A process for recovering dichloromethane vapors

Abstract

This invention discloses a process for recovering dichloromethane volatile gas, comprising the following steps: impurity removal, cooling, adsorption, desorption, drying and cooling, and condensation recovery. The activated carbon fiber adsorber includes three adsorption / desorption tanks arranged at equal intervals, with a fixed top plate on the top of the three tanks. An adsorption / desorption adjustment assembly is installed inside each tank, comprising multiple rotating plates equidistantly arranged on the inner side of the tank. Multiple support frames are fixedly connected in a circumferential array on the rotating plates. Multiple carbon fiber filling layers are equidistantly slidably arranged on the inner side of the support frames. The carbon fiber filling layers can be freely compressed or stretched to change their porosity. This design, by stretching and compressing the carbon fiber filling layers during the adsorption and desorption stages, changes the porosity of the carbon fiber filling layers, resulting in a more uniform gas distribution, significantly improving the utilization rate of the adsorbent, reducing dead zones formed during the desorption process, and improving drying efficiency.

Description

Technical Field

[0001] This invention relates to the field of dichloromethane recovery technology, and more particularly to a process for recovering dichloromethane volatile gas. Background Technology

[0002] Dichloromethane, an important organic solvent, is widely used in the production processes of pharmaceuticals, chemicals, and electronics. Due to its low boiling point and high volatility, dichloromethane generates a large amount of volatile gas during its production and use. Currently, industrial treatment of dichloromethane volatile gas typically employs activated carbon fiber adsorption and recovery technology. This process utilizes the excellent adsorption properties of activated carbon fibers for dichloromethane to capture and enrich the dichloromethane in the volatile gas, and then achieves solvent recovery and reuse through steps such as high-temperature steam desorption and condensation separation.

[0003] In existing fixed-bed adsorbers, since the carbon fiber filling layer is fixed and cannot be stretched or compressed, when the cooled and purified gas enters from the bottom of the adsorption tank, the concentration of dichloromethane in the gas is distributed in a state of low at the top and high at the bottom. The carbon fiber layer at the bottom comes into contact with the high concentration of gas first and quickly becomes saturated. As the gas flows upward, the concentration gradually decreases. The adsorption capacity of the entire bed is forced to terminate prematurely before the carbon fiber layer at the top reaches saturation, resulting in a low adsorbent utilization rate. During the desorption process, high-temperature steam enters from the top and needs to penetrate multiple layers of carbon fiber filling to reach the bottom. Due to the large heat capacity and heat exchange area of ​​the carbon fiber layer, the steam will gradually cool down during the penetration process due to heat loss and condensation. By the time it reaches the bottom, the heat is severely insufficient, which means that the dichloromethane in the bottom carbon fiber layer cannot be effectively desorbed, forming a desorption dead zone and shortening the service life of the adsorbent. Therefore, in order to solve the above problems, a dichloromethane volatile gas recovery process is proposed. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a process for recovering dichloromethane volatiles.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A process for recovering dichloromethane volatile gas includes the following steps: Step 1: Impurity removal. The volatile gas containing dichloromethane is passed through a filter to remove particulate impurities and obtain purified gas. Step 2: Cooling down. The purified gas is passed into a surface cooler to cool down, while some condensate is separated and removed, and some dichloromethane liquid is precipitated to obtain cooled purified gas. Step 3: Adsorption. The cooled and purified gas is passed into a single-stage adsorption system consisting of three activated carbon fiber adsorbers. The dichloromethane in the cooled and purified gas is adsorbed by the activated carbon fibers, and the purified exhaust gas meets the emission standards. Step 4: Desorption. Saturated water vapor after depressurization is introduced into the activated carbon fiber adsorber that was saturated with adsorption in Step 2 to heat and purge the activated carbon fiber layer, thereby desorbing the adsorbed dichloromethane and forming a mixed steam containing water vapor and dichloromethane vapor. Step 5: Drying and cooling. After the desorption in step 3 is completed, fresh cold air is introduced into the adsorber to purge it and cool and dry the desorbed activated carbon fiber layer. Step 6: Condensation and recovery. The mixed vapor generated in Step 3 is passed into a condenser for condensation to obtain a mixed liquid. At the same time, the condensate flowing out of the bottom of the adsorber during the desorption process in Step 3 is cooled by a deep cooler and also sent to the separation device.

