Dichloromethane recovery device

Abstract

The utility model relates to a dichloromethane recovery device which comprises a drying furnace, a condenser and a gas-liquid separator, the drying furnace comprises a first working area and a second working area, and the first working area is provided with a first gas outlet; an inlet of the condenser is communicated with the first air outlet of the first working area, and the condenser is used for condensing dichloromethane discharged from the first air outlet of the first working area; the gas-liquid separator is used for carrying out gas-liquid separation on dichloromethane liquefied by the condenser, the gas-liquid separator is provided with an inlet, a first outlet and a second outlet, the inlet of the gas-liquid separator is communicated with the outlet of the condenser, the first outlet of the gas-liquid separator is communicated with the inlet of the first working area, and the second outlet of the gas-liquid separator is used for discharging dichloromethane liquid. According to the device provided by the utility model, on the premise of ensuring the quality of a diaphragm on a production line, the amount of dichloromethane entering a rear-section adsorption process is reduced, the steam cost and the electricity cost in the adsorption, desorption and condensation processes in the rear-section adsorption process are reduced, and the load of a gas recovery system is reduced.

Description

Technical Field

[0001] The utility model belongs to the field of dichloromethane recovery, and particularly relates to a dichloromethane recovery device. Background Art

[0002] In the wet process lithium battery separator production process in the industry, white oil is mostly used as a pore-forming agent, and after film formation, dichloromethane is used to extract the white oil therein. A large amount of white oil and dichloromethane are used in this process, and recycling dichloromethane and white oil is the key to reducing the production cost of potassium battery separators and improving market competitiveness.

[0003] Extraction and drying are also key processes in the wet process. In the existing drying process, hot air with controlled temperature is continuously supplemented to heat the separator, so that the liquid dichloromethane attached to the separator is vaporized into gas and then recovered by certain means. The concentration of dichloromethane waste gas discharged by the conventional drying process is usually less than 50,000 ppm. At the same time, due to the increasingly high environmental protection requirements for the emission limit of dichloromethane in various places, the applicable treatment methods are limited. The conventional recovery technologies for dichloromethane-containing waste gas mainly include condensation method, adsorption method, and solvent recovery method. The condensation method requires increasing the concentration of dichloromethane. Some manufacturers use a cryogenic device at -40°C for treatment, with large consumption, poor energy efficiency, and high cost.

[0004] The industry usually uses an activated carbon fiber adsorption process for treatment. The dichloromethane gas generated during the drying process is led to an activated carbon fiber adsorption device through an exhaust gas collection device. The activated carbon fiber adsorption device recovers and recycles the dichloromethane therein through adsorption, desorption, and condensation. The existing problems are: the equipment investment of the activated carbon fiber adsorption device is high, and a large amount of steam and chilled water are consumed during the adsorption and desorption process and condensation process, resulting in huge electricity consumption. The electricity cost of the exhaust gas conveying fan is high, and the service life of the activated carbon fiber adsorption device is short. Summary of the Utility Model

[0005] The purpose of the utility model is to provide an improved dichloromethane recovery device.

[0006] To achieve the above purpose, a technical solution adopted by the utility model is:

[0007] A dichloromethane recovery device, the device includes:

[0008] A drying furnace, the drying furnace is used for drying the separator, the drying furnace includes a first working area and a second working area sequentially arranged along the separator conveying direction, and the first working area has a first air outlet;

[0009] A condenser, the inlet of the condenser is communicated with the first air outlet of the first working area, and the condenser is used for condensing the dichloromethane discharged from the first air outlet of the first working area;

[0010] A gas-liquid separator is used to separate the liquefied dichloromethane from the condenser. The gas-liquid separator has an inlet, a first outlet, and a second outlet. The inlet of the gas-liquid separator is connected to the outlet of the condenser. The first outlet of the gas-liquid separator is connected to the inlet of the first working area. The second outlet of the gas-liquid separator is used to discharge the dichloromethane liquid.

[0011] In some embodiments, the first working area and the second working area are separated by a partition. The partition includes an upper partition and a lower partition. The upper partition is located above the lower partition. The upper partition abuts against the upper side wall inside the drying furnace, and the lower partition abuts against the lower side wall inside the drying furnace. There is a gap between the upper partition and the lower partition for the conveying roller for the conveying diaphragm to move.

