Recycling method and system for secondary coagulating bath in viscose fiber production

Abstract

The invention relates to a recycling method and system for a secondary coagulating bath in viscose fiber production. Relates to the technical field of viscose production. According to the invention, the secondary coagulating bath after the secondary bath in the viscose fiber production process is sequentially subjected to filtration, degassing cooling and heat exchange, and then is used for sealing water and / or filter cloth cleaning fluid of a rubber belt type vacuum filter. The secondary coagulating bath generated in the spinning process is subjected to filtering, impurity removal, high-vacuum degassing and cooling treatment and then is used for replacing known production water for sealing a vacuum box of a rubber belt type vacuum filter of equipment for separating solid sodium sulfate in an acid bath and circulating water for cleaning and regenerating filter cloth; when a rubber belt type vacuum filter is used as sodium sulfate separation equipment in the viscose fiber production process, water introduced into a system due to washing, equipment vacuum box sealing and filter cloth cleaning regeneration can be reduced, and steam loss indirectly generated in the equipment use process can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of viscose fiber production, and in particular to a method and system for recycling a secondary coagulation bath in viscose fiber production. Background Art

[0002] In the viscose fiber production process, the separation of sodium sulfate in the acid bath is a key step. In the traditional process, a rubber belt vacuum filter is used to separate sodium sulfate, but the following problems exist during its operation: (1) When using production water as sealing water and filter cloth cleaning liquid, water will enter the system with the acid bath, and the introduced water needs to be evaporated, which increases the water consumption and steam consumption of the system; (2) When using production water as filter cloth liquid and recycling it, as the sodium sulfate concentration in the water increases, the filter cloth cleaning effect is poor, resulting in incomplete filter cloth regeneration and affecting the filtration efficiency. Directly using production water as cleaning liquid without recycling will further increase the amount of water introduced into the system; (3) Spray water directly enters the system, increasing steam consumption and material loss. In the existing technology, although some companies use circulating water and dust removal water for optimization, they still cannot effectively solve the problems of high energy consumption and large water consumption. Therefore, it is urgent to develop a method and system for recycling the secondary coagulation bath in viscose fiber production to use the recycled secondary coagulation bath as sealing water and filter cloth cleaning liquid. Summary of the Invention

[0003] To address the above-mentioned technical problems, the present invention provides a method and system for recycling the secondary coagulation bath in viscose fiber production. The present invention uses the secondary coagulation bath generated during the spinning process, after filtering and removing impurities, high-vacuum degassing, and cooling, to replace the conventional production water used for sealing the vacuum box of the rubber belt vacuum filter and the circulating water used for cleaning and regenerating the filter cloth used to separate solid sodium sulfate from the acid bath. This method can reduce the amount of water introduced into the system due to washing, sealing the vacuum box of the equipment, and cleaning and regenerating the filter cloth when the rubber belt vacuum filter is used as the sodium sulfate separation equipment in the viscose fiber production process, thereby reducing indirect steam loss during the use of the equipment.

[0004] The technical solution of the present invention to solve the above technical problems is as follows: The first object of the present invention is to provide a method for recycling the secondary coagulation bath in viscose fiber production, wherein the secondary coagulation bath after the second bath in the viscose fiber production process is filtered, degassed, cooled, and heat-exchanged in sequence, and then used as sealing water and / or filter cloth cleaning liquid for a rubber belt vacuum filter.

[0005] Furthermore, the concentration of the secondary coagulation bath is 45-65°C.

[0006] The beneficial effects of the present invention are as follows: in the viscose fiber production process, the secondary coagulation bath generated in the spinning process is filtered to remove impurities, subjected to high vacuum degassing and temperature reduction treatment, and then used to replace the known production water used for sealing the vacuum box of the rubber belt vacuum filter and the circulating water used for cleaning and regenerating the filter cloth of the equipment for separating solid sodium sulfate in the acid bath; the water introduced into the system due to washing, sealing the vacuum box of the equipment and cleaning and regenerating the filter cloth when the rubber belt vacuum filter is used as the sodium sulfate separation equipment in the viscose fiber production process can be reduced, thereby reducing the steam loss indirectly generated during the use of the equipment.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the secondary coagulation bath includes sulfuric acid, sodium sulfate, hydrogen sulfide, and carbon disulfide; the content of the sulfuric acid is 30g / L to 50g / L; the content of the zinc sulfate is 2.5g / L to 6g / L, the content of the sodium sulfate is 80g / L to 150g / L; the content of the hydrogen sulfide is 150mg / L-202mg / L; and the content of the carbon disulfide is 56mg / L to 86mg / L.

[0009] The beneficial effect of adopting the above further solution is that the water consumption and steam consumption of the system are reduced by using the secondary coagulation bath instead of the produced water.

[0010] Furthermore, the degassing and cooling is specifically as follows: the filtered secondary coagulation bath is evaporated and cooled under vacuum to obtain a degassed and cooled secondary coagulation bath.

[0011] The beneficial effect of adopting the above further scheme is that organic impurities such as fiber and hemi-sugar will remain in the solution after the second coagulation bath of viscose fiber, which can be degassed and cooled under vacuum and filtered to remove impurities.

