N-methylpyrrolidone-containing waste gas recovery treatment apparatus and method

Abstract

Provided are an N-methylpyrrolidone-containing waste gas recovery treatment apparatus and method. The apparatus comprises an absorption unit and a molecular sieve membrane dehydration unit which are connected to each other. The recovery treatment method comprises: treating a waste gas containing a certain amount of N-methylpyrrolidone by means of an absorption unit, and then carrying out dehydration operation treatment on a treatment liquid by means of a molecular sieve membrane dehydration unit to obtain electronic-grade N-methylpyrrolidone and an exhaust gas, wherein the exhaust gas is conveyed to the absorption unit for treatment and then is discharged, and the electronic-grade N-methylpyrrolidone is cooled for later use. The treatment apparatus reduces the operation cost and the device investment cost, and avoids the problem in a conventional membrane dehydration apparatus of requiring secondary treatment for permeate condensate waste liquid. According to the waste gas recovery treatment method, the molecular sieve membrane dehydration technology is used for treatment, energy in high-temperature exhaust gas can be fully utilized, and water generated in the entire process is discharged from the absorption unit in the form of saturated water, thereby achieving zero-pollution-emission treatment in the process.

Description

A device and method for recovering and treating waste gas containing N-methylpyrrolidone

[0001] This application claims priority to Chinese patent applications with application number 202310955478.9, filed on July 31, 2023, entitled “A method and device for recovering and treating waste gas containing N-methylpyrrolidone”, and application number 202322041321.3, entitled “A device for recovering and treating waste gas containing N-methylpyrrolidone”, all of which are incorporated herein by reference. Technical Field

[0002] The present application belongs to the technical field of organic waste gas recovery, and specifically relates to a device and method for recovering and treating waste gas containing N-methylpyrrolidone. Background Art

[0003] N-Methylpyrrolidone (NMP) is a highly soluble aprotic solvent. It is a colorless, transparent, oily liquid with a slight amine odor. Due to its low volatility and excellent thermal and chemical stability, NMP is widely used in the lithium battery, pharmaceutical, pesticide, electronics, petrochemical, and other industries due to its excellent performance. During the lithium battery manufacturing process, NMP itself does not enter the final lithium battery product. Instead, it serves as a solvent for dispersing the binder. It evaporates at a certain temperature during the drying process, and NMP is discharged from the production equipment as waste gas. If this waste gas is directly discharged into the atmosphere without recovery and treatment, it will cause both environmental pollution and waste of resources. Therefore, the recovery and purification of this waste gas is of great significance.

[0004] Currently, the common N-methylpyrrolidone recovery and purification devices in the related art typically utilize a multi-tower distillation structure for purification and intermodal operation. However, this device requires large investment, high energy consumption, and complex operation. Furthermore, several methods for recovering N-methylpyrrolidone have been proposed in the related art. For example, one researcher has used three towers in series and subjected them to precision treatment in an adsorption tower to recover and purify NMP waste gas from lithium battery production into electronic-grade NMP solvent, which can be directly used as a solvent for positive and negative electrode materials in lithium battery production. However, this method deactivates the adsorbent, turning it into solid waste, and the multi-tower distillation process consumes high evaporation energy. Furthermore, some researchers have used porous ceramic filter membrane separators combined with pervaporation membranes to separate NMP from water. The operating temperature during the recovery process is below the boiling point of the NMP recovered liquid. However, the continuous circulation of water in this method results in substandard exhaust emissions from the absorption tower overhead in the later stages of the absorption process. The permeate wastewater and vacuum exhaust generated during the membrane dehydration process require secondary treatment, presenting numerous problems. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems existing in the prior art. To this end, this application proposes a device and method for recovering and treating waste gas containing N-methylpyrrolidone. This device can achieve ultra-low emission indicators for waste gas, has good treatment effects, achieves zero pollution emission treatment throughout the entire process, eliminates the need for secondary pollutant treatment, and significantly saves energy.

[0006] According to a first aspect of the present application, there is provided a waste gas recovery and treatment device containing N-methylpyrrolidone, the waste gas recovery and treatment device comprising:

[0007] An absorption unit comprising a heat exchange device, a first phase separation device, and an absorption device, wherein the heat exchange device, the first phase separation device, and the absorption device are connected in sequence;

[0008] The molecular sieve membrane dehydration unit is connected to the absorption unit, and the molecular sieve membrane dehydration unit comprises a filtering device, a heat exchange device, a first heating device, and a molecular sieve membrane assembly, which are connected in sequence.

[0009] The N-methylpyrrolidone-containing waste gas recovery and treatment device according to the embodiment of the present application has at least the following beneficial effects: the device includes an absorption unit and a molecular sieve membrane dehydration unit, which can ensure the continuous and stable operation of the system. Using this set of treatment devices, the absorption rich liquid concentration can be concentrated to more than 92%, greatly reducing the energy consumption of the membrane dehydration process and the number of membrane components, reducing operating costs and equipment investment costs. Compared with traditional membrane dehydration devices, this application eliminates the permeate vapor condenser, avoiding the problem of secondary treatment of the permeate condensation waste liquid in traditional membrane dehydration devices.

[0010] According to some embodiments of the present application, the absorption device comprises:

[0011] A bottom portion, wherein one side of the bottom portion is provided with an exhaust gas inlet and the other side of the bottom portion is provided with an absorption rich liquid outlet;

[0012] In the middle, an absorbent circulation inlet is provided;

[0013] The top portion is provided with an absorbent inlet on one side and an exhaust gas outlet on the other side.