[0006] The activated carbon fiber adsorber includes three adsorption-desorption tanks arranged at equal intervals. The top of the three adsorption-desorption tanks is provided with a fixed top plate. An adsorption-desorption adjustment component is provided inside the adsorption-desorption tank. The adsorption-desorption adjustment component includes multiple rotating plates that are equidistantly rotatably arranged inside the adsorption-desorption tank. Multiple support frames are fixedly connected in a circumferential array on the rotating plates. Multiple carbon fiber filling layers are equidistantly slidably arranged inside the support frames. The carbon fiber filling layers can be freely compressed or stretched to change their porosity.

[0007] The above technical solution further includes: A recovery pipe and a discharge pipe are fixedly installed on the top outer wall of the adsorption-desorption tank, and a desorption gas outlet pipe and a drying gas outlet pipe are fixedly installed on the bottom of the adsorption-desorption tank.

[0008] The adsorption regulating assembly also includes multiple bearing seats fixedly installed on the top of the fixed top plate. A first motor is fixedly installed on the outer side of the bearing seats. The output end of the first motor is driven by a transmission main bevel gear. The fixed top plate and the adsorption / desorption tank are rotatably connected by a first transmission shaft. One end of the first transmission shaft extending to the inner side of the bearing seat is fixedly connected to a transmission driven gear. The transmission driven gear meshes with the transmission main bevel gear. A second motor is fixedly connected to the top of the bearing seat. The output end of the second motor is fixedly connected to the second transmission shaft.

[0009] The inner wall of the suction-extraction tank is fixedly connected with sealing sliding shafts at equal intervals. The rotating plate slides relative to the sealing sliding shafts. The inner side of the support frame is symmetrically fixedly connected with slide rails. A middle partition is slidably arranged between the two slide rails. Several sliding partitions are equidistantly arranged on both sides of the middle partition. The sliding partitions slide relative to the slide rails. Side partitions are fixedly connected to both inner sides of the rotating plate. Carbon fiber filling layers are filled between the side partitions and the sliding partitions, between two adjacent sliding partitions, and between the middle partition and the sliding partitions.

[0010] Telescopic frames are fixedly connected between the central partition, side partitions, and several sliding partitions. Two telescopic frames are centrally symmetrically distributed. Bearing plates are symmetrically fixedly connected to the bottom of the support frame. Limiting sliding shafts are symmetrically fixedly connected between the two bearing plates. A reciprocating screw is rotatably connected between the two bearing plates. A crescent-shaped slider is threaded onto the reciprocating screw. The crescent-shaped slider is fixedly connected to the bottom of the central partition and slides relative to the two limiting sliding shafts.

[0011] The first drive shaft has multiple sets of rotating holes equidistantly opened on its outer side. Each set of rotating holes has multiple holes arranged in a circular array. The rotating holes are rotatably connected to the reciprocating lead screw. The second drive shaft has multiple adjusting bevel gears fixedly connected at equal intervals on its outer side. The end of the reciprocating lead screw extending to the inner side of the first drive shaft is fixedly connected to an adjusting bevel gear. The adjusting bevel gears mesh with the multiple adjusting bevel gears.

[0012] Multiple reciprocating lead screws at the same height use the same pitch and number of turns. The reciprocating lead screws at different heights have different thread specifications to change the compression and elongation of the carbon fiber filler layer at different heights.

