NMP waste gas recovery and purification system

Abstract

The utility model discloses an NMP waste gas recovery and purification system which comprises a spraying absorption tower connected with NMP waste gas, the bottom of the spraying absorption tower is connected with a reverse osmosis membrane dehydration device through a pipeline, and a liquid outlet of the reverse osmosis membrane dehydration device is connected with a liquid-liquid heat exchanger and is connected with a rectifying tower through the liquid-liquid heat exchanger. According to the NMP waste gas recovery and purification system, heat in NMP waste gas and heat in a rectified NMP finished product are fully recovered and then applied to the NMP recovery and purification system, and the energy consumption of the system is greatly reduced. In addition, compared with a traditional multi-tower rectification purification NMP system, the NMP pure product is obtained by adopting a method of rough filtration, reverse osmosis dehydration and single-tower rectification heavy component removal. According to the method, the multi-tower rectification process is omitted, the energy consumption is greatly reduced, and the operation cost is saved.

Description

Technical Field

[0001] The utility model relates to an NMP recovery and purification system, in particular to an NMP waste gas recovery and purification system. Background Technique

[0002] The molecular formula of N-methylpyrrolidone is C5H9NO, and its English name is N-Methyl pyrrolidone (abbreviated as NMP). It is an important chemical raw material that is colorless, transparent, oily, and slightly amine-smelling. It is easily soluble in water, ethanol, ether, acetone, ethyl acetate, chloroform, and benzene. Due to its strong polarity, good solubility, and high chemical stability, NMP is widely used in the production of lithium battery positive electrode sheets. The NMP in the electrode sheets will be baked out during the coating process and enter the recovery treatment system. After treatment, the NMP waste gas is dissolved in water to form a high-concentration NMP waste liquid.

[0003] At present, there are mainly two disposal methods for the NMP waste liquid recovered by coating machines in lithium battery factories. The first method is to store the NMP waste liquid in a waste liquid tank, and regularly transport the stored waste liquid to a professional chemical purification factory for purification, and then purchase the purified NMP finished product and transport it back to the factory for production. The problems with this disposal method are high transportation costs, and NMP belongs to hazardous organic waste, which is toxic, flammable, and explosive by itself. Therefore, long-distance and large-scale transportation has certain safety hazards and greater environmental risks. The second disposal method is that the lithium battery factory disposes of the recovered NMP waste liquid on-site and uses multi-column distillation to purify and reuse the NMP waste liquid. The problems with this method are that the traditional multi-column distillation occupies a large area, has high investment and operating costs, and requires extremely high energy consumption due to multiple heating, which does not conform to the concept of environmental protection production. Content of the Utility Model

[0004] The purpose of the utility model is to provide an NMP waste gas recovery and purification system to solve the problems raised in the above background technique.

[0005] To achieve the above purpose, the utility model provides the following technical solutions:

[0006] An NMP waste gas recovery and purification system includes a spray absorption tower connected to NMP waste gas. The bottom of the spray absorption tower is connected to a reverse osmosis membrane dehydration device through a pipeline. The liquid outlet of the reverse osmosis membrane dehydration device is connected to a liquid-liquid heat exchanger and is connected to a distillation column through the liquid-liquid heat exchanger. The upper outlet of the distillation column is communicated with the liquid-liquid heat exchanger and discharged through the liquid-liquid heat exchanger.

[0007] The NMP waste gas is absorbed by a spray absorption tower, and the NMP waste liquid is dehydrated by a reverse osmosis membrane dehydration device. The dehydrated NMP waste liquid is then rectified and purified by a rectification tower. Multi-column rectification can be avoided. At the same time, a liquid-liquid heat exchanger is provided to recover the heat in the rectified NMP finished product and reduce the system energy consumption.

[0008] As a further solution of the present utility model: the spray absorption tower is connected to the coating machine, the NMP waste gas exhaust end of the coating machine is connected to the spray absorption tower through a gas-gas heat exchanger and a circulation fan, and the upper part of the spray absorption tower is connected to the heat exchange pipeline of the gas-gas heat exchanger.

[0009] By setting up a gas-gas heat exchanger, the heat in the NMP waste gas can be recovered, reducing the overall energy consumption of the system.

[0010] As a further solution of the present utility model: a closed cooling tower is connected to the spray absorption tower, and the closed cooling tower is connected to the spray absorption tower through a circulating pump group and a circulating pipeline.

[0011] By commonly setting up a closed cooling tower, the NMP waste liquid and the absorption liquid in the spray absorption tower can be quickly cooled, improving the acquisition speed of the NMP waste liquid.

[0012] As a further solution of the present utility model: the spray device on the upper part of the spray absorption tower is connected to a pure water unit through a pure water pump.