[0014] According to some embodiments of the present application, the absorption device includes: an absorption tower, one end of which is connected to the first phase separation device;

[0015] The waste gas recovery and treatment device also includes a first condensing device connected to the other end of the absorption tower, which is used to condense the material transported from the other end of the absorption tower and return it to the absorption tower.

[0016] It can be understood that the absorption tower of the present application adopts a combination of bubble trays and plate corrugated packings and packings, which can transfer N-methylpyrrolidone from a content of 0.001~2wt% in the gas phase to a content of 90~95wt% in the liquid phase, thereby achieving high-concentration enrichment and concentration, while achieving ultra-low emission indicators of the top exhaust gas. The low water content of N-methylpyrrolidone rich liquid also further reduces the load of molecular sieve membrane dehydration, which can further save energy consumption.

[0017] According to some embodiments of the present application, the absorption unit further comprises a first material conveying device, one end of which is connected to the first phase separation device;

[0018] The first phase separation device comprises:

[0019] a first gas phase outlet connected to the exhaust gas inlet;

[0020] The first liquid phase outlet is connected to the first material conveying equipment.

[0021] According to some embodiments of the present application, the exhaust gas outlet is connected to the heat exchange medium inlet of the heat exchange device;

[0022] The absorption rich liquid outlet is connected to a second material conveying device, and one end of the second material conveying device is connected to the absorbent circulation inlet.

[0023] It is understandable that the other end of the second material conveying device can also be used to be connected to the molecular sieve membrane dehydration unit to convey the absorption rich liquid outlet to the molecular sieve membrane dehydration unit for further processing.

[0024] According to some embodiments of the present application, a material liquid phase inlet is provided on one side of the molecular sieve membrane assembly, and a material liquid phase outlet and a vacuum port are provided on the other side. The material liquid phase inlet is connected to the first heating device, and the material liquid phase outlet is connected to the heat exchange medium inlet of the heat exchange device.

[0025] It can be understood that the present application provides a material liquid phase outlet on the other side of the molecular sieve membrane assembly, and the material discharged from the material liquid phase outlet enters the heat exchange medium inlet of the heat exchange device and can be further used as a heat exchange medium.

[0026] According to some embodiments of the present application, the molecular sieve membrane dehydration unit further includes:

[0027] A third cooling device comprises a gas phase inlet and a gas phase outlet, wherein the gas phase inlet is connected to a portion of the vacuum port in the molecular sieve membrane assembly;

[0028] a first vacuum unit connected to the gas phase outlet of the third cooling device;

[0029] The second vacuum unit has an inlet connected to another vacuum port in the molecular sieve membrane assembly.

[0030] It should be noted that the first vacuum unit and the second vacuum unit of the present application are directly or indirectly arranged on one side of the molecular sieve membrane assembly to provide vacuum for the osmosis process. As the driving force for water molecules to pass through the molecular sieve membrane assembly, they can enhance the pervaporation dehydration process of the molecular sieve membrane assembly.

[0031] According to some embodiments of the present application, the outlet of the first vacuum unit and the outlet of the second vacuum unit are respectively connected to the exhaust gas inlet at the bottom of the absorption equipment.

[0032] It is understandable that the present application connects the outlet of the first vacuum unit and the tail gas of the second vacuum unit directly to the waste gas inlet at the bottom of the absorption equipment, so that the tail gas can be directly recycled and processed, so that the tail gas containing 0.1~2wt% of N-methylpyrrolidone separated by the molecular sieve membrane assembly is processed by the absorption equipment, and the water generated during the whole process is discharged from the top of the absorption tower in the form of saturated water, thus achieving zero pollution emission treatment during the process. In addition, the outlet of the first vacuum unit and the tail gas of the second vacuum unit proposed in the present application are directly connected to the waste gas inlet at the bottom of the absorption equipment, which can perfectly solve the problem of secondary treatment of vacuum tail gas and permeate condensate waste liquid in the traditional membrane dehydration process.

[0033] According to a second aspect of the present application, a method for recovering and treating waste gas containing N-methylpyrrolidone is provided, comprising the following steps:

[0034] The waste gas containing a certain amount of N-methylpyrrolidone is treated through an absorption unit to obtain a treated liquid;

[0035] The treated liquid is dehydrated by a molecular sieve membrane dehydration unit to obtain electronic grade N-methylpyrrolidone and tail gas, wherein the tail gas is transported to the absorption unit for treatment and then discharged, and the electronic grade N-methylpyrrolidone is cooled for standby use.

[0036] Among them, the waste gas recovery and treatment method of the above-mentioned embodiment of the present application is to process the waste gas containing N-methylpyrrolidone through an absorption unit, and then transfer the N-methylpyrrolidone in the waste gas from the gas phase to the liquid phase by absorption, and use molecular sieve membrane dehydration technology to perform deep dehydration and purification treatment. The separated tail gas is processed by the absorption unit, and the water generated in the whole process is discharged from the absorption unit in the form of saturated water, realizing zero pollution emission treatment in the process, and finally obtaining electronic grade N-methylpyrrolidone. It can be understood that the electronic grade N-methylpyrrolidone referred to in the embodiment of the present application means that the content of N-methylpyrrolidone reaches 99.9wt%.

