Method for gasifying in-situ coal seam through nutrition-enhanced microorganisms

Abstract

The invention discloses a method for gasifying an in-situ coal seam by nutrition-enhanced microorganisms. The method comprises the following steps: S1, screening strains; s2, domesticating the strain; s3, screening the biomass; s4, preparing fermentation liquor; s5, the coal seam is fractured; s6, adding fermentation liquor and biomass; and S7, performing regular monitoring. The invention provides a method for gasifying an in-situ coal seam by nutrition-enhanced microorganisms, which mainly utilizes the conversion capacity of the biomass-enhanced microorganisms to the coal seam, collects the coal seam left in a goaf, and provides a proper living environment for the microorganisms, thereby economically and efficiently preparing the coal seam gas. According to the method, the yield of the coal bed gas can be effectively increased, the waste coal bed can be recycled, and meanwhile urban waste and algae can be reused, so that maximum utilization of resources is achieved, environmental pollution is reduced, and the utilization efficiency of the resources is improved.

Description

Technical Field

[0001] The invention relates to the technical field of in-situ coal seam fluidized mining, in particular to a method for gasifying an in-situ coal seam using nutrient-enhanced microorganisms. Background Art

[0002] There are many problems with the traditional coal mining and utilization model, such as low mining efficiency, serious waste of resources and serious environmental pollution. The traditional coal mining technology commonly used in my country often leaves coal pillars, and the geological conditions in some areas are complex, making it difficult to mine with modern mining technology. Therefore, we need an innovative method for coal mining and utilization. Microbial gasification in situ coal seam technology mainly relies on the degradation of organic matter in coal by microorganisms. Under suitable environmental conditions, microorganisms can convert coal into methane-based gas, which helps solve the problems of resource depletion and high mining costs faced by traditional coal mining methods.

[0003] Microbial gasification of in-situ coal seams is a complex process involving multiple bacterial species. At present, the process of microbial gasification of in-situ coal seams mainly includes strain screening and cultivation, nutrient injection, microbial metabolism and gas collection and utilization. However, the nutrients currently injected into coal seams are microbial culture media, which are expensive, environmentally unfriendly and unsustainable. The co-fermentation of biomass and coal can improve the efficiency of coal conversion to methane, enhance the stability of the fermentation system, and save the cost of coal biogasification. In a broad sense, biomass covers all kinds of organic matter such as plants and animals and their excremental waste. For example, typical biomass such as crops, crop residues, wood, wood waste and animal manure are rich in various nutrients, such as sugars, aldehydes, acids, alcohols, etc., which can enhance microbial activity and can be used as nutrients for microbial growth.

[0004] Compared with the traditional microbial gasification in situ coal seam technology, the method of using biomass as a nutrient source has many advantages: first, as a renewable resource, biomass is extremely abundant, and various types of biomass can be used, such as crop residues, urban waste, etc., which can more effectively adapt to the complex biomass composition in the current coal seam environment; second, biomass can improve the metabolic efficiency of microorganisms, maintain a high efficiency state, and thus increase the output of combustible gas; finally, biomass, as a green material, can reduce the production of by-products produced during microbial gasification, such as carbon dioxide, thereby reducing environmental pollution. Although the application of biomass as a nutrient source in microbial gasification in situ coal seams is still in its infancy, with the continuous advancement of science and technology, its application prospects will become more and more broad. With the continuous growth of energy demand, microbial gasification in situ coal seam technology will play an important role in the future energy field. Summary of the invention

[0005] The purpose of the present invention is to provide a method for nutrient-enhanced microbial gasification of in-situ coal seams. By studying the use of biomass instead of traditional nutrients, the cost of in-situ coal seam microbial gasification reactions is reduced and the stability of in-situ coal seam gasification is enhanced, so as to solve the problems of high cost and unsustainability in in-situ coal seam microbial gasification reactions raised in the above-mentioned background technology.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a method for in-situ coal seam gasification by nutrient-enhanced microorganisms, comprising the following steps:

[0007] S1. Screening of bacterial strains: using anaerobic sludge or natural soil to screen out highly efficient composite bacterial strains that can degrade coal in laboratory culture medium;

[0008] S2. Domestication of bacteria: According to the in-situ coal seam environment, with coal and biomass as substrates, the composite bacteria are cultured intensively, and composite fermentation bacteria that are adapted to the in-situ coal seam environment and have significant effects are selected, and gas production data are recorded;

