System and method for preventing spontaneous combustion of floating coal in goaf

Abstract

A system and method for preventing and treating spontaneous combustion of floating coal in goaf, the system: the filling pipeline is arranged on one side of the roadway in the working face; a plurality of branch pipelines are connected to the filling pipeline in sequence; the water-soluble plug is composed of a gland, a water-soluble sealing ring and a circular baffle, the gland is composed of a sleeve and a limiting ring, an annular mounting groove is arranged in the right end of the sleeve; the limiting ring is fixed to the inside of the right end of the sleeve; the water-soluble sealing ring is installed in the annular mounting groove, an annular positioning step is arranged on the left side of the inside of the water-soluble sealing ring; the circular baffle is installed in the annular positioning step. The method: the water-soluble plug is installed when the branch pipeline on the front side enters the corner of the working face, the water-soluble plug is opened in a set time by the action of water to inject slurry or nitrogen into the goaf. The system and method can conveniently realize uninterrupted grouting or nitrogen injection operation, and effectively solve the problem of large pipeline consumption in the existing coal mine goaf fire prevention and extinguishing technology.

Description

Technical Field

[0001] This invention belongs to the field of coal mining technology, specifically relating to a system and method for preventing spontaneous combustion of floating coal in goaf areas. Background Technology

[0002] After coal mining, numerous goaf areas are created, leaving behind large amounts of loose coal. Due to coal's spontaneous combustion properties, under conditions of adequate ventilation, oxygen supply, and heat storage, this loose coal is prone to spontaneous combustion. Spontaneous combustion in coal mine goaf areas is extremely dangerous, potentially causing mine fires, significant property damage, and even serious safety accidents resulting in casualties.

[0003] Current coal mine goaf fire prevention and extinguishing technologies mainly involve injecting preventative grout or fire inhibitors. Injecting preventative grout is a passive fire prevention and extinguishing method, requiring the laying of grouting pipelines in the working face roadway, typically in the return airway (commonly known as the return air roadway). As the working face advances, the end of the grouting pipeline gradually enters the goaf. Grouting operations begin when the pipeline's opening has penetrated a certain distance into the goaf. As the working face advances to the grouting location, grouting operations cease, and the grouting pipeline is disconnected at the return air corner, forming a new grouting pipeline end. As the working face continues to advance, grouting operations resume when the new grouting pipeline end extends a certain distance into the goaf. For mines with severe spontaneous combustion, continuous grouting operations are required in the goaf to ensure the effectiveness of grouting for fire prevention and extinguishing. Because the distance between the grouting port in the goaf and the working face must be maintained within a certain range, such as 20m to 40m, the position of the end of the grouting pipeline within the goaf must always be within this range. To meet the requirements of both continuous grouting and ensuring that the position of the end of the grouting pipeline within the goaf remains within this range, mines typically employ a method of alternating grouting with two grouting pipelines. Figure 1 As shown, two grouting pipes 17 are laid parallel in the working face roadway 4. Each grouting pipe 17 is disconnected at a corner every 40m, forming a cut-off grout outlet 18. The distance between adjacent disconnection points of the two grouting pipes 17 is 20m. Thus, when one grouting pipe 17 extends 40m into the goaf 3, the system switches to the other grouting pipe 17 to begin grouting from 20m down, repeating this switching process to achieve uninterrupted grouting. However, due to the large area and complex internal conditions of the goaf, problems such as grouting failing to reach the ignition point or grouting pipe blockage can easily occur, leading to the failure of fire prevention and extinguishing operations. While using fire inhibitors for fire prevention and extinguishing can effectively suppress the spontaneous combustion of residual coal in the goaf, the existing technology involves a complex system structure for injecting fire inhibitors, resulting in high costs and significantly increasing the cost of mine fire prevention and extinguishing operations.

[0004] In view of the current situation where existing goaf fire prevention and extinguishing technologies suffer from problems such as high pipeline consumption, large installation workload, frequent switching, heavy workload for operators, and poor practical application effect, there is an urgent need to provide a system and method that can effectively prevent spontaneous combustion of floating coal in goaf areas, so as to effectively improve the safety of mine production operations. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a system and method for preventing spontaneous combustion of floating coal in goaf areas. This system requires minimal operation and maintenance, and can easily achieve uninterrupted grouting or nitrogen injection operations. It effectively solves the problem of high pipeline consumption in existing coal mine goaf fire prevention and extinguishing technologies, while also significantly reducing pipeline installation workload and the labor load of workers. This method is simple to implement, requires minimal operation and maintenance, has good economic benefits, and high injection efficiency. It effectively ensures safe production operations in coal mines and improves the safety factor for coal miners, making it suitable for widespread application.

[0006] To achieve the above objectives, the present invention provides a system for preventing spontaneous combustion of floating coal in goaf areas, comprising an injection pipeline, a bypass pipeline, and a water-soluble plug.

[0007] The injection pipeline is laid or hoisted on one side of the roadway in the working face roadway;

[0008] Multiple branch lines are evenly distributed along the length of the injection line on the same side, and the inlet end of each branch line is connected to the injection line in a continuous manner. A control valve is installed in the middle of each branch line, and an external thread structure is provided on the outside of the outlet end of each branch line. The branch lines are used to transport slurry or nitrogen in the injection line to the goaf.

[0009] Multiple water-soluble plugs are correspondingly installed for each of the multiple branch pipes. Each water-soluble plug consists of a gland, a water-soluble sealing ring, and a circular baffle. The gland is composed of a sleeve and a limiting ring. The sleeve has an annular mounting groove on its right end and an internal thread structure on the left side of the annular mounting groove. The sleeve is then fixedly fitted onto the outside of the branch pipe outlet through the threaded connection. The limiting ring is coaxially fixedly connected to the inside of the right end of the sleeve. The water-soluble sealing ring is made of water-soluble material and is fitted into the annular mounting groove. Its inner diameter is smaller than that of the limiting ring. An annular positioning step is provided on the left side of the interior of the water-soluble sealing ring. The inner diameter of the annular positioning step is smaller than that of the limiting ring. The circular baffle is fitted to the annular positioning step and is fixedly installed within it.