[0012] Furthermore, the absolute pressure of the vacuum is 1 kPa to 5 kPa, the temperature of the secondary coagulation bath after degassing and cooling is 32° C. to 38° C.; the content of hydrogen sulfide in the secondary coagulation bath after degassing and cooling is 0 mg / L to 30 mg / L; and the content of carbon disulfide is 0 mg / L to 30 mg / L.

[0013] The beneficial effects of adopting the above further solution are: degassing and cooling under vacuum, and filtering and removing impurities.

[0014] Furthermore, when the secondary coagulation bath after heat exchange is used for the sealing water, the temperature is lowered to 22°C to 28°C by heat exchange.

[0015] Furthermore, when the secondary coagulation bath after heat exchange is used as the filter cloth cleaning liquid, the temperature is raised to 35° C. to 50° C. by heat exchange.

[0016] A second object of the present invention is to provide a recycling system for a secondary coagulation bath in viscose fiber production, comprising a second-bath recovery tank, a second-bath delivery pump, a second-bath filter, a second-bath degassing and cooling device, a second-bath storage tank for impurities removal, a fresh second-bath delivery pump, a heat exchanger, and a rubber belt vacuum filter; The second bath recovery tank, the second bath delivery pump, the second bath filter, the second bath degassing and cooling device, the impurity removal second bath storage tank, and the fresh second bath delivery pump are connected in sequence; The heat exchanger includes a two-bath heat exchanger for washing filter cloth and a two-bath heat exchanger for sealing; the two-bath heat exchanger for washing filter cloth and the two-bath heat exchanger for sealing are respectively connected to the outlet of the fresh two-bath delivery pump, and then respectively connected to the rubber belt vacuum filter.

[0017] The beneficial effects of the present invention are: (1) by using a secondary coagulation bath instead of production water, the system water consumption and steam consumption are reduced; (2) the overall process operating cost is significantly reduced.

[0018] Furthermore, the two-bath degassing and cooling device includes a two-bath evaporation chamber and a two-bath secondary steam condenser; The two-bath evaporation chamber is provided with a first-stage evaporation chamber, a second-stage evaporation chamber, and a third-stage evaporation chamber; the two-bath secondary steam condenser is provided with a first-stage condenser, a second-stage condenser, and a third-stage condenser; The first-stage evaporation chamber is connected to the third-stage condenser, and the second-stage evaporation chamber is connected to the second-stage condenser; the third-stage evaporation chamber is connected to the first-stage condenser; the inlet of the first-stage condenser is connected to the lower part of the third-stage condenser via a water outlet pipe; the upper part of the first-stage condenser is connected to a water inlet pipe; The second-bath filter is connected to the first-stage evaporation chamber, and the third-stage evaporation chamber is connected to the second-bath storage tank for impurity removal.

[0019] The beneficial effect of adopting the above further scheme is: the vacuum of each condenser at each level of the second-bath secondary steam condenser is controlled differently from that of the evaporation chamber to ensure the temperature gradient, so that the evaporation amount of each evaporation chamber is uniform, to maximize the evaporation amount of the entire equipment, and to reduce the second bath to the lowest temperature through evaporation.

[0020] Furthermore, the two-bath degassing and cooling device also includes a cooling gas-liquid separation tank and a vacuum pumping device; the first-level condenser is connected to the cooling gas-liquid separation tank, the inlet of the vacuum pumping device is connected to the outlet of the first-level condenser, and the outlet of the vacuum pumping device is connected to the inlet of the cooling gas-liquid separation tank.

[0021] Furthermore, the system also includes a dust removal water recycling functional area, including a gas-liquid separation tank, a buffer tank, and a second water ring vacuum pump; the inlet of the gas-liquid separation tank is connected to the outlet of the rubber belt vacuum filter, the inlet of the buffer tank is connected to the drain port of the gas-liquid separation tank, the outlet of the buffer tank is connected to the inlet of the rubber belt vacuum filter, and the exhaust port of the gas-liquid separation tank is connected to the inlet of the second water ring vacuum pump.

[0022] The beneficial effect of adopting the above further solution is: the use of spray water recycling technology further reduces water consumption and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a system flow chart of Example 1 of the present invention; Figure 2 This is a system flow chart of Example 2 of the present invention; Figure 3 This is a diagram of the degassing and cooling device of Example 6 of the present invention.

