interruption of solvent recovery.

[0004] Currently, the industry generally focuses on optimizing the recycling process itself, or using adsorption beds to remove metal ions, but this cannot meet the requirements for continuous operation. There is a lack of effective pretreatment methods to remove these specific fouling precursors online before the solution enters the main recycling system. Therefore, developing a control and pretreatment system that can achieve continuous production and prevent or significantly reduce clogging in the recycling section from the source has become a key technical problem that urgently needs to be solved to improve the operational stability of solvent recycling in carbon fiber production, reduce maintenance costs, and achieve long-term stable operation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a carbon fiber solvent recovery pretreatment system and pretreatment method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention discloses a carbon fiber solvent recovery pretreatment system, comprising a buffer tank, a buffer tank discharge pump, a primary filtration unit, a secondary filtration unit, an ion exchange column feed pump, an ion exchange unit, an online metal ion analyzer, an ion exchange column discharge pump, and a tertiary filtration unit. The discharge port of the buffer tank is connected to the inlet of the primary filtration unit via the buffer tank discharge pump. The discharge port of the primary filtration unit is connected to the inlet of the secondary filtration unit. The discharge port of the secondary filtration unit is connected to the inlet of the ion exchange unit via the ion exchange column feed pump. The discharge port of the ion exchange unit is connected to the online metal ion analyzer. The online metal ion analyzer is connected to the inlet of the tertiary filtration unit via the ion exchange column discharge pump. The discharge port of the tertiary filtration unit is connected to a subsequent solvent recovery system.

[0008] Preferably, the primary filtration unit consists of primary filter A and primary filter B connected in parallel, the secondary filtration unit consists of secondary filter A and secondary filter B connected in parallel, the ion exchange unit consists of ion exchange column A and ion exchange column B connected in parallel, and the tertiary filtration unit consists of tertiary filter A and tertiary filter B connected in parallel.

[0009] Preferably, the filtration accuracy of primary filter A and primary filter B is 50-100 μm, the filtration accuracy of secondary filter A and secondary filter B is 15-25 μm, and the filtration accuracy of tertiary filter A and tertiary filter B is 1-5 μm.

[0010] Preferably, the primary, secondary, and tertiary filtration units are each equipped with a differential pressure detector and a three-way switching valve. The differential pressure detector is used to detect the pressure difference between the inlet and outlet of the corresponding filtration unit. The three-way switching valve switches between the two filters in each filtration unit according to the signal output by the differential pressure detector. The switching time is less than 30 seconds, and the system pressure drop fluctuation is less than 5%.

[0011] Preferably, ion exchange columns A and B are filled with macroporous aminophosphonic acid chelated cation exchange resin, and the throughput of a single column is 0.5–5.0 m³. 3 / h, empty bed flow rate is 2~10BV / h, resin bed height is 800~3000mm, bed height-to-diameter ratio is 2:1~6:1, and bed operating pressure difference is 0.02~0.15MPa.

[0012] Preferably, the system also includes an ion exchange unit switching valve. The online metal ion analyzer is interlocked with the ion exchange unit switching valve. When the online metal ion analyzer detects that the outlet metal ion concentration is greater than a preset value, it controls the ion exchange unit switching valve to switch from ion exchange column A to ion exchange column B or from ion exchange column B to ion exchange column A.

[0013] Preferably, ion exchange column A and ion exchange column B are respectively connected to a regeneration pipeline system, which includes a primary water washing pipeline, an acid regeneration pipeline, a secondary water washing pipeline, and a solvent replacement pipeline.

[0014] A pretreatment method for a carbon fiber solvent recovery pretreatment system includes the following steps:

[0015] S1. The recovered solution containing impurities is temporarily stored in a buffer tank and then stirred and homogenized by a stirring mechanism.

[0016] S2, the buffer tank discharge pump pumps the homogenized solution into the primary filtration unit for primary filtration to intercept large-sized low molecular weight PAN gel and initial carbonized particles.

[0017] S3. The solution after primary filtration enters the secondary filtration unit for secondary filtration to remove fine particles and colloidal oligomers.

