A high-low pressure coupled pressure swing adsorption hydrogen extraction system and method

Abstract

The present invention discloses a high-low pressure coupled pressure swing adsorption hydrogen extraction system and method, which solves the technical problems of high investment cost and high operating energy consumption of hydrogen equipment for separating high- and low-pressure raw gases with different hydrogen contents in the prior art. The hydrogen extraction system includes a high-pressure pressure swing adsorption hydrogen extraction device and a low-pressure pressure swing adsorption hydrogen extraction device. The low-pressure product hydrogen external transmission pipe on the low-pressure pressure swing adsorption hydrogen extraction device is respectively connected to each high-pressure adsorption tower in the high-pressure pressure swing adsorption hydrogen extraction device. The separation and purification method is to add a hydrogen storage step to the hydrogen extraction adsorption tower of the high-pressure pressure swing adsorption device, and the product hydrogen of the low-pressure pressure swing adsorption hydrogen extraction device enters the high-pressure adsorption tower for temporary storage when the high-pressure adsorption tower undergoes the hydrogen storage step. The high-pressure adsorption tower undergoes the equalization and pressure boosting step and the final pressure boosting step and then boosts the pressure to output as high-pressure product hydrogen. The present invention eliminates the separate pressurization process of the low-pressure product hydrogen, reduces the investment in compressor equipment, reduces the energy consumption cost of the compressor equipment, and reduces carbon dioxide emissions.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure swing adsorption gas separation, and in particular relates to a high-low pressure coupled pressure swing adsorption hydrogen extraction system and method. Background Art

[0002] Pressure swing adsorption (PSA) hydrogen purification technology is widely used in the petroleum, chemical, and energy sectors. With the development of industrial technology, PSA hydrogen purification technology has become a key component of industrial systems, and the scale of equipment has increased from a few hundred cubic meters per hour to hundreds of thousands of cubic meters per hour. With the continuous expansion of PSA hydrogen extraction technology applications and the continuous increase in equipment scale, the PSA hydrogen extraction process is also constantly improving, and the efficiency of PSA hydrogen extraction is also continuously increasing.

[0003] The adsorption pressure of the pressure swing adsorption hydrogen extraction device varies in a wide range. For example, the pressure of gas sources such as coal-to-hydrogen purification gas and methanol relaxation gas is relatively high, ranging from 5.0 to 7.0 MPaG, while the pressure of gases such as reforming gas and low-fraction gas is 2.0 to 2.7 MPaG. There are also some industrial tail gases with a pressure of only 0.6 MPaG or atmospheric pressure. For some large enterprises, there are multiple types of raw gas, high pressure and low pressure, and the required product hydrogen pressure is generally only one specification. At this time, the conventional practice is to compress the low-pressure raw gas to the pressure of the high-pressure raw gas, and the high- and low-pressure raw gases with equivalent hydrogen content enter a set of pressure swing adsorption devices to purify the hydrogen and obtain hydrogen of one pressure specification; when the hydrogen content of the low-pressure raw gas is significantly different from that of the high-pressure raw gas, the high-pressure raw gas and the low-pressure raw gas enter the high-pressure pressure swing adsorption device and the low-pressure adsorption device respectively, and the product hydrogen of the low-pressure pressure swing adsorption device is compressed by a compressor to the product hydrogen pressure of the high-pressure pressure swing adsorption device, such as Figure 5 As shown in the figure, high-pressure feed gas and low-pressure feed gas coexist, and it is a common configuration to build high-pressure and low-pressure pressure swing adsorption hydrogen production units at the same time. The low-pressure hydrogen separated by the low-pressure pressure swing adsorption hydrogen extraction unit needs to be compressed before it can be mixed with the high-pressure hydrogen separated by the high-pressure pressure swing adsorption hydrogen extraction unit for transportation. The hydrogen compressor supporting the low-pressure pressure swing adsorption hydrogen extraction unit not only increases equipment investment but also has high operating energy consumption.

