Process and device for deep purification and flexible selection of hydrogen in low-temperature environment

Abstract

The invention discloses a process and a device for deep purification and flexible selection of hydrogen in a low-temperature environment, the device comprises a feed gas heat exchanger (1), a liquid nitrogen tank (2), a main path gas pipe (3), a plurality of first branch gas pipes (6), a plurality of second branch gas pipes (7), a hydrogen storage tank (8), a vacuum pump (9) and a plurality of valves (10), and the liquid nitrogen tank comprises a cryogenic buffer tank (4) and a plurality of adsorption towers (5); the two sides of the raw material gas heat exchanger are respectively communicated with the main path gas pipe (3), one end of the raw material gas heat exchanger is respectively communicated with the cryogenic buffer tank (4), the plurality of adsorption towers (5) and the vacuum pump (9), and the other ends of the cryogenic buffer tank (4) and the plurality of adsorption towers (5) are respectively communicated with the main path gas pipe (3) through the first branch gas pipe (6). The preparation and purification efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen purification, and particularly relates to a flexible selection process and device for deep impurity removal of hydrogen in a low-temperature environment. Background Technique

[0002] The hydrogen impurity removal technology refers to using various methods to remove impurity components in the hydrogen production raw material gas, and finally obtaining high-purity hydrogen that meets the industrial production application standards. The impurity removal process is a key step in the effective utilization of hydrogen energy. The hydrogen after impurity removal is widely used in high-tech industries such as metallurgy, biomedicine, fuel cells, and aerospace. In the technical requirements of China's GB / T3634.1-2006 "Hydrogen - Part 1: Industrial Hydrogen", the purity standard of high-purity hydrogen is 99.999%. Currently, the hydrogen used in fuel cells at home and abroad is generally based on this standard. In the production process of polysilicon in the semiconductor industry, the purity of hydrogen is required to reach more than 99.9999%. Therefore, the deep impurity removal of hydrogen has become an urgent problem to be solved.

[0003] The industrial hydrogen purity standard in the industry is used to measure the quality of hydrogen used in fuel cells. Even high-purity hydrogen only meets the purity standard, but specific impurities in hydrogen that can damage fuel cells, such as carbon monoxide, carbon dioxide, and methane, may exceed the standard. There is oxygen shuttling between the anode and cathode during the water electrolysis hydrogen production process, resulting in a small amount of oxygen and water vapor impurities in the hydrogen obtained by electrolyzing water. Currently, the highest purity of hydrogen produced by electrolyzing water is about 99.9%. However, many industries have high requirements for hydrogen purity, and the impurity content of hydrogen must be at the ppb level. Through different hydrogen production processes, the content of impurities such as CH4, CO2, CO, O2, H2S, water vapor, and N2 in hydrogen is relatively high after detection. Therefore, it is necessary to provide a hydrogen deep impurity removal process to further perform targeted deep impurity removal so that the purity of hydrogen can reach 99.9999+%. Summary of the Invention

[0004] The present invention discloses a flexible selection process and device for deep impurity removal of hydrogen in a low-temperature environment, and efficiently solves the problem of deep impurity removal of hydrogen. The specific solutions are as follows:

[0005] A flexible selection device for deep impurity removal of hydrogen in a low-temperature environment includes: a raw material gas heat exchanger (1), a liquid nitrogen tank (2), a main gas pipe (3), a plurality of first branch gas pipes (6), a plurality of second branch gas pipes (7), a hydrogen storage tank (8), a vacuum pump (9), and a plurality of valves (10), wherein the liquid nitrogen tank includes a cryogenic buffer tank (4) and a plurality of adsorption towers (5);

[0006] The two sides of the raw material gas heat exchanger are respectively connected to the main gas pipe (3), and one end is respectively connected to the cryogenic buffer tank (4), several adsorption towers (5) and a vacuum pump (9). The other ends of the cryogenic buffer tank (4) and several adsorption towers (5) are respectively connected to the main gas pipe (3) through the first branch gas pipe (6). At the same time, the other ends of several adsorption towers (5) are also respectively connected to the hydrogen storage tank (8) through the second branch gas pipe (7).

