Epoxy alkane chlorohydrin method clean production device based on chlorine closed-loop cyclic utilization

Abstract

An alkylene oxide chlorohydrination method clean production device based on chlorine closed-loop cyclic utilization is characterized in that a chlorine dissolving device and a propylene distributor are connected into a chlorohydrination reactor and then connected with a flash tower, and a tail gas outlet in the top of the flash tower is connected into an alkali washing tower and then connected into a propylene recovery system to form a chlorohydrination subsystem; the pipeline type causticization reactor and the stripping tower form a causticization subsystem; a front distillation tower and a rectifying tower are connected in series to form an epoxypropane rectifying subsystem, an electromagnetic heating pipeline type gasification reactor and a supercritical delayed gasification reactor form a causticization wastewater treatment subsystem, chlorine in an electrolytic bath of a NaCl solution electrolysis subsystem enters a chlorine dissolving device of a chlorohydrination subsystem, and NaOH electrolyte enters a pipeline type causticization reactor of the causticization subsystem; the chlorohydrination subsystem is connected to a pipeline type causticization reactor of the causticization subsystem, crude alkylene oxide at the top of a stripping tower of the causticization subsystem enters a front distillation tower of the alkylene oxide rectification subsystem, and causticization wastewater at the bottom of the stripping tower enters an electromagnetic heating pipeline type gasification reactor of the causticization wastewater treatment subsystem.

Description

1. Technical Field

[0001] The invention provides an alkylene oxide chlorohydrin process clean production device based on closed-loop recycling of chlorine, and relates to the field of fine chemicals. 2. Background technology

[0002] The chlorohydrin process for preparing alkylene oxide is to prepare hypochlorous acid by chlorine and water, and C2-C7 olefins react with hypochlorous acid to obtain chlorohydrin, which is then reacted with slaked lime or caustic soda to generate alkylene oxide, and then separated by ordinary distillation method to obtain refined alkylene oxide. The chlorohydrin process for preparing propylene oxide was industrialized as early as 1931. It has mature production technology, short process, large operating load flexibility, good selectivity, low requirements for raw material purity, safe and stable production, low construction investment, and products with strong cost competitiveness. At present, about 40% of the world's propylene oxide production capacity is produced by the chlorohydrin process. However, the traditional chlorohydrin process device is less environmentally friendly, with large consumption of water resources and chlorine, and the caustic wastewater containing chlorides is difficult to handle, polluting the environment. At the same time, the chloric acid produced also corrodes the equipment more seriously. For example, for every ton of propylene oxide produced, about 1.5 tons of chlorine are consumed, and at least 40 tons of caustic wastewater containing a small amount of organic chloride and more than 2 tons of CaCl2 waste residue are produced.

[0003] In order to solve the three wastes and corrosion defects of propylene oxide produced by the chlorohydrin method, co-oxidation and direct oxidation methods have been developed at home and abroad. The co-oxidation method overcomes the shortcomings of the chlorohydrin method, such as high corrosiveness and large amount of sewage, but its disadvantages are long process flow, many raw material varieties, high propylene purity requirements, and expensive equipment costs. Propylene oxide produces a large number of co-products in the co-oxidation method. Each ton of propylene oxide must produce 2.5 tons of styrene or 2.4 tons of tert-butyl alcohol. The advantages of this process can only be shown when the market demand for propylene oxide and co-products matches; in addition, the COD of sewage produced by this method is high, and the treatment cost accounts for about 10% of the total investment. The advantages of the direct oxidation method are high conversion rate and selectivity, the amount of wastewater is only 30% of other existing technologies, and the energy consumption is 65% of the existing process; the process flow is simple and economical, the by-product is water, the environmental pollution is small, the land use is small, the factory infrastructure investment is small, and the investment can be reduced by 25%, but the technology is immature, the cost is high, and the safety is poor.

