Fire preventing and extinguishing method and device for coal mine

Abstract

The invention belongs to the field of coal mine fire prevention and extinguishing safety, and particularly relates to a coal mine fire prevention and extinguishing method and device. Gas obtained after gas is extracted and combusted is adsorbed, enriched or captured, the purity of the gas reaches 50% or above, the captured gas enters a supercharging device, and one path of supercharged CO2 gas can be directly injected into a coal mine goaf through a gas injection pipeline; after the flue gas is injected into the goaf of the coal mine, the concentration of carbon dioxide, oxygen and methane is monitored through a gas concentration monitoring system, and gas injection is stopped when the concentration of carbon dioxide in the goaf reaches 50%. According to the invention, carbon dioxide gas in flue gas is injected into the goaf through the trapping system, and the CO2 gas is sealed by utilizing the adsorption characteristic of coal rock in the goaf to the CO2 gas, so that the CO2 trapping and separating cost can be reduced, the spontaneous combustion of residual coal in the goaf can be prevented and controlled, the fire prevention and extinguishing effects are achieved, and the safety of the coal mine goaf is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of coal mine fire prevention and control safety, and particularly relates to a coal mine fire prevention and control method and device. Background Art

[0002] The gob area of a coal mine refers to the underground cavities or voids left after coal or coal gangue extraction. Such cavities often pose safety hazards during the production process. Due to the residual floating coal during the mining process, it provides potential fuel for coal mine spontaneous combustion, which greatly threatens the production and safety of coal mines. According to statistics, in state-owned key coal mines in China, coal mine spontaneous combustion caused by the gob area accounts for 60% of spontaneous combustion fires, and most of these fires are caused by poor ventilation, that is, air leakage. The prevention and control of gob area spontaneous combustion are important links in coal mine fire prevention work, which is directly related to the safe operation and economic benefits of coal mines. Effective prevention measures can significantly reduce the occurrence of coal mine fires, ensure the safety of miners' lives, and the stable development of the entire industry.

[0003] Coal seams are a special type of porous rock material that has a strong adsorption capacity for CO2 and can achieve the purpose of long-term CO2 sequestration on a geological time scale. Therefore, it has become a potential geological body for CO2 sequestration.

[0004] CN103061795A is a coal mine fire prevention and control method using flue gas from a pithead power plant, characterized in that: flue gas is taken from the outlet of the desulfurization tower (1) of the coal mine pithead power plant. After the flue gas undergoes denitrification, dehumidification, cooling, and dust removal treatment in the flue gas pretreatment system (2), it enters the transportation and flue gas injection system. After being pressurized by the flue gas injection system, the flue gas is injected into the mine; the method of burying pipes for gas injection is adopted. Two injection pipelines (10) are buried in the intake airway of the fully mechanized caving face. One of the injection pipelines is buried to the middle of the open-off cut, with 3 injection holes opened, the pipe orifice facing upwards, 2m away from the floor, and the other injection pipeline is buried in the oxidation zone, with 3 injection holes opened; the gas injection method adopts continuous gas injection, that is, injecting gas for 24 hours every day, and stopping gas injection when the CO2 concentration in the return airway reaches more than 1.5%. CN103061795A uses the fact that the CO2 concentration in the flue gas from the pithead power plant is relatively low, and there are also certain polluting gases such as nitrogen oxides and sulfur oxides in the gas, which are likely to cause secondary pollution to the bottom of the mine, and stops gas injection when the CO2 concentration reaches more than 1.5%. This fire extinguishing method is not applicable to the gob area of coal mines and has limited fire extinguishing effect.

