Improved process for purifying hydrogen through pressure swing adsorption

Abstract

The invention discloses an improved process for purifying hydrogen through pressure swing adsorption, and belongs to the technical field of gas separation. According to the process, N adsorption towers and M clockwise-deflation buffer tanks are adopted, the adsorption towers and the clockwise-deflation buffer tanks are in coupled operation to continuously produce hydrogen, N is larger than or equal to 4, and M is larger than or equal to 1; each adsorption tower is sequentially subjected to an adsorption step, a pressure equalizing and reducing step, a forward discharging step, a reverse discharging step, a washing step, a pressure equalizing and boosting step and a final charging step in a cycle; wherein the number of times of voltage-sharing boosting is larger than the number of times of voltage-sharing reducing; and in the pressure equalizing and boosting step, at least one time of pressure equalizing and boosting directly utilizes the clockwise deflation gas in the clockwise deflation gas buffer tank and the adsorption tower to equalize the pressure. According to the invention, the amount of pressurized product gas in the final charging stage can be reduced by 10%-20%, the hydrogen recovery rate can be improved by 0.5%-1.5%, and a new cycle process in which the number of times of pressure equalizing and boosting is greater than that of pressure equalizing and reducing is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation, and particularly relates to an improved pressure swing adsorption process for hydrogen purification. Background Art

[0002] With the global energy structure transforming towards low-carbon, hydrogen, as a clean energy carrier and important industrial raw material, has become increasingly prominent. In fields such as petroleum refining, ammonia synthesis, methanol production, and fuel cells, the demand for high-purity hydrogen (purity ≥ 99.9%) is continuously rising. However, hydrogen in industrial by-products (such as refinery gas, coke oven gas, chlor-alkali tail gas, etc.) usually coexists with various impurities such as CH4, CO, CO2, N2, etc., and needs to be purified through efficient separation technologies. Traditional hydrogen purification methods, such as cryogenic separation and membrane separation, have problems such as high energy consumption, complex equipment, or insufficient product purity. In contrast, the pressure swing adsorption (PSA) technology has gradually become the mainstream process in the hydrogen separation field due to its advantages of flexible operation, low energy consumption, and high product purity.

[0003] The pressure swing adsorption technology is based on the adsorption selectivity differences of adsorbents for different components in the mixed gas, and realizes the adsorption-desorption cycle through periodic pressure changes. Since the UOP company first applied PSA to hydrogen purification in the 1960s, this technology has undergone multiple iterations and optimizations. The typical PSA process uses a configuration of 4 - 16 towers, with adsorbents such as zeolite molecular sieves, activated carbon, and silica gel as the core materials, and realizes continuous hydrogen production through the coordinated operation of multiple towers.

[0004] The pressure swing adsorption (PSA) technology is based on the adsorption selectivity differences of adsorbents for different components in the mixed gas, and realizes the adsorption-desorption cycle through periodic pressure changes. Since the UOP company first applied the PSA technology to hydrogen purification in the 1960s, this technology has undergone multiple iterations and optimizations. The typical PSA process usually configures 4 to 16 adsorption towers, uses zeolite molecular sieves, activated carbon, silica gel, etc. as the core adsorption materials, and realizes continuous and stable hydrogen production through the coordinated operation of multiple towers.

[0005] The adsorption pressure range of the pressure swing adsorption hydrogen extraction device is usually 0.6 MPa to 6.6 MPa. For the process flow using purge regeneration, generally 0.2 to 0.3 MPa of blowdown gas is required as the purge regeneration gas. Since the blowdown step is usually located after the pressure equalization depressurization step, the pressure in the adsorption tower is usually about 0.5 MPa at the end of the pressure equalization depressurization. When the adsorption pressure is 2.5 MPa, generally 4-step pressure equalization is adopted; as the adsorption pressure increases, in order to ensure the hydrogen recovery rate, the number of pressure equalization steps needs to be increased. For example, when the adsorption pressure reaches 3.0 MPa, at least more than 5 steps of pressure equalization are required; if the adsorption pressure is further increased, the number of pressure equalization steps needs to be increased accordingly. However, the existing technology still faces multiple challenges. In the traditional process, increasing the number of pressure equalization steps usually relies on increasing the number of adsorption towers, and each additional adsorption tower can increase one step of pressure equalization. In addition, the patent with the publication number CN111282397A proposes a method of decomposing the pressure equalization step, and an additional N - 1 times of pressure equalization is achieved by adding N intermediate tanks.

