Method for producing hydrogen by using coal mine goaf

Abstract

The invention relates to the technical field of biological energy, and particularly discloses a method for producing hydrogen by using a coal mine goaf, which comprises the following steps: mixing pretreated agricultural organic wastes with fermentation liquor and a culture solution containing a methane inhibitor, and conveying the mixture to the coal mine goaf through an injection well; utilizing natural ground temperature conditions in the goaf to enable microorganisms to perform co-fermentation on residual coal in the goaf and the injected agricultural organic waste to produce hydrogen; produced hydrogen is collected and output through a gas producing well, and fermentation residues are discharged through a material producing well. According to the hydrogen production method provided by the invention, the goaf is used as a natural reactor, and two wastes are synergistically converted, so that the hydrogen production cost and energy consumption are greatly reduced, meanwhile, environmental pollution is effectively avoided, and a new green way is provided for resource utilization of waste mines.

Description

Technical Field

[0001] This invention relates to the field of bioenergy technology, specifically to a method for producing hydrogen from coal mine goaf. Background Technology

[0002] With the global energy structure transformation and the deepening of the "dual-carbon" strategy, hydrogen energy, as a clean and efficient secondary energy source, has attracted much attention for its development and utilization. Biohydrogen production technology, especially the use of microbial fermentation to produce hydrogen, is considered one of the most promising hydrogen production pathways due to its mild conditions and ability to utilize waste resources.

[0003] Currently, most bio-hydrogen production technologies use single agricultural organic waste as substrates. However, single substrates often suffer from problems such as an imbalanced carbon-nitrogen ratio and a limited nutrient structure, which restricts the metabolic activity and hydrogen production efficiency of microorganisms and makes it difficult to convert waste from multiple sources (such as residual coal in coal mine goafs that is difficult to mine using traditional methods). In addition, existing bio-hydrogen production facilities (such as ground fermenters) typically require high construction and operation costs, and the reaction process consumes a large amount of energy.

[0004] Therefore, there is an urgent need in this field to develop a new method for producing hydrogen at low cost, high efficiency, and on a large scale, which can make full use of the existing geological conditions in coal mine goaf areas. Summary of the Invention

[0005] This invention provides a method for producing hydrogen from coal mine goaf areas. The hydrogen production method provided by this invention uses the goaf area as a natural reactor, synergistically converting two types of waste, significantly reducing hydrogen production costs and energy consumption, while effectively avoiding environmental pollution, providing a green new approach for the resource utilization of abandoned mines.

[0006] This invention provides a method for producing hydrogen from coal mine goaf, comprising the following steps: Agricultural organic waste, fermentation broth, and culture medium are mixed to form a mixture. The fermentation broth is obtained by processing coal samples collected from the goaf of the target coal mine. The processing involves: mixing the coal sample with the culture medium and culturing to obtain an initial enriched broth; mixing the agricultural organic waste, coal sample, culture medium, methane inhibitor, and initial enriched broth and then anaerobically fermenting to obtain an initial fermentation broth; and continuing to mix the agricultural organic waste, coal sample, culture medium, methane inhibitor, and initial fermentation broth and then anaerobically fermenting to obtain the final fermentation broth. The mixture is transported to the goaf of the target coal mine through an injection well and co-fermented with the residual coal therein for 80 to 100 days to decompose the two into hydrogen. The hydrogen produced by the co-fermentation is collected and exported through a gas-producing well.

[0007] The hydrogen production method provided by this invention uses the goaf as a natural reactor to synergistically transform two types of waste: agricultural organic waste and residual coal from the goaf. The hydrogen production efficiency when both wastes are used as substrates is significantly higher than that when one substrate is used alone, which greatly reduces the cost and energy consumption of hydrogen production, while effectively avoiding environmental pollution. This provides a green new approach for the resource utilization of abandoned mines.

[0008] Furthermore, the agricultural organic waste is corn stalks, sugarcane bagasse, beet pulp, soybean cake, or peanut bran.

[0009] Furthermore, the particle size of the agricultural organic waste is 20 mesh to 80 mesh.

[0010] Furthermore, the drying process is as follows: drying at 75℃~85℃ for 6 h~8 h.

[0011] Furthermore, the sterilization process specifically involves irradiating the surface with ultraviolet light for 30 to 60 minutes.

