Process for the underground production of hydrogen separation and purification

Abstract

The application relates to the technical field of chemical purification, in particular to an underground hydrogen separation and purification process. The process comprises the following steps: (1) the mixed gas to be separated and purified is introduced into a -5 to -1 DEG C tetrachloromethane solution to remove residual water, and then introduced into a calcium chloride dryer to remove residual water; (2) the mixed gas after the water is removed is introduced into a reaction bed paved with 50 to 60 DEG C chromium slag to remove residual hydrogen sulfide, and then introduced into a hydrogen sulfide absorption liquid to remove residual hydrogen sulfide; (3) the mixed gas after the hydrogen sulfide is removed is filtered through a composite permeation membrane to obtain hydrogen after separation and purification; the composite permeation membrane comprises a palladium layer, a vanadium layer and a polysulfone base layer, and the vanadium layer is located between the palladium layer and the polysulfone base layer. The purification process can improve the separation purity and speed of hydrogen by adopting the composite permeation membrane composed of the palladium layer, the vanadium layer and the polysulfone base layer, and can protect the palladium layer and improve the separation effect of the palladium layer on hydrogen by two-step water removal and two-step hydrogen sulfide removal.

Description

Technical Field

[0001] This application relates to the field of gas purification technology, specifically to an underground hydrogen production separation and purification process. Background Technology

[0002] Traditional hydrogen production typically relies on fossil fuels such as natural gas, crude oil, and coal, accounting for 96% of global hydrogen production. 3.9% comes from water electrolysis and 0.1% from other methods. Biological methods for hydrogen production are currently a hot topic. Because the reactants, production methods, gas composition, and conditions differ between conventional and bio-hydrogen production, their gas compositions also differ. To simplify the separation and purification process, the reproduction and fermentation of methanogens can be restricted. This results in a mixture of hydrogen, carbon dioxide, carbon monoxide, and other trace gases, primarily composed of these underground microbial hydrogen production components. Furthermore, due to the characteristics of underground microbial hydrogen production, a significant portion of the water in the mixture needs to be removed.

[0003] Traditional hydrogen separation and purification technologies include cryogenic separation, pressure swing adsorption (PSA), chemisorption, and membrane separation. Cryogenic separation, as the earliest and most widely used separation method, does not require the introduction of excessive chemical components, but it consumes a large amount of energy to maintain the low temperature, resulting in high costs. Chemisorption also requires a large amount of sodium hydroxide. The biggest drawback of pressure swing adsorption is its very low hydrogen recovery rate. Due to the characteristics of hydrogen production by underground microorganisms, the hydrogen content in the obtained mixed gas is already relatively low, making this method impractical. Most importantly, the hydrogen purity obtained by the above three methods is also relatively low.

[0004] Membrane separation is the most popular method. However, the composition of the gas produced during microbial hydrogen production is different from that of the mixed gas produced by conventional petroleum cracking. Microbial fermentation produces carbon dioxide and hydrogen products, and may also produce a small amount of hydrogen sulfide. Therefore, it is necessary to study and explore methods specifically for the separation and purification of hydrogen produced by microorganisms, and to improve the separation efficiency as much as possible. Summary of the Invention

[0005] To address the aforementioned issues, an underground hydrogen production separation and purification process is provided. This method employs a composite permeation membrane composed of a palladium layer, a vanadium layer, and a polysulfone substrate. This improves the purity and speed of hydrogen separation. Considering the small amount of hydrogen sulfide and the large amount of water produced in microbial hydrogen production, the process first involves two steps of water removal and two steps of hydrogen sulfide removal before separation via the composite permeation membrane. This protects the palladium layer and enhances the membrane's hydrogen separation efficiency. Furthermore, the three-layer composite structure of palladium, vanadium, and polysulfone substrate is used. The palladium layer has high hydrogen adsorption efficiency, while the vanadium layer has high hydrogen conductivity. Combined with the high-hardness polysulfone substrate, this not only improves the overall strength of the composite permeation membrane but also further enhances the hydrogen separation effect.

[0006] According to one aspect of this application, an underground hydrogen production separation and purification process is provided, comprising the following steps:

[0007] (1) The mixed gas to be separated and purified is passed into a tetrachloromethane solution at -5 to -1℃ for preliminary dehydration, and then passed into a calcium chloride dryer to remove residual moisture.

[0008] (2) After the moisture-removed mixed gas is passed through a reaction bed with chromium slag at 50-60℃ for preliminary desulfurization, it is then passed into a hydrogen sulfide absorption liquid to remove residual hydrogen sulfide.