[0024] In the accompanying drawings, the components represented by the reference numerals are as follows: 1. Second-bath recovery tank; 2. Second-bath delivery pump; 3. Second-bath filter; 4. Second-bath degassing and cooling device; 5. Second-bath storage tank for impurities removal; 6. Fresh second-bath delivery pump; 7. Second-bath heat exchanger for washing filter cloth and regeneration; 8. Second-bath heat exchanger for sealing; 9. Cooling gas-liquid separation tank; 10. Vacuuming device; 11. Gas-liquid separation tank; 12. Buffer tank; 13. Second water ring vacuum pump; 14. Recovery spray water delivery pump; 15. Rear spray zone; 16. Front spray zone; 17. Rubber belt vacuum filter; 18. First filtration device; 19. , second filtering device; 41, second-bath evaporation chamber; 42, second-bath secondary steam condenser; 101, first automatic control valve; 102, second automatic control valve; 103, third automatic control valve; 104, fourth automatic control valve; 105, fifth automatic control valve; 171, filter cloth tensioning device; 172, vacuum box; 173, acid collecting tank; 201, first pressure gauge; 202, second pressure gauge; 203, third pressure gauge; 301, first liquid level gauge; 302, second liquid level gauge; 1001, Roots vacuum pump; 1002, first water ring vacuum pump. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] Example 1: like Figure 1As shown: A recycling system for a secondary coagulation bath in viscose fiber production, comprising a second bath recovery tank 1, a second bath delivery pump 2, a second bath filter 3, a second bath degassing and cooling device 4, a second bath storage tank for impurities removal 5, a fresh second bath delivery pump 6, a heat exchanger, and a rubber belt vacuum filter 17; The second bath recovery tank 1, the second bath delivery pump 2, the second bath filter 3, the second bath degassing and cooling device 4, the impurity removal second bath storage tank 5, the fresh second bath delivery pump 6, the heat exchanger, and the rubber belt vacuum filter 17 are connected in sequence; The heat exchanger includes a two-bath heat exchanger 7 for washing filter cloth and a two-bath heat exchanger 8 for sealing. The two-bath heat exchanger 7 for washing filter cloth and the two-bath heat exchanger 8 for sealing are respectively connected to the outlet of the fresh two-bath delivery pump 6 and then respectively connected to the rubber belt vacuum filter 17.

[0027] Preferably, in the embodiment, the two-bath degassing and cooling device 4 includes a two-bath evaporation chamber 41 and a two-bath secondary steam condenser 42; The second-bath evaporation chamber 41 is provided with a first-stage evaporation chamber, a second-stage evaporation chamber, and a third-stage evaporation chamber; the second-bath secondary steam condenser 42 is provided with a first-stage condenser, a second-stage condenser, and a third-stage condenser; The first-stage evaporation chamber is connected to the third-stage condenser, the second-stage evaporation chamber is connected to the second-stage condenser; the third-stage evaporation chamber is connected to the first-stage condenser; the lower part of the third-stage condenser is connected to the water outlet pipe; the upper part of the first-stage condenser is connected to the water inlet pipe, which supplies 10-15m 3 / h The produced water with a temperature of 25-30℃ is discharged through the internal pipeline after passing through the high head difference step by step; Preferably, in other embodiments, Figure 3 As shown, the second-bath evaporation chamber 41 is provided with a primary evaporation chamber and a secondary evaporation chamber; the second-bath secondary steam condenser 42 is provided with a primary condenser and a secondary condenser; The first-level evaporation chamber is connected to the first-level condenser, and the second-level evaporation chamber is connected to the second-level condenser; the lower part of the second-level condenser is connected to the water outlet pipe; the upper part of the first-level condenser is connected to the water inlet pipe, which supplies 10m 3 / h~15m 3 / h The produced water with a temperature of 25℃~30℃ is discharged through the internal pipeline after passing through the high head difference step by step; Preferably, the two-bath degassing and cooling device 4 further includes a cooling gas-liquid separation tank 9 and a vacuum pumping device 10, and the vacuum pumping device 10 includes a Roots vacuum pump 1001 and a first water ring vacuum pump 1002; The primary condenser is connected to the cooling type gas-liquid separation tank 9, and a Roots vacuum pump 1001 and a first water ring vacuum pump 1002 are sequentially connected in the middle.

[0028] Preferably, the cooling type gas-liquid separation tank 9 is also connected to a water inlet pipe to cool the non-condensable gas in the cooling type gas-liquid separation tank 9 and wash away the acid entrained by the liquid foam in the non-condensable gas.

[0029] Preferably, the system also includes a gas-liquid separation tank 11, a buffer tank 12, and a second water ring vacuum pump 13; the gas-liquid separation tank 11 is connected to a rubber belt vacuum filter 17, the inlet of the buffer tank 12 is connected to the discharge port of the gas-liquid separation tank 11, the outlet of the buffer tank 12 is connected to the rubber belt vacuum filter 17, and the exhaust port of the gas-liquid separation tank 11 is connected to the second water ring vacuum pump 13.

[0030] Preferably, the rubber belt vacuum filter 17 includes a vacuum box 172 , a filter cloth tensioning device 171 , and an acid collecting tank 173 .

[0031] Example 2: In this embodiment, a first filtering device 18 is further connected between the sealing two-bath heat exchanger 8 and the rubber belt vacuum filter 17. The first filtering device 18 includes a plurality of filters; Preferably, a recycled spray water delivery pump 14 and a second filtering device 19 are sequentially connected between the buffer tank 12 and the rubber belt vacuum filter 17; the first filtering device 18 and the second filtering device 19 both include multiple filters; In this embodiment, an automatic control system is also included, which includes a first automatic control valve 101, a second automatic control valve 102, a third automatic control valve 103, a fourth automatic control valve 104, a fifth automatic control valve 105, a first liquid level gauge 301, and a second liquid level gauge 302; Preferably, a first liquid level gauge 301 is further installed in the second-bath recovery tank 1; the second-bath delivery pump 2 is respectively connected to the second-bath filter 3 and the second-bath degassing and cooling device 4; a third automatic control valve 103 is further connected between the second-bath degassing and cooling device 4 and the second-bath delivery pump 2, a first automatic control valve 101 is installed on the liquid inlet pipe of the second-bath recovery tank, and a second automatic control valve 102 is further installed between the first automatic control valve and the system; the real-time liquid level in the second-bath recovery tank 1 is detected by the first liquid level gauge 301 to be between 55% and 80%. When the liquid level exceeds 80%, the third automatic control valve 103 cannot be adjusted or fails, the second automatic control valve 102 is opened and the first automatic control valve 101 is closed to adjust the liquid level of the second-bath recovery tank 1; Preferably, a backup pump is also included, and the outlets of the second bath recovery tank 1 and the impurity removal second bath storage tank 5 are respectively connected to the inlet of the backup pump, and the outlet of the backup pump is respectively connected to the sealing second bath heat exchanger 8 and the second bath filter 3.

