NMP (N-Methyl Pyrrolidone) recovery equipment

Abstract

The utility model discloses NMP (N-Methyl Pyrrolidone) recovery equipment which comprises a preheater, a condensate water heater, a scraper falling film evaporator, a tower top full cooler, a tower top vacuum trap, a product cooler, a raw material deaerator, a tower bottom heat pump, an evaporator feeding pump, a light component discharging pump, a dividing wall rectifying tower and a light component temporary storage tank, the dividing wall rectifying tower comprises a tower body, the bottom in the tower body is provided with a first space and a second space which are separated by a partition plate, a first packing layer is arranged above the first space, a second packing layer is arranged above the second space, a discharging cavity is formed in the middle area of the second packing layer, and a third packing layer is arranged on the upper portion in the tower body. A built-in condensation reflux device is arranged above the third filler layer; an outlet of a heating channel of the preheater is connected with an inlet of the raw material deaerator; the condensate water heater is connected with the outlet of the raw material deaerator and the lower part of the first space of the dividing wall rectifying tower. The NMP recovery equipment is low in investment cost, low in process energy consumption and capable of stably running for a long time.

Description

Technical Field

[0001] The utility model relates to the technical field of NMP purification, in particular to an NMP recovery device. Background Art

[0002] Methylpyrrolidone (NMP for short) is an important chemical solvent with the characteristics of low toxicity, high boiling point, strong solubility, good selectivity and good stability. It is the most commonly used solvent in lithium battery production. NMP is miscible with water, PVDF, positive and negative electrode materials and other substances, so it is widely used in the preparation of lithium batteries. At present, there are many main methods for recovering NMP in the lithium battery industry. The most widely used method is to continuously distill the mixed liquid containing NMP through multiple towers, which can effectively remove impurities such as water.

[0003] Due to the high energy consumption of multi-tower distillation, many studies have been conducted on the use of a bulkhead tower to purify NMP. The Chinese utility model patent application with publication number CN114432728A discloses a bulkhead tower, in which a partition plate is vertically arranged from the upper end cap, and two spaces at the lower part share a reboiler, which can obtain qualified high-purity NMP products, but the system has a high temperature in the tower bottom, and the decomposition rate of NMP is relatively fast. Since the coating machine exhaust gas carries a very small amount of soluble lithium salts and insoluble particles, long operation time will cause the reboiler to be blocked and the filler to be contaminated. The Chinese utility model patent with announcement number CN220370452U discloses a bulkhead tower applied to the recovery of NMP waste liquid, in which a partition plate is arranged at the bottom of the tower, and the system arranges fillers on both sides of the partition plate, while no fillers are arranged at the top of the tower, and the material is also fed directly between the filler layers. Since the coating machine exhaust gas carries a very small amount of soluble lithium salts and insoluble particles, long operation time will cause filler contamination and blockage. In addition, the system only uses two reboilers and one condenser, without considering the issue of energy recovery. Utility Model Content

[0004] The technical problem solved by the utility model is to provide an energy-saving NMP recovery device capable of operating stably for a long time.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is: an NMP recovery device, including a preheater, a condensate heater, a scraper falling film evaporator, a tower top full cooler, a tower top vacuum collector, a product cooler, a raw material deoxidizer, a tower bottom heat pump, an evaporator feed pump, a light component discharge pump, a distillation tower and a light component temporary storage tank;

[0006] The dividing wall distillation tower comprises a tower body, wherein the bottom of the tower body has a first space and a second space separated by a partition plate, a first packing layer is arranged above the first space, a second packing layer is arranged above the second space, a discharge cavity is arranged in the middle area of ​​the second packing layer, a third packing layer is arranged at the upper part of the tower body, and a built-in condensation reflux device is arranged above the third packing layer;

[0007] The outlet of the cold stream of the preheater is connected to the inlet of the raw material deoxidizer;

[0008] The condensed water heater is connected to the outlet of the raw material deoxidizer and the lower part of the first space of the next-wall distillation tower;

[0009] The inlet of the scraped falling film evaporator is connected to the bottom of the first space of the distillation tower next door through the evaporator feed pump, the gas outlet of the scraped falling film evaporator is connected to the upper part of the first space, one of the liquid outlets of the scraped falling film evaporator is connected to the discharge port, and the other liquid outlet of the scraped falling film evaporator is connected to the lower part of the first space;

[0010] The inlet of the heat pump for recovering the heat energy of the fluid at the bottom of the tower is connected to the discharge cavity, the outlet of the heat pump for recovering the heat energy of the fluid at the bottom of the tower is connected to the hot fluid inlet of the preheater, and the inlet of the heating channel of the heat pump at the bottom of the tower and the outlet of the heating channel of the heat pump at the bottom of the tower are respectively connected to the second space;

[0011] The hot fluid inlet of the product cooler is connected to the hot fluid outlet of the preheater;

[0012] The tower top full cooler is respectively connected to the top of the tower body and the light component temporary storage tank;

[0013] The lower part of the light component temporary storage tank is connected to the light component discharge pump, and the upper part of the light component temporary storage tank is connected to the tower top vacuum collector.