[0009] (3) The mixed gas after removing hydrogen sulfide is filtered through a composite permeation membrane to obtain separated and purified hydrogen.

[0010] The composite permeation membrane comprises a palladium layer, a vanadium layer, and a polysulfone base layer, wherein the vanadium layer is located between the palladium layer and the polysulfone base layer.

[0011] Optionally, the thickness of the composite permeation membrane is 90–120 μm.

[0012] Optionally, the thickness ratio of the palladium layer, vanadium layer and polysulfone base layer is (1-2):(3-5):10.

[0013] Optionally, the thickness ratio of the palladium layer, vanadium layer, and polysulfone base layer is 1:4:10.

[0014] Optionally, the preparation steps of the composite permeation membrane include:

[0015] (a) Clean the substrate surface and place it in a vacuum chamber, fill it with argon gas as a protective gas, and sputter to deposit a vanadium film to obtain a vanadium layer;

[0016] (b) Using chemical plating, the vanadium layer is immersed in the palladium plating solution, a palladium film is covered on the outside of the vanadium layer, and the vanadium layer and palladium layer are obtained after removing the substrate;

[0017] (c) After heating the polysulfone to a molten state, the polysulfone is sprayed onto the side of the vanadium film away from the palladium layer using a spraying device, and the composite permeation membrane is obtained after cooling.

[0018] Optionally, the outer side of the vanadium layer may be polished before step (b).

[0019] Optionally, the palladium plating solution comprises palladium salt, EDTA, urea-formaldehyde, hydrochloric acid, and ammonia.

[0020] Optionally, the urea-formaldehyde concentration is 10–15 g / L.

[0021] Optionally, the palladium plating solution may also contain ethylene glycol.

[0022] Optionally, the concentration of the ethylene glycol is 50–100 ml / L.

[0023] The beneficial effects of this application include, but are not limited to:

[0024] 1. According to the underground hydrogen production separation and purification process of this application, a composite permeation membrane composed of a palladium layer, a vanadium layer, and a polysulfone base layer is used. The palladium layer can effectively adsorb and dissociate hydrogen, while the vanadium layer has a good hydrogen permeation effect and can conduct the hydrogen adsorbed and dissociated by the palladium layer. Moreover, the vanadium layer has high strength and can provide good protection for the palladium layer, preventing the palladium layer from cracking. The use of a polysulfone base layer further separates the hydrogen and improves the hydrogen separation effect.

[0025] 2. According to the underground hydrogen production separation and purification process of this application, the thickness of the composite permeation membrane is 90-120 μm, wherein the thickness ratio of the palladium layer, vanadium layer and polysulfone base layer is (1-2):(3-5):10. The polysulfone base layer is the thickest and is located on the outermost layer in contact with the mixed gas. It can protect the palladium and vanadium layers by means of its thickness and hardness, and can further separate hydrogen, so as to obtain higher hydrogen purity. The palladium layer has a good separation effect on hydrogen, but its permeability is poor. By setting the thinnest palladium layer and combining it with the thicker vanadium layer with good hydrogen permeability, the hydrogen separation efficiency can be improved.

[0026] 3. According to the underground hydrogen production separation and purification process of this application, the composite permeation membrane has a three-layer sandwich structure, in which the thickness of the palladium layer, vanadium layer and polysulfone base layer increases sequentially. Among the palladium layer, vanadium layer and polysulfone base layer, the vanadium layer has the best hydrogen permeability, while the palladium layer and polysulfone base layer on both sides have good hydrogen separation effect. By setting the above-mentioned composite permeation membrane, the hydrogen separation efficiency can be improved as much as possible, the hydrogen separation effect can be better, and the strength and service life of the composite permeation membrane can also be improved.

[0027] 4. According to the underground hydrogen production separation and purification process of this application, due to the characteristics of microbial hydrogen production, the mixed gas will carry a large amount of water and trace amounts of hydrogen sulfide. The presence of hydrogen sulfide and water will inhibit the activity of the palladium layer and reduce the adsorption and dissociation effect of the palladium layer on hydrogen. Therefore, the purification process first removes water and then adds a step to remove hydrogen sulfide.

[0028] 5. According to the underground hydrogen production separation and purification process of this application, water and hydrogen sulfide in the mixed gas are removed in two steps before separation by the composite permeation membrane. This can completely remove water and hydrogen sulfide from the mixed gas, protect the composite permeation membrane, greatly extend the service life of the composite permeation membrane, and improve the separation effect and efficiency of the composite permeation membrane for hydrogen.