[0032] Preferably, the second-bath filter 3 includes multiple filters, a first pressure gauge 201 is installed between the second-bath filter 3 and the second-bath delivery pump 2, and a second pressure gauge 202 is installed between the second-bath delivery pump 2 and the second-bath degassing and cooling device 4. When the pressure difference between the first pressure gauge 201 and the second pressure gauge 202 is higher than 1 bar, the filters are switched to ensure the filtering effect.

[0033] Preferably, the acid collecting tank of the rubber belt vacuum filter 17 is connected to the external system and the impurity removal second bath storage tank 5 respectively, and the impurity removal second bath storage tank 5 is provided with a second liquid level gauge 302; the acid collecting tank 173 is also connected to the external system through a drain pipe, and a fourth automatic control valve 104 is installed on the drain pipe; When the second liquid level gauge 302 detects that the liquid level in the impurity removal second bath storage tank 5 is lower than 50%, the fourth automatic control valve 104 is opened for replenishment. When the liquid level is higher than 80%, the fourth automatic control valve 104 is closed, and the secondary coagulation bath after impurity removal in the impurity removal second bath storage tank 5 is pumped into the degassing and cooling device 4 through the fresh second bath delivery pump 6.

[0034] Example 3: Method 1 for recycling the secondary coagulation bath in viscose fiber production (1) Figure 2 As shown, the first automatic control valve 102 is opened, the second automatic control valve 101 is closed, and the secondary coagulation bath of 45-65°C generated in the second bath during the production of viscose fiber is discharged at a flow rate of 6m 3 / h~10m 3 / h is passed into the second bath recovery tank 1. The secondary coagulation bath includes sulfuric acid, sodium sulfate, hydrogen sulfide, carbon disulfide, and organic impurities; the content of sulfuric acid is 30-50g / L; the content of zinc sulfate is 2.5-6g / L, the content of sodium sulfate is 80g / L-150g / L; the content of hydrogen sulfide is 150-202mg / L; the content of carbon disulfide is 56-86mg / L; the second bath delivery pump 2 is then used to send the secondary coagulation bath into the high-precision filter 3 for filtration to obtain the filtered secondary coagulation bath, which is then passed into the first evaporation chamber, the second evaporation chamber, and the third evaporation chamber of the second bath degassing and cooling device 4 in sequence, and a Roots vacuum pump is used. 1001. The first water ring vacuum pump 1002 evacuates the chamber to maintain an absolute pressure of 1 kPa to 5 kPa in the final evaporation chamber, allowing the secondary coagulation bath to evaporate and cool under vacuum. The liquids in the first, second, and third evaporation chambers boil at an absolute pressure of 1 kPa to 5 kPa, and the vapors volatilized are condensed in the third, second, and first condensers, respectively. The temperature of the secondary coagulation bath is lowered to below 35° C. through successive evaporation, and the concentrations of hydrogen sulfide and carbon disulfide gases in the secondary coagulation bath are reduced to below 30 mg / l, thereby obtaining a degassed and cooled secondary coagulation bath. (2) After degassing and cooling, the hydrogen sulfide and carbon disulfide in the secondary coagulation bath are reduced to below 30 mg / l, and the temperature is reduced to below 35°C; at this time, the degassing and cooling secondary coagulation bath is discharged from the three-stage evaporation chamber into the impurity removal second bath storage tank 5, and the fresh second bath delivery pump 6 is used to deliver the fresh second bath at a rate of 4 to 6 m 3 , 2~3m 3The flow rate is discharged into the two-bath heat exchanger for washing filter cloth regeneration 7 and the two-bath heat exchanger for sealing 8. In the two-bath heat exchanger for washing filter cloth regeneration 7, the temperature is increased to 35℃~50℃ by heat exchange with the hot medium. The filter cloth is then passed into the rubber belt vacuum filter 17 and used as filter cloth cleaning liquid to clean the filter cloth tensioned by the filter cloth tensioning device 171. The filter cloth cleaning liquid after cleaning the filter cloth flows into the acid collecting tank 173 and is discharged through the overflow pipe and the floor drain. The secondary coagulation bath passed into the two-bath heat exchanger for sealing 8 is cooled to below 25℃ by heat exchange with the cold medium. After being filtered through the first filter 18, the filter cloth is filtered to 1m 3 The flow rate is passed into the vacuum box 172 in the rubber belt vacuum filter 17 as sealing water, and the overflowing sealing water is collected by the water receiving tray installed in the rubber belt vacuum filter 17 and enters the acid collecting tank 173; (3) The rubber belt vacuum filter 17 uses four spraying methods to spray the washing materials, of which the first two spraying methods are the front spraying area 16, and the last two spraying methods are the rear spraying area 15. The dust removal water treated by the patent CN115253545B is pumped through a centrifugal pump at a speed of 2m 3 / h~3m 3 / h flow rate is transported to the rear spraying area 15 of the rubber belt vacuum filter 17 for spraying to wash the material. The sprayed water is collected by the vacuum box and transported to the gas-liquid separation tank 11 for gas-liquid separation. The second water ring vacuum pump 13 puts the gas-liquid separation tank 11 into a vacuum state, the separated gas is discharged, and the liquid is discharged into the buffer tank 12. It is transported to the second filtering device 19 through the recovery spray water delivery pump 14 for filtration and impurity removal, and then transported to the front spraying area 16 of the rubber belt vacuum filter 17. The flow rate is 2-3m 3 / h, the water volume in the front spray area 16 is slightly higher than that in the rear spray area 15, and the dust removal water treated by patent CN115253545B is added to the tank through the fifth automatic control valve 105 connected to the buffer tank 12 to ensure the stability of the liquid level and ensure that the water volume in the front spray area 16 is greater than that in the rear spray area 15.