[0004] Therefore, designing a high-low pressure coupled pressure swing adsorption hydrogen extraction system and method to reduce the equipment investment cost and device operating cost of separating hydrogen from high- and low-pressure raw gases with different hydrogen contents has become a technical problem that needs to be urgently solved by technicians in the relevant technical field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a high-low pressure coupled pressure swing adsorption hydrogen extraction system and method, which utilizes the power of the pressure-equalizing and pressure-reducing gas during the circulation process of the high-pressure pressure swing adsorption hydrogen extraction device to increase the pressure of the low-pressure product hydrogen of the low-pressure pressure swing adsorption hydrogen extraction device to the pressure of the high-pressure product hydrogen of the high-pressure pressure swing adsorption device. The product hydrogen of the low-pressure pressure swing adsorption and high-pressure pressure swing adsorption devices are both output from the high-pressure pressure swing adsorption device, thereby eliminating the separate compression process of the low-pressure product hydrogen of the low-pressure pressure swing adsorption device. In this way, the compressor of this step can be eliminated, which not only reduces the investment in compressor equipment, but also saves the energy consumption cost of the compressor operation.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A high-low pressure coupled pressure swing adsorption hydrogen extraction system comprises a high-pressure pressure swing adsorption hydrogen extraction device and a low-pressure pressure swing adsorption hydrogen extraction device. The low-pressure product hydrogen transmission pipe on the low-pressure pressure swing adsorption hydrogen extraction device is respectively connected to each high-pressure adsorption tower in the high-pressure pressure swing adsorption hydrogen extraction device for delivering the low-pressure product hydrogen separated and purified by the low-pressure pressure swing adsorption hydrogen extraction device into the corresponding high-pressure adsorption tower when the high-pressure adsorption tower undergoes a hydrogen storage step.

[0008] Furthermore, a regulating valve is provided on the low-pressure product hydrogen export pipe, and a program-controlled valve is provided on the pipeline connecting the low-pressure product hydrogen export pipe and each high-pressure adsorption tower.

[0009] A separation and purification method for a high-low pressure coupled pressure swing adsorption hydrogen extraction system is completed by the cooperation of a high-pressure pressure swing adsorption hydrogen extraction device and a low-pressure pressure swing adsorption hydrogen extraction device. Each high-pressure adsorption tower of the high-pressure pressure swing adsorption hydrogen extraction device undergoes an adsorption step, a pressure reduction step, a regeneration step, a pressure equalization and boosting step, a hydrogen storage step and a final pressure boosting step. The low-pressure product hydrogen separated and purified by the low-pressure pressure swing adsorption hydrogen extraction device enters the high-pressure adsorption tower for temporary storage when the adsorption tower of the high-pressure pressure swing adsorption hydrogen extraction device undergoes the hydrogen storage step. After the high-pressure adsorption tower undergoes the pressure equalization and boosting step and the final pressure boosting step, the low-pressure product hydrogen temporarily stored therein reaches the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device. After the high-pressure adsorption tower enters the adsorption step, the hydrogen in the high-pressure adsorption tower is output as high-pressure product hydrogen.

[0010] Preferably, the operating pressure of the high-pressure pressure swing adsorption hydrogen extraction device is higher than the operating pressure of the low-pressure pressure swing adsorption hydrogen extraction device.

[0011] Preferably, the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device is 2.0MPaG~7.0MPaG, and the adsorption pressure of the low-pressure pressure swing adsorption hydrogen extraction device is 0.5MPaG~6.0MPaG, and the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device is higher than the adsorption pressure of the low-pressure pressure swing adsorption hydrogen extraction device.

[0012] Preferably, the desorbed gas from the high-pressure pressure swing adsorption hydrogen extraction device is pressurized and used as part or all of the feed gas for the low-pressure pressure swing adsorption hydrogen extraction device.

[0013] Preferably, the hydrogen production capacity of the high-pressure pressure swing adsorption hydrogen extraction device is greater than that of the low-pressure pressure swing adsorption hydrogen extraction device.

[0014] Preferably, the purity of the high-pressure product hydrogen of the high-pressure pressure swing adsorption hydrogen extraction device is not lower than the purity of the low-pressure product hydrogen of the low-pressure pressure swing adsorption hydrogen extraction device.

[0015] Preferably, the hydrogen storage step of the high-pressure pressure swing adsorption hydrogen extraction device is carried out separately or simultaneously with the pressure equalization and pressure boosting step.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention has a simple structure and a scientific and reasonable design. Through the coupling operation of high and low pressure pressure swing adsorption hydrogen extraction devices, the low-pressure product hydrogen output pipe of the low-pressure pressure swing adsorption hydrogen extraction device is respectively connected to each high-pressure adsorption tower of the high-pressure pressure swing adsorption hydrogen extraction device. At the same time, the high-pressure pressure swing adsorption hydrogen extraction device adds a hydrogen storage step, and the low-pressure product hydrogen of the low-pressure pressure swing adsorption hydrogen extraction device is transported to the corresponding high-pressure adsorption tower for temporary storage during the hydrogen storage step. After the high-pressure adsorption tower undergoes the equalization and pressure boosting step and the final pressure boosting step, the low-pressure product hydrogen temporarily stored therein is pressurized to the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device, and after the high-pressure adsorption tower enters the adsorption step, it is exported together as high-pressure product hydrogen. In this way, the separate pressurization process of the low-pressure product hydrogen can be effectively omitted, thereby effectively reducing the use of compressor equipment, reducing compressor equipment investment, and at the same time reducing the energy consumption cost of compressor equipment and reducing carbon dioxide emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the coupling of the high- and low-pressure pressure swing adsorption hydrogen extraction device of the present invention.