[0006] Therefore, providing a pressure swing adsorption hydrogen purification process that can increase the number of pressure equalization steps and thus improve the hydrogen recovery rate without additional equipment has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of the present invention is to provide an improved pressure swing adsorption hydrogen purification process, which starts from the optimization of the process steps to increase the pressure equalization steps and improve the hydrogen recovery rate without additional equipment.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] An improved pressure swing adsorption hydrogen purification process disclosed by the present invention uses N adsorption towers and M blowdown gas buffer tanks, and the adsorption towers and the blowdown gas buffer tanks are coupled to operate continuously to produce hydrogen, where N≥4 and M≥1;

[0010] Each adsorption tower sequentially experiences an adsorption step, a pressure equalization depressurization step, a blowdown step, a reverse blowdown step, a purge step, a pressure equalization pressurization step, and a final charge step within one cycle;

[0011] Among them, the number of pressure equalization pressurization steps in the pressure equalization pressurization step is greater than the number of pressure equalization depressurization steps in the pressure equalization depressurization step; and at least one pressure equalization pressurization in the pressure equalization pressurization step directly uses the blowdown gas in the blowdown gas buffer tank to equalize the pressure with the adsorption tower.

[0012] In some embodiments of the present invention, in the pressure equalization pressurization step, the adsorption tower first equalizes the pressure with the blowdown gas buffer tank, and then sequentially equalizes the pressure with other adsorption towers that have undergone pressure equalization depressurization.

[0013] In some embodiments of the present invention, the number of equalizing pressure reduction steps is X, and the number of equalizing pressure increase steps is X + 1; X ≥ 2 and is an integer.

[0014] The adsorption step, equalizing pressure reduction step, reverse release step, flushing step, and final charging step in the present invention are all prior arts.

[0015] Adsorption step: At any time, one or more adsorption towers are in the adsorption state. The raw material gas enters the adsorption tower in the adsorption state, and product hydrogen is obtained from the outlet of the adsorption tower.

[0016] Equalizing pressure reduction step: After the adsorption step is completed, the adsorption tower performs X (X ≥ 1) equalizing pressure reduction steps.

[0017] Forward release step: After the equalizing pressure reduction step is completed, the adsorption tower continues to reduce pressure in the forward direction, and the forward release gas is discharged into M (M ≥ 1) forward release gas buffer tanks.

[0018] Reverse release step: After the forward release step is completed, the adsorption tower reduces pressure against the adsorption feed direction to reduce the pressure in the adsorption tower to the regeneration pressure.

[0019] Flushing step: The adsorption tower is flushed and regenerated with the gas stored in the forward release gas buffer. During this process, the impurities adsorbed by the adsorbent are carried out of the adsorption tower, and the gas in the forward release gas buffer tank is controlled by a regulating valve.

[0020] Equalizing pressure increase step: After the flushing step is completed, the adsorption tower first performs the (X + 1)-th equalizing pressure with the forward release gas buffer tank, that is, uses a part of the forward release gas to increase the pressure of the adsorption tower, and then performs the conventional X equalizing pressure increase steps until all equalizing pressure increase steps are completed.

[0021] Final charging process: After the equalizing pressure increase step is completed, the adsorption tower is pressurized with the final product hydrogen until the pressure reaches the adsorption pressure.

[0022] In some embodiments of the present invention, the number of forward release gas buffer tanks M ≥ 2, including a high-pressure forward release gas buffer tank and a low-pressure forward release gas buffer tank; the high-pressure forward release gas stored in the high-pressure forward release gas buffer tank accounts for 40% - 70% of the total forward release gas; the low-pressure forward release gas stored in the low-pressure forward release gas buffer tank accounts for 30% - 60% of the total forward release gas. The (X + 1)-th equalizing pressure increase is performed with the high-pressure forward release gas and the adsorption tower, and the flushing step is performed with the low-pressure forward release gas.

