White oil refining system and method for recovering lithium battery diaphragm extract liquor

Abstract

The invention discloses a white oil refining system and a white oil refining method for recovering lithium battery diaphragm extract liquor. The system comprises a kettle type reboiler, a tower top condenser, a vacuum buffer tank, a water ring vacuum pump, a gas-liquid separation tank, an oil separation tank and an aeration tank. A kettle type reboiler is used for heating crude white oil, a water ring vacuum pump is used for reducing the internal pressure of the kettle type reboiler, nitrogen is distributed into the crude white oil, vacuum rectification and nitrogen gas are carried out, and the crude white oil is separated into refined white oil and tail gas. And condensing the tail gas by using a tower top condenser, and separating the tail gas into condensate and non-condensable gas. A water ring vacuum pump is utilized to divide a white oil component into small liquid drops to be mixed in a working solution, and the white oil component in non-condensable gas is separated from gas-phase components of dichloromethane and nitrogen. According to the method, a vacuum rectification and nitrogen gas stripping combined process is adopted, the crude white oil is rectified into the refined white oil, and the separated dichloromethane tail gas is treated and then is merged into a factory gas-phase VOC recovery device, so that the requirement of up-to-standard emission is met.

Description

Technical Field

[0001] The invention relates to a white oil refining system for recovering lithium battery diaphragm extract, and also relates to a refining method based on the white oil refining system, belonging to the technical field of extraction recovery. Background Art

[0002] The extract produced by the lithium battery wet-process diaphragm production line contains dichloromethane and white oil, which are usually separated and recovered by evaporation or distillation. In the recovery process, dichloromethane is recycled through evaporation, gas-liquid separation, condensation and water separation. However, after preliminary treatment, the crude white oil in the bottom concentrate still has trace amounts of dichloromethane, which needs to be further refined.

[0003] In the Chinese patent application with application number 202010599217.4, a separation device for a mixture of dichloromethane and white oil is disclosed. The device includes a distillation system, a white oil treatment system and a dichloromethane treatment system. The distillation system consists of a distillation tower, an evaporator and a gas-liquid separator for preliminary separation of dichloromethane and white oil; the white oil treatment system includes an oil rectifier, a white oil cooler and a white oil collector for further purification of white oil; the dichloromethane treatment system includes a condenser, a water separator and a collector for recovering dichloromethane.

[0004] However, in the process of refining crude white oil, a certain proportion of white oil is mixed in the volatilized dichloromethane. When these mixed gases enter the VOC recovery device, the white oil will block the adsorption pores, thereby hindering the adsorption efficiency and regeneration effect of the adsorption unit. Summary of the invention

[0005] The primary technical problem to be solved by the present invention is to provide a white oil refining system for recycling lithium battery diaphragm extract.

[0006] Another technical problem to be solved by the present invention is to provide a purification method for recovering lithium battery diaphragm extract.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: According to a first aspect of an embodiment of the present invention, a white oil refining system for recycling lithium battery diaphragm extract is provided, comprising a kettle reboiler, a tower top condenser, a vacuum buffer tank, a water ring vacuum pump, a gas-liquid separation tank, an oil separator and an aeration tank; wherein: The feed port of the kettle reboiler is connected to the upstream pipeline, the gas phase discharge port is connected to the feed port of the tower top condenser, the liquid phase discharge port is connected to the downstream pipeline, the gas distributor is connected to the upstream pipeline, and the tower top reflux port is connected to the liquid phase discharge port of the tower top condenser; The gas phase discharge port of the tower top condenser is connected to the feed port of the vacuum buffer tank; the discharge port of the vacuum buffer tank is connected to the air intake port of the water ring vacuum pump; the output port of the water ring vacuum pump is connected to the feed port of the gas-liquid separation tank, and the water supply port is connected to the liquid phase discharge port of the aeration tank and the upstream water supply pipeline; The gas phase outlet of the gas-liquid separation tank is connected to the downstream VOC adsorption device, and the liquid phase outlet is connected to the feed port of the oil separator tank; the outlet of the oil separator tank is connected to the feed port of the aeration tank; the gas phase outlet of the aeration tank is connected to the downstream VOC adsorption device.

[0008] Preferably, a top pressure sensor is provided at the top of the kettle reboiler; the controller of the water ring vacuum pump is connected to the top pressure sensor, and the operating speed of the water ring vacuum pump is controlled according to the measurement data of the top pressure sensor to maintain the internal air pressure of the kettle reboiler and the gas output of the gas phase discharge port.

[0009] Preferably, the white oil refining system further comprises a separation tank condenser and an expansion pipe; wherein, The feed port of the separation tank condenser is connected to the gas phase discharge port of the gas-liquid separation tank, and the discharge port is connected to the feed port of the expansion pipe; the gas phase discharge port of the expansion pipe is connected to the downstream VOC adsorption device, and the liquid phase discharge port is connected to the downstream condensate recovery pipeline.

