Mine return air corner low-oxygen multi-stage cooperative prevention and control method

Abstract

The invention provides a low-oxygen multi-stage cooperative prevention and control method for a mine return air corner. The method comprises the following steps: firstly, carrying out grid division on a key area and arranging monitoring points; the junction position of the working face and the goaf is blocked, and adjustable arc baffles are arranged at the corners of an air inlet way and an air return way; an air inlet of the ejector faces an air return corner, an air outlet is communicated with an air return way air duct, and the air inlet end is connected into a compressed air pipeline. Continuously monitoring the oxygen concentration, and if the oxygen concentration is lower than a safety threshold, dynamically adjusting the inclination angle of the arc-shaped baffle; if the oxygen concentration does not reach the standard, an ejector is started, oxygen-enriched air is introduced to form jet flow, accumulated gases such as carbon monoxide and carbon dioxide are exhausted until the oxygen concentration recovers to the safety level, and multi-stage dynamic cooperative regulation and control are achieved.

Description

Technical Field

[0001] This invention relates to the field of mining engineering, specifically a multi-level synergistic prevention and control method for low oxygen levels in the return air corner of a mine. Background Technology

[0002] Coal has always been one of the pillar industries of my country's energy and social development. The safety and stability of coal mine production are closely related to people's production and lives. In low-gas mine operations, the working area may experience a decrease in oxygen concentration, leading to limitations in personnel's physiological functions and, in severe cases, the risk of asphyxiation, threatening operational safety. To maintain a breathable atmospheric environment, it is necessary to effectively control oxygen concentration and achieve the directional transportation of fresh media.

[0003] Currently, research and application of technologies such as extraction and diversion, and sealing and isolation have been carried out to address the problem of excessively low oxygen concentrations in localized areas of the mining site, achieving some passive removal and spatial isolation of harmful components. Among these, the active diversion method based on the fluid ejection principle has shown certain application potential in local airflow control, capable of achieving gas replacement in the target area through energy exchange. However, existing technologies mostly rely on a single diversion mechanism, lacking the ability to coordinate responses to multiple sources of interference, and their adaptability and control precision under dynamic operating conditions remain limited, making it difficult to achieve graded, orderly, and controllable gas environment regulation.

[0004] Therefore, it is urgent to develop a control method based on multi-stage ejection and synergistic diversion mechanism to enhance the active regulation capability of the gas environment under complex working conditions and ensure the stability of oxygen concentration and operational safety in the work space. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-level synergistic prevention and control method for low oxygen levels in the return air corner of a mine, comprising the following steps:

[0006] S1. The return airway area, ejector installation area, and return air corner area are divided into multiple evenly distributed grid cell areas. The center of each grid cell area is used as a monitoring point, and a real-time oxygen concentration monitoring sensor is installed at the monitoring point.

[0007] S2. Lay sealing material at the boundary between the working face and the goaf.

[0008] S3. An arc-shaped baffle is installed at each corner formed by the sealing material and the intake and return airways.

[0009] S4. Align the air inlet of the ejector with the return air corner, connect the air outlet to the ventilation duct located in the return airway, and connect the end near the air inlet to the downhole compressed air pipeline through the pipeline.

[0010] S5. Detect the oxygen concentration in the return air corner space using a real-time oxygen concentration monitoring sensor, and determine whether the current oxygen concentration is less than the safety threshold. If so, proceed to step S6; otherwise, continue monitoring the oxygen concentration in the return air corner space.

[0011] S6. Areas with oxygen concentrations below the safety threshold are designated as low-oxygen areas, and the area with the lowest oxygen concentration is selected as the area to be treated.

[0012] The angle of the arc-shaped baffle is adjusted by an electromagnetic actuator.

[0013] S7. After waiting for t hours, determine whether the oxygen concentration is less than the safety threshold using a real-time oxygen concentration monitoring sensor. If yes, proceed to step S8; otherwise, return to step S5.

[0014] S8. Start the ejector and introduce external oxygen-enriched air through the pipeline to form a directional jet, which discharges the carbon dioxide and carbon monoxide accumulated in the return air corner into the return air alley until the oxygen concentration is greater than the safety threshold. Then, turn off the ejector and return to step S5.

[0015] Furthermore, in step S2), filling the sealing material includes the following steps:

[0016] S2.1 Stack the coal bags in the corner of the return airway to form a sealing frame, thus completing one sealing operation.

[0017] S2.2 Fill the gaps in the coal bags with cement-based expansion material to complete the secondary sealing.

[0018] S2.3. Spray quick-setting foam onto the surface of the sealing skeleton to complete the three-stage sealing process.

