Gas-liquid two-phase combined injection coupling inerting active fire prevention method for thick coal seam before mining

Abstract

The invention belongs to the field of coal mine safety, and relates to a pre-mining gas-liquid two-phase combined injection coupling inerting active fire prevention method for a thick coal seam, which comprises the following steps of: sequentially injecting a stopping agent solution, nitrogen and carbon dioxide composite inert gas into a coal body in a pressing manner before mining of a working face, so that the coal body is effectively isolated from oxygen, and gas-liquid two-phase coupling inerting dual protection is formed; oxidation spontaneous combustion of loose coal bodies in a goaf and a coal pillar area is effectively inhibited or delayed, so that the goaf coal spontaneous combustion is actively prevented in advance, and an important technical means and approach are provided for effectively solving the comprehensive fire prevention and extinguishing problem in the initial mining and initial caving period of a fully mechanized caving face of an ultra-thick coal seam.

Description

Technical Field

[0001] The invention belongs to the field of coal mine safety and relates to a gas-liquid two-phase combined injection coupled inerting active fire prevention method before mining of thick coal seams. Background Art

[0002] Coal fire disasters always accompany the process of coal mining. Spontaneous combustion fires in the goaf will produce a large amount of toxic gases. If the mine is a high-gas mine, the gas in the goaf will also explode during the fire. All coal-producing countries in the world pay great attention to the prevention and control of coal fire disasters, because they not only lead to a large amount of coal resources being wasted, but also cause significant casualties and economic losses. At present, more than 80% of underground fires in coal mines are caused by spontaneous combustion of coal seams. With the improvement of my country's coal mining technology, the widespread use of mechanical equipment, and the large-scale use of mining equipment in coal mines, while increasing the mining volume, the problem of spontaneous combustion in coal mines will also cause greater waste and damage to coal mine resources and equipment. Comprehensive mechanized top coal caving mining is an important technology for achieving high-yield, high-efficiency and intensive mines. Due to the popularization of comprehensive top coal caving mining technology, the efficiency of coal resource mining in my country has been greatly improved.

[0003] However, the fully mechanized caving mining production process also determines that no coal is placed on the top of the working face inlet and return air chute. During the initial mining period, the untimely collapse of coal and rock also makes it difficult to place coal. The first coal placement of the fully mechanized caving working face in thick coal seams is generally carried out after the working face brushing and trial mining advances 8 to 10 meters. During the initial mining and initial caving period, the characteristics of the working face production are that the top coal is not placed or the top coal is not completely placed, so the goaf is full of loose coal body. At the same time, due to the stress concentration, the coal body behind the mining line of the working face and the coal body and coal pillar above the inlet and return air roadway are fractured to produce a large number of cracks. Therefore, during the initial mining and initial caving period of the fully mechanized caving working face in thick coal seams, a large amount of coal is lost, there is a lot of coal left in the goaf, and the coal body in the coal pillar area is broken, which leads to a high possibility of spontaneous combustion of the loose coal body in these areas. In addition, the working face advances slowly during the initial mining period, which brings great difficulties to the prediction and prevention of coal spontaneous combustion. The traditional fire prevention and extinguishing technologies of nitrogen injection in the air intake tunnel and grouting in the return air tunnel are used. Since the goaf area has a small impact range during the initial mining period, the grouting fire prevention and extinguishing method may cause a large amount of slurry to flow out, and nitrogen injection may easily cause hypoxia on the working face. At the same time, the above methods have a small range of action and cannot effectively wrap the fractured areas around the initial working face and the collapsed coal body in the goaf area, resulting in poor initial fire prevention and extinguishing effects. It is generally difficult to prevent spontaneous combustion of coal in the fully mechanized caving working face during the initial mining period.

