Chlor-alkali industry hydrogen purification system and purification method thereof

Abstract

The application provides a chlor-alkali industry hydrogen purification system and a purification method thereof, and belongs to the technical field of chlor-alkali industry by-product resource utilization and gas deep purification, solves the problems of poor impurity removal effect, low hydrogen recovery rate and low product purity of the existing chlor-alkali industry hydrogen purification system and method, and the purification system comprises a hydrogen compressor, a pretreatment tower, an online multi-component purity analyzer, a dechlorination tower, a deoxygenation tower, a PSA system, a DCS system and the like, the flow ratio of raw material gas and PSA desorption gas is 10:1, mixed gas passes through a hydrogen buffer tank, a hydrogen compressor, a pretreatment tower, a dechlorination tower, a deoxygenation tower, a cooler, a gas-liquid separator and a PSA system, and is finally collected. Through the purification technology research of the chlor-alkali hydrogen+PSA desorption gas mixed system, the mixed gas is pressurized, pretreated, dechlorinated, deoxygenated and PSA, and the purity reaches the high-purity hydrogen 99.999% standard.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization of by-products in the chlor-alkali industry and deep purification of gases. Specifically, it relates to a purification system and corresponding purification method for hydrogen in the chlor-alkali industry. It is particularly suitable for the deep purification of hydrogen from the electrolysis of brine process and PSA (pressure swing adsorption) desorption gas to high-purity hydrogen standards, and significantly improves the PSA hydrogen recovery rate. It belongs to the interdisciplinary technical field of hydrogen energy production and clean energy utilization. Background Technology

[0002] In the electrolysis of brine in the chlor-alkali industry, the surplus hydrogen has an initial purity of 98.67%-99.33%. With the development of the hydrogen energy industry, this surplus hydrogen, characterized by its high purity, relatively well-defined impurity types, and stable source, represents a low-cost clean energy resource with significant development potential. As the "dual-carbon" goal is further promoted, the demand for hydrogen energy, as a zero-carbon emission energy carrier, is experiencing explosive growth in fuel cells, the electronics industry, fine chemical synthesis, and hydrogen metallurgy. The resource utilization of surplus hydrogen from the chlor-alkali industry has become an important direction for energy conservation, carbon reduction, and industrial chain extension in the chemical industry.

[0003] Therefore, developing a hydrogen purification system and method that can efficiently process the "chlor-alkali hydrogen + PSA desorption gas" mixed system, achieve deep removal of impurities, significantly improve hydrogen recovery rate and product purity, and is low in energy consumption, highly stable, and suitable for industrial-scale production, is of great practical significance and industrial application value for promoting the resource-based upgrading of chlor-alkali industry by-products, reducing hydrogen production costs, and helping the high-quality development of the hydrogen energy industry chain. Summary of the Invention

[0004] The purpose of this invention is to provide a hydrogen purification system and method for the chlor-alkali industry, so as to solve the problems of poor impurity removal effect, low hydrogen recovery rate and low product purity in existing hydrogen purification systems and methods for the chlor-alkali industry.

[0005] The technical solution of the present invention is: a hydrogen purification system for chlor-alkali industry, comprising a first hydrogen buffer tank, a hydrogen compressor, and a second hydrogen buffer tank connected in sequence. The inlet end of the first hydrogen buffer tank is connected to a raw material hydrogen delivery pipeline and a desorption gas recycling pipeline provided by the chlor-alkali system. The second hydrogen buffer tank is connected to a regeneration pretreatment tower and an adsorption pretreatment tower. The rear ends of the regeneration pretreatment tower and the adsorption pretreatment tower are connected to a tail gas absorption tower via a vacuum pump. The front ends of the regeneration pretreatment tower and the adsorption pretreatment tower are connected to a dechlorination tower. The dechlorination tower is connected in sequence to a deoxygenation tower, a cooler, a gas-liquid separator, and a PSA system. The PSA system is connected to a qualified hydrogen storage tank and a desorption gas storage tank. The second hydrogen buffer tank is equipped with a first automatic valve and a second automatic valve between the adsorption pretreatment tower and the regeneration pretreatment tower, respectively. The adsorption pretreatment tower and the regeneration pretreatment tower are equipped with a third automatic valve and a fourth automatic valve between the dechlorination tower, respectively. The adsorption pretreatment tower and the regeneration pretreatment tower are equipped with a fifth automatic valve and a sixth automatic valve between the rear end of the adsorption pretreatment tower and the tail gas absorption tower. The fifth automatic valve and the sixth automatic valve are interlocked with the vacuum pump. The system also includes a DCS system.

