A goaf fire prevention and extinguishing method based on wind flow distribution and dry ice phase change

Abstract

The present invention discloses a goaf fire prevention and extinguishing method based on airflow distribution and dry ice phase transition. The method comprises the following steps: measuring the airflow intersection between the goaf and the coal mining face; laboratory testing the impact range of dry ice sublimation into CO2 gas; placing dry ice in the goaf; and, during mining, after the goaf roof collapses, the coal and rock in the goaf roof fall onto an insulated box containing dry ice, causing the box to rupture. The dry ice is buried by the coal and rock in the goaf roof and sublimates to form CO2 gas, which diffuses around the goaf to extinguish the fire. By arranging the dry ice-filled insulated boxes parallel to the coal mining face and dividing them into sections based on airflow intersection within the goaf, the present invention ensures that the CO2 gas generated by the sublimation of the dry ice is uniformly distributed within the goaf. The dry ice in the insulated boxes does not undergo phase transition when in the heat dissipation zone, but sublimates when in the oxidation zone, the most susceptible area for spontaneous combustion, after being broken apart by the falling coal and rock in the goaf roof. This achieves precise fire prevention and extinguishing.

Description

Technical Field

[0001] The present invention relates to the technical field of fire prevention and extinguishing in coal mine goafs, and in particular to a fire prevention and extinguishing method for goafs based on wind flow distribution and dry ice phase change. Background Art

[0002] Most coal mining in my country is done underground, where tunnels are driven from the ground toward the target coal seam and a mining face is deployed. Due to factors such as the formation conditions and the degree of metamorphism, some coal seams are prone to spontaneous combustion, which can, under certain circumstances, cause fires and pose a serious threat to safe mining. For coal mines with seams prone to spontaneous combustion, the goaf is the most vulnerable location for spontaneous combustion fires. This is especially true when there is a large amount of coal left in the goaf and sufficient air leakage. Due to the lack of oxygen and heat accumulation, the coal left in the goaf is prone to spontaneous combustion, leading to secondary disasters.

[0003] At present, the fire prevention and extinguishing methods in goafs include injection of inert gas (N2, CO2, etc.), grouting, spraying of inhibitors, injection of three-phase foam, blocking of air leakage channels, and pressure-equalizing fire prevention and extinguishing. Among them, injection of inert gas and grouting are more commonly used. Both of these fire prevention and extinguishing methods are to arrange pipelines in the tunnel (generally the air intake tunnel) and use the fluid outlets reserved on the pipelines to inject a large amount of fluid into the goaf for fire prevention and extinguishing. That is, the fire extinguishing source is generally concentrated at a certain point in the goaf (on the side of the air intake tunnel), and the goaf is diffused and filled by large-scale injection and the use of pores and airflow distribution in the goaf. This results in a huge consumption of fire extinguishing materials, uneven distribution of fire extinguishing materials in the goaf, and difficulty in evaluating the fire prevention and extinguishing effect. In particular, when there are air leakage channels and structural cracks near the fire extinguishing source, a large amount of fire extinguishing materials will be lost, seriously affecting the fire prevention and extinguishing effect of the goaf, and thus threatening the safe production of the coal mining face. In addition, when inert gas is injected in large quantities, it will cause the oxygen concentration in the air at the coal mining face to decrease, which may cause safety risks such as suffocation of personnel. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a goaf fire prevention and extinguishing method based on wind flow distribution and dry ice phase change.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change, comprising the following steps:

[0007] S1. Determination of airflow intersection between goaf and coal mining face:

[0008] S101. After a constant and continuous release of tracer gas at a tracer gas release point in the lower corner area of ​​the coal mining face, the tracer gas is carried into the goaf by the airflow, then from the goaf into the coal mining face, and finally into the return air lane;

[0009] S102. Within the coal mining face, tracer gas concentrations in the airflow are measured using a tracer gas detector at multiple tracer gas concentration detection points under the hydraulic supports of the coal mining face along the airflow direction. A graph is drawn showing the distance between each tracer gas concentration detection point and the air intake tunnel and the change in tracer gas concentration. The section where the airflows intersect between the coal mining face and the goaf is divided based on the trend of the curve:

[0010] The first section: the tracer gas concentration is 0, and the air flow from the coal mining face mainly flows into the goaf;

[0011] The second section: The tracer gas concentration is in a slowly rising section. In this section, the tracer gas concentration is not zero, but does not exceed 100 ppm. In this section, the airflow from the coal mining face flows into the goaf, and the airflow from the goaf flows into the coal mining face.

