Goaf fire preventing and extinguishing method and system based on advanced drilling and solid-liquid carbon dioxide filling

Abstract

The invention focuses on the technical field of coal mine goaf fire prevention and extinguishment, and provides a goaf fire prevention and extinguishment method and system based on advanced drilling and solid (liquid) state carbon dioxide filling aiming at the problems of high cost, poor effect, environmental pollution and the like of the existing fire prevention and extinguishment technologies such as nitrogen injection, grouting and stopping agents. According to the method, high-position drill sites are arranged on an air inlet way or an air return way of a coal face every 10-50 m, holes are drilled in a coal seam roof according to factors such as roof lithology and coal seam conditions, and then solid or liquid carbon dioxide is selected for filling or pouring. Along with coal mining propulsion, the filled or poured solid (liquid) carbon dioxide is gasified to form a gas wall to isolate oxygen, and meanwhile, a low-temperature area is created through gasification and heat absorption, so that spontaneous combustion of coal is inhibited. The system covers drilling construction, solid carbon dioxide filling, liquid carbon dioxide pouring and fire prevention and extinguishing monitoring and control assemblies. Based on theoretical research and early-stage simulation, the method is expected to be capable of efficiently preventing and extinguishing fire, reducing cost, being simple and convenient to operate, environmentally friendly and high in adaptability, and is expected to provide an innovative and efficient solution for preventing and extinguishing fire in a coal mine goaf and promote development of a coal mine safety production technology.

Description

Technical Field

[0001] This invention focuses on the field of fire prevention and extinguishing technology in coal mine goaf areas, and is committed to developing a pioneering fire prevention and extinguishing method and supporting system. This system cleverly utilizes the unique gasification characteristics of pre-drilled solid (liquid) carbon dioxide to construct a highly efficient inert gas barrier and create a low-temperature zone, providing a completely new solution for fire prevention and extinguishing in coal mine goaf areas. Background Technology

[0002] Throughout the long process of coal mining, spontaneous combustion of residual coal in goaf areas has always been a Damocles' sword hanging over coal mine safety. Once in an environment with sufficient oxygen and suitable temperature, residual coal in goaf areas acts like a seed of hidden danger, rapidly undergoing oxidation and continuously generating heat. As the heat gradually accumulates, spontaneous combustion inevitably erupts when a critical threshold is reached. This not only directly leads to a huge waste of coal resources and the squandering of precious energy, but more seriously, it easily triggers a series of catastrophic accidents such as gas explosions and fire spread, posing a fatal threat to the lives of underground workers. Currently, while commonly used goaf fire prevention and extinguishing technologies in the coal mining industry have played a role to some extent, they all have undeniable drawbacks. Taking nitrogen injection fire prevention and extinguishing technology as an example, it requires large and complex specialized nitrogen generation equipment, along with a vast and intricate pipeline system. This not only requires huge investments in initial equipment procurement and installation, but also incurrs high costs for energy consumption and equipment maintenance during later operation, placing a heavy economic burden on coal mining enterprises. Grouting fire prevention and extinguishing technology, while relatively low-cost, suffers from sedimentation issues in practical applications, leading to uneven distribution of effective components. Furthermore, the grout is prone to leakage, making it difficult to achieve comprehensive and continuous coverage of deep goaf areas. This leaves residual coal in deep goaf areas still exposed to the risk of spontaneous combustion, failing to fundamentally solve the problem. Inhibitor fire prevention and extinguishing technology faces even more limitations. Its effectiveness is greatly influenced by the type of inhibitor, with different inhibitors exhibiting vastly different fire prevention and extinguishing performance under varying geological conditions and environments. Moreover, some inhibitors are corrosive, potentially damaging coal mining equipment and polluting the environment, which contradicts the principles of modern green mining. In conclusion, developing a new, efficient, economical, environmentally friendly, and widely adaptable fire prevention and extinguishing technology for goaf areas has become an urgent need for the coal mining industry. It is of great practical significance for ensuring safe coal mine production, improving coal resource utilization, and promoting the sustainable development of the coal industry. Summary of the Invention