[0010] As a preferred option, the distance between two adjacent branch pipes is 40m.

[0011] In this invention, by uniformly connecting multiple branch pipes along the length of the filling pipeline, it is convenient to use multiple branch pipes as grouting ports or nitrogen injection ports sequentially during the advancement of the working face. This allows for switching between different grouting port or nitrogen injection port positions without cutting off the filling pipeline, greatly improving the convenience of the filling process, significantly reducing the workload of operators, and increasing the safety factor of the operation. An external thread structure is provided on the outer side of the outlet end of each branch pipe, facilitating the assembly of plugs through threaded engagement, thereby improving the convenience of plug assembly and effectively ensuring the reliability and stability of the assembled plugs. The cap of the water-soluble plug consists of a sleeve and a limiting ring, with an annular mounting groove inside the right end of the sleeve and an internal thread structure on the left side of the annular mounting groove. This facilitates the assembly of the cap on the outer side of the branch pipe outlet end through threaded engagement, and also facilitates the use of the annular mounting groove to limit the installation of the water-soluble sealing ring. An annular positioning step is provided on the left side of the interior of the water-soluble sealing ring, and a circular baffle is installed in the annular positioning step. This allows the circular baffle, in conjunction with the water-soluble sealing ring, to effectively seal the through-hole area inside the limiting ring, thus creating a closed structure for the water-soluble plug. The water-soluble sealing ring is made of a water-soluble material, so that when water comes into contact with the sealing ring for a certain period, it automatically dissolves. This allows the water-soluble sealing ring to automatically detach from the annular mounting groove without operator intervention. Because the outer diameter of the circular baffle is smaller than the inner diameter of the limiting ring, after the water-soluble sealing ring dissolves, the circular baffle can be quickly ejected from the limiting ring under the impact of the internal slurry or nitrogen gas. This allows the slurry or nitrogen gas from the injection pipeline to be smoothly injected into the goaf through the connected branch pipeline. By connecting a control valve in series on each branch pipe, the on / off state of the branch pipe can be easily controlled by the action of the control valve, thus allowing a water-soluble plug to be installed at the outlet end of the branch pipe without stopping the injection.

[0012] This invention achieves completely uninterrupted grouting or nitrogen injection operations by simply installing one injection pipeline on one side of the roadway in the working face. Compared to the traditional method of using two injection pipelines for alternating grouting, pipeline consumption is reduced by approximately 50%, and the corresponding pipeline installation and maintenance workload is also reduced by approximately 50%. Because the water-soluble plug automatically opens after a set time of water action, the predetermined grouting or nitrogen injection operations can be achieved relatively automatically during the synchronous advancement of the working face, significantly improving the automation level of the injection operation. This system requires minimal operation and maintenance, conveniently achieving uninterrupted grouting or nitrogen injection operations, effectively solving the problem of high pipeline consumption in existing coal mine goaf fire prevention and extinguishing technologies. Simultaneously, it effectively reduces pipeline installation workload and the labor load of operators.

[0013] This invention also provides a method for preventing spontaneous combustion of floating coal in goaf areas, employing a system for preventing spontaneous combustion of floating coal in goaf areas, comprising the following steps:

[0014] Step 1: Install a filling pipeline in the working face roadway and connect the inlet end of the filling pipeline to the pulping station;

[0015] Step 2: Connect a branch pipe along the length of the filling pipeline at predetermined intervals on one side, with a control valve connected in series on each branch pipe.

[0016] Step 3: Install a sealing plug at the outlet end of each branch pipe to seal it, and close the control valve on each branch pipe;

[0017] Step 4: Prepare the slurry using a slurry preparation station and continuously transport the prepared slurry to the injection pipeline;

[0018] Step 5: As the fully mechanized mining face advances, when the side branch pipeline on the front side reaches the corner of the working face, first ensure that the control valve on the side branch pipeline is closed, then remove the sealing plug on the side branch pipeline, then install a water-soluble plug at the outlet end of the side branch pipeline, and finally open the control valve on the side branch pipeline.

[0019] Step Six: The slurry in the injection pipeline acts on the water-soluble sealing ring. After a set time, the water-soluble sealing ring dissolves and falls off from the annular mounting groove. Under the impact of the slurry, the circular baffle, which has lost the positioning support of the annular mounting groove, automatically disengages from the limiting ring. At this time, the outlet end of the side branch pipeline changes from a closed state to a conductive state, forming a grouting port. Simultaneously, after a set time, the fully mechanized mining face advances to a set distance in front of the grouting port, and the slurry inside the injection pipeline flows out from the limiting ring and enters the newly formed goaf.

[0020] Step 7: As the fully mechanized mining face advances, when the next branch pipeline reaches the corner of the working face, first ensure that the control valve on the branch pipeline is closed, then remove the sealing plug on the branch pipeline, then install a water-soluble plug at the outlet end of the branch pipeline, and finally open the control valve on the branch pipeline.

[0021] Step 8: The slurry in the injection pipeline acts on the water-soluble sealing ring. After a set time, the water-soluble sealing ring dissolves and falls out of the annular mounting groove. Under the impact of the slurry, the circular baffle is automatically pushed out from inside the limiting ring. At this time, the outlet end of the side branch pipeline changes from a closed state to a conductive state. The side branch pipeline at this position forms a conveying path with a shorter stroke and less resistance, replacing the previous grouting port to form a new grouting port. Simultaneously, after a set time, the advancing fully mechanized mining face is a set distance away from the grouting port, and the slurry inside the injection pipeline flows out from the limiting ring and enters the newly formed goaf.

