Method and device for recovering monochlorodifluoromethane from preparation system

Abstract

The invention discloses a device for recovering monochlorodifluoromethane from a preparation system, which is characterized in that a residual liquid outlet is communicated with a recovery buffer tank (2) through a residual liquid storage tank (1), a liquid phase outlet of the residual liquid storage tank (1) is communicated with an inlet of an alkali liquor desorption tower (6) through a regulating valve (3), a material outlet of a dilute acid storage tank (5) is communicated with an inlet of the alkali liquor desorption tower (6), and a material outlet of the dilute acid storage tank (5) is communicated with a material outlet of the alkali liquor desorption tower (6). An alkali liquor outlet is communicated with a recovery buffer tank (2) through an alkali liquor desorption tower (6), a monochlorodifluoromethane outlet of the recovery buffer tank (2) is communicated with an inlet of a condensation collecting tank (9) through a compressor (8), and the condensation collecting tank (9) is communicated with a finished product storage tank (12) through a recovery pump (4), a water alkali washing system and a rectifying tower (11). The monochlorodifluoromethane stored in the recovery buffer tank (2) is conveyed to a water alkali washing system and then put into a rectifying tower (11) to be refined, and the obtained monochlorodifluoromethane finished product is stored in a finished product storage tank (12).

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for recovering chlorodifluoromethane from a preparation system. Background Art

[0002] Chlorodifluoromethane is a colorless and slightly sweet-smelling substance with a wide range of uses and stable chemical properties. It is mainly used as a refrigerant, a fire extinguishing agent, and a raw material for polytetrafluoroethylene resin. Since the product chlorodifluoromethane can dissolve in acid and alkali solutions and the rectification residue contains chlorodifluoromethane, resulting in a loss of chlorodifluoromethane production, it is basically difficult to reach the theoretical consumption level of chlorodifluoromethane products during the production and preparation of chlorodifluoromethane. Currently, when dealing with F22 in acid and alkali solutions, it can only be sent to the sewage treatment station for treatment in the end; the rectification residue is directly sent to the incineration device for incineration treatment. The above treatment methods are extremely uneconomical, easily cause pollution, and have high production costs. In view of this problem, how to recover chlorodifluoromethane in the F22 preparation system has become an important topic for the sustainable development of the industry. Summary of the Invention

[0003] The present invention provides a method and an apparatus for recovering chlorodifluoromethane from a preparation system, which can effectively treat the residue generated during the preparation of chlorodifluoromethane. The treatment method is economical and reliable, avoiding direct incineration treatment, and preventing environmental pollution.

[0004] The present invention adopts the following technical solutions: A method for recovering chlorodifluoromethane from a preparation system, which includes the following steps: Step 1, collect the rectification residue in the preparation of chlorodifluoromethane by a residue storage tank, use a heating method to vaporize the residue in the residue storage tank, and transport the light-component chlorodifluoromethane to a recovery buffer tank for storage. The liquid phase is sent to an alkali solution analysis tower through a regulating valve to analyze the chlorodifluoromethane in the liquid phase and also send it to the recovery buffer tank for storage; Step 2, store the dilute acid in the preparation of chlorodifluoromethane in a dilute acid storage tank. The gas phase of the dilute acid goes to the alkali solution analysis tower to analyze chlorodifluoromethane and then goes to the recovery buffer tank for storage. Step 3, send the crude product of chlorodifluoromethane in the alkali separator in the preparation of chlorodifluoromethane to the alkali solution analysis tower to analyze chlorodifluoromethane and send it to the recovery buffer tank for storage. At the same time, it serves as the alkali solution of the alkali solution analysis tower, and the alkali solution contains chlorodifluoromethane; Step 4, compress the chlorodifluoromethane stored in the recovery buffer tank in Step 1, the chlorodifluoromethane stored in the recovery buffer tank in Step 2, and the chlorodifluoromethane stored in the recovery buffer tank in Step 3 by a compressor, and transport it to a condensation collection tank for collection. Use a recovery pump to transport the chlorodifluoromethane in the condensation collection tank to a water and alkali washing system to remove acidic substances. Finally, put the deacidified chlorodifluoromethane into a rectification tower for refining to obtain the finished product of chlorodifluoromethane and store it in a finished product storage tank.