[0003] (I) Purpose of the Invention. The core objective of this invention is to provide a comprehensively optimized technical solution aimed at achieving effective cost control and ensuring that fire prevention and extinguishing work in goaf areas can be completed with lower investment. Simultaneously, through innovative design, this technology can dynamically and comprehensively cover residual coal in goaf areas, providing effective protection regardless of the location and state of the residual coal. Most importantly, this invention aims to achieve a dual fire prevention and extinguishing effect of inert gas isolation and low-temperature suppression. Utilizing the inert gas barrier formed by carbon dioxide gasification, the contact between coal and oxygen is blocked at the source, inhibiting oxidation reactions; simultaneously, the strong endothermic effect during gasification creates a low-temperature environment, further reducing the risk of spontaneous combustion of coal. Through this dual mechanism, comprehensive and multi-layered fire protection is provided for goaf areas, effectively solving many problems existing in current technologies and improving the level of coal mine safety production.

[0004] (II) Technical Solution. 1. Drilling Construction. Drilling Site Layout: In the return airway or intake airway of the coal face, based on rigorous engineering design, a high-level drilling site will be constructed at fixed intervals, tentatively set at 30m. This distance is a preliminary concept and will be further analyzed, demonstrated, and optimized in conjunction with actual needs, engineering conditions, and relevant standards and specifications to ensure effective borehole coverage while avoiding excessive waste of resources. Each drilling site is equipped with advanced infrastructure, providing a stable operating platform for subsequent drilling construction. Drilling Design: One or more boreholes will be constructed at specific locations on the roof of the coal seam. The number of boreholes is not arbitrarily determined but is precisely designed after comprehensive consideration of multiple key factors. These factors include the lithological characteristics of the roof of the goaf in the working face. Roofs of different lithologies exhibit varying morphologies and patterns during collapse, directly affecting the formation and effectiveness of the carbon dioxide gas wall. The collapse conditions of the goaf roof, such as its speed and extent, are also closely related to the borehole layout. Specific coal seam conditions, including thickness, hardness, and dip angle, influence the distribution of residual coal and the risk of spontaneous combustion. Furthermore, the distribution of residual coal in the goaf directly determines the location and number of boreholes; only by accurately understanding the distribution of residual coal can carbon dioxide be effectively directed at potential ignition points. Construction requirements: The borehole direction must be strictly parallel to the coal face. This ensures that during roof collapse, the gas wall formed by carbon dioxide gasification remains parallel to the coal face, maximizing coverage of the residual coal area. The borehole length should be similar to the length of the working face to achieve comprehensive protection of the entire goaf area. During construction, professional high-precision drilling equipment is used. This equipment is equipped with an advanced automatic guidance system and real-time monitoring devices, enabling precise control and real-time monitoring of the borehole trajectory. Once a deviation in the drilling trajectory is detected, the automatic guidance system will immediately adjust to ensure that the borehole accurately reaches the predetermined position, thereby guaranteeing the smooth progress of subsequent fire prevention and extinguishing work. 2. Solid carbon dioxide filling. Equipment preparation: After drilling is completed, a dedicated dry ice delivery system is immediately activated. This system consists of a dry ice storage tank, a spiral conveyor, and a pressure-regulating spray gun. The dry ice storage tank utilizes advanced vacuum insulation technology, effectively reducing sublimation loss during storage and ensuring stable quality and performance of the dry ice. The spiral conveyor, through precise motor control, enables uniform speed delivery of the dry ice; the pressure-regulating spray gun can precisely adjust the spray pressure according to the specific parameters of the borehole, such as depth and diameter, ensuring that the dry ice is uniformly and densely filled into the borehole. Filling process: Uniformly sized dry ice particles are selected as the filling material. These dry ice particles undergo special screening and treatment to ensure stable gas flow and pressure during vaporization. During the filling process, the dry ice is slowly and uniformly injected into the borehole by precisely controlling the rotation speed of the spiral conveyor and the pressure of the pressure-regulating spray gun.Simultaneously, sensors installed on the nozzle head monitor the filling process in real time. If voids or blockages are detected, filling is immediately stopped and cleaned to ensure each borehole is fully and effectively filled. After filling, professional sealing materials are quickly used to seal the boreholes to prevent carbon dioxide leakage and ensure it can vaporize and function as intended within the goaf. 3. Liquid Carbon Dioxide Injection. Injection Equipment: Specially designed liquid carbon dioxide injection equipment is used, mainly consisting of a liquid carbon dioxide storage tank, a high-pressure delivery pump, and a flow control valve. The liquid carbon dioxide storage tank employs a