Clean production method of propylene oxide chlorohydrin by chlorine closed-loop circulation
By using NaOH electrolytic solution to rapidly causticize and supercritical gasification in the chlorohydrin propylene oxide process, the problems of high water consumption, high pollution and full resource difficulty in traditional processes are solved, and closed-loop recycling of chlorine and low-energy production of propylene oxide are achieved.
Patent Information
- Application Number
- CN202411865897.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-17
- Publication Date
- 2025-04-04
AI Technical Summary
The traditional chlorohydrin process produces propylene oxide process has problems such as high water consumption, high pollution and full resource utilization of caustic waste liquids, resulting in environmental pollution and equipment corrosion.
Through the NaOH electrolytic solution, the caustic waste liquid is supercritical gasified and the gas-liquid mixed phase is separated from the NaCl phase, the high-pressure locking bucket is discharged, and the waste heat of the purified water is recovered and recycled to achieve closed-loop recycling of chlorine.
The chlorohydrin method of low water consumption, low energy consumption, and closed-loop chlorine recycling has been achieved to clean the production of propylene oxide, reducing the risks of pollution and corrosion, and improving the economic and environmental protection of the process.
Smart Images
Figure CN119751382A_ABST
Abstract
Description
1. Technical Field
[0001] The invention provides a clean production method of propylene oxide chlorohydrin process with closed-loop chlorine circulation, and relates to the field of fine chemicals. 2. Background technology
[0002] The chlorohydrin process for producing alkylene oxide is to prepare hypochlorous acid by mixing chlorine gas and water. 2 -C 5 Olefins react with hypochlorous acid to obtain chlorohydrins, which then react with slaked lime or caustic soda to produce alkylene oxides, which are then separated by ordinary distillation methods to obtain refined alkylene oxides. This process 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 method. However, the traditional chlorohydrin method is less environmentally friendly, consumes a lot of water resources and chlorine, and the caustic wastewater containing chlorides is difficult to treat, polluting the environment. At the same time, the chloric acid produced is also seriously corrosive to the equipment. 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 chlorides and more than 2 tons of CaCl 2 Waste residue.
[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 in the United States uses 10% to 20% NaOH electrolyte to replace the lime milk (mainly Ca(OH) 2 ), the mass concentration of propylene glycol (PDO) and dichloropropane (DCP) in the saponification waste liquid is greatly reduced, and a relatively pure salt solution (the main components are NaCl and H 2O). The caustic 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 used to participate in the saponification reaction and recycled to improve the economic efficiency of the reaction. Although this improvement can effectively reduce the wastewater and waste residue after saponification (the main component is CaCl 2 ) is generated, reducing the pollution to soil and water sources, but the refining of caustic brine is too difficult to meet the requirements of electrolysis.
[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 invent a chlorine closed-loop cycle propylene oxide chlorohydrin process clean production method. The invention uses a NaOH electrolytic solution to quickly causticize chlorohydrin, supercritically gasify the causticized waste liquid and separate the gas-liquid mixed phase from the NaCl phase, discharge salt through a high-pressure lock bucket, and recycle the waste heat of high-temperature purified water. The NaCl solution diluted with purified water is used to produce chlorine and the NaOH electrolyte is recycled. 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 the 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 method of propylene oxide chlorohydrin process with closed-loop chlorine circulation, comprising the following steps: (1) chlorohydrinization process: firstly, chlorine gas is dissolved into water at 35-45°C through a chlorine dissolver to generate hypochlorous acid, and then enters a chlorohydrinization reactor, and excessive propylene is introduced through a propylene distributor at a molar ratio of chlorine gas to propylene of 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, the solution contains hydrochloric acid in an equal mole to the chloropropanol, and the tail gas flashed out is treated with NaOH After washing, the electrolyte is returned to the propylene recovery system; (2) causticizing step: the chloropropanol solution obtained in the previous step is quickly mixed with 10% to 20% NaOH electrolyte according to the molar ratio of sodium hydroxide / chloropropanol + hydrochloric acid of 1.0 to 1.2:1, and sent to a pipeline reactor for causticizing reaction. The causticizing reaction temperature is controlled at 90 to 95°C, and the reaction time is controlled at 0.5 to 2 seconds. Then the reaction liquid is sent to a stripping tower to obtain 90% to 95% crude propylene oxide. The absolute pressure at the top of the stripping tower is 25 to 65 Kpa. A 2.5% NaCl-containing propylene oxide is obtained from the bottom of the stripping tower. ~5.5wt% causticized wastewater; (3) distillation process: the crude propylene oxide with a content of 90% to 95% produced in the causticizing process is sent to the propylene oxide front distillation tower and the distillation tower. The front distillation tower and the distillation tower are connected in series. The crude propylene oxide material first passes through