[0014] In one embodiment, the ratio of the cross-sectional area of ​​the first space to the cross-sectional area of ​​the second space is 1.1 to 2.

[0015] In one embodiment, the number of theoretical plates in the first packing layer is 5 to 20.

[0016] In one embodiment, the number of theoretical plates in the second packing layer is 5 to 15.

[0017] In one embodiment, the number of theoretical plates in the third packing layer is 5 to 25.

[0018] In one embodiment, the pressure range of the top of the dividing wall distillation tower is 5-10 kPa, the pressure difference between the first space and the top is 1-3 kPa, and the pressure difference between the second space and the top is 1.2-3.2 kPa.

[0019] In one embodiment, the top temperature of the distillation tower is 35°C to 46°C.

[0020] In one embodiment, the temperature of the first space is 110-125°C.

[0021] In one embodiment, the temperature of the second space is 115-130°C.

[0022] The beneficial effects of the utility model are: the NMP recovery equipment has a novel structure, and compared with multi-tower distillation equipment, the equipment investment cost is lower and the production energy consumption is low. The bulkhead tower technology with a heat pump is adopted, and the deoxygenation, desalination, deheavy component removal, dehydration, and refining processes before the raw materials enter the tower are integrated and completed in one tower.

[0023] The raw material deoxygenator can deoxygenate the raw materials and reduce the occurrence of side reactions. Deoxygenation can reduce the reaction of dissolved oxygen and NMP to generate heavy components, which is beneficial to improve the recovery rate of NMP. Moreover, less heavy component content means easier separation, which reduces the number of theoretical plates of the packing layer in the distillation tower next door, thereby reducing equipment costs and energy consumption.

[0024] The first space uses a scraper falling film evaporator to replace the ordinary reboiler. In addition to realizing the function of the ordinary reboiler to evaporate the feed liquid, it can also concentrate the heavy components and trace soluble lithium salts and insoluble particulate matter in the raw materials to form a semi-solid residue discharge device without the need for subsequent concentration treatment; the second space uses a heat pump to replace the reboiler for heating, which can recover the heat energy of the product and reduce energy consumption; the top of the tower adopts a built-in condensation reflux device, which saves equipment such as an external reflux pump compared to the external condenser reflux, and the pressure drop at the top of the tower is lower, which is conducive to the control of the top temperature of the distillation tower next door.

[0025] In addition, the raw materials directly enter the tower kettle, and there is no stripping section in the distillation tower next door, which can prevent the trace soluble lithium salts in the raw materials from contaminating and clogging the packing. A normally operating vacuum system only discharges water vapor, which generally does not require special treatment to meet emission standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0027] Figure 1 The simplified structural diagram of the NMP recovery device of the first embodiment of the utility model is shown in FIG.

[0028] Description of Figure Numbers:

[0029] 1. Preheater; 2. Condensate heater; 3. Scraper falling film evaporator; 4. Tower top full cooler; 5. Tower top vacuum collector; 6. Product cooler; 7. Raw material deoxidizer; 8. Tower bottom heat pump; 9. Evaporator feed pump; 10. Light component discharge pump; 11. Divider tower; 12. Light component temporary storage tank; 13. First packing layer; 14. Second packing layer; 15. Third packing layer; 16. Built-in condensation reflux device; 17. Inert gas inlet; 18. Discharge chamber; 19. First space; 20. Second space;

[0030] S1, the first pipeline; S2, the second pipeline; S3, the third pipeline; S4, the fourth pipeline; S5, the fifth pipeline; S6, the sixth pipeline; S7, the seventh pipeline; S8, the eighth pipeline; S9, the ninth pipeline; S10, the tenth pipeline; S11, the eleventh pipeline; S12, the twelfth pipeline; S13, the thirteenth pipeline; S14, the fourteenth pipeline; S15, the fifteenth pipeline; S16, the sixteenth pipeline; S17, the seventeenth pipeline; S18, the eighteenth pipeline; S19, the nineteenth pipeline; S20, the twentieth pipeline; S21, the twenty-first pipeline; S22, the twenty-second pipeline. DETAILED DESCRIPTION

[0031] The purpose, features and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

[0032] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0033] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, back, etc., then the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0034] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0035] In addition, if the meaning of "and / or" appears in the full text is to include three parallel solutions, taking "and / or" as an example, it includes solutions, or solutions, or solutions that are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this utility model.