[0010] Preferably, the white oil refining system further comprises a water ring pump condenser; wherein, The feed inlet of the water ring pump condenser is connected to the liquid phase discharge port of the aeration tank, and the discharge port is connected to the water replenishment port of the water ring vacuum pump.

[0011] According to a second aspect of an embodiment of the present invention, a purification method for recovering a lithium battery diaphragm extract is provided, comprising the following steps: Step S1: heating the crude white oil to a designed temperature by using a kettle reboiler, reducing the internal pressure of the kettle reboiler to the designed pressure by using a water ring vacuum pump, and distributing nitrogen into the crude white oil by using a gas distributor of the kettle reboiler to perform vacuum distillation and nitrogen gas on the crude white oil, so as to separate the crude white oil into refined white oil and tail gas; Step S2: condensing the tail gas to a designed temperature using the tower top condenser to separate the tail gas into condensate and non-condensable gas; Step S3: using the vacuum buffer tank to reduce the pressure fluctuation of the kettle reboiler and the tower top condenser; Step S4: using the water ring vacuum pump to provide power for the gas phase materials in the kettle reboiler, the tower top condenser and the vacuum buffer tank, so that they move in the pipelines and equipment; and using the water ring vacuum pump to mix the white oil component into small droplets in the working fluid, and to separate the white oil component in the non-condensable gas from the gas phase components of dichloromethane and nitrogen to form a mixed gas-liquid; Step S5: using the gas-liquid separation tank to separate the mixed gas and liquid into a mixed gas and a mixed liquid, and using downstream equipment to recover and process the mixed gas; Step S6: using the oil separator to separate the white oil component in the mixed liquid to obtain an oil separator liquid; Step S7: using the aeration tank to heat and aerate the oil separator liquid, separating the gas phase dichloromethane to form aeration gas and aeration liquid; using downstream equipment to recover and process the aeration gas; using the aeration liquid as a working fluid and providing it to the water ring vacuum pump.

[0012] Preferably, the rotation speed of the water ring vacuum pump is controlled by using the controller of the water ring vacuum pump according to the detection data of the top pressure sensor inside the kettle reboiler.

[0013] Preferably, the heating temperature of the crude white oil in the kettle reboiler is not less than 140°C; and the temperature of the nitrogen gas input into the kettle reboiler is not less than 140°C.

[0014] Preferably, the mixed gas is cooled to the design temperature by using a separation tank condenser, the mixed gas is separated into separated non-condensable gas and separated condensate by using an expansion pipe, and the separated non-condensable gas and separated condensate are respectively recovered by downstream equipment.

[0015] Preferably, the aeration liquid is cooled to a design temperature by a water ring pump condenser and then provided to the water ring vacuum pump as a working fluid.

[0016] Compared with the prior art, the present invention effectively solves the problem of high residual methylene chloride in the prior art through a combined process of vacuum distillation and nitrogen stripping. The white oil refining system adopts equipment such as kettle reboiler, tower top condenser, vacuum buffer tank, water ring vacuum pump, gas-liquid separation tank, oil separator and aeration tank to achieve efficient refining of crude white oil, so that the mass concentration of methylene chloride in refined white oil is not higher than 30ppm, meeting the reuse demand of the workshop. At the same time, the non-condensable gas tail gas at the top of the tower is incorporated into the gas phase VOC recovery device in the plant area after treatment, and the methylene chloride is further recovered and discharged in compliance with the standards, effectively reducing environmental pollution. In addition, the use of the water ring vacuum pump not only improves the vacuum degree of the system, but also breaks up the white oil into small droplets through its high shear force impeller, which is convenient for subsequent separation and recovery, and prolongs the service life of the VOC adsorption device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1The present invention is a schematic structural diagram of a white oil refining system for recovering lithium battery diaphragm extract in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The technical concept in the embodiment of the present invention is to separate dichloromethane from crude white oil by utilizing the huge difference in relative volatility between dichloromethane and white oil under reduced pressure conditions. Nitrogen stripping utilizes the inertness and stability of nitrogen to effectively carry and separate dichloromethane from crude white oil by adjusting temperature, pressure and flow rate. In this process, nitrogen not only acts as a carrier, but also plays a role in protecting and preventing oxidation and discoloration of white oil.