the front distillation tower, and the finished propylene oxide is discharged from the top of the front distillation tower. The high-boiling point components are discharged from the top of the distillation tower. The propylene oxide front distillation tower and the distillation tower are operated at normal pressure, and the bottom temperature is controlled at 50℃~85℃. The causticized wastewater is discharged from the bottom of the distillation tower; (4) causticized wastewater treatment process: the causticized wastewater and tail gas washing waste liquid from the stripping tower The causticized wastewater at the bottom of the distillation tower is supercritically gasified and separated by electromagnetic heating to generate synthesis gas, purified water and high-concentration NaCl slurry. The high-concentration NaCl slurry is diluted with part of the purified water to become 31.5%-36.1% concentrated brine and then returned to the electrolytic cell for recycling. The remaining purified water is returned to the chlorohydrinization process. (5) NaCl solution electrolysis process: 31.5%-36.1% concentrated brine is electrolyzed in the electrolytic cell, the generated chlorine is returned to the chlorohydrinization process for generating hypochlorous acid, and 10%-20% NaOH electrolyte is returned to the causticization process for rapid causticization.
[0009] The chlorine dissolver for dissolving chlorine gas into water to generate hypochlorous acid 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 during the causticizing reaction in a pipeline 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 used 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. Rectification tower 11. Chlor-alkali electrolyzer A. Propylene inlet B. Purified tail gas outlet C. Synthesis gas 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 feed pump 13. Heat exchanger 14. Electromagnetic heating tubular reactor 15. Electromagnetic heating controller 16. Supercritical delayed gasification reactor 17. Gas-liquid separator G, NaOH caustic waste liquid inlet L, synthesis gas outlet M, purified water outlet N, concentrated 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 method of propylene oxide chlorohydrin process with chlorine closed-loop circulation, comprising the following steps: (1) chlorohydrin process: firstly, chlorine gas is dissolved into water at 35-45°C through a chlorine dissolving device (1) to generate hypochlorous acid, and then enters a chlorohydrin reactor (3), and an excess of propylene is introduced through a propylene inlet A of a propylene distributor (2) at a molar ratio of chlorine gas to propylene of 1:1.01-1.1. The reaction pressure is normal pressure or slightly higher than normal pressure, and the reaction temperature is 50-70°C to generate a solution containing 3.0wt%-6.0wt% of chloropropanol, and the solution contains hydrochloric acid in an equal molar amount to the chloropropanol. The tail gas flashed out through a flash tower (4) is washed with NaOH in an alkali washing tower (5). After washing, the electrolyte is sent back to the propylene recovery system through the purified tail gas outlet B; (2) causticizing step: the chloropropanol solution obtained in the previous step is quickly mixed with 10% to 20% NaOH electrolyte according to the molar ratio of sodium hydroxide / chloropropanol + hydrochloric acid of 1.0 to 1.2:1, and sent to the pipeline causticizing reactor (6) for causticizing reaction. The causticizing reaction temperature is controlled at 90 to 95°C, and the reaction time is controlled at 0.5 to 2 seconds. Then the reaction liquid is sent to the stripping tower (7) to obtain 90% to 95% crude propylene oxide. The absolute pressure at the top of the stripping tower (7) is 25 to 65 KPa. A causticizing waste gas containing 2.5 to 5.5 wt% of NaCl is obtained from the bottom of the stripping tower (7). (3) distillation process: the crude propylene oxide with a content of 90% to 95% produced in the causticizing process is fed into a propylene oxide front distillation tower (9) and a distillation tower (10). The front distillation tower (9) and the distillation tower (10) are connected in series. The crude propylene oxide material first passes through the front distillation tower (9). The finished propylene oxide is discharged from the top of the front distillation tower (9). The high boiling point components are discharged from the top of the distillation tower (10). The propylene oxide front distillation tower (9) and the distillation tower (10) are operated at normal pressure. The bottom temperature of the tower is controlled at 50°C to 85°C. The causticized wastewater is discharged from the bottom of the distillation tower (10); (4) causticized wastewater treatment process: the causticized wastewater from the stripping tower (7) and the washing wastewater discharged from the bottom of the tail gas washing tower (5) are treated with a causticized wastewater treatment process. The wastewater from the washing and distillation tower (10) bottom is subjected to supercritical gasification and separation by electromagnetic heating in a supercritical gasification reaction device (8) to generate synthesis gas, purified water and high-concentration NaCl slurry. The high-concentration NaCl slurry is diluted by part of the purified water to become 31.5%-36.1% concentrated brine and then returned to the chlor-alkali electrolysis cell (11) for recycling. The remaining purified water is returned to the chlorohydrinization process. (5) NaCl solution electrolysis process: the 31.5%-36.1% concentrated brine is electrolyzed in the chlor-alkali electrolysis cell (11). The generated chlorine is returned to the chlorohydrinization process for generating hypochlorous acid, and the 10%-20% NaOH electrolyte is returned to the causticization process for rapid causticization.