[0035] Example 4: Method 2 for recycling the secondary coagulation bath in viscose fiber production (1) Figure 1 As shown in the figure, the secondary coagulation bath at 45℃~65℃ produced by the second bath in the viscose fiber production process is heated to a flow rate of 6m 3 / h~10m 3 / h is passed into the second bath recovery tank 1. The secondary coagulation bath includes sulfuric acid, sodium sulfate, hydrogen sulfide, carbon disulfide, and organic impurities; the content of sulfuric acid is 30g / L~50g / L; the content of zinc sulfate is 2.5g / L~6g / L, the content of sodium sulfate is 80g / L~150g / L; the content of hydrogen sulfide is 150mg / L~202mg / L; the content of carbon disulfide is 56mg / L~86mg / L; the second bath delivery pump 2 is then used to send the secondary coagulation bath into the diatomaceous earth filter 3 for filtration to obtain the filtered secondary coagulation bath, which is then passed into the first evaporation chamber, the second evaporation chamber, and the third evaporation chamber of the second bath degassing and cooling device 4 in sequence, and the Roots vacuum pump 1001 and the first water ring vacuum pump 1002 are used for vacuuming, so that the absolute pressure of the final evaporation chamber is maintained at 1kPa~5kPa, so that the secondary coagulation bath evaporates and cools under vacuum; (2) After degassing and cooling, the hydrogen sulfide and carbon disulfide in the secondary coagulation bath are reduced to below 30 mg / l, and the temperature is reduced to below 35°C. At this time, the secondary coagulation bath after degassing and cooling is discharged from the three-stage evaporation chamber into the impurity removal second bath storage tank 5, and is discharged into the filter cloth washing regeneration second bath heat exchanger 7 and the sealing second bath heat exchanger 8 through the fresh second bath delivery pump 6. In the filter cloth washing regeneration second bath heat exchanger 7, the temperature is increased to 35°C to 50°C by heat exchange with the heat medium, and then passed into the rubber belt vacuum filter 17. , used as filter cloth cleaning liquid to clean the filter cloth tensioned by the filter cloth tensioning device. The filter cloth cleaning liquid after cleaning the filter cloth flows into the acid collecting tank 173 and is discharged through the overflow pipe and floor drain; it is passed into the secondary coagulation bath in the sealing two-bath heat exchanger to cool down to below 25°C through heat exchange with the cold medium, and then passed into the vacuum box 172 in the rubber belt vacuum filter 17 to be used as sealing water. The overflowing sealing water is collected by the water receiving tray installed in the rubber belt vacuum filter 17 and enters the acid collecting tank 173; (3) The rubber belt vacuum filter 17 uses four spraying methods to spray the washing materials, of which the first two spraying methods are the front spraying area 16, and the last two spraying methods are the rear spraying area 15. The dust removal water treated by the patent CN115253545B is pumped through a centrifugal pump at a speed of 2m 3 / h~3m 3 / h flow rate is transported to the rear spraying area of ​​the rubber belt vacuum filter 17 for spraying to wash the material. The sprayed water is collected by the vacuum box 172 and transported to the gas-liquid separation tank 11 for gas-liquid separation. The second water ring vacuum pump 13 puts the gas-liquid separation tank 11 into a vacuum state, the separated gas is discharged, and the liquid is discharged into the buffer tank 12. It is transported to the second filter 19 through the recovery spray water delivery pump 14 for filtration and impurity removal, and then transported to the front spraying area of ​​the rubber belt vacuum filter 17. The flow rate is 2m 3 / h~3m 3 / h, the water volume in the front spray area 16 is slightly higher than that in the rear spray area 15, and the dust removal water treated by patent CN115253545B is added to the tank through the fifth automatic control valve 105 connected to the buffer tank 12 to ensure the stability of the liquid level and ensure that the water volume in the front spray area 16 is greater than that in the rear spray area 16.