[0007] Preferably, the main gas pipe (3), several first branch gas pipes (6), several second branch gas pipes (7) and the hydrogen storage tank (8) are all equipped with flow meters, thermometers and pressure gauges. Among them, the hydrogen storage tank (8) is also equipped with a vent valve.

[0008] Preferably, the vacuum pump (9) is connected to a discharge pipe.

[0009] Preferably, the raw material gas heat exchanger (1) is a buffer gas cylinder and / or a coil pipe and / or a straight conduit.

[0010] A flexible selection process for deep hydrogen purification in a low-temperature environment is as follows:

[0011] S1. Heat exchange of raw material hydrogen: The hydrogen raw material passes through the main gas pipe (3) through the raw material gas heat exchanger (1). After the temperature is reduced to 20 °C, it is introduced into the liquid nitrogen tank (2);

[0012] S2. Liquid nitrogen cryogenic cooling: After the hydrogen raw material is introduced into the liquid nitrogen tank (2), it is first introduced into the cryogenic buffer tank (4) for cooling;

[0013] S3. Flexible selection of impurity removal module: After the hydrogen is cooled, the flexible selection impurity removal module in the cryogenic buffer tank (4) mixes the hydrogen and re-selects it into several module gases. After the selection, it is introduced into the main gas pipe (3) again through the first branch gas pipe (6) connected to the cryogenic buffer tank (4);

[0014] S4. Impurity removal: The main gas pipe (3) introduces the hydrogen into several adsorption towers (5) for impurity removal;

[0015] S5. Hydrogen storage: After the impurity removal by the adsorption tower (5), the hydrogen is introduced through the second branch gas pipe (7) connected to each adsorption tower (5) and stored in the hydrogen storage tank (8);

[0016] S6. Vacuum pump discharge: After all the impurities are removed, each adsorption tower (5) can introduce these impurities into the main gas pipe (3) through the connected second branch gas pipe (7) and transport them to the discharge pipe through the vacuum pump for discharge.

[0017] Preferably, the temperature range of the liquid nitrogen tank is between 73K - 53K.

[0018] Preferably, the adsorbents contained in the cryogenic buffer tank (4) include: lithium-based molecular sieve, silica gel, activated alumina, and activated carbon.

[0019] Preferably, the modules flexibly selected and matched in step S3 include, but are not limited to, the "steam + N2" module, the "CO + H2S" module, the "O2 + steam" module, and the "CO + CO2 + CH4" module.

[0020] Preferably, the impurities discharged from the adsorption tower (5) include water vapor, N2, CO, O2, H2S, CO2, and CH4.

[0021] Preferably, the working pressure of the hydrogen storage tank (8) is 0 - 10 MPa.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The process of the present invention is simple, pollution-free, requires less equipment investment, and the production and purification efficiency is as high as 99.9999%.

[0024] 1. Combination of low-temperature adsorption and temperature swing regeneration

[0025] Innovative process combination: Combining liquid nitrogen cryogenic cooling with temperature swing regeneration of the adsorption tower, effectively removing impurities in the low-temperature adsorption stage, and then realizing the regeneration of the adsorbent by heating the adsorption tower, avoiding the performance attenuation problem of the adsorbent caused by long-term low temperature in the traditional cryogenic process.

[0026] 2. Application expansion of lithium-based molecular sieve

[0027] New adsorbent adapted to low-temperature environment: Using lithium-based molecular sieve to replace the traditional 5A molecular sieve, the adsorption capacity of lithium-based material for CO at low temperature is significantly improved.

[0028] 3. Full-process closed-loop control and safety

[0029] Pressure-temperature-flow linkage monitoring: By real-time monitoring the parameters of the main path and branch paths, dynamically adjusting the working states of the cryogenic buffer tank and the adsorption tower, avoiding the instability of hydrogen purity caused by fluctuations in the raw gas components.

[0030] 4. Low energy consumption and low-cost design

[0031] Cascaded utilization of liquid nitrogen cold energy: The cryogenic buffer tank uses the liquid nitrogen cold energy to precool hydrogen, reducing the cooling load of the subsequent adsorption tower, lowering energy consumption, and the present invention optimizes the cold energy distribution through hierarchical treatment.