[0020] The first embodiment of the present invention provides a white oil refining system for recycling lithium battery diaphragm extract, comprising a kettle reboiler 1, a tower top condenser 2, a vacuum buffer tank 3, a water ring vacuum pump 4, a gas-liquid separation tank 5, an oil separator 6 and an aeration tank 7. The kettle reboiler 1 has been disclosed in the patent ZL 202321891481.0 that the applicant has been granted, and will not be described in detail here. like Figure 1 As shown, the kettle reboiler 1 is a refining device for refining crude white oil into refined white oil, including heating and nitrogen stripping equipment. The feed port 11 (liquid distributor) of the kettle reboiler 1 is connected to the upstream pipeline for inputting crude white oil. The gas phase discharge port 12 is connected to the feed port 21 of the tower top condenser 2 for discharging the tail gas obtained by distilling the crude white oil. The liquid phase discharge port 13 is connected to the downstream pipeline for discharging the refined white oil obtained by distilling the crude white oil. The gas distributor 14 is connected to the upstream pipeline for inputting nitrogen into the kettle reboiler 1 to strip the crude white oil. The tower top reflux port 15 is connected to the liquid phase discharge port 23 of the tower top condenser 2 for providing tower top reflux. A top pressure sensor 16 is provided at the top of the kettle reboiler 1. The heat exchange tube bundle 17 of the kettle reboiler 1 is connected to the external steam pipeline for providing heat energy for distilling the crude white oil.

[0021] The top condenser 2 is a gas condensing device, including a cooling pipeline and a material pipeline. The feed port 21 of the top condenser 2 is connected to the gas phase discharge port 12 of the kettle reboiler 1, the liquid phase discharge port 23 is connected to the top reflux port 15 of the kettle reboiler 1, and the gas phase discharge port 22 is connected to the feed port 31 of the vacuum buffer tank 3. Among them, the feed port 21, the liquid phase discharge port 23 and the gas phase discharge port 22 of the top condenser 2 are different ports of the material pipeline. The cooling pipeline of the top condenser 2 is connected to a cooling medium pipeline, such as a cold water pipeline.

[0022] The vacuum buffer tank 3 is a gas buffer device that can reduce the pipeline pressure fluctuation in the white oil refining system. The feed port 31 of the vacuum buffer tank 3 is connected to the gas phase discharge port 22 of the top condenser 2, and the discharge port 32 is connected to the air intake port 41 of the water ring vacuum pump 4.

[0023] The water ring vacuum pump 4 is an air pump device that can generate vacuum pressure for the white oil refining system and provide pipeline transportation power. The air intake port 41 of the water ring vacuum pump 4 is connected to the discharge port 32 of the vacuum buffer tank 3, the output port 42 is connected to the feed port 51 of the gas-liquid separation tank 5, and the water replenishment port 43 is connected to the liquid phase discharge port 73 of the aeration tank 7 and the upstream water replenishment pipeline. Preferably, the controller 44 of the water ring vacuum pump 4 is connected to the top pressure sensor 16 of the kettle reboiler 1, and the operating speed (power) of the water ring vacuum pump 4 is controlled according to the measurement data of the top pressure sensor 16 to maintain the internal air pressure of the kettle reboiler 1 (to stabilize it at the design pressure) and the gas output of the gas phase discharge port 12. Optionally, the white oil refining system includes multiple water ring vacuum pumps 4, and each water ring vacuum pump 4 is connected in parallel.

[0024] The gas-liquid separation tank 5 is a separation device for gas phase and liquid phase components. The feed port 51 of the gas-liquid separation tank 5 is connected to the output port 42 of the water ring vacuum pump 4, the gas phase discharge port 52 is connected to the downstream VOC adsorption device, and the liquid phase discharge port 53 is connected to the feed port 61 of the oil separator 6.

[0025] The oil separator 6 is a liquid separation device that can absorb and isolate white oil components from the liquid. The feed port 61 of the oil separator 6 is connected to the liquid phase discharge port 53 of the gas-liquid separation tank 5, and the discharge port 62 is connected to the feed port 71 of the aeration tank 7.

[0026] The aeration tank 7 is an aeration device, including heating and air stripping equipment, capable of separating volatile gases from liquid. The feed port 71 of the aeration tank 7 is connected to the discharge port 62 of the oil separator 6, the gas phase discharge port 72 is connected to the downstream VOC adsorption device, and the liquid phase discharge port 73 is connected to the water replenishment port 43 of the water ring vacuum pump 4.

[0027] The water ring vacuum pump 4 provides a reduced pressure vacuum environment for the kettle reboiler 1, so that the absolute pressure in the kettle reboiler 1 is maintained at 30-50 kPa to increase the volatility of dichloromethane. The vacuum distillation mainly utilizes the huge difference in relative volatility between dichloromethane and white oil under reduced pressure conditions to separate dichloromethane from crude white oil.

[0028] The upstream equipment is subjected to low-temperature distillation (40-50°C) to distill and recover dichloromethane from the lithium battery diaphragm extract, and obtain crude white oil. The crude white oil enters the kettle reboiler 1 from the feed port of the kettle reboiler 1, is heated, and the temperature is maintained at 130-150°C (preferably 140°C), and is reduced to 30-50kPa (vacuum) to increase the volatility of dichloromethane. The gas distributor of the kettle reboiler 1 injects the nitrogen transported from the upstream pipeline into the crude white oil, and nitrogen stripping is performed with dichloromethane to further increase the volatility of dichloromethane. Preferably, the temperature of the nitrogen input to the kettle reboiler 1 is not lower than 140°C to maintain the temperature of the crude white oil. The crude white oil is subjected to high temperature, vacuum distillation and nitrogen stripping to become refined white oil, which is discharged and recovered from the liquid phase discharge port of the kettle reboiler 1. It is worth noting that the prior art requires that the content of dichloromethane in the refined white oil needs to be ≤30ppm. Experimental verification shows that when the kettle reboiler operates at 140°C and 30-50 kPa, the residual dichloromethane in the refined white oil can meet this indicator.