[0018] S4. The ion exchange column feed pump delivers the solution after secondary filtration to the ion exchange unit to remove metal ions from the solution.

[0019] S5. The solution after ion exchange flows through the online metal ion analyzer and is then pumped by the ion exchange column outlet pump to the three-stage filtration unit for three-stage filtration to remove trace amounts of resin debris and metal compound precipitates. The online metal ion analyzer monitors the metal ion concentration at the outlet of the ion exchange unit in real time.

[0020] S6. The pretreated solution enters the subsequent solvent recovery system.

[0021] Preferably, when the metal ion concentration at the outlet of the ion exchange column reaches the set threshold, regeneration is performed according to the following steps:

[0022] S101, First wash: Use deionized water or process water for replacement cleaning, with a water volume of 2-7 BV and a water flow rate of 1-4 BV / h, until the DMSO concentration in the effluent is less than 1 wt%.

[0023] S102. Acid Regeneration: Regeneration is performed using a 4%–8% hydrochloric acid solution. The acid volume is 2–7 BV, the acid flow rate is 0.5–2 BV / h, and the acid temperature is controlled at 20–40℃. During acid regeneration, metal ions adsorbed on the aminophosphonic acid groups are converted by H+. + The acid regeneration waste liquid is replaced and then enters the regeneration waste liquid. The acid regeneration waste liquid is collected separately and then enters the metal-containing acidic waste liquid treatment system.

[0024] S103, Secondary water washing: Deionized water is used for washing, with a water volume of 2-7 BV and a flow rate of 1-4 BV / h, until the pH of the effluent reaches 7.0 and the conductivity tends to stabilize.

[0025] S104 Solvent replacement: Replacement is performed using DMSO aqueous solutions of progressively increasing concentrations. DMSO aqueous solutions are sequentially introduced at a flow rate of 1-3 BV / h and a replacement temperature of 30-60℃. Replacement is completed when the DMSO concentration in the effluent does not deviate from the feed concentration by more than ±0.5wt%, the pH does not deviate from the feed concentration by more than ±0.3%, and the conductivity does not deviate from the feed conductivity by more than ±5%.

[0026] The beneficial effects of this invention are: 1. The pretreatment process combining three-stage gradient filtration and ion exchange is adopted. Before the solution enters the main recovery system, the first-stage filter intercepts large-size low-molecular-weight PAN gel and initial carbonized particles, the second-stage filter retains fine particles and colloidal oligomers, the ion exchange column removes metal ions that catalyze coking, and the third-stage filter retains trace amounts of resin debris and metal compound precipitates. This removes two types of coking precursors from the source at the same time, greatly reducing coking deposits on the inner wall of the recovery equipment.

[0027] 2. The three-stage filtration unit and ion exchange unit of the present invention are both configured in parallel and automatically switched by signal triggering from differential pressure detector or online metal ion analyzer. The switching time is less than 30 seconds and the system pressure drop fluctuation is less than 5%, realizing true continuous online operation without stopping to replace filter elements or regenerate resin, thus meeting the requirements of continuous production.

[0028] 3. The buffer tank of the present invention is equipped with a multi-layer stirring structure. The bottom stirring blade and the vertical stirring rod work together to stir the liquid at the bottom, the auxiliary stirring blade stirs the liquid above, and the horizontal stirring blade assists in stirring the inner middle area, so that the liquid at all heights in the tank is effectively stirred, avoiding local solid content fluctuations that could cause instantaneous clogging of the subsequent filter. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the system of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of one embodiment of the buffer container of the present invention;

[0031] Figure 3 This is a schematic diagram of another embodiment of the buffer container of the present invention;

[0032] Figure 4 for Figure 3 Enlarged view of point A in the middle;

[0033] Figure 5 for Figure 3 Enlarged view of point B in the middle;

[0034] Figure 6 for Figure 3 Enlarged diagram of point C in the middle.