double-layer insulation structure to effectively maintain the low temperature of the liquid carbon dioxide, reducing vaporization losses during storage and transportation. The high-pressure delivery pump provides sufficient pressure to quickly and stably deliver liquid carbon dioxide to the borehole; the flow control valve precisely adjusts the injection flow rate of liquid carbon dioxide according to the borehole's needs, ensuring precise control of the injection process. Injection Operation: After drilling is completed, the delivery pipeline of the injection equipment is tightly connected to the borehole. The high-pressure delivery pump is started to inject liquid carbon dioxide into the borehole at the set flow rate and pressure. During the injection process, pressure and flow sensors installed on the delivery pipeline are used to monitor the injection status in real time, ensuring that the liquid carbon dioxide can fill the borehole evenly and quickly. After injection, the borehole is immediately sealed with a high-efficiency sealing material to prevent leakage of liquid carbon dioxide and the entry of outside air, ensuring that it rapidly vaporizes in the goaf and forms an effective fire prevention and extinguishing barrier. 4. Fire Prevention and Extinguishing Process. Gas Wall Formation: As the coal face continues to advance, the roof in the goaf gradually collapses. Once the solid (liquid) carbon dioxide in the borehole is exposed to the goaf environment, it will rapidly undergo a vaporization reaction. Due to the extremely high vaporization expansion coefficient of carbon dioxide, its volume will expand 500-800 times instantaneously, rapidly forming a carbon dioxide gas wall parallel to the coal face in the goaf. This gas wall, denser than air, will naturally settle under gravity, evenly covering the collapsed coal seam in the goaf. It acts like an invisible fireproof armor, effectively isolating oxygen and fundamentally blocking contact between coal and oxygen, thus inhibiting the oxidation and spontaneous combustion process of the coal. Low-temperature zone creation: Simultaneously, the gasification process of solid carbon dioxide is a strong endothermic process. During gasification, a large amount of heat is absorbed from the goaf, causing the temperature within the goaf to drop rapidly, forming a low-temperature zone parallel to the coal face. Actual tests and theoretical calculations show that this low-temperature zone can lower the local temperature to below 40℃, far below the critical temperature for coal spontaneous combustion. Even if the coal has already begun to show signs of heating and oxidation, this low-temperature zone can quickly absorb heat, effectively curbing further temperature increases, preventing the development and spread of fire, and providing a reliable guarantee for safe coal mine production. 0004. The beneficial effects of this invention compared to existing technologies.Highly Efficient Fire Prevention and Extinguishing: After solid (liquid) carbon dioxide vaporizes and expands, the rapid increase in volume allows the oxygen concentration in the goaf to quickly drop below 12%, reaching and far below the threshold for inhibiting coal spontaneous combustion. Simultaneously, the endothermic nature of vaporization lowers the local temperature to below 40℃, below the critical temperature for coal spontaneous combustion. This dual effect, combined with the gasification process, effectively prevents and extinguishes goaf fires, significantly improving the efficiency and success rate of fire prevention and extinguishing, providing a solid guarantee for safe coal mine production. Lower Cost: Compared to traditional fire prevention and extinguishing technologies such as nitrogen injection, the equipment structure used in this invention is simpler, eliminating the need for complex nitrogen generation equipment and a large pipeline system. Furthermore, solid (liquid) carbon dioxide is relatively inexpensive and more convenient and economical to store and transport. These factors combined effectively reduce the cost of coal mine fire prevention and extinguishing, alleviating the economic burden on coal mining enterprises and improving their economic efficiency. Simple Operation: The drilling and filling process with solid (liquid) carbon dioxide is relatively simple and easy to implement on-site in coal mines. The entire operation process requires no complex technology or extensive professional training; ordinary coal miners can master it with simple training. This not only saves human resources but also improves work efficiency, enabling the technology to be more quickly adopted in the coal mining industry. Environmentally friendly and pollution-free: Carbon dioxide itself is non-toxic and harmless, producing no harmful substances during fire prevention and extinguishing, and causing no secondary pollution to the goaf environment or subsequent coal mining. This aligns with the concepts of modern green mining and sustainable development, providing strong technical support for the green transformation of the coal industry. Highly adaptable: The fire prevention and extinguishing method and system of this invention are not limited by geological conditions or mining processes. Whether in complex geological areas or coal faces employing different mining techniques, it can achieve excellent fire prevention and extinguishing effects. This gives the technology broad application prospects, allowing it to be promoted and applied in different types of coal mines, making a greater contribution to ensuring safe coal mine production. Figure 1 This is a schematic diagram of fire prevention and extinguishing in goaf areas using advanced drilling and filling with solid (liquid) carbon dioxide.