[0037] According to some embodiments of the present application, the step of treating the exhaust gas containing a certain amount of N-methylpyrrolidone through an absorption unit includes the following steps:

[0038] The exhaust gas is first passed through a heat exchange device for heat exchange treatment, and then phase separated, and the condensate after the phase separation is collected for standby use;

[0039] The non-condensable gas phase obtained by the phase separation is transported to an absorption device for absorption treatment. After the absorption treatment, a liquid phase material and a gas phase material are obtained, wherein 75-95% of the rich liquid in the liquid phase material is returned to the middle part of the absorption device for treatment and circulation, and 5-25% of the rich liquid is buffered for standby use. The buffered rich liquid is pressurized to obtain the treated liquid;

[0040] The gas phase substance enters the heat exchange equipment as a heat exchange medium.

[0041] It can be understood that the waste gas containing N-methylpyrrolidone is separated into non-condensable gas phase matter and condensate by phase separation. The non-condensable gas phase matter will enter the absorption equipment for absorption treatment, and the condensate will be collected and transported to the molecular sieve membrane unit for further treatment.

[0042] According to some embodiments of the present application, after obtaining the treatment liquid, the following process is further included:

[0043] The treatment liquid is heated to 100-140° C. and then enters the molecular sieve membrane dehydration unit for dehydration treatment.

[0044] It is understood that the condensate obtained after phase separation can also be heated to 100-140° C. and then enter the molecular sieve membrane dehydration unit for dehydration treatment.

[0045] According to some embodiments of the present application, the heat exchange treatment includes two heat exchange processes, wherein the first heat exchange process is carried out at 80-120°C, and the second heat exchange process is carried out at 10-40°C.

[0046] It can be understood that the present application sets up two heat exchange processes because the first heat exchange process is to exchange heat between the exhaust gas at the top of the absorption tower equipment and the raw gas, so that the exhaust gas is heated to an unsaturated state, which plays a role in "whitening", while the second heat exchange process is to reduce the temperature of the exhaust gas entering other equipment to protect other equipment.

[0047] According to some embodiments of the present application, the dehydration operation comprises the following steps:

[0048] The treatment liquid is treated in a plurality of molecular sieve membrane modules in series operation, wherein the series operation includes primary osmosis and secondary osmosis, wherein the gas obtained from the primary osmosis treatment is subjected to condensation treatment, and then the condensate after the condensation treatment is transported to the absorbent circulation inlet of the absorption unit, and the gas obtained from the secondary osmosis treatment is directly returned to the absorption unit.

[0049] It should be noted that the deep dehydration of the molecular sieve membrane assembly can be divided into two stages, including primary osmosis and secondary osmosis, which can further enhance the efficiency of deep dehydration.

[0050] According to some embodiments of the present application, the operating pressure of the primary osmosis is 0.1~3kPaA, and the operating pressure of the secondary osmosis is 0.1~5kPaA.

[0051] According to some embodiments of the present application, after the series operation, the electronic grade N-methylpyrrolidone material discharged at the liquid phase outlet of the material is cooled and used for standby after heat exchange and energy recovery.

[0052] According to some embodiments of the present application, after the gas obtained by the primary osmosis treatment is condensed, the tail gas containing 0.1~2wt% N-methylpyrrolidone is extracted and transported to the absorption unit for treatment and then discharged; and / or, the tail gas containing 0.01~1wt% N-methylpyrrolidone in the gas obtained by the secondary osmosis treatment is extracted and transported to the absorption unit for treatment and then discharged.

[0053] It is understood that deep dehydration of molecular sieve membrane modules involves primary and secondary osmosis processes. The gas obtained from the primary osmosis treatment, due to its high water content and large gas volume, is condensed in a condenser. The treated condensate is then transported to the absorbent circulation inlet of the absorption unit, which can improve the reuse rate of the material. The gas from the secondary osmosis treatment, due to its low water content and small gas volume, is directly returned to the gas phase inlet of the absorption unit for absorption treatment. The two complement each other, eliminating the discharge of osmotic wastewater and vacuum tail gas, achieving self-circulation and zero-pollution emission treatment in the process.

[0054] According to the third aspect of the present application, a method for recovering and treating waste gas containing N-methylpyrrolidone is provided. The waste gas recovery and treatment method is completed using the "a waste gas recovery and treatment device containing N-methylpyrrolidone" provided in the first aspect of the present application as above, and the waste gas recovery and treatment method is completed according to the steps described in the "a waste gas recovery and treatment method containing N-methylpyrrolidone" provided in the second aspect of the present application as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present application is further described below with reference to the accompanying drawings and embodiments, wherein:

[0056] FIG1 is a schematic diagram of a waste gas recovery and treatment device containing N-methylpyrrolidone in one embodiment of the present application.

[0057] Reference numerals:

[0058] First heat exchange equipment 1, second heat exchange equipment 2, first phase separation device 3, fourth material conveying equipment 4, absorption tower 5, second material conveying equipment 6, first condensing equipment 7, first material buffer equipment 8, third material conveying equipment 9, filtering equipment 10, heat exchange device 11, second cooling equipment 12, second material buffer equipment 13, fifth material conveying equipment 14, first heating equipment 15, molecular sieve membrane assembly 16, first vacuum unit 17-1, second vacuum unit 17-2, third cooling equipment 18, third material buffer equipment 19, fifth material conveying equipment 20, first material conveying equipment 21. DETAILED DESCRIPTION

[0059] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following will clearly and completely describe the concept of the present application and the technical effects produced in conjunction with the embodiments to fully understand the purposes, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without paying creative work are all within the scope of protection of this application.

[0060] In this specification, the terms "connect," "install," and "fix" should be understood broadly. For example, "connect" can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a direct connection or an indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0061] In the description of this application, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples.

