Device and process for comprehensively recycling tail gas generated in production of chemical polyimide film

Abstract

The invention relates to a device and a process for comprehensively recycling tail gas generated in production of a chemical polyimide film. The device consists of an absorption separation system, a salt separation recovery system and a rectification system. The process comprises the following steps: collecting production tail gas, feeding the tail gas into a first absorption tower, and removing acetic acid and isoquinoline in the tail gas to obtain a recovery solution containing acetate and isoquinoline; the tail gas at the top of the first absorption tower enters a second absorption tower for DMF / DMAC recovery to obtain a clean DMF / DMAC recovery liquid, the clean DMF / DMAC recovery liquid is sent to a rectification system and refined to obtain a qualified DMF / DMAC product, and the tail gas treated by the second absorption tower is discharged after reaching the standard; the acetate-containing recovery liquid is sent to a salt separation recovery system, and acetate and isoquinoline products are obtained after salt separation and purification; according to the device and the process, the purified tail gas reaches the standard and is discharged, meanwhile, comprehensive recycling of high-value components in the chemical method polyimide film production tail gas is achieved, qualified sodium acetate, isoquinoline and DMF / DMAC products are obtained, and great economic benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of tail gas recovery and resource utilization, and specifically relates to a comprehensive recovery and utilization device for tail gas produced by a chemical method polyimide film and a process thereof. Background Art

[0002] The production of new materials and special functional membranes in China has entered a period of rapid development. At present, there are two main methods for imidization of polyimide films (PI films), namely thermal imidization and chemical imidization. The thermal imidization method heats the polyamic acid to a certain temperature to dehydrate and cyclize it; the chemical imidization method is to add a certain amount of dehydrating agent (acetic anhydride) and catalyst (isoquinoline, etc.) to the polyamic acid solution, quickly mix it, and then heat it to a certain temperature to dehydrate and cyclize it. The process and equipment of the thermal imidization method are simpler than those of the chemical imidization method, but the physical and chemical properties of the obtained film are insufficient compared with those of the chemical imidization method, and it is impossible to produce PI films that meet electronic grade and above. Therefore, with the continuous expansion of demand for high-end functional membrane materials, domestic manufacturers are gradually transitioning from the technology and equipment of the thermal imidization method to the chemical imidization method.

[0003] In the process of chemical polyimide film production, high-temperature tail gas containing acetic acid, catalysts and organic solvents will be generated, which needs to be treated before it can meet the emission standards. At present, combustion methods are mostly used for such tail gas with complex components, such as direct-fired incinerators (TO) and catalytic oxidation (CO). The principle is that the organic components in the tail gas are burned or decomposed into inert components by redox reactions to achieve harmless treatment of organic waste. However, these technologies are all destruction methods, which can only treat organic matter in the tail gas, and cannot recycle and reuse valuable components, especially DMF / DMAC, which is an important solvent in the production of polyimide films, resulting in a huge waste of resources. In addition, the equipment investment of the combustion method is large, and the maintenance cost is high during operation. The catalytic oxidation method also needs to consider the high cost of catalyst deactivation and replacement. If the organic solvent in the tail gas is recovered by a single absorption method or a multi-stage condensation method, a mixed solution of acid, isoquinoline and organic solvent can be obtained. However, since acetic acid forms an azeotrope with DMF / DMAC, the subsequent separation and purification equipment of the organic solvent is complex, the investment is large and the separation is difficult. The purity of acetic acid is low and cannot be reused or sold.

[0004] Therefore, it is necessary to develop a comprehensive tail gas recovery and utilization process and device that can recover high-value components in tail gas from the production of chemical polyimide films and has relatively low processing costs. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention aims to provide a comprehensive recovery and utilization device for tail gas produced by chemical polyimide film production and a process thereof, which adopts absorption separation + salt recovery + distillation technology to solve the problem that the traditional combustion method is high in cost and cannot recover and utilize high-value components in the tail gas. While the purified tail gas meets the emission standards, the separation and recovery of high-value components in the tail gas produced by chemical polyimide film production is achieved, and qualified sodium acetate, isoquinoline and DMF / DMAC products are obtained; In order to achieve the above object, the technical solution adopted by the present invention is as follows: In the first aspect, the present invention provides a chemical method polyimide film production tail gas recovery device, which is used to realize the production tail gas recovery process. The tail gas recovery device includes an absorption separation system, a salt recovery system and a distillation system; the absorption separation system includes a first absorption tower and a matching first circulation pump, a second circulation pump, a second absorption tower and a third circulation pump; the salt recovery system includes an evaporator, an evaporative condenser, a vacuum pump, a crystallization device and a drying device; the distillation system includes a first distillation tower, a second distillation tower, a first condenser, a first reboiler, a second condenser, and a vacuum device.