[0004] To this end, Dow Chemical Company of the United States uses 10% to 20% NaOH electrolyte to replace the lime milk (mainly composed of Ca(OH)2) used in the causticizing reaction, which greatly reduces the mass concentration of propylene glycol (PDO) and dichloropropane (DCP) in the saponification waste liquid, and obtains a relatively pure salt solution (mainly composed of NaCl and H2O). The causticizing salt solution is refined to obtain saturated brine and sent to the electrolytic cell, where chlorine, hydrogen and sodium hydroxide are obtained through electrolysis. Chlorine is used as the reaction raw material of the chlorohydrin method, and sodium hydroxide is continued to be used to participate in the saponification reaction, which is recycled to improve the economic efficiency of the reaction. Although this improvement can effectively reduce the amount of sewage and waste residue (mainly composed of CaCl2) generated after saponification, and reduce the pollution to soil and water sources, the current refining of the causticizing salt solution is too difficult and the cost is too high, which makes it difficult to meet the requirements of the chlor-alkali electrolytic cell.

[0005] If the existing chlorohydrin process for producing alkylene oxides adopts NaOH causticization reaction, it can solve the problem of pollution treatment of chloride-containing caustic wastewater and low-cost recycling of concentrated brine at low cost, and realize closed-loop recycling of chlorine, and the cost and water consumption of propylene oxide can be greatly reduced, then compared with the co-oxidation method and direct oxidation method, the chlorohydrin process for producing alkylene oxides has more development advantages. However, the existing caustic wastewater treatment processes have failed to achieve full resource utilization of caustic wastewater, and it is urgent to develop efficient, clean and low-energy consumption processes and equipment technologies for alkylene oxide chlorohydrin process, eliminate the industrial bottlenecks of high pollution and high water consumption of alkylene oxide chlorohydrin process, and improve its market competitiveness. 3. Summary of the invention

[0006] The invention aims to overcome the shortcomings of the existing chlorohydrin process alkylene oxide technology and to invent a clean production device for chlorohydrin process of alkylene oxide based on chlorine closed-loop recycling. Chlorohydrin is rapidly causticized in a pipeline reactor by means of NaOH electrolyte, causticized waste liquid is supercritically gasified in an electromagnetic heating pipeline reactor and a supercritical delayed gasification reactor, and a gas-liquid mixed phase is separated from the NaCl phase, salt is discharged by a high-pressure lock bucket, and waste heat of high-temperature purified water is recovered and then recycled, and a NaCl solution diluted by part of the purified water in the high-pressure lock bucket is used to produce chlorine and recycle the NaOH electrolyte, so that the industrial bottleneck of high water consumption, high pollution and difficulty in full resource utilization of causticized waste liquid in the production of propylene oxide chlorohydrin process is solved at a low cost, and the serious corrosion of chlorine-containing acid generated by the treatment of causticized waste liquid to equipment is eliminated, thereby realizing the clean production of propylene oxide by chlorohydrin process with low water consumption, low energy consumption and chlorine closed-loop recycling.

[0007] The technical solution of the present invention:

