Protective layer pressure relief and permeability increase method for close-range thin coal seam fluidized mining

Abstract

The invention discloses a close-range thin coal seam fluidized mining protective layer pressure relief and permeability increasing method, and relates to the technical field of coal mining. The thin coal seam coal body is ignited through the ignition circuit with the protection pipe; oxygen is input through the gas inlet pipe, and the gas inlet amount is regulated and controlled through the oxygen concentration sensor, so that the coal body is subjected to redox reaction to generate carbon monoxide and hydrogen; combustible gas is extracted and monitored by using an extraction pipe, an extraction control valve and a generated gas detection end; a cavity formed after the reaction of the thin coal seam provides a pressure relief and permeability increasing space for the lower thick coal seam. The pressure relief and permeability increase method for the close-range thin coal seam fluidized mining protective layer has the advantages of being safe and controllable in operation, high in resource utilization rate, remarkable in pressure relief effect and the like, and is suitable for efficient utilization of the close-range thin coal seam and pretreatment before mining of a thick coal seam.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a method for depressurizing and enhancing permeability of protective layers in fluidized bed mining of thin coal seams at close range. Background Technology

[0002] In the coal mining industry, the mining of thin coal seams in close proximity has always faced the problem of poor economic efficiency. Traditional thin coal seam mining requires a large investment in equipment for shaft and tunnel layout and coal seam recovery, but its resource recovery rate is low and the mining cost is high, resulting in most thin coal seams in close proximity being regarded as difficult-to-mine resources and left idle.

[0003] Before mining, the lower thick coal seam needs to undergo depressurization and permeability enhancement treatment to reduce the risk of gas outbursts. Traditional methods mainly involve mining the protective layer or hydraulic fracturing. However, traditional protective layer mining also faces the cost problem of mining thin coal seams, while hydraulic fracturing is greatly limited by geological conditions and is prone to damaging the coal seam structure, resulting in unstable gas extraction efficiency.

[0004] Current thin coal seam utilization technologies have not yet formed an integrated solution of "mining + utilization + decompression": the energy of thin coal seams is not effectively recovered, and they cannot directly support the decompression and permeability enhancement of the underlying thick coal seams. Therefore, how to achieve low-cost and efficient utilization of nearby thin coal seams, while creating favorable conditions for decompression and permeability enhancement of the underlying thick coal seams, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for decompression and permeability enhancement of protective layers in fluidized bed mining of thin coal seams in close proximity, in order to solve the problems of high cost and poor economic efficiency in existing thin coal seam mining and low decompression and permeability enhancement efficiency in thick coal seams, and to achieve the integrated goal of fluidized bed mining and utilization of thin coal seams and decompression and permeability enhancement of thick coal seams.

[0006] To achieve the above objectives, the present invention provides a method for depressurizing and enhancing permeability of the protective layer in close-range thin coal seam fluidized mining, comprising the following steps: S1. Excavate a roadway in the rock strata between a thin coal seam and a thick coal seam in close proximity, and install an air intake pipe and an air extraction pipe in the roadway. The air intake pipe is connected to the gas transmission motor, and the air extraction pipe is connected to the air extraction control valve and the air extraction motor in sequence. Set up a support structure in the corresponding area of ​​the thin coal seam. The support structure does not obstruct the gas flow. S2. Arrange ignition circuits within the thin coal seam, and connect ignition switches to control the ignition timing. S3. The ignition switch starts the ignition, igniting the coal in the thin coal seam; oxygen is supplied to the thin coal seam area through the gas supply motor and the air intake of the gas supply motor is adjusted. S4. Gas generated by the reaction of thin coal seam is extracted through the extraction pipe by the extraction motor, and the gas flow rate of the extraction pipe is adjusted by the extraction control valve. S5. After continuous combustion, thin coal seams form cavities. These cavities provide pressure relief and permeability enhancement space for the thicker coal seams below, enabling gas extraction from the thicker coal seams.

[0007] Preferably, the support structure in S1 is a mesh structure.

[0008] Preferably, the ignition circuit in S2 is covered with a protective sleeve, and the ignition switch is located outside the protective sleeve.

[0009] Preferably, an oxygen concentration sensor is installed in the thin coal seam area in S3. The air intake of the gas conveying motor is adjusted by the oxygen concentration sensor. When the oxygen volume concentration in the reaction area of ​​the thin coal seam is lower than a preset threshold, the air intake of the gas conveying motor is increased; when the oxygen concentration is higher than the preset threshold, the air intake of the gas conveying motor is decreased.

[0010] Preferably, the coal in S3 undergoes the following reactions: C + O2 = CO2, CO + C = 2CO, H2O + C = H2 + CO.

[0011] Preferably, the purity of the oxygen input in S3 is not less than 90%.

[0012] Preferably, in S4, one end of the extraction pipe is connected to the extraction motor, and the other end is connected to the control valve. A sampling pipe is provided between the control valve and the support structure. The end of the sampling pipe is connected to the gas detection end, which is located outside the extraction pipe.