[0023] In some embodiments of the present invention, the high-pressure forward release gas comes from the pressure reduction gas after the non-last equalizing pressure reduction.

[0024] In some embodiments of the present invention, the number of high-pressure forward release gas buffer tanks is at least 1.

[0025] In one embodiment of the present invention, the process uses 7 adsorption towers and 1 blowdown gas buffer tank, and has 3 equalization pressure reduction steps and 4 equalization pressure increase steps;

[0026] The adsorption tower first performs the 4th equalization pressure increase with the blowdown gas buffer tank, and then sequentially performs 3 equalization pressure increase steps with other adsorption towers that are undergoing equalization pressure reduction.

[0027] In another embodiment of the present invention, the process uses 12 adsorption towers and 2 blowdown gas buffer tanks, and has 6 equalization pressure reduction steps and 7 equalization pressure increase steps; the adsorption tower first performs the 7th equalization pressure increase with the blowdown gas buffer tank, and then sequentially performs 6 equalization pressure increase steps with other adsorption towers that are undergoing equalization pressure reduction.

[0028] Preferably, one of the 2 blowdown gas buffer tanks is a high-pressure blowdown gas buffer tank, and the other is a low-pressure blowdown gas buffer tank; the high-pressure blowdown gas is used to perform the 7th equalization pressure increase with the adsorption tower, and the low-pressure blowdown gas is used to flush the adsorption tower.

[0029] Preferably, the high-pressure blowdown gas accounts for 55% of the total blowdown gas, and the low-pressure blowdown gas accounts for 45% of the total blowdown gas.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention stores the blowdown gas in a stepped pressure manner by setting M buffer tanks, converts the blowdown gas in the high-pressure buffer tank into equalization gas through the (X + 1)th equalization pressure increase step, and recovers this part of the blowdown gas, which can reduce the gas volume for charging the product gas in the final charging stage by 10% - 20%, improve the hydrogen recovery rate by 0.5% - 1.5%, and realize a new cycle process with the number of equalization pressure increase steps greater than the number of equalization pressure reduction steps. Description of the Drawings

[0032] Figure 1 It is a flowchart of Embodiment 1 of the present invention;

[0033] Figure 2 It is a flowchart of Embodiment 2 of the present invention.

[0034] Among them, the names corresponding to the reference numerals are:

[0035] T1 - T12: Adsorption towers;

[0036] 1 - Feed gas pipeline, 2 - Flush out waste gas pipeline, 3 - Blowdown gas pipeline, 4 - Flush in pipeline, 5 - 4th equalization / blowdown pipeline, 6 - 2nd equalization / 3rd equalization pipeline, 7 - 1st equalization / final charging pipeline, 8 - Product gas pipeline, 9 - Product gas pipeline, 5A - 6th equalization / 7th equalization / blowdown pipeline, 6A - 4th equalization / 5th equalization pipeline, 7A - 2nd equalization / 3rd equalization pipeline, 8A - 1st equalization and final charging pipeline;

[0037] G - Forward vent buffer tank, G1 - High - pressure forward vent buffer tank, G2 - Low - pressure forward vent buffer tank;

[0038] PV / PV1 - Flushing regulating valve, HV / HV1 - Final charging regulating valve, 50 - Total forward vent valve, 50A - First total forward vent valve, 50B - Second total forward vent valve;

[0039] 1N - First program - controlled valve, 2N - Second program - controlled valve, 3N - Third program - controlled valve, 4N - Fourth program - controlled valve, 5N - Fifth program - controlled valve, 6N - Sixth program - controlled valve, 7N - Seventh program - controlled valve, 8N - Eighth program - controlled valve, 9N - Ninth program - controlled valve 9N; where N in 1N, 2N, 3N, 4N, 5N, 6N, 7N, 8N, 9N is the number of the adsorption tower. Correspondingly, 1N, 2N, 3N, 4N, 5N, 6N, 7N, 8N, 9N are the numbers of the program - controlled valves. For example Figure 2 in the case of the adsorption tower numbered T3, the corresponding 1N, 2N, 3N, 4N, 5N, 6N, 7N, 8N, 9N are 13, 23, 33, 43, 53, 63, 73, 83, 93 respectively; for the adsorption tower numbered T12, the corresponding 1N, 2N, 3N, 4N, 5N, 6N, 7N, 8N, 9N are 112, 212, 312, 412, 512, 612, 712, 812, 912 respectively, and so on for others. Detailed implementation manners

[0040] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0041] The following will give a detailed description of the present invention through specific examples, but this should not be construed as limiting the above - mentioned subject matter of the present invention.

