Coal spontaneous combustion state evaluation method based on goaf CO output

Abstract

The invention discloses a coal spontaneous combustion state evaluation method based on goaf CO output, which comprises the following steps: building a goaf CO gas detection and wind speed detection system, monitoring the CO concentration and wind speed of a working face in real time, calculating the total circulation time T of working face inlet air entering the goaf and the total loss amount of CO in a return airway within the time T, and evaluating the spontaneous combustion state of coal. Calculating the total amount of residual coal in the oxidation heating zone of the goaf, calculating the CO concentration generated by the residual coal in the goaf per minute, judging whether the CO concentration generated by the residual coal in the goaf per minute exceeds a set alarm threshold value a or not, if so, determining that the hidden danger of coal fire disaster exists and immediately giving an alarm to workers, otherwise, continuously monitoring the CO concentration of the working face and the wind speed. By judging whether the CO concentration generated by the residual coal in the oxidation heating zone in the goaf exceeds the set early warning value or not, whether the goaf has the hidden danger of coal fire disasters or not is judged, and the problem that an existing goaf coal spontaneous combustion state evaluation method is low in evaluation result accuracy is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of gas concentration detection and relates to a method for evaluating the spontaneous combustion state of coal based on the amount of CO produced in a goaf. Background Art

[0002] Coal spontaneous combustion is one of the most likely disasters to occur during coal mining and storage. The internal fire caused by the spontaneous combustion of coal in the goaf is the main cause of mine fires. CO is the main characteristic gas of coal spontaneous combustion. In actual production, it is particularly important to determine the state of coal spontaneous combustion by detecting its production.

[0003] For example, the Chinese patent application number CN201610065635.9, entitled “A method for distinguishing and warning the risk of spontaneous combustion of coal in goaf areas based on index gas” discloses that multiple CO gas concentration detectors are arranged in the goaf of a coal mine and connected to an underground monitoring host. The underground monitoring host transmits the received signals to a ground monitoring computer through communication optical fiber and an industrial ring network, thereby achieving the purpose of coal fire disaster risk warning.

[0004] However, spontaneous combustion of coal in goaf will be affected by the combined effects of the amount of coal left and air supply, which will cause the CO production rate to change. This makes it relatively difficult and inaccurate to monitor the CO production in the return air lane of the goaf alone to judge the state of coal spontaneous combustion. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the spontaneous combustion state of coal based on the amount of CO produced in goaf, thereby solving the problem of low accuracy of evaluation results of existing methods for evaluating the spontaneous combustion state of coal in goaf.

[0006] The technical solution adopted by the present invention is a method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in the goaf, comprising the following steps:

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

[0008] Step 2: Real-time monitoring of CO gas concentration and wind speed at the working face;

[0009] Step 3, calculating the total circulation time T of the air entering the goaf from the working face;

[0010] Step 4: Calculate the total amount of CO gas dissipated in the return air lane within a time period of T according to the monitored CO gas concentration and wind speed of the working face;

[0011] Step 5, calculating the total amount of coal residue in the oxidation and warming zone of the goaf, and inferring the CO gas concentration generated by the coal residue in the goaf per minute;

[0012] Step 6, determine whether the CO gas concentration generated by the coal residue in the goaf per minute exceeds the set alarm threshold a. If it exceeds, there is a hidden danger of coal fire disaster, and the staff will be alarmed immediately. Otherwise, continue to monitor the CO gas concentration and wind speed of the working face.

[0013] In step 1, a CO gas detection and wind speed detection system is built in the goaf, including installing wind speed sensors in the air intake and return air lanes to monitor the wind speed V in the air intake lane in real time. j and the wind speed V in the return air channel h , CO concentration sensors are installed in the upper corner and the middle of the return air lane to monitor the CO gas concentration C in the upper corner in real time. s and CO gas concentration in the return air channel C h ,All wind speed sensors and CO concentration sensors are connected to the local ,industrial computer through optical fiber, and the local industrial computer is connected to the ,surface host computer through a wireless network.

[0014] The wind speed sensor and CO concentration sensor are both installed close to the top plate. The wind speed sensor in the air inlet tunnel is 18m to 22m away from the lower corner, the wind speed sensor in the return air tunnel is 18m to 22m away from the upper corner, and the CO concentration sensor in the return air tunnel is 28m to 32m away from the upper corner.