[0012] Furthermore, the culture medium contains inorganic salts, trace elements, an organic nitrogen source, vitamins, and a reducing agent; the inorganic salts include KCl, NaCl, MgCl2, NH4Cl, KH2PO4, K2HPO4, and NaHCO3; the organic nitrogen source is yeast extract; the trace elements include MgCl2·6H2O, FeCl2·4H2O, CoCl·6H2O, H3BO3, ZnSO4·7H2O, CuSO4·5H2O, NiSO4·6H2O, MnCl2·4H2O, and (NH4)6Mo7O 24 • 4H2O; the vitamins include vitamin B6, vitamin B1, vitamin B2, vitamin B3, vitamin B5, vitamin B12, lipoic acid, para-aminobenzoic acid, vitamin B7, and vitamin B9; the reducing agent includes Na2S and L-cysteine.

[0013] Furthermore, the methane inhibitor is sodium 2-bromoethylsulfonate.

[0014] Furthermore, the solid residue remaining after co-fermentation is collected and discharged through the feed well.

[0015] Furthermore, the injection well passes through the overlying Quaternary strata, tight rock strata, and coal seam roof from the surface and connects with the coal mine goaf; the gas production well and the feed well extend from the coal mine goaf through the coal seam roof, tight rock strata, and Quaternary strata to the surface.

[0016] Furthermore, the bottom of the coal mine goaf is a coal seam floor plate, and the top is covered by the coal seam roof plate; the sidewalls of the coal mine goaf are provided with an anti-seepage layer or are surrounded by dense rock strata.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The hydrogen production method provided by this invention realizes the co-processing and resource utilization of waste. It creatively utilizes the huge underground space of coal mine goaf as a natural bioreactor and the natural microbial community of coal seams in the mining area. It innovatively combines agricultural organic waste with residual coal in the goaf and simultaneously converts it into high-value-added hydrogen and organic fertilizer through microbial co-fermentation technology, realizing a circular economy model of "treating waste with waste and turning waste into treasure". At the same time, it uses the geothermal field to maintain the fermentation temperature, which greatly reduces the cost and energy consumption of hydrogen production, saves the expensive construction costs of traditional above-ground reactors and the purchase cost of hydrogen-producing bacteria, and makes large-scale, low-cost bio-hydrogen production possible.

[0018] The hydrogen production method provided by this invention not only reduces pollution from open burning and stockpiling of agricultural waste, but also eliminates the hidden dangers of spontaneous combustion of residual coal and the slow release of greenhouse gases. Simultaneously, the dense rock strata and impermeable structures overlying the goaf form a natural barrier, ensuring that the biochemical reaction process is safely contained underground, preventing secondary pollution of groundwater and surface ecology. This provides a novel and economically viable green revitalization solution for the vast number of abandoned coal mines, possessing the potential to transform traditional environmental liabilities into clean energy production bases, and aligning with sustainable development strategies. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the hydrogen production method based on the microbial degradation of residual coal and agricultural organic waste in coal mine goaf areas according to the present invention.

[0021] Explanation of reference numerals in the attached diagram: 1-Injection well, 2-Mixed material, 3-Quaternary strata, 4-Dense rock strata, 5-Coal seam roof, 6-Coal mine goaf, 7-Imperible layer, 8-Coal seam floor, 9-Production well, 10-Production gas well, 11-Residual coal, 12-Dense rock strata. Detailed Implementation

[0022] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0023] Example 1: A method for producing hydrogen from coal mine goaf.

[0024] Sugar beet pulp, a byproduct of sugar refining, was crushed and sieved to ensure a particle size of 50±30 mesh. After drying at 80℃ for 7 hours, it was sterilized under ultraviolet light for 45 minutes to obtain the agricultural organic waste. Coal collected from the in-situ coal seam goaf was aseptically crushed to a particle size of less than 1 cm to obtain coal samples.