[0042] Embodiment 1

[0043] As Figure 1 shown, this embodiment discloses an improved pressure swing adsorption process for hydrogen purification. The process of this embodiment uses 7 adsorption towers (T1 - T7) and 1 forward vent buffer tank (G).

[0044] As attached Figure 1As shown in the figure, the pressure swing adsorption hydrogen purification system of this embodiment includes seven adsorption towers T1 - T7, a raw material gas pipeline 1 connected to the adsorption towers T1 - T7 and provided with a first programmable control valve 1N, a flushing waste gas pipeline 2 provided with a second programmable control valve 2N, a reverse exhaust pipeline 3 provided with a third programmable control valve 3N, a flushing inlet pipeline 4 led out from the adsorption towers T1 - T7 and provided with a fourth programmable control valve 4N, a fourth equalization / forward release pipeline 5 provided with a fifth programmable control valve 5N, a second equalization / third equalization pipeline 6 provided with a sixth programmable control valve 6N, a first equalization / end - charge pipeline 7 provided with a seventh programmable control valve 7N, and a product gas pipeline 8 provided with an eighth programmable control valve 8N. The fourth equalization / forward release pipeline 5 is connected to the forward release gas buffer tank G, the flushing inlet pipeline 4 is led out from the forward release gas buffer tank G, a forward release main valve 50 is arranged on the fourth equalization / forward release pipeline 5, and a flushing regulating valve PV1 is arranged on the flushing inlet pipeline 4; a final charge regulating valve HV1 is arranged between the product gas pipeline 8 and the first equalization / end - charge pipeline 7.

[0045] The process timing of this embodiment is shown in Table 1, with three equalization pressure drops and four equalization pressure increases. Each adsorption tower sequentially undergoes the following steps:

[0046] Adsorption process: The raw material gas enters the adsorption tower through the raw material gas pipeline 1 via the first programmable control valve 1N. The impurity gas is adsorbed by the adsorbent, and the obtained product hydrogen enters the product gas pipeline 8 through the eighth programmable control valve 8N and is output as product gas.

[0047] Three equalization pressure drop processes: The adsorbed adsorption towers are equalized with three other adsorption towers respectively, and sequentially undergo the first equalization pressure drop, the second equalization pressure drop, and the third equalization pressure drop.

[0048] Forward release process: The adsorption tower after equalization pressure drop discharges the remaining gas in the adsorption tower into the forward release gas buffer tank G through the fifth programmable control valve 5N and the forward release main valve 50.

[0049] Reverse exhaust process: The adsorption tower after forward release undergoes reverse pressure reduction, and the reverse exhaust gas is sent out of the system through the third programmable control valve 3N and the reverse exhaust pipeline 3.

[0050] Flushing process: The adsorption tower after reverse exhaust is flushed and regenerated using the forward release gas in the forward release gas buffer tank G. The forward release gas is regulated by the flushing regulating valve PV1 in the forward release gas buffer tank G, enters the adsorption tower through the fourth programmable control valve 4N, and the flushing waste gas is sent out of the system through the second programmable control valve 2N and the flushing waste gas pipeline 2.

[0051] Four equalization pressure increase processes: The adsorption tower after flushing first undergoes the fourth equalization pressure increase. The adsorption tower and the forward release gas buffer tank G are equalized through the fifth programmable control valve 5N and the forward release main valve 50, and part of the gas in the forward release gas buffer tank G boosts the pressure of the adsorption tower. The adsorption tower after the fourth equalization pressure increase is sequentially equalized with the other three adsorption towers that have undergone equalization pressure drop for the third equalization pressure increase, the second equalization pressure increase, and the first equalization pressure increase.

[0052] Final charging process: The adsorption tower after equalizing pressure and boosting pressure uses the product hydrogen to continue boosting the pressure of the adsorption tower until the pressure inside the adsorption tower reaches the adsorption pressure.