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

[0016] Step 3.1: Measure the maximum distance M between the oxidation heating zone on the air inlet side and the working surface ja and the closest distance M ji Measure the maximum distance M between the oxidation heating zone on the return air side and the working surface ha and the closest distance M hi ;

[0017] Step 3.2, calculate the migration distance of the airflow in the goaf, and get the migration distance of the airflow in the goaf as M. z ;

[0018] Step 3.3, the airflow migration distance in the goaf is divided into three stages, namely, the distance M from the air inlet side into the goaf but not into the oxidation and heating zone z1 , the wind speed is selected as the wind speed V of the air inlet lane j ; The distance M from the return air side into the goaf but not into the oxidation heating zone z3 , the wind speed is selected as the return air lane wind speed V h ; and the distance M into the oxidation warming zone z2 , the wind speed is selected as a constant of 0.2m / min;

[0019] Step 3.4, calculate the migration time of underground airflow into the goaf, that is, the total circulation time T of the working face air entering the goaf:

[0020]

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

[0022] Step 3.2.1, set the spatial origin of the goaf for calculating the wind flow moving distance as the midpoint of the working face (0, 0), and obtain the corresponding coordinate positions of the upper corner and the lower corner 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 coordinate position of the point with the longest relative movement distance of the wind flow to ((M ja +M ha ) / 2,0);

[0024] Step 3.2.3, set the movement path of the wind flow in the goaf to a sector shape, with the sector radius as R and the horizontal coordinate of the center of the sector as x0, and calculate the center position of the wind flow movement path. Since the upper corner, the lower corner and the point with the farthest relative movement of the wind flow form an isosceles triangle, the formula of the perpendicular bisector corresponding to the upper corner and the lower corner is y0=0, and the perpendicular bisector y0 between the upper corner and the point with the farthest relative movement of the wind flow is a , and the perpendicular bisector y between the lower corner and the point with the longest relative movement b The expressions are:

[0025]

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

[0027] Step 3.2.4, calculate the angle β of the corner at the center of the wind flow moving path:

[0028]

[0029] Step 3.2.5, calculate the travel distance M of the airflow into 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) of the fan-shaped airflow path in the goaf and the closest oxidation warming zone:

[0033]

[0034]

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

[0036] Step 3.3.2, calculate the distance between the two intersection points and the corner position, and get M z1 、M z2 and M z3 :

[0037]

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

[0039] Step 4: The specific process is as follows:

[0040] Step 4.1: Read the CO concentration value C detected by the CO concentration sensor at the upper corner in real time s ;

[0041] Step 4.2, determine C s Is it higher than the threshold of 24ppm? If it is higher than the threshold, there is a disaster risk and the staff will be alerted immediately. Otherwise, go to step 4.3;

[0042] Step 4.3, real-time reading of C h With V h , calculate the total amount of CO gas Y that escapes from the return air tunnel within the same time T s :

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

[0044] In the formula, S h Indicates the cross-sectional area of ​​the return air duct where the CO concentration sensor is installed.

[0045] Step 5: The specific process 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 coal left in the oxidation and warming zone of the goaf, the volume V of the coal left in the oxidation and warming zone y for:

[0049] Vy =S y H (10)

[0050] Where, H is the height of the overlying coal in the goaf;

[0051] Step 5.3, calculate the CO gas concentration C generated by the coal in the goaf every minute z :

[0052]

[0053] The beneficial effect of the present invention is that by real-time monitoring of the CO gas concentration and wind speed of the working face, the total circulation time of the air entering the goaf from the working face and the total escape amount of CO gas in the return air tunnel are calculated, and then the CO gas concentration generated by the residual coal in the oxidation and warming zone in the goaf is deduced, and finally it is determined whether the CO gas concentration exceeds the set warning value, and then it is determined whether there is a hidden danger of coal fire disaster in the goaf. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a flow chart of the method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in the goaf according to the present invention;

[0055] Figure 2 It is a structural schematic diagram of the goaf CO gas detection and wind speed detection system constructed in the present invention.