[0012] In some embodiments, a first fan is provided between the inlet of the condenser and the first air outlet of the first working area, and a second fan is provided between the first outlet of the gas-liquid separator and the inlet of the first working area.

[0013] In some embodiments, a first valve is provided on the pipeline connecting the first air outlet of the first working area and the first fan, and a second valve is provided on the pipeline connecting the second fan and the first outlet of the gas-liquid separator.

[0014] In some embodiments, a gas distributor is provided in the first working area. The gas distributor is used to divert the dichloromethane gas in the first working area to the first fan. The gas distributor includes an air guiding pipe, a first gas converging box, a distribution pipe, and a second gas converging box. There are two air guiding pipes. One end of one air guiding pipe is connected to the first fan through a pipeline, and the other end of one air guiding pipe faces the inside of the first working area. The other ends of the two air guiding pipes are respectively connected to the first gas converging box and the second gas converging box. The opposite ends of the distribution pipe are respectively connected to the first gas converging box and the second gas converging box.

[0015] In some embodiments, the device further includes a recovery system. The recovery system is connected to the second outlet of the gas-liquid separator and is used to recover the dichloromethane liquid discharged from the second outlet of the gas-liquid separator.

[0016] In some embodiments, the condenser uses 7°C chilled water.

[0017] In some embodiments, the volume of the first working area is less than or equal to the volume of the second working area.

[0018] In some embodiments, the first working area further has a second air outlet, and a first tail gas discharge pipeline is provided at the second air outlet of the first working area.

[0019] In some embodiments, the condenser is a plate condenser.

[0020] Another technical solution adopted by the present utility model is:

[0021] Due to the application of the above technical solution, the present utility model has the following advantages compared with the prior art:

[0022] The dichloromethane recovery device provided by the present utility model can recover dichloromethane in the waste gas of the drying process section at a lower cost on the premise of ensuring the quality of the diaphragm of the current production line, reduce the amount of dichloromethane waste gas entering the subsequent adsorption process, reduce the steam cost and electricity cost in the adsorption, desorption, and condensation processes in the subsequent adsorption process, reduce the load of the gas recovery system, and achieve the purposes of environmental protection and cost reduction and efficiency improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Attached Figure 1 is a structural diagram of the dichloromethane recovery device of the present utility model;

[0024] Attached Figure 2 is Figure 1 an enlarged view of the drying furnace in

[0025] Attached Figure 3 is a three-dimensional view of the gas distributor of the dichloromethane recovery device of the present utility model;

[0026] Attached Figure 4 is a front view of the gas distributor of the dichloromethane recovery device of the present utility model.

[0027] In the above drawings:

[0028] 1 - First working area; 2 - Second working area; 3 - Condenser, 31 - First inlet, 32 - Second inlet, 33 - First liquid outlet, 34 - Second liquid outlet; 4 - Gas-liquid separator, 41 - First outlet, 42 - Second outlet; 5 - First fan; 6 - Second fan; 7 - First valve; 8 - Second valve; 9 - Gas distributor, 91 - Air duct, 92 - First gas manifold box, 93 - Distribution pipe, 94 - Second gas manifold box; 10 - Conveyor roller; 11 - Recovery system; 12 - Chilled water supply and return pipeline; 13 - Chilled water recovery pipeline; 14 - Third valve; 15 - First tail gas discharge pipeline; 16 - Second tail gas discharge pipeline; 17 - Upper partition; 18 - Lower partition. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present utility model will be further described below in conjunction with the embodiments shown in the accompanying drawings.

[0030] Refer to Figures 1 to 4 the dichloromethane recovery device of , the device includes a drying furnace, a condenser 3, and a gas-liquid separator 4. The drying furnace includes a first working area 1 and a second working area 2 arranged adjacent to each other. The first working area 1 and the second working area 2 are arranged in sequence along the conveying direction of the lithium battery separator. The first working area 1 is communicated with the extraction tank, and the second working area 2 is communicated with the TDO2 section. The lithium battery separator first enters the first working area 1 of the drying furnace after passing through the extraction tank, then enters the second working area 2, and then is sent out and enters the TDO2 section (other processes).