[0053] In this embodiment, the volume composition of the raw material gas is H2: 74.96%, CO: 3.46%, CH4: 4.27%, CO2: 17.05%, H2O: 0.26%; the pressure of the raw material gas is 2.7 MPaG, the purity of the product hydrogen is 99.9%, CO + CO2 ≤ 10 ppmv, and the pressure of the desorbed gas is 0.03 MPaG. Using the process of this embodiment, the hydrogen recovery rate is 89.5%; while for the traditional 7 - tower process with 3 - step equalizing pressure, the hydrogen recovery rate is 88.4%. The hydrogen recovery rate of the process in this embodiment has increased by 1.1%.

[0054] Table 1 7 - tower timing table

[0055]

[0056] In Table 1, the meanings represented by each English letter are: A: Adsorption step, 1D: The first pressure equalizing and reducing step, 2D: The second pressure equalizing and reducing step, 3D: The third pressure equalizing and reducing step, PP: Co - current discharging step, D: Counter - current discharging step, P: Flushing step, 4R: The fourth pressure equalizing and boosting step, 3R: The third pressure equalizing and boosting step, 2R: The second pressure equalizing and boosting step, 1R: The first pressure equalizing and boosting step, IS: Isolation step, FR: Final charging step.

[0057] Example 2

[0058] As Figure 2 shown, this embodiment discloses an improved pressure swing adsorption process for purifying hydrogen. The process of this embodiment uses 12 adsorption towers (T1 - T12) and 2 co - current discharging gas buffer tanks (G1, G2), where G1 is a high - pressure co - current discharging gas buffer tank and G2 is a low - pressure co - current discharging gas buffer tank.

[0059] As attached Figure 2As shown in the figure, the pressure swing adsorption hydrogen purification system of this embodiment includes at least 12 adsorption towers (T1 - T12), a raw material gas pipeline 1 connected to the adsorption tower and provided with a first programmable control valve 1N, a flushing waste gas pipeline 2 provided with a second programmable control valve 2N, a reverse discharge gas pipeline 3 provided with a third programmable control valve 3N, as well as a flushing inlet pipeline 4 connected from the adsorption tower and provided with a fourth programmable control valve 4N, a 6th equal pressure / 7th equal pressure / forward discharge pipeline 5A provided with a fifth programmable control valve 5N, a 2nd equal pressure / 3rd equal pressure pipeline 7A provided with a seventh programmable control valve 7N, a 4th equal pressure / 5th equal pressure pipeline 6A provided with a sixth programmable control valve 6N, a 1st equal pressure and final charging pipeline 8A provided with an eighth programmable control valve 8N, and a product gas pipeline 9 provided with a ninth programmable control valve 9N. The 6th equal pressure / 7th equal pressure / forward discharge pipeline 5A is connected to a high-pressure forward discharge gas buffer tank G1 and a low-pressure forward discharge gas buffer tank G2, and the flushing inlet pipeline 4 is led out from the low-pressure forward discharge gas buffer tank G2. A first forward discharge main valve 50A is arranged on the pipeline connecting the high-pressure forward discharge gas buffer tank G1 and the 6th equal pressure / 7th equal pressure / forward discharge pipeline 5A, and a second forward discharge main valve 50B is arranged on the pipeline connecting the low-pressure forward discharge gas buffer tank G2 and the 6th equal pressure / 7th equal pressure / forward discharge pipeline 5A. A flushing regulating valve PV is arranged on the flushing inlet pipeline 4, and a final charging regulating valve HV is arranged between the product gas pipeline 9 and the 1st equal pressure and final charging pipeline 8A.

[0060] The process timing of this embodiment is shown in Table 2, with 6 equal pressure step-downs and 7 equal pressure step-ups. Each adsorption tower sequentially experiences the following steps:

[0061] Adsorption process: The raw material gas enters the adsorption tower through the raw material gas pipeline 1 via the first programmable control valve 1N. The impurity gas is adsorbed by the adsorbent, and the obtained high-purity hydrogen enters the product gas pipeline 9 through the ninth programmable control valve 9N and is output as product gas. At any moment, 2 adsorption towers are in the adsorption process.