[0025] In a conical flask containing 1 L of distilled water, add the following inorganic salts in sequence: 0.2 g KCl, 2.0 g NaCl, 2.0 g MgCl2, 1.0 g NH4Cl, 0.4 g KH2PO4, 0.4 g K2HPO4, and 1 g NaHCO3; organic nitrogen source: 1.0 g yeast extract; and trace elements: 0.05 g MgCl2·6H2O, 0.06 g FeCl2·4H2O, 0.0015 g CoCl·6H2O, 0.001 g H3BO3, 0.001 g ZnSO4·7H2O, 0.0005 g CuSO4·5H2O, 0.0045 g NiSO4·6H2O, 0.05 g MnCl2·4H2O, and 0.0064 g (NH4)6Mo7O. 24 ·4H2O, seal the mouth of the conical flask with medical absorbent cotton wrapped in cloth, and sterilize in an autoclave at 121℃ for 20 min. After sterilization, cool to room temperature to obtain the initial culture medium solution. Continue to add vitamins to the initial culture medium solution in sequence: 0.0001 g vitamin B6, 0.00005 g vitamin B1, 0.00005 g vitamin B2, 0.00005 g vitamin B3, 0.00005 g vitamin B5, 0.00005 g vitamin B12, 0.00005 g lipoic acid, 0.00005 g para-aminobenzoic acid, 0.00002 g vitamin B7 and 0.00002 g vitamin B9; reducing agent: 0.2 g Na2S and 0.5 g L-cysteine. After stirring evenly, sterilize under ultraviolet light for 40 min, adjust the pH to 7.0±0.2, and obtain 1 L of culture medium.

[0026] 100 g of coal sample was placed in an anaerobic flask, 1 L of culture medium was added, the air in the flask was replaced with nitrogen, and then sealed with an isobutyl stopper and sealing film. The flask was then placed in a 35°C incubator in the dark for 35 days to obtain the initial enrichment solution. 1.5 kg of agricultural organic waste and 1.5 kg of coal sample were added to an anaerobic fermenter, along with 100 L of culture medium, 100 g of sodium 2-bromoethylsulfonate, and 1 L of the initial enrichment solution. The air in the fermenter was replaced with nitrogen, and the flask was incubated at 35°C in the dark for 14 days to obtain the initial fermentation solution. 150 kg of agricultural organic waste and 150 kg of coal sample were then added to the anaerobic fermenter, along with 10 m³ of culture medium. 3 The culture medium was added, along with 10 kg of sodium 2-bromoethylsulfonate and 100 L of initial fermentation broth. The air in the tank was replaced with nitrogen, and the mixture was cultured at 35°C in the dark for 14 days to obtain 10 m... 3 Fermentation broth.

[0027] 15,000 kg of agricultural organic waste, 1,000 kg of sodium 2-bromoethylsulfonate, and 10 m 3 Fermentation broth and 1000 m 3 The culture medium, after being uniformly mixed, was used as a mixture and injected into a 3000 m³ well through injection well 1. 3 In the goaf of a coal mine, injection well 1, production well 9, and gas production well 10 were shut down for a simmering process, allowing residual coal 11 and the mixture to co-ferment. During this process, the temperature, pressure, and oxygen concentration in the goaf were continuously monitored to ensure the temperature remained at 35±10℃, the pressure below 0.5MPa, and a strictly anaerobic environment was maintained. After 90 days of simmering, the mixed gas (hydrogen concentration greater than 50%) produced by fermentation was pumped from gas production well 10 to the Quaternary strata above 3 using a vacuum pump. Subsequently, it was purified using a pressure swing adsorption (PSA) device to achieve a hydrogen concentration meeting the purity standards of GB / T3634.1-2006 "Hydrogen Part 1: Industrial Hydrogen" before being pumped into a hydrogen storage tank, producing a total of 400 m³ of hydrogen. 3 Hydrogen; the residual biogas residue after fermentation is pumped from the feed well 9 to the Quaternary strata above 3 using a biogas residue pumping equipment. A filter press is then used to reduce the moisture content of the biogas residue to below 70%, yielding a total of 600 m³. 3 The liquid and 10,000 kg of biogas residue were treated and stored separately in accordance with the industry standard NY / T 2374-2013 "Technical Specification for Post-treatment of Biogas Slurry and Biogas Residue in Biogas Engineering".

