A dichloromethane recovery device and method in a lithium battery separator production process

Abstract

The application discloses a dichloromethane recovery device and method in a lithium battery diaphragm production process, and belongs to the technical field of lithium battery diaphragm production. The application comprises a box body and a fan arranged at the inlet of the box body, a condenser and a heater are arranged in the box body, and a liquid collecting groove is arranged at the bottom of the box body. The condenser is arranged in multiple groups along the flow direction of dichloromethane, and baffles are arranged between adjacent condensers, the baffles are arranged in an upper and lower staggered mode in sequence, and a wire mesh demister is arranged above the liquid collecting groove. The dichloromethane recovery device of the application is used for the dichloromethane discharged from a drying box, the dichloromethane is first condensed by the condenser and then flows into the liquid collecting groove, the dichloromethane which is not condensed is heated by the heater and then returned to the drying box, the utilization rate of dichloromethane is improved, the concentration of dichloromethane is reduced, and the treatment cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery separator production technology, and more specifically, relates to a dichloromethane recovery device and method in the lithium battery separator production process. Background Technology

[0002] The function of a lithium-ion battery separator is to insulate the positive and negative electrodes to prevent short circuits, allowing lithium ions to pass freely. In cases of overcharging or high temperature, the separator's pores prevent contact between the positive and negative electrodes, thus achieving insulation. It significantly affects key performance characteristics of lithium batteries, such as capacity, cycle performance, and charge / discharge current density. Currently, the manufacturing processes for lithium-ion battery separators are mainly divided into two types: dry processes (uniaxial and biaxial stretching) and wet processes (thermally induced phase separation). Wet-process separators have advantages over dry-process separators in terms of mechanical properties, permeability, and physicochemical properties. Coating significantly improves the thermal stability of wet-process separators. Overall, wet-coated separators have significant performance advantages.

[0003] The production process of wet-process lithium-ion battery separators generally includes: feeding, extrusion, casting, stretching, extraction, drying, traction, winding, inspection, slitting, and packaging. During separator production, white oil acts as a pore-forming agent, uniformly distributed within the molecular chain. In the extraction process, dichloromethane acts as the extractant, extracting the white oil and separating it from the separator, thus forming a microporous structure with uniform pore size. The drying process removes dichloromethane from the separator surface and pores. In existing wet-process lithium-ion battery separator production processes, all dichloromethane emitted during the drying process is typically sent to a gas recovery and treatment device. This operation not only wastes resources but also increases the investment cost of the recovery and treatment device, thereby increasing the separator production cost and reducing product competitiveness.

[0004] A search revealed Chinese Patent Application CN 208448686 U, which discloses a pretreatment device for recovering dichloromethane waste gas. This application includes a drying chamber, an exhaust fan, a condenser tank, a storage tank, and a microporous tube. The drying chamber is used to heat and dry the extracted diaphragm. The microporous tube is located inside the condenser tank. One end of the exhaust fan is connected to the drying chamber, and the other end is connected to the microporous tube in the condenser tank. The condenser tank is connected to the storage tank. The microporous tube has holes to allow the dichloromethane waste gas from the drying chamber, transported by the exhaust fan, to be discharged into the condenser tank through these holes. Multiple holes are evenly distributed along the axial direction of the microporous tube. This application uses a condenser tank to pretreat the dichloromethane waste gas from the drying chamber, reducing subsequent treatment costs.

[0005] For example, Chinese Patent Application No. CN 217391969 U discloses a dichloromethane recovery system for a wet-process lithium-ion battery separator. This application includes a drying chamber exhaust fan, with compressors one and two externally connected to the exhaust body. Both compressors one and two are connected to an external gas-liquid separator, and a heat exchanger is installed between the gas-liquid separator and compressor two. The gas-liquid separator is externally connected to a water cooler, and the outlet of the precooler is connected to a membrane module. The membrane module is connected to three externally connected adsorption towers (one, two, and three). The gas phase outlets of adsorption towers one, two, and three are connected to an external chimney, while the liquid phase outlets of adsorption towers one, two, and three are connected to a stratification tank and an aeration tank. This system significantly reduces operating costs, achieves a dichloromethane recovery rate of over 99.9%, and generates no other environmental pollutants such as wastewater, waste liquid, or waste residue.

[0006] While both of the aforementioned documents can reduce the cost of dichloromethane recycling, neither fundamentally solves the problem of high recycling costs for dichloromethane. Summary of the Invention

[0007] 1. The problem to be solved

[0008] To address at least some of the problems existing in the prior art, this invention proposes a dichloromethane recovery device and method in the lithium battery separator production process. Using the technical solution of this invention, dichloromethane flowing out of the drying chamber is partially condensed, and simultaneously, a portion of the dichloromethane gas is returned to the drying chamber to purge and dry the separator. This improves the utilization rate of dichloromethane while reducing its concentration, thereby lowering processing costs.