[0022] Step 9: Repeat steps 7 and 8 to continuously grout the goaf until grouting of all sections is completed.

[0023] In this invention, a sealing plug is first installed at the outlet end of each branch pipe to effectively prevent foreign objects from entering the outlet end of the branch pipe, avoiding blockage and ensuring the smooth progress of subsequent grouting operations. When the branch pipe on the front side enters the corner of the working face, a water-soluble plug replaces the sealing plug. This allows the dissolution time of the water-soluble plug to be synchronized with the forward advance of the working face, so that the water-soluble plug automatically opens when the working face advances to the grouting position to a set distance, thereby automatically performing the grouting operation. Traditional grouting techniques, which use two alternating grouting pipelines, require frequent switching between them. Furthermore, material sedimentation and blockage can easily occur in the stopped pipelines, necessitating short-term shutdowns of the grouting station. Additionally, the pipelines need to be flushed with water during switching. Therefore, traditional techniques have low grouting efficiency and involve a significant workload. In contrast, this new method uses water-soluble plugs with water-soluble properties that automatically clear the pipelines. This eliminates the need for short-term shutdowns of the grouting station, allowing for continuous grouting operations. Its grouting efficiency is significantly higher than traditional techniques, effectively reducing the oxygen content in the floating coal seam and preventing spontaneous combustion, thus achieving effective fire prevention. It also effectively reduces the workload of workers. This method is simple to implement, requires minimal operation and maintenance, offers good economic benefits, and boasts high grouting efficiency. It enables continuous grouting operations in goaf areas, effectively ensuring safe production in coal mines and improving the safety factor for coal miners, making it suitable for widespread application.

[0024] As a preferred embodiment, the sealing plug is connected to the outside of the outlet end of the branch pipe via a threaded connection.

[0025] In steps five and seven, the time is set as the dissolution time t of the water-soluble sealing ring, with the unit being d. The dissolution time t is determined by formula (1).

[0026]

[0027] In the formula, l is the minimum distance between the grouting port and the end of the working face, in meters (m), and v is the average daily advance speed of the working face, in meters per day (m / d).

[0028] As a preferred embodiment, the slurry is a 20% concentration yellow mud slurry.

[0029] As a preferred option, the distance set in steps five and seven is 20m.

[0030] This invention also provides a method for preventing spontaneous combustion of floating coal in goaf areas, employing a system for preventing spontaneous combustion of floating coal in goaf areas, comprising the following steps:

[0031] S1: Install a filling pipeline in the working face roadway and connect the inlet end of the filling pipeline to the nitrogen generation system outside the roadway;

[0032] S2: Connect a branch pipe at set intervals along the length of one side of the filling pipe. Each branch pipe is connected in series with a control valve, and the outlet end of each branch pipe is lower than the filling pipe.

[0033] S3: Install a sealing plug at the outlet end of each branch pipe to seal it, and close the control valve on each branch pipe.

[0034] S4: Nitrogen gas is prepared by liquid nitrogen vaporizer and the prepared nitrogen gas is continuously supplied into the injection pipeline;

[0035] S5: As the fully mechanized mining face advances, when the side branch pipeline on the front side reaches the corner of the working face, first ensure that the control valve on the side branch pipeline is closed, then remove the sealing plug on the side branch pipeline, and then install a water-soluble plug at the outlet end of the side branch pipeline. During the installation of the water-soluble plug, first fill the inside of the water-soluble plug with water, then install the water-soluble plug at the outlet end of the side branch pipeline, and finally open the control valve on the side branch pipeline.

[0036] S6: The water inside the water-soluble plug acts on the water-soluble sealing ring. After a set time, the water-soluble sealing ring dissolves and falls out of the annular mounting groove. Under the impact of nitrogen, the circular baffle, which loses the positioning support of the annular mounting groove, automatically disengages from the limiting ring, forming a nitrogen injection port. At this time, the outlet end of the side branch pipeline changes from a closed state to a conductive state. Simultaneously, after a set time, the fully mechanized mining face advances to a set distance in front of the nitrogen injection port, and the nitrogen inside the injection pipeline flows out from the limiting ring and enters the newly formed goaf.

[0037] S7: As the longwall mining face advances, when the next branch pipeline reaches the corner of the working face, first ensure that the control valve on the branch pipeline is closed, then remove the sealing plug on the branch pipeline, and then install a water-soluble plug at the outlet end of the branch pipeline. During the installation of the water-soluble plug, first fill the inside of the water-soluble plug with water, then install the water-soluble plug at the outlet end of the branch pipeline, and finally open the control valve on the branch pipeline.

[0038] S8: The water inside the water-soluble plug acts on the water-soluble sealing ring. After a set time, the water-soluble sealing ring dissolves and falls out of the annular mounting groove. Under the impact of nitrogen, the circular baffle is automatically pushed out from inside the limiting ring. At this time, the outlet end of the side branch pipeline changes from a closed state to a conductive state. The side branch pipeline at this position forms a conveying path with a shorter stroke and less resistance, replacing the previous nitrogen injection port to form a new nitrogen injection port. Simultaneously, after a set time, the advancing fully mechanized mining face is a set distance away from the nitrogen injection port. The nitrogen inside the injection pipeline flows out from the limiting ring and enters the newly formed goaf.

[0039] S9: Repeat S7 and S8 to continuously inject nitrogen into the goaf until the nitrogen injection operation is completed in all sections.

[0040] As a preferred option, the set distance in S6 and S8 is 20m.