[0029] 6. According to the underground hydrogen production separation and purification process of this application, by adding urea-formaldehyde to the palladium plating solution, the formation time of the palladium layer in the electroless plating can be extended, thereby improving the brush plating effect. This results in a palladium layer with higher uniformity and a denser coating, without causing excessive palladium deposition. However, the excessive density of the palladium layer also leads to poor hydrogen permeability, resulting in low hydrogen recovery efficiency. Further, by adding ethylene glycol to the palladium plating solution to adjust the palladium layer, the permeability of hydrogen can be significantly improved while ensuring the excellent filtration effect of the palladium layer, thereby increasing the hydrogen recovery rate.

[0030] 7. According to the underground hydrogen production separation and purification process of this application, since the main components of the mixed gas formed by underground hydrogen production by microorganisms are carbon dioxide and hydrogen, compared with other hydrogen production methods, the mixed gas containing hydrogen prepared by this method also has the characteristics of high water vapor content and small amount of hydrogen sulfide. In view of the characteristics of the components in the above-mentioned mixed gas, by using a purification process with a composite permeation membrane, hydrogen can specifically and efficiently permeate through the composite permeation membrane, thereby effectively separating carbon dioxide and hydrogen. Furthermore, removing water and hydrogen sulfide in the early stage of the purification process can further improve the filtration efficiency and service life of the composite permeation membrane. Therefore, this hydrogen production separation and purification process is particularly suitable for the separation of underground hydrogen production by microorganisms. Detailed Implementation

[0031] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0032] Unless otherwise specified, the raw materials and chemical reagents used in the embodiments of this application were all purchased commercially.

[0033] Example 1

[0034] Preparation of composite permeable membrane

[0035] (a) Using silicon as a substrate, the substrate is cleaned and dried for later use. The silicon substrate is placed in a vacuum chamber, first evacuated to a low vacuum, then to a high vacuum, and finally filled with argon protective gas to reach the working pressure. The silicon substrate is first cleaned with a parallel ion beam, and then the focusing source is turned on to clean the vanadium target, which can remove the oxide layer on the target surface. After that, sputtering deposition is started. The sputtering deposition conditions are: working pressure 2.0*10 -2 Pa, ion beam energy 900eV, coating time 10min, substrate temperature 260℃.

[0036] (b) Prepare activation solutions A and B, wherein the composition of activation solution A is 0.01 mol / L hydrochloric acid and 1 wt% tin chloride, and the composition of activation solution B is 0.01 mol / L hydrochloric acid and 1 wt% palladium chloride. Then, immerse the substrate carrying the vanadium layer into activation solutions A and B for 1 min each, and repeat the process 3 times to activate the vanadium layer with palladium seed crystals to make the electroplating rate more uniform.

[0037] Then, a palladium plating solution was prepared, which consisted of: 0.1-10 g / L dichlorotetraamminepalladium, 5-80 g / L EDTA, 100-600 ml / L ammonia, and 5-10 ml / L hydrochloric acid. The vanadium layer activated by the palladium seed crystal was immersed in the palladium plating solution and electroplated at 60°C. After rinsing with deionized water, it was dried in a vacuum oven at 120°C for 12 hours. After removing the substrate, the vanadium layer and palladium layer were obtained.

[0038] (c) After heating the polysulfone to 340°C to a molten state, the molten polysulfone is sprayed onto the other side of the vanadium film away from the palladium layer using a spraying device. After cooling, a composite permeation membrane is obtained.

[0039] The composite permeation membrane has a thickness of 90 μm, and the thickness ratio of the palladium layer, vanadium layer and polysulfone substrate is 1:4:10.

[0040] underground hydrogen production separation and purification

[0041] The mixed gas to be separated and purified is passed through a -3℃ tetrachloromethane solution for preliminary dehydration, and then passed through a calcium chloride dryer to remove residual moisture.

[0042] After the moisture-removed mixed gas is passed through a reaction bed with chromium slag laid at 55℃ for preliminary desulfurization, it is then passed into an N-methylethylene glycolamine solution to remove residual hydrogen sulfide.

[0043] The mixed gas after removing hydrogen sulfide was filtered through a composite permeation membrane to obtain separated and purified hydrogen gas, wherein the composite permeation membrane used was the composite permeation membrane prepared according to Example 1.