[0009] 2. Technical Solution

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] The present invention discloses a dichloromethane recovery device in the production process of lithium battery separator, comprising a box and a fan installed at the inlet of the box. The box is equipped with a condenser and a heater, and a liquid collection tank is provided at the bottom of the box. Dichloromethane discharged from the drying box first flows into the liquid collection tank after being condensed by the condenser. The uncondensed dichloromethane is heated by the heater and then returns to the drying box.

[0012] Furthermore, the condenser is provided in multiple sets along the flow direction of dichloromethane, and baffles are provided between adjacent condensers, with the baffles arranged alternately in a staggered manner.

[0013] Furthermore, the housing comprises two layers, one above the other. The lower layer is further divided into a condensation zone and a circulation zone. The condenser is located in the condensation zone, and the upper and lower layers are interconnected through the circulation zone.

[0014] Furthermore, a wire mesh demister is provided at the bottom of the condensation zone, which is located above the liquid collection tank.

[0015] Furthermore, a wire mesh demister is provided at the bottom of the flow zone, and the wire mesh demister is separated from the wire mesh demister in the condensation zone by a partition.

[0016] Furthermore, the wire mesh demister has a wire mesh density of 0.1-2 mm and a thickness of 1-10 cm.

[0017] Furthermore, the heat exchange area of ​​the condenser is 100-1000 m². 2 The fan has an air volume of 1000m³ / hour to 5600m³ / hour and a condensing temperature of less than 39.8℃.

[0018] Furthermore, a wire mesh demister is provided at the outlet of the circulation area. The wire mesh demister is inclined at an angle of 30-60°.

[0019] Furthermore, a filter is provided in the upper region, and the filter has a filtration level of 0.5um-30um.

[0020] The method for recovering dichloromethane using the above-described apparatus includes the following steps:

[0021] S1. The dichloromethane gas from the product inside the drying chamber is discharged into the recovery unit by a fan.

[0022] S2, dichloromethane gas is first condensed in the condensation zone at the bottom of the chamber. The condensed liquid is filtered by a wire mesh demister and then flows into the collection tank.

[0023] S3. Uncondensed dichloromethane gas passes through the flow area to the upper layer of the chamber, and after being heated and filtered twice, it re-enters the drying chamber.

[0024] S4. The clean liquid dichloromethane in the collection tank is re-entered into the extraction tank.

[0025] 3. Beneficial effects

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) A dichloromethane recovery device in the lithium battery separator production process of the present invention partially condenses the dichloromethane flowing out of the drying box; at the same time, part of the dichloromethane gas returns to the drying box to purge and dry the separator, thereby improving the dichloromethane utilization rate and reducing the concentration of dichloromethane, thereby reducing the processing cost.

[0028] (2) A dichloromethane recovery device in the lithium battery separator production process of the present invention, wherein multiple sets of condensers are provided along the dichloromethane flow direction, and baffles are provided between adjacent condensers, and the baffles are arranged alternately in the upper and lower positions; by setting the baffles arranged alternately in the upper and lower positions, the flow path of dichloromethane in the condensation zone can be effectively improved, thereby improving the condensation effect.

[0029] (3) A dichloromethane recovery device in the lithium battery separator production process of the present invention is provided with a wire mesh demister at the bottom of the lower box. On the one hand, it can effectively remove impurities in the condensed liquid; on the other hand, by controlling the wire mesh aperture, the condensed liquid can form a liquid seal in the wire mesh demister to prevent gas from being discharged through the wire mesh demister and ensure the gas-liquid separation effect. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of a dichloromethane recovery device in the lithium battery separator production process according to the present invention.

[0031] Figure 2 This is a front view of a dichloromethane recovery device in the lithium battery separator production process according to the present invention;

[0032] Figure 3 This is a cross-sectional view of a dichloromethane recovery device in the lithium battery separator production process according to the present invention;

[0033] Figure 4 This is a schematic diagram of the internal structure of a dichloromethane recovery device in the lithium battery separator production process of the present invention.

[0034] In the diagram: 1. Housing; 11. Condensation zone; 12. Flow zone;

[0035] 2. Fan; 3. Condenser; 4. Heater; 5. Liquid collection tank; 6. Baffle; 7. Wire mesh demister; 8. Baffle; 9. Filter. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments.