[0031] The first working area 1 has a first air outlet and a second air outlet. The inlet of the condenser 3 is communicated with the first air outlet of the first working area 1. The condenser 3 is used to condense the dichloromethane discharged from the first air outlet of the first working area 1. The gas-liquid separator 4 is used to separate the gas and liquid of the dichloromethane liquefied by the condenser 3. The gas-liquid separator 4 has an inlet, a first outlet 41 and a second outlet 42. The first outlet 41 is located at the top, and the second outlet 42 is located at the bottom. The inlet of the gas-liquid separator 4 is communicated with the outlet of the condenser 3. The first outlet 41 of the gas-liquid separator 4 is communicated with the inlet of the first working area 1. The second outlet 42 of the gas-liquid separator 4 is used to discharge the dichloromethane liquid (the separated dichloromethane droplets are collected by the wire mesh demister in the gas-liquid separator 4 and collected at the bottom of the tank. When the set liquid level height is reached, the solvent pump starts, and the dichloromethane is sent out for recovery). That is, the dichloromethane gas after gas-liquid separation enters the first working area 1, and the dichloromethane liquid is discharged and recovered. That is, the circulation of dichloromethane gas among the drying furnace, the condenser 3 and the gas-liquid separator 4 is realized.

[0032] A first fan 5 is arranged between the inlet of the condenser 3 and the first air outlet of the first working area 1. A second fan 6 is arranged between the first outlet 41 of the gas-liquid separator 4 and the inlet of the first working area 1. A first valve 7 is arranged on the pipeline communicating the first air outlet of the first working area 1 and the first fan 5. A second valve 8 is arranged on the pipeline communicating the second fan 6 and the inlet of the first working area 1.

[0033] In the first working area 1 and the second working area 2 of this example, there are heating rollers for conveying and heating the diaphragm. The boiling point of dichloromethane is 39.8°C, and the temperature of the drying hot air in the drying furnace is 70°C. The lithium battery diaphragm is dried by the hot air. The air knife in the drying furnace acts on the diaphragm, and the dichloromethane on the diaphragm continuously volatilizes. Since the density of dichloromethane is heavier than air, it sinks downward and is pumped by the first fan 5 to the condenser 3 to condense part of the dichloromethane. Then, after passing through the gas-liquid separator 4, the dichloromethane gas enters the first working area 1 again. The dichloromethane in the first working area 1 acts on the diaphragm through the air knife again, and so on. By using the concentration difference and the circulation volume, the dichloromethane is continuously removed, and at the same time, the heating roller supplements the heating to accelerate the volatilization of dichloromethane. After the diaphragm is dried in the first working area 1, most of the dichloromethane has been removed. When the diaphragm passes through the hot roller and the outlet air knife in the second working area 2 for further drying, the amount of dichloromethane on the diaphragm is extremely small.

[0034] In this example, the first working area 1 and the second working area 2 are separated by a partition. The partition includes an upper partition 17 and a lower partition 18. Both the upper partition 17 and the lower partition 18 extend in the vertical direction. The upper partition 17 is located above the lower partition 18. The upper partition 17 abuts against the upper side wall inside the drying furnace, and the lower partition 18 abuts against the lower side wall inside the drying furnace. There is a gap between the upper partition 17 and the lower partition 18 for the conveying roller for conveying the diaphragm to move. By setting the partition, there is only a small gap between the first working area 1 and the second working area 2. The first working area 1 and the second working area 2 are relatively closed, and the amount of dichloromethane overflowing from the first working area 1 to the second working area 2 is small.

[0035] Under the action of the circulation of dichloromethane gas among the drying furnace, the condenser 3 and the gas-liquid separator 4 and the partition, the concentration of dichloromethane in the first working area 1 is continuously increased. The concentration in the first working area 1 is significantly higher than that in the second working area 2. After circulating for a period of time, when the concentration in the first working area 1 is increased to a certain range of concentration values (such as above 300,000 ppm), the condenser 3 can use 7°C chilled water instead of -40°C chilled water, which can greatly save energy and reduce costs.