[0006] The gas phase inlet of the first absorption tower of the absorption and separation system is arranged at the bottom of the tower, and the tail gas of the chemical polyimide film production is collected and aggregated and connected to the inlet of the first absorption tower through a pipeline; the liquid phase outlet of the kettle of the first absorption tower is connected to the inlet of the first circulation pump, and the outlet of the first circulation pump is divided into two branches, one of which is connected to the liquid inlet in the middle of the first absorption tower, and the other branch is connected to the liquid phase inlet of the evaporator of the salt recovery system; a liquid collecting tray is arranged in the middle section of the first absorption tower, and the outlet of the liquid collecting tray is connected to the inlet of the second circulation pump, and the outlet of the second circulation pump is connected to the liquid inlet at the top of the first absorption tower; the gas phase outlet at the top of the first absorption tower is connected to the gas phase outlet at the bottom of the second absorption tower The inlet of the second absorption tower kettle is connected to the inlet of the third circulation pump, and the outlet of the third circulation pump is divided into two branches, one of which is connected to the liquid inlet in the middle of the second absorption tower, and the other is connected to the feed inlet of the first distillation tower of the distillation system; a liquid collecting tray is arranged in the middle section of the second absorption tower, and the outlet of the liquid collecting tray is connected to the liquid inlet at the top of the first absorption tower after pressurization by a pipeline connection pump; a fresh water inlet is arranged at the top of the second absorption tower; the evaporator is provided with stirring and a jacket, and the gas phase outlet at the top of the evaporator is connected to the gas phase inlet of the evaporative condenser; the gas phase outlet of the evaporative condenser is connected to the inlet of the vacuum pump, and the liquid phase outlet of the evaporative condenser is connected to the inlet of the vacuum pump, and the liquid phase outlet of the evaporative condenser is connected to the inlet of the vacuum pump. The pump is connected to the liquid phase feed port at the top of the first absorption tower; the liquid phase outlet of the evaporator is divided into two branches, one of which is connected to the inlet of the crystallization equipment, and the other is connected to the inlet of the drying equipment; the crystallization equipment is provided with a solid phase outlet and a liquid phase outlet, the solid phase outlet is used to produce the acetate product, and the liquid phase outlet is divided into two branches, one of which is connected to the liquid phase inlet of the evaporator, and the other is used to produce the residual liquid; the gas phase outlet at the top of the first distillation tower is connected to the feed port of the first condenser, the gas phase outlet of the first condenser is connected to the vacuum equipment, and the liquid phase outlet of the first condenser is divided into two branches, one of which is refluxed to the liquid phase inlet at the top of the first distillation tower, and the other is refluxed to the liquid phase inlet at the top of the first distillation tower. Used to produce water for reuse in the second absorption tower; the bottom discharge port of the first distillation tower is divided into two branches, one of which is connected to the first reboiler, and the other branch is used to produce distillation residue to the outside; the gas phase outlet at the bottom of the first distillation tower is connected to the gas phase feed port of the second distillation tower; the gas phase outlet at the top of the second distillation tower is connected to the second condenser, the gas phase outlet of the second condenser is connected to the vacuum equipment, the liquid phase outlet of the second condenser is divided into two branches, one of which is refluxed to the liquid phase inlet at the top of the second distillation tower, and the other branch produces DMF / DMAC finished product; the kettle outlet of the second distillation tower is connected to the kettle feed port of the first distillation tower after being pressurized by a pump.

[0007] Furthermore, the first absorption tower is a segmented absorption tower, the lower section of the tower is a neutralization and salt-forming section, a multi-layer circulating spray distributor is provided, alkali solution is added from the liquid inlet in the middle of the first absorption tower or the tower kettle, and acetic acid in the tail gas is removed after being neutralized and salt-formed in the lower section of the tower. The upper section of the first absorption tower is an absorption section, which adopts a filler or a tower plate structure, a high-precision liquid distributor is provided at the top of the tower, and a DMF / DMAC aqueous solution is added from the liquid inlet at the top of the tower, and sprayed downward through the distributor to achieve the removal of isoquinoline in the tail gas.

[0008] Furthermore, the second absorption tower is a multi-stage absorption tower, the topmost stage is a packed tower or a plate tower, a high-precision liquid distributor is provided, the absorbent is fresh water, which is added from the liquid phase inlet at the top of the tower; the remaining stages are circulating absorption stages, which adopt a packing design and are all provided with circulating spray distributors. The absorption liquid is the circulating liquid in the bottom of the tower, and the number of circulating stages is 1 to 5. The recovery of DMF / DMAC in the tail gas is achieved through multi-stage absorption.

[0009] Furthermore, the evaporator is a stirred kettle with a jacket, the jacket is heated by steam or thermal oil, and a spray device is provided on the top for uniform dispersion of water. The crystallization equipment is one or a combination of an evaporation crystallizer and a cooling crystallizer, with a centrifugal separation and cleaning system.

[0010] Furthermore, the first distillation tower and the second distillation tower are plate towers or packed towers. After the DMF / DMAC recovery liquid is obtained by multi-stage absorption in the second absorption tower and water is removed from the first distillation tower, a crude DMF / DMAC product is obtained in the bottom of the tower and needs to be transported to the second distillation tower for further purification. If the reuse purity requirement of the DMF / DMAC product is not high, the crude product can be directly reused.