[0008] A clean production device for chlorohydrin process of alkylene oxide based on closed-loop recycling of chlorine, wherein the circulating purified water inlet is connected to the chlorohydrin reactor through a chlorine dissolving device and a propylene distributor in sequence, the chlorohydrin reactor is then connected to a flash tower, the tail gas outlet at the top of the flash tower is connected to an alkali washing tower and then to a propylene recovery system, forming a chlorohydrin subsystem, the circulating purified water temperature is 35-45°C, the molar ratio of chlorine to propylene is 1:1.01-1.1, the reaction pressure is normal pressure or slightly higher than normal pressure, the reaction temperature is 50-70°C, and a solution containing 3.0wt%-6.0wt% of chloropropanol is generated, and the solution contains hydrochloric acid in an equal mole to the chloropropanol; the NaOH electrolyte inlet is connected to the chlorohydrin reactor through a pipeline The causticizing reactor is connected with the stripping tower to form a causticizing subsystem, the concentration of NaOH electrolyte is 10wt%-20wt%, the molar ratio of sodium hydroxide / chloropropanol+hydrochloric acid is 1.0-1.2:1, the causticizing reaction temperature is controlled at 90-95°C, the reaction time is controlled at 0.5-2 seconds, the concentration of crude propylene oxide at the top of the stripping tower is 90wt%-95wt%, the absolute pressure at the top of the stripping tower is 25-65Kpa, and the NaCl concentration in the causticizing wastewater at the bottom of the stripping tower is 2.5wt%-5.5wt%; the fore-distillation tower and the distillation tower are connected in series to form a propylene oxide distillation subsystem, the crude propylene oxide material first passes through the fore-distillation tower, and the finished propylene oxide is discharged from the fore-distillation tower The high-boiling-point components are discharged from the top of the distillation tower, the operating pressure of the fore-distillation tower and the distillation tower is atmospheric pressure, the bottom temperature is controlled at 50°C to 85°C, and the causticized wastewater is discharged from the bottom of the distillation tower; the high-pressure pump is connected to the supercritical delayed gasification reactor through an electromagnetic heating pipeline gasification reactor, and the salt discharge lock bucket at the bottom of the supercritical delayed gasification reactor is connected to the high-temperature purified water outlet of the gas-liquid separation tank respectively, forming a causticized wastewater treatment subsystem; the diluted brine inlet is connected to the electrolytic cell of the NaCl solution electrolysis subsystem, the chlorine outlet of the electrolytic cell is connected to the chlorine dissolving device of the chlorohydrin subsystem through a compressor, and the NaOH electrolyte is connected to the pipeline causticizing reactor of the causticizing subsystem through a pressure pump. the chlorohydrinization subsystem is connected to the inlet of the pipeline causticizing reactor of the causticizing subsystem through the chlorohydrin solution outlet at the bottom of the flash tower, the crude alkylene oxide outlet at the top of the stripping tower of the causticizing subsystem is connected to the inlet of the fore-distillation tower of the alkylene oxide rectification subsystem, the causticized wastewater outlet at the bottom of the stripping tower is connected to the inlet of the electromagnetic heating pipeline gasification reactor of the causticizing wastewater treatment subsystem, and the waste liquid outlet of the tail gas washing tower of the chlorohydrinization subsystem and the causticized wastewater outlet at the bottom of the distillation tower of the propylene oxide rectification subsystem are also connected to the inlet of the electromagnetic heating pipeline gasification reactor; the salt discharge lock hopper at the bottom of the supercritical delayed gasification reactor of the causticizing wastewater treatment subsystem is connected to the electrolytic cell of the NaCl solution electrolysis subsystem.

[0009] Among them, the chlorine dissolver is a microporous pipeline chlorine dissolver, a jet pump chlorine dissolver or a T-type straight tube chlorine dissolver.

[0010] The propylene distributor is a microporous pipeline mixer or a jet pump mixer, and the chlorohydrinization reactor is a pipeline reactor with an internal mixing element reinforcement, a single-tower chlorohydrin reactor, a single-tower multi-tower chlorohydrin reactor in series, a tube-tower chlorohydrin reactor or a tube reactor.

[0011] In order to improve the conversion rate of chloropropanol, the causticizing reaction is carried out in a pipeline causticizing reactor. The amount of NaOH added should be excessive, and the NaOH content in the causticizing wastewater should be controlled at 0.01% to 1.3wt%.