[0035] Reference numerals: 1. Buffer tank; 101. Tank body; 102. Motor frame; 103. Stirring motor; 104. Drive shaft; 105. Bottom stirring blade; 106. Vertical stirring rod; 107. Fixing sleeve; 108. Horizontal stirring blade; 109. Collar ring; 110. Auxiliary stirring blade; 111. Retaining ring; 112. Guide strip; 113. Sleeve; 114. Guide hole; 115. Lifting sleeve; 116. Guide rod; 117. Mounting ring groove; 118. Suspension component; 119. Winding rope; 120. Mounting frame; 121. Winding reel; 122. Winding motor 1. Machine; 123. Guide wheel; 124. Drive shaft; 125. Driven gear; 126. Mounting chamber; 127. Rotating shaft; 128. Drive gear; 129. Worm gear; 130. Adjusting motor; 131. Worm; 2. Buffer tank discharge pump; 3. Primary filter A; 4. Primary filter B; 5. Secondary filter A; 6. Secondary filter B; 7. Ion exchange column feed pump; 8. Ion exchange column A; 9. Ion exchange column B; 10. Online metal ion analyzer; 11. Ion exchange column discharge pump; 12. Tertiary filter A; 13. Tertiary filter B. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 As shown, a carbon fiber solvent recovery pretreatment system includes a buffer tank 1, a buffer tank discharge pump 2, a primary filtration unit, a secondary filtration unit, an ion exchange column feed pump 7, an ion exchange unit, an online metal ion analyzer 10, an ion exchange column discharge pump 11, and a tertiary filtration unit.

[0038] The outlet of the buffer tank 1 is connected to the inlet of the primary filtration unit via the buffer tank discharge pump 2. The outlet of the primary filtration unit is connected to the inlet of the secondary filtration unit. The outlet of the secondary filtration unit is connected to the inlet of the ion exchange unit via the ion exchange column feed pump 7. The outlet of the ion exchange unit is connected to the online metal ion analyzer 10. The online metal ion analyzer 10 is connected to the inlet of the tertiary filtration unit via the ion exchange column discharge pump 11. The outlet of the tertiary filtration unit is connected to the subsequent solvent recovery system.

[0039] The primary filtration unit consists of primary filters A3 and B4 connected in parallel; the secondary filtration unit consists of secondary filters A5 and B6 connected in parallel; the ion exchange unit consists of ion exchange columns A8 and B9 connected in parallel; and the tertiary filtration unit consists of tertiary filters A12 and B13 connected in parallel.

[0040] Primary filters A3 and B4 have a filtration precision of 50–100 μm, responsible for intercepting large particles. The solids in the solution are mainly low molecular weight PAN gel and initially carbonized particles. Secondary filters A5 and B6 have a filtration precision of 15–25 μm, further intercepting finer particles and some colloidal oligomers. Tertiary filters A12 and B13 have a filtration precision of 1–5 μm, intercepting trace amounts of resin, metal compound precipitates, or colloids carried by the solution after ion exchange, ensuring that the liquid finally entering the distillation column is free of particles. All parts in contact with materials are lined with 316L stainless steel or PTFE.

[0041] Each filter unit is equipped with a differential pressure detector and a three-way switching valve. The differential pressure detector detects the pressure difference between the inlet and outlet of the corresponding filter unit. The three-way switching valve switches between the two filters in the filter unit based on the signal output by the differential pressure detector, with a switching time of less than 30 seconds and a system pressure drop fluctuation of less than 5%. The differential pressure warning value for the first-stage filter is 0.12–0.20 MPa, for the second-stage filter it is 0.10–0.15 MPa, and for the third-stage filter it is 0.08–0.12 MPa.

[0042] Ion exchange columns A8 and B9 are filled with macroporous aminophosphonic acid chelated cation exchange resin, where phosphonic acid groups react with Fe... 3+ Ca 2+ Mg 2+ Stable coordination complexes are formed, and cation exchange occurs simultaneously. The macroporous structure provides strong resistance to organic fouling. The throughput of a single ion exchange column is 0.5–5.0 m³. 3 The empty bed flow rate is 2–10 BV / h, the resin bed height is 800–3000 mm, the bed height-to-diameter ratio is 2:1–6:1, and the bed operating pressure difference is 0.02–0.15 MPa. When the pressure difference rises to 0.18–0.25 MPa or the outlet metal ion concentration reaches the set threshold, the system switches to the standby ion exchange column and regenerates the saturated resin.