[0022] The chlorine dissolving device (1) for dissolving chlorine gas into water to generate hypochlorous acid is a microporous pipeline chlorine dissolving device, a jet pump chlorine dissolving device or a T-type straight pipe chlorine dissolving device.
[0023] The propylene distributor (2) is a microporous pipeline mixer or a jet pump mixer, and the chlorohydrinization reactor (3) 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] The caustic waste water at the bottom of the stripping tower (7) is pressurized to ≥22.1MPa by a high-pressure pump (12), and then heat exchanged with the supercritical gasified synthesis gas and supercritical high-temperature purified water mixed phase through a heat exchanger (13); the preheated caustic waste liquid is heated to 400-700°C by an electromagnetic heating tubular reactor (14) to perform a supercritical gasification reaction, and the supercritical gasified gas and liquid enter a supercritical delayed gasification reactor (16) and stay there 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 high-pressure caustic waste liquid after heat exchange, and the synthesis gas is discharged from the synthesis gas outlet L at the top of the gas-liquid separation tank (17), and the purified water discharged from the bottom is reused; the high-concentration NaCl slurry is passed through a supercritical The bottom lock hopper of the supercritical delayed gasification reactor (16) is switched, and the concentrated brine is diluted with part of the purified water to 31.5%-36.1% and then returned to the chlor-alkali electrolyzer (11) for recycling; the electromagnetic heating tubular reactor (14) is that when the high-frequency alternating current generates an alternating magnetic field through the coil under the action of the electromagnetic heating controller (15), the tubular reactor wall and the internal self-mixing strengthening internal components generate eddy current self-heating, thereby achieving uniform heating of the 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 (16), 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) used 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 24 MPa and 450 °C, 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 H in the synthesis gas is 2 The anion membrane electrolyzer is used to generate NaOH electrolyte, H 2and chlorine, NaOH electrolyte and chlorine are recycled, H 2 Mixed with synthesis gas for chemical synthesis.
[0029] (2) Under the conditions of 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 H in the synthesis gas is 2 The oxygen anion membrane electrolyzer only produces NaOH electrolyte and chlorine gas, and the electrolysis energy consumption 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 method of propylene oxide chlorohydrin process with chlorine closed-loop circulation provided by the present invention is to causticize with NaOH, treat the causticized wastewater with supercritical gasification, and then use it for electrolysis to produce NaOH electrolyte and chlorine 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 using the supercritical water characteristics. The organic matter in the causticized wastewater is completely gasified to produce H-containing 2 The synthesis gas is more than 60%, the COD removal rate is greater than 99%, the brine concentration can be flexibly adjusted with low cost and low energy consumption according to the needs of the electrolyzer, the cost and investment of resource management of NaOH causticized waste liquid are reduced by more than 70% compared with traditional treatment methods, the high water consumption and high pollution of the chlorohydrin method are eliminated, the propylene oxide yield is increased by 3 percentage points, the selectivity is increased by 10%, and the closed-loop utilization of chlorine is realized.
Claims
1. A clean production method of propylene oxide chlorohydrin process with chlorine closed-loop circulation, characterized in that The following steps are involved: (1) Chlorohydrinization process: chlorine is first dissolved into water at 35-45°C through a chlorine dissolver to generate hypochlorous acid, which then enters a chlorohydrinization reactor, and an excess of propylene is introduced through a propylene distributor at a molar ratio of chlorine to propylene of 1:1.01-1.