[0006] As a further improvement of the present invention, the raw material hydrogen transmission pipeline is equipped with an interlocked seventh automatic valve and a vortex flow meter, and the desorption gas return pipeline is equipped with an interlocked regulating valve and a vortex flow meter.

[0007] As a further improvement of the present invention, a first pressure transmitter is provided on the first hydrogen buffer tank, the second hydrogen buffer tank, the regeneration pretreatment tower, the adsorption pretreatment tower, the dechlorination tower, the tail gas absorption tower, the deoxygenation tower, the qualified hydrogen storage tank and the desorption gas storage tank.

[0008] As a further improvement of the present invention, differential pressure transmitters are provided on the dechlorination tower and the deoxygenation tower respectively.

[0009] As a further improvement of the present invention, the first hydrogen buffer tank is equipped with an online hydrogen purity analyzer.

[0010] As a further improvement of the present invention, online multi-component purity analyzers are respectively installed between the adsorption pretreatment tower and the dechlorination tower, between the PSA system and the qualified hydrogen storage tank, and between the PSA system and the desorption gas storage tank.

[0011] As a further improvement of the present invention, a thermal resistance temperature transmitter is provided at each end of the cooler.

[0012] As a further improvement of the present invention, the gas-liquid separator is equipped with a second pressure transmitter, a level gauge and an automatic valve for the sewage discharge pipeline, and the level gauge and the automatic valve for the sewage discharge pipeline are interlocked.

[0013] A purification method for a hydrogen purification system in a chlor-alkali industry includes the following steps: Step 1: The flow ratio of the raw gas and the PSA desorption gas is 10:1. The two gases are first mixed evenly in the hydrogen buffer tank. After the pressure is set by the hydrogen compressor, the gas enters the hydrogen buffer tank and is finally delivered to the subsequent pretreatment tower in a stable and uniform state. Step 2: The adsorption pretreatment tower and the regeneration pretreatment tower of the pretreatment tower adopt a dual tower mode of adsorption-regeneration alternating operation. When the adsorption pretreatment tower completes the adsorption and impurity removal function, the regeneration pretreatment tower performs regeneration treatment simultaneously to realize continuous pretreatment of the raw gas. Step 3: After passing through the pretreatment tower, the mixed gas is sent to the dechlorination tower. After dechlorination, it enters the deoxygenation tower. The mixed gas, after preliminary purification, passes through a cooler and a gas-liquid separator to cool it to below 40°C. Step 4: The mixed gas enters the PSA system through the gas-liquid separator. The qualified product from the pressure swing adsorption enters the qualified hydrogen storage tank, and the desorbed gas from the pressure swing adsorption enters the desorbed gas storage tank.

[0014] The beneficial effects of this invention are as follows: The purification system of this invention includes: a hydrogen compressor, a pretreatment tower, an online multi-component purity analyzer, a dechlorination tower, a deoxygenation tower, a PSA system, a DCS system, etc. The flow ratio of the raw gas to the PSA desorption gas is 10:1. The two gases first flow into the buffer tank before the compressor, and uniform mixing is achieved through the stabilization of flow and equalization of pressure in the tank.

[0015] In the hydrogen compressor, the flow ratio of raw material gas to PSA desorption gas is 10:1. The two gases first enter the buffer tank before the compressor, where they are uniformly mixed through the stabilization of flow and equalization of pressure, effectively avoiding the impact of flow fluctuations on the operation of the compressor. After the mixed gas is compressed to the process set pressure by the piston compressor, it enters the hydrogen buffer tank at the back end to further stabilize the pressure and flow, and is finally delivered to the subsequent pretreatment tower in a stable and uniform state.