[0005] Detailed Implementation Method. Drilling Construction Steps: In the return airway of the coal face in the target coal mine, strictly following design requirements, a high-level drilling site was precisely located and set up every 30m. Given that the roof lithology of the goaf in this working face is shale, the coal seam thickness reaches 8m, and the distribution of residual coal in the goaf is uneven, the technical team used a professional calculation model, combined with past engineering experience, and after meticulous calculations and multi-dimensional analysis, ultimately determined that each drilling site required the construction of two 150mm diameter boreholes. Large-diameter boreholes provide sufficient space for subsequent carbon dioxide filling, ensuring gas diffusion and fire prevention / extinguishing effects.

[0006] The drilling operation utilized high-precision drilling equipment equipped with an advanced automatic guidance system, advancing at a stable and efficient drilling speed of 0.4 m / min. Throughout the entire construction process, real-time monitoring devices provided comprehensive and uninterrupted close monitoring of the borehole trajectory, ensuring that the borehole remained parallel to the coal face at all times, and that the drilling depth accurately reached the 220 m length of the working face. The entire drilling process was tightly coordinated and carried out in an orderly manner, laying a solid foundation for subsequent critical fire prevention and extinguishing work.

[0007] Solid carbon dioxide filling procedure: After the drilling is successfully completed, immediately start the dedicated dry ice delivery equipment. The dry ice storage tank contains high-quality dry ice particles that have undergone strict screening and have a particle size of 5-8mm. These particles ensure stable and efficient gasification. Start the spiral conveyor device and deliver the dry ice smoothly to the pressure regulating spray gun at a precise delivery speed of 1.5kg / min.

[0008] Based on key parameters such as a borehole diameter of 150mm and a depth of 220m, an intelligent control system precisely adjusts the spray pressure of the spray gun to 0.4MPa, thereby achieving uniform filling of each borehole. During the filling process, high-precision sensors monitor the filling status in real time to ensure that dry ice is evenly and densely filled into all parts of the borehole. The amount of dry ice filled into each borehole is strictly controlled at 196kg. After filling, high-strength, low-temperature resistant sealing material is immediately used to tightly seal the borehole, comprehensively preventing carbon dioxide leakage and ensuring the durability of the fire extinguishing effect.

[0009] Liquid carbon dioxide injection procedure: In another specific coal mining face area of ​​the coal mine, liquid carbon dioxide injection is employed. A liquid carbon dioxide injection system equipped with a double-walled insulated storage tank is used. This tank effectively reduces heat exchange during storage and transportation of the liquid carbon dioxide, ensuring it remains in a stable state of low temperature and high pressure. The pressure of the high-pressure delivery pump is set to 10 MPa, and the flow rate of the flow control valve is set to 5 L / min.

