Reaction and separation combined system for producing ethylene-vinyl alcohol copolymer

Abstract

The application provides a reaction and separation combined system for preparing ethylene-vinyl alcohol copolymer, and relates to the technical field of chemical reaction systems, which comprises a fiber membrane reactor and a fiber membrane neutralizer, the gas phase outlet of the fiber membrane neutralizer is connected with the gas phase outlet of the fiber membrane reactor and a low-pressure separation tower, and the reaction liquid outlet of the fiber membrane neutralizer is connected with a water washing and filtering system; the water washing and filtering system, a low-pressure separation system and a high-pressure separation system; the fiber membrane reactor is used for the reaction of EVA to EVOH, can provide a specific surface area of 1000-5000 m2 / m3, forms an ultra-thin liquid film of 1-10 microns, the mass transfer coefficient is improved by 1-2 orders of magnitude compared with a traditional stirred tank, the alcoholysis degree fluctuation is controlled within ±0.3 %, the residence time is shortened to 1 / 5-1 / 10 of that of the traditional tank type, the alkali consumption is reduced by 30 %-50 %, the utilization rate of catalyst is increased by more than 20 %, and the continuous and green preparation of high-quality EVOH is realized.

Description

Technical Field

[0001] This invention relates to the field of chemical reaction system technology, specifically to a reaction and separation system for preparing ethylene-vinyl alcohol copolymers, and more particularly to a reaction and separation system for preparing ethylene-vinyl alcohol copolymers using ethylene-vinyl acetate copolymers. Background Technology

[0002] Ethylene-vinyl alcohol copolymer (EVOH) combines the processability of polyethylene with the high barrier properties of polyvinyl alcohol. It has excellent oxygen barrier properties under dry conditions, as well as good oil resistance, transparency and mechanical strength. It is widely used in high-end fields such as food packaging and medical materials. Market demand is rising and the requirements for product purity and performance are constantly increasing.

[0003] Because vinyl alcohol monomers are highly susceptible to isomerization, EVOH cannot be prepared by direct copolymerization of ethylene and vinyl alcohol. Industrially, a two-step indirect synthesis method is commonly used: first, ethylene is copolymerized with vinyl acetate (VAM) to generate ethylene-vinyl acetate copolymer (EVA), and then EVA is converted to EVOH via alcoholysis. The alcoholysis reaction determines the degree of alcoholysis and overall properties of EVOH, while subsequent separation and purification directly affect product purity and production economics. The synergy between these two processes is key to improving production efficiency.

[0004] Currently, the reaction and separation systems for EVA to EVOH are independent and lack efficient synergy, resulting in numerous drawbacks. In the reaction stage, existing alcoholysis methods mostly employ inorganic metal base catalysts, which have low solubility and poor dispersibility, easily leading to low reaction efficiency, uneven alcoholysis degree of EVOH, and difficulty in removing metal ion impurities, thus degrading product performance. At the same time, the methyl acetate byproduct generated in the reaction cannot be removed in a timely manner, further reducing reaction efficiency and increasing separation difficulty.

[0005] In the separation and purification process, traditional processes are cumbersome, energy-intensive, and have poor separation results. Not only is it difficult to completely remove impurities, affecting product purity and failing to meet high-end demands, but there are also problems such as low solvent (mainly methanol) recovery rates, resource waste, and high production costs. Furthermore, the waste liquid generated during the separation process is difficult to treat and highly polluting, which is inconsistent with the current development trend of green chemistry and low-carbon production. Multiple purification operations also significantly extend the production cycle, increase water consumption, and raise production costs.

[0006] Currently, domestic EVOH production lines still lag behind in efficiency, purity, and energy consumption control. The core reason is the lack of an integrated system that coordinates reaction and separation, resulting in large fluctuations in product quality and high energy consumption, which restricts domestic substitution and the expansion of high-end applications.

[0007] Given the shortcomings of existing technologies, developing a combined system that can achieve efficient and synergistic EVA alcoholysis and separation, solve the above-mentioned technical defects, and is simple, environmentally friendly, and scalable is an urgent technical challenge to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a reaction and separation combination system for preparing ethylene-vinyl alcohol copolymers.

[0009] The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymers provided by the present invention includes: The fiber membrane reactor is filled with a fiber structure. The mixed raw material inlet of the fiber membrane reactor is connected to the metal alkali catalyst feed line and the EVA solution feed line. The gas inlet of the fiber membrane reactor is connected to the first stripping gas feed line, and the reaction liquid outlet and gas phase outlet of the fiber membrane reactor are connected to the downstream fiber membrane neutralizer. The fiber membrane neutralizer is located downstream of the fiber membrane reactor and is filled with a fiber structure. The material inlet of the fiber membrane neutralizer is connected to the reaction liquid outlet and neutralizing agent feed line of the fiber membrane reactor, and the gas inlet of the fiber membrane neutralizer is connected to the second stripping gas feed line. The gas phase outlet of the fiber membrane neutralizer and the gas phase outlet of the fiber membrane reactor are simultaneously connected to the low-pressure separation tower, and the reaction liquid outlet of the fiber membrane neutralizer is connected to the water washing and filtration system. The water washing and filtration system includes a water washing tank, a filter and a dryer connected in sequence. The material inlet of the water washing tank is connected to the reaction liquid outlet of the fiber membrane neutralizer. After the reaction liquid is processed by the water washing tank, the filter and the dryer, it forms powder EVOH, which is sent to the outside from the powder product outlet of the dryer. The low-pressure separation system includes a low-pressure separation tower for separating and recovering methanol from the stripping gas generated by the fiber membrane reactor and the fiber membrane neutralizer. The separated methanol is sent to the outside from the discharge port at the bottom of the low-pressure separation tower, and the separated material is sent to the high-pressure separation tower from the gas phase outlet of the low-pressure separation tower. The high-pressure separation system includes a high-pressure separation tower for separating and recovering methyl acetate from materials processed by a low-pressure separation tower. The separated methyl acetate is discharged from the outlet at the bottom of the high-pressure separation tower to the outside.

[0010] Preferably, the fiber membrane reactor includes an upper shell, a middle shell, and a lower shell. The top of the upper shell is provided with a gas phase outlet, and the bottom side of the upper shell is provided with a mixing raw material inlet. The fiber membrane reactor has a bundled fiber membrane cylinder inside the shell, which is filled with stainless steel fiber filaments. Connecting cylinder plates are provided at both ends. The bundled fiber membrane cylinder is fixed to the upper cylinder plate and the lower cylinder plate through connecting flanges between the upper shell and the middle shell, and between the middle shell and the lower shell. The fiber membrane reactor has a gas inlet on the upper side of the lower shell, which is connected to the first stripping gas feed line, and a reaction liquid outlet at the bottom. The fiber membrane neutralizer includes an upper shell, a middle shell, and a lower shell. The top of the upper shell of the fiber membrane neutralizer is provided with a gas phase outlet, and the bottom side of the upper shell is provided with a material inlet. The fiber membrane neutralizer has a bundled fiber membrane cylinder inside the shell, which is filled with stainless steel fiber structure. Connecting cylinder plates are provided at both ends. The bundled fiber membrane cylinder is fixed to the upper cylinder plate and the lower cylinder plate through connecting flanges between the upper shell and the middle shell, and between the middle shell and the lower shell. The fiber membrane neutralizer has a gas inlet on the upper side of the lower shell, which is connected to the second stripping gas feed line, and a reaction liquid outlet at the bottom.

