Low gas mine return air corner gas and coal spontaneous combustion collaborative prevention and control method

Abstract

The application discloses a low-gas mine return air corner gas and coal spontaneous combustion cooperative prevention and control method and belongs to the technical field of coal mine gas prevention and control. First, the unit method is used to identify the gas source of a coal mining working face, and a complex gas inrush area of an old goaf and a key management area of a return air corner are locked. Then, a solidified foam plugging layer is sprayed on the surface of a coal pillar along the gob, inorganic materials are filled in the return air corner by using a three-dimensional bag, and a foam plugging is supplemented to form an isolation wall. The air flow of the working face is regulated by an air inlet end head wind curtain and a return air end head flow guide wind curtain, a telescopic wind curtain is arranged on the middle and rear parts of the return air side, and the telescopic wind curtain and the return air end head flow guide wind curtain realize working condition linkage switching. Finally, the mining rate is controlled in combination with the oxidation zone of the goaf and the coal spontaneous combustion characteristics, and the gas instantaneous inrush is controlled by using the staggered operation of coal cutting and coal releasing. The application does not need to rely on a high-cost gas extraction system, and can simultaneously reduce the gas accumulation overlimit of the return air corner of the low-gas mine and the coal spontaneous combustion risk of the goaf.

Description

Technical Field

[0001] This invention relates to the field of gas control technology, specifically to a method for the coordinated prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine. Background Technology

[0002] my country's coal mines are primarily underground, and with increasing mining depth and intensity, ventilation conditions at the working face, the development of surrounding rock fissures, and the gas migration patterns in the goaf have become more complex, leading to increasingly prominent risks of gas accumulation and spontaneous combustion. For low-gas mines, although their absolute gas emission is usually lower than that of high-gas mines, factors such as roadway retention along the goaf, air leakage in the goaf, unstable airflow organization at the working face end, and switching of mining processes can still cause abnormal gas accumulation, instantaneous exceedances, and oxidation and heating of residual coal in the goaf in localized areas. The return air corners and gas exchange areas on the old goaf side are particularly sensitive locations for compound disasters.

[0003] Existing gas control methods in low-gas mines primarily rely on conventional ventilation and dilution. High-level drilling and dedicated extraction pipelines are generally not the dominant methods due to their high construction and operating costs. Under these conditions, if the local airflow organization at the working face is unreasonable, or if the coal mining machine moves to the end area requiring temporary adjustments to the existing diversion facilities, the return air corner is prone to short-term insufficient diversion, leading to gas accumulation and instantaneous exceedances. Especially under special operating conditions such as at the cutter head, conventional fixed diversion facilities cannot simultaneously meet equipment operation requirements and localized continuous diversion needs, causing the return air corner to become a weak point in gas control during specific periods.

[0004] On the other hand, various air leakage channels commonly exist in goaf areas and along the goaf roadways, such as coal pillar fissures, corner voids, and boundary cracks between the backfill and the surrounding rock. Current technologies for addressing these channels often focus on localized plugging or sealing of single locations, lacking a systematic approach to surface-level seepage channels, volumetric space channels, and boundary crack channels. Therefore, they are insufficient to effectively reduce gas exchange between the goaf and the working face. Once fresh air continuously leaks into the goaf, it may not only induce abnormal migration of gas from the old goaf to the working face but also expand the oxidation zone of residual coal and enhance oxygen supply, thereby increasing the risk of spontaneous combustion. In other words, existing sealing measures still suffer from insufficient specificity and a lack of overall effectiveness in reducing air leakage and oxygen supply and suppressing spontaneous combustion.

[0005] Furthermore, existing technologies typically treat gas control and coal spontaneous combustion prevention as two relatively independent issues, lacking a synergistic control approach that considers the same working face, the same airflow system, and the same leakage channels. For example, simply increasing local airflow can help dilute gas, but if the airflow path is not properly controlled, it may actually increase oxygen supply through goaf leakage; simply strengthening sealing can reduce goaf leakage to some extent, but it is difficult to solve the problem of local flow failure in the return air corner under special working conditions; and relying solely on mining speed control cannot simultaneously take into account the dynamic relationship between instantaneous gas outbursts and the oxidation development of residual coal in the goaf. Therefore, existing technologies lack a systematic and synergistic control method for low-gas mines that takes into account both the prevention and control of gas accumulation in the return air corner and the suppression of coal spontaneous combustion in the goaf.