[0056] In the figure, 1. oxidation warming zone, 2. goaf, 3. air intake tunnel, 4. working face, 5. return air tunnel, 6. coal seam, 7. support, 8. wind speed sensor, 9. CO concentration sensor, 10. air flow path in the goaf. DETAILED DESCRIPTION

[0057] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Example 1

[0059] A method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf, referring to Figure 1 , including the following steps:

[0060] Step 1: Build a CO gas detection and wind speed detection system in the goaf, refer to Figure 2 , including installing wind speed sensors 8 in the air inlet tunnel 3 and the return air tunnel 5 respectively, to monitor the wind speed V of the air inlet tunnel 3 in real time j And the wind speed V of the return air channel 5 h The air inlet tunnel 3 and the return air tunnel 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 bracket 7 is provided on the side of the working face 4 close to the goaf 2. CO concentration sensors 9 are respectively installed in the upper corner and in the middle of the return air tunnel 5 to monitor the CO gas concentration C in the upper corner in real time.s and CO gas concentration in the return air channel C h The wind speed sensor 8 and the CO concentration sensor 9 are both installed close to the top plate. The wind speed sensor 8 of the air inlet tunnel 3 is 18m away from the lower corner, the wind speed sensor 8 of the return air tunnel 5 is 18m away from the upper corner, and the CO concentration sensor 9 in the return air tunnel 5 is 32m away from the upper corner.

[0061] The wind speed sensor 8 used in this embodiment is an intrinsically safe wind speed sensor, and the CO concentration sensor 9 used is an intrinsically safe diffuse reflection CO laser sensor. The wind speed sensor 8 and the CO concentration sensor 9 are both connected to the local industrial computer through optical fiber, and the local industrial computer is connected to the surface host computer through a wireless network.

[0062] Step 2, obtain the CO gas concentration and wind speed of the working face 4 by reading the installed wind speed sensor 8 and CO concentration sensor 9 in real time, and ensure that the reading values ​​of the four sensors are at the same time by reading the timestamps of the two modal signals of the wind speed sensor and the CO concentration sensor.

[0063] Step 3, calculating the total circulation time T of the air entering the working face 4 into the goaf 2;

[0064] Step 4, calculate the total amount of CO gas dissipated in the return air lane 5 within a time period of T according to the monitored CO gas concentration and wind speed of the working face;

[0065] Step 5, calculating the total amount of residual coal in the oxidation and heating zone 1 in the goaf 2, and calculating the CO gas concentration generated by the residual coal in the goaf 2 per minute;

[0066] Step 6, determine whether the CO gas concentration generated by the residual coal in the goaf 2 exceeds the set alarm threshold a per minute. If it exceeds, there is a hidden danger of coal fire disaster, and the staff is immediately alarmed. Otherwise, continue to monitor the CO gas concentration and wind speed of the working face.

[0067] Example 2

[0068] A method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf, comprising the following steps:

[0069] Step 1: Build a CO gas detection and wind speed detection system in the goaf, including installing wind speed sensors 8 in the air inlet tunnel 3 and the return air tunnel 5 to monitor the wind speed V in the air inlet tunnel 3 in real time. j And the wind speed V of the return air channel 5 h , CO concentration sensors 9 are installed in the upper corner and the middle of the return air lane 5 respectively, for real-time monitoring of the CO gas concentration C in the upper corner s and CO gas concentration in the return air channel C hThe wind speed sensor 8 and the CO concentration sensor 9 are both installed close to the top plate. The wind speed sensor 8 of the air inlet tunnel 3 is 22m away from the lower corner, the wind speed sensor 8 of the return air tunnel 5 is 22m away from the upper corner, and the CO concentration sensor 9 in the return air tunnel 5 is 28m away from the upper corner.

[0070] The wind speed sensor 8 and the CO concentration sensor 9 are connected to the local industrial computer through optical fibers, and the local industrial computer is connected to the surface host computer through a wireless network.

[0071] Step 2, obtain the CO gas concentration and wind speed of the working face 4 by reading the installed wind speed sensor 8 and CO concentration sensor 9 in real time, and ensure that the reading values ​​of the four sensors are at the same time by reading the timestamps of the two modal signals of the wind speed sensor 8 and the CO concentration sensor 9.

