RU2139426C1 - Coal processing method - Google Patents

Abstract

FIELD: coal production industry. SUBSTANCE: method implies injection into bore-holes of methanogenic consortium of microorganisms with cultural medium upon determined interval of time after injection of water. Bore-holes are periodically blown with air during determined period of time. Used in function of methanogenic consortium is collecting microbe culture yielded on coal, and fermented sludge from methane tank. Combination of aforesaid features of method increases emittance of methane due to changing coal properties and widening availability of coal surface for microorganisms. In course of coal processing, microorganisms produce biogas consisting basically of methane and carbon dioxide. EFFECT: higher efficiency. 1 cl, 4 tbl, 1 ex

Description

 The invention relates to mining, and in particular to methods of processing coal and coal waste, the result of which are biogas and a coal-water suspension.

 Known methods of processing coal, solid fuels and carbon-containing materials based on the use of biotechnology (1, 2).

 In the known method (1) for processing a carbon-containing material, a mixture of microorganisms in an aqueous solution of phosphorus salts under aerobic conditions is used. The result of coal processing in this way are finely dispersed coal, humic acids and compounds that activate biochemical processes in the soil. The disadvantage of this method is the practically difficult requirement of constant aeration and mixing during processing, because the latter is carried out in the presence of oxygen.

The closest analogue of this invention in technical essence and the achieved result is a method (2) for processing solid fuel, which includes opening a processing section by wells, injecting a methanogenic consortium of microorganisms with a culture medium, keeping it in the reservoir and extracting coal processing products (dispersed coal and biogas) to surface. The process is conducted under anaerobic conditions, in a closed system. Fermented dung slurry and cattle rumen breeding, as well as activated sludge aeration tank, at an optimal pH of 7.2-7.7, in thermophilic mode (at 50 ^o C) are used as a methanogenic consortium.

 A significant disadvantage of this method is that coal is not processed by microorganisms, because if manure, rumen, and also sludge aeration tank are used as a methanogenic consortium, the organic matter of the latter is the only carbon source for microorganisms and is more accessible than coal, and coal is not processed by microorganisms. In addition, this method is carried out in thermophilic mode. With increasing temperature in the microbiological process, the lag phase (the phase of adaptation of microorganisms to the substrate) in a closed system decreases, but in a coal seam, such a temperature can only be set before the microorganisms are injected, for example, by exposure to water vapor. The process of methanogenesis lasts 40-60 days or more. It is impossible to maintain such a temperature in the formation continuously during the formation of methane. Due to these disadvantages, this method is inefficient for processing coal in the reservoir.

 The basis of the invention is to develop a method for processing coal by injecting into the wells a methanogenic consortium of microorganisms with a culture medium in combination with treating coal with water and blowing wells with air for a predetermined period of time, which contributes to an increase in the formation of methane from coal by its destruction and processing by microorganisms and increases coal processing efficiency.

 The problem is solved by the fact that a method for processing coal is proposed, including opening a processing section by wells, injecting a methanogenic consortium of microorganisms with a culture medium, keeping it in the formation and extracting coal processing products to a surface in which according to the invention water is pumped into wells before injection of a methanogenic consortium of microorganisms with culture medium, which, in turn, is injected into the wells after a predetermined period of time, determined by a decrease in coal strength after water injection, the wells are periodically blown with air for a predetermined period of time, determined by the increase in methane yield, and the accumulative microbial culture isolated on coal and digested sludge digester are used as a methanogenic consortium of microorganisms.

 The ratio of the accumulative microbial culture isolated on coal and the digested sludge methane tank in the methanogenic consortium of microorganisms is, for example, 5:95.

Cumulative microbial culture is obtained in a known manner (3) - the allocation on coal as the only source of carbon and energy after inoculation of the medium with residues of coal and soil. The isolation process was carried out for two years. The culture was reseeded after 6 months, then after 2 months at a temperature of 30 ^o C. The composition of the accumulative microbial culture, isolated on coal, includes microorganisms that carry out hydrolysis, fermentation and methanogenesis, which uses the organic substance of coal as the sole carbon source, processing coal and producing biogas, consisting mainly of methane and carbon dioxide. Fermented sludge methane tank is a source of methanogens, while it itself does not make a significant contribution of methane.