[0013] Preferably, S4 uses the sampling tube and gas detection end to monitor the concentration of carbon monoxide and hydrogen in the extracted gas in real time. If the concentration is lower than the preset utilization threshold, the opening of the gas extraction control valve is increased; if the concentration is higher than the preset safety threshold, the opening of the gas extraction control valve is decreased.

[0014] Preferably, when carrying out gas extraction work in thick coal seams in S5, gas boreholes are arranged in the thick coal seams, and the area covered by the gas extraction boreholes corresponds to the depressurization range of the cavity area after fluidized mining.

[0015] Therefore, the present invention adopts the above-mentioned method for depressurization and permeability enhancement of protective layer in fluidized mining of thin coal seams in close proximity. By excavating roadways in the rock strata between the thin coal seam in close proximity and the thick coal seam below, and arranging air intake pipes, air extraction pipes, support structures and monitoring equipment, the integrated operation of fluidized mining of thin coal seams and depressurization and permeability enhancement of thick coal seams is realized.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an embodiment of the method for depressurizing and enhancing permeability of a protective layer in fluidized coal seam mining at close range according to the present invention; Figure 2 This is a detailed diagram of the equipment layout for the present invention; Figure 3 This is an application effect diagram of the present invention;

[0018] Figure Labels 1. Lower thick coal seam; 2. Roadway; 3. Air intake pipe; 4. Closely spaced thin coal seam; 5. Rock strata; 6. Extraction pipe; 7. Gas transmission motor; 8. Oxygen concentration sensor; 9. Protective pipe; 10. Ignition switch; 11. Support structure; 12. Sampling pipe; 13. Gas detection end; 14. Control valve; 15. Extraction motor; 16. Void projection area. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0021] Example Please see Figures 1-3 This invention provides a method for depressurizing and enhancing the permeability of a protective layer in fluidized coal seam mining at close range, comprising the following steps: S1. A roadway 2 is excavated in the rock strata 5 between the thin coal seam 4 and the thick coal seam 1 below for equipment installation and operation; an air intake pipe 3 and an air extraction pipe 6 are laid in the roadway. One end of the air intake pipe 3 extends to the reaction area of ​​the thin coal seam, and the other end is connected to the gas supply motor 7, which is used to supply oxygen required for the reaction to the thin coal seam; one end of the air extraction pipe 6 extends to the other side of the reaction area of ​​the thin coal seam, and the other end is connected in sequence to the air extraction control valve 14 and the air extraction motor 15, which are used to extract the carbon monoxide and hydrogen generated by the reaction.

[0022] Support structures 11 are arranged in the roadway 2 corresponding to the thin coal seam and around the coal seam. The support structure 11 is a mesh structure, and its mesh size does not affect the gas flow. It is used to maintain the stability of the cavity connection and prevent damage during the reaction process.

[0023] S2. An ignition circuit is arranged along the strike or dip within the thin coal seam. The ignition circuit uses high-temperature resistant conductors and is externally sheathed with a protective conduit 9. The protective conduit 9 is made of flame-retardant material and its length covers the entire ignition circuit to protect it from the high temperature of the coal seam reaction, coal slag, and water vapor. One end of the ignition circuit is connected to an ignition switch 10, which controls the ignition timing to ensure the safety of the reaction initiation.

[0024] S3. Ignition is started by ignition switch 10 to ignite the coal in the thin coal seam; the operation of gas supply motor 7 is maintained to continuously supply oxygen to the reaction area of ​​the thin coal seam through air inlet pipe 3, with a purity of not less than 90%, so as to ensure that the coal reacts fully.

[0025] An oxygen concentration sensor 8, installed in the reaction zone of the thin coal seam, monitors the oxygen volume concentration in the reaction zone in real time. When the oxygen concentration is below 15%, the air intake of the gas conveying motor 7 is increased; when the oxygen concentration is above 20%, the air intake of the gas conveying motor 7 is decreased, so that the coal body undergoes the following reaction under oxygen regulation: 1. Preliminary oxidation reaction: C + O₂ = CO₂; 2. Secondary reduction reaction: CO2 + C = 2CO; 3. Water vapor reaction: H2O + C = H2 + CO.

[0026] By adjusting the oxygen concentration, the reaction is ensured to primarily produce carbon monoxide and hydrogen, thereby improving the efficiency of combustible gas production.

[0027] S4. Start the gas extraction motor 15 and extract carbon monoxide and hydrogen generated by the reaction of the thin coal seam through the gas extraction pipe 6; set the sampling pipe 12 at the front end of the gas extraction pipe 6, and connect the sampling pipe 12 to the generated gas detection end 13 to monitor the volume concentration of carbon monoxide and hydrogen in the extracted gas in real time.