[0019] Figure 2 This is the timing chart of PSA1 in Example 1 of the present invention.

[0020] Figure 3 This is the timing chart of PSA2 in Example 2 of the present invention.

[0021] Figure 4 Schematic diagram of a high-pressure pressure swing adsorption hydrogen production device in an embodiment of the present invention.

[0022] Figure 5 Schematic diagram of the conventional process of two sets of pressure swing adsorption hydrogen production units with different traditional pressures. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, the present invention provides a high-low pressure coupled pressure swing adsorption hydrogen extraction system, comprising a high-pressure pressure swing adsorption hydrogen extraction unit and a low-pressure pressure swing adsorption hydrogen extraction unit. The low-pressure product hydrogen transmission pipe of the low-pressure pressure swing adsorption hydrogen extraction unit is respectively connected to each high-pressure adsorption tower in the high-pressure pressure swing adsorption hydrogen extraction unit, so as to deliver the low-pressure product hydrogen separated and purified by the low-pressure pressure swing adsorption hydrogen extraction unit to the corresponding high-pressure adsorption tower when the high-pressure adsorption tower undergoes the hydrogen storage step. The low-pressure product hydrogen transmission pipe is provided with a regulating valve, and the pipeline connecting the low-pressure product hydrogen transmission pipe to each high-pressure adsorption tower is also equipped with a programmable valve.

[0025] The low-pressure hydrogen product from the low-pressure PSA hydrogen extraction unit enters the high-pressure adsorption tower of the high-pressure PSA hydrogen extraction unit during the hydrogen storage step. After undergoing the equalization and final pressure-boosting steps, the low-pressure hydrogen stored in the high-pressure adsorption tower reaches the adsorption pressure of the high-pressure PSA hydrogen extraction unit and is ultimately converted into hydrogen at the same pressure as the high-pressure product hydrogen from the high-pressure PSA unit. This high-low pressure coupling process increases the pressure of the low-pressure hydrogen product from the low-pressure PSA hydrogen extraction unit, eliminating the need for a compressor, saving operating energy, and reducing carbon dioxide emissions.

[0026] like Figure 1 As shown, the present invention provides a separation and purification method for a high-low pressure coupled pressure swing adsorption hydrogen extraction system, which is completed by the cooperation of a high-pressure pressure swing adsorption hydrogen extraction device and a low-pressure pressure swing adsorption hydrogen extraction device. Each high-pressure adsorption tower of the high-pressure pressure swing adsorption hydrogen extraction device undergoes an adsorption step, a pressure reduction step, a regeneration step, a pressure equalization step, a hydrogen storage step, and a final pressure increase step. The low-pressure product hydrogen separated and purified by the low-pressure pressure swing adsorption hydrogen extraction device enters the high-pressure adsorption tower for temporary storage while the high-pressure adsorption tower undergoes the hydrogen storage step. After the high-pressure adsorption tower undergoes the pressure equalization step and the final pressure increase step, the low-pressure product hydrogen temporarily stored therein reaches the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device. After it enters the adsorption step, the hydrogen in the high-pressure adsorption tower is output as high-pressure product hydrogen. The operating pressure of the high-pressure pressure swing adsorption hydrogen extraction device is higher than that of the low-pressure pressure swing adsorption hydrogen extraction device. The hydrogen storage step of the high-pressure pressure swing adsorption hydrogen extraction device is performed separately or simultaneously with the pressure equalization step.

[0027] Preferably, the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device is 2.0MPaG~7.0MPaG, and the adsorption pressure of the low-pressure pressure swing adsorption hydrogen extraction device is 0.5MPaG~6.0MPaG, and the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device is higher than the adsorption pressure of the low-pressure pressure swing adsorption hydrogen extraction device.