[0013] The top of the desorption / desorption tank is fixedly connected to a desorption inlet ring. Multiple desorption inlet pipes are installed in a continuous circumferential array on the outer side of the desorption inlet ring. The desorption inlet ring is rotatably connected to a first drive shaft. A desorption channel is opened through the bottom end of the first drive shaft. A desorption interface sleeve is fixedly connected to the outer wall of the inner side of the first drive shaft. Multiple desorption nozzles are installed in a continuous circumferential array on the outer side of the desorption interface sleeve.

[0014] The bottom of the suction and desorption tank is fixedly connected to a purified gas inlet ring. Multiple purified gas inlet pipes are installed in a continuous circumferential array on the outer side of the purified gas inlet ring. The purified gas inlet ring is rotatably connected to the first drive shaft. A purified gas channel is opened through the bottom end of the first drive shaft. A purified gas interface sleeve is fixedly connected to the outer wall of the inner side of the suction and desorption tank. Multiple purified gas nozzles are installed in a continuous circumferential array on the outer side of the purified gas interface sleeve.

[0015] The present invention has the following beneficial effects: In this invention, the design uses independent control of the first and second motors to change the porosity of the carbon fiber filling layer by stretching and compressing during the adsorption stage, thereby making the gas distribution more uniform, extending the contact time, and significantly improving the utilization rate and adsorption efficiency of the adsorbent.

[0016] In this invention, during the desorption stage, the carbon fiber filler layer is repeatedly squeezed and stretched to assist desorption with mechanical action. At the same time, the spiral airflow enhances the steam penetration ability, eliminates the desorption dead zone, and shortens the regeneration cycle. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a dichloromethane volatile gas recovery process proposed in this invention; Figure 2 This is a schematic diagram of the overall structure of the activated carbon fiber adsorber in this invention; Figure 3 This is a top view of the internal structure of the suction-extraction tank in this invention; Figure 4 This is a schematic diagram of the internal structure of the suction-extraction tank in this invention, viewed from below. Figure 5 This is a schematic diagram showing the positional relationship between the first motor and the second motor in this invention; Figure 6 for Figure 5 Enlarged schematic diagram of the structure at point A in the middle; Figure 7 This is a schematic diagram of the adsorption / desorption adjustment component in this invention; Figure 8 for Figure 7 Enlarged schematic diagram of the structure at point B; Figure 9 This is a schematic diagram of the structure of the side partition, sliding partition, middle partition, and carbon fiber filling layer in this invention; Figure 10 This is a schematic diagram of the purified gas inlet pipe, purified gas nozzle, and purified gas channel structure in this invention.

[0018] In the diagram: 1. Fixed top plate; 2. Suction / desorption tank; 3. First motor; 4. Desorption inlet ring; 5. Purified gas inlet ring; 6. Desorption gas outlet pipe; 7. Drying gas outlet pipe; 20. Recovery pipe; 21. Discharge pipe; 30. Support frame; 302. Slide rail; 31. Sealing slide shaft; 32. Rotating plate; 33. Second motor; 34. Second drive shaft; 35. Bearing seat; 36. First drive shaft; 360. Rotating hole; 37. Drive main bevel gear; 38. Driven gear; 39. Side 390. Partition plate; 391. Sliding partition plate; 310. Telescopic frame; 311. Bearing plate; 312. Reciprocating lead screw; 313. Limiting slide shaft; 314. Adjusting bevel gear plate; 315. Adjusting bevel gear; 316. Crescent-shaped slider; 317. Carbon fiber filling layer; 40. Desorption channel; 41. Desorption interface sleeve; 42. Desorption nozzle; 43. Desorption inlet pipe; 50. Purified gas inlet pipe; 51. Purified gas nozzle; 52. Purified gas interface sleeve; 53. Purified gas channel; Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 like Figure 1 As shown, the present invention proposes a dichloromethane volatile gas recovery process, which includes the following steps: Step 1: Impurity removal. The volatile gas containing dichloromethane is passed through a filter to remove particulate impurities and obtain purified gas. Step 2: Cooling. The purified gas is passed into a surface cooler to cool down to below 35°C. At the same time, some condensate is separated and removed, and some dichloromethane liquid is precipitated. The resulting mixture enters the separation device, and the cooled purified gas enters the subsequent process. Step 3: Adsorption. The cooled and purified gas is passed into a single-stage adsorption system consisting of three activated carbon fiber adsorbers. The system is controlled so that at any given time, two adsorbers are connected in parallel for adsorption, and one adsorber is used for regeneration. The dichloromethane in the cooled and purified gas is adsorbed by the activated carbon fibers, and the purified exhaust gas is then emitted. Step 4: Desorption. For the activated carbon fiber adsorber saturated in Step 2, saturated water vapor after pressure reduction is introduced through a self-regulating pressure regulating valve to heat and purge the activated carbon fiber layer, thereby desorbing the adsorbed dichloromethane and forming a mixed steam containing water vapor and dichloromethane vapor.