[0036] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0037] Embodiment 1

[0038] Embodiment 1 of the present utility model is: an NMP recovery device, which is used to recover and purify NMP waste liquid collected by a lithium battery coating machine.

[0039] Please refer to Figure 1 The NMP recovery equipment includes a preheater 1, a condensate heater 2, a scraper falling film evaporator 3, a tower top full cooler 4, a tower top vacuum collector 5, a product cooler 6, a raw material deoxidizer 7, a tower bottom heat pump 8, an evaporator feed pump 9, a light component discharge pump 10, a distillation tower 11 and a light component temporary storage tank 12;

[0040] The dividing wall distillation tower 11 comprises a tower body, the bottom of the tower body has a first space 19 and a second space 20 separated by a partition plate, the partition plate is vertically arranged along the height direction of the tower body, a first packing layer 13 is arranged above the first space 19, a second packing layer 14 is arranged above the second space 20, a discharge cavity 18 is arranged in the middle area of ​​the second packing layer 14, a third packing layer 15 is arranged in the upper part of the tower body, and a built-in condensation reflux device 16 is arranged above the third packing layer 15;

[0041] The inlet of the heating channel of the preheater 1 is connected to a first pipe S1, and the external raw material (i.e., NMP waste liquid) is passed into the heating channel of the preheater 1 via the first pipe S1. The outlet of the heating channel of the preheater 1 is connected to the inlet of the raw material deoxidizer 7 through a second pipe S2. The raw material deoxidizer 7 can deoxidize the NMP waste liquid by various deoxidation means such as thermal deoxidation, vacuum deoxidation, and analytical deoxidation. The specific structure of the raw material deoxidizer 7 can refer to the Chinese patent application with application number 202311717748.9;

[0042] The outlet of the raw material deoxidizer 7 is connected to the inlet of the heating channel of the condensed water heater 2 through the third pipe S3, and the outlet of the heating channel of the condensed water heater 2 is connected to the lower part of the first space 19 through the fourth pipe S4;

[0043] The bottom of the first space 19 is connected to the evaporator feed pump 9 through the fifth pipeline S5, and the evaporator feed pump 9 is connected to the inlet of the scraped film evaporator 3 through the sixth pipeline S6. The gas outlet of the scraped film evaporator 3 is connected to the upper part of the first space 19 through the seventh pipeline S7. One of the liquid outlets of the scraped film evaporator 3 forms a discharge port through the ninth pipeline S9, and the other liquid outlet of the scraped film evaporator 3 is connected to the lower part of the first space 19 through the eighth pipeline S8. The maximum liquid-phase solid content of the scraped film evaporator 3 in this embodiment can reach 15%, while other forms of reboilers such as kettle type in the prior art may be blocked when treating residual residues in the tower kettle. In addition, the scraped film evaporator 3 has high heat transfer efficiency, and the total heat transfer coefficient is 1750~7000W / (m 2 .℃), the residence time of the material in the scraper falling film evaporator 3 is short, and the probability of side reactions is low. If a general reboiler, such as a thermosyphon reboiler or a kettle reboiler, is used, the discharged liquid needs to be further distilled. If a general reboiler is used to concentrate the liquid, the concentrated residue may clog the heat exchanger, requiring frequent maintenance and cleaning;