[0006] In summary, existing technologies have at least the following shortcomings: First, low-gas mines lack a highly efficient local gas control method that does not rely on high-cost extraction systems; second, there is a lack of multi-layered composite sealing methods for air leakage channels such as coal pillar pores and fissures, corner volumes, and boundary cracks, making it difficult to simultaneously block gas migration and reduce oxygen supply to the goaf; third, for special mining conditions such as cutter heads, existing diversion facilities cannot achieve continuous and stable dilution of return air corners; fourth, existing measures fail to organically combine air leakage sealing, airflow control, and mining rhythm control, making it difficult to achieve coordinated prevention and control of return air corner gas and coal spontaneous combustion risks. Therefore, it is necessary to propose a method for coordinated prevention and control of return air corner gas and coal spontaneous combustion applicable to low-gas mines. Summary of the Invention

[0007] The purpose of this invention is to provide a method for the coordinated prevention and control of gas and spontaneous combustion of coal in the return air corner of low-gas mines. This method aims to solve the complex disaster problem of excessive gas accumulation and spontaneous combustion of coal in the return air corner of low-gas mines under special working conditions such as the cutting machine head. Through the integrated design of leak sealing, airflow guidance and control and operation rhythm management, the method can simultaneously achieve efficient dilution of gas in the return air corner and suppression of the risk of spontaneous combustion of coal in the goaf, thereby improving the safety and economy of mining in low-gas mines.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a method for the coordinated prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine, comprising the following steps:

[0009] Step S1: Identify the gas sources in the coal mining face, and determine the complex gas inrush area in the old goaf and the key treatment area in the return air corner;

[0010] Step S2: For the complex gas influx area of ​​the old goaf, spray a solidified foam sealing layer on the coal pillar surface on the side of the goaf-side roadway close to the old goaf to reduce the gas exchange between the complex gas in the old goaf and the fresh air flow of the working face.

[0011] Step S3: Set up three-dimensional bags at the air intake corner and the return air corner along the direction of the roof cutting line of the working face, and fill the three-dimensional bags with inorganic filling material to form filling bags, so that the filling bags are in contact with the roof, coal wall and goaf collapse wall;

[0012] Step S4: Spray curing foam around the filling bag to seal the gaps between the filling bag and the roof, coal wall and goaf collapse wall to form an isolation wall to block air leakage and gas migration in the goaf.

[0013] Step S5: Install an air inlet end guide curtain in front of the air inlet side isolation wall to restrict the airflow from entering the air inlet corner and direct the air volume to the working face; install a return air end guide curtain on the return air end bracket to guide the airflow from the working face into the return air corner.

[0014] Step S6: Install a retractable air curtain at the middle and rear support position on the return air side. Under normal coal cutting conditions, the retractable air curtain is in a retracted state.

[0015] Step S7: When the coal mining machine runs to the predetermined section at the head end of the return air side, switch the return air end guide curtain to the retractable state and unfold the retractable curtain to guide the airflow of the working face to the inlet of the retracted return air end guide curtain and introduce it into the return air corner, thereby maintaining the continuous dilution of the return air corner under the working condition of the cutter head.

[0016] Step S8: After the coal mining machine leaves the predetermined area, restore the unfolded guiding state of the return air end guide curtain and retract the retractable air curtain.

[0017] Step S9: Control the mining rate based on the width of the oxidation zone in the goaf, the spontaneous combustion period of coal, and the construction efficiency of the isolation wall, and control the instantaneous gas outburst rhythm by staggering coal cutting and coal release operations.

[0018] As a further improvement of the present invention, in step S1, the gas source identification is carried out using the unit method. The working face is divided into several continuous units along the airflow direction of the working face. Each unit corresponds to 5-15 hydraulic supports. The units where the air intake corner and the air return corner are located also include the predetermined roadway range in front of the coal roadway before entering the working face. Each unit's air intake section and air outlet section are respectively set with goaf side measuring points, sidewalk measuring points and coal wall side measuring points. The coal roadway section is determined with three measuring points in the horizontal direction of the section to measure the gas concentration, wind speed and air volume. Based on the air volume balance and gas balance, the gas emission volume of the goaf and the gas emission volume of the coal wall, roof and floor and falling coal are determined.

[0019] As a further improvement of the present invention, in step S2, the solidified foam sealing layer on the surface of the coal pillar is mainly sprayed on the thin coal pillar area, and the spraying thickness is not less than 5 cm.