[0011] Preferably, the water washing filtration system is a multi-stage water washing filtration system, including a primary water washing filtration system, a secondary water washing filtration system, and a tertiary water washing filtration system; The primary water washing and filtration system includes a primary water washing tank and a primary filter. The material inlet of the primary water washing tank is connected to the reaction liquid outlet of the fiber membrane neutralizer, and the material inlet of the primary filter is connected to the material outlet of the primary water washing tank. The two-stage water washing and filtration system includes a two-stage water washing tank and a two-stage filter. The material inlet of the two-stage water washing tank is connected to the solid phase outlet of the first-stage filter, and the material inlet of the two-stage filter is connected to the material outlet of the two-stage water washing tank. The three-stage water washing and filtration system includes a three-stage water washing tank and a three-stage filter. The material inlet of the three-stage water washing tank is connected to the solid phase outlet of the two-stage filter, the material inlet of the three-stage filter is connected to the material outlet of the three-stage water washing tank, and the solid phase outlet of the three-stage filter is connected to the material inlet of the dryer. The gas phase outlets of the primary washing tank, secondary washing tank, tertiary washing tank, and dryer are all connected to the low-pressure vent bus.

[0012] Preferably, it also includes a primary screw conveyor, a secondary screw conveyor, and a tertiary screw conveyor; The feed inlet of the primary screw conveyor is connected to the solid phase outlet of the primary filter, and the discharge outlet of the primary screw conveyor is connected to the material inlet of the secondary washing tank. The feed inlet of the secondary screw conveyor is connected to the solid phase outlet of the secondary filter, and the discharge outlet of the secondary screw conveyor is connected to the material inlet of the tertiary washing tank. The feed inlet of the three-stage screw conveyor is connected to the solid phase outlet of the three-stage filter, and the discharge outlet of the three-stage screw conveyor is connected to the material inlet of the dryer.

[0013] Preferably, it also includes a primary liquid phase collection tank, a secondary liquid phase collection tank, and a tertiary liquid phase collection tank; The liquid phase inlets of the primary liquid phase collection tank, the secondary liquid phase collection tank, and the tertiary liquid phase collection tank are respectively connected to the liquid phase outlets of the primary filter, the secondary filter, and the tertiary filter, and the gas phase outlets of the primary liquid phase collection tank, the secondary liquid phase collection tank, and the tertiary liquid phase collection tank are all connected to the low-pressure vent bus. The material outlet of the tertiary liquid phase collection tank is connected to the material inlet of the secondary water washing tank, the material outlet of the secondary liquid phase collection tank is connected to the material inlet of the primary water washing tank, and the material outlet of the primary liquid phase collection tank is connected to the methanol separation system.

[0014] Preferably, it also includes a condensate buffer tank; The gas phase outlet of the fiber membrane neutralizer merges with the gas phase outlet of the fiber membrane reactor, and is then connected to the condensate buffer tank via a stripper gas cooler. The gas phase outlet of the condensate buffer tank is connected to the vent bus, and the liquid phase outlet of the condensate buffer tank is connected to the low-pressure separation tower. The low-pressure separation system also includes a reflux tank at the top of the low-pressure separation tower. The feed inlet of the low-pressure separation tower is connected to the discharge outlet at the bottom of the condensate buffer tank. The gas phase outlet of the low-pressure separation tower is connected to the feed inlet of the reflux tank at the top of the low-pressure separation tower through a cooler at the top of the low-pressure separation tower. The discharge outlet at the bottom of the low-pressure separation tower is connected to the outside. The liquid phase outlet of the reflux tank at the top of the low-pressure separation tower is divided into two paths: one path is connected to the reflux port of the low-pressure separation tower, and the other path is connected to the feed port of the high-pressure separation tower. The gas phase outlet of the reflux tank at the top of the low-pressure separation tower is connected to the vent bus. The gas phase at the top of the low-pressure separation tower is condensed by the cooler at the top of the low-pressure separation tower and then enters the reflux tank at the top of the low-pressure separation tower. The separated solvent methanol is sent to the outside through the outlet of the low-pressure separation tower. The reflux tank at the top of the low-pressure separation tower is used to buffer and collect the reaction liquid cooled by the cooler at the top of the low-pressure separation tower. The reaction liquid is divided into two paths: one path flows back to the low-pressure separation tower through the reflux port, and the other path is sent to the high-pressure separation tower. The outlet of the reflux tank at the top of the low-pressure separation tower is connected to the vent bus.

[0015] Preferably, the high-pressure separation system further includes a high-pressure separation tower top reflux tank; The feed inlet of the high-pressure separation tower is connected to the discharge outlet of the low-pressure separation tower, the gas outlet of the high-pressure separation tower is connected to the feed inlet of the high-pressure separation tower top reflux tank through the high-pressure separation tower top cooler, and the discharge outlet of the high-pressure separation tower is connected to the outside. The liquid outlet of the high-pressure separation tower top reflux tank is divided into two paths: one path is connected to the reflux port of the high-pressure separation tower, and the other path is connected to the reflux liquid inlet of the condensate buffer tank. The gas outlet of the high-pressure separation tower top reflux tank is connected to the vent bus. The reaction gas formed after separation in the high-pressure separation tower passes through the top cooler of the high-pressure separation tower and then enters the top reflux tank of the high-pressure separation tower from the gas outlet. The separated solvent, methyl acetate, is sent to the outside through the discharge outlet of the high-pressure separation tower. The high-pressure separation tower top reflux tank is used to buffer and collect methanol cooled by the high-pressure separation tower top cooler. The reaction liquid is divided into two paths: one path flows back to the high-pressure separation tower through the reflux port, and the other path flows back to the condensate buffer tank. The gas outlet of the high-pressure separation tower top reflux tank is connected to the vent bus.

[0016] Preferably, it also includes a methanol separation system, comprising a methanol separation tower and a methanol separation tower top reflux tank; The inlet of the methanol separator is connected to the liquid phase outlet of the filter, the outlet of the methanol separator is connected to the inlet of the methanol separator top reflux tank through the methanol separator top cooler, and the outlet of the methanol separator is connected to downstream equipment. The liquid outlet at the bottom of the methanol separator top reflux tank is divided into two paths: one path connects to the reflux port of the methanol separator, and the other path connects to the outside. The gas outlet of the methanol separator top reflux tank is connected to the vent bus. The methanol separation tower is used to separate methanol from the liquid discharged by the filter. The separated gaseous methanol is condensed after passing through the methanol separation tower top cooler and then enters the methanol separation tower top reflux tank. The waste liquid formed after separation is discharged to downstream equipment through the discharge port at the bottom of the methanol separation tower. The methanol separator top reflux tank is used to buffer and collect methanol cooled by the methanol separator top cooler. The methanol is divided into two paths: one path flows back to the methanol separator through the reflux port, and the other path is sent to the outside. The gas phase outlet of the methanol separator top reflux tank is connected to the vent bus.

[0017] Preferably, it also includes a wastewater treatment system, which includes wastewater recycling facilities, a recycling tank, and a circulating water pump; The wastewater inlet of the wastewater recovery facility is connected to the outlet at the bottom of the methanol separation tower, the recovered water outlet of the wastewater recovery facility is connected to the inlet of the recovered water tank, and the solids outlet of the wastewater recovery facility is connected to the outside of the boundary. The gas phase outlet of the recovery water tank is connected to the high-pressure vent line, the water inlet of the recovery water tank is connected to the outside, and the water outlet of the recovery water tank is connected to the water washing and filtration system through a circulating water pump.