[0021] Step 5: Drying and cooling. After the desorption in step 3 is completed, fresh cold air is introduced into the adsorber to purge it and cool and dry the desorbed activated carbon fiber layer. Step Six: The mixed vapor generated in Step Three is passed into a condenser for condensation to obtain a mixed liquid; at the same time, the condensate flowing out of the bottom of the adsorber during the desorption process in Step Three is cooled by a deep cooler and also sent to the separation device; the mixed liquid and the cooled condensate are separated into layers in the separation device by using density difference to obtain the upper layer of separated water and the lower layer of liquid dichloromethane; the separated dichloromethane is pumped into a solvent storage tank for recycling.

[0022] Example 2 like Figures 2-9 As shown, based on Embodiment 1, in this embodiment, the activated carbon fiber adsorber includes three adsorption / desorption tanks 2 arranged at equal intervals. The top of the three adsorption / desorption tanks 2 is provided with a fixed top plate 1. The adsorption / desorption adjustment assembly is provided inside the adsorption / desorption tank 2. The adsorption / desorption adjustment assembly includes multiple rotating plates 32 rotatably arranged at equal intervals on the inner side of the adsorption / desorption tank 2. Multiple support frames 30 are fixedly connected in a circumferential array on the rotating plates 32. Multiple carbon fiber filling layers 317 are slidably arranged at equal intervals on the inner side of the support frames 30. The carbon fiber filling layers 317 can be freely compressed or stretched to change their porosity.

[0023] A recovery pipe 20 and a discharge pipe 21 are fixedly installed on the top outer wall of the suction-desorption tank 2, and a desorption gas outlet pipe 6 and a drying gas outlet pipe 7 are fixedly installed on the bottom of the suction-desorption tank 2.

[0024] In this design, the cooling and purification gas flow is powered by an external negative pressure machine. Two of the three adsorption and desorption tanks 2 always carry out the adsorption process, while one adsorber performs the desorption process. Furthermore, the cooled and purified gas first undergoes an adsorption process. It flows from the main pipeline of the cooled and purified gas through multiple purified gas inlet pipes 50 into the adsorption-desorption tank 2. The cooled and purified gas passes through the carbon fiber filling layer 317, where dichloromethane is captured and remains in the porous structure of the carbon fiber filling layer 317. The purified exhaust gas is discharged through the discharge pipe 21. A sensor is installed on the discharge pipe 21 to detect the concentration of dichloromethane. When the concentration in the discharge pipe 21 is too high, the valve on the discharge pipe 21 is closed, and the valve on the recovery pipe 20 is opened. The exhaust gas returns from the recovery pipe 20 back into the main pipeline that transports the cooled and purified gas.