[0032] Modular reuse of adsorption towers: Multiple adsorption towers can operate in parallel or in series, and are flexibly enabled according to the impurity concentration, reducing equipment redundancy, and the present invention has a significant improvement in equipment utilization rate. Description of the Drawings

[0033] The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0034] Figure 1 It is a schematic diagram of the overall structure of a flexible selection device for deep hydrogen purification in a low-temperature environment related to the present invention;

[0035] Figure 2 It is a process flow chart of a flexible selection process for deep hydrogen purification in a low-temperature environment involved in the invention. Specific Embodiments

[0036] In order to make the purpose and advantages of the present invention clearer, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and do not limit the protection scope of the present invention.

[0038] A flexible selection device for deep hydrogen purification in a low-temperature environment includes: a raw material gas heat exchanger (1), a liquid nitrogen tank (2), a main gas pipe (3), a number of first branch gas pipes (6), a number of second branch gas pipes (7), a hydrogen storage tank (8), a vacuum pump (9) and a number of valves (10), wherein the liquid nitrogen tank includes a cryogenic buffer tank (4) and a number of adsorption towers (5);

[0039] Both sides of the raw material gas heat exchanger are respectively connected to the main gas pipe (3) and one end is respectively connected to the cryogenic buffer tank (4), a number of adsorption towers (5) and the vacuum pump (9). At the other end of the cryogenic buffer tank (4) and a number of adsorption towers (5), they are respectively connected to the main gas pipe through the first branch gas pipes (6) (3). At the same time, the other end of a number of adsorption towers (5) is also respectively connected to the hydrogen storage tank (8) through the second branch gas pipes (7).

[0040] Preferably, the main gas pipe (3), a number of first branch gas pipes (6), a number of second branch gas pipes (7) and the hydrogen storage tank (8) are all provided with flow meters, thermometers and pressure gauges, and the hydrogen storage tank (8) is also provided with a vent valve.

[0041] Preferably, the vacuum pump (9) is connected to a discharge pipe.

[0042] Preferably, the raw material gas heat exchanger (1) is a buffer gas cylinder and / or a coil and / or a straight conduit.

[0043] Example 1:

[0044] Raw material gas, pressure: 8 MPa, flow rate: 20 mL to 1 m3 / min, temperature: atmospheric temperature -30~40℃.

[0045] S1, raw hydrogen heat exchange: the hydrogen raw material passes through the main gas pipe 3 and the raw gas heat exchanger 1, and after the temperature is reduced to 20°C, it is passed into the liquid nitrogen tank 2;

[0046] S2, liquid nitrogen cryogenics: After the hydrogen raw material is passed into the liquid nitrogen tank 2, it is first passed into the cryogenic buffer tank 4 to be cooled to 70K;

[0047] S3, flexible selection of impurity removal module: After the hydrogen is cooled, the "steam + N2" module in the cryogenic buffer tank (4) is selected, and the hydrogen is introduced into the main gas pipe 3 again through the first branch gas pipe 6 connected to the cryogenic buffer tank 4;

[0048] S4, impurity removal: The main gas pipe (3) passes hydrogen into adsorption towers A and B, and is adsorbed by fixed bed adsorbents in towers A and B in turn to remove a small amount of impurities in the raw hydrogen;

[0049] S5, hydrogen storage: After the impurities are removed from the adsorption tower 5, the hydrogen is introduced into the hydrogen storage tank 8 through the second branch gas pipe (7) and stored. At this point, the cryogenic impurity removal is completed. The remaining adsorption towers do not participate in the impurity removal process, and the adsorbent is regenerated by heating.

[0050] S6, vacuum pump discharge: After all impurities are removed, the vacuum pump is turned on, and each adsorption tower (5) can pass these impurities into the main gas pipe (3) through the connected second branch gas pipe (7), evacuate the system, and transport them to the discharge pipe for discharge through the vacuum pump.