[0062] The embodiment of the present application will be further described and illustrated below with reference to FIG1 .

[0063] According to one embodiment of the present application, a waste gas recovery and treatment device containing N-methylpyrrolidone is provided, comprising an absorption unit and a molecular sieve membrane dehydration unit. The waste gas recovery and treatment device containing N-methylpyrrolidone of the present application utilizes a combination of an absorption unit and a molecular sieve membrane dehydration unit, which can ensure continuous and stable operation of the system. Furthermore, the recovery and treatment device of the present application can reduce operating costs and equipment investment costs. Compared to conventional membrane dehydration devices, the present application eliminates the permeate vapor condenser, thus avoiding the problem of requiring secondary treatment of the permeate condensate waste liquid in conventional membrane dehydration devices.

[0064] In the waste gas recovery and treatment device containing N-methylpyrrolidone of the present application, the absorption unit includes a heat exchange device, a first phase separation device 3, and an absorption device, wherein the heat exchange device, the first phase separation device 3 and the absorption device are connected in sequence; the molecular sieve membrane dehydration unit is connected to the absorption unit, and the molecular sieve membrane dehydration unit includes a filtering device 10, a heat exchange device 11, a first heating device 15, and a molecular sieve membrane assembly 16, wherein the filtering device 10, the heat exchange device 11, the first heating device 15, and the molecular sieve membrane assembly 16 are connected in sequence.

[0065] The waste gas recovery and treatment device containing N-methylpyrrolidone of the present application achieves the effect of condensing the waste gas through the heat exchange equipment in the above composition, and combines the absorption equipment and the molecular sieve membrane dehydration unit. Through the condensation-absorption-molecular sieve membrane dehydration technology, the N-methylpyrrolidone content in the gas phase after absorption can reach 20mg / m 3 The following has the advantages of meeting tail gas emission standards and fully recovering and utilizing heat.

[0066] It is understood that the heat exchange equipment of the present application may include a first heat exchange device 1 and a second heat exchange device 2. By using different processing temperatures of the two heat exchange devices, the waste gas containing N-methylpyrrolidone can be subjected to different degrees of heat exchange treatment. For example, the processing temperature of the first heat exchange device 1 is 80-120°C, and the processing temperature of the second heat exchange device 2 is 10-40°C.

[0067] According to one embodiment of the present application, the absorption device comprises a bottom portion, a middle portion, and a top portion. The bottom portion has an exhaust gas inlet on one side and an absorption rich liquid outlet on the other side, while the middle portion has an absorbent circulation inlet, and the top portion has an absorbent inlet on one side and an exhaust gas outlet on the other side.

[0068] It is understood that the absorption device of the present application can provide different functions by providing different inlets and / or outlets at its bottom, middle, and top. For example, by providing an exhaust gas inlet on one side of the bottom of the absorption device, exhaust gas generated by other parts of the exhaust gas recovery and treatment device can be passed into the absorption device for circulation and absorption, thereby achieving continuous treatment of the exhaust gas, improving the purity of the recovered product, and reducing the formation of secondary pollution. In addition, by providing an absorbent circulation inlet in the middle, the absorbent can be recycled during the recovery process, and the heat can also be fully utilized, significantly improving resource utilization.

[0069] According to one embodiment of the present application, the absorption equipment includes an absorption tower 5 , wherein one end of the absorption tower 5 is connected to the first phase separation device 3 .

[0070] In the absorption apparatus of the present application, one end of the absorption tower 5 is connected to the first phase separation device 3, so that part of the material separated by the first phase separation device 3 can be fed into the absorption tower 5. It is understood that the material separated by the first phase separation device 3 can be fed into the absorption tower 5 via a fourth material conveying device 4. In some embodiments, the fourth material conveying device 4 can be a fan.

[0071] In addition, the waste gas recovery and treatment device also includes a first condensing device 7, which is connected to the other end of the absorption tower 5 and is used to condense the material transported out of the other end of the absorption tower 5 and return it to the absorption tower 5.

[0072] In the present application, a first condensing device 7 is provided in the waste gas recovery and treatment device, which can condense the material transported from the other end of the absorption tower 5 and return it to the absorption tower 5. This connection method is conducive to the recycling absorption treatment of the material treated by the absorption tower 5, thereby improving the utilization rate of resources.

[0073] According to an embodiment of the present application, the absorption unit further includes a first material conveying device 21, one end of which is connected to the first phase separation device 3. It is understandable that the first material conveying device 21 can be a pump.

[0074] Furthermore, the first phase separation device 3 includes a first gas-phase outlet and a second liquid-phase outlet. The first gas-phase outlet is connected to the exhaust gas inlet, while the first liquid-phase outlet is connected to the first material conveying device 21. Specifically, the first material conveying device 21 discharges the liquid-phase material produced in the first phase separation device 3 for use by other processing components in the recovery and treatment device. Furthermore, the gaseous material produced by the first phase separation device 3 enters the exhaust gas inlet at the bottom of the absorption device, facilitating absorption processing within the absorption device.

[0075] According to one embodiment of the present application, the exhaust gas outlet is connected to the heat exchange medium inlet of the heat exchange device. It should be noted that an exhaust gas outlet is provided on the other side of the top of the absorption device. After the exhaust gas treated by the absorption device flows out of this outlet, it can be returned to the heat exchange medium inlet of the heat exchange device, achieving continuous exhaust gas treatment and fully and effectively utilizing the heat.