[0041] In this invention, a sealing plug is first installed at the outlet end of each branch pipe to effectively prevent foreign objects from entering the outlet end of the branch pipe, avoiding blockage and ensuring the smooth progress of subsequent nitrogen injection operations. When the branch pipe on the front side enters the corner of the working face, a water-soluble plug replaces the sealing plug. At the same time, the water-soluble plug is filled with water, so that the dissolution time of the water-soluble plug is synchronized with the forward advance of the working face. Thus, when the working face advances to the nitrogen injection position to a set distance, the water-soluble plug automatically opens, thereby automatically performing the nitrogen injection operation. Traditional grouting techniques, which use two alternating grouting pipelines, require frequent switching between them. Furthermore, material sedimentation and blockage can easily occur in the stopped pipelines, necessitating short-term shutdowns of the grouting station. Additionally, the pipelines need to be flushed with water during switching. Therefore, traditional techniques have low grouting efficiency and involve a significant workload. In contrast, this method uses water-soluble plugs that automatically clear the pipelines, enabling continuous nitrogen injection. Its nitrogen injection efficiency is significantly higher than traditional techniques, effectively reducing the oxygen content in the floating coal seam and preventing spontaneous combustion, thus achieving effective fire prevention. Simultaneously, it effectively reduces the workload of workers. This method is simple to implement, requires minimal operation and maintenance, offers good economic benefits, and boasts high nitrogen injection efficiency. It allows for continuous nitrogen injection into goaf areas, effectively ensuring safe coal mine production and improving the safety factor for miners, making it suitable for widespread application. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the existing technology that uses two grouting pipes for interactive grouting;

[0043] Figure 2 This is a schematic diagram of the layout of a system for preventing spontaneous combustion of floating coal in a goaf area according to the present invention;

[0044] Figure 3 This is a schematic diagram of the structure of a system for preventing spontaneous combustion of floating coal in goaf areas according to the present invention;

[0045] Figure 4 This is a schematic diagram of the assembly of the bypass pipeline and the water-soluble plug in this invention;

[0046] Figure 5 This is a schematic diagram of the structure of the water-soluble plug in this invention;

[0047] Figure 6 This is a schematic diagram of the assembly of the branch pipe and the sealing plug in this invention.

[0048] In the diagram: 1. Fully mechanized mining face; 2. Sealing plug; 3. Goaf; 4. Working face roadway; 5. Injection pipeline; 6. Side branch pipeline; 7. Circular baffle; 8. Water-soluble sealing ring; 9. Water-soluble plug; 10. Pressure cap; 11. Sleeve; 12. Limiting ring; 13. Annular mounting groove; 14. Annular positioning step; 15. Grouting port; 16. Nitrogen injection port; 17. Grouting pipeline; 18. Cut-off grout outlet; 19. Control valve. Detailed Implementation

[0049] The invention will now be further described with reference to the accompanying drawings.

[0050] like Figures 2 to 6 As shown, the present invention provides a system for preventing spontaneous combustion of floating coal in goaf areas, including an injection pipeline 5, a side branch pipeline 6, and a water-soluble plug 9;

[0051] The injection pipeline 5 is laid or hoisted on one side of the roadway in the working face roadway 4 and is used to supply slurry or nitrogen.

[0052] Multiple branch pipes 6 are evenly distributed along the length of the injection pipe 5 on the same side, and the inlet end of each branch pipe 6 is connected to the injection pipe 5 in a continuous manner. A control valve 19 is installed in the middle of each branch pipe 6, and an external thread structure is provided on the outside of the outlet end of each branch pipe 6. The branch pipes 6 are used to transport the slurry or nitrogen in the injection pipe 5 to the goaf 3.

[0053] Multiple water-soluble plugs 9 are correspondingly installed with multiple branch pipes 6. Each water-soluble plug 9 consists of a cap 10, a water-soluble sealing ring 8, and a circular baffle 7. The cap 10 consists of a sleeve 11 and a limiting ring 12. The sleeve 11 has an annular mounting groove 13 inside its right end, and an internal thread structure is provided on the part of the sleeve 11 to the left of the annular mounting groove 13. The sleeve 11 is fixedly fitted onto the outside of the outlet end of the branch pipe 6 through threaded engagement. The limiting ring 12 is coaxially fixedly connected to the right side of the sleeve 11. The inner side of the end; the water-soluble sealing ring 8 is made of water-soluble material, which dissolves in water within a set time range after contact with water; the water-soluble sealing ring 8 is adapted to be installed in the annular mounting groove 13, the inner diameter of which is smaller than the inner diameter of the limiting ring 12, and an annular positioning step 14 is provided on the left side of the interior of the water-soluble sealing ring 8, the inner diameter of the annular positioning step 14 is smaller than the inner diameter of the limiting ring 12; the size of the circular baffle 7 is adapted to the size of the annular positioning step 14 and is fixedly installed in the annular positioning step 14.

[0054] As a preferred option, the distance between two adjacent branch pipes 6 is 40m.

[0055] In this invention, by uniformly connecting multiple branch pipes along the length of the filling pipeline, it is convenient to use multiple branch pipes as grouting ports or nitrogen injection ports sequentially during the advancement of the working face. This allows for switching between different grouting port or nitrogen injection port positions without cutting off the filling pipeline, greatly improving the convenience of the filling process, significantly reducing the workload of operators, and increasing the safety factor of the operation. An external thread structure is provided on the outer side of the outlet end of each branch pipe, facilitating the assembly of plugs through threaded engagement, thereby improving the convenience of plug assembly and effectively ensuring the reliability and stability of the assembled plugs. The cap of the water-soluble plug consists of a sleeve and a limiting ring, with an annular mounting groove inside the right end of the sleeve and an internal thread structure on the left side of the annular mounting groove. This facilitates the assembly of the cap on the outer side of the branch pipe outlet end through threaded engagement, and also facilitates the use of the annular mounting groove to limit the installation of the water-soluble sealing ring. An annular positioning step is provided on the left side of the interior of the water-soluble sealing ring, and a circular baffle is installed in the annular positioning step. This allows the circular baffle, in conjunction with the water-soluble sealing ring, to effectively seal the through-hole area inside the limiting ring, thus creating a closed structure for the water-soluble plug. The water-soluble sealing ring is made of a water-soluble material, so that when water comes into contact with the sealing ring for a certain period, it automatically dissolves. This allows the water-soluble sealing ring to automatically detach from the annular mounting groove without operator intervention. Because the outer diameter of the circular baffle is smaller than the inner diameter of the limiting ring, after the water-soluble sealing ring dissolves, the circular baffle can be quickly ejected from the limiting ring under the impact of the internal slurry or nitrogen gas. This allows the slurry or nitrogen gas from the injection pipeline to be smoothly injected into the goaf through the connected branch pipeline. By connecting a control valve in series on each branch pipe, the on / off state of the branch pipe can be easily controlled by the action of the control valve, thus allowing a water-soluble plug to be installed at the outlet end of the branch pipe without stopping the injection.