[0036] Example 5: Method 3 for recycling the secondary coagulation bath in viscose fiber production (1) Figure 2 As shown, open the first automatic control valve 102, close the second automatic control valve 101, and heat the second bath of the filter cloth regeneration in the viscose fiber production process in the heat exchanger 7 to 50-55 ° C, with a flow rate of 10m 3 / h of the secondary coagulation bath, flows out, and then passes into the second bath recovery tank 1, its components include sulfuric acid, sodium sulfate, hydrogen sulfide, carbon disulfide, and organic impurities; wherein the content of sulfuric acid is 30-50g / L; the content of zinc sulfate is 2.5g / L~6g / L, the content of sodium sulfate is 80g / L~150g / L; the content of hydrogen sulfide is 150mg / L~202mg / L; the content of carbon disulfide is 56mg / L~86mg / L; then the second bath delivery pump 2 is used to send the secondary coagulation bath into the diatomaceous earth filter 3 for filtration to obtain the filtered secondary coagulation bath, and then sequentially pass into the first evaporation chamber, the second evaporation chamber, and the third evaporation chamber of the second bath degassing and cooling device 4, and use the Roots vacuum pump and the first water ring vacuum pump to evacuate the absolute pressure of the final evaporation chamber to maintain at 3kPa, so that the secondary coagulation bath evaporates and cools to below 30°C under vacuum; (2) After degassing and cooling, the hydrogen sulfide and carbon disulfide in the secondary coagulation bath are reduced to below 30 mg / l, and the temperature is reduced to below 30°C. At this time, the degassed and cooled secondary coagulation bath is discharged from the three-stage evaporation chamber into the impurity removal second bath storage tank 5, and is discharged into the filter cloth washing regeneration second bath heat exchanger 7 and the sealing second bath heat exchanger 8 through the fresh second bath delivery pump 6. In the filter cloth washing regeneration second bath heat exchanger 7, the temperature is exchanged with the 65°C second bath to be raised to 42°C to 48°C, and then passed into the rubber belt vacuum filter 17. The filter cloth tensioned by the filter cloth tensioning device 171 is cleaned as a filter cloth cleaning liquid. The filter cloth cleaning liquid flows into the acid collecting tank 173 after cleaning the filter cloth and is discharged through the overflow pipe and floor drain. The liquid is passed into the secondary coagulation bath in the sealing two-bath heat exchanger 8, where it is cooled to below 25°C by heat exchange with the cold medium. The liquid is then passed into the vacuum box 172 in the rubber belt vacuum filter 17 and used as sealing water. The overflowing sealing water is collected by a water receiving tray installed in the rubber belt vacuum filter 17 and flows into the acid collecting tank 173. (3) The rubber belt vacuum filter 17 uses four spraying methods to spray the washing materials, of which the first two spraying methods are the front spraying area 16, and the last two spraying methods are the rear spraying area 15. The dust removal water treated by the patent CN115253545B is pumped through a centrifugal pump at a speed of 2m 3 / h flow rate is transported to the rear spraying area 16 of the rubber belt vacuum filter 17 for spraying to wash the material. The sprayed water is collected by the vacuum box 172 and transported to the gas-liquid separation tank 11 for gas-liquid separation. The second water ring vacuum pump 13 puts the gas-liquid separation tank 11 into a vacuum state, the separated gas is discharged, and the liquid is discharged into the buffer tank 12. It is transported to the second filter 19 through the recovery spray water delivery pump 14 for filtration and impurity removal, and then transported to the front spraying area of ​​the rubber belt vacuum filter 17. The flow rate is 2m 3 / h~3m 3 / h, the water volume in the front spray area 16 is slightly higher than that in the rear spray area 15, and the dust removal water treated by patent CN115253545B is added to the tank through the fifth automatic control valve 105 connected to the buffer tank 12 to ensure the stability of the liquid level and ensure that the water volume in the front spray area 16 is greater than that in the rear spray area 15.

