Coal spontaneous combustion state evaluation method based on goaf CO production

Abstract

The application discloses a coal spontaneous combustion state evaluation method based on a goaf CO production amount, comprising the following steps: building a goaf CO gas detection and wind speed detection system, monitoring the working face CO concentration and the wind speed in real time, calculating the total circulating time T of the working face air inlet into the goaf and the total amount of CO escaping from the air return roadway in the T time length, calculating the total amount of the goaf oxidation temperature zone residual coal, calculating the CO concentration of the goaf residual coal generated per minute, judging whether the CO concentration of the goaf residual coal generated per minute exceeds the set alarm threshold a, if yes, there is a hidden danger of coal fire disaster, and the staff is immediately alarmed, otherwise, the working face CO concentration and the wind speed are continuously monitored. The application judges whether the CO concentration of the goaf oxidation temperature zone residual coal exceeds the set early warning value, and then judges whether the goaf has a hidden danger of coal fire disaster, thereby solving the problem that the evaluation result accuracy of the existing goaf coal spontaneous combustion state evaluation method is low.

Description

Technical Field

[0001] This invention belongs to the field of gas concentration detection technology and relates to a method for assessing the spontaneous combustion state of coal based on CO production in goaf areas. Background Technology

[0002] Spontaneous combustion of coal is one of the most common hazards during coal mining and storage. Internal fires caused by the spontaneous combustion of residual coal in goaf areas, resulting in light and heat emission, are a major cause of mine fires. As the primary indicator gas for spontaneous combustion of coal, CO is crucial in actual production for determining the state of spontaneous combustion by detecting its production.

[0003] For example, Chinese patent application number CN201610065635.9, entitled "A Method for Judging and Early Warning of the Risk of Coal Spontaneous Combustion in Goaf Based on Index Gas", discloses a method that involves deploying multiple CO gas concentration detectors in the goaf of a coal mine and connecting them to an underground monitoring host. The underground monitoring host then transmits the received signals to a ground monitoring computer via optical fiber and an industrial ring network, thereby achieving the purpose of early warning of coal fire hazards.

[0004] However, spontaneous combustion of coal in goaf areas is affected by a combination of factors, such as the amount of residual coal and air supply, which causes changes in the CO production rate. This makes it relatively difficult and inaccurate to judge the spontaneous combustion status of coal by monitoring the CO production in the return airway of the goaf alone. Summary of the Invention

[0005] The purpose of this invention is to provide a method for assessing the spontaneous combustion state of coal based on CO production in goaf areas, which solves the problem of low accuracy in existing methods for assessing the spontaneous combustion state of coal in goaf areas.

[0006] The technical solution adopted in this invention is a method for assessing the spontaneous combustion state of coal based on CO production in goaf areas, comprising the following steps:

[0007] Step 1: Set up a CO gas detection and wind speed detection system in the goaf area;

[0008] Step 2: Monitor the CO gas concentration and wind speed at the working face in real time;

[0009] Step 3: Calculate the total circulation time T of the air intake from the working face into the goaf.

[0010] Step 4: Calculate the total amount of CO gas escaping from the return airway within time T based on the monitored CO gas concentration and wind speed at the working face.

[0011] Step 5: Calculate the total amount of residual coal in the oxidation and heating zone of the goaf, and estimate the CO gas concentration generated by the residual coal in the goaf per minute;

[0012] Step 6: Determine whether the CO gas concentration generated by the residual coal in the goaf per minute exceeds the set alarm threshold 'a'. If it exceeds the threshold, there is a potential coal fire hazard, and an alarm is immediately triggered to the staff. Otherwise, continue to monitor the CO gas concentration and wind speed at the working face.

[0013] In step 1, a CO gas detection and wind speed detection system for the goaf is established, including the installation of wind speed sensors in the intake and return airways to monitor the wind speed V in the intake airway in real time. j Wind speed V in the return airway h CO concentration sensors were installed in the upper corner and the return airway to monitor the CO gas concentration in the upper corner in real time. s CO gas concentration C in the return airway h All wind speed sensors and CO concentration sensors are connected to the local industrial control computer via fiber optic cables, and the local industrial control computer is connected to the ground-based host computer via a wireless network.