[0020] As a further improvement of the present invention, in step S3, the three-dimensional bag is made of polypropylene, with its top suspended from the top plate by a hanging nose, and its left and right sides fixed to the coal wall and the goaf collapse wall, respectively.

[0021] As a further improvement of the present invention, in step S4, at least one isolation wall is provided at approximately 5 m intervals between the air inlet corner and the air return corner.

[0022] As a further improvement of the present invention, in step S5, the return air end guide curtain is fixed to the front beam and column of the hydraulic support, and extends along the direction of the sidewalk before being set towards the return air corner, so as to introduce the airflow of the working face into the return air corner.

[0023] As a further improvement of the present invention, in step S6, the retractable air curtain is positioned at the 15th-20th hydraulic support position on the return air side.

[0024] As a further improvement of the present invention, in step S7, when the coal mining machine runs to the vicinity of the 10th hydraulic support on the return air side, the return air end guide curtain is switched to the retracted state, and the retractable curtain is switched from the retracted state to the extended state.

[0025] As a further improvement of the present invention, in step S7, the retractable air curtain extends to the front side of the front beam of the hydraulic support after being unfolded, and is used to guide the airflow of the working face to the inlet of the return air curtain in the withdrawn state.

[0026] As a further improvement of the present invention, in step S9, the staggered operation of coal cutting and coal release includes a preset time interval between coal cutting and coal release, and prohibits coal cutting and coal release from being carried out simultaneously, so as to reduce the instantaneous gas outburst.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] 1. This invention seals the coal pillar pores, corner volume space, and surrounding gaps by spraying cured foam onto the surface of the coal pillar in the old goaf, setting up filling bags at the corners, and spraying cured foam around them to form an isolation wall. This reduces gas exchange between the goaf and the working face, minimizes air leakage, and suppresses the risk of spontaneous combustion of coal. 2. This invention utilizes the switching and coordination between the return air end guide curtain and the retractable air curtain. Even when the return air end guide curtain must be removed due to the shearing machine head, continuous dilution and dilution of gas can still be maintained in the return air corner, reducing the risk of short-term gas accumulation and instantaneous exceedance. 3. This invention is suitable for low-gas mines with limited extraction conditions. It can achieve the coordinated implementation of return air corner gas control and goaf coal spontaneous combustion prevention without relying on a high-cost extraction system. Attached Figure Description

[0029] Figure 1This is a flowchart of the method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine, as described in this invention.

[0030] Figure 2 This is a schematic diagram showing the division of the gas source analysis unit in this invention;

[0031] Figure 3 This is a schematic diagram of the gas source analysis test section of the present invention, wherein the left figure is the test section of the working face and the right figure is the test section of the coal roadway;

[0032] Figure 4 This is a schematic diagram of the working face air curtain diversion and leakage sealing method of the present invention; the left diagram shows the coal mining machine not in the head position, and the right diagram shows the coal mining machine in the head position;

[0033] Figure 5 This is a schematic diagram of the retractable air curtain structure of the present invention.

[0034] Explanation of reference numerals in the attached diagram: 1-Goaf; 2-Unit; 3-Measuring point cross-section; 4-Intake airway; 5-Airflow direction; 6-Return airway; 7-Intake corner isolation wall; 8-Intake corner; 9-Intake end guide curtain; 10-Walking walkway; 11-Hydraulic support; 12-Return corner; 13-Return corner isolation wall; 14-Retractable curtain; 14-1-Curtain; 14-2-Folding rib; 14-3-Slide rail; 14-4-Hanging ring; 14-5-Pulley; 14-6-Wire rope; 14-7-Fixed section; 15-Coal mining machine; 16-Coal pillar; 17-Return end guide curtain; 18-Guidance direction. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0036] like Figures 1-4 As shown, the present invention provides a method for the coordinated prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine, comprising the following steps:

[0037] Step S1: Identify the gas sources in the coal mining face, determining the complex gas inflow areas in the old goaf and the key treatment areas in the return air corners. Specifically, the gas source identification is performed using a unit method, such as... Figure 2As shown, starting from the intake airway 4, along the airflow direction 5 of the working face (airflow exits from the return airway 6), the entire working face is divided into several continuous units 2. Generally, 5-15 hydraulic supports 11 constitute one unit 2. The unit containing the intake and return air corners includes the 15 m section of the roadway before the coal roadway enters the working face and the first 5-10 hydraulic supports 11 just entering the working face, ensuring that the intake and return air corners of the working face are included in the first and last units, respectively. The boundaries of each unit are marked with the hydraulic support 11 numbers, and the interval length of each unit is determined according to the actual conditions of the working face.

