NMP recovery and purification system for coating area of lithium battery factory

Abstract

The utility model discloses an NMP (N-Methyl Pyrrolidone) recovery and purification system for a coating area of a lithium battery factory. The NMP recovery and purification system comprises a heat exchanger, an NMP recovery device, a direct expansion system, a supergravity purification device and a pervaporation device, the heat exchanger is used for recovering heat energy of the NMP waste gas; the NMP recovery device is connected with the heat exchanger and is used for liquefying and recovering NMP; the direct expansion system is respectively connected with the heat exchanger, the NMP recovery device and the supergravity purification device, and is used for pre-treating NMP waste gas and preheating NMP waste liquid; the supergravity purification device is connected with the NMP recovery device and is used for removing most moisture in the NMP waste liquid; the pervaporation device is connected with the supergravity purification device to further remove moisture in the NMP waste liquid so as to obtain an NMP purified liquid. The NMP recovery energy consumption of the lithium battery coating area can be effectively reduced, meanwhile, the structure is simple, and the occupied area is small; and the energy consumption of purification treatment is reduced while a qualified NMP purified product is obtained.

Description

Technical Field

[0001] The utility model relates to an NMP recovery and purification system in a coating area of ​​a lithium battery factory, belonging to the technical field of NMP recovery and purification of lithium ion batteries. Background Art

[0002] N-Methylpyrrolidone, or NMP, is a highly soluble solvent with stable chemical properties and good thermal stability. It is widely used in the chemical industry. In the field of lithium battery production, NMP is often used as a solvent for positive electrode materials. During the coating process, the NMP used is constantly volatilized. Usually, the volatilized NMP is extracted during the production process and recycled to form NMP waste liquid. The NMP waste liquid is then purified to remove moisture and heavy metal impurities in the waste liquid to obtain qualified NMP purified liquid.

[0003] At present, the mainstream NMP recovery technologies include waste heat recovery + absorption tower, waste heat recovery + deep condensation device + rotor, waste heat recovery + deep cooling device + absorption tower, and waste heat recovery + deep cooling device + absorption tower. Among them, compared with the first two processes, the waste heat recovery + deep cooling device + absorption tower process has the advantages of low return air dew point and no need for rotor consumables, and is widely used in lithium battery factories with high requirements for battery cell quality. However, this method requires a deep cooling device in front of the absorption tower, which consumes electricity and has a high overall energy consumption. The current mainstream NMP purification equipment uses a high-tower distillation solution, however, this solution occupies a large area and has a complex equipment structure. In summary, the development of a lithium battery factory NMP recovery and purification system that can effectively recover NMP gas in the coating area to form NMP waste liquid and efficiently purify NMP waste liquid is a problem that needs to be solved urgently at this stage. Summary of the invention

[0004] The purpose of the utility model is to overcome the deficiencies in the prior art and provide a NMP recovery and purification system for the coating area of ​​a lithium battery factory, which can realize the recovery and utilization of gas heat through a waste heat recovery system, realize the liquefaction and recovery of NMP components in the gas through the method of the NMP recovery device, and then use the supergravity purification device and the pervaporation device to realize the purification of NMP waste liquid. In addition, the utility model uses a direct expansion system to effectively reduce the energy consumption of NMP recovery and purification in the lithium battery coating area, and the structure is relatively simple, which can realize the efficient recovery and purification of NMP waste liquid.

[0005] In order to achieve the above purpose, the utility model is implemented by adopting the following technical solutions:

[0006] A NMP recovery and purification system for a coating area of ​​a lithium battery factory, comprising a heat exchanger, an NMP recovery device, a direct expansion system, an ultra-gravity purification device and a pervaporation device;

[0007] The heat exchanger is used to recover the heat energy of the NMP waste gas generated in the coating area;

[0008] The NMP recovery device is connected to a heat exchanger for liquefying and recovering NMP;

[0009] The direct expansion system is respectively connected to a heat exchanger, an NMP recovery device and an ultra-gravity purification device, and is used to pre-treat the NMP waste gas and preheat the NMP waste liquid;

[0010] The ultra-gravity purification device is connected to the NMP recovery device to remove most of the water in the NMP waste liquid;

[0011] The pervaporation device is connected to the supergravity purification device to further remove water from the NMP waste liquid to obtain NMP purified liquid.