[0043] The online metal ion analyzer 10 is interlocked with the switching valve of the ion exchange unit. The valve switching is achieved by a PLC receiving the metal ion concentration signal and controlling the explosion-proof solenoid valve to drive the pneumatic switching valve. When the online metal ion analyzer 10 detects that the outlet metal ion concentration is greater than 5 ppm, it automatically switches to another set of ion exchange resin columns after continuous confirmation and regenerates the current ion exchange resin column.

[0044] Ion exchange columns A8 and B9 are each connected to a regeneration pipeline system, which includes a primary water wash pipeline, an acid regeneration pipeline, a secondary water wash pipeline, and a solvent replacement pipeline. By incorporating primary water wash, acid regeneration, secondary water wash, and solvent replacement steps, direct contact between the acid regeneration solution and the DMSO / acrylonitrile system can be avoided, reducing side reactions and safety risks. Simultaneously, this ensures that the resin maintains stable metal removal capabilities and low bed resistance even after multiple regeneration cycles.

[0045] like Figure 2 As shown, the buffer tank 1 includes a tank body 101 and a stirring motor 103. The stirring motor 103 is mounted on the top of the tank body 101 via a motor frame 102. The stirring motor 103 is driven by a drive shaft 104 via a coupling. The lower end of the drive shaft 104 extends into the tank body 101. Several bottom stirring blades 105 are connected to the outer periphery of the bottom end of the drive shaft 104. The bottom stirring blades 105 are horizontally arranged, and a vertical stirring rod 106 is connected to the end of the bottom stirring blades 105 away from the drive shaft 104. The vertical stirring rod 106 is vertically arranged and extends upward. The tank body 101 is made of 316L stainless steel, and the stirring speed is controlled at 40 r / min to ensure uniform distribution of DMSO, water, acrylonitrile, and suspended oligomers in the solution, avoiding instantaneous clogging of the subsequent filter due to local fluctuations in solid content.

[0046] Two retaining rings 111 are mounted on the drive shaft 104, with the lower retaining ring 111 positioned higher than the upper end of the vertical stirring rod 106. A guide bar 112 is mounted on the outer periphery of the drive shaft 104 between the two retaining rings 111, and the guide bar 112 is arranged axially along the drive shaft 104. A collar 109 is fitted onto the drive shaft 104, positioned between the two retaining rings 111. A guide groove is formed on the inner side of the collar 109 to mate with the guide bar 112. An auxiliary stirring blade 110 is connected to the outer periphery of the collar 109, and the auxiliary stirring blade 110 is inclined.

[0047] The collar 109 and auxiliary stirring blades 110 are made entirely of plastic and can float on the surface of the liquid inside the tank 101, rising and falling with the liquid level. The collar 109 rotates with the drive shaft 104 through the cooperation of the guide groove and the guide bar 112, thereby stirring the liquid above. In addition to the stirring of the liquid at the bottom of the tank 101 by the bottom stirring blades 105 and the vertical stirring rod 106, the stirring of the liquid above is added, so that the liquid at all heights in the tank 101 is effectively stirred.

[0048] Another implementation of the buffer jar 1 is as follows: Figure 3 As shown, a sleeve 113 is installed on the inner wall of the top of the tank 101, and a drive shaft 104 passes through the sleeve 113. A guide hole 114 is provided inside the sleeve 113, which is axially aligned with the sleeve 113, and its lower end is connected to the lower end face of the sleeve 113. A lifting sleeve 115 is fitted onto the drive shaft 104, located below the sleeve 113. A guide rod 116 is connected to the upper end of the lifting sleeve 115, and its upper end extends into the guide hole 114, with the guide rod 116 slidingly engaging with the guide hole 114.

[0049] like Figure 4 As shown, a collar 109 is fitted onto the drive shaft 104, and the collar 109 is located below the lifting sleeve 115. A mounting groove 117 is formed at the lower end of the lifting sleeve 115, and a suspension member 118 is installed within the mounting groove 117. The suspension member 118 can rotate around the drive shaft 104 within the mounting groove 117, and its lower end is connected to the upper end face of the collar 109. A guide bar 112 is connected to the outer periphery of the drive shaft 104, and the guide bar 112 is arranged along the axial direction of the drive shaft 104. A guide groove that mates with the guide bar 112 is formed within the collar 109.