[0009] S3. Biomass screening: Screen out economical and sustainable biomass, mainly organic matter containing carbon and nitrogen;

[0010] S4. Preparation of fermentation liquid: enrich various bacterial species cultured in the laboratory in the culture medium for 4-5 days, maintain the pH value constant at about 7, and prepare fermentation liquid;

[0011] S5. Fracturing coal seams: Pressing high-pressure water into deep-buried coal seams through directional drilling, causing the coal seams to fracture to varying degrees;

[0012] S6. Adding fermentation liquid and biomass: sequentially pressing the fermentation liquid and biomass into the directional drill hole of the coal seam, and sealing the drill hole;

[0013] S7. Regularly monitor the gas output. If the output decreases, add biomass to the coal seam to ensure sufficient nutrients and stable pH during the fermentation process.

[0014] Preferably, the composite bacteria selected in step S1 include: hydrolytic bacteria, hydrogen-producing and acetogenic bacteria, methylotrophic methanogens, and hydrogenotrophic methanogens.

[0015] Preferably, the basic culture medium components used for screening composite strains in step S1 include: deionized water, NH4CI (1.0 g), KH2PO4 (0.1 g), MgCI2·6H2O (0.165 g), NaCI (0.8 g), KCI (0.1 g), and CaCI2·2H2O (0.04 g).

[0016] Preferably, the domestication of the strains in step S2 is performed in a simulated real environment.

[0017] Preferably, the biomass selected in step S4 is mostly urban waste and various algae, and the two can be combined in different proportions.

[0018] Preferably, in step S5, a method of hydraulically fracturing the coal seam is adopted.

[0019] Preferably, after adding the fermentation liquid and biomass in step S6, a coal monitoring instrument is installed to monitor the gas production and pH value in the coal seam in real time.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention combines the synergistic effects of hydrolytic bacteria, hydrogen-producing and acetogenic bacteria, methylotrophic methanogens, hydrogenotrophic methanogens, high-temperature-resistant thermophilic bacteria and various types of biomass to effectively improve the efficiency of coal methane production. At the same time, the nutrients in the biomass further promote the chemical reaction process between microorganisms and coal.

[0022] 2. The present invention has carried out multiple precise screenings and enrichments for the desired bacterial strains, and can fully utilize the bacterial strains that are adaptable to the coal mine environment and efficient, significantly improve their efficacy, enhance their ability to transform coal seams, and thus increase the yield of methane.

[0023] 3. The present invention enhances the ability of microorganisms to decompose coal by adding biomass. The biomass source is extensive and economically sustainable. Compared with the traditional method of using culture medium as a nutrient for microbial gasification of coal, the output of methane is increased and the economic cost of microbial gasification of coal seams is reduced.

[0024] 4. The present invention is applicable to various coal seam environmental conditions and can ensure the continuous generation of methane within the room temperature range of 16-36°C. There is no need to perform strain activation operation, which helps to reduce production costs.

[0025] 5. The present invention uses water fracturing coal seam technology to expand the contact surface between coal and microorganisms and improve the fluidity of biomass. Compared with traditional direct microbial injection, its efficiency is significantly improved and the cost is reduced, making it more suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the process of the present invention;

[0027] Figure 2 It is a top view schematic diagram of the implementation of the present invention;

[0028] Figure 3 It is a schematic cross-sectional view of an implementation of the present invention.

[0029] Figure 4 This is a simulation experiment diagram of this embodiment of the present invention.

[0030] In the figure: 1-surface, 2-borehole, 3-rock layer, 4-coal seam, 5-fracturing, 6-mixture of biomass and fermentation bacteria, 7-extraction system, 8-monitoring system. DETAILED DESCRIPTION

[0031] In order to further explain the technical solution of the present invention, it is described in detail below through specific embodiments.