[0056] This invention achieves completely uninterrupted grouting or nitrogen injection operations by simply installing one injection pipeline on one side of the roadway in the working face. Compared to the traditional method of using two injection pipelines for alternating grouting, pipeline consumption is reduced by approximately 50%, and the corresponding pipeline installation and maintenance workload is also reduced by approximately 50%. Because the water-soluble plug automatically opens after a set time of water action, the predetermined grouting or nitrogen injection operations can be achieved relatively automatically during the synchronous advancement of the working face, significantly improving the automation level of the injection operation. This system requires minimal operation and maintenance, conveniently achieving uninterrupted grouting or nitrogen injection operations, effectively solving the problem of high pipeline consumption in existing coal mine goaf fire prevention and extinguishing technologies. Simultaneously, it effectively reduces pipeline installation workload and the labor load of operators.

[0057] This invention also provides a method for preventing spontaneous combustion of floating coal in goaf areas, employing a system for preventing spontaneous combustion of floating coal in goaf areas, comprising the following steps:

[0058] Step 1: Install a filling pipeline 5 in the working face roadway 4 and connect the inlet end of the filling pipeline 5 to the pulping station;

[0059] As an alternative, the slurry preparation station is located on the ground, which can take advantage of the height difference between the ground and underground to automatically inject yellow mud slurry into the goaf 3 by gravity, thereby saving the cost of adding an extra power source.

[0060] Step 2: Connect a branch pipe 6 along the length of the filling pipe 5 at predetermined intervals. Each branch pipe 6 is connected in series with a control valve 19.

[0061] Step 3: Install a sealing plug 2 at the outlet end of each branch pipe 6 to seal it, and close the control valve (19) on each branch pipe (6);

[0062] Step 4: Prepare the slurry using a slurry preparation station and continuously transport the prepared slurry to the injection pipeline 5;

[0063] Step 5: As the fully mechanized mining face 1 advances, when the side branch pipeline 6 on the front side reaches the corner of the working face, first ensure that the control valve 19 on the side branch pipeline 6 is closed, then remove the sealing plug 2 on the side branch pipeline 6, then install the water-soluble plug 9 at the outlet end of the side branch pipeline 6, and finally open the control valve 19 on the side branch pipeline 6.

[0064] Step Six: The slurry in the injection pipeline 5 acts on the water-soluble sealing ring 8. After a set time, the water-soluble sealing ring 8 dissolves and falls off from the annular mounting groove 13. Under the impact of the slurry, the circular baffle 7, which loses the positioning support of the annular mounting groove 13, automatically disengages from the limiting ring 12. At this time, the outlet end of the side branch pipeline 6 changes from a closed state to a conductive state, forming a grouting port 15. Simultaneously, after a set time, the fully mechanized mining face 1 advances to a set distance in front of the grouting port 15. The slurry inside the injection pipeline 5 flows out from the limiting ring 120 and enters the newly formed goaf 3.

[0065] Step 7: As the fully mechanized mining face 1 advances, when the next branch pipeline 6 reaches the corner of the working face, first ensure that the control valve 19 on the branch pipeline 6 is closed, then remove the sealing plug 2 on the branch pipeline 6, then install the water-soluble plug 9 at the outlet end of the branch pipeline 6, and finally open the control valve 19 on the branch pipeline 6.

[0066] Step 8: The slurry in the injection pipeline 5 acts on the water-soluble sealing ring 8. After a set time, the water-soluble sealing ring 8 dissolves and falls out of the annular mounting groove 13. Under the impact of the slurry, the circular baffle 7 is automatically pushed out from the inside of the limiting ring 12. At this time, the outlet end of the side branch pipeline 6 changes from a closed state to a conductive state. The side branch pipeline 6 at this position forms a conveying path with a shorter stroke and less resistance, replacing the previous grouting port 15 to form a new grouting port 15. Simultaneously, after a set time, the advancing fully mechanized mining face 1 is a set distance away from the grouting port 15. The slurry inside the injection pipeline 5 flows out from the limiting ring 120 and enters the newly formed goaf 3.

[0067] Step 9: Repeat steps 7 and 8 to continuously grout goaf 3 until grouting of all sections is completed.

[0068] As a preferred embodiment, the sealing plug 2 is connected to the outside of the outlet end of the branch pipe 6 via a threaded connection.

[0069] In steps five and seven, the time is set as the dissolution time t of the water-soluble sealing ring 8, the unit of which is d. The dissolution time t is determined by formula (1).

[0070]

[0071] In the formula, l is the minimum distance between the grouting port 15 and the end of the working face, in meters (m), and v is the average daily advance speed of the working face, in meters per day (m / d).

[0072] As a preferred embodiment, the slurry is a 20% concentration yellow mud slurry.

[0073] As a preferred option, the distance set in steps five and seven is 20m.