[0014] Both the wind speed sensor and the CO concentration sensor are installed near the top plate. The wind speed sensor in the intake airway is 18m to 22m from the lower corner, the wind speed sensor in the return airway is 18m to 22m from the upper corner, and the CO concentration sensor in the return airway is 28m to 32m from the upper corner.

[0015] The specific process of step 3 is as follows:

[0016] Step 3.1, measure the farthest distance M between the oxidation heating zone on the air inlet side and the working face. ja And the closest distance M ji The farthest distance M from the oxidation heating zone on the return air side to the working face was measured. ha And the closest distance M hi ;

[0017] Step 3.2: Calculate the transport distance of the intake airflow within the goaf, obtaining the transport distance M of the intake airflow within the goaf. z ;

[0018] Step 3.3 divides the airflow's movement distance in the goaf into three stages: the distance M from the air intake side into the goaf but before entering the oxidation and heating zone. z1 The airflow velocity is selected from the inlet airway velocity V. j The distance M from the return air side into the goaf without entering the oxidation and heating zone z3 The airflow velocity is selected from the return airway velocity V. h ; and the distance M to enter the oxidation heating zone z2 The airflow velocity was chosen to be a constant of 0.2 m / min;

[0019] Step 3.4, calculate the transport time of underground airflow into the goaf, i.e., the total circulation time T of the air intake from the working face into the goaf:

[0020]

[0021] The specific process of step 3.2 is as follows:

[0022] Step 3.2.1: Set the spatial origin for calculating the airflow movement distance in the goaf as the midpoint (0, 0) of the working face, and obtain the coordinate positions of the upper and lower corners in the space, which are (0, m / 2) and (0, -m / 2) respectively, where m is the length of the working face;

[0023] Step 3.2.2, set the coordinates of the point where the relative movement of the airflow is farthest as ((M ja +M ha ) / 2,0);

[0024] Step 3.2.3: Define the airflow path within the goaf as a sector with radius R and center x0. Calculate the center position of the airflow path. Since the upper and lower corners form an isosceles triangle with the point of furthest relative movement of the airflow, the perpendicular bisector formula for the upper and lower corners is y0 = 0. The perpendicular bisector of the upper corner and the point of furthest relative movement of the airflow is y0 = 0. a And the perpendicular bisector y of the lower corner and the point of furthest relative movement. b The expressions are as follows:

[0025]

[0026] In the formula, b is an intermediate variable, and the intersection of the three perpendicular bisectors is (m(b-1) / 4b, 0), which is the center position of the airflow path.

[0027] Step 3.2.4, calculate the angle β between the corners of the center position of the airflow path:

[0028]

[0029] Step 3.2.5: Calculate the transport distance M of the intake airflow in the goaf. z :

[0030]

[0031] In step 3.3, M z1 M z2 and M z3 The calculation process is as follows:

[0032] Step 3.3.1: Calculate the two intersection points (x1, y1) and (x2, y2) between the fan-shaped airflow path in the goaf and the nearest oxidation heating zone:

[0033]

[0034]

[0035] In the formula, b2 is an intermediate variable;

[0036] Step 3.3.2: Calculate the distance between the two intersection points and the corresponding corner positions to obtain M. z1 M z2 and M z3 :

[0037]

[0038] In the formula, A1 is the lower corner angle, the angle formed by (x0, 0) and (x1, y1), and A3 is the upper corner angle, the angle formed by (x0, 0) and (x2, y2).

[0039] Step 4 is as follows:

[0040] Step 4.1: Real-time reading of the CO concentration value C detected by the CO concentration sensor at the upper corner. s ;

[0041] Step 4.2, determine C s If the concentration is above the threshold of 24 ppm, there is a risk of disaster, and the staff should be alerted immediately; otherwise, proceed to step 4.3.

[0042] Step 4.3, Real-time reading of C h With V h Calculate the total amount of CO gas emitted from the return airway Y within the same time period T. s :

[0043] Y s =T*S h *V h *C h (8)

[0044] In the formula, S h This indicates the cross-sectional area of ​​the return airway where the CO concentration sensor is installed.