[0019] Further, in step S2.2), the cement-based expansive material includes ultrafine silicate cement, ettringite, and cement-based penetrating crystalline waterproofing masterbatch, wherein the mass fractions of each material are as follows:

[0020] The mass fraction of the ultrafine silicate cement is 23.6–26.5.

[0021] The mass fraction of the ettringite is 1.20 to 8.00.

[0022] The cement-based penetrating crystalline waterproof masterbatch has a mass fraction of 0.05–3%.

[0023] Furthermore, in step S2.3), the rapid-setting foam comprises 80% resin by mass and 20% catalyst by mass.

[0024] Furthermore, in step S3), the inner arc surface of the arc-shaped wind deflector is positioned away from the corner. An audible and visual alarm module is installed on the arc-shaped wind deflector.

[0025] The arc-shaped baffle includes a rotating shaft, a baffle body, and an electromagnetic actuator. The baffle body is an arc-shaped baffle, and the top side of the arc-shaped baffle is fixed to the tunnel roof support via the rotating shaft. The electromagnetic actuator is fixed to the tunnel roof or sidewall.

[0026] The electromagnetic actuator includes a servo motor, an electromagnetic brake, a reduction gear transmission mechanism, and an angle sensor. The servo motor is connected to the electromagnetic brake. The electromagnetic brake is connected to the reduction gear transmission mechanism. The reduction gear transmission mechanism is connected to a rotating shaft. An angle sensor is mounted on the rotating shaft. Both the servo motor and the angle sensor are electrically connected to the processor. The electromagnetic brake is a normally closed type. The concave surface of the baffle body faces the working surface.

[0027] During operation, the real-time oxygen concentration monitoring sensor transmits the collected data to the processor. The processor determines whether the current oxygen concentration is below the safety threshold. If so, the processor issues a control command to drive the servo motor, allowing the baffle body to rotate relative to the rotating shaft. If, after t seconds, the oxygen concentration collected by the real-time oxygen concentration monitoring sensor is still below the safety threshold, the processor issues a control command to activate the audible and visual alarm module, triggering an alarm.

[0028] Furthermore, in step S4), the ejector inlet is positioned higher than the outlet. The outlet is 2.0-2.5m from the upper coal wall of the return airway and 0.8-1.0m from the roof.

[0029] The ejector is equipped with an electromagnetic valve and an alarm.

[0030] When adjusting the curved baffle fails to bring the oxygen concentration above the safety threshold, the processor issues a control command to open the solenoid valve and activate the ejector, simultaneously activating the alarm to alert staff that the ejector has been activated.

[0031] Furthermore, in step S4), a rotatable guide shield is provided at the air inlet position of the ejector. When the ejector needs to be activated, the controller issues a control command to adjust the position of the rotatable guide shield so that it faces the area to be treated.

[0032] Furthermore, in step S6), the criterion for determining the low-oxygen region is: when the oxygen concentration is detected to be below 20.9%, the corresponding grid cell region is divided into a low-oxygen region.

[0033] During the monitoring process, the changes in the hypoxia range were analyzed based on the average oxygen concentration during the morning shift maintenance time, the afternoon shift production time, and the evening shift inspection time.

[0034] Furthermore, in step S8), a variable frequency equalizing fan is added to increase the compressed air power.

[0035] Furthermore, in step S1), the monitoring points are distributed in a matrix form, and the distance between adjacent monitoring points is 1m.

[0036] Mixed gas tests are conducted regularly at monitoring points using a handheld multi-functional portable gas analyzer. The measured mixed gases include oxygen, carbon dioxide, and carbon monoxide.

[0037] The technical effects of this invention are undeniable, and its beneficial effects are as follows:

[0038] 1. This invention, by incorporating materials with expansion and filling functions, can effectively prevent low-oxygen gas in the goaf from directly gushing out to the return air corner;

[0039] 2. The present invention arranges an arc-shaped baffle at the return air corner, which can effectively guide the airflow into the return air corner and increase the air volume in the area. On the other hand, it can eliminate the eddy phenomenon and dilute gases such as carbon dioxide and carbon monoxide. Under these circumstances, the low-oxygen gas flowing out from the goaf can be carried away by the larger airflow, thus making it less likely to form a local accumulation of low-oxygen gas.