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

[0073] Step 3.1: Measure the maximum distance M between the oxidation heating zone 1 on the air inlet side and the working surface 4 ja and the closest distance M ji , measure the maximum distance M between the return air side oxidation heating zone and the working surface 4 ha and the closest distance M hi ;

[0074] Step 3.2, calculate the migration distance of the airflow in the goaf, and get the migration distance of the airflow in the goaf as M. z ;

[0075] Step 3.3, the airflow migration distance in the goaf is divided into three stages, namely, the distance M from the air inlet side into the goaf but not into the oxidation and heating zone z1 , the wind speed is selected as the wind speed V of the air inlet lane j ; The distance M from the return air side into the goaf but not into the oxidation heating zone z3 , the wind speed is selected as the return air lane wind speed V h ; and the distance M into the oxidation warming zone z2 , the wind speed is selected as a constant of 0.2m / min;

[0076] Step 3.4, calculate the migration time of underground airflow into the goaf, that is, the total circulation time T of the working face air entering the goaf:

[0077]

[0078] Step 4: Calculate the total amount of CO gas dissipated in the return air lane within a time period of T based on the monitored CO gas concentration and wind speed of the working face. The specific process is as follows:

[0079] Step 4.1: Read the CO concentration value C detected by the CO concentration sensor at the upper corner in real time s ;

[0080] Step 4.2, determine C s Is it higher than the threshold of 24ppm? If it is higher than the threshold, there is a disaster risk and the staff will be alerted immediately. Otherwise, go to step 4.3;

[0081] Step 4.3, real-time reading of C h With V h , calculate the total amount Y of CO gas dissipated in the return air lane within the same time T s :

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

[0083] In the formula, S h Indicates the cross-sectional area of ​​the return air duct where the CO concentration sensor is installed.

[0084] Step 5, calculate the CO gas concentration generated by the coal in the goaf every minute. The specific process is as follows:

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

[0086]

[0087] Where m is the length of the working surface;

[0088] Step 5.2, calculate the total amount of coal left in the oxidation and heating zone in the goaf, the volume of coal left in the oxidation and heating zone V y for:

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

[0090] Where, H is the height of the overlying coal in the goaf;

[0091] Step 5.3, calculate the CO gas concentration C produced by the coal in the goaf every minute 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, there is a hidden danger of coal fire disaster, and the staff will be alarmed immediately. Otherwise, continue to monitor the CO gas concentration and wind speed of the working face.

[0094] Example 3

[0095] A method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf, comprising the following steps:

[0096] Step 1: Build a CO gas detection and wind speed detection system in the goaf, including installing wind speed sensors 8 in the air inlet tunnel 3 and the return air tunnel 5 to monitor the wind speed V in the air inlet tunnel 3 in real time. j and the wind speed V in the return air channel h , CO concentration sensors 9 are installed in the upper corner and the middle of the return air lane to monitor the CO gas concentration C in the upper corner in real time. s and CO gas concentration in the return air channel C h The wind speed sensor 8 and the CO concentration sensor 9 are both installed close to the top plate. The wind speed sensor 8 of the air inlet tunnel 3 is 20m away from the lower corner, the wind speed sensor 8 of the return air tunnel 5 is 20m away from the upper corner, and the CO concentration sensor 9 in the return air tunnel 5 is 30m away from the upper corner.

[0097] The wind speed sensor 8 and the CO concentration sensor 9 are connected to the local industrial computer through optical fibers, and the local industrial computer is connected to the surface host computer through a wireless network.

[0098] Step 2, obtain the CO gas concentration and wind speed of the working face 4 by reading the installed wind speed sensor 8 and CO concentration sensor 9 in real time, and ensure that the reading values ​​of the four sensors are at the same time by reading the timestamps of the two modal signals of the wind speed sensor 8 and the CO concentration sensor 9.

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

[0100] Step 3.1: Measure the maximum distance M between the oxidation heating zone on the air inlet side and the working surface ja and the closest distance M ji , measure the maximum distance M between the oxidation heating zone on the return air side and the working surface ha and the closest distance M hi ;

[0101] Step 3.2, calculate the migration distance of the airflow in the goaf, and get the migration distance of the airflow in the goaf as M. z ;

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

[0103] Step 3.2.1, set the spatial origin of the goaf for calculating the wind flow moving distance as the midpoint of the working face (0, 0), and obtain the corresponding coordinate positions of the upper corner and the lower corner 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 with the farthest relative movement of the wind flow as the center point of the farthest distance of the oxidation warming zone, and the coordinate position corresponds to ((M ja +M ha ) / 2,0);