[0045] Step 5 is as follows:

[0046] Step 5.1, calculate the area S of the oxidation heating zone. y :

[0047]

[0048] Step 5.2: Calculate the total amount of residual coal in the oxidation and heating zone of the goaf, and the volume V of the residual coal in the oxidation and heating zone. y for:

[0049] Vy =S y H (10)

[0050] In the formula, H is the height of the overlying coal seam in the goaf;

[0051] Step 5.3, calculate the CO gas concentration C produced per minute by the residual coal in the goaf. z :

[0052]

[0053] The beneficial effect of this invention is that by real-time monitoring of CO gas concentration and wind speed at the working face, the total circulation time of the intake air entering the goaf and the total amount of CO gas escaping in the return air roadway are calculated, thereby estimating the CO gas concentration generated by the residual coal in the oxidation and heating zone of the goaf, and finally determining whether the CO gas concentration exceeds the set warning value, thereby determining whether there is a potential coal fire hazard in the goaf. Attached Figure Description

[0054] Figure 1 This is a flowchart illustrating the method for assessing the spontaneous combustion state of coal based on CO production in goaf areas according to the present invention.

[0055] Figure 2 This is a schematic diagram of the CO gas detection and wind speed detection system for the goaf area constructed in this invention.

[0056] In the figure, 1. Oxidation heating zone, 2. Goaf, 3. Intake airway, 4. Working face, 5. Return airway, 6. Coal seam, 7. Support, 8. Wind speed sensor, 9. CO concentration sensor, 10. Goaf airflow path. Detailed Implementation

[0057] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0058] Example 1

[0059] A method for assessing the spontaneous combustion state of coal based on CO production in goaf areas, referring to Figure 1 This includes the following steps:

[0060] Step 1: Establish a CO gas detection and wind speed detection system for the goaf area, referring to... Figure 2 This includes installing wind speed sensors 8 in the intake airway 3 and the return airway 5 respectively, to monitor the wind speed V in the intake airway 3 in real time. j Wind speed V in return air alley h The intake airway 3 and return airway 5 are located on both sides of the coal seam 6. The other side of the coal seam 6 is the working face 4. A support 7 is installed on the side of the working face 4 closest to the goaf 2. CO concentration sensors 9 are installed in the upper corner and in the middle of the return airway 5 to monitor the CO gas concentration C in the upper corner in real time.s CO gas concentration C in the return airway h Both the wind speed sensor 8 and the CO concentration sensor 9 are installed near the top plate. The wind speed sensor 8 in the intake airway 3 is 18m away from the lower corner, the wind speed sensor 8 in the return airway 5 is 18m away from the upper corner, and the CO concentration sensor 9 in the return airway 5 is 32m away from the upper corner.

[0061] In this embodiment, the wind speed sensor 8 is an intrinsically safe wind speed sensor, and the CO concentration sensor 9 is an intrinsically safe diffuse reflection CO laser sensor. Both the wind speed sensor 8 and the CO concentration sensor 9 are connected to the local industrial control computer via optical fiber. The local industrial control computer is connected to the ground-based host computer via a wireless network.

[0062] Step 2: Obtain the CO gas concentration and wind speed of the working face 4 by reading the readings of the installed wind speed sensor 8 and CO concentration sensor 9 in real time. By reading the timestamps of the two modes of signals from the wind speed sensor and CO concentration sensor, ensure that the readings of the four sensors are within the same time.

[0063] Step 3: Calculate the total circulation time T of the air intake from working face 4 into goaf 2;

[0064] Step 4: Calculate the total amount of CO gas escaping from the return airway 5 within time T based on the monitored CO gas concentration and wind speed at the working face.

[0065] Step 5: Calculate the total amount of residual coal in oxidation heating zone 1 within goaf 2, and estimate the CO gas concentration generated per minute by the residual coal within goaf 2.

[0066] Step 6: Determine whether the CO gas concentration generated by the residual coal in the goaf 2 per minute exceeds the set alarm threshold a. If it exceeds the threshold, there is a potential coal fire hazard, and an alarm is immediately triggered to the staff. Otherwise, continue to monitor the CO gas concentration and wind speed at the working face.