[0005] CN116877184A discloses a goaf carbon dioxide mineralization grouting filling fire prevention and extinguishing system, including a filling system and a trusteeship grouting system. It is characterized in that the filling system includes a slurry conveying pipeline, a filling driving device and a slurry filling pipeline. The filling system is connected to the trusteeship grouting system through the slurry filling pipeline. The trusteeship grouting system includes a carbon dioxide conveying pipeline and a goaf embedded pipe, and the carbon dioxide conveying pipeline is connected to the goaf embedded pipe. It is necessary to lay a slurry filling pipeline in the goaf underground, and it is also necessary to transport CO2 to the goaf through the embedded pipeline. The process is cumbersome, the cost is relatively high, and it is difficult to implement. Summary of the Invention

[0006] The purpose of the present invention is to provide a coal mine fire prevention and extinguishing method and device with reasonable design and reliable performance.

[0007] Coal seams are a special porous rock material, which has a strong adsorption capacity for CO2 and can achieve the purpose of long-term CO2 sequestration on the geological time scale. Therefore, it has become a potential geological body for CO2 sequestration.

[0008] Combining carbon capture and storage with coal seams, the gas after the combustion of extracted gas mainly composed of CO2 is treated and then injected into the goaf. Utilizing the adsorption characteristics of coal and rock in the goaf for CO2 gas, the sequestration of CO2 gas can be realized. It can not only reduce the cost of CO2 capture and separation, but also prevent the spontaneous combustion of residual coal in the goaf and play a role in fire prevention and extinguishing.

[0009] The present invention is realized through the following technical solutions: 1) The gas after gas combustion, including nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane, carbon monoxide, etc., enters the CO2 enrichment or capture device. The flue gas remaining after CO2 enrichment or capture is discharged through the remaining gas discharge pipeline; 2) After the CO2 gas is enriched or captured by physical adsorption or chemical adsorption, its purity reaches more than 50%, preferably more than 60%, and more preferably more than 80%. The gas components mainly include carbon dioxide, nitrogen, and a small amount of oxygen. The captured gas enters the pressurization device. The pressurized CO2 gas can be directly injected into the coal mine goaf through the gas injection pipeline in one way; in the other way, it enters the CO2 storage device, is transformed into liquid CO2 to realize the temporary storage of CO2, and then enters the conversion device to realize the conversion of CO2 from gaseous state to liquid state. The converted CO2 gas is then injected into the coal mine goaf through the gas injection pipeline. The switching of all gas paths can be adjusted through gas shut-off valves, and the injected flue gas volume can be adjusted and controlled through the booster and the CO2 storage device. If there is a temporary failure in the equipment, CO2 can be discharged through the temporary gas discharge channel; 3) After the flue gas is injected into the goaf of the coal mine, the concentrations of carbon dioxide, oxygen, and methane are monitored through a gas concentration monitoring system. When the carbon dioxide concentration in the goaf reaches 50%, the gas injection stops. As time goes by, the residual coal in the goaf gradually adsorbs the injected carbon dioxide. After the carbon dioxide concentration in the goaf decreases, gas injection is continued until the carbon dioxide concentration reaches 50% and then the gas injection stops. The device used in the above method includes: a flue gas system, a CO2 enrichment or capture system, a CO2 storage system, a CO2 injection system, and a gas concentration monitoring system; The flue gas system includes the flue gas after gas - fired power generation, the remaining flue gas after CO2 enrichment or capture, and the temporarily discharged CO2 flue gas. The flue gas is collected from the chimney or flue. The components of the flue gas after gas - fired power generation include nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane and carbon monoxide. The remaining flue gas after CO2 enrichment or capture includes nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane and carbon monoxide. The temporarily discharged CO2 flue gas mainly contains carbon dioxide.