[0012] The third section: The tracer gas concentration is in a rapid rising stage. The tracer gas concentration in this section is not zero, and the tracer gas concentration value at the first tracer gas concentration detection point in the section increases by not less than 100% compared with the tracer gas concentration value at the last tracer gas concentration detection point in the second section. This section is mainly caused by the air flow from the goaf merging into the coal mining face.

[0013] S2. The scope of influence when dry ice sublimates into CO2 gas in laboratory test:

[0014] S201. In the laboratory, first obtain an insulated box. The insulated box is a sealed hollow cubic structure. To simulate the burial of dry ice after the insulated box breaks, the upper cover of the insulated box is removed during the experiment. Then, dry ice of mass M is placed in the insulated box. The insulated box is placed in the center of the laboratory floor with the opening facing upward. Coal blocks are laid on the outside of the insulated box and the insulated box is buried by stacking the coal blocks. The coal blocks are collected from the coal left in the goaf, and the stacked coal blocks have an overall rectangular parallelepiped shape.

[0015] S202, inserting a plurality of CO2 gas sensors on the upper surface of the stacked coal blocks to measure the CO2 gas concentration when the dry ice sublimates;

[0016] All CO2 gas sensors are set to be on, and the test conditions are normal temperature and pressure. During the process of dry ice in the insulated box sublimating into CO2 gas, each CO2 gas sensor measures the CO2 gas concentration. Among all CO2 gas sensors with a measured CO2 gas concentration greater than or equal to 50%, the CO2 gas sensor farthest from the insulated box is selected, and the distance between the CO2 gas sensor and the insulated box is used as the diffusion radius n of the dry ice with a mass M sublimating into CO2 gas.

[0017] S3. Dry ice placement in goaf:

[0018] Based on the diffusion radius n obtained in step S202 and the section of airflow intersection between the coal mining face and the goaf divided in step S102, multiple insulation boxes containing dry ice of mass M are placed into the goaf. In this case, the insulation boxes are sealed hollow cube structures that completely seal the dry ice. A row of insulation boxes are placed parallel to the coal mining face and are placed sequentially from the air intake to the return airway. The placement principle is as follows:

[0019] In the first section, the distance between adjacent insulation boxes is n;

[0020] In the second section, the distance between adjacent insulation boxes is 1.5n;

[0021] In the third section, the distance between adjacent insulation boxes is 2n;

[0022] S4. During mining, after the roof of the goaf collapses, the coal and rock on the roof of the goaf falls onto the insulation box filled with dry ice, causing the insulation box to rupture. The dry ice is buried by the coal and rock on the roof of the goaf and sublimates to form CO2 gas that spreads around to prevent and extinguish fires. As the working face continues to advance, along the advancing direction of the coal mining working face, every time the coal mining working face advances L meters, n≤L≤2n, insulation boxes are placed in the goaf in sequence according to step S3 until the mining of the coal mining working face is completed.

[0023] Furthermore, in step S101, the distance between the tracer gas release point and the hydraulic support of the coal mining face is 2m, and is close to the wall of the air intake tunnel.

[0024] Furthermore, in step S101, the tracer gas is SF6 or He, the release flow rate of the tracer gas is 0.25 L / min, and the continuous release time is 10 minutes.

[0025] Furthermore, in step S102, the interval between adjacent tracer gas concentration detection points is 5 m, and each tracer gas concentration detection point is 4 m away from the coal mining face in the advancing direction of the coal mining face and 1.5 m away from the coal seam floor in the vertical direction.

[0026] Furthermore, in step 201, the height h of the heat preservation box is 40cm-50cm, the height H of the stacked coal blocks is 1.5 times-2 times of h, and the overall length and width of the stacked coal blocks are equal and not less than 25m.

[0027] Furthermore, in step S201, the mass M of the dry ice is 15 kg.

[0028] Furthermore, in step S202, the air inlet of the CO2 gas sensor is inserted into the coal block to a depth d of 1 cm to 5 cm.