[0050] One of the guide rods 116 has a winding rope 119 connected to its upper end, such as... Figure 5 As shown, a mounting frame 120 is installed on the tank body 101, and a winding motor 122 and a guide wheel 123 are mounted on the mounting frame 120. The winding motor 122 is fixedly mounted on the mounting frame 120, and the winding motor 122 drives a winding wheel 121. The guide wheel 123 is rotatably mounted on the mounting frame 120. The other end of the winding rope 119 passes through the tank body 101, passes around the guide wheel 123, and is wound around the winding wheel 121.

[0051] The winding motor 122 drives the winding wheel 121 to rotate forward and backward, thereby winding and unwinding the winding rope 119. This causes the collar 109 to rise and fall along the drive shaft 104, adjusting the auxiliary stirring blades 110 to different heights within the tank 101. The position of the auxiliary stirring blades 110 in the liquid can be adjusted according to stirring requirements, stirring the liquid at corresponding heights and avoiding insufficient stirring at different heights, ensuring effective stirring of the liquid throughout. The suspension component 118 allows the collar 109 to rotate with the drive shaft 104 even when the lifting sleeve 115 does not rotate with the drive shaft 104.

[0052] A fixing sleeve 107 is installed at the middle of the drive shaft 104, and a transverse stirring blade 108 is installed on the outer periphery of the fixing sleeve 107. The transverse stirring blade 108 is inclined. The transverse stirring blade 108 is located within the height range of the vertical stirring rod 106. The transverse stirring blade 108 assists in stirring the inner part of the stirring range covered by the vertical stirring rod 106, so that the stirring range can cover most of the liquid.

[0053] like Figure 6 As shown, an installation chamber 126 is provided within the fixed sleeve 107. A drive shaft 124 is connected to the inner end of the transverse stirring blade 108, and the inner end of the drive shaft 124 extends into the installation chamber 126. The drive shaft 124 is rotatably connected to the fixed sleeve 107. A driven gear 125 is connected to one end of the drive shaft 124 that extends into the installation chamber 126. A rotating shaft 127 is rotatably connected within the installation chamber 126. A drive gear 128 and a worm gear 129 are mounted on the rotating shaft 127, and the drive gear 128 meshes with each of the driven gears 125. An adjusting motor 130 is installed within the installation chamber 126, and the adjusting motor 130 drives a worm gear 131, which meshes with the worm gear 129.

[0054] The worm gear 131 is driven to rotate by the motor 130, which in turn drives the drive gear 128 to rotate via the worm wheel 129 and the rotating shaft 127. The drive gear 128, in turn, drives the transverse stirring blade 108 connected to the transmission shaft 124 to rotate through its engagement with the driven gear 125, thereby adjusting the tilt angle of the transverse stirring blade 108. By changing the frontal area of ​​the transverse stirring blade 108 according to the stirring requirements, its stirring force on the liquid can be altered to meet the corresponding stirring needs. After the transverse stirring blade 108 is adjusted to the appropriate angle, the motor 130 stops, thus acting as a brake to keep the angle of the transverse stirring blade 108 fixed.

[0055] The recovered solution stream contains: 71.5 wt.% water, 27.4 wt.% dimethyl sulfoxide, 1 wt.% acrylonitrile, 0.1 wt.% polymer, and 53 ppm metal ions. It is transferred to buffer tank 1 for temporary storage and homogenization. Buffer tank 1 is made of 316L stainless steel and equipped with a stirring mechanism at a speed controlled at 40 rpm. The solution is then pumped through buffer tank discharge pump 2 into primary filter 3 and secondary filter 5, with filtration accuracies of 75 μm and 20 μm respectively, to remove low molecular weight PAN gel, initially carbonized particles, and fine colloids.