[0029] Nitrogen stripping mainly utilizes the inertness and stability of nitrogen to effectively "carry" the dichloromethane that needs to be extracted and separated from the crude white oil by adjusting the temperature, pressure and nitrogen flow rate. In this process, nitrogen not only acts as a carrier, but also plays a role in protecting and preventing the white oil from oxidation and discoloration, and there is no problem of air pollution.

[0030] Under normal pressure, the gas-liquid phase transition temperature of white oil of different grades is 250-350℃, and the gas-liquid phase transition temperature of dichloromethane is 40℃. On the one hand, in order to reduce energy consumption (economical), on the other hand, under reduced pressure conditions, the relative volatility of white oil and dichloromethane will increase, which is conducive to the separation of the two, so as to achieve the best separation effect. On the third hand, it is also necessary to ensure that the tail gas pressure matches the pressure of the water ring vacuum pump (maintaining the pressure in the kettle reboiler 1 stable and without fluctuation), so the crude white oil temperature is heated to 130-150℃, the pressure is reduced to 30-50kPa, and nitrogen gas stripping is used at the same time, which can fully volatilize the dichloromethane in the crude white oil, form dichloromethane vapor, and realize the separation of white oil and dichloromethane. However, white oil vapor will inevitably be generated. Therefore, the tail gas discharged from the gas phase outlet of the kettle reboiler 1 includes dichloromethane, white oil and nitrogen components. Dichloromethane is treated by the downstream VOC adsorption device, but the white oil component in the tail gas has a high boiling point and high viscosity, which will reduce the life of the adsorption material, so it is necessary to fully remove the white oil component in the tail gas before entering the VOC adsorption device. Among them, the nitrogen component does not affect the effect of VOC adsorption and emission, so it does not need to be removed.

[0031] The tail gas discharged from the gas phase outlet 12 of the kettle reboiler 1 enters the material pipeline of the tower top condenser 2 through the feed port 21 of the tower top condenser 2, and is fully heat exchanged with the cooling medium in the cooling pipeline to reduce the temperature to the design temperature, such as the condensation and liquefaction temperature of dichloromethane (40°C). The condensate formed by condensation is discharged from the liquid phase outlet 23 of the tower top condenser 2, and refluxed into the kettle reboiler 1 through the tower top reflux port 15 of the kettle reboiler 1. The non-condensable gas formed by condensation is discharged from the gas phase outlet 22 of the tower top condenser 2, and input into the vacuum buffer tank 3 through the feed port 31 of the vacuum buffer tank 3. The non-condensable gas includes dichloromethane, white oil and nitrogen components.

[0032] The vacuum buffer tank 3 can reduce the pipeline pressure fluctuation in the white oil refining system and prevent the pipeline and process equipment from being impacted by the drastic change of gas pressure. The non-condensable gas in the vacuum buffer tank 3 is output from the discharge port 32 and input into the water ring vacuum pump 4 from the air intake port 41 of the water ring vacuum pump 4.

[0033] The water ring vacuum pump 4 inputs working fluid through the water replenishment port 43, inputs non-condensable gas through the air intake port 41, and outputs the mixed gas and liquid through the output port 42. The water ring vacuum pump 4 provides power for the gas phase materials in the kettle reboiler 1, the tower top condenser 2 and the vacuum buffer tank 3, so that they move in the pipeline and equipment. The power of the water ring vacuum pump 4 itself comes from the variable frequency motor. The mixed gas and liquid include liquid components of water and white oil, and gas components of dichloromethane and nitrogen. It is worth noting that due to the impact and shearing effect of the impeller of the water ring vacuum pump 4, the white oil component in the non-condensable gas will be broken up into small droplets and mixed into the water, thus forming an oil-water mixture, so that the white oil that is almost insoluble in water can also be completely discharged with the water flow, and almost no deposition, floating or adhesion will occur. The dichloromethane and nitrogen components in the non-condensable gas are gases that are insoluble in water, so the white oil component can be separated in the gas-liquid separation tank 5.