[0044] Example 2

[0045] The difference from Example 1 is that the composite permeation membrane has a thickness of 120 μm, the thickness ratio of the palladium layer, vanadium layer and polysulfone substrate is 1:5:10, and the hydrogen sulfide absorption solution is a monoethanolamine solution.

[0046] Example 3

[0047] The difference from Example 1 is that the thickness of the composite permeation membrane is 120 μm, the thickness ratio of the palladium layer, vanadium layer and polysulfone base layer is 2:3:10, the palladium salt in the palladium plating solution is palladium chloride, and the hydrogen sulfide absorption solution is diethanolamine solution.

[0048] Example 4

[0049] The difference from Example 1 is that the outer side of the vanadium layer is polished before step (b).

[0050] Example 5

[0051] The difference from Example 4 is that the palladium plating solution also includes 10 g / L of urea-formaldehyde.

[0052] Example 6

[0053] The difference from Example 5 is that the amount of urea-formaldehyde used in the palladium plating solution is 15 g / L.

[0054] Example 7

[0055] The difference from Example 5 is that the amount of urea-formaldehyde used in the palladium plating solution is 5 g / L.

[0056] Example 8

[0057] The difference from Example 5 is that the palladium plating solution also includes 80 ml / L of ethylene glycol.

[0058] Example 9

[0059] The difference from Example 8 is that the palladium plating solution also includes 100 ml / L of ethylene glycol.

[0060] Example 10

[0061] The difference from Example 8 is that the palladium plating solution also includes 50 ml / L of ethylene glycol.

[0062] Example 11

[0063] The difference from Example 1 is that the thickness of the composite permeation membrane is 50 μm.

[0064] Example 12

[0065] The difference from Example 1 is that the thickness of the composite permeation membrane is 150 μm.

[0066] Example 13

[0067] The difference from Example 1 is that the thickness ratio of the palladium layer, vanadium layer and polysulfone base layer is 1:1:1.

[0068] Example 14

[0069] The difference from Example 1 is that the thickness ratio of the palladium layer, vanadium layer and polysulfone base layer is 1:1:10.

[0070] Comparative Example 1

[0071] The difference from Example 1 is that the composite permeation membrane contains only a palladium layer.

[0072] Comparative Example 2

[0073] The difference from Example 1 is that the composite permeation membrane contains only polysulfone.

[0074] Comparative Example 3

[0075] The difference from Example 1 is that the underground hydrogen production separation and purification step lacks the calcium chloride dehydration step and the subsequent step of passing N-methylethylene glycolamine solution to remove residual hydrogen sulfide. That is, it only includes the previous dehydration and hydrogen sulfide removal steps.

[0076] Test Example 1

[0077] The purity and recovery rate of hydrogen after separation and purification in Examples 1-14 and Comparative Examples 1-3 were measured and calculated, and the results are shown in Table 1 below.

[0078] Table 1

[0079]

[0080]

[0081] Referring to Table 1, a comparison of the results of Example 4 and Example 1 shows that polishing the vanadium layer before covering it with the palladium layer in step (b) is beneficial to the uniformity and flatness of the palladium layer covering the outer side of the vanadium layer. Since the palladium layer has poor permeability to hydrogen, the thinnest palladium layer in the composite permeation membrane can be made uniform in thickness, avoiding some palladium layers being too thin, thereby improving the purity of hydrogen. A comparison of the results of Examples 5-7 and Example 1 shows that adding an appropriate amount of urea-formaldehyde to the palladium plating solution can prolong the palladium plating time, avoid excessive palladium deposition, and improve the uniformity of the plating layer, thereby increasing the density of the palladium layer prepared by chemical plating and thus improving the filtration effect of hydrogen. However, it also reduces the hydrogen recovery rate. A comparison of the results of Examples 8-10 and Example 1 shows that if urea-formaldehyde is added to the palladium plating solution along with an appropriate concentration of ethylene glycol, the density of the palladium layer can be slightly adjusted, so that the purity of the purified hydrogen does not decrease, while reducing the difficulty of hydrogen passing through the palladium layer and increasing the probability of hydrogen passing through the palladium layer, thereby improving the hydrogen recovery rate.