[0010] The CO2 enrichment or capture system is a CO2 physical adsorption device or a chemical adsorption device. For the CO2 physical adsorption device, it includes a pressure swing adsorption bed and physical adsorption components. When carbon dioxide gas passes through the adsorption bed, due to the high specific surface area and pore structure of the physical adsorbent, and after pressurization to a certain pressure, the carbon dioxide gas can be adsorbed by the pores on the surface of the adsorbent. During the regeneration process, the adsorbed carbon dioxide gas in the adsorption bed is discharged by depressurization, thus obtaining pure carbon dioxide gas. The physical adsorbents include activated carbon, molecular sieve, metal - organic framework materials (MOF), and solid amine adsorbents, etc. For the CO2 chemical adsorption device, it includes an adsorbent bed, a heater, a cooler, and a regenerator, etc. The adsorbent bed is filled with a liquid - phase adsorbent. The chemical adsorbent includes organic amines or alkaline substances. When carbon dioxide gas passes through the adsorbent bed, carbon dioxide reacts chemically with the organic amines or alkaline substances in the adsorbent and is captured. During the regeneration process, the heater heats the adsorbed carbon dioxide in the adsorption bed to release it, and after purification through the cooler, pure carbon dioxide gas is obtained.

[0011] The CO2 storage system includes a pressurizing device, a CO2 storage device, and a conversion device. The pressurizing device can increase the pressure of CO2, reduce the gas volume, and facilitate storage and transportation. The pressurizing device can be a centrifugal compressor or a pneumatic booster pump, etc. The CO2 storage device can temporarily store CO2, serving as a temporary storage for further utilization of CO2 and subsequent sequestration. The CO2 storage device can be a steel storage tank, which can withstand the pressure when CO2 is compressed from gaseous to liquid state. The conversion device can play a role in regulating pressure, and can convert high-pressure or even liquid CO2 into lower-pressure gaseous CO2. The conversion device can be a pressure reducing valve, a throttle valve, or an expander, etc., and connecting pipelines.

[0012] The CO2 injection system includes a mined-out area of a coal mine and a gas injection pipeline. Preferably, the geological structure of the coal mine shaft from top to bottom includes the ground, an aquiferous stratum, an aquifuge stratum, remaining coal seams, and a rock stratum. The bottom of the mined-out area of the coal mine is located in the remaining coal seams, the higher side of the top is located in the aquifuge stratum, and the lower side of the top is located in the remaining coal seams. One end of the gas injection pipeline is connected to the conversion device or the pressurizing device, and the other end is connected to the port of the mined-out area of the coal mine.

[0013] The gas concentration monitoring system includes a carbon dioxide concentration monitoring instrument, an oxygen concentration monitor, and a methane concentration monitoring instrument. When the injected carbon dioxide, oxygen, or methane exceeds a certain concentration, an alarm is triggered, and at the same time, the injection or stop of CO2 is controlled through the PLC system.

[0014] The present invention has the following advantages compared with the existing technologies: ①It solves the problem of carbon dioxide emissions after gas combustion. Through the capture system, carbon dioxide in the flue gas is enriched or captured, and finally carbon dioxide sequestration is achieved. Almost all harmful gases are not discharged, which has great environmental and social benefits. ②The gas after burning the extracted gas mainly composed of CO2 is injected into the gob area. By utilizing the adsorption characteristics of coal and rock in the gob area for CO2 gas, the sequestration of CO2 gas can be achieved. This can not only reduce the costs of CO2 capture and separation, but also prevent the spontaneous combustion of residual coal in the gob area at the same time, playing a role in fire prevention and ensuring the safety of the coal mine gob area. ③The overall structure of the system is simple and easy to implement. By using the carbon dioxide generated after gas combustion and adding CO2 capture devices and pressurized storage devices, etc., which are all conventional equipment, the process is simple, and the investment and operation and maintenance costs are relatively low. ④The concentrations of CO2 and methane can be monitored in real time. Through the concentration sensors and the PLC program control system, the real-time monitoring of the concentrations of CO2 and methane can be achieved to further optimize the injected flue gas ratio in real time and ensure that the gas in the coal mine gob area is within the safe concentration range. ⑤The multi-faceted utilization of CO2 can be realized. By using the carbon dioxide storage device, the multi-faceted utilization of CO2 can be realized in addition to sequestration in the gob area, such as synthesizing chemicals, artificial photosynthesis, mineralization, calcification, alkylation, etc. ⑥It can be widely promoted and applied on a large scale. The overall concept of using gas and then recycling and sequestering its gas for fire prevention in the mining area has relatively low investment and operation costs and has the potential for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the present invention.