[0034] The controller 44 of the water ring vacuum pump 4 is connected to the top pressure sensor 16 of the kettle reboiler 1, and the operating power of the water ring vacuum pump 4 is controlled according to the measurement data of the top pressure sensor 16, so as to control the air intake of the air intake port 41, and then control the air pressure in the kettle reboiler 1 to remain stable. It is worth noting that due to the connection relationship between the kettle reboiler 1, the tower top condenser 2, the vacuum buffer tank 3 and the water ring vacuum pump 4, the water ring vacuum pump 4 simultaneously reduces the internal air pressure of the tower top condenser 2 and the vacuum buffer tank 3, that is, provides a vacuum environment.

[0035] The mixed gas and liquid outputted from the output port 42 of the water ring vacuum pump 4 is inputted into the gas-liquid separation tank 5 through the feed port 51 of the gas-liquid separation tank 5, and separated into a mixed liquid and a mixed gas. The mixed gas includes dichloromethane and nitrogen components, the mixed liquid includes water and white oil components, and the mixed liquid may include unseparated dichloromethane components. The mixed gas is outputted from the gas phase discharge port 52 of the gas-liquid separation tank 5 and sent to the downstream VOC adsorption device for further treatment. The mixed liquid is outputted from the liquid phase discharge port 53 of the gas-liquid separation tank 5 and inputted into the oil separator 6 through the feed port 61 of the oil separator 6.

[0036] The oil separator tank 6 absorbs and separates the white oil component from the mixed liquid to obtain an oil separator liquid. The oil separator liquid includes water and the dichloromethane component that may not be separated. The oil separator liquid is output from the discharge port 62 of the oil separator tank 6 and input into the aeration tank 7 from the feed port 71 of the aeration tank 7.

[0037] The aeration tank 7 heats the oil-water separation liquid and inputs air into the oil-water separation liquid for gas stripping, thereby evaporating the dichloromethane component that may exist in the oil-water separation liquid and obtaining aeration gas and aeration liquid. The aeration gas is output through the gas phase discharge port 72 of the aeration tank 7 and sent to the downstream VOC adsorption device for further treatment. The aeration liquid is output through the liquid phase discharge port 73 of the aeration tank 7 and input through the water replenishment port 43 of the water ring vacuum pump 4 as the working fluid of the water ring vacuum pump 4.

[0038] White oil is a mineral oil, the main component of which is saturated hydrocarbon compounds, and its water solubility is extremely low. White oil is almost insoluble in water, so in the mixed gas and liquid, white oil mainly exists in the form of droplets or oil film, rather than dissolved in water. Therefore, white oil is more attached to the surface of the equipment in the form of droplets or oil film, resulting in low separation efficiency of white oil in the gas-liquid separator and difficulty in recovering it by simple water phase separation. White oil has a high viscosity, especially at low temperatures, and its fluidity is poor, making it more likely to deposit on the pipe wall. White oil has a high boiling point and high thermal stability, and usually does not decompose or chemically react at the operating temperature of the water ring vacuum pump. The main problem with white oil is that it will coke at high temperatures, especially when in contact with air. However, if the temperature in the pipeline is low, the white oil may become more viscous, further exacerbating the deposition phenomenon.

[0039] Specifically, the low solubility of white oil makes it difficult to recover by dissolving and cooling, and it relies more on physical separation. The high boiling point of white oil means that it will not vaporize significantly in the circulating water system, and the recovery efficiency may be limited by the separation efficiency. The high thermal stability of white oil prevents it from decomposing during operation, but coking needs to be prevented.

[0040] The water ring vacuum pump has a high shear force impeller, which makes the white oil be fully sheared in the water, forming fine oil droplets mixed with water to form a uniform liquid phase component. According to the actual operation situation, the ratio of water to white oil is dynamically adjusted to ensure that the particle size of the oil droplets is small enough.

[0041] Nitrogen is an inert gas and will not react chemically with white oil, dichloromethane or water. Nitrogen is filled into the kettle reboiler 1 so that it can be used as a protective gas for white oil at high temperatures, thereby preventing the white oil from contacting the air and causing the color to darken. In addition, nitrogen can remove the light component dichloromethane gas in the white oil, thereby ensuring the purity of the recovered white oil.

[0042] Different from the above-mentioned embodiment, the white oil refining system provided in the second embodiment of the present invention further includes a water ring pump condenser 8 , a separation tank condenser 9 and an expansion pipe 1 .

[0043] The water ring pump condenser 8 is a gas condensation device, which has a cooling pipeline and a material pipeline. Among them, the cooling pipeline is connected to the upstream and downstream cooling medium pipelines, such as cooling water pipelines. The feed port 81 (material pipeline) of the water ring pump condenser 8 is connected to the liquid phase discharge port 73 of the aeration tank 7, and the discharge port 82 is connected to the water replenishment port 43 of the water ring vacuum pump 4. The aeration liquid input into the material pipeline of the water ring pump condenser 8 is fully heat-exchanged with the cooling medium in the cooling pipeline, and the temperature is reduced to the design temperature to meet the temperature requirements of the water ring vacuum pump 4 for the working fluid.