[0029] Furthermore, in step S202, the plurality of CO2 gas sensors are arranged in two rows perpendicular to each other and horizontally outside the thermal insulation box, and the distance between two adjacent CO2 gas sensors in each row is 2m, and the distance between the thermal insulation box and adjacent CO2 gas sensors is also 2m.

[0030] Furthermore, in step S3, the thermal insulation box is deployed using an intrinsically safe drone for coal mines.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention arranges the insulation boxes filled with dry ice in a direction parallel to the coal mining face and divides the sections according to the intersection of wind flows in the goaf, thereby ensuring to the greatest extent that the CO2 gas formed after the dry ice sublimates is evenly distributed in the goaf, thereby improving the fire prevention and extinguishing effect.

[0033] (2) The dry ice in the insulation box of the present invention does not undergo phase change when it is in the heat dissipation zone. However, when it is in the oxidation zone, which is most prone to spontaneous combustion, and the insulation box is ruptured due to coal rock collapse in the goaf roof, the dry ice will sublime, thereby achieving precise fire prevention and extinguishing. In addition, the sublimation of dry ice absorbs heat to lower the surrounding temperature, and the CO2 gas has a strong retention capacity, diluting the oxygen concentration around the coal waste, which has a dual effect of inhibiting the spontaneous combustion of the coal waste.

[0034] (3) The dry ice of the present invention is contained in an insulated box, which has a simple structure and low cost. The dry ice is lightweight and easy to deploy, resulting in less consumption of fire-fighting materials in the goaf, which in turn reduces the overall cost. Furthermore, the insulated box containing dry ice of the present invention is deployed via an intrinsically safe drone for coal mines. This deployment method is simple, highly safe, and labor-intensive, effectively avoiding the dangers that may arise from personnel entering the goaf. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the positions of the tracer gas release point and the tracer gas concentration detection point in an embodiment of the present invention;

[0036] Figure 2Schematic diagram of the installation position of the CO2 gas sensor and the thermal insulation box for laboratory measurement of the impact range after dry ice sublimation in an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the relative position between the air inlet of the CO2 gas sensor and the thermal insulation box in an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the placement and distribution of thermal insulation boxes in the goaf according to an embodiment of the present invention;

[0039] Figure 5 Graph showing the distance between each tracer gas concentration detection point and the air inlet tunnel and the change in tracer gas concentration in an embodiment of the present invention;

[0040] Markings in the figure: 1. Goaf; 2. Coal mining face; 3. Tracer gas release point; 4. Tracer gas concentration detection point; 5. Hydraulic support of the coal mining face; 6. Air intake lane; 7. Return air lane; 8. Coal rock on the roof of the goaf; 9. Insulation box; 10. CO2 gas sensor; 11. Air inlet; 12. Dry ice; 13. Coal block. DETAILED DESCRIPTION

[0041] The following describes the content of the present invention in more detail with reference to the accompanying drawings and specific embodiments, and further elaborates on the present invention.

[0042] Taking the coal mining face 2 of a mine in Xinzhou, Shanxi as an example, the inclined length of the coal mining face 2 is 150m, the strike length is 800m, and the coal seam has a tendency to spontaneous combustion.

[0043] Reference Figures 1-4 A method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change comprises the following steps:

[0044] S1, determination of airflow intersection between goaf 1 and coal mining face 2:

[0045] S101. After a constant and continuous release of tracer gas at the tracer gas release point 3 in the lower corner area of ​​the coal mining face 2, the tracer gas is carried into the goaf 1 by the wind flow, and then enters the coal mining face 2 from the goaf 1, and finally enters the return air lane 7.

[0046] In step S101, the distance between the tracer gas release point 3 and the hydraulic support 5 of the coal mining face is 2m, and the point is close to the wall of the air inlet tunnel 6;

[0047] In step S101, the tracer gas is SF6 or He, the release flow rate of the tracer gas is 0.25 L / min, and the continuous release time is 10 minutes;

[0048] In this embodiment, the tracer gas is SF6.

