Chlorine recovery method in trifluorotrichloroethane production

Abstract

The invention discloses a method for recovering chlorine in trifluorotrichloroethane production, which comprises the following steps of: a, heating, gasifying and separating crude products, namely organic phases such as liquid chlorine, hydrogen fluoride, hydrogen chloride and trifluorotrichloroethane from an acidic material receiving tank, separating out acidic gases such as chlorine, and carrying out alkali washing on the separated trifluorotrichloroethane; b, cooling the separated acid gases such as chlorine and the like, and separating out uncondensed chlorine; c, fully mixing the separated chlorine gas with tetrachloroethylene; and d, feeding the chlorine-absorbed tetrachloroethylene into a fluorination reaction kettle to participate in the reaction. The method can effectively reduce the unit consumption of liquid chlorine and the consumption of liquid caustic soda.

Description

Technical Field

[0001] The present invention relates to a method for recovering chlorine gas in the production of 1,1,2-trichloro-1,2,2-trifluoroethane. Background Art

[0002] Currently, in the production of 1,1,2-trichloro-1,2,2-trifluoroethane, generally, three materials, namely tetrachloroethylene, hydrogen fluoride, and liquid chlorine, are used for fluorination and chlorination reactions in a reaction kettle. The materials at the outlet of the condenser of the reaction reflux tower will contain gases such as 1,1,2-trichloro-1,2,2-trifluoroethane, hydrogen chloride, and hydrogen fluoride. In order to condense and recover most of the 1,1,2-trichloro-1,2,2-trifluoroethane and hydrogen fluoride in the gas, generally, the gas at the outlet of the condenser of the reaction reflux tower is condensed by using four-stage condensers, namely pre-cooling, medium-cooling, tail-cooling, and deep-cooling condensers. Most of the hydrogen fluoride, 1,1,2-trichloro-1,2,2-trifluoroethane, and a small amount of hydrogen chloride in the gas will be condensed to form acidic materials. During the stratification process of the acidic materials in the stratification tank, the crude 1,1,2-trichloro-1,2,2-trifluoroethane is deposited at the lower part of the stratification tank, and it will entrain part of the hydrogen chloride and trace amounts of hydrogen fluoride and chlorine gas into the acidic material receiving tank. Due to the high pressure in the reaction kettle, it is relatively difficult to recover liquid chlorine. Generally, the water washing and alkali washing methods are used to treat the excess chlorine gas.

[0003] Using the water washing and alkali washing methods to treat the excess chlorine gas will result in a high unit consumption of liquid chlorine and consume a large amount of liquid caustic soda. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for recovering chlorine gas in the production of 1,1,2-trichloro-1,2,2-trifluoroethane that can effectively reduce the unit consumption of liquid chlorine and the consumption of liquid caustic soda.

[0005] In order to solve the above technical problem, the method for recovering chlorine gas in the production of 1,1,2-trichloro-1,2,2-trifluoroethane of the present invention includes the following steps: a. Heating and gasifying and separating the organic phase of the crude product, namely liquid chlorine, hydrogen fluoride, hydrogen chloride, and 1,1,2-trichloro-1,2,2-trifluoroethane, etc. from the acidic material receiving tank, separating out acidic gases such as chlorine gas, and sending the separated 1,1,2-trichloro-1,2,2-trifluoroethane for water and alkali washing; b. Cooling the separated acidic gases such as chlorine gas, and separating out the uncondensed chlorine gas; c. Fully mixing the separated chlorine gas with tetrachloroethylene; d. Sending the tetrachloroethylene absorbing chlorine gas into the fluorination reaction kettle to participate in the reaction.

[0006] In the step b, the temperature of the refrigerant used for cooling is -15°C.

[0007] In the step d, the tetrachloroethylene absorbing chlorine gas is heated and then sent into the fluorination reaction kettle to participate in the reaction.

[0008] In step a, the crude products from the acidic feed tank, i.e., organic phases such as liquid chlorine, hydrogen fluoride, hydrogen chloride, and 1,1,2-trichloro-1,2,2-trifluoroethane, enter the deacidification tower from the middle. The material entering the bottom of the deacidification tower is heated and vaporized by the deacidification tower reboiler. The rising gas flow contacts the cold feed countercurrently. Most of the organic phases such as 1,1,2-trichloro-1,2,2-trifluoroethane are cooled down by the reflux cold material and enter the water and alkali washing process.

[0009] In step b, the acidic gases such as uncooled chlorine gas are separated and enter the deacidification tower condenser, where they are cooled by a -15°C refrigerant. The condensed liquid flows back to the deacidification tower, and the uncondensed chlorine gas is taken out and sent to the chlorine absorption tower.

[0010] In step c, tetrachloroethylene is transported to the bottom of the chlorine absorption tower, and the chlorine gas is absorbed by the tetrachloroethylene.

[0011] In step d, the tetrachloroethylene that has absorbed chlorine gas falls into the bottom of the tower and is transported into the fluorination reactor through a PCE pump.