[0028] Preferably, the desorbed gas from the high-pressure PSA hydrogen extraction unit is pressurized and used as part or all of the feed gas for the low-pressure PSA hydrogen extraction unit. The hydrogen production capacity of the high-pressure PSA hydrogen extraction unit is greater than that of the low-pressure PSA hydrogen extraction unit. The purity of the high-pressure hydrogen product from the high-pressure PSA hydrogen extraction unit is no less than the purity of the low-pressure hydrogen product from the low-pressure PSA hydrogen extraction unit.

[0029] The present invention has a simple structure and a scientific and reasonable design. Through the coupling operation of high and low pressure pressure swing adsorption hydrogen extraction devices, the low-pressure product hydrogen output pipe of the low-pressure pressure swing adsorption hydrogen extraction device is respectively connected to each high-pressure adsorption tower of the high-pressure pressure swing adsorption hydrogen extraction device. At the same time, the high-pressure pressure swing adsorption hydrogen extraction device adds a hydrogen storage step, and the low-pressure product hydrogen of the low-pressure pressure swing adsorption hydrogen extraction device is transported to the corresponding high-pressure adsorption tower for temporary storage during the hydrogen storage step. After the high-pressure adsorption tower undergoes the equalization and pressure boosting step and the final pressure boosting step, the low-pressure product hydrogen temporarily stored therein is pressurized to the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device, and after the high-pressure adsorption tower enters the adsorption step, it is exported together as high-pressure product hydrogen. In this way, the separate pressurization process of the low-pressure product hydrogen can be effectively omitted, thereby effectively reducing the use of compressor equipment, reducing compressor equipment investment, and at the same time reducing the energy consumption cost of compressor equipment and reducing carbon dioxide emissions.

[0030] The present invention is described in more detail below using two examples, where the concentration percentages used in the examples are molar percentages.

[0031] Example 1

[0032] like Figure 4 As shown, a high-low pressure coupled pressure swing adsorption hydrogen extraction system includes a high-pressure pressure swing adsorption hydrogen extraction unit PSA1 and a low-pressure pressure swing adsorption hydrogen extraction unit PSA2. The adsorption pressure of PSA1 is 5.8 MPaG, and the feed gas composition is: H2 / N2 / CO / CH4 / CO2 = 74.8% / 11.2% / 4.2% / 3.2% / 6.6%. The hydrogen output of PSA1 is 50,000 Nm 3 / h, hydrogen pressure is 5.75MPaG, using 16-2-9 / P pressure swing adsorption process. PSA2 adsorption pressure is 3.1MPaG, raw gas composition is: H2 / CO / CH4=95% / 0.01% / 4.99%, PSA2 hydrogen production is 14000Nm 3 / h, the hydrogen pressure is 3.05MPaG, and the 8-1-5 / P pressure swing adsorption process is adopted.

[0033] PSA2 is a conventional process, and PSA1 is a process with a hydrogen storage step. The timing of PSA1 is as follows: Figure 2 As shown in Table 1, Figure 2 In the figure, A: adsorption step, 1D: the first equalizing pressure reducing step, 2D: the second equalizing pressure reducing step, 3D: the third equalizing pressure reducing step, 4D: the fourth equalizing pressure reducing step, 5D: the fifth equalizing pressure reducing step, 6D: the sixth equalizing pressure reducing step, 6D: the seventh equalizing pressure reducing step, 8D: the eighth equalizing pressure reducing step, 9D: the ninth equalizing pressure reducing step, PP: forward placement step, D: reverse placement step, P: flushing step, 9R: the ninth equalizing pressure increasing step, 8R: the eighth equalizing pressure increasing step, 7R: the seventh equalizing pressure increasing step, 6R: the sixth equalizing pressure increasing step, C: hydrogen storage step, 5R: the fifth equalizing pressure increasing step, 4R: the fourth equalizing pressure increasing step, 3R: the third equalizing pressure increasing step, 2R: the second equalizing pressure increasing step, 1R: the first equalizing pressure increasing step, FR: the final pressure increasing step.