[0067] Example 2

[0068] A method for assessing the spontaneous combustion status of coal based on CO production in goaf areas includes the following steps:

[0069] Step 1: Construct a CO gas detection and wind speed detection system for the goaf, including installing wind speed sensors 8 in the intake airway 3 and return airway 5 respectively, to monitor the wind speed V in the intake airway 3 in real time. j Wind speed V in return air alley h CO concentration sensors 9 are installed in the upper corner and the middle part of the return airway 5 to monitor the CO gas concentration C in the upper corner in real time. s CO gas concentration C in the return airway hBoth the wind speed sensor 8 and the CO concentration sensor 9 are installed near the top plate. The wind speed sensor 8 in the intake airway 3 is 22m away from the lower corner, the wind speed sensor 8 in the return airway 5 is 22m away from the upper corner, and the CO concentration sensor 9 in the return airway 5 is 28m away from the upper corner.

[0070] Both wind speed sensor 8 and CO concentration sensor 9 are connected to the local industrial control computer via optical fiber, and the local industrial control computer is connected to the ground-based host computer via wireless network.

[0071] Step 2: Obtain the CO gas concentration and wind speed of the working face 4 by reading the readings of the installed wind speed sensor 8 and CO concentration sensor 9 in real time. By reading the timestamps of the two modes of signals from the wind speed sensor 8 and CO concentration sensor 9, ensure that the readings of the four sensors are within the same time.

[0072] Step 3: Calculate the total circulation time T of the air intake from working face 4 into goaf 2. The specific process is as follows:

[0073] Step 3.1, measure the farthest distance M between the air inlet side oxidation heating zone 1 and the working face 4. ja And the closest distance M ji The farthest distance M from the oxidation heating zone on the return air side to the working face 4 was measured. ha And the closest distance M hi ;

[0074] Step 3.2: Calculate the transport distance of the intake airflow within the goaf, obtaining the transport distance M of the intake airflow within the goaf. z ;

[0075] Step 3.3 divides the airflow's movement distance in the goaf into three stages: the distance M from the air intake side into the goaf but before entering the oxidation and heating zone. z1 The airflow velocity is selected from the inlet airway velocity V. j The distance M from the return air side into the goaf without entering the oxidation and heating zone z3 The airflow velocity is selected from the return airway velocity V. h ; and the distance M to enter the oxidation heating zone z2 The airflow velocity was chosen to be a constant of 0.2 m / min;

[0076] Step 3.4, calculate the transport time of underground airflow into the goaf, i.e., the total circulation time T of the air intake from the working face into the goaf:

[0077]

[0078] Step 4: Calculate the total CO gas emission from the return airway within time T based on the monitored CO gas concentration and wind speed at the working face. The specific process is as follows:

[0079] Step 4.1: Real-time reading of the CO concentration value C detected by the CO concentration sensor at the upper corner. s ;

[0080] Step 4.2, determine C s If the concentration is above the threshold of 24 ppm, there is a risk of disaster, and the staff should be alerted immediately; otherwise, proceed to step 4.3.

[0081] Step 4.3, Real-time reading of C h With V h Calculate the total amount of CO gas escaping from the return airway Y within the same time period T. s :

[0082] Y s =T*S h *V h *C h (2)

[0083] In the formula, S h This indicates the cross-sectional area of ​​the return airway where the CO concentration sensor is installed.

[0084] Step 5: Calculate the CO gas concentration produced per minute by the residual coal in the goaf. The specific process is as follows:

[0085] Step 5.1, calculate the area S of the oxidation heating zone. y :

[0086]

[0087] In the formula, m is the length of the working surface;

[0088] Step 5.2: Calculate the total amount of residual coal in the oxidation-heating zone within the goaf, and the volume V of the residual coal in the oxidation-heating zone. y for:

[0089] V y =S y H (4)

[0090] In the formula, H is the height of the overlying coal seam in the goaf;

[0091] Step 5.3, calculate the CO gas concentration C produced per minute by the residual coal in the goaf. z :

[0092]

[0093] Step 6: Determine whether the CO gas concentration generated by the residual coal in the goaf per minute exceeds the set alarm threshold 'a'. If it exceeds the threshold, there is a potential coal fire hazard, and an alarm is immediately triggered to the staff. Otherwise, continue to monitor the CO gas concentration and wind speed at the working face.