[0005] Furthermore, the heat medium in the residual liquid storage tank in Step 1 is hot water heated by steam.

[0006] Furthermore, the dilute acid in Step 2 comes from the water washing tower Ⅰ in the difluorochloromethane production equipment. The water washing tower Ⅰ controls the pressure at 1.25 - 1.35 MPa. The dilute acid is sent to the dilute acid storage tank through the pressure reducing valve Ⅰ, and the pressure is in the atmospheric state. The difluorochloromethane and hydrochloric acid dissolved in the dilute acid are resolved and enter the alkali solution resolving tower to remove acidic substances and recover difluorochloromethane.

[0007] Furthermore, the alkali solution in Step 3 comes from the alkali separator, and the alkali separator controls the pressure at 1.4 - 1.55 MPa; the alkali solution is sent to the alkali solution resolving tower through the pressure reducing valve Ⅱ to resolve the gaseous difluorochloromethane. The pressure of the alkali solution resolving tower is controlled at 1 - 5 kPa, and the temperature is at room temperature.

[0008] Furthermore, the compressor in Step 4 is a two-stage compressor. A pressure regulating valve is set on the pipeline between the compressor and the condensation collection tank. The two-stage compressor uses cooling water as circulating water, 0℃ cold water, -15℃ brine or -35℃ brine. The condensation collection tank is in the form of a combination of a condenser and a storage tank. The refrigerant of the condenser uses -15℃ brine or -35℃ brine. The water washing tower and the alkali washing tower of the water and alkali washing system respectively absorb and remove the HCL and HF gases in the crude difluorochloromethane. The pressures of the water washing tower and the alkali washing tower are controlled at 1.5 - 1.7 MPa, the pressure of the rectifying tower is controlled at 0.8 - 1.3 MPa, the top temperature is controlled at -10 - 10℃, and the bottom temperature is controlled at 30 - 60℃; the purity reaches 99.9%, and the purity of the difluorochloromethane finished product reaches 99.9%, the evaporation residue is less than or equal to 0.02%, the water content is less than or equal to 10 ppm, and the acidity is less than or equal to 0.1 ppm.

[0009] The present invention also discloses a device for recovering chlorodifluoromethane from a preparation system, which includes a residual liquid storage tank, an alkali separator, a dilute acid storage tank, an alkali solution stripping tower, a recovery buffer tank, a compressor, a condensation collection tank, a water and alkali washing system, a rectification tower and a finished product storage tank. The residual liquid outlet of the chlorodifluoromethane preparation device is communicated with the inlet of the residual liquid storage tank. The gas phase outlet of the residual liquid storage tank is communicated with the inlet Ⅰ at the top of the recovery buffer tank. The liquid phase outlet of the residual liquid storage tank is communicated with the inlet of the alkali solution stripping tower through a regulating valve. The dilute acid outlet of the water washing tower Ⅰ in the chlorodifluoromethane preparation device is communicated with the inlet of the dilute acid storage tank through a pressure reducing valve Ⅰ. The material outlet of the dilute acid storage tank is communicated with the inlet of the alkali solution stripping tower. The alkali solution outlet of the alkali separator in the chlorodifluoromethane preparation device is communicated with the inlet of the alkali solution stripping tower through a pressure reducing valve Ⅱ. The outlet of the alkali solution stripping tower is communicated with the inlet Ⅱ on the side of the recovery buffer tank. The chlorodifluoromethane outlet of the recovery buffer tank is connected to the input end of the compressor. The output end of the compressor is communicated with the inlet of the condensation collection tank. The outlet of the condensation collection tank is communicated with the inlet of the water and alkali washing system through a recovery pump. The outlet of the water and alkali washing system is communicated with the finished product storage tank through the rectification tower.

[0010] Furthermore, the alkali solution stripping tower is a packed tower. The tower body diameter of the alkali solution stripping tower is DN600, DN700 or DN800; the height is 9000 - 12000 mm, the tower bottom diameter of the alkali solution stripping tower is 1200 - 1600 mm, and the height is 1600 - 2000 mm.