[0018] Preferably, the gas phase outlet of the washing vessel and the dryer is connected to the low-pressure vent bus; The low-pressure vent bus is connected to the gas phase inlet of the gas-liquid separator, the gas outlet of the gas-liquid separator is connected to the vent bus through the low-pressure vent air booster, and the liquid phase outlet of the gas-liquid separator is connected to the condensate buffer tank.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs a fiber membrane reactor for the synthesis of ethylene-vinyl acetate copolymer (EVA) into ethylene-vinyl alcohol copolymer (EVOH). The fiber membrane reactor, with its unique fiber bundle structure and liquid film contact method, exhibits significant advantages in the EVA alcoholysis to EVOH preparation process. The reactor interior is composed of numerous highly elastic, self-healing fibers, providing an ultra-high phase contact specific surface area of ​​1000–5000 m² / m³. This allows the EVA organic phase and the alkaline alcoholysis solution to form an ultra-thin, stable two-phase liquid film of 1–10 μm on the fiber surface. The interphase mass transfer coefficient is increased by 1–2 orders of magnitude compared to traditional stirred tank reactors, greatly enhancing the interphase mass transfer process of the transesterification reaction. Compared to traditional stirred tank reactors, this structure avoids problems such as excessively high local alkali concentrations, uneven mixing, and severe backmixing, making the alcoholysis reaction gentler and more uniform. It can control the EVOH alcoholysis degree fluctuation within ±0.3%, effectively improving the consistency of EVOH alcoholysis degree, reducing polymer thermal degradation and side reactions, and significantly improving product color and transparency. Meanwhile, the reactor enables continuous operation, reducing residence time to 1 / 5 to 1 / 10 of that of traditional batch reactors. It features a compact size, increased catalyst utilization by more than 20%, and reduced alkali consumption by 30% to 50%. This improves production efficiency while reducing energy and alkali consumption, providing an efficient and feasible technical path for the continuous and green preparation of high-quality, high-barrier EVOH.

[0020] 2. This invention uses a fiber membrane neutralizer to neutralize acetic acid with excess sodium hydroxide in the reaction products. The alkaline solution forms a micron-scale continuous liquid film along the fiber surface, with a phase contact specific surface area of ​​1000–5000 m² / m³. The mass transfer coefficient is increased by 1–2 orders of magnitude compared to traditional stirred tank reactors, and the neutralization reaction rate and reaction conversion rate are significantly improved. The reaction process involves non-dispersed phase contact, avoiding emulsification and phase entrainment from the source. After the reaction, the two phases can be quickly and automatically separated, realizing the integration of reaction and separation, eliminating the need for post-processing units such as sedimentation and agglomeration. The mass transfer at the phase interface is uniform and stable, eliminating the problem of local excess alkali, and the pH control accuracy can reach ±0.1–±0.3.

[0021] 3. This invention removes methyl acetate through two separate stripping processes, sequentially in a fiber membrane reactor and a fiber membrane neutralizer. Compared to traditional single-stage stripping, this method offers significantly improved separation efficiency and synergistic advantages. The first stripping, performed in the fiber membrane reactor, utilizes the system's own temperature and the efficient mass transfer interface of the fiber membrane to remove most of the methyl acetate generated during alcoholysis online, reducing its inhibitory effect on subsequent reaction equilibrium and preventing the accumulation of methyl acetate in the system that could lead to increased side reactions. The second stripping, performed in the fiber membrane neutralizer, achieves deep removal of residual methyl acetate while neutralizing and dealkalizing. Leveraging the ultrathin liquid membrane and ultra-large specific surface area of ​​the fiber membrane, the combined two stripping processes can achieve a total methyl acetate removal rate approaching 100%.

[0022] 4. This invention employs a high-low pressure dual-tower distillation process combining a high-pressure distillation column and a low-pressure distillation column to separate the methanol-methyl acetate azeotropic system. This fully utilizes the significant differences in the azeotropic composition of the two substances under different pressures, breaking the azeotropic limitation and achieving efficient continuous distillation separation. Compared with traditional processes such as single-tower distillation and extractive distillation, the high-low pressure dual-tower process eliminates the need for extractants or entrainers, avoiding the impact of external components on product purity and reducing solvent recovery energy consumption. It yields high-purity methanol and methyl acetate products, with methanol purity reaching over 99.8 wt% and methyl acetate purity not less than 99.5 wt%.

[0023] 5. This invention employs a three-stage countercurrent washing process combined with centrifugal separation for desalination and impurity removal, achieving highly efficient and deep removal of residual sodium salts, methanol, and trace amounts of methyl acetate from the EVOH alcoholysis neutralization system. The three-stage countercurrent arrangement fully utilizes the concentration gradient of the washing solution, significantly improving washing efficiency and water utilization while reducing fresh water consumption. Combined with centrifugal separation, centrifugal force enables rapid solid-liquid separation, achieving complete separation of the polymer and aqueous phases in a short time. This effectively avoids emulsion entrainment and residual salt agglomeration, significantly reducing the ash and metal ion content of the product. This combined process offers high desalination rates and more thorough washing, reducing sodium ion content in the product to extremely low levels, ensuring the purity, color, and processing stability of the EVOH resin. Simultaneously, the process is continuous, highly automated, and requires minimal floor space. Compared to multi-stage static sedimentation processes, it significantly shortens separation time and improves processing efficiency, providing efficient, stable, and low-consumption post-processing support for the continuous production of high-quality EVOH.

[0024] 6. This process utilizes methanol recovery through distillation coupled with evaporation crystallization to treat wastewater, achieving the dual advantages of efficient wastewater recovery and full-process resource recycling. The distillation unit efficiently purifies methanol in the system, yielding high-purity methanol that can be recycled. This process boasts high methanol recovery rates and low losses, significantly reducing fresh solvent replenishment and production costs. Evaporation crystallization leverages the difference in solubility during evaporation to achieve stepwise separation of residual organic matter, byproduct salts, and the aqueous phase in the wastewater, completing deep desalination and concentration reduction under mild conditions. The wastewater treated by evaporation crystallization is stable in quality and has extremely low impurity content, allowing it to be directly reused in the three-stage countercurrent washing unit as process washing water, achieving closed-loop wastewater recycling and significantly reducing fresh water consumption and total wastewater discharge. Attached Figure Description