[0011] In a second aspect, the present invention further provides a comprehensive recovery and utilization process of tail gas from the production of polyimide film by a chemical method, which is carried out using the tail gas comprehensive recovery and utilization device as described above, and the tail gas comprehensive recovery and utilization process comprises the following steps: (1) The high-temperature exhaust gas from the PI film production line is collected and transported to the first absorption tower. In the first absorption tower, alkali solution and DMF / DMAC aqueous solution are used as absorbents to remove acetic acid and isoquinoline in the exhaust gas. After acetic acid is neutralized, acetate is formed and isoquinoline enters the bottom liquid of the first absorption tower.

[0012] (2) The tail gas is passed through the first absorption tower in step (1) to remove acetic acid and isoquinoline, and then enters the second absorption tower. The top of the second absorption tower uses water as an absorbent to recover DMF / DMAC in the tail gas, and a high-concentration DMF / DMAC recovery liquid is obtained in the bottom of the tower. The tail gas is purified in the second absorption tower and meets the emission standards.

[0013] (3) In step (1), the bottom liquid of the first absorption tower is regularly taken out to separate the salt recovery system, and the washing liquid is evaporated and concentrated by an evaporator. The gas phase of the evaporator is condensed to obtain water and DMF / DMAC mixed liquid, which is returned to the top of the first absorption tower for liquid replenishment; the mother liquor is evaporated and concentrated to recover the remaining solvent and then separated and refined by a crystallization device to obtain a qualified acetate product. After the isoquinoline in the mother liquor is concentrated to a certain concentration, it is evaporated to dryness in an evaporator and dissolved in water. Since isoquinoline is insoluble in water, it is separated from the sodium acetate aqueous solution, and the lower oil phase is taken and dried to obtain the isoquinoline product; (4) The DMF / DMAC recovery liquid obtained in step (2) is transported to a first distillation tower for distillation separation. Under the action of a bottom reboiler, a top condenser and a certain reflux ratio, water is produced from the top of the tower and a crude DMF / DMAC product is obtained in the bottom of the tower; (5) The second distillation tower and the first distillation tower share a reboiler. The rising vapor from the bottom of the first distillation tower is partially extracted and sent to the second distillation tower for further refining. The gas phase extracted from the top of the second distillation tower is condensed to obtain DMF / DMAC finished products that meet the index requirements, and the bottom liquid is returned to the first distillation tower. The bottom of the first distillation tower regularly extracts the distillation residue.

[0014] Furthermore, the main components of the PI film production tail gas in step (1) are: DMF / DMAC content 1~15g / Nm 3 , acetic acid (acetic anhydride) content 0.4~5g / Nm 3 , isoquinoline content 0.05~1g / Nm 3 , the rest is water, air and a small amount of polymers, dust, tar, etc.

[0015] Furthermore, the temperature of the high-temperature tail gas produced by the PI film production in step (1) is 80-260° C. The operating temperature of the first absorption tower is 5-55° C. The operating temperature of the second absorption tower in step (2) is 5-40° C.

[0016] Furthermore, the alkali solution is added from the middle of the tower or the bottom of the tower, and the acetic acid in the tail gas is neutralized and salted in the lower section of the tower before being removed. The amount of alkali solution added is controlled by the pH of the bottom liquid of the first absorption tower, and the pH value control range is 4 to 6. The DMF / DMAC aqueous solution is added from the top of the tower and sprayed downward through a distributor to further achieve the removal of isoquinoline; Furthermore, the DMF / DMAC aqueous solution is derived from one or more of the recovered liquid from the top section of the second absorption tower in step (2), the recovered liquid from the bottom of the second absorption tower, and the water and DMF / DMAC mixed liquid in step (3); Furthermore, in step (1), the acetate content in the bottom liquid of the first absorption tower is 10-40% (mass percentage); in step (2), the DMF / DMAC content in the DMF / DMAC recovery liquid obtained in the bottom liquid is 40%-80% (mass percentage), and the tail gas is purified by the second absorption tower, wherein the DMAC / DMF concentration is less than 20 mg / m 3 .

[0017] Furthermore, the evaporator is operated under vacuum, the evaporation temperature is 50-130° C., and the operating pressure is 10-90 kPa.

[0018] Furthermore, the crystallization separation and purification process described in step (3) is one of evaporation crystallization and cooling crystallization or a combination of these processes. After the evaporation mother liquor is crystallized, centrifuged and washed, a qualified acetate product is obtained. The crystallization mother liquor is returned to the evaporator, and part of it is extracted as residual liquid.

[0019] Furthermore, the isoquinoline drying process in step (3) is drying with molecular sieves or anhydrous sodium sulfate.

[0020] Furthermore, in step (4), the operating temperature of the top of the first distillation tower is 60-90°C, the operating pressure is 20-90 kPa, and the reflux ratio is 0.5-3.0; in step (5), the operating temperature of the top of the second distillation tower is 90-130°C, the operating pressure is 20-90 kPa, and the reflux ratio is 0.4-2.0.