[0004] Therefore, it is urgent to seek an efficient prevention and control technical means and method to proactively prevent the problem of spontaneous combustion of lost coal during the initial mining of thick coal seam fully mechanized caving working faces. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for active fire prevention by coupled inerting of gas-liquid two-phase combined injection before mining of thick coal seams. By successively injecting inhibitor solution, nitrogen and carbon dioxide composite inert gas into the coal body before mining at the working face, the coal body is effectively isolated from oxygen, forming a double protection of gas-liquid two-phase coupled inerting, effectively inhibiting or delaying the oxidation and spontaneous combustion of loose coal body in the goaf and coal pillar area, thereby achieving the purpose of proactively and actively preventing spontaneous combustion of coal in the goaf.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for active fire prevention by gas-liquid two-phase combined injection coupling inerting before thick coal seam mining, comprising the following steps:

[0007] S1, formulate and implement process design plan;

[0008] According to the working face mining design parameters and coal rock occurrence basic data, complete the design of gas-liquid two-phase combined injection implementation process scheme;

[0009] S2, conduct fire prevention and extinguishing drilling construction;

[0010] After the mining tunnel of the working face is formed, the first, second and third groups of fire-fighting drill holes are constructed in the coal bodies in front, above and behind the working face through the cutting holes in the working face, and the fourth group of fire-fighting drill holes are constructed in the return air tunnel of the working face along the coal pillar direction; the final hole positions of all the drill holes pass through the full thickness of the extra-thick coal seam to 0.5m above the coal seam roof, and the holes are sealed with mining hole sealers;

[0011] S3, implementation of the inhibitor solution injection process;

[0012] After the drilling construction is completed, the inhibitor injection system is connected to inject the inhibitor solution into the borehole, so that cracks are generated in the coal body under the action of fracturing, and the inhibitor solution penetrates into the coal body gaps, realizing the first level of protection against spontaneous combustion of the coal body;

[0013] S4, implementation of nitrogen and carbon dioxide composite inert gas pressure injection process;

[0014] After the borehole injection process of the inhibitor solution is completed, the borehole is connected to the nitrogen and carbon dioxide composite inert gas injection system, and the nitrogen and carbon dioxide composite inert gas is injected into the borehole, so that the gas is fully adsorbed and filled in the cracks and gaps of the coal body, forming a layer of inert gas isolation zone, realizing the second level of protection against spontaneous combustion of the coal body;

[0015] S5. During the mining process of the fully mechanized caving working face, the inhibitor injection system and the nitrogen and carbon dioxide composite inert gas injection system continue to be the main technical means to prevent and control spontaneous combustion of coal in the goaf area and coal pillar area of ​​the working face.

[0016] Optionally, the plane projection distance l between the end point of the first group of fire-fighting drilling holes and the contour line of the cutting eye of the working surface1 The second group of fire-fighting drilling holes are located at the top of the tunnel, and the end point overlaps with the plane projection of the center line of the opening eye of the working face. The distance between the end point of the third group of fire-fighting drilling holes and the plane projection of the contour line of the opening eye of the working face is l 3 The fire-fighting holes are spaced m apart in the inclination direction of the working surface. 1 It is 15 to 20 meters.

[0017] Optionally, the diameter of the fire-proof drilling hole is 93mm or 113mm, and the sealer is a mining sealer, which consists of a water injection component, a rubber sealer, a connecting steel pipe, a connecting head, a sealing water supply pipe, and a water injection water supply pipe component, meeting the requirement that the water injection / gas injection pressure is not less than 25MPa.

[0018] Optionally, the components of the inhibitor solution include one or more combinations of sodium chloride, magnesium chloride, calcium hydroxide, etc., and flame retardants and cooling agents are added; the mass fraction of the inhibitor solution is 15% to 20%, the injection pressure is 15 to 25 MPa, the injection flow rate is 120 to 200 L / min, the injection time is 2 to 4 hours, or is determined based on the investigation of coal body occurrence conditions.

[0019] Optionally, the concentration ratio of nitrogen and carbon dioxide composite inert gas is set to 3:7 or 4:6, or determined through experimental tests and simulation studies; the gas injection pressure is 0.5-0.7MPa, the gas injection flow rate is 60-120L / min, and the gas injection time is 2-4h, or determined according to factors such as the spontaneous combustion level of the coal seam, the thickness of the coal seam, the permeability of the coal seam, and the length of the gas pipeline.