[0044] The separation tank condenser 9 is a gas condensation device having a cooling pipeline and a material pipeline. The expansion pipe 10 is a small gas-liquid separation tank. Among them, the cooling pipeline connects the upstream and downstream cooling medium pipelines, such as the cooling water pipeline. The feed port 91 (material pipeline) of the separation tank condenser 9 is connected to the gas phase discharge port 52 of the gas-liquid separation tank 5, and the discharge port 92 is connected to the feed port 101 of the expansion pipe 10. The gas phase discharge port 102 of the expansion pipe 10 is connected to the downstream VOC adsorption device, and the liquid phase discharge port 103 is connected to the downstream condensate recovery pipeline, which is used to further separate the condensed dichloromethane and nitrogen.

[0045] The mixed gas separated by the gas-liquid separation tank 5 is condensed to the design temperature (for example, the condensation temperature of dichloromethane) by the separation tank condenser 9, and is separated into the separation condensate and the separation non-condensable gas in the expansion tube 10. Because the condensation temperature of nitrogen is about -200°C, and the condensation temperature of dichloromethane is about 40°C, the separation tank condenser 9 is designed to be able to condense gaseous dichloromethane into liquid dichloromethane, but cannot condense nitrogen into liquid nitrogen. Therefore, the separation condensate is liquid dichloromethane, which is sent to the downstream condensate recovery device through the liquid phase discharge port 103. The separation non-condensable gas includes gaseous dichloromethane and nitrogen components, which are sent to the downstream VOC adsorption device through the gas phase discharge port 102. Because of the inert gas properties of nitrogen, it will not affect the adsorption effect of the VOC adsorption device on dichloromethane.

[0046] The third embodiment of the present invention provides a refining method, which at least includes the following steps.

[0047] Step S1: using a kettle reboiler 1 to heat the crude white oil to a design temperature (e.g., 130-150° C.), using a water ring vacuum pump 4 to reduce the internal pressure of the kettle reboiler 1 to a design pressure (e.g., 30-50 kPa), and using a gas distributor 14 of the kettle reboiler 1 to distribute nitrogen into the crude white oil, so as to perform vacuum distillation and nitrogen gas on the crude white oil, so as to separate the crude white oil into refined white oil and tail gas.

[0048] The feed port 11 (liquid distributor) of the kettle reboiler 1 is connected to the upstream crude white oil pipeline, the gas phase discharge port 12 is connected to the feed port 21 of the top condenser 2, the liquid phase discharge port 13 is connected to the downstream refined white oil pipeline, the gas distributor 14 is connected to the upstream nitrogen pipeline, and the top reflux port 15 is connected to the liquid phase discharge port 23 of the top condenser 2; The controller 44 of the water ring vacuum pump 4 controls the rotation speed of the water ring vacuum pump 4 according to the detection data of the top pressure sensor 16 inside the kettle reboiler 1 .

[0049] Preferably, the heating temperature of the crude white oil in the kettle reboiler 1 is not less than 140° C. Optionally, the temperature of the nitrogen gas input into the kettle reboiler 1 is not less than 140° C. to maintain the temperature of the crude white oil.

[0050] Step S2: using the tower top condenser 2 to condense the tail gas to a designed temperature (eg, the condensation and liquefaction temperature of dichloromethane) to separate the tail gas into condensate and non-condensable gas.

[0051] The feed port 21 of the tower top condenser 2 is connected to the gas phase discharge port 12 of the kettle reboiler 1, the gas phase discharge port 22 is connected to the feed port 31 of the vacuum buffer tank 3, and the liquid phase discharge port 23 is connected to the tower top reflux port 15 of the kettle reboiler 1; Step S3: using the vacuum buffer tank 3 to reduce the pressure fluctuation of the kettle reboiler 1 and the tower top condenser 2.

[0052] The feed port 31 of the vacuum buffer tank 3 is connected to the gas phase discharge port 22 of the tower top condenser 2, and the discharge port 32 is connected to the air intake port 41 of the water ring vacuum pump 4; Step S4: using the water ring vacuum pump 4 to provide power for the gas phase materials in the kettle reboiler 1, the tower top condenser 2 and the vacuum buffer tank 3, so that they move in the pipelines and equipment; using the working fluid in the water ring vacuum pump 4 to mix the white oil component in the non-condensable gas, the white oil component in the non-condensable gas is separated from the gas phase components of dichloromethane and nitrogen to form a mixed gas-liquid.

[0053] The air inlet 41 of the water ring vacuum pump 4 is connected to the discharge port 32 of the vacuum buffer tank 3, the air outlet 42 is connected to the feed port 51 of the gas-liquid separation tank 5, and the water supply port 43 is connected to the liquid phase discharge port 73 of the aeration tank 7 and the upstream water supply pipeline; Step S5: Separate the mixed gas and liquid into mixed gas and mixed liquid using the gas-liquid separation tank 5, and recycle and process the mixed gas using downstream equipment.