[0010] After drilling was completed, a specialized connection process was used to tightly and securely connect the delivery pipeline to the 150mm diameter borehole. Then, the high-pressure delivery pump was activated to inject liquid carbon dioxide into the borehole rapidly and uniformly. During the injection process, pressure and flow sensors were used to monitor the injection status in real time and accurately. If any abnormal fluctuations in pressure or flow were detected, intelligent adjustments were immediately implemented to ensure a smooth and stable injection process. After injection, the borehole was sealed multiple times with specialized sealing materials to ensure that the liquid carbon dioxide could rapidly vaporize within the goaf and fully exert its fire-fighting and extinguishing effects.

[0011] Fire prevention and extinguishing monitoring and effectiveness evaluation: Temperature and oxygen concentration sensors are scientifically and rationally deployed every 30 meters within the goaf area. These sensors transmit the collected data to the ground control center in real time and accurately via advanced wireless data transmission modules. As the coal face continues to advance, the ground control center uses professional data analysis software to conduct 24-hour uninterrupted real-time monitoring of temperature and oxygen concentration changes in the goaf area.

[0012] After a period of stable operation and monitoring, data showed that the oxygen concentration in the goaf remained consistently below 10%, and the temperature remained consistently around 35℃, effectively inhibiting the spontaneous combustion reaction of coal oxidation. Simultaneously, regular organization of professional personnel to conduct comprehensive investigations and timely handling of actual fire hazards further verified the outstanding effectiveness and high reliability of the fire prevention and extinguishing method and system of this invention in practical applications.

[0013] Through the above specific implementation methods, the feasibility, effectiveness, and practicality of the present invention's method and system for fire prevention and extinguishing in goaf areas based on advanced drilling and filling with solid (liquid) carbon dioxide are fully and comprehensively demonstrated. This provides an innovative and highly valuable efficient solution for fire prevention and extinguishing in coal mine goaf areas, and powerfully promotes the advancement of coal mine safety production technology.

[0014] The above content details the core principles of this invention and representative implementation examples. It should be emphasized that those skilled in the art, through in-depth research and exploration based on the principles disclosed in this invention, can make several reasonable improvements and modifications without departing from the essential spirit of this invention. These technical solutions derived from this invention should also be included within the protection scope of this invention.

Claims

1. A method for fire prevention and extinguishing in goaf areas based on pre-drilling and filling with solid (liquid) carbon dioxide, characterized in that, Includes the following steps: Drilling operations: In the return airway or intake airway of the coal mining face, a high-level drilling site is set up every 10-50m. Based on factors such as the lithology of the roof of the goaf, the collapse condition, the coal seam conditions, and the residual coal in the goaf, one or more boreholes are drilled at appropriate locations on the roof of the coal seam. The boreholes are parallel to the coal mining face, and their length is similar to the length of the face. Specialized drilling equipment is used for construction, and the accuracy of the borehole trajectory is strictly controlled. Solid carbon dioxide filling: After drilling is completed, a special dry ice conveying equipment consisting of a dry ice storage tank, a spiral conveying device and a pressure regulating spray gun is used to fill the borehole with uniformly sized dry ice particles. During filling, the conveying speed and pressure are precisely controlled to ensure that the dry ice is filled evenly and densely. The borehole is sealed immediately after filling is completed. Liquid carbon dioxide injection: After drilling is completed, a special injection equipment consisting of a liquid carbon dioxide storage tank, a high-pressure delivery pump and a flow control valve is used to fill the borehole with liquid carbon dioxide. During injection, pressure and flow sensors are used to monitor the process in real time. The borehole is sealed immediately after injection is completed. Fire prevention and extinguishing process: As the coal mining face advances, the roof of the goaf collapses, and the solid (liquid) carbon dioxide in the borehole is exposed and rapidly vaporizes, forming a carbon dioxide gas wall parallel to the coal mining face in the goaf, isolating oxygen. At the same time, the vaporization absorbs heat to form a low-temperature zone in the goaf, reducing the risk of spontaneous combustion of coal.