[0040] 3. This invention proposes a multi-level coordinated technology for maintaining oxygen in mines based on filling materials, arc-shaped baffles, and ejectors. Through the organic combination of filling materials, arc-shaped baffles, and ejectors, a highly efficient control system is formed. The filling materials effectively block gases such as carbon dioxide and carbon monoxide emanating from the goaf, preventing them from entering the safe area and forming the first barrier. The second level of control introduces an intelligent adjustable arc-shaped baffle structure. When the oxygen concentration at the monitoring point behind the first-level barrier falls below a set threshold, the system automatically triggers a feedback mechanism, adjusting the airflow field through electromagnetic valves and dynamically adjusting the inclination angle of the arc-shaped baffles to optimize airflow organization, blocking the rapid forward movement of high-concentration carbon dioxide and carbon monoxide gas masses, achieving adaptive response of airflow guidance and dilution control, and significantly increasing the air volume and fresh air supply at that location. The ejector serves as an emergency reinforcement measure, equipped with an active ejector ventilation device. When the first two levels of measures fail to restore the ambient oxygen concentration to the safe threshold, the control system activates the ejector, introducing external oxygen-rich air to form a directional jet, rapidly increasing the oxygen partial pressure in the working area, and forcibly expelling accumulated carbon dioxide, carbon monoxide, and other gases. This technology optimizes air circulation and airflow distribution within the mine, increases oxygen concentration at the return air corner, effectively improves overall mine air quality, and achieves dynamic joint control of gases such as carbon dioxide and carbon monoxide in underground coal mines. This invention can effectively increase oxygen concentration at the return air corner of the working face, reduce the concentration of carbon dioxide, carbon monoxide, and other gases surging from the goaf back to the working face, and ensure the safety of oxygen supply for mine workers. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the on-site installation of the multi-level collaborative prevention and control technology of the present invention (the area filled with sealing material is not shown).

[0042] Figure 2 This is a schematic diagram of the gas concentration monitoring at the return air corner of the present invention;

[0043] Figure 3 This is a partial schematic diagram of the field ejection of the present invention;

[0044] In the diagram: 1-Working face; 101-Intake airway; 102-Return airway; 2-Goaf; 3-Return air corner; 4-Filling material; 5-Arched windbreak; 6-Ejector; 7-Air duct; 8-Monitoring point; 9-Pipeline. Detailed Implementation

[0045] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0046] Example 1:

[0047] A multi-level coordinated prevention and control method for low oxygen levels in the corner of mine return air includes the following steps:

[0048] S1. The return airway area, ejector installation area, and return air corner area are divided into grids to obtain multiple evenly distributed grid cell areas. The center position of each grid cell area is designated as monitoring point 8, and a real-time oxygen concentration monitoring sensor is installed at monitoring point 8.

[0049] S2. Lay sealing material 4 at the junction of working face 1 and goaf 2;

[0050] S3. At the corners formed by the sealing material 4 and the intake airway 101 and the return airway 102 respectively, an arc-shaped baffle 5 is installed.

[0051] S4. Align the air inlet 601 of the ejector 6 with the return air corner 3, connect the air outlet 602 to the air duct 7 located in the return air tunnel 102, and connect the end near the air inlet 601 to the underground compressed air pipeline through the pipeline 9.

[0052] S5. Detect the oxygen concentration in the space range of the return air corner 3 by the real-time oxygen concentration monitoring sensor, and determine whether the current oxygen concentration is less than the safety threshold. If so, proceed to step S6; otherwise, continue to monitor the oxygen concentration in the space range of the return air corner 3.

[0053] S6. Areas with oxygen concentrations below the safety threshold are designated as low-oxygen areas, and the area with the lowest oxygen concentration is selected as the area to be treated.

[0054] The angle of the arc-shaped baffle 5 is adjusted by an electromagnetic actuator;

[0055] S7. After time t, determine whether the oxygen concentration is less than the safety threshold using a real-time oxygen concentration monitoring sensor. If yes, proceed to step S8; otherwise, return to step S5.

[0056] S8. Start ejector 6 and introduce external oxygen-enriched air through pipe 9 to form a directional jet, which discharges the carbon dioxide and carbon monoxide accumulated at the return air corner 3 to the return air alley 102 until the oxygen concentration is greater than the safety threshold. Then, turn off ejector 6 and return to step S5.

[0057] Example 2:

[0058] The main structure of this embodiment is the same as that of Embodiment 1. Further, in step S2), the method for confirming the amount of sealing material used is as follows: Multiple groups of oxygen concentrations are monitored by deployed real-time oxygen concentration monitoring sensors to identify the low-oxygen areas in each group. The intersection of the low-oxygen areas in each group and the areas in each group with a low-oxygen level of 2 to 4 are used as reference areas. Based on the range of the reference areas, the sealing length and the amount of sealing material used are determined.

[0059] The filling and sealing material 4 includes the following steps:

[0060] S2.1 Stack the coal bags in the corner of the return airway to form a sealing frame, thus completing one sealing operation;

[0061] S2.2 Fill the gaps in the coal bags with cement-based expansion material to complete the secondary sealing;

[0062] S2.3. Spray quick-setting foam onto the surface of the sealing skeleton to complete the three-stage sealing process.