[0016] In the figure: 1 - chimney; 2 - carbon dioxide enrichment or capture system; 3 - pressurization device (Ⅰ); 4 - pressurization device (Ⅱ); 5 - carbon dioxide storage device; 6 - conversion device; 7 - coal mine gob area; 8 - gas cut-off valve; 9 - gas concentration monitoring system; 10 - gas injection pipeline. DETAILED DESCRIPTION OF THE INVENTION

[0017] The method of the present invention specifically includes the following steps: 1) The gas after gas combustion, containing nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane, carbon monoxide, etc., enters the CO2 enrichment or capture device 2, and the captured gas is discharged through the remaining gas discharge pipeline.

[0018] 2) After the CO2 gas is enriched or captured through physical adsorption or chemical adsorption, its purity reaches over 50%, preferably over 60%, more preferably over 80%. The gas components mainly include carbon dioxide, nitrogen, and a small amount of oxygen. The captured gas enters the pressurization device (I) 3 or the pressurization device (II) 4. The pressurized CO2 gas can be directly injected into the goaf 7 of the coal mine through the gas injection pipeline 10. Another path enters the CO2 storage device 5, is transformed into liquid CO2 to achieve the temporary storage of CO2, and then enters the conversion device 6 to realize the conversion of CO2 from gaseous to liquid. The converted CO2 gas is then injected into the goaf 7 of the coal mine through the gas injection pipeline 10. The switching of all gas paths can be adjusted through the gas shut-off valve 8. The injected flue gas volume can be adjusted and controlled through the pressurization device and the CO2 storage device. If there is a temporary fault in the equipment, CO2 can be discharged through the temporary gas discharge channel.

[0019] 3) After the flue gas is injected into the goaf 7 of the coal mine, the concentrations of carbon dioxide, oxygen, and methane are monitored through the gas concentration monitoring system 9. When the carbon dioxide concentration in the goaf reaches 50%, the gas injection stops. As time goes by, the residual coal in the goaf gradually adsorbs the injected carbon dioxide. After the carbon dioxide concentration in the goaf decreases, additional gas is injected until the carbon dioxide concentration reaches 50% and then the gas injection stops.

[0020] The device used in the above method includes: a flue gas system, a CO2 enrichment or capture system, a CO2 storage system, a CO2 injection system, and a gas concentration monitoring system.

[0021] The flue gas system includes the flue gas after gas power generation combustion, the remaining flue gas after CO2 enrichment or capture, and the flue gas for temporary CO2 discharge. The flue gas is collected from the chimney 1 or the flue. The components of the flue gas after gas power generation combustion include nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane and carbon monoxide. The remaining flue gas after CO2 enrichment or capture includes nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane and carbon monoxide. The flue gas for temporary CO2 discharge mainly contains carbon dioxide.

[0022] The CO2 enrichment or capture system 2 is a CO2 physical adsorption device or a chemical adsorption device. The CO2 physical adsorption device includes components such as a pressure swing adsorption bed and a physical adsorbent. When carbon dioxide gas passes through the adsorption bed, due to the high specific surface area and pore structure of the adsorbent, and after pressurizing to a certain pressure, the carbon dioxide gas can be adsorbed by the pores on the surface of the adsorbent. During the regeneration process, the adsorbed carbon dioxide gas in the adsorption bed is discharged by depressurization, thereby obtaining pure carbon dioxide gas. The physical adsorbent includes activated carbon, molecular sieve, molecular sieve, MOF (metal-organic framework material), and solid amine adsorbent, etc.; The CO2 chemical adsorption device includes parts such as an adsorbent bed, a heater, a cooler, and a regenerator. The adsorbent bed is filled with a liquid-phase adsorbent; The chemical adsorbent includes organic amines or alkaline substances. When carbon dioxide gas passes through the adsorbent bed, carbon dioxide reacts chemically with the organic amines or alkaline substances in the adsorbent and is captured. During the regeneration process, the heater heats the adsorbed carbon dioxide in the adsorption bed to release it, and after being cooled and purified by the cooler, pure carbon dioxide gas is obtained.