[0051] Furthermore, the adsorbent contained in the cryogenic buffer tank (4) includes: lithium-based molecular sieve, silica gel, activated alumina, activated carbon, wherein the treatment is carried out by lithium-based molecular sieve, and the specific advantages are:

[0052] Outstanding nitrogen separation ability: Lithium-based molecular sieves can selectively adsorb oxygen molecules (dynamic diameter of about 0.346nm) due to their small pore size (about 0.3-0.4nm), while nitrogen molecules (0.364nm) are not easily adsorbed due to their slightly larger size, thus achieving efficient nitrogen and oxygen separation.

[0053] Better moisture resistance: Compared with sodium-based molecular sieves, lithium-based molecular sieves are more adaptable to humid environments, have more stable performance in the treatment of humid gases, and reduce the risk of failure caused by moisture adsorption

[0054] Mature industrial applications: Widely used in nitrogen generators, air separation equipment and other fields, especially suitable for scenarios requiring high-purity nitrogen (more than 99%), such as electronic manufacturing, chemical synthesis, etc.

[0055] Further, the modules flexibly selected and matched in step S3 further include a "CO + H2S" module, an "O2 + steam" module, and a "CO + CO2 + CH4" module.

[0056] Further, the working pressure of the hydrogen storage tank (8) is 5 MPa.

[0057] Further, at least 1 cryogenic buffer tank and several adsorption towers connected in series / parallel and filled with different adsorbents are arranged inside the liquid nitrogen tank body;

[0058] Further, during actual operation, the adsorption towers are in a flexible working state. When one adsorption tower is in the adsorption operation, the remaining adsorption towers can be in the regeneration state, and so on in a cycle. Each tower can select the type and ratio of the adsorbent according to the raw material inlet gas volume and impurity components.

[0059] Summary: The raw material gas is high-purity hydrogen of 99.999%. After removing impurities from the hydrogen through technologies such as membrane separation, it is detected that the purity of the hydrogen reaches 99.9999%. The impurities with relatively high contents are mainly water vapor and N2, both of which are 2 ppm.

[0060] Example 2:

[0061] The industrial high-purity hydrogen (99.999%) commonly used in hydrogen refueling stations at present has exceeded standards for carbon monoxide and sulfides; raw material hydrogen: 99.999% industrial high-purity hydrogen;

[0062] Raw material gas, pressure: 3 MPa, flow rate: 5 mL to 1 m 3 / min, temperature: ambient atmospheric temperature - 10 to 45 °C.

[0063] The impurity removal module selected and matched for the raw material hydrogen is a "CO + H2S" module. According to the sequence of first removing CO and then removing H2S, it passes through the fixed-bed adsorbents in Tower C and Tower E in sequence to remove a small amount of impurities in the raw material hydrogen. The hydrogen after impurity removal and purification is stored in the hydrogen storage tank, and the cryogenic impurity removal is completed. The remaining adsorption towers do not participate in the impurity removal process, and the adsorbent is regenerated by heating. Open the vacuum pump to evacuate the system and wait for the next cycle to resume the cryogenic impurity removal process.

[0064] Example 3:

[0065] During the process of hydrogen production by water electrolysis, there is oxygen shuttling between the anode and the cathode, resulting in a small amount of oxygen and water vapor impurities in the hydrogen obtained by electrolyzing water. At present, the highest purity of the hydrogen produced by electrolyzing water is about 99.9%.

[0066] Raw material gas: hydrogen produced by water electrolysis of 99.9%

[0067] Feed gas, pressure: 1.6 MPa, flow rate: 1000 Nm3 / h, temperature: ambient temperature - 20 to 30 °C.

[0068] The feed gas enters the cryogenic buffer tank through the feed valve. The selected impurity removal module is the "O2 + water vapor" module. According to the adsorption impurity removal settings, in the order of first dehydrating water vapor and then removing O2, it passes through the fixed-bed adsorbents in Tower A and Tower D in sequence to remove a small amount of impurities in the raw hydrogen gas. After the hydrogen gas is purified by removing impurities, it is stored in the hydrogen storage tank, and the cryogenic impurity removal is completed. The remaining adsorption towers do not participate in the impurity removal process, and the adsorbents are regenerated by heating. Open the vacuum pump to evacuate the system and wait for the next cycle to resume the cryogenic impurity removal process.