[0021] Furthermore, the top water in step (4) is recovered and reused to replenish the top of the second absorption tower, thereby reusing the top waste water. No waste water is generated in this process. Due to the adoption of the above technical solution, compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention solves the problem that the traditional combustion method cannot recycle the high-value components in the tail gas. While the tail gas meets the emission standards after purification, it realizes the comprehensive recycling of the high-value components in the tail gas of the chemical polyimide film production, and obtains qualified sodium acetate, isoquinoline and DMF / DMAC finished products, which can be reused in the production line or sold as products.

[0022] (2) By adopting a combined process of absorption separation, salt recovery and distillation, the operation is stable. Compared with the traditional combustion method, the equipment investment cost is low and the subsequent high cost of catalyst replacement is eliminated, which greatly reduces the cost of tail gas treatment in the production of chemical polyimide film. In addition, this process does not produce wastewater, which solves environmental problems and has great economic benefits.

[0023] (3) The present invention achieves the removal of acetic acid and isoquinoline in the DMF / DMAC solvent during the tail gas absorption stage, thereby solving the problems of azeotropy formed by acetic acid and DMF / DMAC, complicated subsequent separation and refining equipment, and high difficulty in operation, and realizes the reuse of distillation wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a process flow of a tail gas recovery device for producing a polyimide film by a chemical method provided by the present invention; In the figure: 1. first absorption tower; 2. first circulation pump; 3. second circulation pump; 4. second absorption tower; 5. third circulation pump; 6. evaporator; 7. evaporative condenser; 8. vacuum pump; 9. crystallization equipment; 10. drying equipment; 11. first distillation tower; 12. second distillation tower; 13. first condenser; 14. first reboiler; 15. second condenser; 16. vacuum equipment. DETAILED DESCRIPTION

[0025] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0026] Reference Figure 1 A chemical method polyimide film production tail gas recovery device includes an absorption separation system, a salt recovery system and a distillation system; the absorption separation system includes a first absorption tower 1 and a matching first circulation pump 2, a second circulation pump 3, a second absorption tower 4 and a third circulation pump 5; the salt recovery system includes an evaporator 6, an evaporative condenser 7, a vacuum pump 8, a crystallization device 9, and a drying device 10; the distillation system includes a first distillation tower 11, a second distillation tower 12, a first condenser 13, a first reboiler 14, a second condenser 15, and a vacuum device 16.

[0027] The gas phase inlet of the first absorption tower 1 of the absorption and separation system is arranged at the bottom of the tower, and the tail gas of the chemical polyimide film production is collected and aggregated and connected to the inlet of the first absorption tower 1 through a pipeline; the liquid phase outlet of the bottom of the first absorption tower 1 is connected to the inlet of the first circulation pump 2, and the outlet of the first circulation pump 2 is divided into two branches, one of which is connected to the liquid inlet in the middle of the first absorption tower 1, and the other branch is connected to the liquid phase inlet of the evaporator 6 of the salt recovery system; a liquid collecting tray is arranged in the middle section of the first absorption tower 1, and the outlet of the liquid collecting tray is connected to the inlet of the second circulation pump 3, and the outlet of the second circulation pump 3 is connected to the first The top liquid inlet of the absorption tower 1 is connected; the gas phase outlet at the top of the first absorption tower 1 is connected to the gas phase inlet at the bottom of the second absorption tower 4; the kettle outlet of the second absorption tower 4 is connected to the inlet of the third circulation pump 5, and the outlet of the third circulation pump 5 is divided into two branches, one of which is connected to the liquid inlet in the middle of the second absorption tower 4, and the other branch is connected to the feed inlet of the first distillation tower 10 of the distillation system; a liquid collecting tray is arranged in the middle section of the second absorption tower 4, and the outlet of the liquid collecting tray is connected to the liquid inlet at the top of the first absorption tower 1 after pressurization by a pipeline connection pump; a fresh water inlet is arranged at the top of the second absorption tower 4; The evaporator 6 is provided with stirring and a jacket, and the gas phase outlet at the top of the evaporator 6 is connected to the gas phase inlet of the evaporative condenser 7; the gas phase outlet of the evaporative condenser 7 is connected to the inlet of the vacuum pump 8, and the liquid phase discharge port of the evaporative condenser 7 is connected to the liquid phase feed port in the middle of the first absorption tower 1 through a pipeline connecting pump; the liquid phase outlet of the evaporator 6 is divided into two branches, one of which is connected to the inlet of the crystallization device 9, and the other is connected to the inlet of the drying device 10; the crystallization device 9 is provided with a solid phase and a liquid phase outlet, the solid phase outlet is used to produce the acetate product to the outside, and the liquid phase outlet is divided into two branches, one of which is connected to the liquid phase inlet of the evaporator 6, and the other is used to produce the residual liquid to the outside; The gas phase outlet at the top of the first distillation tower 11 is connected to the feed port of the first condenser 13, the gas phase outlet of the first condenser 13 is connected to the vacuum equipment 16, the liquid phase outlet of the first condenser 13 is divided into two branches, one branch is refluxed to the liquid phase inlet at the top of the first distillation tower 11, and the other branch is used to produce water to the outside; the bottom discharge port of the first distillation tower 11 is divided into two branches, one branch is connected to the first reboiler 14, and the other branch is used to produce the distillation residue to the outside; the gas phase outlet at the bottom of the first distillation tower 11 is connected to the gas phase feed port of the second distillation tower 12; the gas phase outlet at the top of the second distillation tower 12 is connected to the second condenser 15, the gas phase outlet of the second condenser 15 is connected to the vacuum equipment 16, the liquid phase outlet of the second condenser 15 is divided into two branches, one branch is refluxed to the liquid phase inlet at the top of the second distillation tower 12, and the other branch produces the DMF / DMAC finished product; the reactor outlet of the second distillation tower 12 is connected to the reactor feed port of the first distillation tower 11 after being pressurized by a pump. Example 1