[0013] The pure water unit provides pure water to the spray absorption tower, and the NMP waste gas is absorbed by the pure water to form NMP waste liquid, so as to recover the NMP waste gas.

[0014] As a further solution of the present utility model: the bottom of the spray absorption tower is connected to an NMP waste liquid tank through a pipeline, and a coarse filtration device is connected between the NMP waste liquid tank and the reverse osmosis membrane dehydration device.

[0015] By the coarse filtration device, larger impurity particles in the waste liquid can be filtered, reducing the load of subsequent equipment and improving the purification efficiency.

[0016] As a further solution of the present utility model: the coarse filtration device is connected to the NMP waste liquid tank through a first power pump.

[0017] The coarsely filtered waste liquid is pumped into the waste liquid tank by the power pump.

[0018] As a further solution of the present utility model: a buffer tank is provided between the coarse filtration device and the reverse osmosis membrane dehydration device, and a second power pump is provided between the buffer tank and the reverse osmosis membrane dehydration device.

[0019] By setting up a buffer tank, the NMP waste liquid entering the reverse osmosis membrane dehydration device can be buffered to ensure the stability of the NMP waste liquid entering the reverse osmosis membrane dehydration device and avoid large fluctuations in the inflow rate.

[0020] As a further solution of the present utility model: the reverse osmosis membrane dehydration device is a high-frequency reverse osmosis membrane dehydration device, and the reverse osmosis membrane dehydration device is connected to the liquid-liquid heat exchanger through a third power pump.

[0021] The dewatered NMP cost is incorporated into the liquid-liquid heat exchanger through a power pump, and the NMP waste liquid before distillation is heated by the heat of the liquid-liquid heat exchanger and the finished product liquid, so as to increase the temperature of the NMP waste liquid entering the distillation column and reduce the distillation energy consumption.

[0022] As a further solution of the present utility model: the upper outlet of the distillation column is connected with a condenser, the rear end of the condenser is connected with a condensate tank, and the condensate tank is connected with a finished product tank through a reflux pump and a liquid-liquid heat exchanger heat exchange pipeline.

[0023] The heat carried by the finished product after distillation is transferred to the undistilled NMP waste liquid through the liquid-liquid heat exchanger.

[0024] As a further solution of the present utility model: the distillation column is connected with a reboiler through a circulation pipeline, and the outlet at the bottom of the distillation column is provided with a fourth power pump.

[0025] The bottom outlet of the distillation column is connected with a reboiler. A part of the material obtained from the bottom outlet of the distillation column through the fourth power pump is returned to the distillation column after being heated by the reboiler, and the other part is regularly taken out and outsourced for treatment.

[0026] Compared with the prior art, the beneficial effects of the present utility model are as follows: This application fully recovers the heat in the NMP waste gas and the heat in the NMP finished product after distillation, and then applies it to this set of NMP recovery and purification system, greatly reducing the system energy consumption. In addition, compared with the traditional multi-column distillation and purification NMP system, this application uses the method of coarse filtration plus reverse osmosis dehydration plus single-column distillation and deweighting to obtain NMP pure product. This method omits the process of multi-column distillation, greatly reducing the energy consumption and saving the operation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the schematic diagram of the recovery and purification system in this embodiment;

[0028] In the figure: 1 - Coater, 2 - Gas-gas heat exchanger, 3 - Circulation fan, 4 - Spray absorption tower, 5 - Circulation pump group, 6 - Closed cooling tower, 7 - Pure water unit, 8 - Pure water pump, 9 - NMP waste liquid tank, 10 - First power pump, 11 - Coarse filtration device, 12 - Buffer tank, 13 - Second power pump, 14 - Reverse osmosis membrane dehydration device, 15 - Third power pump, 16 - Liquid-liquid heat exchanger, 17 - Return pump, 18 - Condensation tank, 19 - Rectifying column, 20 - Condenser, 21 - Reboiler, 22 - Fourth power pump, 23 - Product tank. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Please refer to Figure 1 , in the embodiment of the present invention, an NMP waste gas recovery and purification system includes a spray absorption tower 4 connected to the NMP waste gas. The spray absorption tower 4 is communicated with the coater 1. The NMP waste gas exhaust end of the coater 1 is communicated with the spray absorption tower 4 through the gas-gas heat exchanger 2 and the circulation fan 3. The upper part of the spray absorption tower 4 is communicated with the heat exchange pipeline of the gas-gas heat exchanger 2. By setting the gas-gas heat exchanger 2, the heat in the NMP waste gas can be recovered, reducing the overall energy consumption of the system. A closed cooling tower 6 is connected to the spray absorption tower 4. The closed cooling tower 6 is communicated with the spray absorption tower 4 through the circulation pump group 5 and the circulation pipeline. The spray device at the upper part of the spray absorption tower 4 is connected to the pure water unit 7 through the pure water pump 8. The pure water unit 7 provides pure water to the spray absorption tower 4, and the NMP waste gas is absorbed by the pure water to form NMP waste liquid, so as to recover the NMP waste gas.