[0025] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0026] The diagram shows: 1. Fiber membrane reactor; 2. Fiber membrane neutralizer; 3. Reaction product booster pump; 4. Primary water wash feed pump; 5. Primary water wash tank; 6. Primary filter feed pump; 7. Primary filter; 8. Primary screw conveyor; 9. Secondary water wash tank; 10. Secondary filter feed pump; 11. Secondary filter; 12. Secondary screw conveyor; 13. Tertiary water wash tank; 14. Tertiary filter feed pump; 15. Tertiary screw conveyor; 16. Dryer; 17. Tertiary liquid phase collection tank; 18. Tertiary water wash booster pump; 19. Secondary liquid phase collection tank; 20. Secondary water wash booster pump; 21. Primary liquid phase collection tank; 22. Primary water wash booster pump; 23. Methanol separation tower; 24. Methanol separation tower top cooler; 25. Methanol separation tower top reflux tank; 26. Methanol separation tower top reflux tank. 27. Flow pump; 28. Methanol separator reboiler; 29. ​​Methanol separator bottom pump; 30. Wastewater recovery facility; 31. Recovered water tank; 32. Circulating water pump; 33. Gas-liquid separator; 34. Low-pressure venting air booster; 35. Condensate recovery pump; 36. Stripping gas cooler; 37. Condensate buffer tank; 38. Condensate booster pump; 39. Low-pressure separation tower; 40. Low-pressure separation tower top cooler; 41. Low-pressure separation tower top reflux tank; 42. Low-pressure separation tower top reflux pump; 43. Low-pressure separation tower bottom reboiler; 44. Low-pressure separation tower bottom pump; 45. High-pressure separation tower; 46. High-pressure separation tower top cooler; 47. High-pressure separation tower top reflux pump; 48. High-pressure separation tower bottom reboiler; 49. High-pressure separation tower bottom pump; 50. Metal-alkali catalyst feed line; 51. EVA Solution feed line 52, First pipeline 53, Second pipeline 54, Third pipeline 55, Fourth pipeline 56, Fifth pipeline 57, Sixth pipeline 58, Seventh pipeline 59, Eighth pipeline 60, Ninth pipeline 61, Tenth pipeline 62, Eleventh pipeline 63, Twelfth pipeline 64, Thirteenth pipeline 65, Fourteenth pipeline 66, Fifteenth pipeline 67, Sixteenth pipeline 68, Seventeenth pipeline 69, Dryer vapor phase outlet 70, Eighteenth pipeline 71, Nineteenth pipeline 72, Twentieth pipeline 73, Twenty-first pipeline 74, Twenty-second pipeline 75, Twenty-third pipeline 76, Low-pressure vent bus 77, Twenty-fourth pipeline 78, Twenty-fifth pipeline 79, Twenty-sixth pipeline 80, Twenty-seventh pipeline 81, Twenty-eighth pipeline 82 Pipeline 29 (83), Pipeline 30 (84), Pipeline 31 (85), Pipeline 32 (86), Pipeline 33 (87), Vent Bus (88), Pipeline 34 (89), Pipeline 35 (90), Pipeline 36 (91), Pipeline 37 (92), Pipeline 38 (93), Pipeline 39 (94), Pipeline 40 (95), Pipeline 41 (96), Pipeline 42 (97), Pipeline 43 (98), Pipeline 44 (99), Pipeline 45 (100), Pipeline 46 (101), Pipeline 47 (102), Pipeline 48 (103), Pipeline 49 (104), Pipeline 50 (105), Pipeline 51 (106), Pipeline 52 (107), Pipeline 53 (108), Pipeline 54 (109)Pipeline 55 (110), Pipeline 56 (111), Pipeline 57 (112), Pipeline 58 (113), Pipeline 59 (114), Pipeline 60 (115), Pipeline 61 (116), Pipeline 62 (117), Pipeline 63 (118), Pipeline 64 (119), Pipeline 65 (120), Pipeline 66 (121), Pipeline 67 (122), Pipeline 68 (123), Pipeline 69 (124), Pipeline 70 (125), Pipeline 71 (126), Pipeline 72 (127), First Stripping Gas Feed Line (128), Second Stripping Gas Feed Line (129), Neutralizing Agent Feed Line (130). Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0028] This invention provides a reaction and separation system for preparing ethylene-vinyl alcohol copolymers, aiming to solve problems such as low solubility and poor dispersibility of metal alkali catalysts in the existing EVA alcoholysis process; inability to remove the generated methyl acetate byproduct in a timely manner; and cumbersome, energy-intensive, poorly separated, and costly traditional processes in the separation and purification stages. Figure 1 As shown, it can be divided into the following functional modules: (I): Main Reaction and Product Processing Module This module mainly includes a fiber membrane reactor 1, a fiber membrane neutralizer 2, a water washing and filtration system, and a dryer 17; The fiber membrane reactor 1 is filled with a fiber structure. The mixed raw material inlet of the fiber membrane reactor 1 is connected to the metal alkali catalyst feed line 51 and the EVA solution feed line 52. The gas inlet of the fiber membrane reactor 1 is connected to the first stripping gas feed line 128. The reaction liquid outlet and gas phase outlet of the fiber membrane reactor 1 are connected to the downstream fiber membrane neutralizer 2. The reaction byproduct methyl acetate is removed in situ in the fiber membrane reactor 1 by stripping gas and then condensed into a condensate tank. It is then separated by high and low pressure distillation after being pressurized. Fiber membrane reactor 1 includes a shell, which is divided into three parts: upper, middle, and lower. The three parts are connected by flanges, as detailed below: The upper shell is equipped with a jacket, and the sides are respectively equipped with a jacket inlet and a jacket outlet; the top is equipped with a gas phase outlet, which is connected to the inlet of the stripping gas cooler 36 through the 30th pipeline 84; the bottom side of the upper shell is equipped with a mixed raw material inlet, which is connected to the EVA solution feed line 52, and the metal alkali catalyst feed line 51 is connected to the EVA solution feed line 52. The middle shell is equipped with a jacket, and the jacket inlet and jacket outlet are respectively set on the side. Inside, there is a bundled fiber membrane cylinder, which is filled with a highly elastic, self-healing stainless steel fiber structure. Connecting cylinder plates are set at both ends. The bundled fiber membrane cylinder is fixed to the upper cylinder plate and the lower cylinder plate through the connecting flanges between the upper shell and the middle shell, and between the middle shell and the lower shell, to form a stable structure. A gas inlet is provided on the upper side of the lower shell and is connected to the first stripping gas feed line 128. A reaction liquid outlet is provided at the bottom and is connected to the inlet of the reaction product booster pump 3 through the first pipeline 53.

[0029] The fiber membrane neutralizer 2 is located downstream of the fiber membrane reactor 1 and is filled with a fiber structure. The material inlet of the fiber membrane neutralizer 2 is connected to the reaction liquid outlet and neutralizing agent feed line 130 of the fiber membrane reactor 1, and the gas inlet of the fiber membrane neutralizer 2 is connected to the second stripping gas feed line 129. The gas phase outlet of the fiber membrane neutralizer 2 and the gas phase outlet of the fiber membrane reactor 1 are simultaneously connected to the low-pressure separation tower 39, and the reaction liquid outlet of the fiber membrane neutralizer 2 is connected to the water washing and filtration system. The fiber membrane neutralizer 2 includes a housing, which is divided into three parts: upper, middle, and lower. The three parts are connected by flanges, as detailed below: The upper shell is equipped with a jacket, and the sides are respectively equipped with a jacket inlet and a jacket outlet; the top is equipped with a gas phase outlet, which is connected to the top gas phase line of the fiber membrane reactor 1, i.e., the thirtieth pipeline 84, through the thirty-first pipeline 85; the bottom side of the upper shell is equipped with a material inlet, which is connected to the outlet of the reaction product booster pump 3 through the second pipeline 54; the neutralizer feed line 130 is connected to the reaction product booster pump outlet line, i.e., the second pipeline 54. The middle shell is equipped with a jacket, and the jacket inlet and jacket outlet are respectively set on the side. Inside, there is a bundled fiber membrane cylinder, which is filled with a highly elastic, self-healing stainless steel fiber structure. Connecting cylinder plates are set at both ends. The bundled fiber membrane cylinder is fixed to the upper cylinder plate and the lower cylinder plate through the connecting flanges between the upper shell and the middle shell, and between the middle shell and the lower shell, to form a stable structure. A gas inlet is provided on the upper side of the lower shell, which is connected to the second stripping gas feed line 129. A reaction liquid outlet is provided at the bottom, which is connected to the inlet of the first-stage water washing feed pump 4 through the third pipeline 55 and the fourth pipeline 56.

[0030] The water washing and filtration system includes a water washing tank, a filter and a dryer 17 connected in sequence. The material inlet of the water washing tank is connected to the reaction liquid outlet of the fiber membrane neutralizer 2. After the reaction liquid is processed by the water washing tank, the filter and the dryer 17, it forms powder EVOH and is sent to the outside from the powder product outlet of the dryer 17. The water washing filtration system is a multi-stage system, including a primary water washing filtration system, a secondary water washing filtration system, and a tertiary water washing filtration system. The primary water washing filtration system includes a primary water washing vessel 5 and a primary filter 7. The material inlet of the primary water washing vessel 5 is connected to the reaction liquid outlet of the fiber membrane neutralizer 2, and the material inlet of the primary filter 7 is connected to the material outlet of the primary water washing vessel 5. The secondary water washing filtration system includes a secondary water washing vessel 9 and a secondary filter 11. The material inlet of the secondary water washing vessel 9 is connected to the solid phase outlet of the primary filter 7. The material inlet of the primary filter 11 is connected to the material outlet of the secondary washing tank 9; the tertiary washing and filtration system includes a tertiary washing tank 13 and a tertiary filter 15. The material inlet of the tertiary washing tank 13 is connected to the solid phase outlet of the secondary filter 11, the material inlet of the tertiary filter 15 is connected to the material outlet of the tertiary washing tank 13, and the solid phase outlet of the tertiary filter 15 is connected to the material inlet of the dryer 17; the gas phase outlets of the primary washing tank 5, the secondary washing tank 9, the tertiary washing tank 13, and the dryer 17 are all connected to the low-pressure vent bus 77.