[0012] Furthermore, the NMP recovery and purification system also includes a coater, which includes an oven for drying out the NMP in the electrode, and a coater head and a coater tail are respectively provided on both sides of the oven.

[0013] Furthermore, the oven is connected to an exhaust duct and an exhaust fan, and the exhaust duct is connected to a high-temperature inlet of a heat exchanger; the oven is also connected to an air supply duct and an air supply fan, and the air supply duct is connected to a high-temperature outlet of the heat exchanger.

[0014] Furthermore, the low-temperature outlet of the heat exchanger is connected in sequence to the evaporator of the direct expansion system, the cooler of the NMP recovery device, the NMP absorption tower and the NMP waste liquid storage tank.

[0015] Furthermore, the NMP recovery device comprises a cooler, an NMP absorption tower and an NMP waste liquid storage tank which are connected in sequence, the top outlet of the NMP absorption tower is connected to the low temperature inlet of the heat exchanger, and the outlet of the NMP waste liquid storage tank is connected to the condenser of the direct expansion system.

[0016] Furthermore, the direct expansion system includes an evaporator, a compressor, a condenser and an expansion valve. The outlet of the evaporator is connected to the compressor and the condenser in sequence, and the outlet of the condenser is connected to the expansion valve and the evaporator in sequence; the outlet of the condenser is also connected to an ultra-gravity purification device.

[0017] Furthermore, the ultra-gravity purification device includes an ultra-gravity purifier, a reboiler, a first reflux tank and a first vacuum tank. The top of the ultra-gravity purifier is circularly connected to the first reflux tank, and the bottom is circularly connected to the reboiler. The first reflux tank is connected to the first vacuum tank, and the NMP inlet of the ultra-gravity purifier is also connected to the condenser of the direct expansion system.

[0018] Furthermore, the pervaporation device includes a heater, a pervaporator, a second reflux tank, a second vacuum tank and an NMP purified liquid storage tank, the inlet of the heater is connected to the bottom of the reboiler of the ultragravity purification equipment, and the outlet is connected to the pervaporator, the outlet of the pervaporator is respectively connected to the second reflux tank and the NMP purified liquid storage tank, and the second reflux tank is also connected to the second vacuum tank.

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] The NMP recovery and purification system in the coating area of ​​a lithium battery factory of the utility model can adjust the temperature of the air before entering the NMP recovery device and the NMP entering the supergravity purification device respectively through the direct expansion system, which can effectively reduce the energy consumption of NMP recovery in the lithium battery coating area. At the same time, the structure is relatively simple, no complex and large equipment is added, and the floor space is small;

[0021] The utility model innovatively uses a combination of an ultra-gravity purification device and a pervaporation device to purify NMP waste liquid, thereby obtaining a qualified NMP purification product and reducing the energy consumption of the purification process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The utility model provides an NMP recovery and purification system for a coating area of ​​a lithium battery factory.

[0023] In the figure: 11, oven; 12, coating machine head; 13, coating machine tail; 21 cooler; 22, NMP absorption tower; 23, NMP waste liquid storage tank; 31, evaporator; 32, compressor; 33, condenser; 34, expansion valve; 41, ultra-gravity purifier; 42, reboiler; 43, first reflux tank; 44, first vacuum tank; 51, heater; 52, pervaporator; 53, second reflux tank; 54, second vacuum tank; 55, NMP purified liquid storage tank; 6, heat exchanger. DETAILED DESCRIPTION

[0024] The utility model is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the utility model, and cannot be used to limit the protection scope of the utility model.