[0036] In this example, if there is no partition in the drying furnace 1, it is equivalent to having only one cavity. The concentration of dichloromethane in the drying furnace 1 is low, and it is difficult to condense dichloromethane. Even if dichloromethane is condensed, the amount of condensed dichloromethane is extremely low.

[0037] When the first working area 1 and the second working area 2 are separated by a partition, the dichloromethane in the first working area 1 is processed by the first fan 5, condenser 3, gas-liquid separator 4, and second fan 6 of the system and then sent back into the first working area 1. In this way, the concentration of dichloromethane in the first working area 1 gradually increases. After a certain period of time, it finally reaches a certain value, such as greater than or equal to 300,000 ppm, and a preferred range is 300,000 ppm to 500,000 ppm. At this time, the dichloromethane in the first working area 1 is sent to the condenser 3 by the first fan 5. After being cooled by chilled water, a large amount of dichloromethane condensate appears. The material after cooling and condensation is a gas-liquid two-phase flow, which is transported through the connecting pipe to the gas-liquid separator 4. The gas separated by the gas-liquid separator 4 flows out from the first outlet 41 of the gas-liquid separator 4 into the first working area 1, the dichloromethane content tends to be stable, and the gas phase in the first working area 1 inside the drying furnace tends to be balanced.

[0038] In some embodiments, the volume of the first working area 1 is less than or equal to the volume of the second working area 2, which can reduce the volume of the first working area 1 and enable the concentration of dichloromethane in the first working area 1 to increase more rapidly.

[0039] In this example, a first tail gas discharge pipeline 15 is provided at the second air outlet of the first working area 1. The dichloromethane gas discharged from the second air outlet of the first working area 1 passes through the first tail gas discharge pipeline 15 to the adsorption device (the adsorption device is communicated with the first tail gas discharge pipeline 15); the second working area 2 has an air outlet, and a second tail gas discharge pipeline 16 is provided at the air outlet of the second working area 2. The gas discharged from the air outlet of the second working area 2 passes through the second tail gas discharge pipeline 16 to the adsorption device (the adsorption device is communicated with the second tail gas discharge pipeline 16). Less dichloromethane gas enters the activated carbon adsorption device, and then the activated carbon adsorption device absorbs the dichloromethane gas, which can reduce the workload of the activated carbon adsorption device and improve the service life of the activated carbon adsorption device.

[0040] In some embodiments, the adsorption device is communicated with the connection point of one end of the first tail gas discharge pipeline 15 and one end of the second tail gas discharge pipeline 16, and the dichloromethane gas discharged from the first tail gas discharge pipeline 15 and the dichloromethane gas discharged from the second tail gas discharge pipeline 16 both enter the adsorption device.

[0041] In some embodiments, a gas distributor 9 is arranged in the first working area 1. The gas distributor 9 is used to divert the methylene chloride gas in the first working area 1 to the first fan 5. The gas distributor 9 includes an air draft pipe 91, a first gas manifold 92, a distribution pipe 93, and a second gas manifold 94. There are two air draft pipes 91. One end of one air draft pipe 91 is connected to the first fan 5 through a pipeline, and one end of the other air draft pipe 91 faces into the first working area 1 (the methylene chloride gas in the first working area 1 enters the air draft pipe 9 through this end). The other ends of the two air draft pipes 91 are respectively connected to the first gas manifold 92 and the second gas manifold 94. The opposite ends of the distribution pipe 93 are respectively connected to the first gas manifold 92 and the second gas manifold 94. The two air draft pipes 91 can be located on the same side of the first gas manifold 92 and the second gas manifold 94. Multiple distribution pipes 93 can be arranged, and the multiple distribution pipes 93 can be arranged in parallel. The gas distributor 9 has a simple structure, uniform distribution, controls the internal wind field, reduces disturbance, and ensures the quality of the diaphragm.

[0042] In this example, the first fan 5 and the second fan 6 are variable-frequency fans. The frequency of the fans can be controlled by a frequency converter to adjust the air volume of the conveyed air, and finally adjust the condensation recovery amount of methylene chloride. An efficient gas-liquid separation structure can be arranged inside the gas-liquid separator 4 to intercept and recover as much methylene chloride condensate as possible.