[0069] The advantages of the present invention include:

[0070] High efficiency of cryogenic adsorption and deep cooling combined for impurity removal

[0071] Enhanced adsorption capacity in low-temperature environment: Cool the hydrogen gas to ultra-low temperature state through liquid nitrogen deep cooling (73K - 53K), combined with lithium-based molecular sieve and silica gel adsorbents, significantly improving the adsorption efficiency of trace impurities (such as CO, H2S). In a low-temperature environment, the surface molecular activity of the adsorbent decreases, and the selective adsorption is enhanced. Especially for difficult-to-treat impurities such as CO, the removal effect is better than that of traditional normal-temperature adsorption. Hierarchical treatment of the cryogenic buffer tank and adsorption tower: The cryogenic buffer tank (4) initially removes high-concentration impurities (such as N2, CH4), and the adsorption tower (5) conducts fine treatment for the remaining low-concentration impurities. The hierarchical strategy reduces the adsorbent load and extends the service life. This solution further optimizes the process modularization and flexible configuration through a low-temperature environment;

[0072] Multi-branch parallel design: Through the flexible switching of the first branch (6) and the second branch (7), the combination mode of the adsorption towers can be dynamically adjusted according to the types and concentrations of impurities in the feed gas, better adapting to the diverse requirements of different industrial by-product hydrogen (such as coke oven gas, chlor-alkali by-product hydrogen). Adaptive pressure and flow control: The main road and branches are equipped with flow meters, thermometers, and pressure gauges. Combined with the vent valve of the hydrogen storage tank (8), precise regulation within the pressure range of 0 - 10 MPa is achieved, meeting the different scenario requirements of hydrogen for fuel cell vehicles (high-pressure hydrogen storage) and industrial hydrogen use (medium and low pressure).

[0073] Optimization of adsorbent regeneration and impurity discharge

[0074] Vacuum pump-driven impurity desorption: Use the vacuum pump (9) to quickly suck out the residual impurities in the adsorption tower. Compared with the multiple equal-pressure regenerations of traditional pressure swing adsorption (PSA), this process shortens the regeneration time and reduces hydrogen loss, improving the recovery rate.

[0075] Combination of cryogenic adsorption and temperature-variable regeneration

[0076] Innovative process combination: Combining cryogenic nitrogen liquefaction with temperature swing regeneration of the adsorption tower to efficiently remove impurities during the low-temperature adsorption stage, and then regenerating the adsorbent by heating the adsorption tower to avoid the performance degradation problem of the adsorbent caused by long-term low temperature in the traditional cryogenic process.

[0077] Expansion of the application of lithium-based molecular sieves

[0078] New adsorbent adapted to low-temperature environment: Using lithium-based molecular sieves to replace traditional 5A molecular sieves, the adsorption capacity of lithium-based materials for CO at low temperature is significantly improved, especially suitable for the strict requirement of CO≤0.2ppm in hydrogen for fuel cells.

[0079] Full-process closed-loop control and safety

[0080] Pressure-temperature-flow linkage monitoring: By real-time monitoring the parameters of the main path and branch paths, dynamically adjusting the working states of the cryogenic buffer tank and the adsorption tower to avoid the instability of hydrogen purity caused by fluctuations in the raw gas composition.

[0081] Low energy consumption and low cost design

[0082] Cascaded utilization of the cold energy of liquid nitrogen: The cryogenic buffer tank uses the cold energy of liquid nitrogen to precool hydrogen, reducing the cooling load of the subsequent adsorption tower and lowering the energy consumption, while this solution optimizes the cold energy distribution through hierarchical treatment

[0083] Modular reuse of adsorption towers: Multiple adsorption towers can operate in parallel or in series, and can be flexibly enabled according to the impurity concentration, reducing equipment redundancy. This solution has a significant improvement in equipment utilization rate.