[0105] Step 3.2.3, set the moving path of the wind flow in the goaf to be fan-shaped, that is, set the wind flow path 10 in the goaf to be fan-shaped (see Figure 2 ), calculate the center position of the wind flow path in the goaf. Since the upper corner, the lower corner and the point with the farthest relative movement of the wind flow form an isosceles triangle, the perpendicular bisector formula corresponding to the upper corner and the lower corner is y0=0, and the perpendicular bisector y a , and the perpendicular bisector y between the lower corner and the point with the longest relative movement b The expressions are:

[0106]

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

[0108] Step 3.2.4, calculate the angle β of the corner at the center of the wind flow moving path:

[0109]

[0110] Step 3.2.5, calculate the travel distance M of the airflow into the goaf z :

[0111]

[0112] Step 3.3, the airflow migration distance in the goaf is divided into three stages, namely, the distance M from the air inlet side into the goaf but not into the oxidation and heating zone z1 , the wind speed is selected as the wind speed V of the air inlet lane j , the distance M from the return air side into the goaf but not into the oxidation heating zone z3 , the wind speed is selected as the return air lane wind speed V h , and the distance M into the oxidation warming zone z2 , the wind speed is selected as a constant of 0.2m / 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) of the fan-shaped airflow path in the goaf and the closest oxidation warming zone:

[0115]

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

[0117] Step 3.3.2, calculate the distance between the two intersection points and the corner position, and get M z1 、M z2 and M z3 :

[0118]

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

[0120] Step 3.4, calculate the migration time of underground airflow into the goaf, that is, the total circulation time T of the working face air entering the goaf:

[0121]

[0122] Step 4: Calculate the total amount of CO gas dissipated in the return air lane within a time period of T based on the monitored CO gas concentration and wind speed of the working face. The specific process is as follows:

[0123] Step 4.1: Read the CO concentration value C detected by the CO concentration sensor at the upper corner in real time s ;

[0124] Step 4.2, determine C s Is it higher than the threshold of 24ppm? If it is higher than the threshold, there is a disaster risk and the staff will be alerted immediately. Otherwise, go to step 4.3;

[0125] Step 4.3, real-time reading of C h With V h , calculate the total amount Y of CO gas dissipated in the return air lane within the same time T s :

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

[0127] In the formula, S h Indicates the cross-sectional area of ​​the return air duct where the CO concentration sensor is installed.

[0128] Step 5, calculate the CO gas concentration generated by the coal in the goaf every minute. The specific process is as follows:

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

[0130]

[0131] Step 5.2, calculate the total amount of coal left in the oxidation and heating zone in the goaf, the volume of coal left in the oxidation and heating zone V y for:

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

[0133] Where, H is the height of the overlying coal in the goaf;

[0134] Step 5.3, calculate the CO gas concentration C generated by the coal in the goaf every minute 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, there is a hidden danger of coal fire disaster, and the staff will be alarmed immediately. Otherwise, continue to monitor the CO gas concentration and wind speed of the working face.

Claims

1. A method for evaluating the spontaneous combustion state of coal based on the amount of CO produced in goaf, characterized in that: The following steps are involved: Step 1: Build a CO gas detection and wind speed detection system in the goaf; Step 2, real-time monitoring of the CO gas concentration and wind speed at the working face (4); Step 3, calculating the total circulation time T of the air entering the working face (4) into the goaf (2); Step 4, calculating the total amount of CO gas dissipated in the return air lane (5) within a time period of T according to the CO gas concentration and wind speed of the monitored working face (4); Step 5, calculating the total amount of coal residue in the oxidation and heating zone (1) in the goaf (2), and calculating the CO gas concentration generated by the coal residue in the goaf (2) per minute; Step 6, determine whether the CO gas concentration generated by the residual coal in the goaf (2) exceeds the set alarm threshold a per minute. If it exceeds, there is a potential risk of coal fire disaster, and the staff is immediately alarmed. Otherwise, continue to monitor the CO gas concentration and wind speed of the working face (4).

2. The method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf according to claim 1 is characterized in that: In the step 1, a CO gas detection and wind speed detection system is built in the goaf, including installing wind speed sensors (8) in the air intake tunnel (3) and the return air tunnel (5) respectively, so as to monitor the wind speed V in the air intake tunnel (3) in real time. j and return air channel (5) wind speed V h A CO concentration sensor (9) is installed at the upper corner and the middle of the return air channel (5) to monitor the CO gas concentration C in the upper corner in real time. s and CO gas concentration in the return air channel (5) C h All wind speed sensors (8) and CO concentration sensors (9) are connected to the local industrial computer via optical fibers, and the local industrial computer is connected to the surface host computer via a wireless network.