[0016] The pretreatment tower adopts a dual-tower mode with alternating adsorption and regeneration. While one tower completes its adsorption and impurity removal function, the other tower simultaneously undergoes regeneration, achieving continuous pretreatment of the raw gas. The operation process is as follows: after one tower becomes saturated, it automatically enters regeneration mode via a pressure transmitter and automatic valve. Upon completion of regeneration, the tower switches back to regeneration mode based on performance indicators, ensuring that one tower is always operating while the other is regenerating, thus guaranteeing continuous and stable process operation. The main functions of the pretreatment tower are: removing impurities and corrosive contaminants. To prevent corrosion of subsequent equipment and catalyst poisoning, a mixed adsorbent of activated carbon and alumina is selected for the pretreatment tower.

[0017] High-purity hydrogen produced by the PSA system is selected as the drying carrier gas. Its high purity can avoid the introduction of new impurities during the regeneration process, ensuring that the activity of the adsorbent is not affected after regeneration. A vacuum pump and a tail gas absorption tower are equipped at the back end of the regeneration tower. The vacuum pump enhances the desorption efficiency of impurities on the surface of the adsorbent by reducing pressure. The tail gas containing impurities generated by desorption is passed into the tail gas absorption tower for harmless treatment to ensure that the emission meets the standards, thus balancing the regeneration effect and environmental protection requirements.

[0018] As the core monitoring unit of the hydrogen purification system in the chlor-alkali industry, the online multi-component purity analyzer is mainly used to track the purity of key components (water, hydrogen, and oxygen) in real time after the feed gas pretreatment and before the product hydrogen production. It provides accurate data support for the switching of the dual-tower pretreatment and the adjustment of process parameters of the PSA main unit, ensuring that the purity of the product hydrogen is consistently up to standard. Conventional online equipment types are thermal conductivity and chromatographic. To achieve high-precision, rapid, and stable monitoring of key components, this process selects a chromatographic online multi-component purity analyzer.

[0019] A dechlorination tower is a fixed bed containing dechlorinating agents. The mixed gas often contains some chloride ions, and chloride is a common catalyst poison. Chloride ions are highly mobile, not only corroding equipment but also reducing catalyst activity and leading to downstream catalyst poisoning. Therefore, to protect valuable catalysts in downstream processes and reduce equipment corrosion, a dechlorination tower is necessary.

[0020] The deoxygenation tower is a fixed bed containing deoxygenation catalysts, primarily using precious metal catalysts, which offer high efficiency and deoxygenation activity. It is mainly used to remove oxygen from mixed gases, achieving a deoxygenation depth of 0.1 ppm. After preliminary purification, the mixed gas passes through a cooler and a gas-liquid separator to cool it to below 40°C, which also facilitates the condensation and removal of water from the hydrogen, preparing it for PSA purification.

[0021] This invention, through research on purification technology of the "chlor-alkali hydrogen + PSA desorption gas" mixed system, can efficiently process the "chlor-alkali hydrogen + PSA desorption gas" mixed system. After mixed gas pretreatment, dechlorination + deoxygenation + PSA, the purity of the mixed gas reaches the high-purity hydrogen standard of 99.999%, significantly improving the PSA hydrogen recovery rate, achieving deep removal of impurities, significantly improving the hydrogen recovery rate, and also possessing low energy consumption, high stability, and suitability for industrial-scale hydrogen purification systems and methods. Attached Figure Description

[0022] Figure 1 This is a structural diagram of the purification system of the present invention.