[0025] Furthermore, during the desorption process, a three-way valve is used between the high-temperature steam pipeline, the fresh cold air pipeline, and the desorption inlet pipe 43. That is, the desorption inlet pipe 43 can be filled with both high-temperature steam and fresh cold air. First, after the high-temperature steam enters the adsorption-desorption tank 2, it heats and purges the carbon fiber filling layer 317, causing the adsorbed dichloromethane to desorb. A mixed steam containing water vapor and dichloromethane vapor is then discharged from the desorption gas outlet pipe 6 and enters the condenser. After the above work is completed, the three-way valve is switched to introduce fresh cold air into the adsorption-desorption tank 2 to dry the carbon fiber filling layer 317. The dried gas is then discharged from the dried gas outlet pipe 7.

[0026] Furthermore, in traditional adsorption processes, the carbon fiber layers are fixed and cannot be stretched or compressed. Therefore, when the cooled and purified gas enters from the bottom of the adsorption tank, the concentration of dichloromethane in the gas is the highest. The bottom carbon fiber layer first comes into contact with the high-concentration gas and quickly becomes saturated. As the gas flows upward, the dichloromethane concentration gradually decreases, reaching extremely low levels at the top. The top carbon fiber layer is far from saturated and is forced to stop adsorption because the bottom carbon fiber layer, once saturated, ceases adsorption. As adsorption continues, each carbon fiber layer becomes increasingly saturated. When only one carbon fiber layer is adsorbing, dichloromethane begins to appear in the outlet gas, i.e., breakthrough occurs.

[0027] Furthermore, during the desorption process, high-temperature steam cannot completely penetrate the traditional multi-layer carbon fiber layer. During the penetration process, the steam will lose heat and condense, resulting in excessive heat loss when it reaches the bottom, leading to low and uneven desorption efficiency. This design can solve the above problems by continuously compressing and elongating the carbon fiber filling layer 317.

[0028] Example 3 like Figure 6 and Figure 10 As shown, based on the above embodiments, in this embodiment, a desorption inlet ring 4 is fixedly connected to the top of the suction-desorption tank 2, and multiple desorption inlet pipes 43 are installed through the outer circumferential array of the desorption inlet ring 4. The desorption inlet ring 4 is rotatably connected to the first drive shaft 36. A desorption channel 40 is opened through the bottom end of the first drive shaft 36. A desorption interface sleeve 41 is fixedly connected to the outer wall of the inner side of the suction-desorption tank 2. Multiple desorption nozzles 42 are installed through the outer circumferential array of the desorption interface sleeve 41.

[0029] A purified gas inlet ring 5 is fixedly connected to the bottom of the suction and desorption tank 2. Multiple purified gas inlet pipes 50 are installed in a continuous circumferential array on the outer side of the purified gas inlet ring 5. The purified gas inlet ring 5 is rotatably connected to the first drive shaft 36. A purified gas channel 53 is opened through the bottom end of the first drive shaft 36. A purified gas interface sleeve 52 is fixedly connected to the outer wall of the inner side of the first drive shaft 36. Multiple purified gas nozzles 51 are installed in a continuous circumferential array on the outer side of the purified gas interface sleeve 52.

[0030] Furthermore, during the adsorption process, the cooled and purified gas enters the purified gas inlet ring 5 from the purified gas inlet pipe 50. The purified gas inlet ring 5 is interconnected with the purified gas channel 53. Then, it enters the purified gas nozzle 51 from the purified gas interface sleeve 52. The purified gas nozzle 51 can rotate synchronously with the first drive shaft 36 to form a spiral airflow and improve the uniformity of the gas.

[0031] Furthermore, during the desorption process, a high-temperature steam pipe or a fresh cold air pipe enters the desorption inlet ring 4 from the desorption inlet pipe 43. The desorption inlet ring 4 is interconnected with the desorption channel 40, and then enters the desorption nozzle 42 from the desorption interface sleeve 41. The desorption nozzle 42 can rotate synchronously with the first drive shaft 36 to form a spiral airflow. On the one hand, this can improve the penetration ability of the airflow. On the other hand, the desorption nozzle 42 is a circumferential design, which can improve the uniformity of the gas.