[0031] Specifically, the primary washing tank 5, secondary washing tank 9, and tertiary washing tank 13 are all tank-type structures equipped with electric agitators to ensure full contact between the EVOH slurry and deionized water; the tanks are jacketed; the top has a material inlet connected to the primary washing feed pump 4, the secondary screw conveyor 12, and the tertiary screw conveyor 16 via the fourth pipeline 56, the eighth pipeline 60, and the twelfth pipeline 64, respectively. Simultaneously, the outlets of the secondary washing water booster pump 21, the tertiary washing water booster pump 19, and the circulating water pump 32 are connected to the sixty-first pipeline 116, the... Pipeline 113 (58th) and pipeline 110 (55th) are connected to pipeline 56 (4th), pipeline 60 (8th), and pipeline 64 (12th); a gas inlet is provided at the top and connected to the low-pressure vent bus 77 via pipelines 76 (23rd), 74 (21st), and 72 (19th); a material outlet is provided at the bottom and connected to the feed pumps 6 (1st stage filter), 10 (2nd stage filter), and 14 (3rd stage filter) via pipelines 57 (57th), 61 (9th), and 65 (13th); the shell is equipped with a jacket inlet and outlet. Specifically, the primary filter 7, secondary filter 11, and tertiary filter 15 are equipped with material inlets that are connected to the material outlets of the primary filter feed pump 6, secondary filter feed pump 10, and tertiary filter feed pump 14 via the sixth pipeline 58, the tenth pipeline 62, and the fourteenth pipeline 66, respectively. The liquid phase outlet is connected to the inlet of the primary liquid phase collection tank 22, the secondary liquid phase collection tank 20, and the tertiary liquid phase collection tank 18 via the sixty-second pipeline 117, the fifty-ninth pipeline 114, and the fifty-sixth pipeline 111, respectively. The solid phase outlet is connected to the primary spiral filter via the seventh pipeline 59, the eleventh pipeline 63, and the fifteenth pipeline 67, respectively. The inlets of conveyor 8, secondary screw conveyor 12, and tertiary screw conveyor 16 are connected; the outlets of secondary wash water booster pump 21, tertiary wash water booster pump 19, and circulating water pump 32 are connected to the fourth pipeline 56, the eighth pipeline 60, and the twelfth pipeline 64, as well as the primary filter 7, the secondary filter 11, and the tertiary filter 15, respectively, through the sixty-first pipeline 116, the fifty-eighth pipeline 113, and the fifty-fifth pipeline 110; preferably, the primary filter 7, the secondary filter 11, and the tertiary filter 15 are continuous centrifugal filters equipped with online cleaning and automatic unloading functions to ensure continuous operation and no material contamination.

[0032] In a preferred embodiment, the water washing and filtration system further includes a primary screw conveyor 8, a secondary screw conveyor 12, and a tertiary screw conveyor 16. The inlet of the primary screw conveyor 8 is connected to the solid phase outlet of the primary filter 7, and the outlet of the primary screw conveyor 8 is connected to the material inlet of the secondary washing vessel 9. The inlet of the secondary screw conveyor 12 is connected to the solid phase outlet of the secondary filter 11, and the outlet of the secondary screw conveyor 12 is connected to the material inlet of the tertiary washing vessel 13. The inlet of the tertiary screw conveyor 16 is connected to the solid phase outlet of the tertiary filter 15, and the outlet of the tertiary screw conveyor 16 is connected to the material inlet of the dryer 17. The primary screw conveyor 8, the secondary screw conveyor 12, and the tertiary screw conveyor 16 are all fully sealed structures, effectively preventing the escape of volatile organic compounds and meeting both environmental protection and safety requirements.

[0033] Specifically, the first-stage screw conveyor 8, the second-stage screw conveyor 12, and the third-stage screw conveyor 16 are equipped with feed inlets at the top, which are connected to the solid phase outlets of the first-stage filter 7, the second-stage filter 11, and the third-stage filter 15 via the seventh pipeline 59, the eleventh pipeline 63, and the fifteenth pipeline 67, respectively; and the bottom is equipped with discharge outlets, which are connected to the inlets of the second-stage washing tank 9, the third-stage washing tank 13, and the dryer 17 via the eighth pipeline 60, the twelfth pipeline 64, and the sixteenth pipeline 68, respectively.

[0034] In a preferred embodiment, the water washing and filtration system further includes a primary liquid phase collection tank 22, a secondary liquid phase collection tank 20, and a tertiary liquid phase collection tank 18; the liquid phase inlets of the primary liquid phase collection tank 22, the secondary liquid phase collection tank 20, and the tertiary liquid phase collection tank 18 are respectively connected to the liquid phase outlets of the primary filter 7, the secondary filter 11, and the tertiary filter 15, and the gas phase outlets of the primary liquid phase collection tank 22, the secondary liquid phase collection tank 20, and the tertiary liquid phase collection tank 18 are all connected to the low-pressure vent bus 77; the material outlet of the tertiary liquid phase collection tank 18 is connected to the material inlet of the secondary water washing vessel 9, the material outlet of the secondary liquid phase collection tank 20 is connected to the material inlet of the primary water washing vessel 5, and the material outlet of the primary liquid phase collection tank 22 is connected to the methanol separation system.

[0035] Specifically, the primary liquid phase collection tank 22, the secondary liquid phase collection tank 20, and the tertiary liquid phase collection tank 18 all adopt a vertical cylindrical structure. The top is equipped with a liquid phase inlet, which is connected to the liquid phase outlet of the primary filter 7, the secondary filter 11, and the tertiary filter 15 through the 62nd pipeline 117, the 59th pipeline 114, and the 56th pipeline 111, respectively. The top is equipped with a gas phase outlet, which is connected to the low-pressure vent bus 77 through the 22nd pipeline 75, the 20th pipeline 73, and the 18th pipeline 71, respectively. The bottom is equipped with a liquid phase outlet, which is connected to the inlet of the primary wash water booster pump 23, the secondary wash water booster pump 21, and the tertiary wash water booster pump 19 through the 63rd pipeline 118, the 60th pipeline 115, and the 57th pipeline 112, respectively. The dryer 17 is equipped with a material inlet that is connected to the material outlet of the three-stage screw conveyor 16 via the sixteenth pipeline 68; a dryer gas phase outlet 70 is connected to the low-pressure vent bus 77; and a powder product (EVOH) outlet is provided that is sent to the outside via the seventeenth pipeline 69.

[0036] (II) By-product separation module This module mainly includes a low-pressure separation system and a high-pressure separation system. The stripping gas mainly consists of methanol and methyl acetate. This invention uses a combination of low-pressure and high-pressure separation systems to separate methanol and methyl acetate. Methanol is separated from the bottom of the low-pressure separation tower 39, and methyl acetate is separated from the bottom of the high-pressure separation tower 45. The liquid phase in the reflux tank 41 at the top of the low-pressure separation tower is the feed to the high-pressure separation tower 45, and the liquid phase in the reflux tank 47 at the top of the high-pressure separation tower is sent back to the condensate buffer tank 37.