[0012] The caustic wastewater at the bottom of the stripping tower is pressurized to ≥22.1MPa by a high-pressure pump, and then heat exchanged with the supercritical gasified syngas and supercritical high-temperature purified water mixed phase; the preheated caustic waste liquid is heated to 400-700℃ by an electromagnetic heating tubular reactor for supercritical gasification reaction, and the supercritical gasified gas and liquid enter the supercritical delayed gasification reactor and stay for 1-180 minutes to generate a syngas and supercritical high-temperature purified water mixed phase and a high-concentration NaCl slurry; the extracted syngas and supercritical high-temperature purified water mixed phase are separated from the gas and liquid after heat exchange with the high-pressure dissolved oxygen caustic waste liquid, and the syngas is discharged and the purified water is reused; the high-concentration NaCl slurry is passed through the bottom lock of the supercritical delayed gasification reactor. The hopper is switched, and part of the purified water is used to dilute it into 31.5%-36.1% concentrated brine and then return it to the electrolytic cell for recycling; the electromagnetic heating tubular reactor is under the action of the electromagnetic heating controller, when high-frequency alternating current passes through the coil to generate an alternating magnetic field, the tubular reactor wall and the internal self-mixing strengthening internal components generate eddy current self-heating, thereby achieving uniform heating of high-pressure dissolved oxygen causticizing waste liquid, rapid temperature increase and gasification reaction; the self-mixing strengthening internal components are regular packing type, X-cross plate type or spiral plate type; a funnel-shaped liquid extraction port is arranged in the center of the supercritical delayed gasification reactor, the funnel is connected to the upper part of the reactor, a gas-liquid mixed phase discharge port is arranged on the top of the reactor, and two or more salt discharge lock hoppers are arranged at the bottom of the reactor.

[0013] The electrolyzer is an oxygen anion membrane electrolyzer or an anion membrane electrolyzer.

[0014] The present invention will be described in detail with reference to embodiments. 4. Description of the drawings

[0015] Attached Figure 1 It is a process schematic diagram of the present invention.

[0016] Attached Figure 1 The following is a description of the drawings:

[0017] 1. Chlorine dissolver 2. Propylene distributor 3. Chlorohydrin reactor 4. Flash tower 5. Alkali scrubber 6. Pipeline causticizing reactor 7. Stripping tower 8. Supercritical gasification device 9. Fore-distillation tower 10. Distillation tower 11. Chlor-alkali electrolyzer A. Propylene inlet B. Purified tail gas outlet C. Ethylene oxide product outlet D. Heavy component outlet E. Causticizing liquid outlet F. Synthesis gas outlet

[0018] Attached Figure 2 The following is a description of the drawings:

[0019] 12. High-pressure pump 13. Heat exchanger 14. Electromagnetic heating tubular reactor 15. Electromagnetic heating controller 16. Supercritical delayed gasification reactor 17. Gas-liquid separation tank G, NaOH caustic waste liquid inlet L, synthesis gas outlet M, purified water outlet N, diluted brine outlet

[0020] The process characteristics of the present invention are described in detail below in conjunction with the accompanying drawings and embodiments. 5. Specific implementation methods