[0043] In this example, the condenser 3 is a plate condenser. Chilled water at 7°C under 0.3 Mpa is used to cool the methylene chloride gas, which is convenient and easy to implement. The chilled water at 7°C is a conventional cold source, and each factory is equipped with it, and there is no need to obtain it through additional means.

[0044] See Figure 1 , the condenser 3 has a first inlet 31, a second inlet 32, a first liquid outlet 33, and a second liquid outlet 34. The device further includes a chilled water supply pipeline 12 and a chilled water recovery pipeline 13. The first inlet 31 of the condenser 3 is connected to the first air outlet of the first working area 1. The second liquid outlet 34 of the condenser 3 is connected to the gas-liquid separator 4. The second inlet 32 of the condenser 3 is connected to the chilled water supply pipeline 12. The first liquid outlet 33 of the condenser 3 is connected to the chilled water recovery pipeline 13.

[0045] The device further includes a recovery system 11 which is communicated with the second outlet 42 of the gas-liquid separator 4. The recovery system 11 is used to recover the dichloromethane liquid discharged from the second outlet 42 of the gas-liquid separator 4. A material transfer pump is arranged between the recovery system 11 and the second outlet 42 of the gas-liquid separator 4. The dichloromethane gas discharged from the first gas outlet of the first working area 1 of the drying furnace passes through the condenser 3 and is cooled by 7°C chilled water, condensing part of the dichloromethane. After being separated by the gas-liquid separator 4, the dichloromethane gas enters the first working area 1 of the drying furnace through the first outlet 41 of the gas-liquid separator 4, and the dichloromethane liquid enters the recovery system 11 through the second outlet 42 of the gas-liquid separator 4. The recovery system 11 in this example is a technical means well-known to those skilled in the art.

[0046] The device further includes a heater which is arranged between the first outlet 41 of the gas-liquid separator 4 and the inlet of the first working area 1 of the drying furnace, preferably arranged on the pipeline communicated between the second blower 6 and the inlet of the first working area 1. The dichloromethane gas after gas-liquid separation enters the first working area 1 after being heated by the heater and continues to act on the diaphragm in the first working area 1 through the air knife.

[0047] In this example, the connecting pipelines between the first working area 1 of the drying furnace and the condenser 3, between the condenser 3 and the gas-liquid separator 4, and between the gas-liquid separator 4 and the first working area 1 of the drying furnace are all combinations of food-grade stainless steel pipes and hoses, and are externally coated with rubber and plastic for cold insulation.

[0048] The method for realizing dichloromethane recovery by using the dichloromethane recovery device in this example includes the following:

[0049] In the initial state, the first valve 7 and the second valve 8 are in the closed state; when in the working state, the first valve 7 and the second valve 8 are opened, and the condenser 3, the gas-liquid separator 4, the first blower 5, and the second blower 6 are started. In the drying furnace, the lithium battery diaphragm is dried by hot air, and the air knife in the drying furnace acts on the diaphragm, and the dichloromethane on the diaphragm volatilizes. The dichloromethane gas is discharged from the first gas outlet of the first working area 1 and enters the condenser 3. After being condensed by the condenser 3, the liquefied dichloromethane enters the gas-liquid separator 4. After gas-liquid separation by the gas-liquid separator 4, the dichloromethane gas enters the first working area 1, and the dichloromethane liquid is discharged from the second outlet 42 of the gas-liquid separator 4. The concentration of dichloromethane in the first working area 1 is higher than that in the second working area 2. In this way, by repeating the cycle, using the concentration difference and the circulation volume, the dichloromethane is continuously carried out.

[0050] Among them, in the first working area 1, the dichloromethane on the diaphragm is gradually removed. Finally, when the diaphragm passes through the heating roller in the second working area 2, the dichloromethane on the diaphragm can be completely removed.

[0051] By repeating this process, the concentration of dichloromethane in the first working area 1 of the drying furnace is continuously increased until the concentration range of dichloromethane in the first working area 1 reaches 300,000 ppm to 500,000 ppm. The vacuum degree of the first working area 1 is less than that of the second working area 2, establishing an equilibrium between the tail gas pressure and the dichloromethane concentration in the drying furnace.