[0028] The present invention utilizes the chemical method polyimide film production tail gas recovery device to disclose a tail gas comprehensive recovery and utilization process. The tail gas produced by the PI film is mainly composed of: DMF / DMAC content 1-15g / Nm 3 , acetic acid (acetic anhydride) content 0.4~5g / Nm 3 , isoquinoline content 0.05~1g / Nm 3 , the rest is water, air and a small amount of polymer, dust, tar, etc., the exhaust gas temperature is 80~400℃; refer to Figure 1 , specifically including the following steps: (1) The high-temperature tail gas from the PI film production line is collected and transported to the first absorption tower 1; the high-temperature tail gas is used in the first absorption tower 1 to remove acetic acid and isoquinoline in the tail gas with alkali solution and DMF / DMAC aqueous solution as absorbents, and the operating temperature of the first absorption tower is 5~55°C; the acetic acid is neutralized to form acetate and enters the bottom liquid of the first absorption tower 1 with isoquinoline. The alkali solution is added from the middle part of the tower or the bottom of the tower, and the acetic acid in the tail gas is neutralized and salted in the lower part of the tower before being removed; the pH value of the bottom liquid is controlled in the range of 4~6, and the acetate content is 10~40% (mass percentage); the DMF / DMAC aqueous solution is added from the top of the tower and sprayed downward through a distributor to achieve the removal of isoquinoline.

[0029] (2) The tail gas is passed through the first absorption tower 1 in step (1) to remove acetic acid and isoquinoline, and then enters the second absorption tower 4. The top of the second absorption tower 4 uses water as an absorbent to recover DMF / DMAC in the tail gas. The operating temperature of the second absorption tower is 5-40°C. A high-concentration DMF / DMAC recovery liquid is obtained in the kettle, and the DMF / DMAC content in the recovery liquid is 40%-80% (mass percentage); the tail gas is purified by the second absorption tower and meets the emission standards, wherein the DMAC / DMF concentration is less than 20 mg / m 3 .

[0030] (3) In step (1), the bottom liquid of the first absorption tower 1 is regularly taken out to the evaporator 6, and the washing liquid is evaporated and concentrated. The evaporator is operated in vacuum, the evaporation temperature is 50~130℃, and the operating pressure is 10~90kPa; the gas phase produced by the evaporator 6 is condensed to obtain water and DMF / DMAC mixed liquid, which is returned to the top of the first absorption tower 1 for liquid replenishment; the evaporated mother liquor is evaporated and concentrated to recover DMF and water, and then sent to the crystallization device 9 for separation and purification to obtain a qualified acetate product. The crystallization device 9 is one or a combination of evaporation crystallization and cooling crystallization. The evaporated mother liquor is crystallized, centrifuged and washed to obtain a qualified acetate product. The crystallization mother liquor is returned to the evaporator, and part of it is taken out as residual liquid. After the isoquinoline in the mother liquor is concentrated to a certain concentration, it is evaporated to dryness in the evaporator, and water is added to dissolve it. Since isoquinoline is insoluble in water, it is separated from the sodium acetate aqueous solution, and the lower oil phase is taken and dried to obtain the isoquinoline product; (4) The DMF / DMAC recovery liquid obtained in step (2) is transported to a first distillation tower 11 for distillation separation. Under the action of a first reboiler 14, a first condenser 13 and a certain reflux ratio, water is produced from the top of the tower and a crude DMF / DMAC product is obtained in the bottom of the tower. The operating temperature at the top of the first distillation tower 11 is 60-90° C., the operating pressure is 20-90 kPa, and the reflux ratio is 0.5-3.0.

[0031] (5) The second distillation tower 12 and the first distillation tower 11 share a reboiler. The vapor rising from the bottom of the first distillation tower 11 is partially extracted to the second distillation tower 12 for further refining treatment. The gas phase extracted from the top of the second distillation tower 12 is condensed to obtain a DMF / DMAC product that meets the index requirements, and the bottom liquid is returned to the first distillation tower 11. The top operating temperature of the second distillation tower 12 is 90~130℃, the operating pressure is 20~90kPa, and the reflux ratio is 0.4~2.0. The distillation residue is regularly extracted from the bottom of the first distillation tower 11. Example 2