[0034] PSA1 adopts a 16-2-9 / P pressure swing adsorption process with a total of 16 adsorption towers. Two adsorption towers are fed for adsorption at the same time, and there are 9 pressure equalization steps. Each adsorption tower undergoes 32 steps in one cycle, including 4 adsorption steps, 9 pressure equalization reduction steps and 9 pressure equalization increase steps, 2 inversion steps, 4 flushing steps, 2 hydrogen storage steps and 1 final pressure increase step. The hydrogen storage step is located between the 6-equal pressurization step and the 5-equal pressurization step. In the hydrogen storage step, the product hydrogen of PSA2 enters the adsorption tower of PSA1 through the hydrogen storage pipeline and the corresponding valve. The product gas of PSA2 is stored in the adsorption tower of PSA1. The stored hydrogen undergoes 5-equal pressurization steps, 4-equal pressurization steps, 3-equal pressurization steps, 2-equal pressurization steps, 1-equal pressurization step and the final pressurization step, and the pressure is raised to the product gas pressure of PSA1 of 5.75MPaG. After entering the adsorption step, this part of the stored hydrogen is used together with the hydrogen of PSA1 as the product hydrogen at 5.75MPaG output device.

[0035] By coupling the two pressure swing adsorption hydrogen extraction units PSA1 and PSA2, the low-pressure product hydrogen of PSA2 is converted into product gas with the same pressure as the high-pressure product hydrogen of PSA1, saving investment in compressors and reducing the energy consumption of PSA2 hydrogen compression by 370kW, saving 3.108 million kWh of electricity per year (based on 8,400 hours of annual operation).

[0036] Example 2

[0037] like Figure 4As shown, a high-low pressure coupled pressure swing adsorption hydrogen extraction system includes a high-pressure pressure swing adsorption hydrogen extraction unit PSA1 and a low-pressure pressure swing adsorption hydrogen extraction unit PSA2. The adsorption pressure of PSA1 is 5.6 MPaG, and the feed gas composition is: H2 / N2 / CO / CH4=97.1% / 0.78% / 1.69% / 0.43%. The hydrogen output of PSA1 is 200,000 Nm 3 / h, hydrogen pressure is 5.55MPaG, using 16-2-9 / P pressure swing adsorption process. PSA2 adsorption pressure is 2.0MPaG, raw gas composition is: H2 / N2 / CO / CH4=63.97% / 9.45% / 21.19% / 5.38%, PSA2 hydrogen output is 10000Nm 3 / h, the hydrogen pressure is 1.95MPaG, and the 6-1-3 / P pressure swing adsorption process is adopted.

[0038] PSA2 is a conventional process, and PSA1 is a process with a hydrogen storage step. The timing of PSA1 is as follows: Figure 3 As shown in Table 2, Figure 3 In the figure, A: adsorption step, 1D: the first equalizing pressure reducing step, 2D: the second equalizing pressure reducing step, 3D: the third equalizing pressure reducing step, 4D: the fourth equalizing pressure reducing step, 5D: the fifth equalizing pressure reducing step, 6D: the sixth equalizing pressure reducing step, 6D: the seventh equalizing pressure reducing step, 8D: the eighth equalizing pressure reducing step, 9D: the ninth equalizing pressure reducing step, PP: forward placement step, D: reverse placement step, P: flushing step, 9R: the ninth equalizing pressure increasing step, 8R: the eighth equalizing pressure increasing step, 7R: the seventh equalizing pressure increasing step, C: hydrogen storage step, 6R: the sixth equalizing pressure increasing step, 5R: the fifth equalizing pressure increasing step, 4R: the fourth equalizing pressure increasing step, 3R: the third equalizing pressure increasing step, 2R: the second equalizing pressure increasing step, 1R: the first equalizing pressure increasing step, FR: the final pressure increasing step.

[0039] PSA1 adopts a 16-2-9 / P pressure swing adsorption process with a total of 16 adsorption towers. Two adsorption towers are fed for adsorption at the same time, and there are 9 pressure equalization steps. Each adsorption tower undergoes 32 steps in one cycle, including 4 adsorption steps, 9 pressure equalization reduction steps and 9 pressure equalization increase steps, 2 inversion steps, 4 flushing steps, 2 hydrogen storage steps and 1 final pressure increase step. The hydrogen storage step is located between the 7-equal pressurization step and the 6-equal pressurization step. In the hydrogen storage step, the product hydrogen of PSA2 enters the adsorption tower of PSA1 through the hydrogen storage pipeline and the corresponding valve. The product gas of PSA2 is stored in the adsorption tower of PSA1. The stored hydrogen undergoes 6-equal pressurization steps, 5-equal pressurization steps, 4-equal pressurization steps, 3-equal pressurization steps, 2-equal pressurization steps, 1-equal pressurization step and the final pressurization step, and the pressure is raised to the product gas pressure of PSA1 of 5.55MPaG. After entering the adsorption step, this part of stored hydrogen is output to the device as product hydrogen at 5.55MPaG together with the hydrogen of PSA1.