[0052] The dichloromethane gas in the first working area 1 then flows through the second gas outlet to the activated carbon fiber adsorption device, and the dichloromethane gas in the tail gas of the second working area 2 flows through the outlet to the activated carbon fiber adsorption device. Since dichloromethane is partially condensed, the content of dichloromethane flowing to the activated carbon fiber adsorption device is reduced, effectively reducing the load of the existing activated carbon fiber adsorption device, ensuring the adsorption efficiency, and at the same time ensuring the service life of the activated carbon fiber adsorption device.

[0053] The advantages of the dichloromethane recovery device in this example are as follows: on the premise of ensuring the quality of the diaphragm in the current production line, recovering dichloromethane in the exhaust gas of the drying process section at a lower cost, reducing the content of dichloromethane in the discharged exhaust gas, reducing the load of the KF gas recovery device by more than 15% - 20%, and saving the consumption of public utilities such as steam, circulating water, and chilled water. Especially when the gas recovery is operating under overloaded conditions, the commissioning of the device in this example can reduce the load in a more economical and efficient manner, save energy and reduce emissions, reduce the overall consumption, and at the same time extend the service life of the activated carbon fiber adsorption core of the activated carbon fiber adsorption device, achieving the goals of environmental protection and cost reduction and efficiency improvement.

[0054] The above embodiments are only used to illustrate the technical concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A dichloromethane recovery device, characterized in that, The device comprises: A drying furnace, wherein the drying furnace is used for drying the diaphragm, and the drying furnace comprises a first working area and a second working area sequentially arranged along the conveying direction of the diaphragm, and the first working area has a first air outlet; A condenser, wherein the inlet of the condenser is connected to the first gas outlet of the first working area, and the condenser is used to condense the dichloromethane discharged through the first gas outlet of the first working area; A gas-liquid separator, the gas-liquid separator is used to separate the dichloromethane liquefied by the condenser into gas and liquid, the gas-liquid separator has an inlet, a first outlet and a second outlet, the inlet of the gas-liquid separator is connected to the outlet of the condenser, the first outlet of the gas-liquid separator is connected to the inlet of the first working area, and the second outlet of the gas-liquid separator is used to discharge the dichloromethane liquid.

2. The dichloromethane recovery device according to claim 1, characterized in that: The first working area and the second working area are separated by a partition, and the partition includes an upper partition and a lower partition. The upper partition is located above the lower partition, and the upper partition is connected to the upper side wall of the drying furnace. The lower partition is connected to the lower side wall of the drying furnace. There is a gap between the upper partition and the lower partition for the conveying roller of the diaphragm to move.

3. The dichloromethane recovery device according to claim 1, characterized in that: A first fan is arranged between the inlet of the condenser and the first air outlet of the first working area, and a second fan is arranged between the first outlet of the gas-liquid separator and the inlet of the first working area.

4. The dichloromethane recovery device according to claim 3, characterized in that: A first valve is provided on the pipeline connecting the first air outlet of the first working area and the first fan, and a second valve is provided on the pipeline connecting the second fan and the first outlet of the gas-liquid separator.

5. The dichloromethane recovery device according to claim 4, characterized in that: A gas distributor is provided in the first working area, and the gas distributor is used to guide the dichloromethane gas in the first working area to the first fan. The gas distributor includes an induced draft pipe, a first gas junction box, a distribution pipe, and a second gas junction box. One end of the induced draft pipe is connected to the first fan through a pipeline, and the other end of the induced draft pipe is connected to the first gas junction box. The opposite ends of the distribution pipe are respectively connected to the first gas junction box and the second gas junction box.

6. The dichloromethane recovery device according to claim 1, characterized in that: The device also includes a recovery system, which is communicated with the second outlet of the gas-liquid separator and is used to recover the dichloromethane liquid discharged from the second outlet of the gas-liquid separator.

7. The dichloromethane recovery device according to claim 1, characterized in that: The condenser uses 7°C chilled water.

8. The dichloromethane recovery device according to claim 1, characterized in that: The volume of the first working area is less than or equal to the volume of the second working area.

9. The dichloromethane recovery device according to claim 1, characterized in that: The first working area also has a second air outlet, and the second air outlet of the first working area is provided with a first exhaust gas exhaust pipeline.

10. The dichloromethane recovery device according to claim 1, characterized in that: The condenser is a plate condenser.

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