[0012] In step d, the tetrachloroethylene that has absorbed chlorine gas falls into the bottom of the tower, is heated by the tetrachloroethylene preheater, and then sent into the fluorination reactor.

[0013] In step c, tetrachloroethylene is transported to the bottom of the chlorine absorption tower. There are random packing Pall rings in the chlorine absorption tower, enabling the chlorine gas to come into full contact with the tetrachloroethylene, and the chlorine gas is absorbed by the tetrachloroethylene.

[0014] The method includes the following equipment and steps: The crude products from the acidic feed tank, i.e., organic phases such as liquid chlorine, hydrogen fluoride, hydrogen chloride, and 1,1,2-trichloro-1,2,2-trifluoroethane, enter the deacidification tower from the middle. The material entering the bottom of the deacidification tower is heated and vaporized by the deacidification tower reboiler. The rising gas flow contacts the cold feed countercurrently. Most of the organic phases such as 1,1,2-trichloro-1,2,2-trifluoroethane are cooled down by the reflux cold material and enter the water and alkali washing process; the acidic gases such as uncooled chlorine gas are separated and enter the deacidification tower condenser, where they are cooled by a -15°C refrigerant. The condensed liquid flows back to the deacidification tower, and the uncondensed chlorine gas is taken out and sent to the chlorine absorption tower; the tetrachloroethylene storage tank is connected to the tetrachloroethylene transfer pump through a pipeline, and the tetrachloroethylene transfer pump is connected to the chlorine absorption tower through a pipeline. The tetrachloroethylene in the tetrachloroethylene storage tank is transported to the bottom of the chlorine absorption tower through the tetrachloroethylene transfer pump; a part of the bottom material is pumped back through a PCE pump, and a part is transported to the fluorination reactor; the chlorine gas from the deacidification tower condenser enters the chlorine absorption tower and rises, where it is absorbed by the tetrachloroethylene. There are random packing Pall rings in the chlorine absorption tower, enabling the chlorine gas to come into full contact with the tetrachloroethylene; the tetrachloroethylene that has absorbed chlorine gas falls into the bottom of the tower, is transported through a PCE pump, and after being heated by the tetrachloroethylene preheater, enters the fluorination reactor to participate in the reaction.

[0015] Using the method of the present invention, first, a deacidification tower is used to separate chlorine gas from the organic phase. Then, the raw material tetrachloroethylene is used to absorb the excess chlorine gas, which is then re-introduced into the reaction for utilization. This solves the problem in the prior art that the excess chlorine gas cannot be recycled, effectively reducing the unit consumption of liquid chlorine and the consumption of liquid caustic soda in the production of trifluorotrichloroethane.

[0016] The method of the present invention adds a deacidification tower. First, the material is separated from chlorine gas, and then tetrachloroethylene is used to absorb chlorine gas, improving the efficiency of tetrachloroethylene in absorbing chlorine gas and effectively reducing the unit consumption of chlorine gas and the consumption of liquid caustic soda. If the organic phase reaction material is directly fed into the chlorine absorption tower without separation, it will result in low chlorine absorption efficiency.

[0017] The method of the present invention uses a deacidification tower to separate chlorine gas from the organic phase. First, it is heated and vaporized by a reboiler, and then cooled with a refrigerant at -15°C, enabling efficient separation of chlorine gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a block diagram of the process equipment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following describes the present invention in detail in conjunction with the drawings and specific embodiments: The method for recovering chlorine gas in the production of trifluorotrichloroethane of the present invention includes the following steps: a. The crude product from the acidic receiving tank, namely liquid chlorine, hydrogen fluoride, hydrogen chloride, trifluorotrichloroethane and other organic phases, is heated and vaporized for separation to separate acidic gases such as chlorine gas, and the separated trifluorotrichloroethane is sent for water and caustic soda washing; b. The separated acidic gases such as chlorine gas are cooled to separate the uncondensed chlorine gas; c. The separated chlorine gas is fully mixed with tetrachloroethylene; d. The tetrachloroethylene absorbing chlorine gas is sent to the fluorination reaction kettle to participate in the reaction.

[0020] As Figure 1As shown in the figure, the method for recovering chlorine gas in the production of trichlorotrifluoroethane according to the present invention includes the following equipment and steps: The crude product from the acidic receiving tank, namely liquid chlorine, hydrogen fluoride, hydrogen chloride, trichlorotrifluoroethane and other organic phases, enters the deacidification tower from the middle. The material entering the bottom of the deacidification tower is heated and vaporized by the reboiler of the deacidification tower. The gas flow rises and contacts the cold material in a countercurrent manner. Most of the organic phases such as trichlorotrifluoroethane are cooled down by the reflux cold material and enter the water and alkali washing; The acidic gases such as uncooled chlorine gas are separated and enter the deacidification tower condenser, where they are cooled by a refrigerant at -15°C. The condensed liquid flows back to the deacidification tower, and the uncondensed chlorine gas is taken out and sent to the chlorine absorption tower; Connect the perchloroethylene storage tank and the perchloroethylene transfer pump through pipelines. The perchloroethylene transfer pump is connected to the chlorine absorption tower through pipelines. The perchloroethylene in the perchloroethylene storage tank is transported to the bottom of the chlorine absorption tower by the perchloroethylene transfer pump; Part of the material at the bottom of the tower is pumped back by the material pump, and part is transported to the fluorination reactor; The chlorine gas from the deacidification tower condenser enters the chlorine absorption tower and rises upward, where it is absorbed by perchloroethylene. There are random packing Pall rings in the chlorine absorption tower, enabling the full contact of chlorine gas and perchloroethylene; The perchloroethylene that has absorbed chlorine gas falls into the bottom of the tower, is transported by the material pump, and then enters the fluorination reactor to participate in the reaction after being heated by the perchloroethylene preheater.