[0038] The hydraulic supports 11 at both ends of each unit serve as the test positions for the air inlet and outlet sections of that unit, respectively, i.e., test point sections 3. These are located near the goaf 1, the walkway 10, and the coal face. Figure 3 As shown, three measuring points (1#, 2#, and 3#) were set up at each cross-section. The gas concentrations (c1) in the goaf, (c2) in the walkway, and (c3) beside the coal wall were measured using a portable gas detector or sampling analysis. An anemometer was used at measuring point 2# to measure the airflow velocity at each test cross-section. The airflow volume entering and exiting each unit was calculated based on the cross-sectional area. After obtaining the gas concentrations at each measuring point, the gas emission volume from the top and bottom of the coal wall and from falling coal, as well as the gas emission volume in the goaf, were determined according to the gas-airflow balance of each unit. The main sources of gas emission were further analyzed.

[0039] Gas volume balance equation:

[0040]

[0041] In the formula, This represents the amount of gas entering (or leaving) each unit from the goaf. A positive value indicates the amount of gas entering the unit, while a negative value indicates the amount of gas flowing into the goaf. This refers to the gas emission from the top and bottom of the coal wall and the coal falling within each unit. The air volume flowing into each unit, To determine the airflow volume of each unit, both calculations are based on the wind speed test results at measuring point #2 of each test section. This represents the leakage air volume flowing into (out of) each unit from the goaf. A positive value indicates the air volume flowing into the unit, while a negative value indicates the leakage air volume flowing into the goaf. The methane concentration in the leaking airflow in the goaf is calculated based on the methane concentration test results at measuring point 1 of each test section. The concentration of methane gas flowing into the airflow of each unit. To determine the methane concentration in the airflow of each unit, both measurements were calculated based on the methane concentration test results at measuring point #2 of each test section.

[0042] The actual measured gas concentration and air volume are substituted into the gas air volume balance equation to calculate the amount of gas entering (or leaving) each unit in the goaf. and the gas emission from the top and bottom of the coal wall and the coal falling within each unit. It can analyze the sources and proportions of gas within a unit, determine key areas for gas prevention and control, and judge the lateral diffusion of gas from the coal face to the goaf based on c1, c2 and c3 measured at the unit's entry and exit sections. At the same time, it can verify the accuracy of the results calculated by the unit method.

[0043] Step S2: For the complex gas influx area of ​​the old goaf, a solidified foam sealing layer is sprayed onto the surface of coal pillar 16 on the side of the goaf-side roadway closest to the old goaf to reduce gas exchange between the complex gas in the old goaf and the fresh airflow from the working face. The solidified foam sealing layer on the surface of coal pillar 16 is mainly sprayed on the thin coal pillar area, with a spray thickness of not less than 5 cm.

[0044] Step S3: Install three-dimensional bags along the roof-cutting line at the intake air corner 8 and return air corner 12, and fill the bags with inorganic filling material to form filling bags that adhere to the roof, coal face, and goaf collapse wall. The three-dimensional bags are made of polypropylene, with their tops suspended from the roof via hooks, and their left and right sides fixed to the coal face and goaf collapse wall, respectively. The inorganic filling material is a two-liquid inorganic filling material, which is mixed by a mine slurry mixer and then injected into the three-dimensional bags by an electric two-liquid grouting pump.

[0045] Step S4: Spray curing foam around the filling bag to seal the gaps between the filling bag and the roof, coal wall, and goaf collapse wall, thus forming an isolation wall to block air leakage and gas migration in the goaf, namely, the intake corner isolation wall 7 and the return corner isolation wall 13. At least one isolation wall shall be set at approximately 5 m intervals between the intake corner 8 and the return corner 12.