[0044] The inlet of the heat energy recovery channel of the tower bottom heat pump 8 is connected to the discharge chamber 18 through the tenth pipeline S10, the outlet of the heat energy recovery channel of the tower bottom heat pump 8 is connected to the inlet of the hot fluid cooling channel of the preheater 1 through the eleventh pipeline S11, the inlet of the heating channel of the tower bottom heat pump 8 is connected to the second space 20 through the fourteenth pipeline S14, and the outlet of the heating channel of the tower bottom heat pump 8 is connected to the second space 20 through the fifteenth pipeline S15. The connection point between the fourteenth pipeline S14 and the tower body is located at the connection point between the fifteenth pipeline S15 and the tower body. In detail, the fourteenth pipeline S14 is connected to the tower body. The liquid phase region of the second space 20 is connected to the fifteenth pipeline S15, and the gas phase region of the second space 20 is connected; the NMP product is discharged from the discharge cavity 18 between the two sections of fillers in the second space 20 in the gas phase, so that the NMP product will not be contaminated by the heavy components at the bottom of the tower, and the moisture content is also below 100ppm. The heat of the side product is recovered by the bottom heat pump 8. The vaporization heat of the NMP product recovered in this section plus a small amount of electric energy for the operation of the bottom heat pump 8 can be fully converted into heat energy for heating the material in the second space 20. In normal operation, except for a small amount of electric energy required by the bottom heat pump 8, no additional energy is required, thereby reducing energy consumption as a whole.

[0045] The inlet of the cooling channel of the product cooler 6 is connected to the outlet of the cooling channel of the preheater 1 through the twelfth pipeline S12, and the outlet of the cooling channel of the product cooler 6 is connected to the outside through the thirteenth pipeline S13 to complete the recovery and transportation of the NMP product;

[0046] The bottom of the second space 20 is connected to the middle of the first space 19 through a sixteenth pipe S16;

[0047] The inlet of the cooling channel of the tower top full cooler 4 is connected to the top of the tower body through the seventeenth pipeline S17, and the outlet of the cooling channel of the tower top full cooler 4 is connected to the light component temporary storage tank 12 through the eighteenth pipeline S18;

[0048] The upper part of the light component temporary storage tank 12 is connected to the inlet of the tower top vacuum collector 5 through the nineteenth pipeline S19, and the outlet of the vacuum collector is connected to the vacuum system and the outside world through the twentieth pipeline S20. The lower part of the light component temporary storage tank 12 is connected to the light component discharge pump 10 through the twenty-first pipeline S21, and the light component discharge pump 10 is connected to the outside world through the twenty-second pipeline S22 to discharge light components mainly composed of water.

[0049] In the actual NMP recovery equipment, the inlet of the heat medium channel of the condensed water heater 2 can be connected to the condensed water outlet of the scraper falling film evaporator 3, so that the heat can be fully utilized and the heat waste can be reduced, thereby improving the energy-saving performance of the NMP recovery equipment to a greater extent.

[0050] An inert gas inlet 17 is provided at the top of the tower body, and an inert gas is introduced into the distillation tower 11 through the inert gas inlet 17. The inert gas can prevent the oxidation and decomposition of NMP, which is beneficial to improving the recovery efficiency of NMP. The inert gas can be nitrogen, argon, helium, etc.

[0051] The cross-sectional area of ​​the first space 19 is greater than the cross-sectional area of ​​the second space 20 , and the ratio of the cross-sectional area of ​​the first space 19 to the cross-sectional area of ​​the second space 20 is 1.1 to 2.

[0052] The number of theoretical plates in the first packing layer 13 is 5 to 20, and the specific number of theoretical plates in the first packing layer 13 depends on the content of heavy components in the raw material; the number of theoretical plates in the second packing layer 14 is 5 to 15, and the specific number of theoretical plates in the second packing layer 14 depends on the quality requirements of the product, such as the purity, heavy component content and water content of the NMP product; the number of theoretical plates in the third packing layer 15 is 5 to 25, and the specific number of theoretical plates in the third packing layer 15 depends on the content of light components in the raw material, such as the water content.

[0053] The reflux liquid leaving the third packing layer 15 falls to the first packing layer 13 of the first space 19 and the second packing layer 14 of the second space 20, wherein the amount of the reflux liquid to the first packing layer 13 of the first space 19 accounts for 0.3-0.8 of the total amount of the reflux liquid.

[0054] The reflux ratio of the isolation distillation tower is generally controlled at 1 to 8.

[0055] The pressure range of the top of the dividing wall distillation tower 11 is 5-10 kPa, the pressure difference between the first space 19 and the top is 1-3 kPa, and the pressure difference between the second space 20 and the top is 1.2-3.2 kPa.

[0056] The top temperature of the distillation tower 11 is 35°C to 46°C, the temperature of the first space 19 is 110°C to 125°C, and the temperature of the second space 20 is 115°C to 130°C.