[0037] Example 6: Method 3 for recycling the secondary coagulation bath in viscose fiber production (1)Reference Figure 2 , open the first automatic control valve 102, close the second automatic control valve 101, and heat the 65℃ generated by the secondary coagulation bath in the viscose fiber production process to 50℃~55℃ in the heat exchanger 7, with a flow rate of 10m 3 / h secondary coagulation bath is passed into the second bath recovery tank 1, and its components include sulfuric acid, sodium sulfate, hydrogen sulfide, carbon disulfide, and organic impurities; wherein the content of sulfuric acid is 30g / L~50g / L; the content of zinc sulfate is 2.5g / L~6g / L, the content of sodium sulfate is 80g / L~150g / L; the content of hydrogen sulfide is 150mg / L~202mg / L; the content of carbon disulfide is 56g / L~86mg / L; then the second bath delivery pump 2 is used to send the secondary coagulation bath into the diatomaceous earth filter 3 for filtration to obtain the filtered secondary coagulation bath, and then it is passed into the following Figure 3 The primary evaporation chamber and the secondary evaporation chamber of the two-bath degassing and cooling device 4 are evacuated using a Roots vacuum pump 1001 and a first water ring vacuum pump 1002 to maintain an absolute pressure of 3 kPa in the secondary evaporation chamber, so that the secondary coagulation bath evaporates and cools to 35-38° C. under vacuum. (2) After degassing and cooling, the hydrogen sulfide and carbon disulfide in the secondary coagulation bath are reduced to below 30 mg / l, and the temperature is reduced to 35-38°C. At this time, the degassed and cooled secondary coagulation bath is discharged from the secondary evaporation chamber into the impurity removal second bath storage tank 5, and is discharged into the filter cloth washing regeneration second bath heat exchanger 7 and the sealing second bath heat exchanger 8 through the fresh second bath delivery pump 6. In the filter cloth washing regeneration second bath heat exchanger 7, the temperature is exchanged with the 65°C second bath to 42-48°C, and then passed into the rubber belt vacuum filter 17. The filter cloth tensioned by the filter cloth tensioning device 171 is cleaned as a filter cloth cleaning liquid. The filter cloth cleaning liquid flows into the acid collecting tank 173 after cleaning the filter cloth and is discharged through the overflow pipe and floor drain. The liquid is passed into the secondary coagulation bath in the sealing two-bath heat exchanger 8, where it is cooled to below 25°C by heat exchange with the cold medium. The liquid is then passed into the vacuum box 172 in the rubber belt vacuum filter 17 and used as sealing water. The overflowing sealing water is collected by a water receiving tray installed in the rubber belt vacuum filter 17 and flows into the acid collecting tank 173. (3) The rubber belt vacuum filter 17 uses four spraying methods to spray the washing materials, of which the first two spraying methods are the front spraying area 16, and the last two spraying methods are the rear spraying area 15. The dust removal water treated by the patent CN115253545B is pumped through a centrifugal pump at a speed of 2m 3 / h flow rate is transported to the rear spraying area 15 of the rubber belt vacuum filter 17 for spraying to wash the material. The sprayed water is collected by the vacuum box 172 and transported to the gas-liquid separation tank 11 for gas-liquid separation. The second water ring vacuum pump 13 puts the gas-liquid separation tank 11 into a vacuum state, the separated gas is discharged, and the liquid is discharged into the buffer tank 12. It is transported to the second filter 19 through the recovery spray water delivery pump 14 for filtration and impurity removal, and then transported to the front spraying area 16 of the rubber belt vacuum filter 17. The flow rate is 2m 3 / h~3m 3 / h, the water volume in the front spray area 16 is slightly higher than that in the rear spray area 15, and the dust removal water treated by patent CN115253545B is added to the tank through the fifth automatic control valve 105 connected to the buffer tank 12 to ensure the stability of the liquid level and ensure that the water volume in the front spray area 16 is greater than that in the rear spray area 15.

[0038] In Example 3, Example 4, Example 5, and Example 6, the system needs to evaporate 1-2 tons of water per hour.

[0039] Comparative Example 1: Recycling method of secondary coagulation bath in viscose fiber production The production water is directly used as sealing water and filter cloth cleaning liquid, 2 tons of sealing water per hour, the filter cloth cleaning liquid is recycled and collected for use, and 1 ton of production water is replenished per hour to replace the cleaning liquid; the sealing water and filter cloth cleaning replenishing liquid enter the system directly through the rubber belt vacuum filter; the spray water of the rubber belt vacuum filter 17 uses the dust removal water treated by the patent CN115253545B, and 3 tons of water are still introduced into the system.

[0040] The results show that the traditional process requires the introduction of 6 tons of water into the system per hour, the system increases the evaporation of 6 tons of water, the steam consumption is high, and the filter cloth regeneration effect is poor.

[0041] Comparative Example 2: Recycling method of secondary coagulation bath in viscose fiber production The second bath is directly mixed into the acid bath used in viscose fiber production. The produced water is used as sealing water and filter cloth cleaning fluid for the rubber belt vacuum filter 17. One ton of sealing water is supplied per hour, and the filter cloth cleaning fluid is recycled. One ton of produced water is added to replace the cleaning fluid. The sealing water and filter cloth cleaning supplementary fluid pass directly through the rubber belt vacuum filter 17 into the external system. The spray water for the rubber belt vacuum filter 17, treated with dust removal water from patent CN115253545B, still requires two tons of water to be introduced into the system. Results show that the conventional process requires the introduction of four tons of water into the system per hour, resulting in an additional four tons of water evaporation, high steam consumption, and poor filter cloth regeneration.

[0042] It can be seen that the process of the present invention reduces steam consumption by 0.9 tons per hour compared with the traditional process.

[0043] Comparative Example 3: Recycling method of secondary coagulation bath in viscose fiber production The second bath was directly mixed into the acid bath used in viscose fiber production. The production water was used as filter cloth cleaning fluid, supplying 2 tons per hour. After cleaning the filter cloth, the cleaning fluid was recovered and used as sealing water. This sealing water passed directly into the system through a rubber belt vacuum filter 17. The spray water from the rubber belt vacuum filter, treated with dust removal water from patent CN115253545B, still required 2 tons of water to be introduced into the system. Results showed that the conventional process required the introduction of 4 tons of water into the system per hour, resulting in an additional 4 tons of water evaporation, high steam consumption, and poor filter cloth regeneration.