[0021] Embodiment: A clean production device for chlorohydrin process of alkylene oxide based on closed-loop recycling of chlorine, wherein the circulating purified water inlet is connected to the chlorohydrin reactor (3) through the chlorine dissolving device (1) and the propylene distributor (2) in sequence, the propylene is connected to the propylene distributor (2) through the propylene inlet A, the chlorohydrin reactor (3) is then connected to the flash tower (4), the tail gas outlet of the flash tower (4) is connected to the alkali washing tower (5) and then connected to the propylene recovery system through the purified tail gas outlet B, forming a chlorohydrin subsystem, the circulating purified water temperature is 35-45°C, the molar ratio of chlorine to propylene is 1:1.01-1.1, the reaction pressure is normal pressure or slightly higher than normal pressure, the reaction temperature is 50-70°C, and the generated chloropropanol is 3.0w t%~6.0wt% solution, the solution contains hydrochloric acid in an amount equimolar to that of chloropropanol; the NaOH electrolyte inlet G is connected to the stripping tower (7) through a pipeline causticizing reactor (6) to form a causticizing subsystem, the concentration of the NaOH electrolyte is 10wt%~20wt%, the molar ratio of sodium hydroxide / chloropropanol+hydrochloric acid is 1.0~1.2:1, the causticizing reaction temperature is controlled at 90~95℃, the reaction time is controlled at 0.5-2 seconds, the concentration of crude propylene oxide at the top of the stripping tower (7) is 90wt%~95wt%, the absolute pressure at the top of the stripping tower (7) is 25~65Kpa, and the NaCl concentration in the causticized wastewater at the bottom of the stripping tower (7) is 2.5wt%~5.5wt%; a front distillation tower (9) and a distillation tower (10) are connected in series to form a propylene oxide distillation subsystem, the crude propylene oxide material first passes through the front distillation tower (9), the finished propylene oxide is discharged from the ethylene oxide product outlet C at the top of the front distillation tower (9), and the high boiling point component is discharged from the heavy component outlet D at the top of the distillation tower (10), the operating pressure of the front distillation tower (9) and the distillation tower (10) is atmospheric pressure, the tower bottom temperature is controlled at 50°C to 85°C, and the causticized liquid outlet E at the bottom of the distillation tower (10) discharges causticized waste water; high pressure The pump (12) is connected to the supercritical delayed gasification reactor (16) through the electromagnetic heating pipeline gasification reactor (13); the salt discharge lock bucket at the bottom of the supercritical delayed gasification reactor (16) is respectively connected to the high-temperature purified water outlet M of the gas-liquid separation tank (17); the top of the gas-liquid separation tank (17) is provided with a synthesis gas outlet F; the bottom of the salt discharge lock bucket is provided with a diluted brine outlet N, forming a treatment subsystem of the caustic wastewater supercritical gasification device (8); the diluted brine inlet is connected to the chlor-alkali electrolysis of the NaCl solution electrolysis subsystem The chlorine gas outlet of the chlor-alkali electrolytic cell (11) is connected to the chlorine dissolving device (1) of the chlorohydrinization subsystem through a compressor, and the NaOH electrolyte is connected to the pipeline causticizing reactor (6) of the causticizing subsystem through a high-pressure pump; the chlorohydrin solution outlet at the bottom of the flash tower (4) of the chlorohydrinization subsystem is connected to the inlet of the pipeline causticizing reactor (6) of the causticizing subsystem, the crude alkylene oxide outlet at the top of the stripping tower (7) of the causticizing subsystem is connected to the inlet of the fore-distillation tower (9) of the alkylene oxide distillation subsystem, and the stripping tower (7) is connected to the inlet of the fore-distillation tower (9) of the alkylene oxide distillation subsystem. (7) The bottom caustic wastewater outlet is connected to the inlet of the electromagnetic heating pipeline gasification reactor (14) of the caustic wastewater treatment subsystem, and at the same time, the waste liquid outlet of the tail gas alkali scrubber (5) of the chlorohydrin subsystem and the bottom caustic wastewater outlet of the distillation tower (10) of the propylene oxide distillation subsystem are also connected to the inlet of the electromagnetic heating pipeline gasification reactor (14); the salt discharge lock hopper at the bottom of the supercritical delayed gasification reactor (16) of the caustic wastewater treatment subsystem is connected to the chlor-alkali electrolysis cell (11) of the NaCl solution electrolysis subsystem.

[0022] Wherein, the chlorine dissolver (1) is a microporous pipeline chlorine dissolver, a jet pump chlorine dissolver or a T-shaped straight tube chlorine dissolver.

[0023] The propylene distributor (2) is a microporous pipeline mixer or a jet pump mixer, and the chlorohydrinization reactor is a pipeline reactor with an internal mixing element, a single-tower chlorohydrin reactor, a single-tower multi-tower chlorohydrin reactor in series, a tube-tower chlorohydrin reactor or a tube reactor.

[0024] The causticizing reaction is carried out in the pipeline causticizing reactor (6). In order to improve the conversion rate of chloropropanol, the amount of NaOH added should be excessive, and the NaOH content in the causticizing wastewater is controlled at 0.01% to 1.3wt%.