[0063] Example 3:

[0064] The main structure of this embodiment is the same as that of Embodiment 2. Further, in step S2.2), the cement-based expansive material includes ultrafine silicate cement, ettringite, and cement-based penetrating crystalline waterproofing masterbatch, wherein the mass fractions of each material are as follows:

[0065] The mass fraction of the ultrafine silicate cement is 23.6–26.5.

[0066] The mass fraction of the ettringite is 1.20–8.00.

[0067] The cement-based penetrating crystalline waterproof masterbatch has a mass fraction of 0.05–3%.

[0068] Example 4:

[0069] The main structure of this embodiment is the same as any one of embodiments 2 to 3. Further, in step S2.3), the quick-setting foam includes 80% resin by mass and 20% catalyst by mass.

[0070] Example 5:

[0071] The main structure of this embodiment is the same as any one of embodiments 1 to 4. Further, in step S3, the inner arc surface of the arc-shaped windbreak 5 is positioned away from the corner. An audible and visual alarm module is installed on the arc-shaped windbreak 5.

[0072] The arc-shaped baffle 5 includes a rotating shaft, a baffle body, and an electromagnetic actuator. The baffle body is an arc-shaped baffle, and the top side of the arc-shaped baffle is fixed to the tunnel roof support via the rotating shaft. The electromagnetic actuator is fixed to the tunnel roof or sidewall.

[0073] The electromagnetic actuator includes a servo motor, an electromagnetic brake, a reduction gear transmission mechanism, and an angle sensor. The servo motor is connected to the electromagnetic brake. The electromagnetic brake is connected to the reduction gear transmission mechanism. The reduction gear transmission mechanism is connected to a rotating shaft. An angle sensor is mounted on the rotating shaft. Both the servo motor and the angle sensor are electrically connected to the processor. The electromagnetic brake is a normally closed type. The concave surface of the baffle body faces the working surface.

[0074] During operation, the real-time oxygen concentration monitoring sensor transmits the collected data to the processor. The processor determines whether the current oxygen concentration is below the safety threshold. If so, the processor issues a control command to drive the servo motor, allowing the baffle body to rotate relative to the rotating shaft. If, after t seconds, the oxygen concentration collected by the real-time oxygen concentration monitoring sensor is still below the safety threshold, the processor issues a control command to activate the audible and visual alarm module, triggering an alarm.

[0075] Example 6:

[0076] The main structure of this embodiment is the same as any one of embodiments 1 to 5. Further, in step S4), the air inlet 601 of the ejector 6 is positioned higher than the air outlet 602. The air outlet 602 is 2.0-2.5m from the upper coal wall of the return airway 102 and 0.8-1.0m from the roof.

[0077] The ejector 6 is equipped with an electromagnetic valve and an alarm.

[0078] When adjusting the arc-shaped baffle 5 fails to bring the oxygen concentration above the safety threshold, the processor issues a control command to open the solenoid valve and activate the ejector 6, while simultaneously activating the alarm to alert staff that the ejector 6 has been activated.

[0079] Example 7:

[0080] The main structure of this embodiment is the same as any one of embodiments 1 to 6. Further, in step S4), a rotatable guide shield is provided at the air inlet 601 of the ejector. When the ejector 6 needs to be activated, the controller issues a control command to adjust the position of the rotatable guide shield so that the rotatable guide shield faces the area to be treated.

[0081] Example 8:

[0082] The main structure of this embodiment is the same as any one of embodiments 1 to 7. Furthermore, in this embodiment, a combined wind power extender of model KZQ40-18 is selected as the ejector.

[0083] The KZQ40-18 combined wind power extender is a high-volume ejector with an ejector air volume of 300-400 m³ / h. / min; Dimensions ø550mm×800mm; Working air pressure >0.5MPa; Weight 30kg; Air outlet ø550mm; Air consumption 5.2 / min.

[0084] Example 9:

[0085] The main structure of this embodiment is the same as any one of embodiments 1 to 8. Further, in step S6), the criterion for judging the low oxygen region is: when the oxygen concentration is detected to be lower than 20.9%, the corresponding grid cell region is divided into a low oxygen region.

[0086] During the monitoring process, the changes in the hypoxia range were analyzed based on the average oxygen concentration during the morning shift maintenance time, the afternoon shift production time, and the evening shift inspection time.

[0087] The hypoxia level is divided into four levels:

[0088] Level 1 hypoxia is mild hypoxia, with an oxygen concentration of 19.5%-20.9% (volume concentration).

[0089] Level 2 hypoxia is moderate hypoxia, with an oxygen concentration of 16%-19.5%.

[0090] Level 3 hypoxia is severe hypoxia, with an oxygen concentration of 12%-16%.

[0091] Level 4 hypoxia is extreme hypoxia, with an oxygen concentration of less than 12%.