[0044] It can be seen that the process of the present invention reduces steam consumption by 0.9 tons per hour compared with the traditional process.

[0045] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0046] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0047] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0048] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0049] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for recycling a secondary coagulation bath in viscose fiber production, characterized in that: The secondary coagulation bath after the second bath in the viscose fiber production process is filtered, degassed, cooled, and heat-exchanged in sequence, and then used as sealing water and / or filter cloth cleaning liquid for the rubber belt vacuum filter.

2. The method for recycling a secondary coagulation bath in viscose fiber production according to claim 1, characterized in that: The secondary coagulation bath includes sulfuric acid, sodium sulfate, hydrogen sulfide, and carbon disulfide; the content of the sulfuric acid is 30-50 g / L; the content of the zinc sulfate is 2.5-6 g / L, the content of the sodium sulfate is 80-150 g / L; the content of the hydrogen sulfide is 150-202 mg / L; and the content of the carbon disulfide is 56-86 mg / L.

3. The method for recycling a secondary coagulation bath in viscose fiber production according to claim 2, characterized in that: The degassing and cooling is specifically as follows: the filtered secondary coagulation bath is evaporated and cooled under vacuum to obtain a degassed and cooled secondary coagulation bath.

4. The method for recycling a secondary coagulation bath in viscose fiber production according to claim 3, characterized in that: The absolute pressure of the vacuum is 1 to 5 kPa, the temperature of the secondary coagulation bath after degassing and cooling is 32° C. to 38° C.; the content of hydrogen sulfide in the secondary coagulation bath after degassing and cooling is 0 mg / L to 30 mg / L; and the content of carbon disulfide is 0 mg / L to 30 mg / L.

5. The method for recycling a secondary coagulation bath in viscose fiber production according to claim 1, characterized in that: When the secondary coagulation bath is used for the sealing water, the temperature is lowered to 22-28°C by heat exchange.

6. The method for recycling a secondary coagulation bath in viscose fiber production according to claim 1, characterized in that: When the secondary coagulation bath is used as the filter cloth cleaning liquid, the temperature is raised to 35° C. to 50° C. by heat exchange.

7. A recycling system for secondary coagulation bath in viscose fiber production, characterized in that: It includes a second bath recovery tank (1), a second bath delivery pump (2), a second bath filter (3), a second bath degassing and cooling device (4), a second bath storage tank for impurities removal (5), a fresh second bath delivery pump (6), a heat exchanger, and a rubber belt vacuum filter (17); The second bath recovery tank (1), the second bath delivery pump (2), the second bath filter (3), the second bath degassing and cooling device (4), the impurity removal second bath storage tank (5), and the fresh second bath delivery pump (6) are connected in sequence; The heat exchanger comprises a two-bath heat exchanger (7) for washing filter cloth and regenerating the filter cloth, and a two-bath heat exchanger (8) for sealing. The two-bath heat exchanger (7) for washing filter cloth and regenerating the filter cloth and the two-bath heat exchanger (8) for sealing are respectively connected to the two-bath fresh water delivery pump (6), and then respectively connected to the rubber belt vacuum filter (17).

8. The recycling system of the secondary coagulation bath in viscose fiber production according to claim 7, characterized in that: The two-bath degassing and cooling device (4) comprises a two-bath evaporation chamber (41) and a two-bath secondary steam condenser (42); The second-bath evaporation chamber (41) is provided with a first-stage evaporation chamber, a second-stage evaporation chamber, and a third-stage evaporation chamber; the second-bath secondary steam condenser (42) is provided with a first-stage condenser, a second-stage condenser, and a third-stage condenser; The first-stage evaporation chamber is connected to the third-stage condenser, and the second-stage evaporation chamber is connected to the second-stage condenser; the third-stage evaporation chamber is connected to the first-stage condenser; the lower part of the third-stage condenser is connected to a water outlet pipe; the upper part of the first-stage condenser is connected to a water inlet pipe; The second-bath filter (3) is connected to the first-stage evaporation chamber, and the third-stage evaporation chamber is connected to the second-bath storage tank (5) for impurity removal.

9. The recycling system of the secondary coagulation bath in viscose fiber production according to claim 8, characterized in that: The two-bath degassing and cooling device (4) further comprises a cooling gas-liquid separation tank (9) and a vacuum pumping device (10); the first-stage condenser is connected to the cooling gas-liquid separation tank (9), the inlet of the vacuum pumping device (10) is connected to the outlet of the first-stage condenser, and the outlet of the vacuum pumping device (10) is connected to the inlet of the cooling gas-liquid separation tank (9).

10. The recycling system of the secondary coagulation bath in viscose fiber production according to claim 7, characterized in that: The system further comprises a gas-liquid separation tank (11), a buffer tank (12), and a second water ring vacuum pump (13); the inlet of the gas-liquid separation tank (11) is connected to the outlet of the rubber belt vacuum filter (17), the inlet of the buffer tank (12) is connected to the liquid discharge port of the gas-liquid separation tank (11), the outlet of the buffer tank (12) is connected to the inlet of the rubber belt vacuum filter (17), and the exhaust port of the gas-liquid separation tank (11) is connected to the inlet of the second water ring vacuum pump (13).

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