[0025] In the treatment subsystem of the caustic wastewater supercritical gasification device (8), the caustic wastewater at the bottom of the stripping tower (7) is pressurized to ≥22.1MPa through the NaOH caustic wastewater inlet G by a high-pressure pump (12), and then heat exchanged with the supercritically gasified synthesis gas and supercritical high-temperature purified water mixed phase through a heat exchanger (13); the preheated caustic wastewater is heated to 400-700°C by an electromagnetic heating tubular reactor (14) for supercritical gasification reaction, and the supercritically gasified gas and liquid enter the supercritical delayed gasification reactor (16) and stay for 1-180 minutes to generate a mixed phase of synthesis gas and supercritical high-temperature purified water and a high-concentration NaCl slurry; the extracted synthesis gas and supercritical high-temperature purified water mixed phase are heat exchanged with the high-pressure dissolved oxygen caustic wastewater through the heat exchanger (13) and then enter the gas-liquid separator (17) for gas-liquid separation, and the synthesis gas is discharged from the synthesis gas outlet L( Figure 1 F) discharge, purified water reuse; high-concentration NaCl slurry is switched through the bottom lock hopper of the supercritical delayed gasification reactor (16), and diluted with part of the purified water to 31.5%-36.1% concentrated brine and then returned to the chlor-alkali electrolysis cell (11) for recycling; the electromagnetic heating tubular reactor (14) is under the action of the electromagnetic heating controller (15), when high-frequency alternating current passes through the coil to generate an alternating magnetic field, the tubular reactor wall and the internal self-mixing strengthening internal components generate eddy current self-heating, thereby achieving uniform heating of high-pressure dissolved oxygen causticizing waste liquid, rapid temperature increase and gasification reaction; the self-mixing strengthening internal components are regular packing type, X-cross plate type or spiral plate type; a funnel-shaped liquid extraction port is arranged at the center of the supercritical delayed gasification reactor (17), the funnel is connected to the upper part of the reactor, a gas-liquid mixed phase discharge port is arranged at the top of the reactor, and two or more salt discharge lock hoppers are arranged at the bottom of the reactor.

[0026] The chlor-alkali electrolyzer (11) is an oxygen anion membrane electrolyzer or an anion membrane electrolyzer.

[0027] The specific reaction conditions and experimental results are as follows:

[0028] (1) Under 24MPa and 450℃, the supercritical gasification reaction is 2 seconds when heated, the supercritical delayed gasification reaction is 10 minutes, the COD removal rate is 99.1%, the quality of the concentrated brine can meet the requirements of electrolysis in the chlor-alkali electrolyzer, and the H2 in the synthesis gas is 70% and CO is 10%. An anion membrane electrolyzer is used to generate NaOH electrolyte, H2 and chlorine, the NaOH electrolyte and chlorine are recycled, and H2 is mixed with the synthesis gas for chemical synthesis.

[0029] (2) Under 24 MPa and 550°C, the supercritical gasification reaction lasts for 2 seconds and the supercritical delayed gasification reaction lasts for 5 minutes. The COD removal rate is 99.9%, and the quality of the concentrated brine fully meets the requirements of electrolysis in the chlor-alkali electrolyzer. The H2 content in the synthesis gas is 65% and the CO content is 8%. The oxygen anion membrane electrolyzer is used to generate only NaOH electrolyte and chlorine, and the energy consumption of electrolysis is reduced by 35%.

[0030] This method is not only used for the preparation of propylene oxide by the chlorohydrin process, but can also be used for the resource-based epoxidation of olefins such as ethylene, butene, and pentene.