[0037] Example 1

[0038] refer to Figure 1 , Figure 3As shown in this embodiment, a dichloromethane recovery device in the lithium battery separator production process includes a housing 1, which has a gas inlet and a gas outlet. A fan 2 is connected to the gas inlet, which transfers the extractant volatilized in the drying chamber into the housing 1. The extractant used in this embodiment is dichloromethane, but other volatile organic solvents such as acetone can also be used.

[0039] The chamber 1 is equipped with a condenser 3 and a heater 4, and a collection tank 5 is provided at the bottom of the chamber 1. Dichloromethane entering the chamber 1 is first condensed by the condenser 3 and flows into the collection tank 5. The uncondensed dichloromethane is heated by the heater 4 and then returns to the drying chamber to purge the diaphragm for drying.

[0040] This embodiment of a dichloromethane recovery device in the lithium battery separator production process improves the utilization rate of dichloromethane by returning a portion of the dichloromethane to the drying chamber, and at the same time reduces the concentration of the dichloromethane to be treated, thereby saving processing costs.

[0041] Specifically, the housing 1 comprises two layers arranged vertically. The lower layer is further divided into a condensation zone 11 and a flow zone 12 distributed horizontally, and the upper and lower layers are connected through the flow zone 12. This design facilitates the placement of the gas inlet and gas outlet on the same side of the housing 1 and effectively reduces the overall length of the housing 1.

[0042] In this specific embodiment, the gas inlet is located on the lower housing, and the gas outlet is located on the upper housing. A steel pipe is connected to the gas inlet via a flange. The airflow of the fan 2 at the gas inlet is 1000 m³ / s. 3 / hour - 5600m 3 / hour, preferably 2300-4500m 3 / Hour.

[0043] The condenser 3 is located within the condensation zone 11, which is positioned close to the gas inlet. That is, dichloromethane entering the housing 1 passes sequentially through the condensation zone 11, the flow zone 12, and the upper housing, before being discharged through the gas outlet.

[0044] The heater 4 is located in the upper chamber and is used to heat the incoming dichloromethane gas. Simultaneously, a filter 9 is also provided in the upper chamber, located near the gas outlet, to filter the heated dichloromethane. Preferably, the filter 9 has a filtration rating of 0.5µm-30µm.

[0045] In addition, the liquid collection tank 5 is inclined as a whole, and its inclination direction gradually decreases from the condensation zone 11 to the flow zone 12, so as to facilitate the effective collection of liquid in the liquid collection tank 5.

[0046] In this embodiment, a dichloromethane recovery device is provided in the lithium battery separator production process. The condenser 3 is provided in multiple sets along the flow direction of dichloromethane, and baffles 6 are provided between adjacent condensers 3. The baffles 6 are arranged alternately up and down.

[0047] The staggered arrangement of baffles 6 effectively improves the flow path of dichloromethane in the condensation zone, thereby enhancing the condensation effect and reducing processing costs. Specifically, in this embodiment, the condenser 3 is configured with four sets, each having a heat exchange area of ​​100-1000 m². 2 It is worth noting that this heat exchange area is the total heat exchange area.

[0048] The main operating procedure of the dichloromethane recovery device in the lithium battery separator production process of this embodiment is as follows:

[0049] The dichloromethane gas generated in the drying chamber is discharged into the housing 1 of the recovery device by fan 2.

[0050] The dichloromethane gas entering the chamber 1 is first condensed in the condensation zone 11 of the lower chamber, and the condensed liquid flows into the collection tank 5.

[0051] Uncondensed dichloromethane gas passes through the flow zone 12 to the upper part of the chamber, and is heated by the heater 4 and filtered by the filter 9 before re-entering the drying chamber.

[0052] Liquid dichloromethane collected in the collection tank 5 can be reintroduced into the extraction tank to further improve the utilization rate of dichloromethane.

[0053] Example 2

[0054] The dichloromethane recovery device in the lithium battery separator production process of this embodiment has the same basic structure as that in Embodiment 1. The difference is that a wire mesh demister 7 is also provided in the housing 1 for filtering dichloromethane.

[0055] Specifically, refer to Figure 3 , Figure 4 As shown, a wire mesh demister 7 is provided at the bottom of the housing 1. The wire mesh demister 7 is located above the liquid collection tank 5 and is used to filter impurities from the condensed liquid.

[0056] Preferably, the wire mesh demister 7 has a wire mesh density of 0.1-2 mm and a thickness of 1-10 cm. This size selection ensures effective filtration of the condensate; furthermore, in conjunction with the airflow of the fan 2 and the heat exchange area of ​​the condenser 3, a portion of the condensate remains in the wire mesh demister 7, forming a liquid seal to prevent gaseous dichloromethane from passing through the demister 7. This separates the flow paths of the gas and liquid, achieving good gas-liquid separation.