[0082] Comparing the results of Examples 11 and 12 with those of Example 1, it can be seen that if the composite permeation membrane is too thin, although the hydrogen recovery rate is improved, the hydrogen purity will decrease significantly. Conversely, if the composite permeation membrane is too thick, the hydrogen recovery rate will decrease significantly. Comparing the results of Examples 13 and 14 with those of Example 1, it can be seen that the thickness ratio of the palladium layer, vanadium layer, and polysulfone base layer also affects the hydrogen purity and recovery rate. Most importantly, since the composite permeation membrane may be subjected to pressure during air purification, a thicker polysulfone base layer is needed to prevent the palladium layer from breaking. At the same time, the vanadium layer has a high hydrogen permeation effect, which can promptly remove hydrogen, and also has very good hardness, which can improve the overall strength of the composite permeation membrane. The thinner palladium layer is responsible for directly contacting the gas to be separated and separating and purifying the hydrogen after dissociation.

[0083] A comparison of the results from Comparative Examples 1 and 2 and Example 3 shows that while the palladium-only scheme can guarantee high hydrogen purity, it results in a very low hydrogen recovery rate. The polysulfone-only scheme, on the other hand, does not achieve a high level of hydrogen purification. A comparison of the results from Comparative Example 3 and Example 3 shows that incomplete removal of hydrogen sulfide and moisture in the early stages affects the filtration efficiency of the palladium layer, leading to both reduced hydrogen purity and a lower hydrogen recovery rate. This indicates that the presence of hydrogen sulfide and moisture inhibits the function of the palladium layer, making thorough removal necessary in the early stages to improve the lifespan of the composite membrane.

[0084] Test Example 2

[0085] The lifespan of the composite permeation membranes in Examples 1, 5, 8 and Comparative Example 3 was tested only. The purity (%) of the hydrogen obtained after separation was measured after 100h, 500h and 1000h of use, respectively. The results are shown in Table 2 below.

[0086] Table 2

[0087]

[0088] Referring to Table 2, a comparison of the results of Examples 1, 5, and 8 with Comparative Example 3 shows that, due to the incomplete removal of moisture and hydrogen sulfide, the filtration and separation effect of the composite permeation membrane in Comparative Example 3 decreased significantly with increasing usage time. In Example 5, the addition of urea-formaldehyde to the palladium plating solution resulted in the highest density of the palladium layer, thus exhibiting the smallest decrease. While the decrease in Example 8 was less severe than that in Example 5 compared to Example 1, it was still much smaller than that in Example 1. However, the service life of Examples 1, 5, and 8 was all longer than that of Comparative Example 3.

[0089] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A process for separating and purifying hydrogen produced underground, characterized in that, Includes the following steps: (1) The mixed gas to be separated and purified is passed into a tetrachloromethane solution at -5~-1℃ for preliminary dehydration, and then passed into a calcium chloride dryer to remove residual moisture. (2) After removing moisture, the mixed gas is passed through a reaction bed with chromium slag at 50~60℃ for preliminary desulfurization, and then passed into a hydrogen sulfide absorption liquid to remove residual hydrogen sulfide. (3) The mixed gas after removing hydrogen sulfide is filtered through a composite permeation membrane to obtain separated and purified hydrogen; The composite permeation membrane comprises a palladium layer, a vanadium layer, and a polysulfone base layer, wherein the vanadium layer is located between the palladium layer and the polysulfone base layer, the thickness of the composite permeation membrane is 90~120μm, and the thickness ratio of the palladium layer, the vanadium layer, and the polysulfone base layer is (1~2):(3~5):10; The preparation steps of the composite permeation membrane include: (a) Clean the substrate surface and place it in a vacuum chamber, fill it with argon gas as a protective gas, and sputter to deposit a vanadium film to obtain a vanadium layer; (b) Using chemical plating, the vanadium layer is immersed in the palladium plating solution, a palladium film is covered on the outside of the vanadium layer, and the vanadium layer and palladium layer are obtained after removing the substrate; (c) After heating the polysulfone to a molten state, the polysulfone is sprayed onto the side of the vanadium film away from the palladium layer using a spraying device, and the composite permeation membrane is obtained after cooling. The palladium plating solution contains palladium salt, EDTA, urea-formaldehyde, hydrochloric acid, ammonia, and ethylene glycol. The concentration of urea-formaldehyde is 10-15 g / L, and the concentration of ethylene glycol is 50-100 ml / L.

2. The underground hydrogen production separation and purification process according to claim 1, characterized in that, The thickness ratio of the palladium layer, vanadium layer, and polysulfone base layer is 1:4:

10.

3. The underground hydrogen production separation and purification process according to claim 1, characterized in that, Before step (b), the outer side of the vanadium layer is polished.

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