[0092] Example 10:

[0093] The main structure of this embodiment is the same as any one of embodiments 1 to 9. Further, in step S6), the basis for adjusting the angle of the arc baffle 5 is: the processor identifies the spatial centroid coordinates of the current "area to be treated" based on real-time monitoring data (based on the weighted average algorithm of gridded monitoring points) and automatically calculates the optimal pointing angle required by the ejector.

[0094] Example 11:

[0095] The main structure of this embodiment is the same as any one of embodiments 1 to 10. Further, in step S7), t is approximately 45 seconds. Because exposure time exceeding 2-3 minutes may cause irreversible health risks, effective intervention measures must be initiated within 1 minute. Secondly, the filling material affects the gas (such as...) , , The absorption reaction of (etc.) requires a certain amount of time: most highly efficient adsorbent materials can achieve an adsorption efficiency of over 80% within 30-60 seconds; coupled with the 45-second delay in the alarm system, this provides sufficient buffer time for the first line of defense to operate, while ensuring that the second line of defense is activated in a timely manner. This aligns with the original intention of the multi-level synergistic approach, which is to progressively upgrade the response and improve system reliability and efficiency.

[0096] Example 12:

[0097] The main structure of this embodiment is the same as any one of embodiments 1 to 11. Further, in step S8), to increase the compressed air power, a variable frequency pressure equalizing fan is added, model FBD№10.0 / 2×55kW, with specific parameters: power 75kW; voltage 1140 / 660V; total air pressure 318-4680Pa; total air volume 550-1650Pa. / min.

[0098] Example 13:

[0099] The main structure of this embodiment is the same as any one of embodiments 1 to 12. Further, in step S1), the monitoring points 8 are distributed in a matrix form, and the distance between adjacent monitoring points 8 is 1m.

[0100] Mixed gas tests were conducted regularly at 8 monitoring points using a handheld multi-functional portable gas tester. The measured mixed gases included oxygen, carbon dioxide, and carbon monoxide.

[0101] Example 14:

[0102] The main structure of this embodiment is the same as any one of embodiments 1 to 13. Furthermore, an apparatus for multi-level coordinated prevention and control of low oxygen in the corner of mine return air includes a real-time oxygen concentration monitoring sensor, a sealing wall, an arc baffle, an ejector, a ventilation duct, and a processor.

[0103] Multiple real-time oxygen concentration monitoring sensors are spaced out in the return air tunnel area, the ejector installation area, and the return air corner area. All of these sensors are electrically connected to the processor. The spacing between adjacent real-time oxygen concentration monitoring sensors is equal.

[0104] The sealing wall is located at the return air corners on both sides. The sealing wall comprises coal bags, cement-based expanding material, and quick-setting foam. Several coal bags are stacked at the return air corners, with cement-based expanding material filling the gaps between adjacent coal bags. The outer surface of the framework formed by the coal bags and cement-based expanding material is sprayed with quick-setting foam.

[0105] The two arc-shaped baffles are respectively installed at the junction of the intake airway, the return airway, and the two side sealing walls. An audible and visual alarm module is integrated into each arc-shaped baffle. The audible and visual alarm module is electrically connected to the processor.

[0106] The arc-shaped baffle 5 includes a rotating shaft, a baffle body, and an electromagnetic actuator. The baffle body is an arc-shaped baffle, and its top side is fixed to a roadway roof support via the rotating shaft. The electromagnetic actuator is fixed to the roadway roof or sidewall. The electromagnetic actuator includes a servo motor, an electromagnetic brake, a reduction gear transmission mechanism, and an angle sensor. The servo motor is connected to the electromagnetic brake. The electromagnetic brake is connected to the reduction gear transmission mechanism. The reduction gear transmission mechanism is connected to the rotating shaft. An angle sensor is mounted on the rotating shaft. Both the servo motor and the angle sensor are electrically connected to a processor. The electromagnetic brake is a normally closed type; in operation, it drives the servo motor, allowing the baffle body to rotate relative to the rotating shaft. The concave surface of the baffle body faces the working surface.

[0107] The ejector is installed in the return airway and includes an air inlet and an air outlet. The air inlet faces the area to be treated. The air outlet is connected to the ventilation duct. The end of the ejector near the air inlet is connected to the downhole compressed air pipeline via a pipeline. The ejectors are electrically connected to each other.

[0108] The air inlet of the ejector is positioned higher than the air outlet. The air outlet is 2.0-2.5m from the upper coal wall of the return airway and 0.8-1.0m from the roof. A rotatable guide shroud is installed at the air inlet of the ejector. An electromagnetic valve and an alarm are mounted on the ejector. Both the electromagnetic valve and the alarm are electrically connected to the processor.