[0057] The condensation zone 11 and the flow zone 12 are separated by a partition 8. Under normal circumstances, new condensate will accumulate in the condensation zone 11 while some condensate will be discharged through the wire mesh demister 7, thus maintaining a dynamic equilibrium in the amount of condensate actually remaining in the condensation zone 11. However, with prolonged use, the wire mesh demister 7 in the condensation zone 11 will absorb a large amount of impurities, reducing its filtration speed and leading to excessive condensate in the condensation zone 11. Since the amount of condensate in the condensation zone 11 is much greater than that in the flow zone 12, the condensate in the condensation zone 11 can flow over the partition 8 into the flow zone 12 to regulate the dynamic balance of the condensate in the condensation zone 11.

[0058] In addition, a wire mesh demister 7 is also provided at the outlet of the circulation zone 12. The wire mesh demister 7 is inclined at an angle of 30-60° to increase the filtration area.

[0059] Example 3

[0060] This embodiment provides a method for recovering dichloromethane during the production of lithium battery separators, which includes the following steps:

[0061] S1. The dichloromethane gas from the product in the drying chamber is discharged into the housing 1 of the recovery device by the fan 2.

[0062] S2. The dichloromethane gas entering the chamber 1 is first condensed in the condensation zone 11 of the lower chamber. The condensed liquid is filtered by the wire mesh demister 7 and flows into the collection tank 5. At the same time, a liquid seal is formed on the surface of the wire mesh demister 7.

[0063] S3. Uncondensed dichloromethane gas passes through the flow zone 12 to the upper part of the chamber, and after being heated and filtered twice, it re-enters the drying chamber.

[0064] S4. The clean liquid dichloromethane flowing into the collection tank 5 can be reused by re-entering the extraction tank.

[0065] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A dichloromethane recovery device in the production process of lithium battery separators, comprising a housing (1) and a fan (2) installed at the inlet of the housing, characterized in that: The box (1) is equipped with a condenser (3) and a heater (4). The bottom of the box (1) is equipped with a liquid collection tank (5). The dichloromethane discharged from the drying box first flows into the liquid collection tank (5) after being condensed by the condenser (3). The uncondensed dichloromethane is heated by the heater (4) and then returns to the drying box. The housing (1) includes two layers, one above the other. The lower layer is further divided into a condensation zone (11) and a flow zone (12). The condenser (3) is located in the condensation zone (11). The upper and lower layers are connected to each other through the flow zone (12). The bottom of the condensation zone (11) is provided with a wire mesh demister (7), which is located above the liquid collection tank (5). Part of the condensate is retained on the wire mesh demister (7) to form a liquid seal.

2. The dichloromethane recovery device in the lithium battery separator production process according to claim 1, characterized in that: The condenser (3) is provided in multiple sets along the flow direction of dichloromethane, and baffles (6) are provided between adjacent condensers (3), and the baffles (6) are arranged alternately up and down.

3. A dichloromethane recovery device in the lithium battery separator production process according to claim 1 or 2, characterized in that: The bottom of the flow zone (12) is provided with a wire mesh demister (7), which is separated from the wire mesh demister (7) in the condensation zone (11) by a partition (8).

4. The dichloromethane recovery device in the lithium battery separator production process according to claim 3, characterized in that: The wire mesh demister (7) has a wire mesh density of 0.1-2 mm and a thickness of 1-10 cm.

5. A dichloromethane recovery device in the lithium battery separator production process according to claim 4, characterized in that: The heat exchange area of ​​the condenser (3) is 100-1000 m². 2 The air volume of the fan (2) is 1000m³ / hour - 5600m³ / hour.

6. A dichloromethane recovery device in the lithium battery separator production process according to claim 5, characterized in that: A wire mesh demister (7) is provided at the outlet of the circulation area (12). The wire mesh demister (7) is inclined at an angle of 30-60°.

7. A dichloromethane recovery device in the lithium battery separator production process according to claim 1, characterized in that: A filter (9) is provided in the upper area of ​​the housing, and the filter (9) has a filtration level of 0.5um-30um.

8. A method for recovering dichloromethane using the apparatus of claim 7, characterized in that: Includes the following steps, S1. The dichloromethane gas in the product inside the drying chamber is discharged into the box (1) of the recovery device by the fan (2); S2. Dichloromethane gas is first condensed in the condensation zone (11) at the bottom of the box. After condensation, the liquid is filtered by the wire mesh demister (7) and then flows into the collection tank (5). S3. The uncondensed dichloromethane gas passes through the flow area (12) to the upper layer of the box, and after being heated and filtered twice, it re-enters the drying box. S4. The clean liquid dichloromethane in the collection tank (5) is re-entered into the extraction tank.

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