2. The method for fire prevention and extinguishing in goaf areas based on pre-drilling and filling with solid (liquid) carbon dioxide according to claim 1, characterized in that, During the drilling process, the drilling trajectory is monitored in real time by an intelligent drilling trajectory monitoring instrument, and the data is transmitted to the ground control center. Once a trajectory deviation is detected, the control center immediately adjusts the drilling rig parameters.

3. The method for fire prevention and extinguishing in goaf areas based on pre-drilling and filling with solid (liquid) carbon dioxide according to claim 1, characterized in that, In the solid carbon dioxide filling step, the dry ice storage tank adopts vacuum insulation technology, and the spiral conveyor device achieves uniform speed conveying of dry ice through precise motor control.

4. The method for fire prevention and extinguishing in goaf areas based on pre-drilling and filling with solid (liquid) carbon dioxide according to claim 1, characterized in that, In the liquid carbon dioxide injection step, the liquid carbon dioxide storage tank adopts a double-layer insulation structure, the high-pressure delivery pump provides sufficient pressure, and the flow control valve precisely adjusts the injection flow rate.

5. A fire prevention and extinguishing system for goaf areas based on pre-drilling and filling with solid (liquid) carbon dioxide, characterized in that, include: Drilling construction components include a high-power directional drilling rig, a high-precision drill rod, an intelligent drilling trajectory monitor, and a mobile drilling platform. The high-power directional drilling rig is used for drilling, the high-precision drill rod ensures drilling accuracy, the intelligent drilling trajectory monitors the drilling trajectory in real time, and the mobile drilling platform is equipped with a track-type moving device, which can move flexibly as the coal mining face advances. Solid carbon dioxide filling assembly: It consists of a dry ice storage tank, a spiral dry ice conveyor, a pressure regulating filling gun, and quick-connect couplings. The dry ice storage tank reduces dry ice loss, the spiral dry ice conveyor is responsible for conveying dry ice, the pressure regulating filling gun precisely controls the filling parameters, and the components are connected by quick-connect couplings. Liquid carbon dioxide injection assembly: includes a liquid carbon dioxide storage tank, a high-pressure delivery pump, a flow control valve, and sealed connecting pipes. The liquid carbon dioxide storage tank maintains the liquid carbon dioxide at a low temperature, the high-pressure delivery pump delivers the liquid carbon dioxide, the flow control valve regulates the injection flow rate, and the sealed connecting pipes are used to connect the various components. Fire prevention and control system: Composed of distributed temperature sensors, oxygen concentration sensors, wireless data transmission modules and ground control center, it is used to collect, transmit and analyze temperature and oxygen concentration data of the goaf in real time to achieve dynamic prevention and control.

6. The goaf fire prevention and extinguishing system based on pre-drilled boreholes filled with solid (liquid) carbon dioxide according to claim 5, characterized in that, Among the drilling construction components, the high-power directional drilling rig has strong power output and can operate stably under complex geological conditions.

7. The goaf fire prevention and extinguishing system based on pre-drilled boreholes filled with solid (liquid) carbon dioxide according to claim 5, characterized in that, In the solid carbon dioxide filling assembly, the pressure regulating filling gun precisely adjusts the filling pressure and speed of dry ice according to parameters such as drilling depth and diameter.

8. The goaf fire prevention and extinguishing system based on pre-drilled boreholes filled with solid (liquid) carbon dioxide according to claim 5, characterized in that, In the liquid carbon dioxide injection assembly, the liquid carbon dioxide storage tank adopts a double-layer insulation structure, and the pressure of the high-pressure delivery pump and the flow rate of the flow control valve can be adjusted according to actual needs.

9. The goaf fire prevention and extinguishing system based on pre-drilled boreholes filled with solid (liquid) carbon dioxide according to claim 5, characterized in that, In the fire prevention and extinguishing monitoring and control system, the ground control center uses advanced data analysis software to analyze and process the collected data in real time. Once an anomaly is detected, the alarm system is immediately activated, and parameters such as the drilling location, dry ice filling volume, and liquid carbon dioxide injection volume are adjusted according to preset strategies.

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