[0032] Example 4 like Figures 3-5 , Figures 7-9 As shown, based on the above embodiments, in this embodiment, the adsorption adjustment assembly further includes multiple bearing seats 35 fixedly installed on the top of the fixed top plate 1. A first motor 3 is fixedly installed on the outer side of the bearing seat 35. The output end of the first motor 3 is connected to a transmission main bevel gear 37. A first transmission shaft 36 is rotatably connected between the fixed top plate 1 and the adsorption / extraction tank 2. A transmission driven gear 38 is fixedly connected to one end of the first transmission shaft 36 extending to the inner side of the bearing seat 35. The transmission driven gear 38 meshes with the transmission main bevel gear 37. A second motor 33 is fixedly connected to the top of the bearing seat 35. The output end of the second motor 33 is fixedly connected to the second transmission shaft 34.

[0033] Sealing slide shafts 31 are fixedly connected at equal intervals on the inner wall of the suction-extraction tank 2. The rotating plate 32 slides relative to the sealing slide shafts 31. Slide rails 302 are symmetrically fixedly connected to the inner side of the support frame 30. A middle partition 391 is slidably arranged between the two slide rails 302. Several sliding partitions 390 are equidistantly arranged on both sides of the middle partition 391. The sliding partitions 390 slide relative to the slide rails 302. Side partitions 39 are fixedly connected to both inner sides of the rotating plate 32. Carbon fiber filling layer 317 is filled between the side partitions 39 and the sliding partitions 390, between two adjacent sliding partitions 390, and between the middle partition 391 and the sliding partitions 390.

[0034] Telescopic frames 310 are fixedly connected between the central partition 391, the side partition 39, and several sliding partitions 390. The two telescopic frames 310 are centrally symmetrically distributed. Bearing plates 311 are symmetrically fixedly connected to the bottom of the support frame 30. Limiting sliding shafts 313 are symmetrically fixedly connected between the two bearing plates 311. A reciprocating screw 312 is rotatably connected between the two bearing plates 311. A crescent-shaped slider 316 is threaded onto the reciprocating screw 312. The crescent-shaped slider 316 is fixedly connected to the bottom of the central partition 391 and slides relative to the two limiting sliding shafts 313.

[0035] Multiple sets of rotating holes 360 are equidistantly provided on the outer side of the first drive shaft 36. Each set of rotating holes 360 has multiple holes and is arranged in a circular array. The rotating holes 360 are rotatably connected to the reciprocating lead screw 312. Multiple adjusting bevel gears 314 are fixedly connected at equal intervals on the outer side of the second drive shaft 34. An adjusting bevel gear 315 is fixedly connected to one end of the reciprocating lead screw 312 that extends to the inner side of the first drive shaft 36. The adjusting bevel gears 314 mesh with the multiple adjusting bevel gears 315.

[0036] Multiple reciprocating lead screws 312 at the same height use the same pitch and number of turns. The reciprocating lead screws 312 at different heights have different thread specifications to change the compression and elongation of the carbon fiber filler layer 317 at different heights.

[0037] Furthermore, regardless of whether it is in the adsorption stage or the desorption stage, the second motor 33 and the first motor 3 can be controlled to work separately to achieve different effects. When the concentration of dichloromethane in the cooled and purified gas is high, the first motor 3 can be controlled to rotate independently. Through the meshing transmission between the transmission gear 38 and the transmission main bevel gear 37, the first transmission shaft 36 is driven to rotate, which drives the support frame 30 to move in a circular motion. At the same time, the second motor 33 is self-locked, and the second transmission shaft 34 remains stationary. Therefore, the adjusting bevel gear disk 314 rotates on the adjusting bevel gear 315 and moves in a circular motion, thereby driving the reciprocating screw 312 to move synchronously. The reciprocating screw 312 drives the middle partition 391 to move repeatedly through the crescent slider 316. The carbon fiber filling layer 317 on both sides of the middle partition 391 is stretched or compressed under the action of the telescopic frame 310, and the movement state of the carbon fiber filling layer 317 on both sides of the middle partition 391 is different.