[0031] The bottom of the spray absorption tower 4 is connected to an NMP waste liquid tank 9 through a pipeline. The bottom of the spray absorption tower 4 is connected to a reverse osmosis membrane dehydration device 14 through a pipeline. A coarse filtration device 11 is connected between the NMP waste liquid tank 9 and the reverse osmosis membrane dehydration device 14. Larger impurity particles in the waste liquid can be filtered through the coarse filtration device 11, reducing the load of subsequent equipment and improving the purification efficiency. The filtration accuracy of the coarse filtration device 11 is 1um. The coarse filtration device 11 is communicated with the NMP waste liquid tank 9 through a first power pump 10. A buffer tank 12 is arranged between the coarse filtration device 11 and the reverse osmosis membrane dehydration device 14. A second power pump 13 is arranged between the buffer tank 12 and the reverse osmosis membrane dehydration device 14. By setting the buffer tank 12, the NMP waste liquid entering the reverse osmosis membrane dehydration device 14 can be buffered, ensuring the stability of the NMP waste liquid entering the reverse osmosis membrane dehydration device 14 and avoiding large fluctuations in the inlet flow rate.

[0032] The reverse osmosis membrane dehydration device 14 is a high-frequency reverse osmosis membrane dehydration device. The liquid outlet of the reverse osmosis membrane dehydration device 14 is connected to a liquid-liquid heat exchanger 16 and is connected to a rectification tower 19 through the liquid-liquid heat exchanger 16. The dehydrated NMP waste liquid is further rectified and purified through the rectification tower 19, and multi-tower rectification can be avoided. The reverse osmosis membrane dehydration device 14 is communicated with the liquid-liquid heat exchanger 16 through a third power pump 15. The upper outlet of the rectification tower 19 is communicated with the liquid-liquid heat exchanger 16 and is discharged through the liquid-liquid heat exchanger 16. In this embodiment, the upper outlet of the rectification tower 19 is connected to a condenser 20. The rear end of the condenser 20 is connected to a condensate tank 18. The condensate tank 18 is connected to a finished product tank 23 through a reflux pump 17 and a liquid-liquid heat exchanger 16 heat exchange pipeline. The NMP waste gas is absorbed through the spray absorption tower 4, the NMP waste liquid is dehydrated through the reverse osmosis membrane dehydration device 14, and the dehydrated NMP cost is incorporated into the liquid-liquid heat exchanger 16 through a power pump. The NMP waste liquid before rectification is heated through the liquid-liquid heat exchanger 16 and the heat of the finished product liquid, increasing the temperature of the NMP waste liquid entering the rectification tower 19 and reducing the rectification energy consumption.

[0033] The rectification tower 19 is connected to a reboiler 21 through a circulation pipeline. The outlet at the bottom of the rectification tower 19 is provided with a fourth power pump 22. The bottom discharge port of the rectification tower 19 is connected to the reboiler 21. A part of the material obtained from the bottom outlet of the rectification tower through the fourth power pump 22 returns to the rectification tower after being heated by the reboiler, and the other part is regularly taken out and outsourced for treatment.

[0034] When the present utility model is in use, the high-temperature NMP waste gas discharged from the coater 1 is sent to the gas-gas heat exchanger 2 through a pipeline. The heat in the NMP waste gas is recovered through the gas-gas heat exchanger. More than 90-95% of the treated waste gas is sent to the waste heat recovery heat exchanger for preheating, and the preheated waste gas is circulated back to the coating line. The remaining 5-10% of the up-to-standard tail gas is discharged.

[0035] The NMP waste gas cooled after heat recovery enters the spray absorption tower 4, where it comes into countercurrent contact with the spray circulating liquid. The circulating liquid absorbs most of the NMP in the waste gas. The waste gas containing a small amount of NMP enters the second stage of the absorption tower. At the same time, the pure water pump 8 pumps the pure water from the pure water unit 7 into the top of the spray absorption tower 4. The small amount of NMP waste gas comes into countercurrent contact with the pure water again, further washing and absorbing the tail gas, so that the NMP waste gas can meet the discharge standards. The circulating liquid pumped out by the circulating pump group 5 enters the closed cooling tower 6, where it is cooled. The cooled circulating liquid then enters the spray absorption tower 4 again to absorb the NMP waste gas in the tower. When the spray circulating liquid at the bottom of the spray absorption tower 4 reaches the set concentration (NMP concentration ≥ 85%), a part is extracted and stored in the waste liquid tank 9.