[0049] S102. Within the coal mining face 2, tracer gas concentrations in the airflow are measured using a tracer gas detector at multiple tracer gas concentration detection points 4 beneath the hydraulic supports 5 of the coal mining face along the airflow direction. (Adjacent tracer gas concentration detection points 4 are spaced 5 m apart, and each tracer gas concentration detection point 4 is 24 m from the coal mining face along the advancing direction of the coal mining face 2 and 1.5 m from the coal seam floor in the vertical direction.) A graph is drawn showing the distance between each tracer gas concentration detection point 4 and the air intake tunnel 6 and the change in tracer gas concentration. The section where the airflows intersect between the coal mining face 2 and the goaf 1 is divided based on the trend of the curves.

[0050] The first section: the tracer gas concentration is 0, and the air flow from the coal mining face 2 mainly flows into the goaf 1;

[0051] The second section: The tracer gas concentration is in a slowly rising section. In this section, the tracer gas concentration is not zero, but does not exceed 100 ppm. In this section, the airflow from the coal mining face 2 flows into the goaf 1, and the airflow from the goaf 1 flows into the coal mining face 2.

[0052] The third section: The tracer gas concentration is in a rapid rising stage. The tracer gas concentration in this section is not zero, and the tracer gas concentration value at the first tracer gas concentration detection point in this section increases by not less than 100% compared with the tracer gas concentration value at the last tracer gas concentration detection point in the second section. In this section, the airflow from goaf 1 mainly flows into coal mining face 2.

[0053] like Figure 5 As shown, in this embodiment, a coal mining face 2 of a mine in Xinzhou, Shanxi Province was measured, wherein each tracer gas concentration detection point 4 was respectively subjected to three tracer gas concentration detections. The wind flow intersection between the coal mining face 2 and the goaf 1 was:

[0054] The interval between the tracer gas concentration detection point 4 and the air inlet tunnel 6, which is 0-95m, is the first section; the interval between the tracer gas concentration detection point 4 and the air inlet tunnel 6, which is 95m-120m, is the second section; and the interval between the tracer gas concentration detection point 4 and the air inlet tunnel 6, which is 120m-150m to the return air tunnel 7, is the third section.

[0055] S2. The scope of influence when the laboratory tests the sublimation of dry ice 12 into CO2 gas:

[0056] S201. In the laboratory, first, take an insulated box 9. The insulated box 9 is a sealed hollow cubic structure made of biodegradable plastic. To simulate the burial of dry ice 12 after the insulated box 9 breaks, the cover of the insulated box 9 is removed during the experiment. Then, dry ice 12 of mass M is placed in the insulated box 9. The insulated box 9 is placed with the cover facing up at the center of the laboratory floor. Coal blocks 13 are laid outside the insulated box 9. The insulated box 9 is buried by stacking the coal blocks 13. The coal blocks 13 are collected from the coal left in the goaf. The stacked coal blocks 13 have an overall rectangular parallelepiped shape. The height h of the insulated box 9 is 40 cm to 50 cm. The height H of the stacked coal blocks 13 is 1.5 to 2 times h. The overall length and width of the stacked coal blocks 13 are equal and not less than 25 m. The stacked coal blocks 13 can be blocked on all sides with baffles to form an overall rectangular parallelepiped shape.

[0057] In this embodiment, the mass M of the dry ice 12 is specifically 15 kg. The dry ice 12 is in a cubic shape.

[0058] S202, inserting multiple CO2 gas sensors 10 above the coal blocks in the container to measure the CO2 gas concentration when the dry ice 12 sublimates, with the air inlet 11 of the CO2 gas sensor 10 inserted into the coal blocks to a depth d of 1 cm to 5 cm;

[0059] Specifically, the plurality of CO2 gas sensors 10 are arranged in two rows perpendicular to each other and horizontally outside the heat preservation box 9, and the distance between two adjacent CO2 gas sensors 10 in each row is 2m, and the distance between the heat preservation box 9 and the adjacent CO2 gas sensors 10 is also 2m;

[0060] All CO2 gas sensors 10 are set to the on state, and the test conditions are normal temperature and pressure. During the process of dry ice 12 in the insulation box 9 sublimating into CO2 gas, each CO2 gas sensor 10 measures the CO2 gas concentration. Among all CO2 gas sensors 10 with a measured CO2 gas concentration greater than or equal to 50%, the CO2 gas sensor 10 farthest from the insulation box 9 is selected, and the distance between it and the insulation box 9 is used as the diffusion radius n of the dry ice 12 with a mass M sublimating into CO2 gas, where n is in meters.