[0025] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" 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 it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0027] The utility model discloses a NMP recovery and purification system for a lithium battery factory coating area, which is innovative based on the existing NMP recovery and purification system. The schematic diagram of its structural connection is as follows: Figure 1 As shown, the system mainly includes a coating machine, a heat exchanger 6, an NMP recovery device, a direct expansion system, an ultra-gravity purification device and a pervaporation device. The NMP recovery and purification system can fully utilize the heat energy in the exhaust gas, effectively recover the NMP in the exhaust gas, form NMP waste liquid, and efficiently purify the NMP waste liquid to form a qualified NMP purified liquid. Compared with the existing NMP recovery and purification system, the overall energy consumption of the system is significantly reduced, and the floor space is significantly reduced.

[0028] In a specific embodiment, Figure 1 As shown, the coater includes an oven 11, a coater head 12 and a coater tail 13. The coater head 12 and the coater tail 13 of the coating section of the lithium battery factory are located on both sides of the oven 11. The high temperature in the oven 11 is used to bake out the NMP in the electrode. Each section of the oven 11 is connected to an exhaust duct, and a fan is used to introduce gas into the heat exchanger 6.

[0029] In this embodiment, the heat exchanger 6 includes a heat exchanger high temperature inlet, a heat exchanger low temperature outlet, a heat exchanger low temperature inlet and a heat exchanger high temperature outlet, and gas energy exchange is achieved through the heat exchanger.

[0030] In this embodiment, an exhaust duct is provided above the oven 11 and is connected to an exhaust fan, and the exhaust fan is connected to the high-temperature inlet of the heat exchanger 6 through the exhaust duct; an air supply duct is provided below the oven 11 and is connected to the air supply fan, and the air supply fan is connected to the high-temperature outlet of the heat exchanger 6 through the air supply duct.

[0031] In this embodiment, the NMP recovery device includes a cooler 21, an NMP absorption tower 22 and an NMP waste liquid storage tank 23 connected in sequence, the top outlet of the NMP absorption tower 22 is connected to the low-temperature inlet of the heat exchanger 6, and the outlet of the NMP waste liquid storage tank 23 is connected to the condenser 33 of the direct expansion system.

[0032] In this embodiment, the low temperature outlet of the heat exchanger 6 is connected to the evaporator 31 of the direct expansion system, the cooler 21 of the NMP recovery device, the NMP absorption tower 22 and the NMP waste liquid storage tank 23 in sequence. Among them, the evaporator 31 of the direct expansion system cools the NMP waste gas to liquefy part of the NMP and water in the waste gas; the cooler 21 further liquefies the NMP and water in the waste gas, and the NMP absorption tower 22 absorbs the remaining NMP in the waste gas. Pure water enters the NMP absorption tower 22 from the top of the NMP absorption tower 22. The tower body of the NMP absorption tower 22 adopts a secondary structure, and the recovered NMP waste liquid is stored in the NMP waste liquid storage tank 23.

[0033] In this embodiment, the direct expansion system includes an evaporator 31, a compressor 32, a condenser 33 and an expansion valve 34. The outlet of the evaporator 31 is connected to the compressor 32 and the condenser 33 in sequence, and the outlet of the condenser 33 is connected to the expansion valve 34 and the evaporator 31 in sequence; the outlet of the condenser 33 is also connected to the ultra-gravity purification device. The condenser 33 is connected to the compressor 32 and preheats the NMP waste liquid extracted from the NMP waste liquid storage tank 23.

[0034] In this embodiment, the ultra-gravity purification device includes an ultra-gravity purifier 41, a reboiler 42, a first reflux tank 43 and a first vacuum tank 44. The top of the ultra-gravity purifier 41 is cyclically connected to the first reflux tank 43, and the bottom is cyclically connected to the reboiler 42, and the NMP waste liquid is heated by the reboiler 42; the first reflux tank 43 is connected to the first vacuum tank 44, and the NMP inlet of the ultra-gravity purifier 41 is connected to the condenser 33 of the direct expansion system, and the ultra-gravity purification device 41 is used to process the NMP waste liquid.