[0011] Furthermore, the compressor is set as a two-stage compressor, and a pressure regulating valve is installed on the pipeline between the compressor and the condensation collection tank.

[0012] Furthermore, the condensation collection tank includes a collection tank body, and a condenser is installed inside the collection tank body. When the compressed chlorodifluoromethane enters the collection tank body, the chlorodifluoromethane is condensed by the condenser.

[0013] Furthermore, the water and alkali washing system includes a water washing tower and an alkali washing tower, which are connected in series. Among them, the water washing tower and the alkali washing tower adopt a packed tower structure, and the packed material is PP Pall ring, PP Intalox saddle ring or PP flower ring; the diameter of the packed material is φ25, φ38 or φ50.

[0014] The present invention has the following beneficial effects: After adopting the above technical solutions, in the present invention, the rectification residue in the preparation of chlorodifluoromethane, the crude chlorodifluoromethane in the dilute acid and alkali separator are analyzed through an alkali solution analysis tower, and then by using the combined technology of compression, water and alkali washing, and rectification, chlorodifluoromethane is recovered step by step, and the chlorodifluoromethane with qualified product quality is obtained after treatment. In this way, the residue generated in the preparation of chlorodifluoromethane can be effectively treated. The treatment method is economical and reliable, avoiding treatment by direct incineration, preventing environmental pollution, and moreover, the chlorodifluoromethane obtained after treating the waste liquid can be reused, turning waste into treasure, thus effectively reducing the cost of producing chlorodifluoromethane in industrial production and improving the utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 It is a schematic structural diagram of the present invention. EMBODIMENTS

[0017] The following will elaborate on the preferred embodiments of the present invention patent in conjunction with the drawings, so that the advantages and features of the present invention patent can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention patent.

[0018] Embodiment 1, the present invention provides a method for recovering chlorodifluoromethane from a preparation system, which includes the following steps: Step 1, collect the rectification residue in the preparation of chlorodifluoromethane in the residue storage tank 1, use heating to vaporize the residue in the residue storage tank 1, and transport the light-component chlorodifluoromethane to the recovery buffer tank 2 for storage. The liquid phase is sent to the alkali solution analysis tower 6 through the regulating valve 3 to analyze the chlorodifluoromethane in the liquid phase and also send it to the recovery buffer tank 2 for storage. The heat medium of the residue storage tank 1 in this embodiment is hot water heated by steam; Step 2, store the dilute acid in the preparation of chlorodifluoromethane in the dilute acid storage tank 5. The gas phase part of the dilute acid goes to the alkali solution analysis tower 6 to analyze chlorodifluoromethane and then goes to the recovery buffer tank 2 for storage. The dilute acid in Step 2 of this embodiment comes from the water washing tower I 14 in the chlorodifluoromethane preparation equipment. The water washing tower I 13 controls the pressure at 1.25 MPa, and the dilute acid is sent to the dilute acid storage tank 5 through the pressure reducing valve I 13. The pressure is in the atmospheric state, and the chlorodifluoromethane and hydrochloric acid dissolved in the dilute acid are analyzed out and enter the alkali solution analysis tower 6 to remove acidic substances and recover chlorodifluoromethane. Step 3, the crude chlorodifluoromethane in the alkali separator 16 in the preparation of chlorodifluoromethane is sent to the alkali solution analysis tower 6 to analyze chlorodifluoromethane and send it to the recovery buffer tank 2 for storage. At the same time, it serves as the alkali solution of the alkali solution analysis tower 6. The alkali solution contains chlorodifluoromethane. The alkali solution in Step 3 of this embodiment comes from the alkali separator 16, and the alkali separator 16 controls the pressure at 1.4 MPa; the alkali solution is sent to the alkali solution analysis tower 6 through the pressure reducing valve II 16 to analyze the gaseous chlorodifluoromethane. The pressure of the alkali solution analysis tower 6 is controlled at 1 - 5 kPa, and the temperature is at room temperature; Step 4, compress the chlorodifluoromethane stored in the recovery buffer tank 2 in Step 1, the chlorodifluoromethane stored in the recovery buffer tank 2 in Step 2, and the chlorodifluoromethane stored in the recovery buffer tank 2 in Step 3 by using the compressor 8, and transport it to the condensation collection tank 9 for collection. Use the recovery pump 4 to transport the chlorodifluoromethane in the condensation collection tank 9 to the water and alkali washing system to remove acidic substances. Finally, put the deacidified chlorodifluoromethane into the rectification tower 11 for refining to obtain the finished product of chlorodifluoromethane and store it in the finished product storage tank 12. The compressor 8 in Step 4 of this embodiment is a two-stage compressor. A pressure regulating valve 10 is set on the pipeline between the compressor 8 and the condensation collection tank 9. The two-stage compressor uses circulating water, 0 °C cold water, and -15 °C brine as the cooling water. The condensation collection tank 9 is of the type combined with the condenser 91 and the storage tank 92. The refrigerant of the condenser 91 uses -15 °C brine. The water washing tower 18 and the alkali washing tower 17 in the water and alkali washing system respectively absorb and remove HCL and HF gases in the crude chlorodifluoromethane. The pressure of the water washing tower 18 and the alkali washing tower 17 is controlled at 1.5 MPa, the pressure of the rectification tower 11 is controlled at 0.8 MPa, the top temperature is controlled at 1 °C, and the bottom temperature is controlled at 30 °C; the purity reaches 99.9%. The purity of the finished product of chlorodifluoromethane reaches 99.9%, the evaporation residue is less than or equal to 0.02%, the moisture content is equal to 10 ppm, and the acidity is equal to 0.1 ppm.