[0031] The clean production device of chlorohydrin process of alkylene oxide based on closed-loop recycling of chlorine provided by the present invention is used for electrolysis to produce NaOH electrolyte and chlorine after NaOH causticizing and supercritical gasification treatment of causticizing wastewater to ensure circulation. At the same time, the pipeline reactor strengthens heat and mass transfer and inhibits salt precipitation scaling corrosion by self-mixing strengthening internal components. The supercritical delayed gasification reactor is used to improve the gasification efficiency and realize the separation of water-gas mixed phase and salt phase by supercritical water characteristics. Organic matter in the causticizing wastewater is completely gasified to produce synthesis gas containing more than 60% of H2, and the COD removal rate is greater than 99%. The brine concentration is flexibly regulated with low cost and low energy consumption according to the needs of the electrolyzer. The cost and investment of resource management of NaOH causticizing wastewater are reduced by more than 70% compared with traditional treatment methods, and the high water consumption and high pollution of the chlorohydrin process are eliminated. The yield of propylene oxide is increased by 3 percentage points and the selectivity is increased by 10%, thereby realizing the closed-loop utilization of chlorine.

Claims

1. A clean production device for chlorohydrin process of alkylene oxide based on closed-loop recycling of chlorine, characterized in that The circulating purified water inlet is connected to the chlorohydrinization reactor through the chlorine dissolving device and the propylene distributor in turn, and the chlorohydrinization reactor is connected to the flash tower. The tail gas outlet at the top of the flash tower is connected to the alkali washing tower and then to the propylene recovery system to form a chlorohydrinization subsystem. The circulating purified water temperature is 35-45°C, the molar ratio of chlorine to propylene is 1:1.01-1.1, the reaction pressure is normal pressure or higher than normal pressure but not higher than 10KPa (gauge pressure), the reaction temperature is 50-70°C, and a solution containing 3.0wt%-6.0wt% of chloropropanol is generated, and the solution contains hydrochloric acid with an equal molar concentration to that of chloropropanol; the NaOH electrolyte inlet is connected to the stripping tower through a pipeline causticizing reactor to form a causticizing subsystem, the concentration of NaOH electrolyte is 10wt%~20wt%, the molar ratio of sodium hydroxide to (chloropropanol and hydrochloric acid) is 1.0~1.2:1, the causticizing reaction temperature is controlled at 90~95°C, the reaction time is controlled at 0.5-2 seconds, the concentration of crude propylene oxide at the top of the stripping tower is 90wt%~95wt%, the absolute pressure at the top of the stripping tower is 25~65Kpa, and the NaCl concentration in the causticizing wastewater at the bottom of the stripping tower is 2.5wt%~5.5wt%; the fore-distillation tower and the distillation tower are connected in series to form a propylene oxide distillation subsystem, the crude propylene oxide material first passes through the fore-distillation tower, the finished propylene oxide is extracted from the top of the fore-distillation tower, and the high-boiling point components are discharged from the top of the distillation tower. The operating pressure of the fore-distillation tower and the rectifying tower is atmospheric pressure, and the bottom temperature is controlled at 50°C to 85°C. The causticized wastewater is discharged from the bottom of the rectifying tower; the high-pressure pump is connected to the supercritical delayed gasification reactor through an electromagnetic heating pipeline gasification reactor, and the salt discharge lock hopper at the bottom of the supercritical delayed gasification reactor is respectively connected to the high-temperature purified water outlet of the gas-liquid separation tank, and a diluted brine outlet is arranged under the salt discharge lock hopper, forming a causticized wastewater supercritical gasification device treatment subsystem; the diluted brine inlet is connected to the chlor-alkali electrolytic cell of the NaCl solution electrolysis subsystem, the chlorine outlet of the chlor-alkali electrolytic cell is connected to the chlorine dissolving device of the chlorohydrin subsystem through a compressor, and the NaOH electrolyte outlet is connected to the pipeline causticizing reactor of the causticizing subsystem through a pressure pump. The chlorohydrin subsystem is connected to the inlet of the pipeline causticizing reactor of the causticizing subsystem through the chlorohydrin solution outlet at the bottom of the flash tower, the crude alkylene oxide outlet at the top of the stripping tower of the causticizing subsystem is connected to the inlet of the fore-distillation tower of the alkylene oxide rectification subsystem, the causticizing wastewater outlet at the bottom of the stripping tower is connected to the inlet of the electromagnetic heating pipeline gasification reactor of the causticizing wastewater treatment subsystem, and the waste liquid outlet of the tail gas washing tower of the chlorohydrin subsystem and the causticizing wastewater outlet at the bottom of the distillation tower of the propylene oxide rectification subsystem are also connected to the inlet of the electromagnetic heating pipeline gasification reactor; the salt discharge lock hopper at the bottom of the supercritical delayed gasification reactor of the causticizing wastewater treatment subsystem is connected to the chlor-alkali electrolysis cell of the NaCl solution electrolysis subsystem.