[0062] 6 equal pressure step-down processes: The adsorbed adsorption towers are equalized with another 6 adsorption towers respectively, and sequentially experience the 1st equal pressure step-down, the 2nd equal pressure step-down, the 3rd equal pressure step-down, the 4th equal pressure step-down, the 5th equal pressure step-down, and the 6th equal pressure step-down.

[0063] Forward discharge process: The forward discharge process and the 6th equal pressure step-down process use the same row of programmable control valves. The 6th equal pressure step-down process and the forward discharge process are completed in the same time sequence, that is, after the 6th equal pressure step-down ends, the valves for the 6th equal pressure step-up are closed, and at the same time, the first forward discharge main valve 50A is opened, and the high-pressure forward discharge gas is put into the high-pressure forward discharge gas buffer tank G1. Then the forward discharge main valve 50A is closed, and the forward discharge main valve 50B is opened to put the low-pressure forward discharge gas into the low-pressure forward discharge gas buffer tank G2, where the high-pressure forward discharge gas accounts for 55% of the forward discharge gas volume, and the low-pressure forward discharge gas accounts for 45% of the forward discharge gas volume.

[0064] Reverse discharge process: The adsorbed adsorption tower after forward discharge undergoes reverse pressure reduction, and the reverse discharge gas is sent out of the system through the third programmable control valve 3N and the reverse discharge gas pipeline 3.

[0065] Rinsing process: After reverse discharging, the adsorption tower is rinsed and regenerated using the low-pressure blowdown gas in the low-pressure blowdown gas buffer tank G2. The low-pressure blowdown gas is regulated by the rinsing regulating valve PV from the low-pressure blowdown gas buffer tank G2 and enters the adsorption tower through the fourth program control valve 4N. The rinsing waste gas is sent out of the system through the program control valve 2N and the rinsing waste gas pipeline 2.

[0066] 7th equalization pressure boosting process: After rinsing, the adsorption tower first undergoes the 7th equalization pressure boost. The adsorption tower and the high-pressure blowdown gas buffer tank G2 equalize pressure through the fifth program control valve 5N and the first blowdown main valve 50A. The blowdown gas in the high-pressure blowdown gas buffer tank G1 boosts the pressure of the adsorption tower. After the 7th equalization pressure boost, the adsorption tower and the other 6 adsorption towers undergoing equalization pressure reduction sequentially perform the 6th equalization pressure boost, the 5th equalization pressure boost, the 4th equalization pressure boost, the 3rd equalization pressure boost, the 2nd equalization pressure boost, and the 1st equalization pressure boost;

[0067] Final charging process: After equalization pressure boosting, the adsorption tower continues to be pressurized using the product hydrogen until the pressure in the adsorption tower reaches the adsorption pressure.

[0068] The volume composition of the raw material gas in this embodiment is: H2: 97.1%, N2: 0.41%, Ar: 0.14%, CO: 2.11%, CH4: 0.24%; the pressure of the raw material gas is 4.5 MPaG, the purity of the product hydrogen is 99.9%, CO ≤ 10 ppmv, and the pressure of the desorbed gas is 0.03 MPaG. Using the process of this embodiment, the hydrogen recovery rate is 92.5%; while for the traditional 12-tower process with 6-step equalization, the hydrogen recovery rate is 91.0%. The hydrogen recovery rate of the process in this embodiment has increased by 1.5%.

[0069] Table 2 12-Tower Timing Table

[0070]

[0071] The meanings represented by each English letter in Table 2 are as follows: A: Adsorption step, 1D: The 1st equalization pressure reduction step, 2D: The 2nd equalization pressure reduction step, 3D: The 3rd equalization pressure reduction step, 4D: The 4th equalization pressure reduction step, 5D: The 5th equalization pressure reduction step, 6DP: The 6th equalization pressure reduction step and blowdown step, D: Reverse discharge step, P: Rinsing step, 7R: The 7th equalization pressure boosting step, 6R: The 6th equalization pressure boosting step, 5R: The 5th equalization pressure boosting step, 4R: The 4th equalization pressure boosting step, 3R: The 3rd equalization pressure boosting step, 2R: The 2nd equalization pressure boosting step, 1R: The 1st equalization pressure boosting step, FR: Final charging step.