[0036] The NMP in the waste liquid tank 9 is pumped into the coarse filtration device 11 by the first power pump 10 for filtration to remove larger particle impurities in the waste liquid. In this embodiment, the filtration accuracy of the coarse filtration device 11 is 1um. Subsequently, the coarsely filtered NMP waste liquid enters the buffer tank 12. The NMP in the buffer tank 12 enters the high-frequency reverse osmosis membrane dehydration device 14 through the second power pump 13 for dehydration. The dehydrated NMP is pumped into the liquid-liquid heat exchanger 16 by the third power pump 15 and then enters the distillation column 19. The distillation column 19 is used for removing heavy components from the dehydrated high-purity NMP liquid. The NMP separated from the top of the distillation column enters the condensation tank 18 after being condensed by the condenser 20. Subsequently, through the transportation of a reflux pump 17, a part of it refluxes into the distillation column 19, and the other part exchanges heat with the dehydrated high-purity NMP after passing through the liquid-liquid heat exchanger 16 and then enters the finished product tank 23; the waste heat of the high-temperature NMP liquid taken by the distillation column is fully utilized to exchange heat with the NMP liquid to be de-heavy-component entering the tower, thereby reducing the energy consumption of the distillation column.

[0037] The bottom discharge port of the distillation column is connected with a reboiler 21. A part of the material obtained from the bottom of the distillation column through the extraction port of the fourth power pump 22 returns to the distillation column after being heated by the reboiler, and the other part is regularly extracted and outsourced for treatment.

[0038] For those skilled in the art, it is obvious that the present utility model is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present utility model. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present utility model. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0039] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An NMP waste gas recovery and purification system, comprising a spray absorption tower (4) connected to the NMP waste gas, characterized in that, The bottom of the spray absorption tower (4) is connected to a reverse osmosis membrane dehydration device (14) through a pipeline. The liquid outlet of the reverse osmosis membrane dehydration device (14) is connected to a liquid-liquid heat exchanger (16) and is connected to a distillation column (19) through the liquid-liquid heat exchanger (16). The upper outlet of the distillation column (19) communicates with the liquid-liquid heat exchanger (16) and is discharged through the liquid-liquid heat exchanger (16).

2. The NMP waste gas recovery and purification system according to claim 1, wherein, The spray absorption tower (4) is connected to a coater (1). The NMP waste gas exhaust end of the coater (1) is connected to the spray absorption tower (4) through a gas-gas heat exchanger (2) and a circulation fan (3). The upper part of the spray absorption tower (4) is connected to the heat exchange pipeline of the gas-gas heat exchanger (2).

3. The NMP waste gas recovery and purification system according to claim 1, wherein A closed cooling tower (6) is connected to the spray absorption tower (4). The closed cooling tower (6) is connected to the spray absorption tower (4) through a circulating pump group (5) and a circulating pipeline.

4. A NMP waste gas recovery and purification system according to claim 1, wherein, The spray device at the upper part of the spray absorption tower (4) is connected to a pure water unit (7) through a pure water pump (8).

5. The NMP waste gas recovery and purification system according to claim 1, characterized in that, The bottom of the spray absorption tower (4) is connected to an NMP waste liquid tank (9) through a pipeline. A coarse filtration device (11) is connected between the NMP waste liquid tank (9) and the reverse osmosis membrane dehydration device (14).

6. The NMP waste gas recovery and purification system according to claim 5, wherein, The coarse filtration device (11) is connected to the NMP waste liquid tank (9) through a first power pump (10).

7. An NMP waste gas recovery and purification system according to claim 5, characterized in that, A buffer tank (12) is provided between the coarse filtration device (11) and the reverse osmosis membrane dehydration device (14). A second power pump (13) is provided between the buffer tank (12) and the reverse osmosis membrane dehydration device (14).

8. An NMP waste gas recovery and purification system according to claim 1, characterized in that, The reverse osmosis membrane dehydration device (14) is a high-frequency reverse osmosis membrane dehydration device. The reverse osmosis membrane dehydration device (14) is connected to the liquid-liquid heat exchanger (16) through a third power pump (15).

9. The NMP waste gas recovery and purification system according to claim 1, characterized in that, The upper outlet of the distillation column (19) is connected to a condenser (20). The rear end of the condenser (20) is connected to a condensate tank (18). The condensate tank (18) is connected to a finished product tank (23) through a reflux pump (17) and the heat exchange pipeline of the liquid-liquid heat exchanger (16).

10. A NMP waste gas recovery and purification system according to claim 1, characterized in that, The distillation column (19) is connected to a reboiler (21) through a circulation pipeline. The outlet at the bottom of the distillation column (19) is provided with a fourth power pump (22).

Images