[0032] In this implementation, the tail gas volume from the chemical polyimide film production line is 30000Nm 3 / h, the main components of tail gas are: DMF content 9.5g / Nm 3 , acetic acid (acetic anhydride) content 2.5g / Nm 3 , isoquinoline content 0.5g / Nm 3 , the rest is water, air and a small amount of polymer, dust, tar, etc., the tail gas temperature is 130°C and the pressure is 5Kpa. The present invention is applied to the production tail gas recovery and includes the following steps: The high-temperature tail gas from the production line is collected and passed into the first absorption tower 1. The absorbent is NaOH solution and DMF aqueous solution. The absorption temperature is 45°C. The acetic acid and isoquinoline in the tail gas are removed. After the tail gas leaves the first absorption tower, it enters the second absorption tower 4. The absorbent is water. The absorption temperature is 30°C. The gas after absorption is discharged from the top of the tower in compliance with the standards to obtain a DMF aqueous solution with a concentration of 70wt% (mass percentage). The bottom liquid of the first absorption tower 1 is regularly taken out to the evaporator 6. The bottom liquid has a sodium acetate concentration of 28wt%, an evaporation temperature of 75°C, and an operating pressure of 15kPa (absolute pressure). The gas phase is condensed and returned to the first absorption tower 1. The liquid phase is concentrated and taken out to the crystallization equipment 9. After evaporation, crystallization, centrifugal separation and washing, a qualified sodium acetate product is obtained. After the isoquinoline in the crystallization mother liquor is concentrated to a certain concentration, it is evaporated to dryness in the evaporator 6, water is added to dissolve and wash, and the lower oil phase is taken out and dried by the drying equipment 10 to obtain the isoquinoline product; the DMF recovery liquid obtained from the bottom of the second absorption tower 2 is transported to the first distillation tower 11, and is separated at the top operating temperature of 69.7°C, the operating pressure of 30kPa (absolute pressure), and the reflux ratio of 0.8, and the DMF crude product is obtained at the bottom of the first distillation tower 11, and the water produced at the top of the tower is returned to the top of the second absorption tower 4 for water replenishment; the steam rising from the bottom of the first distillation tower 11 is partially produced to the second distillation tower 12 for further refining treatment, and is separated at the top operating temperature of 120.3°C, the operating pressure of 30kPa (absolute pressure), and the reflux ratio of 0.6, and the gas phase produced at the top of the second distillation tower 12 is condensed to obtain a high-purity DMF finished product.

[0033] After the above-mentioned process treatment, the comprehensive recovery and utilization of high-value components in the tail gas of chemical polyimide film production is achieved. The purity (mass percentage) of separated sodium acetate is 99%, the purity of isoquinoline is 97%, and the purity (mass percentage) of DMF is 99.9%, which can be reused in the production line or sold as products. Example 3

[0034] In this implementation, the tail gas volume from the chemical polyimide film production line is 26000Nm 3 / h, the main components of tail gas are: DMAC content 3.08g / Nm 3 , acetic acid (acetic anhydride) content 0.76g / Nm 3 , isoquinoline content 0.1g / Nm 3 , the rest is water, air and a small amount of polymer, dust, tar, etc., the tail gas temperature is 80°C and the pressure is 3Kpa. The present invention is applied to the production tail gas recovery and includes the following steps: The high-temperature tail gas from the production line is collected and passed into the first absorption tower 1. The absorbent is NaOH solution and DMAC aqueous solution. The absorption temperature is 43°C. The acetic acid and isoquinoline in the tail gas are removed. After the tail gas leaves the first absorption tower, it enters the second absorption tower 4. The absorbent is water. The absorption temperature is 30°C. The gas after absorption is discharged from the top of the tower in compliance with the standards to obtain a DMAC aqueous solution with a concentration of 55wt% (mass percentage). The bottom liquid of the first absorption tower 1 is regularly taken out to the evaporator 6. The bottom liquid has a sodium acetate concentration of 25wt%, an evaporation temperature of 105°C, and an operating pressure of 10kPa (absolute pressure). The gas phase is condensed and returned to the first absorption tower 1. The liquid phase is concentrated and taken out to the crystallization equipment 9. After cooling, crystallization, centrifugal separation and washing, a qualified sodium acetate trihydrate product is obtained. After the isoquinoline in the crystallization mother liquor is concentrated to a certain concentration, it is evaporated to dryness in the evaporator 6, water is added to dissolve and wash, and the lower oil phase is taken out and dried by the drying equipment 10 to obtain the isoquinoline product; the DMAC recovery liquid obtained in the bottom of the second absorption tower 2 is transported to the first distillation tower 11, and the separation is carried out at the top operating temperature of 75.8°C, the operating pressure of 40kPa (absolute pressure), and the reflux ratio of 1.0, and the DMAC crude product is obtained at the bottom of the first distillation tower 11, and the water produced at the top of the tower is returned to the top of the second absorption tower 4 for water replenishment; the steam rising from the bottom of the first distillation tower 11 is partially produced to the second distillation tower 12 for further refining treatment, and the separation is carried out at the top operating temperature of 133.4°C, the operating pressure of 40kPa (absolute pressure), and the reflux ratio of 0.7. The gas phase produced at the top of the second distillation tower 12 is condensed to obtain a high-purity DMAC finished product.