[0032] See also Figure 1-Figure 3 The present invention provides a method for in-situ coal seam gasification by nutrient-enhanced microorganisms, comprising the following steps:

[0033] S1. Screening of bacterial strains: using anaerobic sludge or natural soil to screen out highly efficient composite bacterial strains that can degrade coal in laboratory culture medium;

[0034] S2. Domestication of bacteria: According to the in-situ coal seam environment, with coal and biomass as substrates, the composite bacteria are cultured intensively, and composite fermentation bacteria that are adapted to the in-situ coal seam environment and have significant effects are selected, and gas production data are recorded;

[0035] S3. Biomass screening: Screen out economical and sustainable biomass, mainly organic matter containing carbon and nitrogen;

[0036] S4. Preparation of fermentation liquid: enrich various bacterial species cultured in the laboratory in the culture medium for 4-5 days, maintain the pH value constant at about 7, and prepare fermentation liquid;

[0037] S5, fracturing the coal seam: on the surface 1 of the coal seam to be gasified, drill holes 2 are arranged at a certain distance, and high-pressure water is pressed into the deep-buried coal seam 4 through directional drilling, causing the coal seam to fracture to varying degrees, forming fractures 5;

[0038] S6, adding a mixture 6 of biomass and fermentation bacteria: injecting the fermentation liquid and biomass mixture into the fracture 5 of the coal seam through the borehole 2 by using a pump 6;

[0039] S7. After the injection is completed, a monitoring system 8 is installed to regularly monitor the gas output. If the output decreases, biomass is added to the coal seam to ensure that the nutrients are sufficient and the pH is stable during the fermentation process of the coal seam.

[0040] The composite bacterial species screened in step S1 include: hydrolytic bacteria, hydrogen-producing and acetogenic bacteria, methylotrophic methanogens, and hydrogenotrophic methanogens. The hydrolytic bacteria are responsible for converting coal macromolecules into small molecules as substrates for methanogens, and the hydrogen-producing and acetogenic bacteria, methylotrophic methanogens, and hydrogenotrophic methanogens cooperate to convert small molecular organic matter into methane.

[0041] The components of the basic culture medium (1L) used for screening the composite strains in step S1 include: deionized water, NH4CI (1.0g), KH2PO4 (0.1g), MgCI2·6H2O (0.165g), NaCI (0.8g), KCI (0.1g), and CaCI2·2H2O (0.04g).

[0042] In step S2, the bacterial strains are domesticated in a simulated real environment so that the bacterial colony can better adapt to the coal seam environment.

[0043] The biomass selected in step S4 is mostly urban waste and various algae, which can be combined in different proportions to achieve maximum economic and environmental benefits.

[0044] In step S5, the method of hydraulically fracturing the coal seam is adopted to ensure sufficient contact between the coal seam and the microorganisms.

[0045] Among them, the monitoring system 8 is a coal monitoring instrument, which is used to monitor the gas production, pH value, etc. in the coal seam in real time, so as to replenish the nutrients required by the microorganisms in time and ensure that the microorganisms can perform at their best efficiency.

[0046] The present invention provides simulation tests, such as Figure 4 As shown, the following simulation test is established to simulate the gas production process under the in-situ stress state and the rock formation state. First, a similar model is established. The model specifications are length × width × height = 50 × 50 × 25CM. The following are the components of the model:

[0047] Ⅰ--Inlet / outlet

[0048] Ⅱ--Acrylic sheet, 5cm thickness

[0049] Ⅲ--Gas hose

[0050] IV--Granite slab

[0051] Ⅴ--Sandstone Slab

[0052] VI--Gangue

[0053] Ⅶ--Coal fragments and coal slime mixture

[0054] Ⅷ--Syringe suction port

[0055] Ⅸ--Injection hose

[0056] Ⅹ--Methane Potential Tester

[0057] Coal samples and sandstone were sampled on-site at the 16th coal seam of Yulingxin Coal Mine, and were pre-crushed to less than 200 mesh in the laboratory to make coal slime. The lump coal sample was then mixed with the coal slime to make a coal seam of length × width × height = 40 × 40 × 10CM. During the production process, bacterial liquid and biomass and other materials were pre-buried in the injection hose. At the same time, some cracks were reserved in the coal seam. At the same time, steel columns with the same height or width as the coal seam could be pre-buried in the coal seam as a skeleton. After drying for 24 hours, they were assembled as shown in the figure, and finally sealed on all sides with acrylic panels and sealed at the joints with sealants.