[0054] The feed port 51 of the gas-liquid separation tank 5 is connected to the output port 42 of the water ring vacuum pump 4 , the gas phase discharge port 52 is connected to the downstream VOC adsorption device, and the liquid phase discharge port 53 is connected to the feed port 61 of the oil separator 6 .

[0055] This step may also include the following: The separation tank condenser 9 is used to cool the mixed gas to the design temperature (for example, the condensation and liquefaction temperature of dichloromethane), and the expansion pipe 10 is used to separate the mixed gas into separated non-condensable gas and separated condensate, and the separated non-condensable gas and separated condensate are respectively recovered by downstream equipment.

[0056] The feed port 91 of the separation tank condenser 9 is connected to the gas phase discharge port 52 of the gas-liquid separation tank 5, and the discharge port 92 is connected to the feed port 101 of the expansion tube 10. The liquid phase discharge port 103 of the expansion tube 10 is connected to the downstream condensate recovery pipeline, and the gas phase discharge port 102 is connected to the downstream VOC adsorption device.

[0057] Step S6: using the oil separator 6 to separate the white oil component in the mixed liquid to obtain an oil separator liquid.

[0058] The feed port 61 of the oil separator 6 is connected to the liquid phase discharge port 53 of the gas-liquid separation tank 5, and the discharge port 62 is connected to the feed port 71 of the aeration tank 7; Step S7: using the aeration tank 7 to heat and aerate the oil separator liquid, separating the gas phase dichloromethane to form aeration gas and aeration liquid; using downstream equipment to recover and process the aeration gas; using the aeration liquid as a working fluid and providing it to the water ring vacuum pump 4.

[0059] The feed port 71 of the aeration tank 7 is connected to the discharge port 62 of the oil separator tank 6 , the gas phase discharge port 72 is connected to the downstream VOC adsorption device, and the liquid phase discharge port 73 is connected to the water replenishment port 43 of the water ring vacuum pump 4 .

[0060] Preferably, the oil-water separator liquid is heated to a design temperature, such as above the vaporization temperature of dichloromethane (40° C.) by using the aeration tank 7. Preferably, the oil-water separator liquid is heated to above 50° C. by using the aeration tank 7.

[0061] This step may also include the following: The aeration liquid is cooled to the design temperature by the water ring pump condenser 8 and then supplied to the water ring vacuum pump 4 as the working liquid.

[0062] The feed inlet 81 of the water ring pump condenser 8 is connected to the liquid phase discharge port 72 of the aeration tank 7 , and the discharge port 82 is connected to the water replenishment port 43 of the water ring vacuum pump 4 .

[0063] In summary, the embodiments of the present invention provide a white oil refining system and a refining method for recovering lithium battery diaphragm extract. The heating temperature of the crude white oil in the white oil refining system is 140°C, the purity of nitrogen stripping is >99.9%, the outlet temperature of the non-condensing steam condenser in the white oil refining system is 40°C, the vacuum degree of the vacuum system is 50kPa, and the non-condensable gas entering the vacuum pump contains trace amounts of dichloromethane and white oil. The dichloromethane content in the refined white oil after refining treatment is ≤50ppm. The vacuum pump uses a water ring vacuum pump to remove the white oil component in the non-condensable gas (the white oil fume in the non-condensable steam enters the wastewater), and the non-condensable gas continues to enter the VOC recovery adsorption device to further recover dichloromethane. The water ring vacuum pump removes the high-boiling point white oil component, which can extend the life of the adsorption material of the subsequent VOC device. The wastewater discharged by the water ring vacuum pump enters the aeration device after the white oil is removed by the degreasing tank. The aeration device is heated to 50℃, and auxiliary air aeration can remove dichloromethane from the wastewater. The waste gas containing dichloromethane also enters the VOC recovery adsorption device. The aerated water is cooled and then enters the water ring vacuum pump for recycling.

[0064] It should be noted that the above embodiments are only examples, and the technical solutions of the various embodiments can be combined, all within the protection scope of the present invention.

[0065] It should be noted that the order of steps in the embodiments of the present invention can be changed according to actual needs, the order of the steps can be changed, and serial processing can be changed to parallel processing, and is not limited to the order of steps listed in the embodiments.

[0066] The orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings and is only for the convenience of describing the present invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0067] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0068] The above is a detailed description of a white oil refining system and a refining method for recycling lithium battery diaphragm extract provided by the present invention. For a person skilled in the art, any obvious changes made to it without departing from the essence of the present invention will constitute an infringement of the patent right of the present invention and will bear the corresponding legal liability.