[0056] The solution after secondary filtration is fed to ion exchange column 8 by ion exchange column feed pump 7 for ion exchange. Macroporous aminophosphonic acid chelate cation exchange resin is selected, with a resin bed height of 2000 mm, an empty bed flow rate of 4 BV / h, an operating temperature of 65℃, and an operating pressure differential controlled around 0.08 MPa. An online metal ion analyzer 10 monitors the ion removal effect in real time. The subsequent solution is fed to a tertiary filter 12 with a filtration accuracy of 3 μm by ion exchange column discharge pump 11 for final fine filtration before entering the subsequent distillation and recovery system.

[0057] After filtration and ion exchange, the test results showed that: water 71.558 wt.%, DMSO 27.422 wt.%, acrylonitrile 1.001 wt.%, polymer 0.019 wt.%, and metal ions approximately 3 ppm.

[0058] When the metal ion concentration at the ion exchange column outlet reaches the set threshold (i.e., metal ion concentration > 5 ppm), regeneration is performed according to the following steps: First, deionized water is used for flushing and replacement, with a flushing volume of 4.5 BV, a flushing flow rate of 2 BV / h, and a flushing temperature controlled at 40℃, until the DMSO concentration in the effluent is below 1 wt% and the effluent color is basically stable. Then, acid regeneration is performed using a 5.5 wt.% hydrochloric acid solution as the regenerator, with an acid volume of 3 BV, an acid regeneration flow rate of 1 BV / h, and an acid temperature controlled at 35℃. After acid regeneration, a second flushing is performed using deionized water, with a second flushing volume of 4 BV, a flushing flow rate of 2 BV / h, and a flushing temperature controlled at 40℃, until the effluent pH reaches 7.0 and the conductivity tends to stabilize. Finally, solvent replacement and equilibration are performed using a gradient of DMSO aqueous solutions. Approximately 10 wt%, 20 wt%, and 27 wt% DMSO aqueous solutions are sequentially introduced, with each gradient replacement volume being 1 BV. The replacement flow rate is 1.5 BV / h, and the replacement temperature is controlled at approximately 50°C. Replacement continues until the DMSO concentration in the effluent deviates from the feed concentration by no more than ±0.5 wt%, the pH deviates from the feed concentration by no more than ±0.3, and the conductivity deviates from the feed concentration by no more than ±5%. This completes the regeneration of the resin and solvent equilibration. Afterward, the ion exchange column is heated to 65°C and put back into service or put into operation.

[0059] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A carbon fiber solvent recovery pretreatment system, characterized in that, The system includes a buffer tank (1), a buffer tank discharge pump (2), a primary filtration unit, a secondary filtration unit, an ion exchange column feed pump (7), an ion exchange unit, an online metal ion analyzer (10), an ion exchange column discharge pump (11), and a tertiary filtration unit. The discharge port of the buffer tank (1) is connected to the inlet of the primary filtration unit via the buffer tank discharge pump (2). The discharge port of the primary filtration unit is connected to the inlet of the secondary filtration unit. The discharge port of the secondary filtration unit is connected to the inlet of the ion exchange unit via the ion exchange column feed pump (7). The discharge port of the ion exchange unit is connected to the online metal ion analyzer (10). The online metal ion analyzer (10) is connected to the inlet of the tertiary filtration unit via the ion exchange column discharge pump (11). The discharge port of the tertiary filtration unit is connected to the subsequent solvent recovery system.

2. The carbon fiber solvent recovery pretreatment system according to claim 1, characterized in that, The primary filtration unit consists of a primary filter A (3) and a primary filter B (4) connected in parallel. The secondary filtration unit consists of a secondary filter A (5) and a secondary filter B (6) connected in parallel. The ion exchange unit consists of an ion exchange column A (8) and an ion exchange column B (9) connected in parallel. The tertiary filtration unit consists of a tertiary filter A (12) and a tertiary filter B (13) connected in parallel.

3. The carbon fiber solvent recovery pretreatment system according to claim 2, characterized in that, The filtration accuracy of the primary filter A (3) and the primary filter B (4) is 50-100 μm, the filtration accuracy of the secondary filter A (5) and the secondary filter B (6) is 15-25 μm, and the filtration accuracy of the tertiary filter A (12) and the tertiary filter B (13) is 1-5 μm.

