Method for preventing spontaneous combustion of coal in goaf by using flue gas of power plant

Abstract

The invention relates to a method for preventing spontaneous combustion of coal in a goaf by using flue gas of a power plant, which comprises the following steps: (1) monitoring the concentrations of O2, CO, NOx and SO2 in the flue gas of the power plant and respectively recording the concentrations as P1, P2, P3 and P4, and when P1 is less than or equal to an inerting threshold value, taking the flue gas of the power plant as a pipeline to be subjected to gas taking; (2) according to the highest concentration of the underground harmful gas, calculating the allowable underground maximum flue gas injection amounts of CO, NOx and SO2, and respectively recording the allowable underground maximum flue gas injection amounts as M2, M3 and M4; a goaf harmful gas standard exceeding alarm threshold value K5 is determined, K5 is any numerical value from M-1000 to M-800, and M is the minimum value of M2, M3 and M4; (3) determining a target flue gas injection amount K6 of the goaf according to the allowable flue gas injection amount QY of the goaf, wherein K6 is any numerical value from QY + 300 to QY + 800; and (4) when the value of K5-K6 is more than 1000, the flue gas in the to-be-extracted gas pipeline is injected into the goaf, and the injection flow N is an arbitrary value between K6-800, K6 + 800]. According to the method, the flue gas of the power plant is further utilized, and the goaf is inerted.

Description

Technical Field

[0001] The present disclosure relates to the technical field of preventing and controlling spontaneous combustion disasters of coal in underground coal mines, and specifically, to a method for preventing spontaneous combustion of coal in gob areas by using flue gas from power plants. Background Art

[0002] Fire is one of the five major disasters in coal mines. Coal mine fires often cause huge economic losses and even casualties. Among them, gob fires are the main objects of prevention and control in coal mine fires because gob fires are hidden and difficult to detect. Once they occur, they not only last for a long time and are difficult to extinguish, but also the toxic and harmful gases such as carbon monoxide and carbon dioxide generated by the fire flow into each underground working area together with the high-temperature fire smoke, causing poisoning and asphyxiation of personnel.

[0003] The mainstream method for preventing and controlling gob fires is to inject inert gases. Currently, the commonly used inert gases are mainly nitrogen and carbon dioxide. However, the cost of the nitrogen production process is relatively high, the power consumption is large, the source of carbon dioxide is unstable, and the injection volume is strictly controlled. The above problems have been plaguing the popularization and application of inert gas fire prevention and extinguishing technologies. Finding alternative inert gases to nitrogen and carbon dioxide is a research hotspot for preventing and controlling gob fires. Building a power plant beside a coal mine is the product of integrated coal and electricity construction. The flue gas of the power plant is the product of coal combustion, and its main components are nitrogen, carbon dioxide, sulfur dioxide, and a small amount of oxygen. However, the composition of the flue gas of the power plant is complex, and whether it can inertize the gob area to prevent spontaneous combustion of coal has not been reported in the existing technology. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a method for preventing spontaneous combustion of coal in gob areas by using flue gas from power plants. This method further utilizes the flue gas from power plants and injects it into the gob area to prevent spontaneous combustion of coal. On the one hand, it replaces high-cost nitrogen, thereby saving costs. On the other hand, it can realize the resource treatment of flue gas from power plants and reduce carbon emissions.

[0005] To achieve the above purpose, the present disclosure provides a method for preventing spontaneous combustion of coal in gob areas by using flue gas from power plants. The method includes the following steps: (1) Monitor the concentrations of O2, CO, NO x , and SO2 in the flue gas from the power plant and record them as P1, P2, P3, and P4 respectively. When P1 ≤ the inerting threshold, use the flue gas from the power plant as the gas pipeline to be taken. The unit of P1 is %; the units of P2, P3, and P4 are mg / Nm 3 ; (2) Calculate the maximum allowable injection volume of each gas of CO, NO x , and SO2 into the underground according to the maximum allowable concentration of harmful gases in the underground, and record them as M2, M3, and M4 respectively, with the unit of m 3 / h; Determine the alarm threshold K5 for exceeding the standard of harmful gases in the gob area. The K5 is M -1000 to MAny value in -800, the M is the minimum value among M2, M3 and M4; The unit of K5 is m 3 / h; (3)According to the allowable flue gas injection volume Q of the goaf Y determine the target flue gas injection volume K6 of the goaf, K6 is Q Y +300 to Q Y +800; Any value in Q Y and the unit of K6 is m 3 / h; (4)When the value of K5 - K6 is above 1000, inject the flue gas in the gas extraction pipeline into the goaf, and the injection flow rate N is any value between [K6 - 800, K6 + 800], and the unit of N is m 3 / h.