[0072] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting it. Certainly, it does not limit the patent scope of the present invention. Any meaningless changes or polishing made on the main design concept and spirit of the present invention, as long as the technical problems solved are still the same as those of the present invention, should be included in the protection scope of the present invention; in addition, directly or indirectly applying the technical solutions of the present invention to other related technical fields shall also be included in the patent protection scope of the present invention by the same token.

Claims

1. An improved pressure swing adsorption process for purifying hydrogen, characterized in that, The process uses N adsorption towers and M blowdown gas buffer tanks, and the adsorption towers and blowdown gas buffer tanks operate in a coupled manner to continuously produce hydrogen, where N≥4 and M≥1; Each adsorption tower sequentially experiences an adsorption step, an equalization pressure reduction step, a co-current blowdown step, a counter-current blowdown step, a purge step, an equalization pressure increase step, and a final charge step within one cycle; Among them, the number of equalization pressure increase times in the equalization pressure increase step is greater than the number of equalization pressure reduction times in the equalization pressure reduction step; and at least one equalization pressure increase in the equalization pressure increase step directly uses the blowdown gas in the blowdown gas buffer tank for equalization with the adsorption tower.

2. An improved pressure swing adsorption process for purifying hydrogen according to claim 1, characterized in that, In the equalization pressure increase step, the adsorption tower first performs equalization pressure increase with the blowdown gas buffer tank, and then sequentially performs equalization pressure increase with other adsorption towers that have undergone equalization pressure reduction.

3. An improved pressure swing adsorption process for purifying hydrogen according to claim 1, characterized in that, The number of equalization pressure reduction times is X, and the number of equalization pressure increase times is X + 1; X≥2 and is an integer.

4. An improved pressure swing adsorption process for hydrogen purification according to any one of claims 1-3, characterized in that, The number of blowdown gas buffer tanks M≥2, including a high-pressure blowdown gas buffer tank and a low-pressure blowdown gas buffer tank; the high-pressure blowdown gas stored in the high-pressure blowdown gas buffer tank accounts for 40% - 70% of the total blowdown gas; the low-pressure blowdown gas stored in the low-pressure blowdown gas buffer tank accounts for 30% - 60% of the total blowdown gas. The high-pressure blowdown gas is used for the (X + 1)th equalization pressure increase with the adsorption tower, and the low-pressure blowdown gas is used for the purge step.

5. An improved pressure swing adsorption process for purifying hydrogen according to claim 4, characterized in that, The high-pressure blowdown gas comes from the blowdown gas after non-the last equalization pressure reduction.

6. An improved pressure swing adsorption process for purifying hydrogen according to claim 4, characterized in that, The number of high-pressure blowdown gas buffer tanks is at least 1.

7. An improved pressure swing adsorption process for purifying hydrogen according to claim 1, characterized in that, The system includes 7 adsorption towers and 1 blowdown gas buffer tank, and has 3 equalization pressure reduction steps and 4 equalization pressure increase steps; The adsorption tower first performs the 4th equalization pressure increase with the blowdown gas buffer tank, and then sequentially performs 3 equalization pressure increases with other adsorption towers that have undergone equalization pressure reduction.

8. An improved pressure swing adsorption process for purifying hydrogen according to claim 1, characterized in that, The system includes 12 adsorption towers and 2 blowdown gas buffer tanks, and has 6 equalization pressure reduction steps and 7 equalization pressure increase steps; the adsorption tower first performs the 7th equalization pressure increase with the blowdown gas buffer tank, and then sequentially performs 6 equalization pressure increases with other adsorption towers that have undergone equalization pressure reduction.

9. An improved pressure swing adsorption process for purifying hydrogen according to claim 8, characterized in that, One of the 2 blowdown gas buffer tanks is a high-pressure blowdown gas buffer tank, and the other is a low-pressure blowdown gas buffer tank; the high-pressure blowdown gas is used for the (X + 1)th equalization pressure increase with the adsorption tower, and the low-pressure blowdown gas is used to purge the adsorption tower.

10. An improved pressure swing adsorption process for purifying hydrogen according to claim 8, characterized in that, The high-pressure blowdown gas accounts for 55% of the total blowdown gas, and the low-pressure blowdown gas accounts for 45% of the total blowdown gas.

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