[0074] In this invention, a sealing plug is first installed at the outlet end of each branch pipe to effectively prevent foreign objects from entering the outlet end of the branch pipe, avoiding blockage and ensuring the smooth progress of subsequent grouting operations. When the branch pipe on the front side enters the corner of the working face, a water-soluble plug replaces the sealing plug. This allows the dissolution time of the water-soluble plug to be synchronized with the forward advance of the working face, so that the water-soluble plug automatically opens when the working face advances to the grouting position to a set distance, thereby automatically performing the grouting operation. Traditional grouting techniques, which use two alternating grouting pipelines, require frequent switching between them. Furthermore, material sedimentation and blockage can easily occur in the stopped pipelines, necessitating short-term shutdowns of the grouting station. Additionally, the pipelines need to be flushed with water during switching. Therefore, traditional techniques have low grouting efficiency and involve a significant workload. In contrast, this new method uses water-soluble plugs with water-soluble properties that automatically clear the pipelines. This eliminates the need for short-term shutdowns of the grouting station, allowing for continuous grouting operations. Its grouting efficiency is significantly higher than traditional techniques, effectively reducing the oxygen content in the floating coal seam and preventing spontaneous combustion, thus achieving effective fire prevention. It also significantly reduces the workload of operators. This method is simple to implement, requires minimal operation and maintenance, offers good economic benefits, and boasts high grouting efficiency, enabling continuous grouting operations in goaf areas, making it suitable for large-scale application.

[0075] This invention also provides a method for preventing spontaneous combustion of floating coal in goaf areas, employing a system for preventing spontaneous combustion of floating coal in goaf areas, comprising the following steps:

[0076] S1: Install a filling pipeline 5 in the working face roadway 4, and connect the inlet end of the filling pipeline 5 to the nitrogen generation system outside the roadway.

[0077] S2: Connect a side branch pipe 6 at set intervals along the length of one side of the filling pipe 5. Each side branch pipe 6 is connected in series with a control valve 19, and the outlet end of each side branch pipe 6 is lower than the position of the filling pipe 5.

[0078] S3: Install a sealing plug 2 at the outlet end of each branch pipe 6 to seal it, and close the control valve 19 on each branch pipe 6.

[0079] S4: Nitrogen gas is prepared by liquid nitrogen vaporizer and the prepared nitrogen gas is continuously supplied into the injection pipeline 5;

[0080] S5: As the fully mechanized mining face 1 advances, when the side branch pipeline 6 on the front side reaches the corner of the working face, first ensure that the control valve 19 on the side branch pipeline 6 is closed, then remove the sealing plug 2 on the side branch pipeline 6, and then install the water-soluble plug 9 at the outlet end of the side branch pipeline 6. During the installation of the water-soluble plug 9, first fill the inside of the water-soluble plug 9 with water, then install the water-soluble plug 9 at the outlet end of the side branch pipeline 6, and finally open the control valve 19 on the side branch pipeline 6.

[0081] S6: The water inside the water-soluble plug 9 acts on the water-soluble sealing ring 8. After a set time, the water-soluble sealing ring 8 dissolves and falls out of the annular mounting groove 13. Under the impact of nitrogen, the circular baffle 7, which loses the positioning support of the annular mounting groove 13, automatically disengages from the limiting ring 12, forming a nitrogen injection port 16. At this time, the outlet end of the side branch pipeline 6 changes from a closed state to a conductive state. Simultaneously, after a set time, the fully mechanized mining face 1 advances to a set distance in front of the nitrogen injection port 16. The nitrogen inside the injection pipeline 5 flows out from the limiting ring 120 and enters the newly formed goaf 3.

[0082] S7: As the fully mechanized mining face 1 advances, when the next branch pipeline 6 reaches the corner of the working face, first ensure that the control valve 19 on the branch pipeline 6 is closed, then remove the sealing plug 2 on the branch pipeline 6, and then install the water-soluble plug 9 at the outlet end of the branch pipeline 6. During the installation of the water-soluble plug 9, first fill the inside of the water-soluble plug 9 with water, then install the water-soluble plug 9 at the outlet end of the branch pipeline 6, and finally open the control valve 19 on the branch pipeline 6.

[0083] S8: The water inside the water-soluble plug 9 acts on the water-soluble sealing ring 8. After a set time, the water-soluble sealing ring 8 dissolves and falls out of the annular mounting groove 13. Under the impact of nitrogen, the circular baffle 7 is automatically pushed out from inside the limiting ring 12. At this time, the outlet end of the side branch pipe 6 changes from a closed state to a conductive state. The side branch pipe 6 at this position forms a conveying path with a shorter stroke and less resistance, replacing the previous nitrogen injection port 16 to form a new nitrogen injection port 16. Simultaneously, after a set time, the advancing fully mechanized mining face 1 is a set distance away from the nitrogen injection port 16. The nitrogen inside the injection pipe 5 flows out from the limiting ring 120 and enters the newly formed goaf 3.

[0084] S9: Repeat S7 and S8 to continuously inject nitrogen into goaf 3 until the nitrogen injection operation is completed in all sections.

[0085] As a preferred option, the set distance in S6 and S8 is 20m.

[0086] In this invention, a sealing plug is first installed at the outlet end of each branch pipe to effectively prevent foreign objects from entering the outlet end of the branch pipe, avoiding blockage and ensuring the smooth progress of subsequent nitrogen injection operations. When the branch pipe on the front side enters the corner of the working face, a water-soluble plug replaces the sealing plug. At the same time, the water-soluble plug is filled with water, so that the dissolution time of the water-soluble plug is synchronized with the forward advance of the working face. Thus, when the working face advances to the nitrogen injection position to a set distance, the water-soluble plug automatically opens, thereby automatically performing the nitrogen injection operation. Traditional grouting techniques, which use two alternating grouting pipelines, require frequent switching between them. Furthermore, material sedimentation and blockage can easily occur in the stopped pipelines, necessitating short-term shutdowns of the grouting station. Additionally, the pipelines need to be flushed with water during switching. Therefore, traditional techniques have low grouting efficiency and involve a significant workload. This new method, however, uses water-soluble plugs that automatically clear the pipelines, enabling continuous nitrogen injection. Its nitrogen injection efficiency is significantly higher than traditional techniques, effectively reducing the oxygen content in the floating coal seam and preventing spontaneous combustion, thus achieving effective fire prevention. It also effectively reduces the workload of workers. This method is simple to implement, requires minimal operation and maintenance, is economically efficient, and allows for continuous nitrogen injection into goaf areas, effectively ensuring safe coal mine operations and improving the safety of miners. It is suitable for widespread application.