[0035] After the above-mentioned process treatment, the comprehensive recovery and utilization of high-value components in the tail gas of chemical polyimide film production is achieved. The purity (mass percentage) of the separated sodium acetate trihydrate is 98%, the purity of isoquinoline is 97%, and the purity of DMF (mass percentage) is 99.9%, which can be reused in the production line or sold as products.

[0036] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A comprehensive recovery and utilization device for tail gas from the production of chemical polyimide film, characterized in that: The device comprises an absorption separation system, a salt recovery system and a distillation system; the absorption separation system comprises a first absorption tower (1) and a matching first circulation pump (2), a second circulation pump (3), a second absorption tower (4) and a third circulation pump (5); the salt recovery system comprises an evaporator (6), an evaporative condenser (7), a vacuum pump (8), a crystallization device (9) and a drying device (10); the distillation system comprises a first distillation tower (11), a second distillation tower (12), a first condenser (13), a first reboiler (14), a second condenser (15) and a vacuum device (16).

2. The comprehensive recovery and utilization device for tail gas from chemical polyimide film production according to claim 1, characterized in that: The gas phase inlet of the first absorption tower (1) of the absorption and separation system is arranged at the bottom of the tower, and the tail gas from the production of chemical polyimide film is collected and aggregated and connected to the inlet of the first absorption tower (1) through a pipeline; the liquid phase outlet of the bottom of the first absorption tower (1) is connected to the inlet of the first circulation pump (2), and the outlet of the first circulation pump (2) is divided into two branches, one of which is connected to the liquid inlet in the middle of the first absorption tower (1), and the other branch is connected to the liquid phase inlet of the evaporator (6) of the salt separation and recovery system; a liquid collecting tray is arranged in the middle of the first absorption tower (1), and the outlet of the liquid collecting tray is connected to the inlet of the second circulation pump (3), and the outlet of the second circulation pump (3) is connected to the first absorption tower (1). The first absorption tower (1) is connected to the top liquid inlet of the absorption tower (1); the gas phase outlet at the top of the first absorption tower (1) is connected to the gas phase inlet at the bottom of the second absorption tower (4); the bottom outlet of the second absorption tower (4) is connected to the inlet of a third circulation pump (5), and the outlet of the third circulation pump (5) is divided into two branches, one of which is connected to the liquid inlet in the middle of the second absorption tower (4), and the other branch is connected to the feed inlet of the first distillation tower (10) of the distillation system; a liquid collecting tray is arranged in the middle of the second absorption tower (4), and the outlet of the liquid collecting tray is connected to the liquid inlet at the top of the first absorption tower (1) after being pressurized by a pipeline connection pump; and a fresh water inlet is arranged at the top of the second absorption tower (4).

3. The comprehensive recovery and utilization device for tail gas from chemical polyimide film production according to claim 2, characterized in that: The evaporator (6) is provided with a stirring device and a jacket. The gas phase outlet at the top of the evaporator (6) is connected to the gas phase inlet of the evaporative condenser (7); the gas phase outlet of the evaporative condenser (7) is connected to the inlet of a vacuum pump (8); the liquid phase outlet of the evaporative condenser (7) is connected to the liquid phase feed inlet at the top of the first absorption tower 1 via a pipeline connecting the pump; the liquid phase outlet of the evaporator (6) is divided into two branches, one of which is connected to the inlet of the crystallization device (9) and the other is connected to the inlet of the drying device (10); the crystallization device (9) is provided with a solid phase outlet and a liquid phase outlet, the solid phase outlet is used to produce the acetate product, and the liquid phase outlet is divided into two branches, one of which is connected to the liquid phase inlet of the evaporator (6) and the other is used to produce the residual liquid.

4. The comprehensive recovery and utilization device for tail gas from chemical polyimide film production according to claim 3 is characterized in that: The gas phase outlet at the top of the first distillation tower (11) is connected to the feed port of the first condenser (13), the gas phase outlet of the first condenser (13) is connected to the vacuum device (16), the liquid phase outlet of the first condenser (13) is divided into two branches, one branch is refluxed to the liquid phase inlet at the top of the first distillation tower (11), and the other branch is used to produce water externally; the outlet at the bottom of the first distillation tower (11) is divided into two branches, one branch is connected to the first reboiler (14), and the other branch is used to produce the distillation residue externally; the first distillation tower (11) ) is connected to the gas phase feed port of the second distillation tower (12); the gas phase outlet at the top of the second distillation tower (12) is connected to the second condenser (15); the gas phase outlet of the second condenser (15) is connected to the vacuum device (16); the liquid phase outlet of the second condenser (15) is divided into two branches, one of which is refluxed to the liquid phase inlet at the top of the second distillation tower (12); and the other branch is used to produce the DMF / DMAC product; the bottom outlet of the second distillation tower (12) is connected to the bottom feed port of the first distillation tower (11) after being pressurized by a pump.