[0035] In this embodiment, the pervaporation device includes a heater 51, a pervaporator 52, a second reflux tank 53, a second vacuum tank 54 and an NMP purified liquid storage tank 55, the inlet of the heater 51 is connected to the bottom of the reboiler 42 of the ultragravity purification equipment, and the outlet is connected to the pervaporator 52, the outlet of the pervaporator 52 is respectively connected to the second reflux tank 53 and the NMP purified liquid storage tank 55, and the second reflux tank 53 is also connected to the second vacuum tank 54. Through the action of the second vacuum tank 54, one side of the pervaporation membrane is always maintained in a near vacuum state, thereby achieving continuous pervaporation.

[0036] The following is a further detailed description of the NMP recovery and purification system through a specific implementation method:

[0037] The NMP waste gas in the coating machine oven 11 is sent to the heat exchanger 6 by a fan, and the temperature of the high-temperature inlet is 130°C. The temperature of the gas after NMP recovery treatment reaches 95°C after heat exchange, and the heat exchange efficiency is more than 75%. The gas after heat exchange is sent back to the oven 11; the evaporator 31 of the direct expansion system cools the NMP waste gas to 50°C to remove part of the NMP and moisture in the waste gas, and the cooler 21 is used to further cool the NMP waste gas, and the NMP and moisture in the waste gas are continuously collected, and the removed NMP and moisture are pumped to the NMP waste liquid storage tank 23. Furthermore, the cooled exhaust gas is pumped into the NMP absorption tower 22, which is more than 11 meters high. Pure water is sprayed from the top of the tower to the bottom of the tower. The tower body is divided into two layers, and fillers are filled inside to increase the mass transfer area. More than 95% of the wind is pumped from the top of the tower to the heat exchanger, and another 1%-5% of the wind is discharged to maintain the negative pressure in the oven 11.

[0038] The NMP waste liquid extracted from the NMP waste liquid storage tank 23 is preheated by using the condenser 33 of the direct expansion system, and the temperature of the NMP waste liquid can be increased to 50°C; the NMP waste liquid is continuously heated by using the reboiler 42, the bottom temperature of the ultra-gravity purification device 41 is 150-160°C, and the internal pressure of the device is 5-7kPa. The ultra-gravity purification device 41 is used to separate the components of the NMP waste liquid, and most of the water in the NMP waste liquid is separated from the top of the ultra-gravity purification device 41, and the first reflux tank 43 is used to collect it, and the first vacuum tank 44 is used to return part of the liquid in the first reflux tank 43 to the ultra-gravity purification device 41, and the other part is extracted to the NMP waste liquid storage tank 24; the main components at the bottom of the ultra-gravity purification device 41 are NMP and a small amount of water.

[0039] A power pump is used to pump the filtered NMP waste liquid to the heater 51, the heating temperature is set to 140-160°C, and the heated gaseous substance is pumped to the pervaporator 52; a vacuum pump is used to maintain one side of the pervaporation membrane in a near vacuum state, and the special pervaporation membrane can selectively pervaporate the water in the NMP waste liquid. After being treated by the pervaporation membrane, the remaining water in the NMP waste liquid is removed. A power pump is used to pump the NMP purified liquid at the bottom of the pervaporation membrane to the NMP purified liquid storage tank 55.

[0040] By using the NMP recovery and purification system in the coating area of ​​the lithium battery factory in this embodiment, the NMP in the exhaust gas of the coating area can be effectively recovered and purified. Compared with the traditional rotary NMP recovery system, the utility model uses a direct expansion system evaporator to adjust the temperature of the air before entering the deep condenser; the direct expansion system condenser is arranged before the ultra-gravity purification equipment, and is used to adjust the temperature of the NMP waste liquid entering the ultra-gravity purification equipment. The application of the direct expansion system effectively reduces the energy consumption of NMP recovery in the lithium battery coating area. In addition, the utility model innovatively uses a combination of an ultra-gravity purification device and a pervaporation device to purify the NMP waste liquid, while obtaining a qualified NMP purification product, further reducing the energy consumption of the NMP waste liquid purification process.