[0023] The CO2 storage system includes a pressurizing device (Ⅰ) 3, a pressurizing device (Ⅱ) 4, a CO2 storage device 5, and a conversion device 6. The pressurizing device can increase the pressure of CO2 and reduce the gas volume, facilitating storage and transportation. The pressurizing device can be a centrifugal compressor or a pneumatic booster pump, etc. The CO2 storage device 5 can temporarily store CO2, serving as a temporary storage for further utilization of CO2 and subsequent sequestration. The CO2 storage device 5 can be a steel storage tank, which can withstand the pressure when CO2 is compressed from gaseous to liquid state. The conversion device 5 can play a role in regulating pressure, and can convert high-pressure or even liquid CO2 into lower-pressure gaseous CO2. The conversion device 5 can be a pressure reducing valve, a throttle valve, or an expander, etc., and connecting pipelines.

[0024] The CO2 injection system includes a goaf 7 of a coal mine and a gas injection pipeline 10. Preferably, the geological structure of the coal mine shaft from top to bottom includes the ground, an aquiferous stratum, an aquitard stratum, remaining coal seams, and a rock stratum. The bottom of the goaf of the coal mine is located in the remaining coal seam, the higher side of the top is located in the aquitard stratum, and the lower side of the top is located in the remaining coal seam. One end of the gas injection pipeline 10 is connected to the conversion device 6 or the pressurizing device, and the other end is connected to the port of the goaf 7 of the coal mine.

[0025] The gas concentration monitoring system includes a carbon dioxide concentration monitoring instrument, an oxygen concentration monitor, and a methane concentration monitoring instrument. When the injected carbon dioxide, oxygen, or methane exceeds a certain concentration, an alarm is triggered, and at the same time, the injection or stop of CO2 is controlled through the PLC system.

Claims

1. A method for preventing and extinguishing fires in coal mines, characterized in that: 1) The gas after gas combustion, containing nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane, carbon monoxide, etc., enters the CO2 enrichment or capture system. The flue gas remaining after CO2 enrichment or capture is discharged through the remaining gas discharge pipeline; 2) After the CO2 gas is enriched or captured by physical adsorption or chemical adsorption, its purity reaches more than 50%. The gas components mainly include carbon dioxide, nitrogen, and a small amount of oxygen. The captured gas enters the pressurization device. The pressurized CO2 gas can be directly injected into the gob area of the coal mine through the gas injection pipeline in one way, and enters the CO2 storage device in the other way, where it is transformed into liquid CO2 to achieve the temporary storage of CO2. Then it enters the conversion device to achieve the conversion of CO2 from gaseous to liquid state. The converted CO2 gas is then injected into the gob area of the coal mine through the gas injection pipeline. The switching of all gas paths can be adjusted by the gas shut-off valve, and the injected flue gas volume can be adjusted and controlled by the booster and the CO2 storage device. If there is a temporary failure in the equipment, CO2 can be discharged through the temporary gas discharge channel; 3) After the flue gas is injected into the gob area of the coal mine, the concentrations of carbon dioxide, oxygen, and methane are monitored by the gas concentration monitoring system. When the carbon dioxide concentration in the gob area reaches 50%, the gas injection stops. As time goes by, the residual coal in the gob gradually adsorbs the injected carbon dioxide. When the carbon dioxide concentration in the gob area decreases, additional gas is injected until the carbon dioxide concentration reaches 50% and then the gas injection stops.

2. The method for preventing and extinguishing fire in coal mines according to claim 1, wherein After the CO2 gas is enriched or captured by physical adsorption or chemical adsorption, its purity preferably reaches more than 60%.