[0046] In steps S2, S3, and S4, step S2 addresses the planar air leakage problem caused by pores and fissures on the coal pillar surface by spraying cured foam onto the coal pillar surface; step S3 addresses the volumetric air leakage problem in the corner area by setting up three-dimensional bag-filled packs; and step S4 addresses the boundary gap air leakage problem between the filling packs and the roof, coal wall, and goaf collapse wall by spraying cured foam around the filling packs again, thereby achieving a composite sealing of planar air leakage, volumetric air leakage, and boundary gap air leakage. Furthermore, the composite sealing system formed by steps S2 to S4 not only blocks the migration of complex gases from the old goaf to the working face but also reduces the leakage supply of fresh air from the working face to the goaf. Since the spontaneous oxidation of residual coal in goaf areas, which can further develop into spontaneous combustion, is usually closely related to continuous air leakage and oxygen supply, the expansion of the oxidation zone, and the excessive duration of oxidation, this invention systematically weakens the planar, volumetric, and boundary gap air leakage channels between the goaf and the working face through the synergistic implementation of foam sealing on the coal pillar surface, corner three-dimensional bag filling, and resealing of surrounding gaps. This reduces the oxygen supply conditions of residual coal in the goaf from the source, inhibits the development of the oxidation zone, and thus reduces the risk of spontaneous combustion of coal. Therefore, the sealing measures in this invention serve both the control of return air corner gas and the prevention and control of spontaneous combustion of coal in the goaf, forming an important foundation for the entire synergistic prevention and control method.

[0047] Step S5: Install an air inlet guide curtain 9 in front of the air inlet side isolation wall to restrict airflow into the air inlet corner 8 and direct airflow towards the working face; install a return air guide curtain 17 on the return air side support to guide the airflow from the working face into the return air corner 12. The return air guide curtain 17 is fixed to the front beam and column of the hydraulic support 11, extends along the direction of the walkway 10 and then faces the return air corner 12 to introduce the airflow from the working face into the return air corner 12. Figure 4 The center displays the airflow direction as 18.

[0048] Step S6: Install a retractable air curtain 14 at the rear support position on the return air side. Under normal coal cutting conditions, the retractable air curtain 14 is in a retracted state. The retractable air curtain 14 is installed at the 15th-20th hydraulic support positions on the return air side. The 15th-20th support positions can form an effective supplementary airflow without affecting the passage of equipment.

[0049] like Figure 5As shown, the retractable air curtain 14 includes an air curtain 14-1, a slide rail 14-3, and pulleys 14-5. The slide rail 14-3 is fixed to the top beam of the hydraulic support. The air curtain 14-1 is made of mine-grade flame-retardant and anti-static coated fabric, which is a flexible material. Rigid folding ribs 14-2 are provided on the air curtain 14-1 to facilitate folding and unfolding. A row of hanging holes is provided horizontally at the top of the air curtain, and hanging rings 14-4 are passed through the hanging holes and fitted onto the slide rail 14-3. A pulley 14-5 is fixedly installed at each end of the slide rail 14-3, and a steel wire rope 14-6 is connected to the two pulleys 14-5. A hole sleeve is provided horizontally on the air curtain, through which the steel wire rope 14-6 passes. A fixing section 14-7 (such as a steel buckle) is provided at the upper left corner of the air curtain 14-1 to fix the air curtain 14-1 and the steel wire rope 14-6 together. When the retractable air curtain 14 retracts, pulling the right-side wire rope 14-6 causes the fixed section 14-7 to secure the wire rope 14-6 to the air curtain 14-1. Pulling the wire rope 14-6 downwards moves the air curtain 14-1 from left to right, causing the rigid folding ribs 14-2 to slowly converge and gather to the right. The hanging ring 14-4 slides freely on the slide rail 14-3, and the air curtain retracts to the right. When it needs to be unfolded, pulling the left-side wire rope 14-6 slowly pulls the air curtain back from the right. In this embodiment, the rigid folding ribs 14-2 facilitate the retraction of the air curtain and increase its rigidity during unfolding, preventing it from swaying back and forth. The retractable air curtain 14 of this invention has a simple structure, is very convenient to use, and is particularly suitable for wind protection and guidance on work surfaces, with very quick retraction and unfolding.

[0050] Step S7: When the coal mining machine 15 reaches the predetermined section at the head end of the return air side, the return air end guide curtain 17 is switched to the retracted state, and the retractable curtain 14 is deployed to guide the airflow from the working face to the inlet of the retracted return air end guide curtain 17, and through it, into the return air corner 12, thereby maintaining continuous airflow dilution at the return air corner 12 under the cutting head condition. The cutting head condition refers to the process in a fully mechanized coal mining face where the coal mining machine travels to the end of the scraper conveyor near the transport roadway (head / coal outlet end), thoroughly cutting through and leveling the triangular coal and residual coal wall in the head area, completing the coal cutting operation at the end position. This process is called the cutting head in the coal mine. Specifically, when the coal mining machine reaches the vicinity of the 10th hydraulic support on the return air side, the return air end guide curtain 17 is switched to the retracted state, and the retractable curtain 14 is switched from the retracted state to the deployed state. The area near the 10th unit is where the return air end guide curtain 17 must be switched and where the corner gas is most sensitive. The retractable air curtain 14 extends to the front side of the hydraulic support front beam after being deployed, and is used to guide the airflow at the working face to the inlet of the return air end guide curtain when it is in the withdrawn state.