[0061] In this embodiment, laboratory measurements show that the diffusion radius n of the insulated box 9 containing 15 kg of dry ice 12 pre-buried in a coal block and the dry ice 12 sublimates into CO2 gas is 10 meters;

[0062] S3, dry ice 12 is placed in goaf 1:

[0063] Based on the diffusion radius n = 10 meters obtained in step S202 and the section of airflow intersection between the coal mining face 2 and the goaf 1 divided in step S102, a coal mine intrinsically safe drone is used to drop multiple insulation boxes 9 containing 15 kg of dry ice 12 into the goaf 1. At this time, the insulation boxes 9 are sealed hollow cubic structures that completely seal the dry ice 12. The insulation boxes 9 are dropped in a row parallel to the coal mining face 2 and are dropped sequentially from the air intake lane 6 to the return air lane 7. The drop principle is as follows:

[0064] In the first section, the distance between adjacent insulation boxes 9 is n;

[0065] In the second section, the distance between adjacent insulation boxes 9 is 1.5n;

[0066] In the second section, the distance between adjacent insulation boxes 9 is 2n;

[0067] According to step S102, an insulation box 9 filled with dry ice 12 is arranged at intervals of 10 m in the first section of the distance between the tracer gas concentration detection point 4 and the air inlet tunnel 6, which is 0-95 m.

[0068] In the second section of the air inlet tunnel 6, which is 95m-120m away from the tracer gas concentration detection point 4, an insulation box 9 filled with dry ice 12 is arranged every 15m.

[0069] In the interval from the tracer gas concentration detection point 4 to the air inlet tunnel 6, which is 120 m away, to the return air tunnel 7, an insulation box 9 filled with dry ice 12 is arranged every 20 m.

[0070] S4. During mining, after the roof of the goaf 1 collapses, the coal rock 8 of the goaf roof falls onto the insulation box 9 containing dry ice 12, causing the insulation box 9 to rupture. The dry ice 12 is buried by the coal rock 8 of the goaf roof and sublimates to form CO2 gas, which diffuses around to prevent fire. The CO2 gas diffuses around under the influence of the pressure gradient. Since the dry ice 12 is buried by the coal rock 8 of the goaf roof at this time, it is limited by the wind flow. Therefore, after its phase change, it is not easily carried away by the wind flow, effectively extending its retention time on the coal surface and reducing the amount of it entering the working space of the coal mining face 2, thereby effectively reducing the risk of suffocation. As the working face continues to advance, along the advancing direction of the coal mining face 2, the coal mining face 2 advances L meters, n≤L≤2n (in this embodiment, L=15 meters), and the insulation box 9 is placed in the goaf 1 in sequence according to step S3 until the mining of the coal mining face 2 is completed.