Claims

1. A method for preventing spontaneous combustion of floating coal in a goaf, comprising a system for preventing spontaneous combustion of floating coal in a goaf, the system comprising an injection pipeline (5), a side branch pipeline (6), and a water-soluble plug (9); the injection pipeline (5) is laid or hoisted on one side of the roadway wall in the working face roadway (4); multiple side branch pipelines (6) are evenly distributed along the length direction on the same side of the injection pipeline (5), and the inlet end of each side branch pipeline (6) is connected to the injection pipeline. (5) A control valve (19) is installed in the middle of each branch pipe (6), and an external thread structure is provided on the outside of the outlet end of each branch pipe (6); the branch pipe (6) is used to transport the slurry or nitrogen in the injection pipe (5) to the goaf (3); multiple water-soluble plugs (9) are set one-to-one with multiple branch pipes (6); the water-soluble plugs (9) are composed of a gland (10), a water-soluble sealing ring (8) and a circular baffle (7). The pressure cap (10) is composed of a sleeve (11) and a limiting ring (12). An annular mounting groove (13) is provided inside the right end of the sleeve (11). An internal thread structure is provided on the part of the sleeve (11) to the left of the annular mounting groove (13), and it is fixedly fitted onto the outside of the outlet end of the branch pipe (6) through threaded engagement. The limiting ring (12) is coaxially fixedly connected to the inner side of the right end of the sleeve (11). The water-soluble sealing ring (8) is composed of… Made of water-soluble material, the water-soluble sealing ring (8) is fitted in the annular mounting groove (13), the inner diameter of which is smaller than the inner diameter of the limiting ring (12). An annular positioning step (14) is provided on the left side of the interior of the water-soluble sealing ring (8), the inner diameter of which is smaller than the inner diameter of the limiting ring (12). The size of the circular baffle (7) is adapted to the size of the annular positioning step (14) and is fixedly installed in the annular positioning step (14). Its features are, The method includes the following steps: Step 1: Install a filling pipeline (5) in the working face roadway (4) and connect the inlet end of the filling pipeline (5) to the pulping station; Step 2: Connect a side branch pipe (6) along the length direction on one side of the filling pipe (5) at a set distance, wherein each side branch pipe (6) is connected in series with a control valve (19). Step 3: Install a sealing plug (2) at the outlet end of each branch pipe (6) to seal it, and close the control valve (19) on each branch pipe (6). Step 4: Use a pulping station to prepare slurry and continuously transport the prepared slurry to the injection pipeline (5); Step 5: As the fully mechanized mining face (1) advances, when the side branch pipeline (6) on the front side reaches the corner of the working face, first ensure that the control valve (19) on the side branch pipeline (6) is closed, then remove the sealing plug (2) on the side branch pipeline (6), then install the water-soluble plug (9) at the outlet end of the side branch pipeline (6), and finally open the control valve (19) on the side branch pipeline (6). Step 6: The slurry in the injection pipeline (5) acts on the water-soluble sealing ring (8). After a set time, the water-soluble sealing ring (8) dissolves and falls off from the annular mounting groove (13). Under the impact of the slurry, the circular baffle (7), which loses the positioning support of the annular mounting groove (13), automatically disengages from the limiting ring (12). At this time, the outlet end of the side branch pipeline (6) changes from a closed state to a conductive state, forming a grouting port (15). Simultaneously, after a set time, the fully mechanized mining face (1) advances to a set distance in front of the grouting port (15). The slurry inside the injection pipeline (5) flows out from the limiting ring (12) and enters the newly formed goaf (3). Step 7: As the fully mechanized mining face (1) advances, when the next branch pipe (6) reaches the corner of the working face, first ensure that the control valve (19) on the branch pipe (6) is closed, then remove the sealing plug (2) on the branch pipe (6), then install the water-soluble plug (9) at the outlet end of the branch pipe (6), and finally open the control valve (19) on the branch pipe (6). Step 8: The slurry in the injection pipeline (5) acts on the water-soluble sealing ring (8). After a set time, the water-soluble sealing ring (8) dissolves and falls out of the annular mounting groove (13). Under the impact of the slurry, the circular baffle (7) is automatically flushed out from the inside of the limiting ring (12). At this time, the outlet end of the side branch pipeline (6) changes from a closed state to a conductive state. The side branch pipeline (6) at this position forms a conveying path with a shorter stroke and less resistance, replacing the previous grouting port (15) to form a new grouting port (15). Simultaneously, after a set time, the forward-advancing fully mechanized mining face (1) is a set distance away from the grouting port (15). The slurry inside the injection pipeline (5) flows out from the limiting ring (12) and enters the newly formed goaf (3). Step 9: Repeat steps 7 and 8 to continuously grout the goaf (3) until the grouting of all sections is completed; In steps six and eight, the set time is the dissolution time of the water-soluble sealing ring (8). Its unit is d, dissolution time It is determined by formula (1); （1）； In the formula, This is the minimum distance between the grouting port (15) and the end of the working face, in meters. The average daily advance speed of the working face is expressed in m / d.

2. The method for preventing spontaneous combustion of floating coal in a goaf according to claim 1, characterized in that, The sealing plug (2) is connected to the outside of the outlet end of the side branch pipe (6) by a threaded connection.