[0006] Optionally, the inerting threshold is that the oxygen concentration is below 9%, preferably 3 - 9%.

[0007] Optionally, in step (2), the maximum allowable underground flue gas injection volumes of CO, NO x , SO2 and other gases are calculated according to formula (1), M Formula (1), , where The unit of is m M / h; 3 ; C 限 is the limit threshold of CO, NO x , SO2 and other gases in the "Coal Mine Safety Regulations", and the unit is mg / Nm 3 ; The x of CO, NO C max are P2, P3, P4 respectively, and the unit is mg / Nm 3 ; Q is the air volume of the working face, and the unit is m 3 / h.

[0008] Optionally, in step (3), the allowable flue gas injection volume of the goaf Q Y is calculated according to formula (2), Formula (2), where Q Y The unit of is m 3 / h; Q o is the internal leakage air volume in the oxidation zone of the goaf, and the unit is m 3 / min; C 1 is the average oxygen concentration in the gob oxidation zone, with the unit of %; C 2 is the inerting threshold; C N is the concentration of non-combustible gases in the flue gas, with the unit of %; K is an empirical coefficient, which is any value between 1.2 and 1.4.

[0009] Optionally, C N is 100 - P1.

[0010] Optionally, the method further includes: monitoring the flue gas components of multiple gas extraction channels of the power plant flue gas, and comparing the values of P1, P2, P3, and P4 in the flue gas of multiple gas extraction channels, if the P1 of the multiple gas extraction channels is greater than the inerting threshold, closing the multiple gas extraction channels; if the P1 of a certain gas extraction channel is ≤ the inerting threshold, taking this gas extraction channel as the pipeline to be gas-extracted; if the P1 of the multiple gas extraction channels is ≤ the inerting threshold, taking the gas extraction channel with the minimum P1 value among the multiple gas extraction channels as the pipeline to be gas-extracted.

[0011] Optionally, the method further includes: if the P1 of the multiple gas extraction channels is ≤ the inerting threshold, and the P1 values of any two gas extraction channels are the same, selecting the gas extraction channel with the minimum P2 value among the two gas extraction channels as the pipeline to be gas-extracted; if the P1 of the multiple gas extraction channels is ≤ the inerting threshold, and the P1 and P2 values of any two gas extraction channels are the same, selecting the gas extraction channel with the minimum P3 value among the two gas extraction channels as the pipeline to be gas-extracted; if the P1 of the multiple gas extraction channels is ≤ the inerting threshold, and the P1, P2, and P3 values of any two gas extraction channels are the same, selecting the gas extraction channel with the minimum P4 value among the two gas extraction channels as the pipeline to be gas-extracted.

[0012] Optionally, the method further includes: using a induced draft fan to draw the power plant flue gas in the pipeline to be gas-extracted to a flue gas treatment workshop for desulfurization treatment to obtain desulfurized flue gas; using an induced draft fan to inject the desulfurized flue gas into the gob.

[0013] Optionally, the injection flow rate N is any value between [K6 - 600, K6 + 600].

[0014] Optionally, regularly monitor N and K5. If N ≥ K5, close the pipeline to be gas-extracted and use liquid nitrogen for inerting.

[0015] Through the above technical solution, the present disclosure monitors and analyzes the flue gas of a power plant, selects the gas extraction channel with the oxygen volume concentration meeting the inerting threshold as the pipeline to be gas-extracted; calculates the over-standard alarm threshold of harmful gases in the goaf according to the maximum allowable concentration of harmful gases in the underground mine, determines the target flue gas injection volume in the goaf according to the allowable flue gas injection volume in the goaf, and injects the flue gas in the pipeline to be gas-extracted into the goaf within a specific difference range between the over-standard alarm threshold of harmful gases in the goaf and the target flue gas injection volume in the goaf to prevent coal spontaneous combustion. The method of the present disclosure, through the calculation of the flue gas of the power plant and the goaf, injects the flue gas of the power plant within a specific flow rate range into the goaf to prevent coal spontaneous combustion, making the flue gas of the power plant further reasonably utilized. On the one hand, it replaces high-cost nitrogen, thereby saving costs, and on the other hand, it can realize the resource treatment of the flue gas of the power plant and reduce carbon emissions. Other features and advantages of the present disclosure will be described in detail in the subsequent specific implementation section. Specific Implementation Manner