[0019] Embodiment 2. The present invention provides a method for recovering chlorodifluoromethane from a preparation system, which comprises the following steps: Step 1, the rectification residue in the preparation of chlorodifluoromethane is collected from the residue storage tank 1, and the residue in the residue storage tank 1 is vaporized by heating. The light-component chlorodifluoromethane is transported to the recovery buffer tank 2 for storage, and the liquid phase is sent to the alkali solution analysis tower 6 through the regulating valve 3 to analyze the chlorodifluoromethane in the liquid phase and also sent to the recovery buffer tank 2 for storage. The heat medium of the residue storage tank 1 in this embodiment is hot water heated by steam; Step 2, the dilute acid in the preparation of chlorodifluoromethane is stored in the dilute acid storage tank 5. The gas phase part of the dilute acid goes to the alkali solution analysis tower 6 to analyze the chlorodifluoromethane and then goes to the recovery buffer tank 2 for storage. The dilute acid in Step 2 of this embodiment comes from the water washing tower I 14 in the chlorodifluoromethane preparation equipment. The water washing tower I 13 controls the pressure at 1.35 MPa, and the dilute acid is sent to the dilute acid storage tank 5 through the pressure reducing valve I 13. The pressure is in the atmospheric state, and the chlorodifluoromethane and hydrochloric acid dissolved in the dilute acid are analyzed out and enter the alkali solution analysis tower 6 to remove acidic substances and recover chlorodifluoromethane. Step 3, the crude chlorodifluoromethane in the alkali separator 16 in the preparation of chlorodifluoromethane is sent to the alkali solution analysis tower 6 to analyze the chlorodifluoromethane and sent to the recovery buffer tank 2 for storage. At the same time, it serves as the alkali solution of the alkali solution analysis tower 6, and the alkali solution contains chlorodifluoromethane. The alkali solution in Step 3 of this embodiment comes from the alkali separator 16, and the alkali separator 16 controls the pressure at 1.55 MPa; the alkali solution is sent to the alkali solution analysis tower 6 through the pressure reducing valve II 16 to analyze the gaseous chlorodifluoromethane. The pressure of the alkali solution analysis tower 6 is controlled at 4 kPa, and the temperature is at room temperature; Step 4, the chlorodifluoromethane stored in the recovery buffer tank 2 in Step 1, the chlorodifluoromethane stored in the recovery buffer tank 2 in Step 2, and the chlorodifluoromethane stored in the recovery buffer tank 2 in Step 3 are compressed by the compressor 8 and then transported to the condensation collection tank 9 for collection. The chlorodifluoromethane in the condensation collection tank 9 is transported to the water and alkali washing system by the recovery pump 4 to remove acidic substances. Finally, the acid-removed chlorodifluoromethane is put into the rectification tower 11 for refining, and the finished product of chlorodifluoromethane is stored in the finished product storage tank 12. The compressor 8 in Step 4 of this embodiment is a two-stage compressor. A pressure regulating valve 10 is arranged on the pipeline between the compressor 8 and the condensation collection tank 9. The two-stage compressor uses circulating water, 0 °C cold water, and -35 °C brine as the cooling water. The condensation collection tank 9 is of the type combined with the condenser 91 and the storage tank 92. The refrigerant of the condenser 91 is -35 °C brine. The water washing tower 18 and the alkali washing tower 17 in the water and alkali washing system respectively absorb and remove the HCL and HF gases in the crude chlorodifluoromethane. The pressures of the water washing tower 18 and the alkali washing tower 17 are controlled at 1.7 MPa, the pressure of the rectification tower 11 is controlled at 1.3 MPa, the top temperature is controlled at 10 °C, and the bottom temperature is controlled at 60 °C; the purity reaches 99.9%. The purity of the finished product of chlorodifluoromethane reaches 99.9%, the evaporation residue is less than or equal to 0.02%, the water content is less than or equal to 10 ppm, and the acidity is less than or equal to 0.1 ppm.