3. A coal mine fire prevention and extinguishing method according to claim 1, characterized in that After the CO2 gas is enriched or captured by physical adsorption or chemical adsorption, its purity more preferably reaches more than 80%.

4. The device used in the coal mine fire prevention and extinguishing method according to claim 1, characterized in that It includes: A flue gas system, a CO2 enrichment or capture system, a CO2 storage system, a CO2 injection system, and a gas concentration monitoring system.

5. The device used in the coal mine fire prevention and extinguishing method according to claim 4, characterized in that The flue gas system includes the flue gas after gas power generation combustion, the flue gas remaining after CO2 enrichment or capture, and the flue gas temporarily discharged of CO2. The flue gas is collected from the chimney or flue. The components of the flue gas after gas power generation combustion include nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane, carbon monoxide. The flue gas remaining after CO2 enrichment or capture includes nitrogen, oxygen, carbon dioxide, water vapor, and a small amount of methane, carbon monoxide. The flue gas temporarily discharged of CO2 mainly includes carbon dioxide.

6. The device used in the coal mine fire prevention and extinguishing method according to claim 4, characterized in that The CO2 enrichment or capture system is a CO2 physical adsorption device or a chemical adsorption device: The CO2 physical adsorption device mainly includes a pressure swing adsorption bed and a physical adsorbent. When carbon dioxide gas passes through the adsorption bed, due to the high specific surface area and pore structure of the adsorbent, and after pressurizing to a certain pressure, the carbon dioxide gas can be adsorbed by the pores on the surface of the adsorbent. During the regeneration process, the adsorbed carbon dioxide gas in the adsorption bed is discharged by depressurization, so as to obtain pure carbon dioxide gas. The physical adsorbent includes activated carbon, molecular sieve, metal-organic framework material and solid amine adsorbent; The CO2 chemical adsorption device includes an adsorbent bed, a heater, a cooler and a regenerator. The adsorbent bed is filled with a liquid-phase adsorbent. The chemical adsorbent is an organic amine or an alkaline substance. When carbon dioxide gas passes through the adsorbent bed, carbon dioxide reacts chemically with the organic amine or alkaline substance in the adsorbent and is captured. During the regeneration process, the heater heats the adsorbed carbon dioxide in the adsorption bed to release it, and after being cooled and purified by the cooler, pure carbon dioxide gas is obtained.

7. The device used in the coal mine fire prevention and extinguishing method according to claim 4, characterized in that The CO2 storage system includes a pressurization device, a CO2 storage device, and a conversion device. The pressurization device is a centrifugal compressor or a pneumatic booster pump, and the CO 2 storage device is a steel storage tank that can withstand the pressure when CO2 is compressed from a gaseous state to a liquid state. The conversion device is a pressure reducing valve, a throttle valve, or an expander. The conversion device plays a role in regulating the pressure and can convert high-pressure or even liquid CO2 into low-pressure gaseous CO2.

8. The device used in the coal mine fire prevention and extinguishing method according to claim 4, wherein The described CO2 injection system includes a coal mine goaf and a gas injection pipeline. Preferably, the geological structure of the coal mine shaft from top to bottom includes the ground, an aquiferous stratum, an aquifuge stratum, the remaining coal seam and a rock stratum. The bottom of the coal mine goaf is located in the remaining coal seam, the higher side of the top is located in the aquifuge stratum, and the lower side of the top is located in the remaining coal seam. One end of the gas injection pipeline is connected to a conversion device or a pressurization device, and the other end is connected to the port of the coal mine goaf.

9. The device used in the coal mine fire prevention and extinguishing method according to claim 4, characterized in that The described gas concentration monitoring system includes a carbon dioxide concentration monitoring instrument, an oxygen concentration monitor and a methane concentration monitoring instrument. When the injected carbon dioxide, oxygen or methane exceeds a certain concentration, an alarm is given, and at the same time, the injection or stop of CO2 is controlled through the PLC system.

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