[0040] By coupling the two pressure swing adsorption hydrogen extraction units PSA1 and PSA2, the low-pressure product hydrogen of PSA2 is converted into product gas with the same pressure as the high-pressure product hydrogen of PSA1, reducing the hydrogen compression energy consumption of PSA2 by 450kW and saving 3.78 million kWh of electricity annually (based on 8,400 hours of annual operation).

[0041] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are intended to illustrate the technical solutions of the present invention, and are not intended to limit the present invention, nor are they intended to limit the scope of the present invention. In other words, any modifications or improvements that are made to the main design concept and spirit of the present invention without any substantive significance, provided that the technical problems they solve are still consistent with the present invention, shall be included within the scope of protection of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields shall also be included within the scope of protection of the present invention.

Claims

1. A high-low pressure coupled pressure swing adsorption hydrogen extraction system, comprising a high-pressure pressure swing adsorption hydrogen extraction device and a low-pressure pressure swing adsorption hydrogen extraction device, characterized in that: The low-pressure product hydrogen output pipe on the low-pressure pressure swing adsorption hydrogen extraction device is respectively connected to each high-pressure adsorption tower in the high-pressure pressure swing adsorption hydrogen extraction device, and is used to deliver the low-pressure product hydrogen separated and purified by the low-pressure pressure swing adsorption hydrogen extraction device into the corresponding high-pressure adsorption tower when the high-pressure adsorption tower undergoes the hydrogen storage step.

2. A high-low pressure coupled pressure swing adsorption hydrogen extraction system according to claim 1, characterized in that: A regulating valve is provided on the low-pressure product hydrogen external transmission pipe, and a program-controlled valve is provided on the pipeline connecting the low-pressure product hydrogen external transmission pipe and each high-pressure adsorption tower.

3. The separation and purification method of a high-low pressure coupled pressure swing adsorption hydrogen extraction system according to claim 1 or 2, characterized in that: The process is completed by the collaboration of a high-pressure pressure swing adsorption hydrogen extraction device and a low-pressure pressure swing adsorption hydrogen extraction device. Each high-pressure adsorption tower of the high-pressure pressure swing adsorption hydrogen extraction device undergoes an adsorption step, a pressure reduction step, a regeneration step, a pressure equalization and boosting step, a hydrogen storage step and a final pressure boosting step. The low-pressure product hydrogen separated and purified by the low-pressure pressure swing adsorption hydrogen extraction device enters the high-pressure adsorption tower for temporary storage when the high-pressure adsorption tower undergoes the hydrogen storage step. After the high-pressure adsorption tower undergoes the pressure equalization and boosting step and the final pressure boosting step following the hydrogen storage step, the low-pressure product hydrogen temporarily stored therein reaches the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device. After it enters the adsorption step, the hydrogen in the high-pressure adsorption tower is output as high-pressure product hydrogen.

4. The separation and purification method according to claim 3, wherein The operating pressure of the high-pressure pressure swing adsorption hydrogen extraction device is higher than the operating pressure of the low-pressure pressure swing adsorption hydrogen extraction device.

5. The separation and purification method according to claim 3, wherein The adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device is 2.0MPaG~7.0MPaG, and the adsorption pressure of the low-pressure pressure swing adsorption hydrogen extraction device is 0.5MPaG~6.0MPaG, and the adsorption pressure of the high-pressure pressure swing adsorption hydrogen extraction device is higher than that of the low-pressure pressure swing adsorption hydrogen extraction device.

6. The separation and purification method according to claim 3, wherein The desorbed gas from the high-pressure pressure swing adsorption hydrogen extraction device is pressurized and used as part or all of the feed gas for the low-pressure pressure swing adsorption hydrogen extraction device.

7. The separation and purification method according to claim 3, wherein The hydrogen production capacity of the high-pressure pressure swing adsorption hydrogen extraction device is greater than that of the low-pressure pressure swing adsorption hydrogen extraction device.

8. The separation and purification method according to claim 3, wherein The purity of the high-pressure product hydrogen of the high-pressure pressure swing adsorption hydrogen extraction device shall not be lower than the purity of the low-pressure product hydrogen of the low-pressure pressure swing adsorption hydrogen extraction device.

9. The separation and purification method according to claim 3, wherein The hydrogen storage step of the high-pressure pressure swing adsorption hydrogen extraction device is carried out independently or simultaneously with the pressure equalization and pressure boosting step.

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