[0071] The foregoing description is merely a preferred embodiment of the present invention, and these embodiments are by no means intended to limit the present invention in any way. It will be apparent to those skilled in the art that various modifications and variations may be made to the present invention. Any changes made by those skilled in the art, based on the teachings of this specification, to the embodiments of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change, characterized in that: The following steps are involved: S1. Determination of airflow intersection between goaf and coal mining face: S101. After a constant and continuous release of tracer gas at a tracer gas release point in the lower corner area of ​​the coal mining face, the tracer gas is carried into the goaf by the airflow, then from the goaf into the coal mining face, and finally into the return air lane; S102. Within the coal mining face, tracer gas concentrations in the airflow are measured using a tracer gas detector at multiple tracer gas concentration detection points under the hydraulic supports of the coal mining face along the airflow direction. A graph is drawn showing the distance between each tracer gas concentration detection point and the air intake tunnel and the change in tracer gas concentration. The section where the airflows intersect between the coal mining face and the goaf is divided based on the trend of the curve: The first section: the tracer gas concentration is 0, and the air flow from the coal mining face mainly flows into the goaf; The second section: The tracer gas concentration is in a slowly rising section. In this section, the tracer gas concentration is not zero, but does not exceed 100 ppm. In this section, the airflow from the coal mining face flows into the goaf, and the airflow from the goaf flows into the coal mining face. The third section: The tracer gas concentration is in a rapid rising stage. The tracer gas concentration in this section is not zero, and the tracer gas concentration value at the first tracer gas concentration detection point in the section increases by not less than 100% compared with the tracer gas concentration value at the last tracer gas concentration detection point in the second section. This section is mainly caused by the air flow from the goaf merging into the coal mining face. S2. The scope of influence when dry ice sublimates into CO2 gas in laboratory test: S201. In the laboratory, first obtain an insulated box. The insulated box is a sealed hollow cubic structure. To simulate the burial of dry ice after the insulated box breaks, the upper cover of the insulated box is removed during the experiment. Then, dry ice of mass M is placed in the insulated box. The insulated box is placed in the center of the laboratory floor with the opening facing upward. Coal blocks are laid on the outside of the insulated box and the insulated box is buried by stacking the coal blocks. The coal blocks are collected from the coal left in the goaf, and the stacked coal blocks have an overall rectangular parallelepiped shape. S202, inserting a plurality of CO2 gas sensors on the upper surface of the stacked coal blocks to measure the CO2 gas concentration when the dry ice sublimates; All CO2 gas sensors are set to be on, and the test conditions are normal temperature and pressure. During the process of dry ice in the insulated box sublimating into CO2 gas, each CO2 gas sensor measures the CO2 gas concentration. Among all CO2 gas sensors with a measured CO2 gas concentration greater than or equal to 50%, the CO2 gas sensor farthest from the insulated box is selected, and the distance between the CO2 gas sensor and the insulated box is used as the diffusion radius n of the dry ice with a mass M sublimating into CO2 gas. S3. Dry ice placement in goaf: Based on the diffusion radius n obtained in step S202 and the section of airflow intersection between the coal mining face and the goaf divided in step S102, multiple insulation boxes containing dry ice of mass M are placed into the goaf. In this case, the insulation boxes are sealed hollow cube structures that completely seal the dry ice. A row of insulation boxes are placed parallel to the coal mining face and are placed sequentially from the air intake to the return airway. The placement principle is as follows: In the first section, the distance between adjacent insulation boxes is n; In the second section, the distance between adjacent insulation boxes is 1.5n; In the third section, the distance between adjacent insulation boxes is 2n; S4. During mining, after the goaf roof collapses, the coal and rock in the goaf roof falls onto the insulation box filled with dry ice, causing the insulation box to rupture. The dry ice is buried by the coal and rock in the goaf roof and sublimates to form CO2 gas that spreads around to prevent fire; As the working face continues to advance, along the advancing direction of the coal mining working face, every time the coal mining working face advances L meters, n≤L≤2n, insulation boxes are placed in the goaf in sequence according to step S3 until the mining of the coal mining working face is completed.

2. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step S101, the distance between the tracer gas release point and the hydraulic support of the coal mining face is 2m, and the point is close to the wall of the air intake tunnel.

3. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step S101, the tracer gas is SF6 or He, the release flow rate of the tracer gas is 0.25 L / min, and the continuous release time is 10 minutes.

4. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step S102, the interval between adjacent tracer gas concentration detection points is 5 m, and each tracer gas concentration detection point is 4 m away from the coal mining face along the advancing direction of the coal mining face and 1.5 m away from the coal seam floor in the vertical direction.

5. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step 201, the height h of the heat preservation box is 40 cm to 50 cm, the height H of the stacked coal blocks is 1.5 times to 2 times of h, and the overall length and width of the stacked coal blocks are equal and not less than 25 m.

6. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step S201, the mass M of the dry ice is 15 kg.

7. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step S202, the air inlet of the CO2 gas sensor is inserted into the coal block to a depth d of 1 cm to 5 cm.

8. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step S202, the multiple CO2 gas sensors are arranged in two rows perpendicular to each other and horizontally outside the thermal insulation box, and the distance between two adjacent CO2 gas sensors in each row is 2m, and the distance between the thermal insulation box and adjacent CO2 gas sensors is also 2m.

9. The method for preventing and extinguishing fire in goaf based on wind flow distribution and dry ice phase change according to claim 1, characterized in that: In step S3, the thermal insulation box is deployed using an intrinsically safe drone for coal mines.

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