[0020] The beneficial effects of the present invention are:

[0021] 1) The technical means and methods of the present invention overcome the drawbacks of using single fire prevention and extinguishing technical means such as grouting and nitrogen injection to prevent coal spontaneous combustion through the coupled inerting mode of gas-liquid two-phase joint injection before mining, realize advanced prevention, active prevention, and multiple protection, and greatly improve the efficiency of coal mine fire prevention and extinguishing;

[0022] 2) Compared with the traditional fire prevention and extinguishing method of spraying inhibitor, the present invention adopts the method of pre-pressing inhibitor solution to fracture and inject the coal body, which increases the external moisture of the coal body, reduces the temperature of the coal body, forms a liquid film to surround the coal block, and absorbs moisture from the air, so that the coal surface is in a wet state for a long time, isolating it from oxygen, and effectively reduces the oxidation rate of the coal body;

[0023] 3) The present invention injects nitrogen and carbon dioxide as a composite inert gas for fire prevention and extinguishing. Nitrogen has a good inertization effect, while carbon dioxide has a higher density and a better cooling effect. The combination of the two can give play to their respective advantages, with higher fire prevention efficiency and lower material cost;

[0024] 4) The method of the present invention provides a new and effective means for solving the problem of spontaneous combustion of coal seams. It can also be used as an active fire prevention and extinguishing technical means and method in the working face withdrawal stage and under the condition of overlying close-range coal seams, and has broad application prospects.

[0025] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0027] Figure 1 This is a flow chart of the active fire prevention by gas-liquid two-phase combined injection coupled inerting before thick coal seam mining according to the present invention.

[0028] Figure 2 This is a plan view of the fire prevention and extinguishing drilling holes in the fully mechanized caving working face of a thick coal seam according to the present invention.

[0029] Figure 3 This is the cross-sectional arrangement diagram of the fire prevention and extinguishing drilling section II of the thick coal seam fully mechanized caving working face of the present invention. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0032] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0033] See also Figure 1 to Figure 3 , which is a method for active fire prevention by gas-liquid two-phase combined injection coupling inerting before thick coal seam mining, comprising the following steps:

[0034] 1. Formulate and implement the process design plan: According to the basic data such as the working face mining design parameters and coal rock occurrence, complete the design of the gas-liquid two-phase combined injection implementation process plan.

[0035] 2. Carry out fire prevention and extinguishing drilling construction: After the mining tunnel of the working face is formed, cut through the working face, construct the first group of fire prevention and extinguishing drilling holes towards the coal body in front of the working face, construct the second group of fire prevention and extinguishing drilling holes towards the coal body above the working face, and construct the third group of fire prevention and extinguishing drilling holes towards the coal body behind the working face; after the drilling construction is completed, use a mining hole sealer to seal the hole.

[0036] The final hole positions of the fire-fighting drilling holes all pass through the full thickness of the extra-thick coal seam to 0.5m above the coal seam roof; the plane projection distance between the final hole points of the first group of fire-fighting drilling holes and the contour line of the cutting eye of the working face is l 1 The second group of fire-fighting drilling holes are located at the top of the tunnel, and the end point overlaps with the plane projection of the center line of the opening eye of the working face. The distance between the end point of the third group of fire-fighting drilling holes and the plane projection of the contour line of the opening eye of the working face is l 3 10~15m; the interval of fire-fighting drilling holes along the inclination direction of the working surface is m 1 It is 15 to 20 meters.

[0037] In addition, in the return air lane of the working face, a fourth set of fire-fighting holes is constructed along the direction of the coal pillar. The distance between the holes and the plane projection of the outer side of the lane outline is l 4 The interval between the boreholes along the working face is 10 to 15 m. 2 5 to 10m.

[0038] The diameter of the fire-fighting drilling hole is 93mm or 113mm; the specific opening position of the drilling hole can be determined based on the actual conditions on site.

[0039] The rubber tube expansion sealing process uses a mining sealer as the sealer, which consists of a water injection component, a rubber sealer, a connecting steel pipe, a connecting head, a sealing water supply pipe, a water injection water supply pipe and other components to meet the requirement that the water injection / gas injection pressure is not less than 25MPa.