[0020] The present invention also discloses a device for recovering chlorodifluoromethane from a preparation system, which includes a residual liquid storage tank 1, an alkali separator 16, a dilute acid storage tank 5, an alkali solution stripping tower 6, a recovery buffer tank 2, a compressor 8, a condensation collection tank 9, a water and alkali washing system, a distillation column 1, and a finished product storage tank 12. The residual liquid outlet of the chlorodifluoromethane preparation device is communicated with the inlet of the residual liquid storage tank 1. The gas phase outlet of the residual liquid storage tank 1 is communicated with the inlet Ⅰ at the top of the recovery buffer tank 2. The liquid phase outlet of the residual liquid storage tank 1 is communicated with the inlet of the alkali solution stripping tower 6 through a regulating valve 3. The dilute acid outlet of the water washing tower Ⅰ 14 in the chlorodifluoromethane preparation device is communicated with the inlet of the dilute acid storage tank 5 through a pressure reducing valve Ⅰ 13. The material outlet of the dilute acid storage tank 5 is communicated with the inlet of the alkali solution stripping tower 6. The alkali solution outlet of the alkali separator 16 in the chlorodifluoromethane preparation device is communicated with the inlet of the alkali solution stripping tower 6 through a pressure reducing valve Ⅱ 7. The outlet of the alkali solution stripping tower 6 is communicated with the inlet Ⅱ on the side of the recovery buffer tank 2. The chlorodifluoromethane outlet of the recovery buffer tank 2 is connected to the input end of the compressor 8. The output end of the compressor 8 is communicated with the inlet of the condensation collection tank 9. The outlet of the condensation collection tank 9 is communicated with the inlet of the water and alkali washing system through a recovery pump 4. The outlet of the water and alkali washing system is communicated with the finished product storage tank 12 through the distillation column 11. In this embodiment, the alkali solution stripping tower 6 is a packed tower. The tower body diameter of the alkali solution stripping tower 6 is DN600, DN700 or DN800; the height is 9000 - 12000 mm, and the tower bottom diameter of the alkali solution stripping tower 6 is 1200 - 1600 mm, and the height is 1600 - 2000 mm. In this embodiment, the compressor 8 is set as a two-stage compressor, and a pressure regulating valve 10 is installed on the pipeline between the compressor 8 and the condensation collection tank 9. In this embodiment, the condensation collection tank 9 includes a collection tank main body 91, and a condenser 92 is installed inside the collection tank main body 91. When the compressed chlorodifluoromethane enters the collection tank main body 91, the chlorodifluoromethane is condensed by the condenser 92. In this embodiment, the water and alkali washing system includes a water washing tower 18 and an alkali washing tower 17, and the water washing tower 18 and the alkali washing tower 17 are connected in series. Among them, the water washing tower 18 and the alkali washing tower 17 adopt a packed tower structure, and the packed material is PP Pall ring, PP Intalox saddle ring or PP flower ring; the diameter of the packed material is φ25, φ38 or φ50. In this embodiment, the packed material is PP Pall ring, and the diameter of the packed material is φ25.