[0016] The following details the specific implementation manner of the present disclosure. It should be understood that the specific implementation manner described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0017] The present disclosure provides a method for preventing coal spontaneous combustion in a goaf with the flue gas of a power plant, and the method includes the following steps: (1) Monitor the concentrations of O2, CO, NO x , SO2 in the flue gas of the power plant and record them as P1, P2, P3, P4 respectively. When P1 ≤ the inerting threshold, use the flue gas of the power plant as the pipeline to be gas-extracted; the unit of P1 is %; the units of P2, P3, and P4 are mg / Nm 3 ; (2) Calculate the maximum allowable flue gas injection volumes of CO, NO x , SO2 in the underground mine respectively according to the maximum allowable concentration of harmful gases in the underground mine, and record them as M2, M3, M4 respectively, with the unit of m 3 / h; determine the over-standard alarm threshold K5 of harmful gases in the goaf, and the K5 is M - 1000 to M - 800, and any value within this range, where M is the minimum value of M2, M3, and M4; the unit of K5 is m 3 / h; (3) Determine the target flue gas injection volume K6 in the goaf according to the allowable flue gas injection volume Q Y in the goaf, and K6 is any value from Q Y + 300 to Q Y + 800; the units of Q Y and K6 are m 3 / h; When the value of K5 - K6 is 1000 or more, inject the flue gas in the gas extraction pipeline to be taken into the gob area, and the injection flow rate N is any value between [K6 - 800, K6 + 800], and the unit of N is m 3 / h.

[0018] The present disclosure monitors and analyzes the flue gas of the power plant, selects the gas extraction channel with the oxygen volume concentration meeting the inerting threshold as the gas extraction pipeline to be taken; calculates the over-standard alarm threshold of the harmful gas in the gob area according to the maximum allowable concentration of the harmful gas in the underground mine, determines the target flue gas injection volume in the gob area according to the allowable flue gas injection volume in the gob area, and injects the flue gas in the gas extraction pipeline to be taken into the gob area within a specific difference range between the over-standard alarm threshold of the harmful gas in the gob area and the target flue gas injection volume in the gob area to prevent coal spontaneous combustion. The method of the present disclosure calculates the flue gas of the power plant and the gob area, so that the flue gas of the power plant within a specific flow rate range is injected into the gob area to prevent coal spontaneous combustion, so that the flue gas of the power plant is further reasonably utilized. On the one hand, it replaces high-cost nitrogen to save costs, and on the other hand, it can realize the resource treatment of the flue gas of the power plant and reduce carbon emissions.

[0019] In the present disclosure, the injection flow rate refers to the flue gas injection flow rate required for the gob area of a coal mining face. Preventing coal spontaneous combustion in the present disclosure means inerting the gob area with the flue gas of the power plant so that the temperature in the gob area is below 30°C.

[0020] According to an embodiment of the present disclosure, the inerting threshold is that the oxygen concentration is below 9%, preferably 3 - 9%. The above embodiment is beneficial to the normal operation of the gob area and is beneficial to ensuring the operation safety of the workers in the gob area.

[0021] According to an embodiment of the present disclosure, in step (2), CO, NO x The maximum allowable underground flue gas injection volume of each gas such as SO2 is M Calculated according to formula (1), , formula (1), wherein, M The unit of is m 3 / h; C 限 is the limit threshold of each gas such as CO, NO x SO2 in the "Coal Mine Safety Regulations", and the unit is mg / Nm 3 ; CO, SO2, NO x The C max of each gas are P2, P3, and P4 respectively, and the unit is mg / Nm 3 ; Q is the air volume of the working face, and the unit is m 3 / h. In the present disclosure, the maximum allowable underground flue gas injection volume for each gas is determined based on the harmful gas components of the flue gas under the condition of not considering the influence of the original gas emission from the working face and assuming that all flue gas is discharged through the return air current. The above embodiments are beneficial to the normal operation of the gob area and ensure the operation safety of the workers in the gob area.

[0022] According to an embodiment of the present disclosure, in step (3), the allowable flue gas injection volume of the gob area Q Y is calculated according to formula (2), , formula (2), wherein, Q Y The unit of is m 3 / h; Q o is the air leakage volume in the oxidation zone of the gob area, and the unit is m 3 / min; C 1 is the average oxygen concentration in the oxidation zone of the gob area, and the unit is %; C 2 is the inerting threshold; C N is the concentration of non-combustible gas in the flue gas, and the unit is %; K is an empirical coefficient, and any value between 1.2 and 1.4. The above embodiments are beneficial to achieving a better inerting effect in the gob area, avoiding the situation of excessive flue gas injection volume and causing flue gas spillage.