[0051] Step S8: After the coal mining machine leaves the predetermined area, restore the unfolded and guide state of the return air end guide curtain, and retract the retractable air curtain.

[0052] After the sealing system is completed, steps S5 to S8 further focus on the airflow organization at the working face, and construct a coordinated airflow control mechanism of "static guidance + dynamic adjustment + working condition linkage": In step S5, by setting up windbreak curtains on the air intake side and guiding air curtains on the return air side, the airflow at the working face is initially allocated and guided, so as to realize the effective supply of airflow to the working face and enhance the guiding capacity to the return air corner, and establish a basic guiding structure.

[0053] In step S6, a retractable air curtain is installed at the rear of the return air side. Under normal coal cutting conditions, it remains retracted to avoid interfering with equipment operation and passage, and also serves as a backup flow control unit. In step S7, when the coal mining machine reaches the predetermined section at the head end of the return air side, the original flow path is disrupted because the return air end guide curtain needs to be temporarily removed. At this time, by deploying the retractable air curtain, the airflow from the working face is redirected to the return air corner, forming an alternative flow path. This achieves dynamic reconfiguration of the flow control system, thus maintaining continuous ventilation and gas dilution in the return air corner even under adverse conditions. In step S8, after the coal mining machine leaves this critical section, the return air end guide curtain is restored and the retractable air curtain is retracted, allowing the flow control system to return to normal operation.

[0054] Step S9: Control the mining rate based on the width of the oxidation zone in the goaf, the spontaneous combustion period of coal, and the construction efficiency of the isolation wall, and control the instantaneous gas outburst rhythm by staggering coal cutting and coal release operations. The staggered coal cutting and coal release operations include setting a time interval between coal cutting and coal release, and prohibiting coal cutting and coal release from being carried out simultaneously, in order to reduce the instantaneous gas outburst.

[0055] This invention combines the mining rhythm control in step S9 to form a comprehensive prevention and control system integrating structural control (blocking), flow field control (diversion), and time control (operation rhythm).

[0056] Based on field application verification, and on the basis of effectively suppressing air leakage and complex gas exchange in the goaf by constructing the foam sealing layer on the coal pillar surface, the three-dimensional bag filling bag and the surrounding foam sealing isolation wall in steps S2 to S4, and combined with the basic airflow guidance and control structure formed by the inlet and return air curtains set in step S5, the air curtain linkage control method described in steps S6 to S8 was compared and tested.

[0057] Under the cutting head condition: When only the return air end guide curtain is used for air diversion, the original guide path is interrupted because the guide curtain needs to be temporarily removed when the coal mining machine runs to the return air end area. The return air corner is in a state of guide failure for a short time. The measured peak gas concentration in the return air corner can reach 0.7% to 1.2%, and the duration of the exceedance is 80 to 120 seconds. There are 1 to 2 exceedances in a single cycle, and it takes 60 to 90 seconds for the gas concentration to recover to the safe range.

[0058] Based on this, the linkage switching measures of the retractable air curtain and the return air end guide air curtain described in steps S6 to S8 are further adopted. When the coal mining machine runs to the predetermined interval, the retractable air curtain is deployed to replace the guide path. Under the same sealing and ventilation conditions, the peak gas concentration in the return air corner is reduced to 0.4% to 0.7%, and no gas exceedance phenomenon occurs. Moreover, the concentration recovery time is shortened to 10 to 20 seconds.

[0059] The above results show that the multi-dimensional sealing system formed by steps S2 to S4 reduces air leakage and abnormal gas supply in the goaf, providing stable boundary conditions for airflow control. At the same time, the air curtain linkage diversion mechanism constructed by steps S5 to S8 realizes dynamic reconstruction of the diversion path under different working conditions, ensuring continuous and effective ventilation in the return air corner.