[0084] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A flexible selection device for deep hydrogen purification in a low-temperature environment, characterized in that, Including: Raw gas heat exchanger (1), liquid nitrogen tank (2), main gas pipe (3), several first branch gas pipes (6), several second branch gas pipes (7), hydrogen storage tank (8), vacuum pump (9) and several valves (10). Among them, the liquid nitrogen tank includes a cryogenic buffer tank (4) and several adsorption towers (5); Both sides of the raw gas heat exchanger are respectively connected to the main gas pipe (3), and one end is respectively connected to the cryogenic buffer tank (4), several adsorption towers (5) and the vacuum pump (9). At the other end of the cryogenic buffer tank (4) and several adsorption towers (5), they are respectively connected to the main gas pipe (3) through the first branch gas pipes (6). At the same time, the other end of several adsorption towers (5) is also respectively connected to the hydrogen storage tank (8) through the second branch gas pipes (7).

2. The flexible selection and matching device for deep hydrogen purification in a low-temperature environment according to claim 1, characterized in that, Flow meters, thermometers and pressure gauges are provided on the main gas pipe (3), several first branch gas pipes (6), several second branch gas pipes (7) and the hydrogen storage tank (8). Among them, the hydrogen storage tank (8) is also provided with a vent valve.

3. The flexible selection and matching device for deep impurity removal of hydrogen in a low-temperature environment according to claim 1, characterized in that The vacuum pump (9) is connected to the discharge pipe.

4. The flexible selection process for deep hydrogen purification under low-temperature environment according to claim 1, characterized in that, The raw gas heat exchanger (1) is a buffer gas cylinder and / or coil pipe and / or straight pipe.

5. A flexible selection process for deep hydrogen purification under low-temperature environments, characterized in that, The specific steps are as follows: S1. Incoming gas heat exchange: Hydrogen raw material passes through the main gas pipe (3) through the raw gas heat exchanger (1), and after the temperature is reduced to 20 °C, it is introduced into the liquid nitrogen tank (2); S2. Liquid nitrogen cryogenic cooling: After the hydrogen raw material is introduced into the liquid nitrogen tank (2), it is first introduced into the cryogenic buffer tank (4) for cooling; S3. Flexible selection and matching of impurity removal modules: After the hydrogen is cooled, the flexible selection and matching impurity removal module in the cryogenic buffer tank (4) mixes the hydrogen and re-selects and matches it into several module gases. After the selection and matching, it is introduced into the main gas pipe (3) again through the first branch gas pipe (6) connected to the cryogenic buffer tank (4); S4. Impurity removal: The main gas pipe (3) introduces hydrogen into several adsorption towers (5) for impurity removal; S5. Hydrogen storage: After the impurity removal by the adsorption tower (5), the hydrogen is introduced into and stored in the hydrogen storage tank (8) through the second branch gas pipe (7) connected to each adsorption tower (5); S6. Vacuum pump discharge: After all the impurities are removed, each adsorption tower (5) can introduce these impurities into the main gas pipe (3) through the connected second branch gas pipe (7) and transport them to the discharge pipe through the vacuum pump for discharge.

6. The flexible selection and matching process for deep hydrogen purification under low temperature environment according to claim 5, characterized in that, The temperature range of the liquid nitrogen tank is 73K - 53K.

7. A flexible selection process for deep hydrogen purification under low-temperature environment according to claim 5, characterized in that, The adsorbents contained in the cryogenic buffer tank (4) include: lithium-based molecular sieve, silica gel, activated alumina, activated carbon.

8. A flexible selection process for deep hydrogen purification under low-temperature environments according to claim 5, characterized in that, The modules flexibly selected and matched in step S3 include but are not limited to "water vapor + N2" module, "CO + H2S" module, "O2 + water vapor" module and "CO + CO2 + CH4" module.

9. The flexible selection process for deep impurity removal of hydrogen in a low-temperature environment according to claim 5, characterized in that The impurities discharged from the adsorption tower (5) include water vapor, N2, CO, O2, H2S, CO2 and CH4.

10. The flexible selection process for deep hydrogen purification under low temperature environments according to claim 5, characterized in that, The working pressure of the hydrogen storage tank (8) is 0 - 10 MPa.

Images