[0037] Specifically, the low-pressure separation system includes a low-pressure separation tower 39, which is used to separate methanol from the stripping gas generated by the fiber membrane reactor 1 and the fiber membrane neutralizer 2. The separated methanol is sent to the outside from the outlet of the low-pressure separation tower 39, and the separated material is sent to the high-pressure separation tower 45 from the gas phase outlet of the low-pressure separation tower 39. In a preferred embodiment, the gas phase outlets of the fiber membrane neutralizer 2 and the fiber membrane reactor 1 are combined and then connected to the condensate buffer tank 37 via the stripper gas cooler 36. The outlet of the condensate buffer tank 37 is connected to the vent bus 88, and the outlet of the condensate buffer tank 37 is connected to the low-pressure separation tower 39. Specifically, the inlet of the stripper gas cooler 36 is connected to the gas phase outlets of the fiber membrane reactor 1 and the fiber membrane neutralizer 2 via the 30th pipeline 84 and the 31st pipeline 85, and the outlet of the stripper gas cooler 36 is connected to the inlet of the condensate buffer tank 37 via the 32nd pipeline 86. The condensate buffer tank 37 is provided with a top condensate inlet connected to the outlet of the stripper gas cooler 36 via the 32nd pipeline 86; a reflux inlet is connected to the outlet of the high-pressure separation tower top reflux pump 48 via the 47th pipeline 102; a gas phase outlet is connected to the vent bus 88 via the 33rd pipeline 87; and a bottom condensate outlet is provided connected to the inlet of the condensate booster pump 38 via the 34th pipeline 89. In a preferred embodiment, the low-pressure separation system includes a low-pressure separation tower 39 and a low-pressure separation tower top reflux tank 41. The gas phase outlet of the fiber membrane neutralizer 2 and the gas phase outlet of the fiber membrane reactor 1 are combined and then connected to the condensate buffer tank 37 via a stripper gas cooler 36. The outlet of the condensate buffer tank 37 is connected to the inlet of the low-pressure separation tower 39.

[0038] The top of the low-pressure separation tower 39 has an outlet, which is connected to the inlet of the low-pressure separation tower top cooler 40 via the thirty-sixth pipeline 91. A feed inlet is located on one side of the middle section of the low-pressure separation tower 39, which is connected to the outlet of the condensate booster pump 38 via the thirty-fifth pipeline 90. A reflux port is located on one side of the upper section of the low-pressure separation tower 39, which is connected to the outlet of the low-pressure separation tower top reflux pump 42 via the thirty-ninth pipeline 94. The outlet of the low-pressure separation tower top cooler 40 is connected to the feed inlet of the low-pressure separation tower top reflux tank 41 via the thirty-seventh pipeline 92.

[0039] The top of the low-pressure separation tower top reflux tank 41 is equipped with an air outlet, which is connected to the vent bus 88 via the 29th pipeline 83; the bottom of the low-pressure separation tower top reflux tank 41 is equipped with a liquid outlet, which is connected to the inlet of the low-pressure separation tower top reflux pump 42 via the 38th pipeline 93. The outlet of the low-pressure separation tower top reflux pump 42 is divided into two paths: one path returns to the upper reflux port of the low-pressure separation tower 39 via the 39th pipeline 94, and the other path sends to the feed port of the high-pressure separation tower 45 via the 40th pipeline 95.

[0040] The bottom of the low-pressure separation tower 39 is provided with a discharge port, which is connected to the inlet of the low-pressure separation tower bottom pump 44 through the forty-first pipeline 96. The separated methanol is sent to the outside for recovery through the forty-second pipeline 97 at the outlet of the low-pressure separation tower bottom pump 44. The bottom of the low-pressure separation tower 39 is also connected to a heat source through the low-pressure separation tower bottom reboiler 43.

[0041] In a preferred embodiment, the high-pressure separation system includes a high-pressure separation tower 45 and a high-pressure separation tower top reflux tank 47. The feed inlet of the high-pressure separation tower 45 is connected to the outlet of the low-pressure separation tower top reflux pump 42 via a 40th pipeline 95.

[0042] The high-pressure separation tower 45 has an outlet at its top, which is connected to the inlet of the high-pressure separation tower top cooler 46 via the forty-third pipeline 98. A reflux port is located on one side of the upper part of the high-pressure separation tower 45, which is connected to the outlet of the high-pressure separation tower top reflux pump 48 via the forty-sixth pipeline 101. The outlet of the high-pressure separation tower top cooler 46 is connected to the inlet of the high-pressure separation tower top reflux tank 47 via the forty-fourth pipeline 99.

[0043] The top of the high-pressure separation tower top reflux tank 47 is equipped with an air outlet, which is connected to the vent bus 88 via the 28th pipeline 82; the bottom of the high-pressure separation tower top reflux tank 47 is equipped with a liquid outlet, which is connected to the inlet of the high-pressure separation tower top reflux pump 48 via the 45th pipeline 100. The outlet of the high-pressure separation tower top reflux pump 48 is divided into two paths: one path refluxes to the upper reflux port of the high-pressure separation tower 45 via the 46th pipeline 101, and the other path refluxes to the condensate buffer tank 37 via the 47th pipeline 102.

[0044] The bottom of the high-pressure separation tower 45 is provided with a discharge port, which is connected to the inlet of the high-pressure separation tower bottom pump 50 through the forty-eighth pipeline 103. The separated methyl acetate is sent to the outside for recovery through the forty-ninth pipeline 104 at the outlet of the high-pressure separation tower bottom pump 50. The bottom of the high-pressure separation tower 45 is also connected to a heat source through the high-pressure separation tower bottom reboiler 49.

[0045] (III) Wastewater Recycling Module This module mainly includes a methanol separation system and a wastewater treatment system. The wastewater collected after treatment by the water washing and filtration system mainly consists of methanol, wastewater, and various salts. Methanol is recovered at the top of the methanol separation tower 24, and saline wastewater is separated at the bottom of the methanol separation tower 24. The saline wastewater is separated into most of the water and high-concentration brine by the wastewater recovery facility 30. Most of the recovered water is collected by the recovery water tank 31 and reused in the water washing and filtration system.

[0046] Specifically, the methanol separation system includes a methanol separation tower 24 and a methanol separation tower top reflux tank 26. The feed inlet of the methanol separation tower 24 is connected to the liquid phase outlet of the filter. Specifically, the feed inlet on one side of the middle section of the methanol separation tower 24 is connected to the outlet of the primary water wash booster pump 23 through the fiftieth pipeline 105.

[0047] The methanol separator 24 has an outlet at the top, which is connected to the inlet of the methanol separator top cooler 25 via pipeline 119 (sixty-fourth line). A reflux port is located on one side of the upper part of the methanol separator 24, which is connected to the outlet of the methanol separator top reflux pump 27 via pipeline 122 (sixty-seventh line). The outlet of the methanol separator top cooler 25 is connected to the inlet of the methanol separator top reflux tank 26 via pipeline 120 (sixty-fifth line).

[0048] The top of the methanol separator top reflux tank 26 is equipped with a vent outlet, which is connected to the vent bus 88 via the 27th pipeline 81. The bottom of the methanol separator top reflux tank 26 is equipped with a liquid outlet, which is connected to the inlet of the methanol separator top reflux pump 27 via the 66th pipeline 121. The outlet of the methanol separator top reflux pump 27 is divided into two paths: one path returns to the upper reflux port of the methanol separator 24 via the 67th pipeline 122, and the other path sends the recovered solvent methanol to the outside via the 68th pipeline 123.

[0049] The bottom of the methanol separation tower 24 is provided with a discharge port, which is connected to the inlet of the methanol separation tower bottom pump 29 through the fifty-first pipeline 106. The waste liquid formed after separation is discharged to downstream equipment through the fifty-second pipeline 107 at the outlet of the methanol separation tower bottom pump 29. The bottom of the methanol separation tower 24 is also connected to a heat source through the methanol separation tower reboiler 28.

[0050] The wastewater treatment system includes a wastewater recovery facility 30, a recovery water tank 31, and a circulating water pump 32. The wastewater inlet of the wastewater recovery facility 30 is connected to the outlet of the methanol separation tower 24, the recovery water outlet of the wastewater recovery facility 30 is connected to the inlet of the recovery water tank 31, and the solid outlet of the wastewater recovery facility 30 is connected to the outside. The gas phase outlet of the recovery water tank 31 is connected to the vent bus 88, the water supply port of the recovery water tank 31 is connected to the outside, and the outlet of the recovery water tank 31 is connected to the water washing tank through the circulating water pump 32.