[0057] The process flow of this NMP recovery equipment is briefly described as follows:

[0058] A stream containing 80% NMP aqueous solution (in the lithium battery coating machine process, 80% to 90% NMP aqueous solution is more common, but the NMP recovery equipment of the present invention does not limit the specific water content of the NMP aqueous solution. NMP aqueous solution with any water content can be recovered and purified by the NMP recovery equipment of the present invention) enters the preheater 1 through the first pipeline S1, and the temperature is increased to 60°C. Then the stream leaving the preheater 1 enters the raw material deoxygenator 7 through the second pipeline S2 for deoxygenation. The function of the raw material deoxygenator 7 is to reduce the decomposition of NMP in the subsequent distillation process, reduce the generation of heavy components, and improve the recovery rate of NMP. The deoxygenated raw material enters the condensate heater 2 through the third pipeline S3, and the temperature rises to 90°C. The material heated by the condensate heater 2 enters the first space 19 at the bottom of the next-door distillation tower 11 through the fourth pipeline S4. The stream drawn out of the first space 19 passes through the fifth pipeline S5 and enters the evaporator feed pump 9 and enters the scraper falling film evaporator 3 through the sixth pipeline S6. The gas generated by evaporation in the scraper falling film evaporator 3 returns to the gas phase area of ​​the first space 19 through the seventh pipeline S7, and exchanges heat and substances with the liquid in the first packing layer 13 to complete the distillation process. The ungasified liquid material in the scraper falling film evaporator 3 is discharged from the bottom of the scraper falling film evaporator 3. According to the test results, if the discharge requirements of the residue are met, it is directly cooled and barreled through the ninth pipeline S9 for external discharge. If the discharge requirements have not been met, it returns to the liquid phase area of ​​the first space 19 through the eighth pipeline S8 to continue the above process until the discharge requirements of the residue are met.

[0059] The NMP gas phase product is drawn out from the middle section of the second packing layer 14 of the second space 20 (i.e., the discharge chamber 18) through the tenth pipeline S10 and enters the tower bottom heat pump 8. The gas phase NMP is condensed into liquid phase NMP in the tower bottom heat pump 8. The condensation heat is recovered by the tower bottom heat pump 8 and used to heat the material in the second space 20 in the adjacent distillation tower 11. The liquid phase material in the liquid phase region of the second space 20 enters the tower bottom heat pump 8 through the fourteenth pipeline S14 and becomes a gas phase material and returns to the gas phase region of the second space 20 through the fifteenth pipeline S15. The temperature of the liquid phase NMP cooled by the pump 8 is about 110°C. The liquid phase NMP leaving the tower bottom heat pump 8 is passed into the preheater 1 through the eleventh pipeline S11 to heat the NMP aqueous solution (i.e., raw material) flowing through the preheater 1, and the temperature of the liquid phase NMP itself decreases. At this time, the temperature of the liquid phase NMP is about 50°C. The liquid phase NMP leaving the preheater 1 is passed into the product cooler 6 through the twelfth pipeline S12, and is further cooled to 40°C in the product cooler 6, and then sent to the outside of the boundary area through the thirteenth pipeline S13 connected to the product cooler 6 to become the NMP product.

[0060] The top of the distillation tower 11 next door passes the uncondensed gas into the top full cooler 4 through the seventeenth pipeline S17, condenses into liquid phase through the top full cooler 4, and then flows into the light component temporary storage tank 12 through the eighteenth pipeline S18 for temporary storage, and finally is transported to the outside through the light component discharge pump 10.

[0061] The light component temporary storage tank 12 passes the non-condensable gas into the tower top vacuum collector 5 through the 19th pipeline S19, and is connected to the vacuum system for discharge. Since the light component at the top of the tower is water, the non-condensable gas usually does not contain NMP and organic components, and can be directly discharged under normal circumstances.

[0062] The main control schemes of the distillation tower 11 next door are: controlling the flow rate of heating steam by the liquid level of the liquid phase area of ​​the first space 19 of the distillation tower 11 next door; controlling the product extraction amount in cascade by the product discharge flow rate and the temperature of the liquid phase area of ​​the second space 20 of the distillation tower 11 next door; controlling the cooling amount of the tower top by the temperature of a certain point in the third packing layer 15 (sensitive plate temperature), thereby stabilizing the reflux in the tower; controlling the pressure at the tower top by the opening of the vacuum system regulating valve; controlling the liquid level of the second space 20 of the distillation tower next door by the opening of the regulating valve of the first space 19 of the distillation tower next door 11; and controlling the liquid level of the light component temporary storage tank 12 by the opening of the regulating valve of the temporary storage tank for light components to go out of the boundary.