[0038] Alternatively, when the concentration of dichloromethane is low, the second motor 33 can be controlled independently while the first motor 3 is locked off. At this time, the support frame 30 is stationary, and the carbon fiber filling layers 317 at different heights are repeatedly squeezed and stretched. This design can change the porosity of the carbon fiber filling layer 317, adjust the airflow distribution, and assist in desorption or adsorption.

[0039] Furthermore, since the porosity of the carbon fiber filling layer 317 changes in real time, as the porosity increases, the gas flow rate decreases, the airflow distribution becomes more uniform, and the contact time between the gas and the carbon fiber is extended. As the porosity decreases, the gas is forced to choose a new path to pass through other areas, so that the carbon fibers in the entire bed can be in uniform contact with the gas, which can improve the desorption and adsorption effects.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for recovering dichloromethane volatile gas, characterized in that, Includes the following steps, Step 1: Impurity removal. The volatile gas containing dichloromethane is passed through a filter to remove particulate impurities and obtain purified gas. Step 2: Cooling down. The purified gas is passed into a surface cooler to cool down, while some condensate is separated and removed, and some dichloromethane liquid is precipitated to obtain cooled purified gas. Step 3: Adsorption. The cooled and purified gas is passed into a single-stage adsorption system consisting of three activated carbon fiber adsorbers. The dichloromethane in the cooled and purified gas is adsorbed by the activated carbon fibers, and the purified exhaust gas meets the emission standards. Step 4: Desorption. Saturated water vapor after depressurization is introduced into the activated carbon fiber adsorber that was saturated with adsorption in Step 2 to heat and purge the activated carbon fiber layer, thereby desorbing the adsorbed dichloromethane and forming a mixed steam containing water vapor and dichloromethane vapor. Step 5: Drying and cooling. After the desorption in step 3 is completed, fresh cold air is introduced into the adsorber to purge it and cool and dry the desorbed activated carbon fiber layer. Step 6: Condensation and recovery. The mixed vapor generated in Step 3 is passed into a condenser for condensation to obtain a mixed liquid. At the same time, the condensate flowing out of the bottom of the adsorber during the desorption process in Step 3 is cooled by a deep cooler and also sent to the separation device.

2. The dichloromethane volatile gas recovery process according to claim 1, wherein the activated carbon fiber adsorber comprises three adsorption / desorption tanks (2) arranged at equal intervals, and the tops of the three adsorption / desorption tanks (2) are jointly provided with a fixed top plate (1), characterized in that, The suction-desorption tank (2) is equipped with a suction-desorption adjustment component. The suction-desorption adjustment component includes multiple rotating plates (32) that are equidistantly rotatable on the inner side of the suction-desorption tank (2). Multiple support frames (30) are fixedly connected to the rotating plates (32) in a circumferential array. Multiple carbon fiber filling layers (317) are equidistantly slidably arranged on the inner side of the support frames (30). The carbon fiber filling layers (317) can be freely compressed or stretched to change their porosity.

3. The dichloromethane volatile gas recovery process according to claim 2, characterized in that, A recovery pipe (20) and a discharge pipe (21) are fixedly installed on the top outer wall of the adsorption-desorption tank (2), and a desorption gas outlet pipe (6) and a drying gas outlet pipe (7) are fixedly installed at the bottom of the adsorption-desorption tank (2).

4. The dichloromethane volatile gas recovery process according to claim 2, characterized in that, The adsorption adjustment assembly also includes multiple bearing seats (35) fixedly installed on the top of the fixed top plate (1). A first motor (3) is fixedly installed on the outside of the bearing seat (35). The output end of the first motor (3) is connected to a transmission main bevel gear (37). A first transmission shaft (36) is rotatably connected between the fixed top plate (1) and the adsorption tank (2). A transmission slave gear (38) is fixedly connected to one end of the first transmission shaft (36) extending to the inside of the bearing seat (35). The transmission slave gear (38) meshes with the transmission main bevel gear (37). A second motor (33) is fixedly connected to the top of the bearing seat (35). The output end of the second motor (33) is fixedly connected to the second transmission shaft (34).