[0109] The device also includes a variable frequency equalizing fan, which is arranged in parallel with the ejector in the return airway.

[0110] Example 15:

[0111] The main structure of this embodiment is the same as any one of embodiments 1 to 14. Furthermore, a corner gas "blocking-guiding-extraction" prevention technology includes the following steps:

[0112] 1) Determine the scope of governance

[0113] The oxygen concentration and low-oxygen range distribution in the return air corner of the working face were measured. Multiple gas detectors were installed in sections to monitor the oxygen concentration in the return air corner space multiple times during morning maintenance, afternoon production, and evening inspection times. The average value was taken to obtain the change in the low-oxygen range of the working face. The treatment area was determined based on the size and degree of low oxygen range.

[0114] 2) Lay out expansion material to fill the "air-blocking" area.

[0115] Based on parameters such as the pressure difference between the goaf and the working face, and the length of the seepage zone in the goaf, the air leakage resistance is calculated. The composition and amount of sealing material are determined according to the sealing area and the air leakage resistance. For the sealing construction of the return air corner of the working face, an appropriate amount of coal bags are prepared according to the area of ​​the sealing area of ​​the return air corner of the working face and stacked to form a sealing skeleton for the first sealing. Cement-based expansion material is filled into the gaps between the coal bags for the second sealing. Quick-setting foam is sprayed on the surface of the coal bag skeleton for the third sealing, so as to achieve the sealing and isolation of the low oxygen source.

[0116] In step 2), the expansion sealing material mainly comprises: coal bag skeleton, cement-based expansion material, and quick-setting foam;

[0117] In step 2), the amount of sealing material used is mainly calculated based on the air leakage resistance of the sealing area and the sealing area measured in step 4.

[0118] In step 2), the cement-based expansive material primarily functions to connect the coal bags and fill the gaps between them. The cement-based expansive material comprises the following components by weight: 23.6–26.5 parts ultrafine silicate cement, 1.20–8.00 parts ettringite, and 0.05–3 parts cement-based penetrating crystalline waterproofing masterbatch.

[0119] In step 2), the main function of the expansion component is to form a large amount of expansion products after the expansion component reacts with the cement slurry through stirring and hydration to fill the pores and prevent the cement from detaching from the skeleton due to cement shrinkage.

[0120] In step 2), the self-healing component has the following main function: after the cement-based material is damaged and cracks are generated, the self-healing component will permeate and crystallize upon contact with water to fill the cracks, thereby reducing the risk of the secondary seepage channels in the sealed area being re-formed.

[0121] In step 2), the rapid-setting foam primarily functions to cover and seal the area, filling in corners and gaps that the skeleton cannot reach, thereby further reducing leakage. Its main components include: ① resin, 80%; ② catalyst, 20%.

[0122] 3) Lay out curved baffles to "guide the air".

[0123] An arc-shaped baffle is installed in front of the return air corner, integrating a real-time oxygen concentration monitoring sensor, an electromagnetic actuator, and an audible and visual alarm module. When the oxygen concentration at the monitoring point behind the first-level barrier (sealing material) falls below a set threshold, the system automatically triggers a feedback mechanism. The lifting angle of the arc surface is adjusted according to the site conditions, transforming the corner from a right angle to an arc surface. This effectively increases the wind speed near the corner and eliminates the vortex phenomenon formed by the right-angle turn, which is highly beneficial for the airflow to promptly remove low-oxygen gases from the area near the corner.

[0124] 4) Install the ejector "air intake".

[0125] The KZQ40-18 combined air expander is selected. The ejector can be connected to the underground compressed air pipeline. Compressed air enters the radial annular space, where it is throttled at the annular gap. After passing through a chamfered structure, a high-speed airflow is generated. During the flow through the chamfer, a low-pressure area is created in the center. Due to the continuity of the gas and the effect of negative pressure, air behind the ejector is introduced and mixed with the high-speed jet of compressed air before being ejected through the diffuser. This dilutes gases such as carbon dioxide and carbon monoxide in the upper corner. Simultaneously, to avoid poor air guiding effect of the ejector, one FBD№10.0 / 2×55kW variable frequency pressure equalizing fan can be used to appropriately increase the compressed air power. The ejector outlet should be 2.0-2.5m away from the upper coal wall of the return airway and 0.8-1.0m away from the roof. The ejector inlet side should be slightly higher, i.e., at an elevation angle of 5°. The ejector is suspended, and a duct can be connected to the ejector outlet to guide and disperse the air at the point of lowest oxygen concentration. Simultaneously, oxygen concentration sensors, solenoid valves, and alarms are installed on the ejector as emergency reinforcement measures. If the current two-level measures fail to restore the ambient oxygen concentration to a safe threshold, the control system will activate the ejector to introduce external oxygen-enriched air, forming a directional jet to rapidly increase the oxygen partial pressure in the work area and forcibly expel accumulated carbon dioxide, carbon monoxide, and other gases.