[0023] According to an embodiment of the present disclosure, C N is 100 - P1.

[0024] According to an embodiment of the present disclosure, the method further includes: Monitoring the flue gas components of multiple gas extraction channels of the power plant flue gas, comparing the values of P1, P2, P3, and P4 in the flue gas of multiple gas extraction channels. If the P1 of the multiple gas extraction channels is greater than the inerting threshold, then close the multiple gas extraction channels; if the P1 of a certain gas extraction channel is ≤ the inerting threshold, then use this gas extraction channel as the gas extraction pipeline to be used; if the P1 of the multiple gas extraction channels is ≤ the inerting threshold, then use the gas extraction channel with the minimum P1 value among the multiple gas extraction channels as the gas extraction pipeline to be used. In a further embodiment, after closing the gas extraction channel of the power plant flue gas, liquid nitrogen is used for inerting. Liquid nitrogen inerting is a conventional operation in the art and will not be specifically described herein. The above embodiments are beneficial to achieving a better inerting effect in the gob area, further resource utilization of the power plant flue gas, which is beneficial to environmental protection on the one hand and can reduce the operation cost of enterprises on the other hand.

[0025] According to an embodiment of the present disclosure, the method further includes: If the P1 of the multiple gas extraction channels is ≤ the inerting threshold, and when the P1 of any two gas extraction channels is the same, select the gas extraction channel with the minimum P2 among the two gas extraction channels as the pipeline to be gas extracted; if the P1 of the multiple gas extraction channels is ≤ the inerting threshold, and the P1 and P2 values of any two gas extraction channels are the same, then select the gas extraction channel with the minimum P3 among the two gas extraction channels as the pipeline to be gas extracted; if the P1 of the multiple gas extraction channels is ≤ the inerting threshold, and the P1, P2 and P3 values of any two gas extraction channels are the same, then select the gas extraction channel with the minimum P4 among the two gas extraction channels as the pipeline to be gas extracted. The above embodiments are conducive to achieving a better inerting effect in the goaf, further resource utilization of the power plant flue gas, which is beneficial to environmental protection on the one hand and can reduce the operation cost of enterprises at the same time.

[0026] According to an embodiment of the present disclosure, the method further includes: using a induced draft fan to lead the power plant flue gas in the pipeline to be gas extracted to a flue gas treatment workshop for desulfurization treatment to obtain desulfurized flue gas; using an induced draft fan to inject the desulfurized flue gas into the goaf. In a further embodiment, after the pipeline to be gas extracted is selected, the gas extraction valve is opened in two ways: local opening or remote opening. For local opening, the PLC controller is used to open the gas extraction valve, and for remote opening, the configuration software, monitoring substation and PLC controller are used to open the gas extraction valve; when using an induced draft fan to inject the desulfurized flue gas into the goaf, the induced draft fan adopts frequency conversion control, and the injection flow rate is constantly pressure-regulated according to the actual allowable flue gas injection volume in the underground goaf. The frequency conversion control is a conventional operation in the art, and the injection flow rate N is any value between [K6 - 800, K6 + 800]. The above embodiments are conducive to achieving a better inerting effect in the goaf, further resource utilization of the power plant flue gas, which is beneficial to environmental protection on the one hand and can reduce the operation cost of enterprises at the same time.

[0027] According to an embodiment of the present disclosure, the injection flow rate N is any value between [K6 - 600, K6 + 600]. The above embodiments are conducive to achieving a better inerting effect in the goaf, further resource utilization of the power plant flue gas, which is beneficial to environmental protection on the one hand and can reduce the operation cost of enterprises at the same time.

[0028] According to an embodiment of the present disclosure, N and K5 are monitored regularly. If N ≥ K5, the pipeline to be gas extracted is closed, and liquid nitrogen is used for inerting. The above embodiments are conducive to the normal operation of the goaf and ensure the operation safety of the goaf workers.

[0029] The following further describes the present disclosure in detail with reference to embodiments, but does not limit the present disclosure in any way.