[0076] Furthermore, the rich absorption liquid outlet located on the other side of the bottom of the absorption apparatus is connected to a second material conveying device 6, which is in turn connected to the absorbent circulation inlet. This means that the rich absorption liquid flowing from the bottom of the absorption apparatus, after being conveyed by the second material conveying device 6, is returned to the absorbent circulation inlet located in the middle of the absorption apparatus. This improves the reuse rate of the rich absorption liquid and significantly enhances the purity of the recovered product. It is understood that the second material conveying device 6 includes, but is not limited to, a pump.

[0077] According to one embodiment of the present application, a material liquid phase inlet is provided on one side of the molecular sieve membrane assembly 16, and a material liquid phase outlet and a vacuum port are provided on the other side. The material liquid phase inlet is connected to the first heating device 15, and the material liquid phase outlet is connected to the heat exchange medium inlet of the heat exchange device 11.

[0078] It is understood that when the material treated by the absorption unit enters the molecular sieve membrane dehydration unit, it must first be heated by the first heating device 15, and the heating temperature can be selected to be 100-140°C. The liquid phase material treated by the molecular sieve membrane assembly 16 can first be heat exchanged by the heat exchange device 11 for subsequent use.

[0079] According to an embodiment of the present application, the molecular sieve membrane dehydration unit further includes a second cooling device 12 connected to the heat exchange medium outlet of the heat exchange device 11 .

[0080] It is understandable that a second cooling device 12 is provided in the molecular sieve membrane dehydration unit and connected to the heat exchange medium outlet of the heat exchange device 11, so that the liquid phase material treated by the heat exchange device 11 can be further cooled to achieve a material suitable for temporary storage for future use.

[0081] It should be noted that the second cooling device 12 can also be connected to the second material buffer device 13 to temporarily store the material cooled to 25-50°C for future use. In addition, the material temporarily stored in the second material buffer device 13 can be delivered as N-methylpyrrolidone product via the fifth material conveying device 14.

[0082] According to an embodiment of the present application, the molecular sieve membrane dehydration unit further includes a third cooling device 18. The third cooling device 18 includes a gas phase inlet and a gas phase outlet, and the gas phase inlet is connected to a portion of the vacuum port in the molecular sieve membrane assembly 16.

[0083] In addition, it should be noted that molecular sieve membrane assembly 16 comprises a plurality of components operated in series, for example, can comprise four series assemblies, are respectively expressed as 16-1,16-2,16-3,16-4.Wherein, 16-1 and 16-2 carry out one-level osmotic dehydration, 16-3 and 16-4 carry out two-level osmotic dehydration.One-level osmotic dehydration belongs to preliminary dehydration, and is dehydrated to a water content of about 1wt%, and two-level osmotic dehydration belongs to deep dehydration, and is dehydrated to a water content of about 0.1wt%.Wherein, the gas phase inlet of the 3rd cooling device 18 in this application is connected with the components 16-1 and 16-2 that carry out one-level osmotic dehydration, for cooling the gas processed by one-level osmotic dehydration.

[0084] According to one embodiment of the present application, the molecular sieve membrane dehydration unit also includes a first vacuum unit 17-1 and a second vacuum unit 17-2, wherein the first vacuum unit 17-1 is connected to the gas phase outlet of the third cooling device 18; the second vacuum unit 17-2 has an inlet, which is connected to another part of the vacuum port in the molecular sieve membrane assembly 16.

[0085] According to one embodiment of the present application, the outlet of the first vacuum unit 17 - 1 and the outlet of the second vacuum unit 17 - 2 are respectively connected to the exhaust gas inlet at the bottom of the absorption device.

[0086] It is understood that the material processed by the first vacuum unit 17-1 and the second vacuum unit 17-2 is returned to the exhaust gas inlet at the bottom of the absorption device. In other words, the present application directly connects the exhaust gas generated by the vacuum units to the absorption device for recovery and treatment. This allows the exhaust gas containing 0.1-2 wt% N-methylpyrrolidone separated by the molecular sieve membrane assembly 16 to be processed by the absorption device. The water generated throughout the entire process can be discharged from the top of the absorption device in the form of saturated water, achieving zero pollution emissions throughout the entire recovery process.

[0087] It can be understood that the condensate condensed by the third cooling device 18 can be transported to the third material buffer device 19 and further transported to the absorbent circulation inlet set in the middle of the absorption tower 5 through the fifth material conveying device 20.

[0088] According to one embodiment of the present application, a first material cache device 8 is further provided between the absorption unit and the molecular sieve membrane dehydration unit, wherein the molecular sieve membrane dehydration unit further includes a third material conveying device 9, the inlet of the third material conveying device 9 is connected to the first material cache device 8, and the outlet is connected to the filtration device 10.

[0089] The material processed by the absorption unit is intermediately stored by the first material buffer device 8 , and is transported to the filtering device 10 by the third material conveying device 9 for filtering, and then processed by the heat exchange device 11 .

[0090] It can be understood that the N-methylpyrrolidone-containing waste gas recovery and treatment device according to the embodiment of the present application can ensure the continuous and stable operation of the system. With this set of treatment devices, the absorption rich liquid concentration can be concentrated to more than 92%, which greatly reduces the energy consumption of the membrane dehydration process and the number of membrane components, and reduces the operating cost and equipment investment cost. Compared with the traditional membrane dehydration device, the present application deletes the permeate vapor condenser, avoiding the problem of secondary treatment of the permeate condensation waste liquid in the traditional membrane dehydration device. In addition, the recovery and treatment device of the present application can realize the continuous treatment of waste gas, and the heat is fully utilized, and the resource utilization rate is high. The N-methylpyrrolidone content in the gas phase after absorption can reach 20mg / m 3 The following advantages are achieved: tail gas emission meets standards and heat recovery is fully utilized. Furthermore, the waste gas recovery and treatment device of the present application has the characteristics of high purity of the recovered product, with the obtained N-methylpyrrolidone content exceeding 99.99%, meeting electronic grade standards, and no secondary pollution is generated. The operating conditions and process technology are highly controllable, and are suitable for the N-methylpyrrolidone recovery process in the battery coating industry, such as lithium batteries.