[0040] At present, the common sealing methods in coal mines include Marisan sealing, cement mortar sealing and rubber tube expansion sealing. According to the application of engineering, when Marisan is used for sealing, its pressure resistance is generally about 3MPa, and the sealing depth is generally greater than 6m when used for coal body drilling sealing, which is not suitable for the requirements of medium and high pressure water injection for coal seam water injection; when cement mortar is used for sealing, the sealing depth is generally required to be greater than 10m. Affected by the shrinkage of cement mortar after solidification, drilling leakage often occurs, resulting in poor effect of water injection to moisten the coal body; when rubber tube expansion sealing is used, the sealing device has the advantages of high pressure resistance of up to about 30MPa, timely adjustment of sealing depth and reusability. The sealing device has the function of non-interference between the sealing and water injection processes, ensuring that the sealing device will not pop out when the water injection is suddenly unloaded, convenient adjustment of sealing depth and reusability.

[0041] 3. Implementation of the inhibitor solution injection process: After the drilling construction is completed, connect the inhibitor injection system and inject the inhibitor solution into the borehole, so that cracks will appear in the coal body under the action of fracturing. The inhibitor solution penetrates into the gaps in the coal body and fills the cavities and cracks in the coal body, thereby inhibiting and delaying the oxidation of the coal body, and realizing the first level of protection against spontaneous combustion of the coal body.

[0042] During the injection of the inhibitor solution, cracks are generated in the coal body under the action of fracturing, and the inhibitor solution penetrates into the coal body gaps to fill the coal body cavities and cracks. During the mining process of the working face, the coal body collapses, and the inhibitor solution continues to wrap the loose coal body, effectively isolating the air and reducing the oxygen absorption capacity of the coal, thereby preventing the oxidation process of the coal and achieving the purpose of preventing the spontaneous combustion of the coal.

[0043] The inhibitor injection system can be set up as a permanent ground type, a semi-permanent type in the mining area, or a mobile type at the coal mining face, including an injection pool (injection box), an injection pump (boosting pump), a water supply pipeline, an injection pipeline, and other ancillary devices such as pressure gauges and valves.

[0044] The components of the inhibitor solution include one or more combinations of sodium chloride, magnesium chloride, calcium hydroxide, etc., and flame retardants, cooling agents, etc. are added; the mass fraction of the inhibitor solution is 15% to 20%, the injection pressure is 15 to 25 MPa, the injection flow rate is 120 to 200 L / min, the injection time is 2 to 4 hours, or determined based on the investigation of coal body occurrence conditions.

[0045] 4. Implementation of nitrogen and carbon dioxide composite inert gas pressure injection process: After the borehole pressure injection process of the inhibitor solution is completed, the borehole is connected to the nitrogen and carbon dioxide composite inert gas pressure injection system, and nitrogen and carbon dioxide composite inert gas is continued to be injected into the borehole, so that the gas is fully adsorbed and filled in the cracks and voids of the coal body, increasing the external moisture of the coal body while forming a layer of inert gas isolation zone, realizing the second level of protection against spontaneous combustion of the coal body.

[0046] During the mining process at the working face, the coal body collapses, and the nitrogen and carbon dioxide compound inert gas enters the loose coal body gaps, cracks and working face goaf, and is adsorbed on the surface of the coal body cracks to form an isolation layer, which reduces the amount of oxygen adsorbed on the coal body surface and the oxygen concentration in the goaf, avoids direct contact between the coal body and oxygen to cause oxidation heat release, prevents further oxidation and spontaneous combustion of the coal, and thus avoids fire accidents such as spontaneous combustion of the coal body.

[0047] The nitrogen and carbon dioxide composite inert gas pressure injection system includes a gas injection device system, a gas transmission pipeline system and an automatic control system.

[0048] The concentration ratio of nitrogen and carbon dioxide composite inert gas is set to 3:7 or 4:6, or determined through experimental tests and simulation studies; the gas injection pressure is 0.5-0.7MPa, the gas injection flow rate is 60-120L / min, and the gas injection time is 2-4h, or determined based on factors such as the spontaneous combustion level of the coal seam, the thickness of the coal seam, the permeability of the coal seam, and the length of the gas pipeline.