[0051] Wastewater recovery facility 30 is equipped with a wastewater inlet, which is connected to the outlet of methanol separator bottom pump 29 via pipeline 52 107; a recovery water outlet, which is connected to the inlet of recovery water tank 31 via pipeline 53 108; and a solids outlet, which sends solids to the outside via pipeline 70 125. Recovery water tank 31 is equipped with an inlet, which is connected to the recovery water outlet of wastewater recovery facility 30 via pipeline 53 108; a gas phase outlet at the top is connected to the vent bus 88 via pipeline 26 80; a water replenishment inlet is connected to the outside via pipeline 69 124; and a water outlet at the bottom is connected to the inlet of circulating water pump 32 via pipeline 54 109. This wastewater recovery facility uses evaporation crystallization to recover high-purity distilled water and acetate crystals.

[0052] In a preferred embodiment, the gas phase outlet of the washing vessel and dryer 17 is connected to a low-pressure vent bus 77; the low-pressure vent bus 77 is connected to the gas phase inlet of the gas-liquid separator 33, the gas outlet of the gas-liquid separator 33 is connected to the vent bus 88 via a low-pressure vent air booster 34, and the liquid phase outlet of the gas-liquid separator 33 is connected to the condensate buffer tank 37 at the gas phase outlet of the fiber membrane neutralizer 2.

[0053] Specifically, the gas-liquid separator 33 is equipped with a gas phase inlet connected to the low-pressure vent bus 77, a gas outlet at the top connected to the inlet of the low-pressure vent air booster 34 via the 24th pipeline 78, and a liquid phase outlet at the bottom connected to the condensate recovery pump 35 via the 71st pipeline 126; the outlet of the condensate recovery pump 35 is connected to the 47th pipeline 102 via the 72nd pipeline 127; the inlet of the low-pressure vent air booster 34 is connected to the gas phase outlet of the gas-liquid separator 33 via the 24th pipeline 78, and the outlet is connected to the vent bus 88 via the 25th pipeline 79.

[0054] In a preferred embodiment, the stripping gas is preferably methanol steam; the alkali metal catalyst is NaOH or KOH methanol solution, preferably NaOH; the neutralizing agent is dilute acetic acid methanol solution; the jacket medium of fiber membrane reactor 1, fiber membrane neutralizer 2, and primary water washing tank 5, secondary water washing tank 9, and tertiary water washing tank 13 is circulating hot water; the heat medium of the reboiler of low-pressure separation tower 39, high-pressure separation tower 45, and methanol separation tower 24 is steam.

[0055] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0056] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A reaction and separation system for preparing ethylene-vinyl alcohol copolymers, characterized in that, include: The fiber membrane reactor (1) is filled with a fiber structure. The mixed raw material inlet of the fiber membrane reactor (1) is connected to the metal alkali catalyst feed line (51) and the EVA solution feed line (52). The gas inlet of the fiber membrane reactor (1) is connected to the first stripping gas feed line (128), and the reaction liquid outlet and gas phase outlet of the fiber membrane reactor (1) are connected to the downstream fiber membrane neutralizer (2). The fiber membrane neutralizer (2) is located downstream of the fiber membrane reactor (1) and is filled with fiber filaments. The material inlet of the fiber membrane neutralizer (2) is connected to the reaction liquid outlet and neutralizer feed line (130) of the fiber membrane reactor (1), and the gas inlet of the fiber membrane neutralizer (2) is connected to the second stripping gas feed line (129). The gas phase outlet of the fiber membrane neutralizer (2) and the gas phase outlet of the fiber membrane reactor (1) are simultaneously connected to the low-pressure separation tower (39), and the reaction liquid outlet of the fiber membrane neutralizer (2) is connected to the water washing and filtration system. The water washing and filtration system includes a water washing tank, a filter and a dryer (17) connected in sequence. The material inlet of the water washing tank is connected to the reaction liquid outlet of the fiber membrane neutralizer (2). After the reaction liquid is processed by the water washing tank, the filter and the dryer (17), it forms powder EVOH and is sent to the outside from the powder product outlet of the dryer (17). The low-pressure separation system includes a low-pressure separation tower (39) for separating methanol from the stripping gas generated by the fiber membrane reactor (1) and the fiber membrane neutralizer (2). The separated methanol is sent to the outside from the outlet of the low-pressure separation tower (39), and the separated material is sent to the high-pressure separation tower (45) from the gas phase outlet of the low-pressure separation tower (39). The high-pressure separation system includes a high-pressure separation tower (45) for separating methyl acetate from the material after it has been processed by a low-pressure separation tower (39). The separated methyl acetate is sent to the outside from the outlet of the high-pressure separation tower (45).

2. The reaction and separation system for preparing ethylene-vinyl alcohol copolymers according to claim 1, characterized in that, The fiber membrane reactor (1) includes an upper shell, a middle shell and a lower shell. The top of the upper shell of the fiber membrane reactor (1) is provided with a gas phase outlet and the bottom side of the upper shell is provided with a mixed raw material inlet. The fiber membrane reactor (1) has a bundled fiber membrane cylinder inside the shell, which is filled with stainless steel fiber structure. Connecting cylinder plates are set at both ends. The bundled fiber membrane cylinder is fixed to the upper cylinder plate and the lower cylinder plate through the connecting flanges between the upper shell and the middle shell and between the middle shell and the lower shell. The fiber membrane reactor (1) has a gas inlet on the upper side of the lower shell, which is connected to the first stripping gas feed line (128), and a reaction liquid outlet at the bottom. The fiber membrane neutralizer (2) includes an upper shell, a middle shell and a lower shell. The top of the upper shell of the fiber membrane neutralizer (2) is provided with a gas phase outlet and the bottom side of the upper shell is provided with a material inlet. The fiber membrane neutralizer (2) has a bundled fiber membrane cylinder inside the shell, which is filled with stainless steel fiber structure. Connecting cylinder plates are provided at both ends. The bundled fiber membrane cylinder is fixed to the upper cylinder plate and the lower cylinder plate through the connecting flanges between the upper shell and the middle shell and between the middle shell and the lower shell. The fiber membrane neutralizer (2) has a gas inlet on the upper side of the lower shell, which is connected to the second stripping gas feed line (129), and a reaction liquid outlet at the bottom.

3. The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymer according to claim 1, characterized in that, The water washing filtration system is a multi-stage water washing filtration system, including a primary water washing filtration system, a secondary water washing filtration system, and a tertiary water washing filtration system; The primary water washing and filtration system includes a primary water washing tank (5) and a primary filter (7). The material inlet of the primary water washing tank (5) is connected to the reaction liquid outlet of the fiber membrane neutralizer (2), and the material inlet of the primary filter (7) is connected to the material outlet of the primary water washing tank (5). The secondary water washing and filtration system includes a secondary water washing tank (9) and a secondary filter (11). The material inlet of the secondary water washing tank (9) is connected to the solid phase outlet of the primary filter (7), and the material inlet of the secondary filter (11) is connected to the material outlet of the secondary water washing tank (9). The three-stage water washing and filtration system includes a three-stage water washing tank (13) and a three-stage filter (15). The material inlet of the three-stage water washing tank (13) is connected to the solid phase outlet of the two-stage filter (11), the material inlet of the three-stage filter (15) is connected to the material outlet of the three-stage water washing tank (13), and the solid phase outlet of the three-stage filter (15) is connected to the material inlet of the dryer (17). The gas phase outlets of the primary water washing tank (5), the secondary water washing tank (9), the tertiary water washing tank (13), and the dryer (17) are all connected to the low-pressure vent bus (77).