[0041] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A NMP recovery and purification system for the coating area of ​​a lithium battery factory, characterized in that: It includes heat exchanger, NMP recovery unit, direct expansion system, ultra-gravity purification unit and pervaporation unit; The heat exchanger is used to recover the heat energy of the NMP waste gas generated in the coating area; The NMP recovery device is connected to a heat exchanger for liquefying and recovering NMP; The direct expansion system is respectively connected to a heat exchanger, an NMP recovery device and an ultra-gravity purification device, and is used to pre-treat the NMP waste gas and preheat the NMP waste liquid; The ultra-gravity purification device is connected to the NMP recovery device, and the pervaporation device is connected to the ultra-gravity purification device, so as to remove water from the NMP waste liquid and obtain the NMP purified liquid.

2. The NMP recovery and purification system in the coating area of ​​a lithium battery factory according to claim 1, characterized in that: The NMP recovery and purification system also includes a coater, which includes an oven for drying out the NMP in the pole piece, and a coater head and a coater tail are respectively provided on both sides of the oven.

3. The NMP recovery and purification system in the coating area of ​​a lithium battery factory according to claim 2, characterized in that: The oven is connected to an exhaust duct and an exhaust fan, and the exhaust duct is connected to a high-temperature inlet of a heat exchanger; the oven is also connected to an air supply duct and an air supply fan, and the air supply duct is connected to a high-temperature outlet of the heat exchanger.

4. The NMP recovery and purification system in the coating area of ​​a lithium battery factory according to claim 1, characterized in that: The low-temperature outlet of the heat exchanger is connected in sequence to the evaporator of the direct expansion system, the cooler of the NMP recovery device, the NMP absorption tower and the NMP waste liquid storage tank.

5. The NMP recovery and purification system in the coating area of ​​a lithium battery factory according to claim 4, characterized in that: The NMP recovery device comprises a cooler, an NMP absorption tower and an NMP waste liquid storage tank which are connected in sequence, the top outlet of the NMP absorption tower is connected to the low temperature inlet of the heat exchanger, and the outlet of the NMP waste liquid storage tank is connected to the condenser of the direct expansion system.

6. The NMP recovery and purification system in the coating area of ​​a lithium battery factory according to claim 4, characterized in that: The direct expansion system includes an evaporator, a compressor, a condenser and an expansion valve. The outlet of the evaporator is connected to the compressor and the condenser in sequence, and the outlet of the condenser is connected to the expansion valve and the evaporator in sequence; the outlet of the condenser is also connected to an ultra-gravity purification device.

7. The NMP recovery and purification system in the coating area of ​​a lithium battery factory according to claim 1, characterized in that: The ultra-gravity purification device comprises an ultra-gravity purifier, a reboiler, a first reflux tank and a first vacuum tank. The top of the ultra-gravity purifier is circularly connected to the first reflux tank, and the bottom is circularly connected to the reboiler. The first reflux tank is connected to the first vacuum tank. The NMP inlet of the ultra-gravity purifier is also connected to the condenser of the direct expansion system.

8. The NMP recovery and purification system in the coating area of ​​a lithium battery factory according to claim 1, characterized in that: The pervaporation device comprises a heater, a pervaporator, a second reflux tank, a second vacuum tank and an NMP purified liquid storage tank, wherein the inlet of the heater is connected to the bottom of the reboiler of the ultragravity purification equipment, and the outlet is connected to the pervaporator, the outlet of the pervaporator is respectively connected to the second reflux tank and the NMP purified liquid storage tank, and the second reflux tank is also connected to the second vacuum tank.

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