Claims

1. A white oil refining system for recycling lithium battery diaphragm extract, characterized in that It includes kettle reboiler, tower top condenser, vacuum buffer tank, water ring vacuum pump, gas-liquid separation tank, oil separator and aeration tank; among which, The feed port of the kettle reboiler is connected to the upstream pipeline, the gas phase discharge port is connected to the feed port of the tower top condenser, the liquid phase discharge port is connected to the downstream pipeline, the gas distributor is connected to the upstream pipeline, and the tower top reflux port is connected to the liquid phase discharge port of the tower top condenser; The gas phase discharge port of the tower top condenser is connected to the feed port of the vacuum buffer tank; the discharge port of the vacuum buffer tank is connected to the air intake port of the water ring vacuum pump; the output port of the water ring vacuum pump is connected to the feed port of the gas-liquid separation tank, and the water supply port is connected to the liquid phase discharge port of the aeration tank and the upstream water supply pipeline; The gas phase outlet of the gas-liquid separation tank is connected to the downstream VOC adsorption device, and the liquid phase outlet is connected to the feed port of the oil separator tank; the outlet of the oil separator tank is connected to the feed port of the aeration tank; the gas phase outlet of the aeration tank is connected to the downstream VOC adsorption device.

2. The white oil refining system for recycling lithium battery diaphragm extract according to claim 1, characterized in that: A top pressure sensor is provided at the top of the kettle reboiler; the controller of the water ring vacuum pump is connected to the top pressure sensor, and the operating speed of the water ring vacuum pump is controlled according to the measurement data of the top pressure sensor to maintain the internal gas pressure of the kettle reboiler and the gas output of the gas phase discharge port.

3. The white oil refining system for recovering lithium battery diaphragm extract according to claim 2, characterized in that It also includes a separation tank condenser and an expansion pipe; wherein, The feed port of the separation tank condenser is connected to the gas phase discharge port of the gas-liquid separation tank, and the discharge port is connected to the feed port of the expansion pipe; the gas phase discharge port of the expansion pipe is connected to the downstream VOC adsorption device, and the liquid phase discharge port is connected to the downstream condensate recovery pipeline.

4. The white oil refining system for recovering lithium battery diaphragm extract according to claim 2, characterized in that It also includes a water ring pump condenser; wherein, The feed inlet of the water ring pump condenser is connected to the liquid phase discharge port of the aeration tank, and the discharge port is connected to the water replenishment port of the water ring vacuum pump.

5. A refining method for recovering lithium battery diaphragm extract, based on the white oil refining system according to any one of claims 1 to 4, characterized in that The following steps are involved: Step S1: heating the crude white oil to a designed temperature by using a kettle reboiler, reducing the internal pressure of the kettle reboiler to the designed pressure by using a water ring vacuum pump, and distributing nitrogen into the crude white oil by using a gas distributor of the kettle reboiler to perform vacuum distillation and nitrogen gas on the crude white oil, so as to separate the crude white oil into refined white oil and tail gas; Step S2: condensing the tail gas to a designed temperature using the tower top condenser to separate the tail gas into condensate and non-condensable gas; Step S3: using the vacuum buffer tank to reduce the pressure fluctuation of the kettle reboiler and the tower top condenser; Step S4: using the water ring vacuum pump to provide power for the gas phase materials in the kettle reboiler, the tower top condenser and the vacuum buffer tank, so that they move in the pipelines and equipment; and using the water ring vacuum pump to mix the white oil component into small droplets in the working fluid, and to separate the white oil component in the non-condensable gas from the gas phase components of dichloromethane and nitrogen to form a mixed gas-liquid; Step S5: using the gas-liquid separation tank to separate the mixed gas and liquid into a mixed gas and a mixed liquid, and using downstream equipment to recover and process the mixed gas; Step S6: using the oil separator to separate the white oil component in the mixed liquid to obtain an oil separator liquid; Step S7: using the aeration tank to heat and aerate the oil separator liquid, separating the gas phase dichloromethane to form aeration gas and aeration liquid; using downstream equipment to recover and process the aeration gas; using the aeration liquid as a working fluid and providing it to the water ring vacuum pump.

6. The refining method for recovering lithium battery diaphragm extract according to claim 5, characterized in that: The controller of the water ring vacuum pump is used to control the rotation speed of the water ring vacuum pump according to the detection data of the top pressure sensor inside the kettle reboiler.

7. The refining method for recovering lithium battery diaphragm extract according to claim 6, characterized in that: The heating temperature of the crude white oil in the kettle reboiler is not lower than 140°C; the temperature of the nitrogen gas input into the kettle reboiler is not lower than 140°C.

8. The refining method for recovering lithium battery diaphragm extract according to claim 7, characterized in that: The mixed gas is cooled to the design temperature by using the separation tank condenser, the mixed gas is separated into separated non-condensable gas and separated condensate by using the expansion pipe, and the separated non-condensable gas and separated condensate are respectively recovered by downstream equipment.

9. The refining method for recovering lithium battery diaphragm extract according to claim 8, characterized in that: The aeration liquid is cooled to the designed temperature by the water ring pump condenser and then provided to the water ring vacuum pump as the working liquid.

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