[0021] Product process control and finished product inspection are obtained by gas chromatography analysis. The analysis results of the finished product chlorodifluoromethane are shown in the following table: Table - Product quality analysis results: Without being limited thereto, any change or replacement that can be thought of without creative work should be covered within the protection scope of this invention patent. Therefore, the protection scope of this invention patent should be subject to the protection scope defined by the claims.

Claims

1. A method for recovering chlorodifluoromethane from a preparation system, characterized in that it It includes the following steps: Step 1: Collect the rectification residue in the preparation of chlorodifluoromethane from the residue storage tank (1). Use heating to vaporize the residue in the residue storage tank (1), and transport the light-component chlorodifluoromethane to the recovery buffer tank (2) for storage. The liquid phase is sent to the caustic solution stripping tower (6) through the regulating valve (3) to strip the chlorodifluoromethane in the liquid phase and also send it to the recovery buffer tank (2) for storage; Step 2: Store the dilute acid in the preparation of chlorodifluoromethane in the dilute acid storage tank (5). The gas phase part of the dilute acid goes to the caustic solution stripping tower (6) to strip chlorodifluoromethane and then goes to the recovery buffer tank (2) for storage, Step 3: The crude chlorodifluoromethane in the caustic separator (16) in the preparation of chlorodifluoromethane is sent to the caustic solution stripping tower (6) to strip chlorodifluoromethane and send it to the recovery buffer tank (2) for storage. At the same time, it serves as the caustic solution of the caustic solution stripping tower (6), and the caustic solution contains chlorodifluoromethane; Step 4: Compress the chlorodifluoromethane stored in the recovery buffer tank (2) in Step 1, the chlorodifluoromethane stored in the recovery buffer tank (2) in Step 2, and the chlorodifluoromethane stored in the recovery buffer tank (2) in Step 3 using the compressor (8), and transport it to the condensation collection tank (9) for collection. Use the recovery pump (4) to transport the chlorodifluoromethane in the condensation collection tank (9) to the water and caustic washing system to remove acidic substances. Finally, put the acid-removed chlorodifluoromethane into the rectification tower (11) for refining to obtain the finished chlorodifluoromethane and store it in the finished product storage tank (12).

2. The method for recovering chlorodifluoromethane from a preparation system according to claim 1, characterized in that The heat medium of the residue storage tank (1) in Step 1 is hot water heated by steam.

3. The method for recovering chlorodifluoromethane from a preparation system according to claim 1, characterized in that The dilute acid in Step 2 comes from the water washing tower I (14) in the chlorodifluoromethane preparation equipment. The water washing tower I (13) controls the pressure at 1.25 - 1.35 MPa, and the dilute acid is sent to the dilute acid storage tank (5) through the pressure reducing valve I (13). The pressure is in the atmospheric state, and the chlorodifluoromethane and hydrochloric acid dissolved in the dilute acid are stripped out, enter the caustic solution stripping tower (6) to remove acidic substances, and recover chlorodifluoromethane.

4. The method for recovering chlorodifluoromethane from a preparation system according to claim 1, characterized in that The caustic solution in Step 3 comes from the caustic separator (16). The caustic separator (16) controls the pressure at 1.4 - 1.55 MPa; the caustic solution is sent to the caustic solution stripping tower (6) through the pressure reducing valve II (16) to strip the gaseous chlorodifluoromethane. The pressure of the caustic solution stripping tower (6) is controlled at 1 - 5 kPa, and the temperature is at room temperature.