[0063] Examples

[0064] The raw materials are 80% by mass of NMP, 19.8% of H2O, 0.02% of heavy matter, trace soluble lithium salt and insoluble particles.

[0065] The theoretical plates of the first packing layer are 10, the theoretical plates of the second packing layer are 8, and the theoretical plates of the third packing layer are 7. The amount of reflux liquid leaving the third packing layer of the distillation tower next door falling into the first space accounts for 0.5 of the total amount of reflux liquid, the reflux ratio of the distillation tower next door is 2.15, the pressure of the top of the distillation tower next door is 8kpa, the top temperature is controlled at 41.5℃, the pressure of the first space at the bottom of the distillation tower next door is 9.6kPa, and the pressure of the second space at the bottom of the distillation tower next door is 9.8kPa.

[0066] The mass fraction of the harvested NMP product is 99.93%, and the water content is 0.0015%.

[0067] This NMP recovery equipment requires 0.84 tons of steam and 45kw of heat pump electricity to produce 1 ton of NMP products, and the power consumption of other moving equipment and circulating water is 7.5kw. The traditional three-tower process requires 1.2 tons of steam to produce 1 ton of NMP products. In comparison, this NMP recovery equipment saves a lot of energy; and the scraper falling film evaporator is used to directly remove the residue, while the liquid discharged by the traditional process needs further distillation treatment. It can be seen that the actual energy consumption of this NMP recovery equipment is less.

[0068] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly used in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A NMP recovery device, characterized in that: Including preheater, condensate heater, scraper falling film evaporator, tower top full cooler, tower top vacuum collector, product cooler, raw material deoxidizer, tower bottom heat pump, evaporator feed pump, light component discharge pump, next-door distillation tower and light component temporary storage tank; The dividing wall distillation tower comprises a tower body, wherein the bottom of the tower body has a first space and a second space separated by a partition plate, a first packing layer is arranged above the first space, a second packing layer is arranged above the second space, a discharge cavity is arranged in the middle area of ​​the second packing layer, a third packing layer is arranged at the upper part of the tower body, and a built-in condensation reflux device is arranged above the third packing layer; The outlet of the cold stream of the preheater is connected to the inlet of the raw material deoxidizer; The condensed water heater is connected to the outlet of the raw material deoxidizer and the lower part of the first space of the next-wall distillation tower; The inlet of the scraped falling film evaporator is connected to the bottom of the first space of the distillation tower next door through the evaporator feed pump, the gas outlet of the scraped falling film evaporator is connected to the upper part of the first space, one of the liquid outlets of the scraped falling film evaporator is connected to the discharge port, and the other liquid outlet of the scraped falling film evaporator is connected to the lower part of the first space; The inlet of the heat pump for recovering the heat energy of the fluid at the bottom of the tower is connected to the discharge cavity, the outlet of the heat pump for recovering the heat energy of the fluid at the bottom of the tower is connected to the hot fluid inlet of the preheater, and the inlet of the heating channel of the heat pump at the bottom of the tower and the outlet of the heating channel of the heat pump at the bottom of the tower are respectively connected to the second space; The hot fluid inlet of the product cooler is connected to the hot fluid outlet of the preheater; The tower top full cooler is respectively connected to the top of the tower body and the light component temporary storage tank; The lower part of the light component temporary storage tank is connected to the light component discharge pump, and the upper part of the light component temporary storage tank is connected to the tower top vacuum collector.

2. NMP recovery equipment according to claim 1, characterized in that: The ratio of the cross-sectional area of ​​the first space to the cross-sectional area of ​​the second space is 1.1 to 2.

3. NMP recovery equipment according to claim 1, is characterized in that: The number of theoretical plates in the first packing layer is 5 to 20.

4. NMP recovery equipment according to claim 1, characterized in that: The number of theoretical plates in the second packing layer is 5 to 15.

5. NMP recovery equipment according to claim 1, characterized in that: The number of theoretical plates in the third packing layer is 5 to 25.

6. NMP recovery equipment according to claim 1, characterized in that: The pressure range of the top of the dividing wall distillation tower is 5-10 kPa, the pressure difference between the first space and the top is 1-3 kPa, and the pressure difference between the second space and the top is 1.2-3.2 kPa.

7. NMP recovery equipment according to claim 1, characterized in that: The top temperature of the distillation tower next door is 35°C to 46°C.

8. NMP recovery equipment according to claim 1, characterized in that: The temperature of the first space is 110-125°C.

9. NMP recovery equipment according to claim 1, characterized in that: The temperature of the second space is 115-130°C.

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