1. The reaction pressure is normal pressure or higher than normal pressure but not higher than 10KPa (gauge pressure), and the reaction temperature is 50-70°C to generate a solution containing 3.0wt% to 6.0wt% of chloropropanol. The solution contains hydrochloric acid with an equimolar concentration to that of chloropropanol. The flashed tail gas is washed with NaOH electrolyte and then sent back to the propylene recovery system; (2) ) Causticizing step: the chloropropanol solution obtained in the previous step is quickly mixed with 10wt% to 20wt% NaOH electrolyte according to the molar ratio of sodium hydroxide to (chloropropanol and hydrochloric acid) of 1.0 to 1.2:1, and sent to a pipeline reactor for causticizing reaction. The causticizing reaction temperature is controlled at 90 to 95°C, and the reaction time is controlled at 0.5 to 2 seconds. Then the reaction liquid is sent to a stripping tower to obtain 90wt% to 95wt% crude propylene oxide. The absolute pressure at the top of the stripping tower is 25 to 65Kpa, and a 2.5 to 5.5wt% NaCl-containing propylene oxide is obtained from the bottom of the stripping tower. Causticized wastewater; (3) distillation process: the crude propylene oxide with a content of 90wt% to 95wt% produced in the causticizing process is fed into a propylene oxide fore-distillation tower and a distillation tower. The fore-distillation tower and the distillation tower are connected in series. The crude propylene oxide material first passes through the fore-distillation tower, and the finished propylene oxide is extracted from the top of the fore-distillation tower. The high-boiling point components are discharged from the top of the distillation tower. The propylene oxide fore-distillation tower and the distillation tower are operated at normal pressure, and the bottom temperature of the tower is controlled at 50℃ to 85℃. The causticized wastewater is discharged from the bottom of the distillation tower; (4) causticized wastewater treatment process: the causticized wastewater from the stripping tower, the tail gas washing waste liquid and the caustic wastewater at the bottom of the distillation tower The chemical wastewater is supercritically gasified and separated by electromagnetic heating to generate synthesis gas, purified water and NaCl slurry. The NaCl slurry is diluted with part of the purified water to become 31.5wt%-36.1wt% concentrated brine and then returned to the electrolytic cell for recycling. The remaining purified water is returned to the chlorohydrinization process. (5) NaCl solution electrolysis process: 31.5wt%-36.1wt% concentrated brine is electrolyzed in the electrolytic cell. The generated chlorine is returned to the chlorohydrinization process for generating hypochlorous acid, and 10wt%-20wt% NaOH electrolyte is returned to the causticization process for rapid causticization.
2. The clean production method of propylene oxide chlorohydrin process with a chlorine closed-loop cycle according to claim 1, characterized in that The chlorine dissolver for dissolving chlorine gas into water to generate hypochlorous acid is a microporous pipeline chlorine dissolver, a jet pump chlorine dissolver or a T-type straight tube chlorine dissolver.
3. A clean production method of propylene oxide chlorohydrin process with chlorine closed-loop circulation 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 method of propylene oxide chlorohydrin process with a chlorine closed-loop cycle according to claim 1, characterized in that The causticizing reaction is carried out in a pipeline reactor, and the NaOH content in the causticizing wastewater is controlled at 0.01wt% to 1.3wt%.
5. The clean production method of propylene oxide chlorohydrin process with chlorine closed-loop circulation according to claim 1, characterized in that 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°C 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 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 NaCl slurry is passed through the supercritical delayed gasification reactor. The bottom lock hopper of the supercritical delayed gasification reactor is switched, and the concentrated brine is diluted with part of the purified water to 31.5wt%-36.1wt% and then returned to the electrolyzer for recycling; the electromagnetic heating tubular reactor is under the action of the electromagnetic heating controller, and the high-frequency alternating current generates an alternating magnetic field through the coil, and the tube wall of the tubular reactor and the internal self-mixing strengthening internal components generate eddy current self-heating; 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, 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 method of propylene oxide chlorohydrin process with chlorine closed-loop circulation according to claim 1, characterized in that The chlor-alkali electrolyzer used is an oxygen anion membrane electrolyzer or an anion membrane electrolyzer.