3. The method for preventing spontaneous combustion of floating coal in a goaf area according to claim 1, characterized in that, The slurry is a 20% concentration of yellow mud slurry.

4. The method for preventing spontaneous combustion of floating coal in a goaf according to claim 1, characterized in that, The distance set in steps six and eight is 20m.

5. The method for preventing spontaneous combustion of floating coal in a goaf according to claim 1, characterized in that, The distance between two adjacent side branch pipes (6) is 40m.

6. A method for preventing spontaneous combustion of floating coal in a goaf, comprising a system for preventing spontaneous combustion of floating coal in a goaf, the system comprising an injection pipeline (5), a side branch pipeline (6), and a water-soluble plug (9); the injection pipeline (5) is laid or hoisted on one side of the roadway wall in the working face roadway (4); multiple side branch pipelines (6) are evenly distributed along the length direction on the same side of the injection pipeline (5), and the inlet end of each side branch pipeline (6) is connected to the injection pipeline. (5) A control valve (19) is installed in the middle of each branch pipe (6), and an external thread structure is provided on the outside of the outlet end of each branch pipe (6); the branch pipe (6) is used to transport the slurry or nitrogen in the injection pipe (5) to the goaf (3); multiple water-soluble plugs (9) are set one-to-one with multiple branch pipes (6); the water-soluble plugs (9) are composed of a gland (10), a water-soluble sealing ring (8) and a circular baffle (7). The pressure cap (10) is composed of a sleeve (11) and a limiting ring (12). An annular mounting groove (13) is provided inside the right end of the sleeve (11). An internal thread structure is provided on the part of the sleeve (11) to the left of the annular mounting groove (13), and it is fixedly fitted onto the outside of the outlet end of the branch pipe (6) through threaded engagement. The limiting ring (12) is coaxially fixedly connected to the inner side of the right end of the sleeve (11). The water-soluble sealing ring (8) is composed of… Made of water-soluble material, the water-soluble sealing ring (8) is fitted in the annular mounting groove (13), the inner diameter of which is smaller than the inner diameter of the limiting ring (12). An annular positioning step (14) is provided on the left side of the interior of the water-soluble sealing ring (8), the inner diameter of which is smaller than the inner diameter of the limiting ring (12). The size of the circular baffle (7) is adapted to the size of the annular positioning step (14) and is fixedly installed in the annular positioning step (14). Its features are, The method includes the following steps: S1: Install a filling pipeline (5) in the working face roadway (4) and connect the inlet end of the filling pipeline (5) to the nitrogen generation system outside the roadway; S2: Connect a side branch pipe (6) along the length direction on one side of the filling pipe (5) at a set distance. Each side branch pipe (6) is connected in series with a control valve (19), and the outlet end of each side branch pipe (6) is lower than the position of the filling pipe (5). S3: Install a sealing plug (2) at the outlet end of each branch pipe (6) to seal it, and close the control valve (19) on each branch pipe (6). S4: Nitrogen is prepared by liquid nitrogen vaporizer and the prepared nitrogen is continuously supplied into the injection pipeline (5); S5: As the fully mechanized mining face (1) advances, when the side branch pipeline (6) on the front side reaches the corner of the working face, first ensure that the control valve (19) on the side branch pipeline (6) is closed, then remove the sealing plug (2) on the side branch pipeline (6), and then install the water-soluble plug (9) at the outlet end of the side branch pipeline (6). During the installation of the water-soluble plug (9), first fill the inside of the water-soluble plug (9) with water, then install the water-soluble plug (9) at the outlet end of the side branch pipeline (6), and finally open the control valve (19) on the side branch pipeline (6). S6: The water inside the water-soluble plug (9) acts on the water-soluble sealing ring (8). After a set time, the water-soluble sealing ring (8) dissolves and falls out of the annular mounting groove (13). Under the impact of nitrogen, the circular baffle (7), which loses the positioning support of the annular mounting groove (13), automatically separates from the limiting ring (12) to form a nitrogen injection port (16). At this time, the outlet end of the side branch pipeline (6) changes from a closed state to a conductive state. Simultaneously, after a set time, the fully mechanized mining face (1) advances to a set distance in front of the nitrogen injection port (16). The nitrogen inside the injection pipeline (5) flows out from the limiting ring (12) and enters the newly formed goaf (3). S7: As the fully mechanized mining face (1) advances, when the next branch pipeline (6) reaches the corner of the working face, first ensure that the control valve (19) on the branch pipeline (6) is closed, then remove the sealing plug (2) on the branch pipeline (6), and then install the water-soluble plug (9) at the outlet end of the branch pipeline (6). During the installation of the water-soluble plug (9), first fill the inside of the water-soluble plug (9) with water, then install the water-soluble plug (9) at the outlet end of the branch pipeline (6), and finally open the control valve (19) on the branch pipeline (6). S8: The water inside the water-soluble plug (9) acts on the water-soluble sealing ring (8). After a set time, the water-soluble sealing ring (8) dissolves and falls out of the annular mounting groove (13). Under the impact of nitrogen, the circular baffle (7) is automatically pushed out from the inside of the limiting ring (12). At this time, the outlet end of the side branch pipeline (6) changes from a closed state to a conductive state. The side branch pipeline (6) at this position forms a conveying path with a shorter stroke and less resistance, replacing the previous nitrogen injection port (16) to form a new nitrogen injection port (16). Simultaneously, after a set time, the advancing fully mechanized mining face (1) is a set distance away from the nitrogen injection port (16). The nitrogen inside the injection pipeline (5) flows out from the limiting ring (12) and enters the newly formed goaf (3). S9: Repeat S7 and S8 to continuously inject nitrogen into the goaf (3) until the nitrogen injection operation of all sections is completed.

7. A method for preventing spontaneous combustion of floating coal in a goaf area according to claim 6, characterized in that, The set distance in S6 and S8 is 20m.

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