[0023] In the diagram: 1-Raw hydrogen delivery pipeline, 2-Seventh automatic valve, 3-Desorption gas recycling pipeline, 4-Regulating valve, 5-Vortex flow meter, 7-First hydrogen buffer tank, 8-First pressure transmitter, 9-Online hydrogen purity analyzer, 10-Conventional automatic valve, 11-Hydrogen compressor, 13-Second hydrogen buffer tank, 15-First automatic valve, 16-Second automatic valve, 17-Regeneration pretreatment tower, 18-Sixth automatic valve, 20-Fourth automatic valve, 21-Fifth automatic valve, 22-Adsorption pretreatment tower, 2 4-Third automatic valve, 25-Online multi-component purity analyzer, 26-Differential pressure transmitter, 28-Dechlorination tower, 31-Vacuum pump, 32-Tail gas absorption tower, 35-Deoxygenation tower, 38-Resistance temperature transmitter, 39-Cooler, 42-Gas-liquid separator, 43-Second pressure transmitter, 45-Level gauge, 46-Automatic valve for sewage discharge pipeline, 47-PSA system, 51-Qualified hydrogen storage tank, 54-Releasing gas storage tank, 56-Releasing gas collection main pipe, 57-DCS system, 58-Regeneration pipeline. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1 like Figure 1 As shown, a hydrogen purification system for chlor-alkali industry includes a first hydrogen buffer tank 7, a hydrogen compressor 11, and a second hydrogen buffer tank 13 connected in sequence. The inlet of the first hydrogen buffer tank 7 is connected to a raw material hydrogen delivery pipeline 1 and a desorption gas recycling pipeline 3 provided by the chlor-alkali system. The second hydrogen buffer tank 13 is connected to a regeneration pretreatment tower 17 and an adsorption pretreatment tower 22. The rear ends of the regeneration pretreatment tower 17 and the adsorption pretreatment tower 22 are connected to a tail gas absorption tower 32 via a vacuum pump 31. The front ends of the regeneration pretreatment tower 17 and the adsorption pretreatment tower 22 are connected to a dechlorination tower 28. The dechlorination tower 28 is connected in sequence to a deoxygenation tower 35, a cooler 39, a gas-liquid separator 42, and a PSA system 47. The PSA system 47 is connected to a qualified hydrogen storage tank 51 and a desorption gas storage tank 54. A first automatic valve 15 and a second automatic valve 16 are respectively provided between the second hydrogen buffer tank 13 and the adsorption pretreatment tower 22 and the regeneration pretreatment tower 17. A third automatic valve 24 and a fourth automatic valve 20 are respectively provided between the adsorption pretreatment tower 22 and the regeneration pretreatment tower 17 and the dechlorination tower 28. A fifth automatic valve 21 and a sixth automatic valve 18 are provided between the rear end of the adsorption pretreatment tower 22 and the regeneration pretreatment tower 17 and the tail gas absorption tower 32. The fifth automatic valve 21 and the sixth automatic valve 18 are interlocked with the vacuum pump 31. The system also includes a DCS system 57.

[0026] The raw material hydrogen transmission pipeline 1 is equipped with an interlocked seventh automatic valve 2 and a vortex flow meter 5, and the desorption gas return pipeline 3 is equipped with an interlocked regulating valve 4 and a vortex flow meter 5. The first hydrogen buffer tank 7, the second hydrogen buffer tank 13, the regeneration pretreatment tower 17, the adsorption pretreatment tower 22, the dechlorination tower 28, the tail gas absorption tower 32, the deoxygenation tower 35, the qualified hydrogen storage tank 51, and the desorption gas storage tank 54 are each equipped with a first pressure transmitter 8.

[0027] Differential pressure transmitters 26 are installed on dechlorination tower 28 and deoxygenation tower 35 respectively. An online hydrogen purity analyzer 9 is installed on the first hydrogen buffer tank 7. Online multi-component purity analyzers 25 are installed between adsorption pretreatment tower 22 and dechlorination tower 28, between PSA system 47 and qualified hydrogen storage tank 51, and between PSA system 47 and desorption gas storage tank 54 respectively. Resistance temperature transmitters 38 are installed at both ends of cooler 39. A second pressure transmitter 43, a level gauge 45, and an automatic drain valve 46 are installed on gas-liquid separator 42; the level gauge 45 and the automatic drain valve 46 are interlocked.

[0028] A purification method for a hydrogen purification system in a chlor-alkali industry includes the following steps: Step 1: The flow ratio of the raw material gas and the PSA desorption gas is 10:1. The two gases are first mixed evenly in the hydrogen buffer tank 7, and then the hydrogen buffer tank 13 is entered after the pressure is set by the hydrogen compressor 11. Finally, the gas is delivered to the subsequent pretreatment tower in a stable and uniform state. Step 2: The adsorption pretreatment tower 22 and the regeneration pretreatment tower 17 of the pretreatment tower adopt a dual tower mode of adsorption-regeneration alternating operation. When the adsorption pretreatment tower 22 completes the adsorption and impurity removal function, the regeneration pretreatment tower 17 simultaneously performs regeneration treatment to realize continuous pretreatment of raw gas. Step 3: After passing through the pretreatment tower, the mixed gas is sent to the dechlorination tower 28. After dechlorination, it enters the deoxygenation tower 35. The mixed gas after preliminary purification then passes through the cooler 39 and the gas-liquid separator 42 to cool the mixed gas to below 40°C. Step 4: The mixed gas enters the PSA system 47 through the gas-liquid separator 42, the qualified product of pressure swing adsorption enters the qualified hydrogen storage tank 51, and the desorbed gas of pressure swing adsorption enters the desorbed gas storage tank 54.