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

4. The method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf according to claim 2 is characterized in that: The specific process of step 3 is as follows: Step 3.1, measure the maximum distance M between the oxidation heating zone (1) on the air inlet side and the working surface (4) ja and the closest distance M ji , measure the maximum distance M between the return air side oxidation heating zone (1) and the working surface (4) ha and the closest distance M hi ; Step 3.2, calculate the migration distance of the airflow into the goaf (2), and obtain the migration distance of the airflow into the goaf (2) as M z ; Step 3.3, the airflow migration distance in the goaf (2) is divided into three stages, namely, the distance M from the air inlet side into the goaf (2) but not into the oxidation and warming zone (1) z1 , the wind speed is selected as the wind speed V of the air inlet lane j , the distance M from the return air side into the goaf (2) but not into the oxidation heating zone (1) z3 , the wind speed is selected as the return air lane wind speed V h , and the distance M into the oxidation warming zone (1) z2 , the wind speed is selected as a constant of 0.2m / min; Step 3.4, calculate the migration time of the underground airflow into the goaf (2), that is, the total circulation time T of the working face air entering the goaf (2):

5. The method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf according to claim 4 is characterized in that: The specific process of step 3.2 is as follows: Step 3.2.1, set the spatial origin for calculating the wind flow movement distance of the goaf (2) as the midpoint (0, 0) of the working face (4), and obtain the corresponding coordinate positions of the upper corner and the lower corner in the space, which are (0, m / 2) and (0, -m / 2), respectively, where m is the length of the working face; Step 3.2.2, set the coordinate position of the point with the longest relative movement distance of the wind flow to ((M ja +M ha ) / 2,0); Step 3.2.3, set the movement path of the wind flow in the goaf (2) as a sector, the sector radius is R, the horizontal coordinate of the center of the sector is x0, and calculate the center position of the wind flow movement path. Since the upper corner, the lower corner and the point with the farthest relative movement of the wind flow form an isosceles triangle, the formula of the perpendicular bisector corresponding to the upper corner and the lower corner is y0=0, and the perpendicular bisector y0 between the upper corner and the point with the farthest relative movement of the wind flow is a , and the perpendicular bisector y between the lower corner and the point with the longest relative movement b The expressions are: In the formula, b is the intermediate variable, and the intersection of the three perpendicular bisectors is (m(b-1) / 4b, 0), which is the center position of the wind flow moving path; Step 3.2.4, calculate the angle β of the corner at the center of the wind flow moving path: Step 3.2.5, calculate the travel distance M of the airflow into the goaf z :

6. The method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf according to claim 5 is characterized in that: 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 (x1, y1) and (x2, y2) of the fan-shaped airflow path in the goaf and the closest oxidation warming zone: In the formula, b2 is the intermediate variable; Step 3.3.2, calculate the distance between the two intersection points and the corner position, and get M z1 、M z2 and M z3 : Wherein, A1 is the angle formed by the lower corner, (x0, 0) and (x1, y1), and A3 is the angle formed by the upper corner, (x0, 0) and (x2, y2).

7. The method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf according to claim 6 is characterized in that: The specific process of step 4 is as follows: Step 4.1, real-time reading of the CO concentration value C detected by the CO concentration sensor (9) at the upper corner s ; Step 4.2, determine C s Is it higher than the threshold of 24ppm? If it is higher than the threshold, there is a disaster risk and the staff will be alerted immediately. Otherwise, go to step 4.3; Step 4.3, real-time reading of C h With V h Calculate the total amount of CO gas Y released from the return air channel (5) within the same time T s : Y s =T*S h *V h *C h (8) In the formula, S h Indicates the cross-sectional area of ​​the return air channel where the CO concentration sensor (9) is installed.

8. The method for evaluating the spontaneous combustion state of coal based on the amount of CO generated in goaf according to claim 7 is characterized in that: The specific process of step 5 is as follows: Step 5.1, calculate the area S of the oxidation warming zone (1) y : Step 5.2, calculate the total amount of coal left in the oxidation and heating zone (1) in the goaf (2), the volume of coal left in the oxidation and heating zone (1) V y for: V y =S y H (10) Where H is the height of the overlying coal in the goaf (2); Step 5.3, calculate the CO gas concentration C generated by the coal in the goaf (2) per minute z :

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