5. The dichloromethane volatile gas recovery process according to claim 4, characterized in that, The inner wall of the suction and desorption tank (2) is fixedly connected with sealed sliding shafts (31) at equal intervals. The rotating plate (32) slides relative to the sealed sliding shafts (31). The inner side of the support frame (30) is symmetrically fixedly connected with slide rails (302). A middle partition (391) is slidably arranged between the two slide rails (302). Several sliding partitions (390) are equidistantly arranged on both sides of the middle partition (391). The sliding partitions (390) slide relative to the slide rails (302). Side partitions (39) are fixedly connected to both inner sides of the rotating plate (32). A carbon fiber filling layer (317) is filled between the side partitions (39) and the sliding partitions (390), between two adjacent sliding partitions (390), and between the middle partition (391) and the sliding partitions (390).

6. The dichloromethane volatile gas recovery process according to claim 5, characterized in that, Telescopic frames (310) are fixedly connected between the central partition (391), the side partition (39), and several sliding partitions (390). The two telescopic frames (310) are centrally symmetrically distributed. Bearing plates (311) are symmetrically fixedly connected to the bottom of the support frame (30). Limiting slide shafts (313) are symmetrically fixedly connected between the two bearing plates (311). A reciprocating screw (312) is rotatably connected between the two bearing plates (311). A crescent-shaped slider (316) is threaded onto the reciprocating screw (312). The crescent-shaped slider (316) is fixedly connected to the bottom of the central partition (391) and slides relative to the two limiting slide shafts (313).

7. The dichloromethane volatile gas recovery process according to claim 6, characterized in that, The first drive shaft (36) has multiple sets of rotating holes (360) equidistantly opened on its outer side. Each set of rotating holes (360) has multiple holes and is arranged in a circular array. The rotating holes (360) are rotatably connected to the reciprocating screw (312). The second drive shaft (34) has multiple adjusting bevel gears (314) fixedly connected at equal intervals on its outer side. The end of the reciprocating screw (312) extending to the inner side of the first drive shaft (36) is fixedly connected to an adjusting bevel gear (315). The adjusting bevel gears (314) mesh with the multiple adjusting bevel gears (315).

8. The dichloromethane volatile gas recovery process according to claim 6, characterized in that, The reciprocating screws (312) at the same height have the same pitch and number of turns. The reciprocating screws (312) at different heights have different thread specifications to change the compression and elongation of the carbon fiber filler layer (317) at different heights.

9. The dichloromethane volatile gas recovery process according to claim 2, characterized in that, The top of the suction-desorption tank (2) is fixedly connected to a desorption inlet ring (4). Multiple desorption inlet pipes (43) are installed through the outer circumferential array of the desorption inlet ring (4). The desorption inlet ring (4) is rotatably connected to the first drive shaft (36). A desorption channel (40) is opened through the bottom end of the first drive shaft (36). A desorption interface sleeve (41) is fixedly connected to the outer wall of the inner side of the first drive shaft (36). Multiple desorption nozzles (42) are installed through the outer circumferential array of the desorption interface sleeve (41).

10. The dichloromethane volatile gas recovery process according to claim 2, characterized in that, The bottom of the suction and desorption tank (2) is fixedly connected to a purified gas inlet ring (5). Multiple purified gas inlet pipes (50) are installed in a circular array on the outer side of the purified gas inlet ring (5). The purified gas inlet ring (5) is rotatably connected to the first drive shaft (36). A purified gas channel (53) is opened through the bottom end of the first drive shaft (36). A purified gas interface sleeve (52) is fixedly connected to the outer wall of the inner side of the first drive shaft (36). Multiple purified gas nozzles (51) are installed in a circular array on the outer side of the purified gas interface sleeve (52).

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