[0029] Purification Principle and Process: The raw material gas from the hydrogen delivery pipeline 1 provided by the chlor-alkali system and the desorption gas collection manifold 56 from the subsequent desorption gas buffer tank 54 of the PSA system 47 are delivered to the desorption gas reuse pipeline 3. The flow rates of the two gas sources are controlled by interlocking the pipe diameter and the seventh automatic valve 2, regulating valve 4, and vortex flow meter 5 on the pipeline. The flow ratio of the raw material gas to the PSA desorption gas is 10:1. The two gases first flow into the first hydrogen buffer tank 7 before the compressor. The first pressure transmitter 8 is mounted on the top of the tank. The first hydrogen buffer tank 7 achieves uniform mixing through flow stabilization and pressure equalization, effectively avoiding the impact of flow fluctuations on the operation of the hydrogen compressor 11. After the mixed gas is compressed to the process set pressure by the piston hydrogen compressor 11, it enters the second hydrogen buffer tank 13 at the rear end. The first pressure transmitter 14 on the top of the buffer tank detects the pressure and further stabilizes the pressure and flow rate, finally delivering it to the subsequent pretreatment tower in a stable and uniform state. An online hydrogen purity analyzer 9 is installed on the pipeline after the first hydrogen buffer tank 7 to detect the purity of the mixed gas in real time. Conventional automatic valves 10 are installed at the front and rear ends of the hydrogen compressor 11 to control the flow rate and ensure the stable operation of the hydrogen compressor 11.

[0030] The mixed gas is transported via pipeline to the pretreatment tower regeneration pretreatment tower 17 and adsorption pretreatment tower 22. The regeneration pretreatment tower 17 and adsorption pretreatment tower 22 monitor the bed adsorption load in real time via the first pressure transmitter 8 inside the tower. When the adsorbent reaches the saturation threshold, the system automatically triggers the switching of the first automatic valve 15, the second automatic valve 16, the fourth automatic valve 20, and the third automatic valve 24. Specifically, one of the first automatic valve 15 and the second automatic valve 16, and the fourth automatic valve 20 and the third automatic valve 24 are open, while the other is closed. The pretreatment tower immediately exits the adsorption state and enters the regeneration mode. After the regeneration process is completed, it automatically switches back to the standby adsorption state according to the set interlocking conditions, always maintaining a dynamic balance of "one tower working online and one tower regenerating offline," ensuring the continuous and stable operation of the entire pretreatment process.

[0031] High-purity hydrogen produced by the PSA system 47 is selected as the drying carrier gas and enters two regeneration pipelines 58. The gas entering the pretreatment tower (regeneration) is controlled by conventional automatic valves 10 installed on these pipelines. Its high purity prevents the introduction of new impurities during regeneration, ensuring that the activity of the adsorbent remains unaffected after regeneration. A vacuum pump 31 and a tail gas absorption tower 32 are connected downstream of the regeneration pretreatment tower 17. A first pressure transmitter 8 is installed at the top of the tail gas absorption tower 32 to monitor its operating pressure. The vacuum pump 31 is interlocked with the sixth automatic valve 18 and the fifth automatic valve 21, with one valve open and the other closed. The vacuum pump 31 enhances the desorption efficiency of impurities on the adsorbent surface by reducing pressure. The tail gas containing impurities generated during desorption is then passed into the tail gas absorption tower 32 for harmless treatment, ensuring compliance with emission standards. An online multi-component purity analyzer 25 is installed downstream of the pretreatment tower to monitor and analyze the indicators of the pretreated mixed gas in real time.