[0060] The synergistic effect of the two enables the present invention to simultaneously reduce the risk of gas accumulation in the return air corner and the risk of spontaneous combustion of coal in the goaf without relying on the gas extraction system, thus significantly improving the prevention and control of complex disasters in low-gas mines.

[0061] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. A method for the coordinated prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine, characterized in that, Includes the following steps: Step S1: Identify the gas sources in the coal mining face, and determine the complex gas inrush area in the old goaf and the key treatment area in the return air corner; Step S2: For the complex gas influx area of ​​the old goaf, spray a solidified foam sealing layer on the coal pillar surface on the side of the goaf-side roadway close to the old goaf to reduce the gas exchange between the complex gas in the old goaf and the fresh air flow of the working face. Step S3: Set up three-dimensional bags at the air intake corner and the return air corner along the direction of the roof cutting line of the working face, and fill the three-dimensional bags with inorganic filling material to form filling bags, so that the filling bags are in contact with the roof, coal wall and goaf collapse wall; Step S4: Spray curing foam around the filling bag to seal the gaps between the filling bag and the roof, coal wall and goaf collapse wall to form an isolation wall to block air leakage and gas migration in the goaf. Step S5: Install an air inlet end guide curtain in front of the air inlet side isolation wall to restrict the airflow from entering the air inlet corner and direct the air volume to the working face; install a return air end guide curtain on the return air end bracket to guide the airflow from the working face into the return air corner. Step S6: Install a retractable air curtain at the middle and rear support position on the return air side. Under normal coal cutting conditions, the retractable air curtain is in a retracted state. Step S7: When the coal mining machine runs to the predetermined section at the head end of the return air side, switch the return air end guide curtain to the retractable state and unfold the retractable curtain to guide the airflow of the working face to the inlet of the retracted return air end guide curtain and introduce it into the return air corner, thereby maintaining the continuous dilution of the return air corner under the working condition of the cutter head. Step S8: After the coal mining machine leaves the predetermined area, restore the unfolded guiding state of the return air end guide curtain and retract the retractable air curtain. Step S9: Control the mining rate based on the width of the oxidation zone in the goaf, the spontaneous combustion period of coal, and the construction efficiency of the isolation wall, and control the instantaneous gas outburst rhythm by staggering coal cutting and coal release operations.

2. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S1, the gas source identification is performed using a unit method. The working face is divided into several continuous units along the airflow direction. Each unit corresponds to 5-15 hydraulic supports. The units where the air intake corner and return corner are located also include the predetermined roadway range before the coal roadway enters the working face. Each unit's air intake section and air outlet section are respectively equipped with goaf side measuring points, walkway measuring points, and coal wall side measuring points. The coal roadway section is determined with three measuring points in the horizontal direction of the section to measure gas concentration, wind speed, and air volume. Based on the air volume balance and gas balance, the gas emission volume in the goaf, as well as the gas emission volume in the coal wall, roof and floor, and falling coal are determined.

3. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S2, the solidified foam sealing layer on the surface of the coal pillar is sprayed mainly on the thin coal pillar area, and the spraying thickness is not less than 5 cm.

4. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S3, the three-dimensional bag is made of polypropylene, with its top suspended from the roof plate by a hanging nose, and its left and right sides fixed to the coal wall and the goaf collapse wall, respectively.

5. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S4, at least one isolation wall is installed at approximately 5 m intervals between the air inlet corner and the air return corner.

6. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S5, the return air end guide curtain is fixed to the front beam and column of the hydraulic support, and extends along the sidewalk direction before being set towards the return air corner, so as to introduce the airflow from the working face into the return air corner.

7. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S6, the retractable air curtain is positioned at the 15th-20th hydraulic support position on the return air side.

8. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S7, when the coal mining machine runs to the vicinity of the 10th hydraulic support on the return air side, the return air end guide curtain is switched to the retracted state, and the retractable curtain is switched from the retracted state to the extended state.

9. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 8, characterized in that, In step S7, the retractable air curtain extends to the front side of the hydraulic support front beam after being unfolded, and is used to guide the airflow of the working face to the inlet of the return air curtain in the retracted state.

10. The method for synergistic prevention and control of gas and spontaneous combustion of coal in the return air corner of a low-gas mine according to claim 1, characterized in that, In step S9, the staggered operation of coal cutting and coal release includes setting a time interval between coal cutting and coal release, and prohibiting coal cutting and coal release from being carried out simultaneously, so as to reduce the instantaneous gas outburst.

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