[0028] After the product collection was completed, 15,000 kg of agricultural organic waste and 1,000 m³ of other waste were disposed of. 3The culture medium, used as a mixture, was injected into the goaf 6 of the coal mine through injection well 1. The remaining liquid and hydrogen-producing bacteria in the slag were used to co-ferment the residual coal 11 and the mixture again. After 90 days of well shut-in, the hydrogen was collected and sent through gas-producing well 10 to the Quaternary strata above 3, producing a total of 360 m³ of hydrogen. 3 Hydrogen; the residual biogas residue after fermentation is sent through feed well 9 to the Quaternary strata above 3, with a total extraction of 800 m³. 3 The liquid and 12,000 kg of biogas residue were stored and utilized separately.

[0029] The bottom of the coal mine goaf 6 is a coal seam floor 8, and the top is covered by a coal seam roof 5. The upper part is successively covered by a dense rock layer 4 and a Quaternary stratum 3. The sides of the coal mine goaf 6 are a wall seepage-proof layer 7 and a dense rock layer 12 that can prevent gas flow. The injection well 1 is connected from the Quaternary stratum 3 to the coal mine goaf 6, and the production well 9 and the gas production well 10 are connected from the coal mine goaf 6 to the surface of the Quaternary stratum 3.

[0030] Although preferred embodiments of the invention have been described, those skilled in the art, once they have learned the basic inventive concept, can make other changes and modifications to these embodiments.

[0031] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for producing hydrogen from coal mine goaf, characterized in that, Includes the following steps: Agricultural organic waste, fermentation broth, and culture medium are mixed to form a mixture. The fermentation broth is obtained by processing coal samples collected from the goaf of the target coal mine. The processing involves: mixing the coal sample with the culture medium and culturing to obtain an initial enriched broth; mixing the agricultural organic waste, coal sample, culture medium, methane inhibitor, and initial enriched broth and then anaerobically fermenting to obtain an initial fermentation broth; and continuing to mix the agricultural organic waste, coal sample, culture medium, methane inhibitor, and initial fermentation broth and then anaerobically fermenting to obtain the final fermentation broth. The mixture is transported through injection well (1) to the goaf area (6) of the target coal mine, and co-fermented with the residual coal (11) therein for 80 to 100 days to decompose the two into hydrogen. Hydrogen produced by the co-fermentation is collected and exported through the gas-producing well (10).

2. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The agricultural organic waste mentioned includes corn stalks, sugarcane bagasse, beet pulp, soybean cake, or peanut bran.

3. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The particle size of the agricultural organic waste is 20 mesh to 80 mesh.

4. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The drying process is as follows: drying at 75℃~85℃ for 6 h~8 h.

5. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The sterilization process specifically involves irradiating the product under ultraviolet light for 30 to 60 minutes.

6. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The culture medium contains inorganic salts, trace elements, organic nitrogen sources, vitamins, and reducing agents; the inorganic salts include KCl, NaCl, MgCl2, NH4Cl, KH2PO4, K2HPO4, and NaHCO3; the organic nitrogen source is yeast extract; the trace elements include MgCl2·6H2O, FeCl2·4H2O, CoCl·6H2O, H3BO3, ZnSO4·7H2O, CuSO4·5H2O, NiSO4·6H2O, MnCl2·4H2O, and (NH4)6Mo7O. 24 • 4H2O; the vitamins include vitamin B6, vitamin B1, vitamin B2, vitamin B3, vitamin B5, vitamin B12, lipoic acid, para-aminobenzoic acid, vitamin B7, and vitamin B9; the reducing agent includes Na2S and L-cysteine.

7. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The methane inhibitor is sodium 2-bromoethylsulfonate.

8. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The solid residue remaining after co-fermentation is collected and discharged through the feed well (9).

9. The method for producing hydrogen from coal mine goaf according to claim 1, characterized in that, The injection well (1) passes through the overlying Quaternary strata (3), tight rock strata (4) and coal seam roof (5) from the surface and then connects with the coal mine goaf (6); the gas production well (10) and the feed well (9) extend from the coal mine goaf (6) through the coal seam roof (5), tight rock strata (4) and Quaternary strata (3) to the surface.

10. The method for producing hydrogen from coal mine goaf according to claim 9, characterized in that, The bottom of the coal mine goaf (6) is the coal seam floor plate (8), and the top is covered by the coal seam roof plate (5); the side walls of the coal mine goaf (6) are provided with an anti-seepage layer (7) or are surrounded by a dense rock layer (12).

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