[0091] According to an embodiment of the present application, the waste gas recovery and treatment method specifically includes the following steps:

[0092] Waste gas containing 0.001-2 wt% N-methylpyrrolidone (NMP) undergoes two heat exchange treatments in a heat exchanger, the first at 80°C and the second at 40°C. The waste gas then enters a phase separation unit for separation, and the condensate is collected and transported for future use. Water is added as the absorbent through the absorbent inlet on the top side of the absorption unit, at room temperature, and subjected to countercurrent absorption. The non-condensable gas phase obtained from phase separation is then transported to the absorption unit for absorption treatment. After absorption, liquid and gas phases are obtained. 75% of the rich liquid in the liquid phase is returned to the middle section of the absorption unit for recycling, while 25% is buffered for future use. This buffered rich liquid (containing 96 wt% NMP) is pressurized and transported to produce the treated liquid. The gas phase also enters the heat exchanger as a heat exchange medium.

[0093] The treated liquid is heated to 100°C and then passed into a molecular sieve membrane dehydration unit for dehydration. Multiple molecular sieve membrane modules are operated in series, encompassing both primary and secondary osmosis. The operating pressure for the molecular sieve membrane dehydration is 0.3 MPa.A, with the primary osmosis side operating at a pressure below 2 kPaA and the secondary osmosis side operating at a pressure of 0.7 kPaA. The gas obtained from the primary osmosis process is condensed and then transferred to the absorbent recirculation inlet of the absorption unit. Furthermore, the gas obtained from the secondary osmosis process is directly returned to the absorption unit. The exhaust gas containing 0.1-2 wt% NMP extracted by the first vacuum unit and 0.01-1 wt% NMP extracted by the second vacuum unit are directly returned to the exhaust gas inlet located on one side of the absorption unit for treatment in the absorption unit before meeting emission standards. The material (electronic-grade N-methylpyrrolidone) discharged from the liquid phase outlet on the first side of the molecular sieve membrane module is cooled to 50°C in a second cooling device before being stored in a buffer for future use. The material discharged from the liquid phase outlet on the second side of the molecular sieve membrane assembly enters another heat exchange device for use as a heat exchange medium. The material discharged from the liquid phase outlet contains about 1 wt% NMP and about 99 wt% water.

[0094] In this embodiment, a method for recovering and treating N-methylpyrrolidone-containing waste gas is provided, which adopts condensation-absorption-molecular sieve membrane dehydration technology. The waste gas containing N-methylpyrrolidone is cooled by multi-stage condensation to recover part of the N-methylpyrrolidone. The energy in the high-temperature waste gas is fully utilized for the "whitening" treatment of the exhaust gas from the absorption unit. The N-methylpyrrolidone in the waste gas is transferred from the gas phase to the liquid phase by absorption, and is deeply dehydrated and purified by a molecular sieve membrane assembly to finally obtain an electronic grade N-methylpyrrolidone product.

[0095] According to another embodiment of the present application, a waste gas recovery and treatment method specifically includes the following steps:

[0096] Waste gas containing 0.001-2 wt% N-methylpyrrolidone (NMP) undergoes two heat exchange treatments in a heat exchanger, the first at 120°C and the second at 40°C. The waste gas then enters a phase separation unit for separation, and the condensate is collected and transported for future use. Water is added as the absorbent through the absorbent inlet on the top side of the absorption unit, fed at room temperature and subjected to countercurrent absorption. The non-condensable gas phase obtained from phase separation is then transported to the absorption unit for absorption treatment. After absorption, liquid and gas phases are obtained. 75% of the rich liquid in the liquid phase is returned to the middle section of the absorption unit for recycling, while the remaining 25% is buffered for future use. This buffered rich liquid (containing 94 wt% NMP) is pressurized and transported to produce the treated liquid. The gas phase also enters the heat exchanger as a heat exchange medium.

[0097] The treated liquid is heated to 110°C and then passed into a molecular sieve membrane dehydration unit for dehydration. Multiple molecular sieve membrane modules are operated in series, encompassing both primary and secondary osmosis. The operating pressure for the molecular sieve membrane dehydration is 0.4 MPa.A, with the primary osmosis side operating at a pressure below 3 kPaA and the secondary osmosis side operating at a pressure of 0.5 kPaA. The gas obtained from the primary osmosis process is condensed and then transferred to the absorbent recirculation inlet of the absorption unit. Furthermore, the gas obtained from the secondary osmosis process is directly returned to the absorption unit. The exhaust gas containing 0.1-2 wt% NMP extracted by the first vacuum unit and 0.01-1 wt% NMP extracted by the second vacuum unit are directly returned to the exhaust gas inlet located on one side of the absorption unit for treatment in the absorption unit and subsequent discharge to meet emission standards. The material (electronic-grade N-methylpyrrolidone) discharged from the liquid phase outlet on the first side of the molecular sieve membrane module is cooled to 40°C in a second cooling device before being stored in a buffer for future use. The material discharged from the liquid phase outlet on the second side of the molecular sieve membrane assembly enters another heat exchange device for use as a heat exchange medium. The material discharged from the liquid phase outlet contains about 1 wt% NMP and about 99 wt% water.