[0126] The KZQ40-18 combined wind power extender is a high-volume ejector with an ejector air volume of 300-400. / min; Dimensions ø550mm×800mm; Working air pressure >0.5MPa; Weight 30kg; Air outlet ø550mm; Air consumption 5.2 / min.

[0127] The FBD№10.0 / 2×55kW variable frequency equalizing fan has a power of 75kW, a voltage of 1140 / 660V, a total air pressure of 318-4680Pa, and a total air volume of 550-1650. / min.

[0128] 5) Monitor the gas concentration at the return air corner.

[0129] Monitoring points were set up at locations where low oxygen levels frequently occurred, such as the return air corner of the low-oxygen working face. The monitoring area should include a portion of the return airway, the return air corner area, and the area near the ejector. The horizontal and vertical spacing between each monitoring point was 1 meter to monitor the effectiveness of multi-level coordinated control technology for the treatment of gases such as carbon dioxide and carbon monoxide. The flow meter operator conducted a five-minute mixed gas test using a handheld multi-functional portable gas analyzer and recorded the results. On-site oxygen levels were also measured. ),carbon dioxide( ) and carbon monoxide ( The concentration of ).

[0130] Within 7 days of implementing the "block-guide-guide" technology, measurements should be taken every other shift, three shifts a day; after 7 days, measurements should be taken every other day. The oxygen concentration threshold is determined according to the "Coal Mine Safety Regulations".

[0131] 6) Combined prevention and control measures including expansion material filling, return air corner arc baffles, and ejectors.

[0132] The first level of protection uses expanded material filling as a primary barrier, preferentially intercepting and adsorbing gases such as carbon dioxide and carbon monoxide, slowing their diffusion rate, and improving local oxygen concentration stability. This is suitable for normal and mild gas disturbance conditions. The second level of protection introduces an intelligent adjustable arc-shaped baffle structure, integrating a real-time oxygen concentration monitoring sensor, an electromagnetic actuator, and an audible and visual alarm module. When the oxygen concentration at the monitoring point behind the first level of protection falls below a set threshold, the system automatically triggers a feedback mechanism, adjusting the intake airflow field via electromagnetic valves and dynamically adjusting the angle of the arc-shaped baffle to optimize airflow organization, blocking the rapid advance of high-concentration carbon dioxide and carbon monoxide gas masses, achieving adaptive response in airflow guidance and dilution control. The third level of protection is equipped with an active ejector ventilation device as an emergency reinforcement measure. If the first two levels of protection fail to restore the ambient oxygen concentration to a safe threshold, the control system activates the ejector, introducing external oxygen-rich air to form a directional jet, rapidly increasing the oxygen partial pressure in the work area, and forcibly expelling accumulated carbon dioxide, carbon monoxide, and other gases. Simultaneously, an alarm is activated to notify the mine safety department, promptly reminding relevant personnel to conduct an investigation, thus achieving dynamic prevention and control through multiple combined measures. The oxygen concentration threshold is determined according to the "Coal Mine Safety Regulations".

Claims

1. A method for multi-level synergistic prevention and control of low oxygen levels in the corner of mine return air, characterized in that, Includes the following steps: S1. Divide the return airway area, ejector setting area and return air corner area into grids to obtain multiple uniformly arranged grid unit areas; take the center position of the grid unit area as the monitoring point (8) and set up a real-time oxygen concentration monitoring sensor at the monitoring point (8); S2. Lay sealing material (4) at the junction of the working face (1) and the goaf (2). S3. At the corners formed by the sealing material (4) and the intake airway (101) and the return airway (102), respectively, an arc-shaped baffle (5) is installed. S4. Align the air inlet (601) of the ejector (6) with the return air corner (3), connect the air outlet (602) to the air duct (7) located in the return air tunnel (102), and connect the end near the air inlet (601) to the underground compressed air pipeline through the pipeline (9); S5. Detect the oxygen concentration in the space range of the return air corner (3) by the real-time oxygen concentration monitoring sensor, and determine whether the current oxygen concentration is less than the safety threshold. If so, proceed to step S6; otherwise, continue to monitor the oxygen concentration in the space range of the return air corner (3). S6. Areas with oxygen concentrations below the safety threshold are designated as low-oxygen areas, and the area with the lowest oxygen concentration is selected as the area to be treated. The angle of the arc-shaped baffle (5) is adjusted by an electromagnetic actuator; S7. After time t, determine whether the oxygen concentration is less than the safety threshold using a real-time oxygen concentration monitoring sensor. If yes, proceed to step S8; otherwise, return to step S5. S8. Start the ejector (6) and introduce external oxygen-rich air through the pipeline (9) to form a directional jet to discharge the carbon dioxide and carbon monoxide accumulated in the return air corner (3) to the return air alley (102) until the oxygen concentration is greater than the safety threshold. Then, turn off the ejector (6) and return to step S5.

2. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air as described in claim 1, characterized in that: In step S2), filling the sealing material (4) includes the following steps: S2.1 Stack the coal bags in the corner of the return airway to form a sealing frame, thus completing one sealing operation; S2.2 Fill the gaps in the coal bags with cement-based expansion material to complete the secondary sealing; S2.

3. Spray quick-setting foam onto the surface of the sealing skeleton to complete the three-stage sealing process.

3. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air as described in claim 2, characterized in that: In step S2.2), the cement-based expansive material includes ultrafine silicate cement, ettringite, and cement-based penetrating crystalline waterproofing masterbatch, wherein the mass fractions of each material are as follows: The mass fraction of the ultrafine silicate cement is 23.6–26.

5. The mass fraction of the ettringite is 1.20–8.

00. The cement-based penetrating crystalline waterproof masterbatch has a mass fraction of 0.05–3%.

4. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air as described in claim 2, characterized in that: In step S2.3), the quick-setting foam comprises 80% resin by mass and 20% catalyst by mass.

5. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air as described in claim 1, characterized in that: In step S3), the inner arc surface of the arc-shaped windbreak (5) is set away from the corner; the sound and light alarm module is installed on the arc-shaped windbreak (5); The arc-shaped baffle (5) includes a rotating shaft, a baffle body, and an electromagnetic actuator; the baffle body is an arc-shaped baffle, and the top side of the arc-shaped baffle is fixed to the roadway roof support by the rotating shaft; the electromagnetic actuator is fixed to the roadway roof or sidewall. The electromagnetic actuator includes a servo motor, an electromagnetic brake, a reduction gear transmission mechanism, and an angle sensor; the servo motor is connected to the electromagnetic brake; the electromagnetic brake is connected to the reduction gear transmission mechanism; the reduction gear transmission mechanism is connected to a rotating shaft; an angle sensor is mounted on the rotating shaft; both the servo motor and the angle sensor are electrically connected to the processor; the electromagnetic brake is a normally closed type; the concave surface of the baffle body faces the working surface; During operation, the real-time oxygen concentration monitoring sensor transmits the collected data to the processor. The processor determines whether the current oxygen concentration is lower than the safety threshold. If so, the processor issues a control command to drive the servo motor, allowing the baffle body to rotate relative to the rotating shaft. If, after t seconds, the oxygen concentration collected by the real-time oxygen concentration monitoring sensor is still lower than the safety threshold, the processor issues a control command to activate the audible and visual alarm module, and the alarm will sound.

6. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air as described in claim 1, characterized in that: In step S4), the air inlet (601) of the ejector (6) is positioned higher than the air outlet (602); the air outlet (602) is 2.0-2.5m from the upper coal wall of the return airway (102) and 0.8-1.0m from the roof. The ejector (6) is equipped with an electromagnetic valve and an alarm. When adjusting the arc-shaped baffle (5) fails to make the oxygen concentration exceed the safety threshold, the processor issues a control command to open the solenoid valve to start the ejector (6) and simultaneously activate the alarm to alert the staff that the ejector (6) has been activated.

7. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air as described in claim 1, characterized in that: In step S4), a rotatable guide shroud is provided at the air inlet (601) of the ejector; when the ejector (6) needs to be started, the controller issues a control command to adjust the position of the rotatable guide shroud so that the rotatable guide shroud faces the area to be treated.

8. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air according to claim 1, characterized in that: In step S6), the criterion for determining the low-oxygen region is: when the oxygen concentration is detected to be below 20.9%, the corresponding grid cell region is divided into a low-oxygen region. During the monitoring process, the changes in the hypoxia range were analyzed based on the average oxygen concentration during the morning shift maintenance time, the afternoon shift production time, and the evening shift inspection time.

9. The method for multi-level coordinated prevention and control of low oxygen in the corner of mine return air according to claim 1, characterized in that: In step S8), a variable frequency equalizing fan is added to increase the compressed air power.

10. A multi-level synergistic prevention and control method for low oxygen levels in the corner of a mine return airway according to claim 1, characterized in that: In step S1), the monitoring points (8) are distributed in a matrix form, and the distance between adjacent monitoring points (8) is 1m; Mixed gas tests are conducted regularly at monitoring point (8). The mixed gas tests are conducted using a handheld multi-functional portable gas tester by a flow meter operator. The measured mixed gas includes oxygen, carbon dioxide and carbon monoxide.

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