 An analysis of the accumulative microbial culture was carried out by classical taxonomic tests based on the Bergey determinant. The population included strains belonging to the genera Rhodococus sp., Pseudomonas sp., Mycobactenum sp., Sulfate reducers. The species of Clostridium sp. and Bacillus sp.

The number of microorganisms carrying out hydrolysis and growing on the following substrates was: on cellulose 10 ⁶ , on peptone 10 ⁵ , on starch 10 ⁵ . Among the microorganisms that carry out fermentation, glucose-growing ones prevailed, their number was 10 ¹¹ . The number of methanogenic bacteria growing on the following substrates was: on hydrogen 10 ⁶ , on formate 10 ¹¹ , on acetate 10 ¹⁰ , on methanol 10 ⁷ .

In digested sludge, the digesters method was used for tenfold dilutions to determine the number of microorganisms forming acetate, syntrophic microorganisms (cells / ml) growing on ethanol, propionate, butyrate, valerate, and methane forming microorganisms: forming acetate growing on glucose 4 • 10 ⁸ , lactate 6 • 10 ⁸ ; syntrophic microorganisms growing on ethanol 3 • 10 ⁸ , propionate 1 • 10 ⁷ , butyrate 1.5 • 10 ⁷ , valerate 1 • 10 ⁸ ; methanogenic microorganisms growing on hydrogen + CO ₂ 2 • 10 ⁸ , formate 1.3 • 10 ⁸ , acetate 6 • 10 ⁷ .

 The content of the accumulative microbial culture in the methanogenic consortium should be 2-10%. The content of the accumulative culture of less than 2% is insufficient to stimulate the process, the content of the accumulative culture of more than 10% reduces the concentration of methanogens, the main source of which is fermented silt methane tank, in addition, it is not economically feasible.

 The concentration of microorganisms in the mixture injected into the coal seam is equal to their concentration in the sludge of the digester plus the concentration of microorganisms in the accumulation culture diluted 20 times in the preparation of a mixture of the accumulation culture and sludge of the digester, for example, in a ratio of 5:95. This ratio is optimal.

The method was simulated in the laboratory. 150 g of coal was placed in a 500 ml glass column and a methanogenic consortium of microorganisms consisting of an accumulative microbial culture isolated on coal and fermented sludge digester was added at an optimal ratio of 5:95, together with a phosphate-carbonate buffer culture medium, pH 7.0:
The composition of the culture medium - g / l
KH ₂ PO ₄ - 0.025
NH ₄ Cl - 0.05
MgCl ₂ - 0.2
CaCl ₂ - 0.04
The process was carried out under anaerobic conditions, measuring the amount of biogas (methane) and analyzing its composition by chromatographic method. The formation of methane from coals of various grades was determined - from brown to anthracite.

 Pumping water into the well before injecting a methanogenic consortium of microorganisms with the culture medium allows you to change some of the physical and chemical properties of coal and its reactivity when interacting with water. The processing of coal by microorganisms at the stage of changing some of its properties increases the availability of the coal surface for microorganisms due to the wedging effect of the penetrating water molecules and the formation of new surfaces, while the formation of coal solubilized products, which in the subsequent stages of microbiological processing is transformed to biogas (methane), increases. Water can be considered as a background reagent, preparing a coal substrate for bioconversion. The increase in the formation of methane from coals of various grades during their preliminary treatment with water is presented in table 1.

 The time of coal treatment with water before the injection of microorganisms, necessary to increase the methane yield, was determined experimentally. According to the results of experimental studies, three areas of structural changes in the properties of coal after its treatment with water are identified. The first region (1 - 10 days) is characterized by physical hydrophilization of the surface of coal particles, the second (10 - 24 days) - a decrease in coal strength, a decrease in sludge viscosity, an increase in the stability of water-coal suspensions, the third (more than 24 days) - hardening of the coal substance and a decrease in the tendency to the formation of suspensions. The effect of coal treatment with water on methane yield (depending on time) before it was treated with microorganisms was experimentally investigated. For the coals studied by this method, the results are shown in table 2.