2. The clean production device of chlorohydrin process based on closed-loop recycling of chlorine according to claim 1, characterized in that The chlorine dissolver is a microporous pipe chlorine dissolver, a jet pump chlorine dissolver or a T-type straight pipe chlorine dissolver.

3. The clean production device of chlorohydrin process based on closed-loop recycling of chlorine according to claim 1, characterized in that The propylene distributor is a microporous pipeline mixer or a jet pump mixer, and the chlorohydrinization reactor is a pipeline reactor with an internal mixing element reinforcement, a single-tower chlorohydrin reactor, a single-tower multi-tower chlorohydrin reactor in series, a tube-tower chlorohydrin reactor or a tube reactor.

4. The clean production device of chlorohydrin process based on closed-loop recycling of chlorine according to claim 1, characterized in that The causticizing reaction is carried out in a pipeline causticizing reactor, and the NaOH content in the causticizing wastewater is controlled at 0.01wt% to 1.3wt%.

5. The clean production device of alkylene oxide chlorohydrin process based on chlorine closed-loop recycling according to claim 1, characterized in that In the caustic wastewater supercritical gasification device treatment subsystem, the caustic wastewater at the bottom of the stripping tower is pressurized to ≥22.1MPa by a high-pressure pump, and then heat exchanged with the supercritically gasified synthesis gas and supercritical high-temperature purified water mixed phase; the preheated caustic waste liquid is heated to 400-700℃ by an electromagnetic heating tubular reactor for supercritical gasification reaction, and the supercritical gasified gas and liquid enter the supercritical delayed gasification reactor and stay for 1-180 minutes to generate a mixture of synthesis gas and supercritical high-temperature purified water and a high-concentration NaCl slurry; the extracted synthesis gas and supercritical high-temperature purified water mixed phase are separated from the gas and liquid after heat exchange with the high-pressure dissolved oxygen caustic waste liquid, and the synthesis gas is discharged and the purified water is reused; the high-concentration Na The Cl slurry is switched through the bottom lock hopper of the supercritical delayed gasification reactor, and is diluted with part of the purified water into 31.5wt%-36.1wt% concentrated brine and then returned to the electrolyzer for recycling; the electromagnetic heating tubular reactor is a tubular reactor in which the cylinder wall and the internal self-mixing strengthening internal components generate eddy current self-heating when high-frequency alternating current passes through the coil to generate an alternating magnetic field under the action of the electromagnetic heating controller, and the self-mixing strengthening internal components are regular packing type, X-cross sheet type or spiral sheet type; a funnel-shaped liquid extraction port is arranged at the center of the supercritical delayed gasification reactor, the funnel is connected to the upper part of the reactor, a gas-liquid mixed phase discharge port is arranged at the top of the reactor, and two or more salt discharge lock hoppers are arranged at the bottom of the reactor.

6. The clean production device of alkylene oxide chlorohydrin process based on chlorine closed-loop recycling according to claim 1, characterized in that The chlor-alkali electrolyzer is an oxygen anion membrane electrolyzer or an anion membrane electrolyzer.

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