5. The method for recovering chlorodifluoromethane from a preparation system according to claim 1, characterized in that In Step 4, the compressor (8) is a two-stage compressor. A pressure regulating valve (10) is provided on the pipeline between the compressor (8) and the condensation collection tank (9). The two-stage compressor uses cooling water as circulating water, 0°C cold water, -15°C brine or -35°C brine. The condensation collection tank (9) is in the form of a combination of a condenser (91) and a storage tank (92). The refrigerant of the condenser (91) uses -15°C brine or -35°C brine. The water scrubbing tower (11) and the caustic scrubbing tower (12) of the water and caustic scrubbing system respectively absorb and remove HCL and HF gases in the crude dichlorofluoromethane. The pressures of the water scrubbing tower (11) and the caustic scrubbing tower (12) are controlled at 1.5 - 1.7 MPa, the pressure of the distillation column (11) is controlled at 0.8 - 1.3 MPa, the top temperature is controlled at -10 - 10°C, and the bottom temperature is controlled at 30 - 60°C; the purity reaches 99.9%, and the purity of the dichlorofluoromethane finished product reaches 99.9%, the evaporation residue is less than or equal to 0.02%, the moisture is less than or equal to 10 ppm, and the acidity is less than or equal to 0.1 ppm.

6. An apparatus for recovering chlorodifluoromethane from a preparation system, characterized in that It includes a residual liquid storage tank (1), an alkali separator (16), a dilute acid storage tank (5), an alkali solution stripping tower (6), a recovery buffer tank (2), a compressor (8), a condensation collection tank (9), a water and caustic scrubbing system, a distillation column (11) and a finished product storage tank (12). The residual liquid outlet of the dichlorofluoromethane preparation device is communicated with the inlet of the residual liquid storage tank (1). The gas phase outlet of the residual liquid storage tank (1) is communicated with the inlet Ⅰ at the top of the recovery buffer tank (2). The liquid phase outlet of the residual liquid storage tank (1) is communicated with the inlet of the alkali solution stripping tower (6) through a regulating valve (3). The dilute acid outlet of the water scrubbing tower Ⅰ (14) of the dichlorofluoromethane preparation device is communicated with the inlet of the dilute acid storage tank (5) through a pressure reducing valve Ⅰ (13). The material outlet of the dilute acid storage tank (5) is communicated with the inlet of the alkali solution stripping tower (6). The alkali solution outlet of the alkali separator (16) of the dichlorofluoromethane preparation device is communicated with the inlet of the alkali solution stripping tower (6) through a pressure reducing valve Ⅱ (7). The outlet of the alkali solution stripping tower (6) is communicated with the inlet Ⅱ on the side of the recovery buffer tank (2). The dichlorofluoromethane outlet of the recovery buffer tank (2) is connected to the input end of the compressor (8). The output end of the compressor (8) is communicated with the inlet of the condensation collection tank (9). The outlet of the condensation collection tank (9) is communicated with the inlet of the water and caustic scrubbing system through a recovery pump (4). The outlet of the water and caustic scrubbing system is communicated with the finished product storage tank (12) through the distillation column (11).

7. The apparatus for recovering chlorodifluoromethane from a preparation system according to claim 5, characterized in that The said alkali solution stripping tower (6) is a packed tower. The tower body diameter of the alkali solution stripping tower (6) is DN600, DN700 or DN800; the height is 9000 - 12000 mm, the tower bottom diameter of the alkali solution stripping tower (6) is 1200 - 1600 mm, and the height is 1600 - 2000 mm.

8. The device for recovering chlorodifluoromethane from a preparation system according to claim 5, characterized in that The said compressor (8) is set as a two-stage compressor, and a pressure regulating valve (10) is installed on the pipeline between the compressor (8) and the condensation collection tank (9).

9. The device for recovering chlorodifluoromethane from a preparation system according to claim 5, characterized in that The condensation collection tank (9) includes a collection tank main body (91), and a condenser (92) is installed inside the collection tank main body (91). When the compressed chlorodifluoromethane enters the collection tank main body (91), the chlorodifluoromethane is condensed by the condenser (92).

10. The device for recovering chlorodifluoromethane from a preparation system according to claim 5, characterized in that The described water and alkali washing system includes a water washing tower (18) and an alkali washing tower (17). The water washing tower (18) and the alkali washing tower (17) are connected in series. Among them, the water washing tower (18) and the alkali washing tower (17) adopt a packed tower structure, and the packed materials are PP Pall rings, PP Intalox saddles or PP flower rings; the diameter of the packing is φ25, φ38 or φ50.

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