 From table 2 it follows that the processing of coal by microorganisms in 10-24 days (which corresponds to the second region of the structural transformations of coal) after preliminary treatment with water leads to an increase in methane yield. Based on the results of these studies, the time parameter necessary to reduce the strength of coal and increase methane yield from 10 to 24 days is determined.

 The composition of the accumulative microbial culture isolated on coal includes facultative anaerobes capable of life under aerobic conditions. The process of methanogenesis is multi-stage, its initial stage - solubilization of coal can be carried out under aerobic conditions. The formation of methane from coal was determined using daily blowing of the column with air for 3–4 hours (Table 3), the methane yield in the aerobic-anaerobic process increased compared to the anaerobic one. Purge time was determined experimentally. To increase the methane yield, 3 to 4 hours is enough, with a longer air purge, the anaerobic conditions are so violated that it is then difficult to recover in the subsequent stages of methanogenesis, requiring anaerobic conditions. The formation of methane from coal grade "GZ" in anaerobic and aerobic-anaerobic processes are presented in table 3.

 In a laboratory experiment, the destruction of coal by microorganisms led to the formation of 25-30% by weight of a pulverulent fraction with a particle size <0.07 mm from the initial coals of fineness -2.5 + 1.6 mm. X-ray analysis showed changes in the structure and structure of the resulting coal particles, which can only be a consequence of biochemical transformations, and not the result of physical destruction during swelling in the medium. The surfactants released by microorganisms, biotensides, stabilize the coal-water suspension. In the process of bioprocessing, sulfur is removed from coal and ash content is reduced (see table. 4).

 The method is as follows. In the coal seam, drilling wells and wells for pumping processed products are drilled from the surface. The distance between the wells is determined depending on the conditions of occurrence, the permeability of the formation, technical characteristics of coal. The supply wells are drilled to a depth below 0.3 m from the top of the formation (m is the thickness of the formation), and the pumped wells are drilled 0.3 m from the bottom of the formation. In the lower part of the pumping well arrange a chamber - a collection of products. Hydraulic fracturing is performed through the supply wells by pumping water at a pressure of 1.5 - 2.5 MPa (for soft coals) and 8 - 10 MPa (for hard coals). Water is supplied until it appears in the collection chambers. A methanogenic consortium of microorganisms, consisting of an accumulated microbial culture separated from coal, comprising from 2 to 10%, and digested sludge methane tank (optimal ratio 5: 95), is pumped into the reservoir together with the culture medium 10-24 days after the coal is treated with water.

 Every day for 3-4 hours, the wells are blown with air at a pressure of 0.15-0.2 MPa through the pumping wells. The biogas (methane) formed as a result of processing, dispersed coal and its products from the collection chambers are extracted to the surface using pumps.

 The use of the invention will improve the efficiency of coal processing.

Sources of information
1. USSR patent N 1816394 A 3, CL. E 21 B 43/295.

 2. USSR patent N 1814686 A 3, CL. E 21 B 43/295, 1993 - prototype.

 3. Namsaraev BB, Dulov LE, Alexandrov IV, Terekhova S.E. and S. Shumkov. Collection "Introduction of microorganisms into the environment." M., RAS, 1994, pp. 71 - 72.

Claims (2)

 1. A method of processing coal, including opening the processing section by wells, injecting a methanogenic consortium of microorganisms with a culture medium into them, keeping it in the formation and extracting coal processing products to the surface, characterized in that water is pumped into the wells before injecting a methanogenic consortium of microorganisms with a culture medium and a methanogenic consortium of microorganisms with a culture medium is injected into the wells after a predetermined period of time, determined by the decrease in strength looking after water injection, the wells are periodically blown with air for a predetermined period of time, determined by the increase in methane yield, while an accumulative microbial culture isolated on coal and digested sludge digester are used as a methanogenic consortium of microorganisms.  2. The method according to claim 1, characterized in that the ratio of the accumulative microbial culture isolated on coal and fermented sludge methane tank in a methanogenic consortium of microorganisms is, for example, 5: 95.

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