[0094] Example 3

[0095] A method for assessing the spontaneous combustion status of coal based on CO production in goaf areas includes the following steps:

[0096] Step 1: Construct a CO gas detection and wind speed detection system for the goaf, including installing wind speed sensors 8 in the intake airway 3 and return airway 5 respectively, to monitor the wind speed V in the intake airway 3 in real time. j Wind speed V in the return airway h CO concentration sensors 9 are installed in the upper corner and the middle of the return airway to monitor the CO gas concentration C in the upper corner in real time. s CO gas concentration C in the return airway h Both the wind speed sensor 8 and the CO concentration sensor 9 are installed near the top plate. The wind speed sensor 8 in the intake airway 3 is 20m away from the lower corner, the wind speed sensor 8 in the return airway 5 is 20m away from the upper corner, and the CO concentration sensor 9 in the return airway 5 is 30m away from the upper corner.

[0097] Both wind speed sensor 8 and CO concentration sensor 9 are connected to the local industrial control computer via optical fiber, and the local industrial control computer is connected to the ground-based host computer via wireless network.

[0098] Step 2: Obtain the CO gas concentration and wind speed of the working face 4 by reading the readings of the installed wind speed sensor 8 and CO concentration sensor 9 in real time. By reading the timestamps of the two modes of signals from the wind speed sensor 8 and CO concentration sensor 9, ensure that the readings of the four sensors are within the same time.

[0099] Step 3: Calculate the total circulation time T of the air intake from working face 4 into goaf 2. The specific process is as follows:

[0100] Step 3.1, measure the farthest distance M between the oxidation heating zone on the air inlet side and the working face. ja And the closest distance M ji The farthest distance M from the oxidation heating zone on the return air side to the working face was measured. ha And the closest distance M hi ;

[0101] Step 3.2: Calculate the transport distance of the intake airflow within the goaf, obtaining the transport distance M of the intake airflow within the goaf. z ;

[0102] The specific process of step 3.2 is as follows:

[0103] Step 3.2.1: Set the spatial origin for calculating the airflow movement distance in the goaf as the midpoint (0, 0) of the working face, and obtain the coordinate positions of the upper and lower corners in the space, which are (0, m / 2) and (0, -m / 2) respectively, where m is the length of the working face;

[0104] Step 3.2.2: Set the point where the airflow moves the furthest distance as the center point of the furthest oxidation heating zone, with the corresponding coordinates as ((M ja +M ha ) / 2,0);

[0105] Step 3.2.3: Set the airflow path within the goaf to a fan shape, that is, set the goaf airflow path 10 to a fan shape (see...). Figure 2 To calculate the center position of the airflow path in the goaf, since the upper and lower corners form an isosceles triangle with the point where the airflow moves the furthest relative distance, the formula for the perpendicular bisectors of the upper and lower corners is y0 = 0. The perpendicular bisector of the upper corner with the point where the airflow moves the furthest relative distance is y0 = 0. a And the perpendicular bisector y of the lower corner and the point of furthest relative movement. b The expressions are as follows:

[0106]

[0107] In the formula, b is an intermediate variable, and the intersection of the three perpendicular bisectors is (m(b-1) / 4b, 0), which is the center position of the airflow path.

[0108] Step 3.2.4, calculate the angle β between the corners of the center position of the airflow path:

[0109]

[0110] Step 3.2.5: Calculate the transport distance M of the intake airflow in the goaf. z :

[0111]

[0112] Step 3.3 divides the airflow's movement distance in the goaf into three stages: the distance M from the air intake side into the goaf but before entering the oxidation and heating zone. z1 The airflow velocity is selected from the inlet airway velocity V. j The distance M from the return air side into the goaf without entering the oxidation and heating zone z3 The airflow velocity is selected from the return airway velocity V. h And the distance M from entering the oxidation heating zone z2 The airflow velocity was chosen to be a constant of 0.2 m / min;

[0113] M z1 M z2 and M z3 The calculation process is as follows:

[0114] Step 3.3.1: Calculate the two intersection points (x1, y1) and (x2, y2) between the fan-shaped airflow path in the goaf and the nearest oxidation heating zone:

[0115]

[0116] In the formula, b2 is an intermediate variable;

[0117] Step 3.3.2: Calculate the distance between the two intersection points and the corresponding corner positions to obtain M. z1 M z2 and M z3 :

[0118]

[0119] In the formula, A1 is the lower corner angle, the angle formed by (x0, 0) and (x1, y1), and A3 is the upper corner angle, the angle formed by (x0, 0) and (x2, y2).