Claims

1. A method for recovering chlorine in the production of trifluorotrichloroethane, characterized in that The steps include: a. The crude product from the acidic receiving tank, i.e., liquid chlorine, hydrogen fluoride, hydrogen chloride and trifluorotrichloroethane, etc., is heated and gasified to separate the organic phase, and the acidic gases such as chlorine are separated, and the separated trifluorotrichloroethane is washed with water; b. Cooling the separated chlorine and other acidic gases to separate the uncondensed chlorine; c. Fully mix the separated chlorine gas with tetrachloroethylene; d. Send the tetrachloroethylene that has absorbed chlorine into the fluorination reactor to participate in the reaction.

2. The method according to claim 1, characterized in that: In the step b, the temperature of the refrigerant used for cooling is -15°C.

3. The method according to claim 1, characterized in that: In the step d, the tetrachloroethylene that has absorbed chlorine is heated and then fed into a fluorination reactor to participate in the reaction.

4. The method according to claim 1, characterized in that: In the step a, the crude product from the acidic material receiving tank, i.e., liquid chlorine, hydrogen fluoride, hydrogen chloride, trifluorotrichloroethane and other organic phases, enters the deacidification tower from the middle, and the materials entering the deacidification tower kettle are heated and vaporized by the deacidification tower reboiler, and the air flow rises and contacts with the cold material in countercurrent, and most of the organic phases such as trifluorotrichloroethane are cooled down by the reflux cold material and enter the water alkali washing.

5. The method according to claim 1, characterized in that: In the step b, the uncooled chlorine and other acidic gases are separated and enter the deacidification tower condenser, cooled by -15°C refrigerant, the condensed liquid is refluxed to the deacidification tower, and the uncondensed chlorine is extracted and sent to the chlorine absorption tower.

6. The method according to claim 1, characterized in that: In the step c, tetrachloroethylene is transported to the kettle of the chlorine absorption tower, and the chlorine is absorbed by the tetrachloroethylene.

7. The method according to claim 1, characterized in that: In the step d, the tetrachloroethylene that absorbs the chlorine falls into the tower kettle and is transported into the fluorination reaction kettle through a material pump.

8. The method according to claim 3, characterized in that: In the step d, the tetrachloroethylene that absorbs chlorine falls into the tower kettle, is heated by the tetrachloroethylene preheater, and then is sent to the fluorination reaction kettle.

9. The method according to claim 6, characterized in that: In the step c, the tetrachloroethylene is transported to the kettle of the chlorine absorption tower, and the chlorine absorption tower has a random ball ring filler, so that the chlorine and the tetrachloroethylene are fully contacted, and the chlorine is absorbed by the tetrachloroethylene.

10. The method according to claim 1, characterized in that The method comprises the following equipment and steps: crude products from an acid receiving tank, i.e., liquid chlorine, hydrogen fluoride, hydrogen chloride, trifluorotrichloroethane and other organic phases, enter a deacidification tower from the middle; the materials entering the deacidification tower kettle are heated and vaporized by a deacidification tower reboiler; the airflow rises and countercurrently contacts with cold materials; most of the organic phases such as trifluorotrichloroethane are cooled by reflux cold materials and enter water alkali washing; the uncooled chlorine and other acidic gases are separated and enter a deacidification tower condenser, cooled by a -15°C refrigerant, the condensed liquid is refluxed to the deacidification tower, and the uncondensed chlorine is extracted and sent to a chlorine absorption tower; the tetrachloroethylene storage tank and the tetrachloroethylene transmission tank are connected; The delivery pump is connected through a pipeline, the tetrachloroethylene delivery pump is connected to the chlorine absorption tower through a pipeline, and the tetrachloroethylene in the tetrachloroethylene storage tank is delivered to the kettle of the chlorine absorption tower through the tetrachloroethylene delivery pump; a part of the material in the kettle is refluxed through a material pump, and a part is delivered to the fluorination reactor; the chlorine from the condenser of the deacidification tower enters the chlorine absorption tower and rises up, and is absorbed by the tetrachloroethylene. There is a random ball ring filler in the chlorine absorption tower, so that the chlorine and the tetrachloroethylene are fully contacted; the tetrachloroethylene that absorbs the chlorine falls into the kettle, is delivered through a material pump, and then enters the fluorination reactor to participate in the reaction after being heated by a tetrachloroethylene preheater.

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