[0028] Adjust the gas extraction control valve 14 according to the monitoring results: when the concentration of carbon monoxide and hydrogen is below 30%, increase the opening of the gas extraction control valve 14 to increase the gas extraction rate; when the concentration is above 70%, decrease the opening of the gas extraction control valve 14 to ensure safe gas extraction.

[0029] S5. During the continuous reaction process of the thin coal seam, the coal body is gradually consumed and cavities are formed. After the reaction of the thin coal seam is completed, gas intake and extraction are stopped. The cavities formed at this time serve as pressure relief spaces for the protective layer, causing the lower thick coal seam to develop fractures due to the release of the load from the upper layer. Gas drainage pipes are installed in the thick coal seam, with the gas intake end of the gas drainage pipe corresponding to the cavity projection area 16. The pressure relief effect formed by the cavities is used to improve the gas drainage efficiency of the thick coal seam, laying the foundation for the safe mining of the subsequent thick coal seam.

[0030] Therefore, this invention employs the aforementioned method for pressure relief and permeability enhancement in the protective layer of fluidized bed mining of thin coal seams in close proximity. By excavating roadways in the rock strata between the thin coal seam and the underlying thick coal seam, and arranging air intake pipes, extraction pipes, support structures, and monitoring equipment, it achieves integrated operation of fluidized bed mining of thin coal seams and pressure relief and permeability enhancement of thick coal seams. This method offers advantages such as safe and controllable operation, high resource utilization, and significant pressure relief effect, making it suitable for the efficient utilization of thin coal seams in close proximity and for pretreatment before mining thick coal seams.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for depressurizing and enhancing permeability of a protective layer in fluidized bed mining of thin coal seams at close range, characterized in that, Includes the following steps: S1. Excavate a roadway in the rock strata between a thin coal seam and a thick coal seam in close proximity, and install an air intake pipe and an air extraction pipe in the roadway. The air intake pipe is connected to the gas transmission motor, and the air extraction pipe is connected to the air extraction control valve and the air extraction motor in sequence. Set up a support structure in the corresponding area of ​​the thin coal seam. The support structure does not obstruct the gas flow. S2. Arrange ignition circuits within the thin coal seam, and connect ignition switches to control the ignition timing. S3. The ignition switch starts the ignition, igniting the coal in the thin coal seam; oxygen is supplied to the thin coal seam area through the gas supply motor and the air intake of the gas supply motor is adjusted. S4. Gas generated by the reaction of thin coal seam is extracted through the extraction pipe by the extraction motor, and the gas flow rate of the extraction pipe is adjusted by the extraction control valve. S5. After continuous combustion, thin coal seams form cavities. These cavities provide pressure relief and permeability enhancement space for the thicker coal seams below, enabling gas extraction from the thicker coal seams.

2. The method for depressurizing and enhancing permeability of the protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 1, is characterized in that: The support structure in S1 is a mesh structure.

3. The method for depressurizing and enhancing permeability of the protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 2, is characterized in that: In S2, the ignition circuit is externally sheathed, and the ignition switch is located outside the sheath.

4. The method for depressurizing and enhancing permeability of the protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 3, is characterized in that: An oxygen concentration sensor is installed in the thin coal seam area of ​​S3. The air intake of the gas conveying motor is adjusted by the oxygen concentration sensor. When the oxygen volume concentration in the reaction area of ​​the thin coal seam is lower than the preset threshold, the air intake of the gas conveying motor is increased; when the oxygen concentration is higher than the preset threshold, the air intake of the gas conveying motor is decreased.

5. The method for depressurization and permeability enhancement of the protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 4, is characterized in that... The following reactions occur in the coal in S3: C + O2 = CO2, CO + C = 2CO, H2O + C = H2 + CO.

6. The method for depressurization and permeability enhancement of the protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 5, is characterized in that: The purity of the oxygen input in S3 is no less than 90%.

7. The method for depressurizing and enhancing permeability of the protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 6, is characterized in that: In S4, one end of the extraction pipe is connected to the extraction motor, and the other end is connected to the control valve. A sampling pipe is installed between the control valve and the support structure. The end of the sampling pipe is connected to the gas detection end, which is located outside the extraction pipe.

8. The method for depressurizing and enhancing permeability of the protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 7, is characterized in that: S4 uses the sampling tube and gas detection end to monitor the concentration of carbon monoxide and hydrogen in the extracted gas in real time. If the concentration is lower than the preset utilization threshold, the opening of the gas extraction control valve is increased; if the concentration is higher than the preset safety threshold, the opening of the gas extraction control valve is decreased.

9. A method for depressurizing and enhancing permeability of a protective layer in fluidized bed mining of thin coal seams at close range, as described in claim 8, is characterized in that: When carrying out gas extraction work in thick coal seams in S5, gas boreholes are arranged in the thick coal seams, and the area covered by the gas extraction boreholes corresponds to the depressurization range of the void area after fluidized mining.

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