[0120] Step 3.4, calculate the transport time of underground airflow into the goaf, i.e., the total circulation time T of the air intake from the working face into the goaf:

[0121]

[0122] Step 4: Calculate the total CO gas emission from the return airway within time T based on the monitored CO gas concentration and wind speed at the working face. The specific process is as follows:

[0123] Step 4.1: Real-time reading of the CO concentration value C detected by the CO concentration sensor at the upper corner. s ;

[0124] Step 4.2, determine C s If the concentration is above the threshold of 24 ppm, there is a risk of disaster, and the staff should be alerted immediately; otherwise, proceed to step 4.3.

[0125] Step 4.3, Real-time reading of C h With V h Calculate the total amount of CO gas escaping from the return airway Y within the same time period T. s :

[0126] Y s =T*S h *V h *C h (8)

[0127] In the formula, S h This indicates the cross-sectional area of ​​the return airway where the CO concentration sensor is installed.

[0128] Step 5: Calculate the CO gas concentration produced per minute by the residual coal in the goaf. The specific process is as follows:

[0129] Step 5.1, calculate the area S of the oxidation heating zone. y :

[0130]

[0131] Step 5.2: Calculate the total amount of residual coal in the oxidation-heating zone within the goaf, and the volume V of the residual coal in the oxidation-heating zone. y for:

[0132] V y =S y H (10)

[0133] In the formula, H is the height of the overlying coal seam in the goaf;

[0134] Step 5.3, calculate the CO gas concentration C produced per minute by the residual coal in the goaf. z :

[0135]

[0136] Step 6: Determine whether the CO gas concentration generated by the residual coal in the goaf per minute exceeds the set alarm threshold 'a'. If it exceeds the threshold, there is a potential coal fire hazard, and an alarm is immediately triggered to the staff. Otherwise, continue to monitor the CO gas concentration and wind speed at the working face.