4. The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymer according to claim 3, characterized in that, It also includes a primary screw conveyor (8), a secondary screw conveyor (12) and a tertiary screw conveyor (16); The feed inlet of the first-stage screw conveyor (8) is connected to the solid phase outlet of the first-stage filter (7), and the discharge outlet of the first-stage screw conveyor (8) is connected to the material inlet of the second-stage washing tank (9). The feed inlet of the secondary screw conveyor (12) is connected to the solid phase outlet of the secondary filter (11), and the discharge outlet of the secondary screw conveyor (12) is connected to the material inlet of the tertiary washing tank (13). The feed inlet of the three-stage screw conveyor (16) is connected to the solid phase outlet of the three-stage filter (15), and the discharge outlet of the three-stage screw conveyor (16) is connected to the material inlet of the dryer (17).

5. The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymer according to claim 3, characterized in that, It also includes a primary liquid phase collection tank (22), a secondary liquid phase collection tank (20), and a tertiary liquid phase collection tank (18). The liquid phase inlets of the primary liquid phase collection tank (22), the secondary liquid phase collection tank (20), and the tertiary liquid phase collection tank (18) are respectively connected to the liquid phase outlets of the primary filter (7), the secondary filter (11), and the tertiary filter (15). The gas phase outlets of the primary liquid phase collection tank (22), the secondary liquid phase collection tank (20), and the tertiary liquid phase collection tank (18) are all connected to the low-pressure vent bus (77). The material outlet of the tertiary liquid phase collection tank (18) is connected to the material inlet of the secondary water washing tank (9), the material outlet of the secondary liquid phase collection tank (20) is connected to the material inlet of the primary water washing tank (5), and the material outlet of the primary liquid phase collection tank (22) is connected to the methanol separation system.

6. The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymer according to claim 1, characterized in that, It also includes a condensate buffer tank (37); The gas phase outlet of the fiber membrane neutralizer (2) and the gas phase outlet of the fiber membrane reactor (1) are combined and then connected to the condensate buffer tank (37) through the stripping gas cooler (36). The gas outlet of the condensate buffer tank (37) is connected to the vent bus (88), and the discharge outlet of the condensate buffer tank (37) is connected to the low-pressure separation tower (39). The low-pressure separation system also includes a low-pressure separation tower top reflux tank (41), the feed inlet of the low-pressure separation tower (39) is connected to the discharge outlet of the condensate buffer tank (37), the gas outlet of the low-pressure separation tower (39) is connected to the feed inlet of the low-pressure separation tower top reflux tank (41) through the low-pressure separation tower top cooler (40), and the discharge outlet of the low-pressure separation tower (39) is connected to the outside. The liquid outlet of the reflux tank (41) at the top of the low-pressure separation tower is divided into two paths. One path is connected to the reflux port of the low-pressure separation tower (39), and the other path is connected to the feed port of the high-pressure separation tower (45). The gas outlet of the reflux tank (41) at the top of the low-pressure separation tower is connected to the vent bus (88). The reaction gas formed after separation by the low-pressure separation tower (39) passes through the top cooler (40) of the low-pressure separation tower and enters the top reflux tank (41) of the low-pressure separation tower (39) from the gas outlet. The separated solvent methanol is sent to the outside through the outlet of the low-pressure separation tower (39). The low-pressure separation tower top reflux tank (41) is used to buffer and collect the reaction liquid after it has been cooled by the low-pressure separation tower top cooler (40). The reaction liquid is divided into two paths: one path flows back to the low-pressure separation tower (39) through the reflux port, and the other path is sent to the high-pressure separation tower (45). The outlet of the low-pressure separation tower top reflux tank (41) is connected to the vent bus (88).

7. The reaction and separation system for preparing ethylene-vinyl alcohol copolymers according to claim 6, characterized in that, The high-pressure separation system also includes a high-pressure separation tower top reflux tank (47). The feed inlet of the high-pressure separation tower (45) is connected to the discharge outlet of the low-pressure separation tower (39). The gas outlet of the high-pressure separation tower (45) is connected to the feed inlet of the high-pressure separation tower top reflux tank (47) through the high-pressure separation tower top cooler (46). The discharge outlet of the high-pressure separation tower (45) is connected to the outside. The outlet of the high pressure separation tower top reflux tank (47) is divided into two paths, one path is connected to the reflux port of the high pressure separation tower (45), and the other path is connected to the reflux liquid inlet of the condensate buffer tank (37). The outlet of the high pressure separation tower top reflux tank (47) is connected to the vent bus (88). The reaction gas formed after separation by the high-pressure separation tower (45) passes through the high-pressure separation tower top cooler (46) and then enters the high-pressure separation tower top reflux tank (47) from the gas outlet of the high-pressure separation tower (45). The separated solvent methyl acetate is sent to the outside through the discharge port of the high-pressure separation tower (45). The high-pressure separation tower top reflux tank (47) is used to buffer and collect the solvent methanol cooled by the high-pressure separation tower top cooler (46). The reaction liquid is divided into two paths: one path flows back to the high-pressure separation tower (45) through the reflux port, and the other path flows back to the condensate buffer tank (37). The gas outlet of the high-pressure separation tower top reflux tank (47) is connected to the vent bus (88).

8. The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymer according to claim 1, characterized in that, It also includes a methanol separation system, including a methanol separator (24) and a methanol separator top reflux tank (26). The feed inlet of the methanol separator (24) is connected to the liquid phase outlet of the filter, the gas outlet of the methanol separator (24) is connected to the feed inlet of the methanol separator top reflux tank (26) through the methanol separator top cooler (25), and the discharge outlet of the methanol separator (24) is connected to downstream equipment. The liquid outlet of the methanol separator top reflux tank (26) is divided into two paths, one path is connected to the reflux port of the methanol separator (24), and the other path is connected to the outside. The gas outlet of the methanol separator top reflux tank (26) is connected to the vent bus (88). The methanol separation tower (24) is used to separate methanol from the liquid discharged by the filter. The separated gaseous methanol passes through the methanol separation tower top cooler (25) and then enters the methanol separation tower top reflux tank (26) from the gas outlet of the methanol separation tower (24). The waste liquid formed after separation is discharged to downstream equipment through the discharge outlet of the methanol separation tower (24). The methanol separation tower top reflux tank (26) is used to buffer and collect the solvent methanol cooled by the methanol separation tower top cooler (25). The solvent methanol is divided into two paths: one path flows back to the methanol separation tower (24) through the reflux port, and the other path is sent to the outside. The gas outlet of the methanol separation tower top reflux tank (26) is connected to the vent bus (88).

9. The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymer according to claim 8, characterized in that, It also includes a wastewater treatment system, which includes a wastewater recycling facility (30), a recycling tank (31), and a circulating water pump (32). The wastewater inlet of the wastewater recovery facility (30) is connected to the outlet of the methanol separation tower (24), the recovered water outlet of the wastewater recovery facility (30) is connected to the inlet of the recovered water tank (31), and the solid outlet of the wastewater recovery facility (30) is connected to the outside of the boundary. The gas phase outlet of the recovery water tank (31) is connected to the vent bus (88), the water inlet of the recovery water tank (31) is connected to the outside of the boundary, and the water outlet of the recovery water tank (31) is connected to the water washing tank through the circulating water pump (32).

10. The reaction and separation combination system for preparing ethylene-vinyl alcohol copolymer according to claim 1, characterized in that, The gas phase outlet of the washing vessel and the dryer (17) is connected to the low-pressure vent bus (77). The low-pressure vent bus (77) is connected to the gas phase inlet of the gas-liquid separator (33), the gas outlet of the gas-liquid separator (33) is connected to the vent bus (88) through the low-pressure vent air booster (34), and the liquid phase outlet of the gas-liquid separator (33) is connected to the condensate buffer tank (37) at the gas phase outlet of the fiber membrane neutralizer (2).

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