[0098] According to another embodiment of the present application, the waste gas recovery and treatment method specifically includes the following steps:

[0099] Waste gas containing 0.001-2 wt% N-methylpyrrolidone (NMP) undergoes two heat exchange treatments in a heat exchanger, the first at 100°C and the second at 40°C. The waste gas then enters a phase separation unit for separation, and the condensate is collected and transported for future use. Water is added as the absorbent through the absorbent inlet on the top side of the absorption unit, at room temperature, and subjected to countercurrent absorption. The non-condensable gas phase obtained after phase separation is then transported to the absorption unit for absorption treatment. After absorption, liquid and gas phases are obtained. 75% of the rich liquid in the liquid phase is returned to the middle section of the absorption unit for recycling, while the remaining 25% is buffered for future use. This buffered rich liquid (containing 95 wt% NMP) is pressurized and transported to produce the treated liquid. The gas phase also enters the heat exchanger as a heat exchange medium.

[0100] The treated liquid is heated to 115°C and then passed into a molecular sieve membrane dehydration unit for dehydration. Multiple molecular sieve membrane modules are operated in series, encompassing both primary and secondary osmosis. The operating pressure for the molecular sieve membrane dehydration is 0.5 MPa.A, with the primary permeation side operating at a pressure below 2 kPaA and the secondary permeation side operating at a pressure of 0.3 kPaA. The gas obtained from the primary permeation process is condensed and then transferred to the absorbent recirculation inlet of the absorption unit. Furthermore, the gas obtained from the secondary permeation process is directly returned to the absorption unit. The exhaust gas containing 0.1-2 wt% NMP extracted by the first vacuum unit and 0.01-1 wt% NMP extracted by the second vacuum unit are directly returned to the exhaust gas inlet located on one side of the absorption unit for treatment in the absorption unit and subsequent discharge to meet emission standards. The material (electronic-grade N-methylpyrrolidone) discharged from the liquid phase outlet on the first side of the molecular sieve membrane module is cooled to 45°C in a second cooling device before being stored in a buffer for future use. The material discharged from the liquid phase outlet on the second side of the molecular sieve membrane assembly enters another heat exchange device for use as a heat exchange medium. The material discharged from the liquid phase outlet contains about 1 wt% NMP and about 99 wt% water.

[0101] According to another embodiment of the present application, the waste gas recovery and treatment method specifically includes the following steps:

[0102] Waste gas containing 0.001-2 wt% N-methylpyrrolidone (NMP) undergoes two heat exchange treatments in a heat exchanger, the first at 90°C and the second at 40°C. The waste gas then enters a phase separation unit for separation, and the condensate is collected and transported for future use. Water is added as the absorbent through the absorbent inlet on the top side of the absorption unit, at room temperature, and subjected to countercurrent absorption. The non-condensable gas phase obtained from phase separation is then transported to the absorption unit for absorption treatment. After absorption, liquid and gas phases are obtained. 75% of the rich liquid in the liquid phase is returned to the middle section of the absorption unit for recycling, while 25% is buffered for future use. This buffered rich liquid (containing 92 wt% NMP) is pressurized and transported to produce the treated liquid. The gas phase also enters the heat exchanger as a heat exchange medium.

[0103] The treated liquid is heated to 120°C and then passed into a molecular sieve membrane dehydration unit for dehydration. Multiple molecular sieve membrane modules are operated in series, encompassing both primary and secondary osmosis. The operating pressure for the molecular sieve membrane dehydration is 0.5 MPa.A, with the primary osmosis side operating at a pressure below 1 kPaA and the secondary osmosis side operating at a pressure of 0.2 kPaA. The gas obtained from the primary osmosis process is condensed and then transferred to the absorbent recirculation inlet of the absorption unit. Furthermore, the gas obtained from the secondary osmosis process is directly returned to the absorption unit. The exhaust gas containing 0.1-2 wt% NMP extracted by the first vacuum unit and 0.01-1 wt% NMP extracted by the second vacuum unit are directly returned to the exhaust gas inlet located on one side of the absorption unit for treatment in the absorption unit and subsequent discharge to meet emission standards. The material (electronic-grade N-methylpyrrolidone) discharged from the liquid phase outlet on the first side of the molecular sieve membrane module is cooled to 45°C in a second cooling device before being stored in a buffer for future use. The material discharged from the liquid phase outlet on the second side of the molecular sieve membrane assembly enters another heat exchange device for use as a heat exchange medium. The material discharged from the liquid phase outlet contains about 1 wt% NMP and about 99 wt% water.

[0104] The embodiments of the present application have been described in detail above in conjunction with specific implementation methods. However, the present application is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other unless there is a conflict.

Claims

1. A waste gas recovery and treatment device containing N-methylpyrrolidone, characterized in that: The waste gas recovery and treatment device comprises: An absorption unit, comprising a heat exchange device, a first phase separation device (3), and an absorption device, wherein the heat exchange device, the first phase separation device (3), and the absorption device are connected in sequence; A molecular sieve membrane dehydration unit is connected to the absorption unit, the molecular sieve membrane dehydration unit comprising a filtering device (10), a heat exchange device (11), a first heating device (15), and a molecular sieve membrane assembly (16), wherein the filtering device (10), the heat exchange device (11), the first heating device (15), and the molecular sieve membrane assembly (16) are connected in sequence.