Claims

1. A method for assessing the spontaneous combustion state of coal based on CO production in goaf areas, characterized in that, Includes the following steps: Step 1: Construct a CO gas detection and wind speed detection system for the goaf, including installing wind speed sensors (8) in the intake airway (3) and return airway (5) respectively, to monitor the wind speed in the intake airway (3) in real time. V j Wind speed in the return air alley (5) V h CO concentration sensors (9) are installed in the upper corner and the return airway (5) respectively to monitor the CO gas concentration in the upper corner in real time. C s CO gas concentration in return airway (5) C h All wind speed sensors (8) and CO concentration sensors (9) are connected to the local industrial computer via optical fiber, and the local industrial computer is connected to the ground host computer via wireless network. Step 2: Monitor the CO gas concentration and wind speed at the working face (4) in real time; Step 3, calculate the total circulation time T of the air intake from the working face (4) into the goaf (2); The specific process of step 3 is as follows: Step 3.1, measure the farthest distance between the air inlet side oxidation heating zone (1) and the working face (4). M ja and closest distance M ji Measure the farthest distance between the return air side oxidation heating zone (1) and the working face (4). M ha and closest distance M hi ; Step 3.2, calculate the transport distance of the intake airflow within the goaf (2), and obtain the transport distance of the intake airflow within the goaf (2) as follows: M z ; The specific process of step 3.2 is as follows: Step 3.2.1: Set the spatial origin for calculating the airflow movement distance in the goaf (2) as the midpoint (0, 0) of the working face (4), and obtain the coordinate positions of the upper and lower corners in the space, which are (0, ... m / 2), (0, - m / 2), where m is the length of the working surface; Step 3.2.2, set the coordinates of the point where the relative movement of the airflow is farthest as (( M ja + M ha ) / 2, 0); Step 3.2.3: Set the airflow path within the goaf (2) as a sector, with a sector radius of R and a sector center x-coordinate of R. x 0. Calculate the center position of the airflow path. Since the upper and lower corners form an isosceles triangle with the point where the airflow travels the furthest distance relative to the upper and lower corners, the formula for the perpendicular bisectors of the upper and lower corners is: y 0=0, the perpendicular bisector of the upper corner angle and the point where the relative movement of the airflow is the farthest. y a And the perpendicular bisector of the lower corner and the point of furthest relative movement. y b The expressions are as follows: （1） In the formula, b is an intermediate variable, and the intersection of the three perpendicular bisectors is (m(b-1) / 4b, 0), which is the center position of the airflow path. Step 3.2.4: Calculate the angle between the corners of the center position of the airflow path. β : （2） Step 3.2.5: Calculate the transport distance of the intake airflow in the goaf. M z : （3） Step 3.3: Divide the airflow distance in the goaf (2) into three stages, namely the distance from near the air intake side into the goaf (2) to before entering the oxidation heating zone (1). M z1 The airflow velocity is selected from the intake airway velocity. V j The distance from the return air side into the goaf (2) to the oxidation heating zone (1) M z3 The airflow velocity is selected from the return airway velocity. V h and the distance to enter the oxidation heating zone (1) M z2 The airflow velocity was chosen to be a constant of 0.2 m / min; In step 3.3, M z1 , M z2 and M z3 The calculation process is as follows: Step 3.3.1, calculate the two intersection points between the fan-shaped airflow path in the goaf and the nearest oxidation heating zone ( x 1, y 1) and ( x 2, y 2): （4） （5） In the formula, b2 is an intermediate variable; Step 3.3.2: Calculate the distances between the two intersection points and the corresponding corner positions to obtain... M z1 , M z2 and M z3 : （6） In the formula, A1 is the lower corner angle, ( x 0,0) and ( x 1, y 1) The angle formed, A3 is the upper corner angle, ( x 0,0) and ( x 2, y 2) The angle of composition; Step 3.4, calculate the transport time of the underground airflow into the goaf (2), that is, the total circulation time T of the air intake from the working face into the goaf (2): （7） Step 4: Calculate the total amount of CO gas escaping from the return airway (5) within time T based on the CO gas concentration and wind speed at the monitored working face (4); The specific process of step 4 is as follows: Step 4.1: Read the CO concentration value detected by the CO concentration sensor (9) at the upper corner in real time. C s ; Step 4.2, Determine C s If the concentration is above the threshold of 24 ppm, there is a risk of disaster, and the staff should be alerted immediately; otherwise, proceed to step 4.

3. Step 4.3, Real-time Reading C h and V h , calculation same T Total CO gas emission from return airway (5) within the specified time period Y s : （8） In the formula, S h This represents the cross-sectional area of ​​the return airway where the CO concentration sensor (9) is installed; Step 5: Calculate the total amount of residual coal in the oxidation heating zone (1) within the goaf (2), and estimate the CO gas concentration generated per minute by the residual coal within the goaf (2). The specific process of step 5 is as follows: Step 5.1, calculate the area of ​​the oxidation heating zone (1). S y : （9） Step 5.2, calculate the total amount of residual coal in the oxidation heating zone (1) within the goaf (2), and the volume of residual coal in the oxidation heating zone (1). V y for: （10） In the formula, H The height of the overlying coal seam in the goaf (2); Step 5.3, calculate the CO gas concentration generated per minute by the residual coal in the goaf (2). C z : （11） Step 6: Determine whether the CO gas concentration generated by the residual coal in the goaf (2) per minute exceeds the set alarm threshold. a If the concentration of CO gas exceeds the limit, there is a risk of coal fire. Immediately alert the staff. Otherwise, continue to monitor the CO gas concentration and wind speed at the working face (4).

2. The method for assessing the spontaneous combustion state of coal based on CO production in goaf areas according to claim 1, characterized in that, The wind speed sensor (8) and CO concentration sensor (9) are both installed near the top plate. The wind speed sensor (8) in the air intake tunnel (3) is 18m to 22m away from the lower corner, the wind speed sensor (8) in the air return tunnel (5) is 18m to 22m away from the upper corner, and the CO concentration sensor (9) in the air return tunnel (5) is 28m to 32m away from the upper corner.

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