[0058] The experiment was divided into two groups. One group of coal seams was made by adding cyanobacteria biomass to the composition, with a coal-algae ratio of 4:1. The other group was made of pure coal slime and coal blocks to ensure that the quality of the two groups of coal seams was consistent, both 20kg (excluding the quality of the steel column). After injecting 150ml of laboratory enriched bacteria into the two groups, the injection port (Ⅰ) was connected to the methane potential tester (Ⅹ) through the gas hose (Ⅲ), and the seal was done well. The gas produced by the bacterial liquid can be collected into the methane potential tester through the gas hose. The rubber plug was used to seal the air inlet (Ⅷ) and extract the gas. The methane content was detected in the gas chromatograph. 8Mpa stress was applied to the surrounding and upper acrylic plates. Due to the presence of steel columns and coal blocks, the overall shape of the entire coal seam can be well maintained, and the deformation can be avoided while maintaining the existence of some cracks. Finally, the gas production of the experimental group with biomass added reached 5.13ml / g, which was only 1.68ml / g in the pure coal group, and the methane gas production rate reached 205.4%.

[0059] The present invention provides a method of using biomass as a nutritional supplement to enhance the conversion capacity of microorganisms, thereby effectively promoting the production of coalbed methane, improving the recycling of abandoned coal seams, and reducing the cost of microbial gasification of in-situ coal seams. This method mainly utilizes biomass to enhance the conversion capacity of microorganisms on coal seams, collects coal seams left in goafs, and provides a suitable living environment for microorganisms, thereby economically and efficiently producing coalbed methane. Not only can the production of coalbed methane be effectively increased, but abandoned coal seams can also be recycled, and urban waste and algae can also be reused, thereby maximizing the utilization of resources, reducing environmental pollution, and improving resource utilization efficiency.

[0060] The above description is only a preferred example of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for in-situ coal seam gasification by nutrient-enhanced microorganisms, characterized in that: The following steps are involved: S1. Screening of bacterial strains: using anaerobic sludge or natural soil to screen out highly efficient composite bacterial strains that can degrade coal in laboratory culture medium; S2. Domestication of bacteria: According to the in-situ coal seam environment, with coal and biomass as substrates, the composite bacteria are cultured intensively, and composite fermentation bacteria that are adapted to the in-situ coal seam environment and have significant effects are selected, and gas production data are recorded; S3. Biomass screening: Screen out economical and sustainable biomass, mainly organic matter containing carbon and nitrogen; S4. Preparation of fermentation liquid: enrich various bacterial species cultured in the laboratory in the culture medium for 4-5 days, maintain the pH value constant at about 7, and prepare fermentation liquid; S5. Fracturing coal seams: Pressing high-pressure water into deep-buried coal seams through directional drilling, causing the coal seams to fracture to varying degrees; S6. Adding fermentation liquid and biomass: sequentially pressing the fermentation liquid and biomass into the directional drill hole of the coal seam, and sealing the drill hole; S7. Regularly monitor the gas output. If the output decreases, add biomass to the coal seam to ensure sufficient nutrients and stable pH during the fermentation process.

2. The method for in-situ coal seam gasification by nutrient-enhanced microorganisms according to claim 1, characterized in that: The composite bacteria selected in step S1 include: hydrolytic bacteria, hydrogen-producing and acetogenic bacteria, methylotrophic methanogens, and hydrogenotrophic methanogens.

3. The method for in-situ coal seam gasification by nutrient-enhanced microorganisms according to claim 2, characterized in that: The basic culture medium components used for screening the composite strains in step S1 include: deionized water, NH4CI (1.0 g), KH2PO4 (0.1 g), MgCI2·6H2O (0.165 g), NaCI (0.8 g), KCI (0.1 g), and CaCI2·2H2O (0.04 g).

4. The method for in-situ coal seam gasification by nutrient-enhanced microorganisms according to claim 1, characterized in that: In step S2, the strains are domesticated in a simulated real environment.

5. The method for in-situ coal seam gasification by nutrient-enhanced microorganisms according to claim 1, characterized in that: The biomass selected in step S4 is mostly urban waste and various algae, which can be combined in different proportions.

6. The method for in-situ coal seam gasification by nutrient-enhanced microorganisms according to claim 1, characterized in that: In step S5, a method of hydraulically fracturing the coal seam is adopted.

7. The method for in-situ coal seam gasification by nutrient-enhanced microorganisms according to claim 1, characterized in that: After adding the fermentation liquid and biomass in step S6, a coal monitoring instrument is installed to monitor the gas production and pH value in the coal seam in real time.

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