2. The waste gas recovery and treatment device according to claim 1, characterized in that: The absorption device comprises: A bottom portion, wherein one side of the bottom portion is provided with an exhaust gas inlet, and the other side of the bottom portion is provided with an absorption rich liquid outlet; In the middle, an absorbent circulation inlet is provided; A top portion is provided with an absorbent inlet on one side and an exhaust gas outlet on the other side.

3. The waste gas recovery and treatment device according to claim 1, characterized in that: The absorption equipment comprises: an absorption tower (5), one end of which is connected to the first phase separation device (3); The waste gas recovery and treatment device further comprises a first condensing device (7) connected to the other end of the absorption tower (5) and used for condensing the material transported out of the other end of the absorption tower (5) and returning it to the absorption tower (5).

4. The waste gas recovery and treatment device according to claim 2, characterized in that: The absorption unit further comprises a first material conveying device (21), one end of which is connected to the first phase separation device (3); The first phase separation device (3) comprises: a first gas phase outlet connected to the exhaust gas inlet; The first liquid phase outlet is connected to the first material conveying device (21).

5. The waste gas recovery and treatment device according to claim 2, characterized in that: The exhaust gas outlet is connected to the heat exchange medium inlet of the heat exchange device; The absorption rich liquid outlet is connected to a second material conveying device (6), and one end of the second material conveying device (6) is connected to the absorbent circulation inlet.

6. The waste gas recovery and treatment device according to claim 2, characterized in that: The molecular sieve membrane assembly (16) is provided with a material liquid phase inlet on one side and a material liquid phase outlet and a vacuum port on the other side. The material liquid phase inlet is connected to the first heating device (15), and the material liquid phase outlet is connected to the heat exchange medium inlet of the heat exchange device (11).

7. The waste gas recovery and treatment device according to claim 6, characterized in that: The molecular sieve membrane dehydration unit also includes: A third cooling device (18) comprises a gas phase inlet and a gas phase outlet, wherein the gas phase inlet is connected to a portion of a vacuum port in the molecular sieve membrane assembly (16); A first vacuum unit (17-1) connected to a gas phase outlet of the third cooling device (18); The second vacuum unit (17-2) has an inlet, which is connected to another vacuum port in the molecular sieve membrane assembly (16).

8. The waste gas recovery and treatment device according to claim 7, characterized in that: The outlet of the first vacuum unit (17-1) and the outlet of the second vacuum unit (17-2) are respectively connected to the waste gas inlet at the bottom of the absorption device.

9. A method for recovering and treating waste gas containing N-methylpyrrolidone, characterized in that: The waste gas recovery and treatment method comprises the following steps: The waste gas containing a certain amount of N-methylpyrrolidone is treated by an absorption unit to obtain a treatment liquid; The treated liquid is dehydrated by a molecular sieve membrane dehydration unit to obtain electronic grade N-methylpyrrolidone and tail gas, wherein the tail gas is transported to the absorption unit for treatment and then discharged, and the electronic grade N-methylpyrrolidone is cooled for standby use.

10. The waste gas recovery and treatment method according to claim 9, characterized in that: The waste gas containing a certain amount of N-methylpyrrolidone is treated by an absorption unit, comprising the following steps: The exhaust gas is firstly subjected to heat exchange treatment by a heat exchange device, and then subjected to phase separation by a first phase separation device, and the condensate after the phase separation is collected for standby use; The non-condensable gas phase material obtained by the phase separation is transported to an absorption device for absorption treatment, and after the absorption treatment, a liquid phase material and a gas phase material are obtained, wherein 75-95% of the rich liquid in the liquid phase material is returned to the middle part of the absorption device for treatment and circulation, and 5-25% of the rich liquid is cached for standby use, and the cached rich liquid is pressurized to obtain the treated liquid; The gas phase substance enters the heat exchange device as a heat exchange medium.

11. The waste gas recovery and treatment method according to claim 9, characterized in that: After obtaining the treatment liquid, the following process is also included: The treated liquid is heated to 100-140° C. and then enters the molecular sieve membrane dehydration unit for dehydration treatment.

12. The waste gas recovery and treatment method according to claim 10, characterized in that: The heat exchange treatment includes two heat exchange processes, wherein the first heat exchange process is carried out at 80-120°C, and the second heat exchange process is carried out at 10-40°C.

13. The waste gas recovery and treatment method according to any one of claims 9 to 12, characterized in that: The dehydration operation process includes the following steps: The treated liquid is treated in series operation in multiple molecular sieve membrane modules, and the series operation includes primary osmosis and secondary osmosis, wherein the gas obtained from the primary osmosis treatment is condensed, and then the condensate after the condensation treatment is transported to the absorbent circulation inlet of the absorption unit, and the gas obtained from the secondary osmosis treatment is directly returned to the absorption unit.

14. The waste gas recovery and treatment method according to claim 13, characterized in that: The operating pressure of the primary osmosis is 0.1-3 kPaA, and the operating pressure of the secondary osmosis is 0.1-5 kPaA.

15. The waste gas recovery and treatment method according to claim 13, characterized in that: After the gas obtained from the primary osmosis treatment is condensed, the tail gas containing 0.1~2wt% N-methylpyrrolidone is extracted and transported to the absorption unit for treatment and then discharged; and / or, the tail gas containing 0.01~1wt% N-methylpyrrolidone in the gas obtained from the secondary osmosis treatment is extracted and transported to the absorption unit for treatment and then discharged.

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