5. A comprehensive recovery and utilization process of tail gas from the production of polyimide film by chemical method, using the comprehensive recovery and utilization device of tail gas as claimed in claim 4, characterized in that: The steps include: (1) High-temperature tail gas from a PI film production line is collected and transported to a first absorption tower (1), where acetic acid and isoquinoline in the tail gas are removed using alkaline solution and DMF / DMAC aqueous solution as absorbents. Acetic acid is neutralized to form acetate, which enters the bottom liquid of the first absorption tower (1) together with isoquinoline; (2) the tail gas passes through the first absorption tower (1) in step (1) to remove acetic acid and isoquinoline, and then enters the second absorption tower (4). The top of the second absorption tower (4) uses water as an absorbent to recover DMF / DMAC in the tail gas, and a high-concentration DMF / DMAC recovery liquid is obtained in the bottom of the tower. The tail gas is purified by the second absorption tower (4) and then meets the emission standards; (3) In step (1), the bottom liquid of the first absorption tower (1) is regularly taken out of the salt separation recovery system, and the washing liquid is evaporated and concentrated by the evaporator (6). The gas phase of the evaporator (6) is condensed to obtain water and DMF / DMAC mixed liquid, which is returned to the first absorption tower (1) for replenishment; the mother liquor is evaporated and concentrated to recover the remaining solvent, and then sent to the crystallization device (9) for separation and purification to obtain a qualified acetate product; after the isoquinoline in the mother liquor is concentrated to a certain concentration, it is evaporated to dryness in the evaporator, and water is added to dissolve it. Since isoquinoline is insoluble in water, it is separated from the sodium acetate aqueous solution, and the lower oil phase is taken and dried to obtain the isoquinoline product; (4) The DMF / DMAC recovery liquid obtained in step (2) is transported to a first distillation tower (11) for distillation separation. Under the action of a bottom reboiler, a top condenser and a certain reflux ratio, water is produced from the top of the tower and a crude DMF / DMAC product is obtained in the bottom of the tower; (5) The second distillation tower (12) and the first distillation tower (11) share a reboiler. The vapor rising from the bottom of the first distillation tower (11) is partially extracted and sent to the second distillation tower (12) for further refining treatment. The gas phase extracted from the top of the second distillation tower (12) is condensed to obtain a DMF / DMAC product that meets the index requirements. The bottom liquid is returned to the first distillation tower (11); the distillation residue is regularly extracted from the bottom of the first distillation tower (11).

6. A comprehensive recovery and utilization process for tail gas from chemical polyimide film production according to claim 5, characterized in that: The temperature of the high-temperature tail gas produced by the PI film in step (1) is 80-260°C; the operating temperature of the first absorption tower (1) is 5-55°C. The operating temperature of the second absorption tower (2) in step (2) is 5-40°C; the alkali solution is added from the middle of the tower or the bottom of the tower, and the acetic acid in the tail gas is neutralized and salted in the lower part of the tower before being removed; the amount of the alkali solution added is controlled by the pH of the bottom liquid of the first absorption tower (1), and the pH value control range is 4-6; the DMF / DMAC aqueous solution is added from the top of the tower and sprayed downward through a distributor to further achieve the removal of isoquinoline.

7. The process for comprehensive recovery and utilization of tail gas from chemical polyimide film production according to claim 5, characterized in that: The DMF / DMAC aqueous solution is derived from the recovered liquid from the top section of the second absorption tower in step (2), the recovered liquid from the bottom of the second absorption tower, the water and the DMF / DMAC mixed liquid in step (3), or one or more thereof; the acetate content in the bottom liquid of the first absorption tower (1) in step (1) is 10-40% (mass percentage); the DMF / DMAC content in the DMF / DMAC recovered liquid obtained from the bottom of the tower in step (2) is 40%-80% (mass percentage); and the tail gas is purified by the second absorption tower (4) and the DMAC / DMF concentration is less than 20 mg / m 3 .

8. The process for comprehensive recovery and utilization of tail gas from chemical polyimide film production according to claim 5, characterized in that: The evaporator (6) is operated in vacuum, the evaporation temperature is 50-130° C., and the operating pressure is 10-90 kPa. The crystallization separation and refining process described in step (3) is one of evaporation crystallization and cooling crystallization or a combination of processes. After the evaporation mother liquor is crystallized, centrifuged and washed, a qualified acetate product is obtained. The crystallization mother liquor is returned to the evaporator (6), and part of it is extracted as residual liquid.

9. The process for comprehensive recovery and utilization of tail gas from chemical polyimide film production according to claim 5, characterized in that: The isoquinoline drying process in step (3) is molecular sieve or anhydrous sodium sulfate drying; the top water in step (4) is recovered and reused to the top of the second absorption tower (4) for water replenishment, thereby realizing the reuse of the top waste water.

10. The process for comprehensive recovery and utilization of tail gas from chemical polyimide film production according to claim 5, characterized in that: In step (4), the operating temperature of the top of the first distillation tower is 60-90°C, the operating pressure is 20-90 kPa, and the reflux ratio is 0.5-3.0; in step (5), the operating temperature of the top of the second distillation tower is 90-130°C, the operating pressure is 20-90 kPa, and the reflux ratio is 0.4-2.0.

Images