[0049] 5. During the mining process of the fully-mechanized caving working face, the inhibitor injection system and the nitrogen and carbon dioxide composite inert gas injection system can continue to be used as the main technical means to prevent and control spontaneous combustion of coal in the goaf area of ​​the working face and the coal pillar area of ​​the roadway.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for active fire prevention by gas-liquid two-phase combined injection coupling inerting before mining thick coal seams, characterized in that: The following steps are involved: S1, formulate and implement process design plan; According to the working face mining design parameters and coal rock occurrence basic data, complete the design of gas-liquid two-phase combined injection implementation process scheme; S2, conduct fire prevention and extinguishing drilling construction; After the mining tunnel of the working face is formed, the first, second and third groups of fire-fighting drill holes are constructed in the coal bodies in front, above and behind the working face through the cutting holes in the working face, and the fourth group of fire-fighting drill holes are constructed in the return air tunnel of the working face along the coal pillar direction; the final hole positions of all the drill holes pass through the full thickness of the extra-thick coal seam to 0.5m above the coal seam roof, and the holes are sealed with mining hole sealers; S3, implementation of the inhibitor solution injection process; After the drilling construction is completed, the inhibitor injection system is connected to inject the inhibitor solution into the borehole, so that cracks are generated in the coal body under the action of fracturing, and the inhibitor solution penetrates into the coal body gaps, realizing the first level of protection against spontaneous combustion of the coal body; S4, implementation of nitrogen and carbon dioxide composite inert gas pressure injection process; After the borehole injection process of the inhibitor solution is completed, the borehole is connected to the nitrogen and carbon dioxide composite inert gas injection system, and the nitrogen and carbon dioxide composite inert gas is injected into the borehole, so that the gas is fully adsorbed and filled in the cracks and gaps of the coal body, forming a layer of inert gas isolation zone, realizing the second level of protection against spontaneous combustion of the coal body; S5. During the mining process of the fully mechanized caving working face, the inhibitor injection system and the nitrogen and carbon dioxide composite inert gas injection system continue to be the main technical means to prevent and control spontaneous combustion of coal in the goaf area and coal pillar area of ​​the working face.

2. The method for active fire prevention by gas-liquid two-phase combined injection coupling inerting before thick coal seam mining according to claim 1 is characterized in that: The plane projection distance l1 between the end point of the first group of anti-fire extinguishing drilling holes and the contour line of the working face opening is 10 to 15m, the opening point of the second group of anti-fire extinguishing drilling holes is located at the top of the tunnel, and the end point overlaps with the plane projection of the center line of the working face opening; the plane projection distance l3 between the end point of the third group of anti-fire extinguishing drilling holes and the contour line of the working face opening is 10 to 15m; the interval m1 of the anti-fire extinguishing drilling holes along the inclination direction of the working face is 15 to 20m.

3. The method for active fire prevention by gas-liquid two-phase combined injection coupling inerting before thick coal seam mining according to claim 1 is characterized in that: The diameter of the fire-proof drilling hole is 93mm or 113mm, and the sealer is a mining sealer, which consists of a water injection component, a rubber sealer, a connecting steel pipe, a connecting head, a sealing water supply pipe, and a water injection water supply pipe component, meeting the requirement that the water injection / gas injection pressure is not less than 25MPa.

4. The method for active fire prevention by gas-liquid two-phase combined injection coupling inerting before thick coal seam mining according to claim 1 is characterized in that: The components of the inhibitor solution include one or more combinations of sodium chloride, magnesium chloride, calcium hydroxide, etc., and flame retardants and cooling agents are added; the mass fraction of the inhibitor solution is 15% to 20%, the injection pressure is 15 to 25 MPa, the injection flow rate is 120 to 200 L / min, the injection time is 2 to 4 hours, or determined based on the investigation of coal body occurrence conditions.

5. The method for active fire prevention by gas-liquid two-phase combined injection coupling inerting before thick coal seam mining according to claim 1 is characterized in that: The concentration ratio of nitrogen and carbon dioxide composite inert gas is set to 3:7 or 4:6, or determined through experimental tests and simulation studies; the gas injection pressure is 0.5-0.7MPa, the gas injection flow rate is 60-120L / min, and the gas injection time is 2-4h, or determined based on factors such as the spontaneous combustion level of the coal seam, the thickness of the coal seam, the permeability of the coal seam, and the length of the gas pipeline.

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