[0032] The mixed gas is delivered to the dechlorination tower 28 via a conventional automatic valve 10 installed on the pipeline. The dechlorination tower 28 is equipped with a first pressure transmitter 8 and a differential pressure transmitter 26 for monitoring the replacement of the dechlorinating agent in the dechlorination tower 27. After dechlorination, the gas enters the deoxygenation tower 35 via the same conventional automatic valve 10 installed on the pipeline. The dechlorination tower 35 is equipped with a first pressure transmitter 8 and a differential pressure transmitter 26 for monitoring the replacement of the deoxygenating agent in the deoxygenation tower 35.

[0033] The pre-purified gas mixture then passes through cooler 39 and gas-liquid separator 42 to cool it to below 40°C, which also facilitates the condensation and discharge of water from the mixture, preparing it for further purification in PSA system 47. Resistance temperature transmitters 38 are installed at both ends of cooler 39 to measure the temperature of the gas mixture. Conventional automatic valves 10 are installed on the pipelines at both ends of cooler 39 to control the flow rate of the gas mixture and the flow rate into gas-liquid separator 42.

[0034] A second pressure transmitter 43, a level gauge 45, and an automatic drain valve 46 are installed on the gas-liquid separator 42. The level gauge 45 and the automatic drain valve 46 are interlocked to promptly discharge the condensate in the mixed gas.

[0035] The gas-liquid separator 42 flows through a conventional automatic valve 10 installed on its pipeline into the PSA system 47. The PSA system 47 employs a 6-1-3 / P process for hydrogen extraction via pressure swing adsorption (PSA) (6 adsorption towers, 1 tower adsorption, 3 pressure equalization cycles, and atmospheric pressure desorption). The adsorbents in the adsorption towers are mainly of two types: activated alumina and three types of molecular sieve adsorbents. The device uses a 6-tower process, with one tower adsorbing, three pressure equalization cycles, and atmospheric pressure desorption in a PSA process. Each adsorption tower undergoes twelve steps in one cycle: adsorption, first equalization desorption, second equalization desorption, third equalization desorption, forward discharge, reverse discharge, rinsing, third equalization rise, second equalization rise, first equalization rise, and final charging. The six adsorption towers are staggered in their execution sequence, forming a closed-loop cycle to ensure continuous feed input and continuous product output.

[0036] The qualified product from pressure swing adsorption (PSA) enters the qualified hydrogen storage tank 51 via an online multi-component purity analyzer 25 and a conventional automatic valve 10. A first pressure transmitter 8 is installed on the top of the qualified hydrogen storage tank to monitor its pressure in real time. The desorbed gas from PSA enters the desorbed gas storage tank 54 via the online multi-component purity analyzer 25 and a conventional automatic valve 10. A first pressure transmitter 8 is also installed on the top of the desorbed gas storage tank 54 to monitor its pressure in real time.

[0037] The DCS system 57 will input and control all the detection indicators and interlocks of this process into the DCS system 57.

[0038] The above description is merely a preferred embodiment of the present invention and is not limited to the present invention. It should be noted that those skilled in the art can make other equivalent modifications and improvements based on the technical teachings provided by the present invention, all of which can achieve the purpose of the present invention and should be considered within the scope of protection of the present invention.

Claims

1. A hydrogen purification system for chlor-alkali industry, characterized in that: The system includes a first hydrogen buffer tank (7), a hydrogen compressor (11), and a second hydrogen buffer tank (13) connected in sequence. The inlet end of the first hydrogen buffer tank (7) is connected to the raw material hydrogen transmission pipeline (1) and the desorption gas recycling pipeline (3) provided by the chlor-alkali system. The second hydrogen buffer tank (13) is connected to the regeneration pretreatment tower (17) and the adsorption pretreatment tower (22). The rear end of the regeneration pretreatment tower (17) and the adsorption pretreatment tower (22) is connected to the tail gas absorption tower (32) through the vacuum pump (31). The front end of the regeneration pretreatment tower (17) and the adsorption pretreatment tower (22) is connected to the dechlorination tower (28). The dechlorination tower (28) is connected in sequence to the deoxygenation tower (35), the cooler (39), the gas-liquid separator (42), and the PSA system (47). The PSA system (47) is connected to the qualified hydrogen storage tank (51) and the desorption gas storage tank (54). The second hydrogen buffer tank (13) is provided with a first automatic valve (15) and a second automatic valve (16) between the adsorption pretreatment tower (22) and the regeneration pretreatment tower (17), respectively. The adsorption pretreatment tower (22) and the regeneration pretreatment tower (17) are provided with a third automatic valve (24) and a fourth automatic valve (20) between the dechlorination tower (28), respectively. The adsorption pretreatment tower (22) and the regeneration pretreatment tower (17) are provided with a fifth automatic valve (21) and a sixth automatic valve (18) between the rear end of the adsorption pretreatment tower (22) and the regeneration pretreatment tower (17) and the tail gas absorption tower (32). The fifth automatic valve (21) and the sixth automatic valve (18) are interlocked with the vacuum pump (31). The system also includes a DCS system (57).