4. The carbon fiber solvent recovery pretreatment system according to claim 2, characterized in that, The primary, secondary, and tertiary filtration units are each equipped with a differential pressure detector and a three-way switching valve. The differential pressure detector is used to detect the pressure difference between the inlet and outlet of the corresponding filtration unit. The three-way switching valve switches between the two filters in each filtration unit according to the signal output by the differential pressure detector, with a switching time of less than 30 seconds.

5. The carbon fiber solvent recovery pretreatment system according to claim 2, characterized in that, The ion exchange columns A (8) and B (9) are filled with macroporous aminophosphonic acid chelating cation exchange resin, and the single-column throughput of ion exchange columns A (8) and B (9) is 0.5–5.0 m³. 3 / h, empty bed flow rate is 2~10BV / h, resin bed height is 800~3000mm, bed height-to-diameter ratio is 2:1~6:1, and bed operating pressure difference is 0.02~0.15MPa.

6. The carbon fiber solvent recovery pretreatment system according to claim 2, characterized in that, It also includes an ion exchange unit switching valve. The online metal ion analyzer (10) is interlocked with the ion exchange unit switching valve. When the online metal ion analyzer (10) detects that the outlet metal ion concentration is greater than the preset value, it controls the ion exchange unit switching valve to switch from ion exchange column A (8) to ion exchange column B (9) or from ion exchange column B (9) to ion exchange column A (8).

7. The carbon fiber solvent recovery pretreatment system according to claim 2, characterized in that, The ion exchange column A (8) and ion exchange column B (9) are respectively connected to a regeneration pipeline system, which includes a primary water washing pipeline, an acid regeneration pipeline, a secondary water washing pipeline and a solvent replacement pipeline.

8. A method for pretreatment of carbon fiber solvent recovery, characterized in that, Using the carbon fiber solvent recovery pretreatment system according to any one of claims 1 to 7, the process includes the following steps: S1. The recovered solution containing impurities is transferred to the buffer tank (1) for temporary storage and homogenization; S2, the buffer tank discharge pump (2) pumps the homogenized solution into the primary filtration unit for primary filtration to intercept large-size low molecular weight PAN gel and initial carbonized particles. S3. The solution after primary filtration enters the secondary filtration unit for secondary filtration to remove fine particles and colloidal oligomers. S4, Ion exchange column feed pump (7) delivers the solution after secondary filtration to the ion exchange unit to remove metal ions from the solution; S5. The solution after ion exchange flows through the online metal ion analyzer (10), and is then transported to the three-stage filtration unit by the ion exchange column discharge pump (11) for three-stage filtration to retain trace amounts of resin debris and metal compound precipitates. The online metal ion analyzer (10) monitors the metal ion concentration at the outlet of the ion exchange unit in real time. S6. The pretreated solution enters the subsequent solvent recovery system.

9. The pretreatment method for carbon fiber solvent recovery according to claim 8, characterized in that, When the metal ion concentration at the outlet of the ion exchange column reaches the set threshold, regeneration shall be performed according to the following steps: S101, First wash: Use deionized water or process water for replacement cleaning, with a water volume of 2-7 BV and a water flow rate of 1-4 BV / h, until the DMSO concentration in the effluent is less than 1 wt%. S102. Acid regeneration: Regeneration is carried out using a hydrochloric acid solution with a mass concentration of 4% to 8%, the acid volume is 2 to 7 BV, the acid flow rate is 0.5 to 2 BV / h, and the acid temperature is controlled at 20 to 40℃. S103, Secondary water washing: Deionized water is used for washing, with a water volume of 2-7 BV and a flow rate of 1-4 BV / h, until the pH of the effluent reaches 7.0 and the conductivity tends to stabilize. S104 Solvent replacement: Replacement is performed using DMSO aqueous solutions of progressively increasing concentrations. DMSO aqueous solutions are sequentially introduced at a flow rate of 1-3 BV / h and a replacement temperature of 30-60℃. Replacement is completed when the DMSO concentration in the effluent does not deviate from the feed concentration by more than ±0.5wt%, the pH does not deviate from the feed concentration by more than ±0.3%, and the conductivity does not deviate from the feed conductivity by more than ±5%.

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