2. The hydrogen purification system for chlor-alkali industry according to claim 1, characterized in that: The raw material hydrogen transmission pipeline (1) is equipped with an interlocked seventh automatic valve (2) and a vortex flow meter (5), and the desorption gas return pipeline (3) is equipped with an interlocked regulating valve (4) and a vortex flow meter (5).

3. The hydrogen purification system for chlor-alkali industry according to claim 2, characterized in that: The first hydrogen buffer tank (7), the second hydrogen buffer tank (13), the regeneration pretreatment tower (17), the adsorption pretreatment tower (22), the dechlorination tower (28), the tail gas absorption tower (32), the deoxygenation tower (35), the qualified hydrogen storage tank (51), and the desorption gas storage tank (54) are each equipped with a first pressure transmitter (8).

4. The hydrogen purification system for chlor-alkali industry according to claim 3, characterized in that: Differential pressure transmitters (26) are respectively installed on the dechlorination tower (28) and the deoxygenation tower (35).

5. A hydrogen purification system for chlor-alkali industry according to claim 4, characterized in that: The first hydrogen buffer tank (7) is equipped with an online hydrogen purity analyzer (9).

6. A hydrogen purification system for chlor-alkali industry according to claim 5, characterized in that: Online multi-component purity analyzers (25) are respectively installed between the adsorption pretreatment tower (22) and the dechlorination tower (28), between the PSA system (47) and the qualified hydrogen storage tank (51), and between the PSA system (47) and the desorption gas storage tank (54).

7. A hydrogen purification system for chlor-alkali industry according to claim 6, characterized in that: The cooler (39) is equipped with a resistance temperature transmitter (38) at both ends.

8. A hydrogen purification system for chlor-alkali industry according to claim 7, characterized in that: The gas-liquid separator (42) is equipped with a second pressure transmitter (43), a level gauge (45) and an automatic valve for the sewage discharge line (46), and the level gauge (45) and the automatic valve for the sewage discharge line (46) are interlocked.

9. The purification method of a hydrogen purification system for chlor-alkali industry according to claim 8, characterized in that: Includes the following steps: Step 1: The flow ratio of the raw material gas and the PSA desorption gas is 10:

1. The two gases are first mixed in the hydrogen buffer tank (7) and then the hydrogen buffer tank (13) is set by the hydrogen compressor (11) and finally delivered to the subsequent pretreatment tower in a stable and uniform state. Step 2: The adsorption pretreatment tower (22) and the regeneration pretreatment tower (17) of the pretreatment tower adopt a dual tower mode of adsorption-regeneration alternating operation. When the adsorption pretreatment tower (22) completes the adsorption and impurity removal function, the regeneration pretreatment tower (17) performs regeneration treatment simultaneously to realize continuous pretreatment of raw gas. Step 3: After passing through the pretreatment tower, the mixed gas is transported to the dechlorination tower (28). After dechlorination, it enters the deoxygenation tower (35). The mixed gas after preliminary purification is then cooled to below 40°C by the cooler (39) and the gas-liquid separator (42). Step 4: The mixed gas enters the PSA system (47) through the gas-liquid separator (42), the qualified product through pressure swing adsorption enters the qualified hydrogen storage tank (51), and the desorbed gas through pressure swing adsorption enters the desorbed gas storage tank (54).

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