[0030] Example 1 of the present disclosure takes the Dananhu No. 1 Mine as the object of inerting. The basic situation is that the mine is located about 84 km south of Hami City, Xinjiang Uygur Autonomous Region, in the middle of the Dananhu Coalfield; the mine field development design adopts the comprehensive development method of the main inclined shaft and auxiliary and air vertical shafts; the 1305 working face mainly mines the No. 3 coal seam, with an average coal seam thickness of 9 m. The coal seam belongs to an easily self-igniting coal seam, and the coal spontaneous combustion period is 62 days; the top coal caving mining method is adopted, and the coal recovery rate is 60% - 80%; the roof is sandstone, and the uniaxial compressive strength is 55 - 65 MPa; the KJ770N safety monitoring system is installed in the 1305 working face, and methane, carbon monoxide, oxygen, temperature, wind speed, dust, and smoke sensors are respectively set. The extracted power plant flue gas is the flue gas of the Hami Dananhu Power Plant, and oxygen sensors, CO sensors, NO x sensors and SO2 sensors are set at the flue gas extraction port.

[0031] Example 1 (1) Mark multiple gas extraction channels at the power plant flue gas discharge port. According to the data of the power plant flue gas discharge monitoring system, monitor the concentrations of O2, CO, NO x , SO2 in the flue gas and record them as P1, P2, P3, P4 respectively. The monitoring results of the K1 gas extraction channel are shown in Table 1. P1 is 6%, and P1 is less than the inerting threshold of 9%. The K1 gas extraction channel of the power plant flue gas can be used as the gas pipeline to be extracted; P2 is 300 mg / Nm 3 , P3 is 50 mg / Nm 3 , P4 is 35 mg / Nm 3 ; Table 1

[0032] (2) The maximum allowable concentration of underground harmful gases is shown in Table 2. Calculate the maximum allowable flue gas injection volume of CO, NO x , SO2 underground respectively, and record them as M2, M3, M4, with the unit of m 3 / h; The calculation formula is as follows,

[0033] Q is the working face air volume, m 3 / h; C 限 is the maximum limit of pollutants in the regulations, mg / Nm 3 ; C max is the highest value of pollutants in the flue gas, mg / Nm 3 , Q is 79380 m 3 / h, and M2 is calculated to be 8820 m3 / h, M3 is 8820 m 3 / h, M4 is 59535 m 3 / h; Determine the over-standard alarm threshold K5 of harmful gases in the goaf according to the minimum value of 8820 m 3 / h, K5 = 8000 m 3 / h; Table 2 Maximum allowable concentrations of harmful gases in the Coal Mine Safety Regulations

[0034] Table 3

[0035] (3) Calculate the allowable flue gas injection volume of the goaf according to the following formula Q Y , , Q0 is the air leakage volume in the oxidation zone of the goaf, measured as 25 m 3 / min; C1 is the average oxygen concentration in the oxidation zone of the goaf, which is 15%; C2 is the inerting threshold of the goaf, 9%; C N is the concentration of non-combustible gases in the injected flue gas, which is 94%; K is the spare coefficient, taking 1.3, and the calculated result is Q Y = 3900 m 3 / h; Determine the target flue gas injection volume K6 of the goaf, K6 is 4500 m 3 / h; (4) The value of K5 - K6 is 3500, and inject the flue gas in the gas extraction pipeline into the goaf; the flue gas injection flow rate N of a mining face is 4500 m 3 / h.

[0036] After selecting the gas extraction channel, open the gas extraction valve, use the induced draft fan to first draw the power plant flue gas in the gas extraction pipeline to the flue gas treatment workshop for desulfurization treatment to obtain the desulfurized flue gas; use the induced draft fan to inject the desulfurized flue gas into the goaf, and monitor the injection flow rate. According to the actual allowable flue gas injection volume of the underground goaf, regulate the injection flow rate by constant pressure and variable frequency. The injection flow rate N is any value between [K6 - 500, K6 + 500], so that the temperature in the goaf is below 30°C. Monitor the injection flow rate in real time. If N exceeds K5, close the gas extraction channel and use the liquid nitrogen channel for inerting.

[0037] According to the method of the present disclosure, within the injection flow rate range of the power plant flue gas of the present disclosure, the power plant flue gas can be used to achieve the purpose of inerting the goaf. Below the injection flow rate range of the present disclosure, the power plant flue gas and liquid nitrogen need to be used together for inerting. Above the injection flow rate range of the present disclosure, it is easy to cause the over-standard of harmful gases and pose a safety risk.

[0038] The preferred embodiments of the present disclosure have been described in detail above. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0039] In addition, it should be noted that, in the case of no conflict, the various specific technical features described in the above specific embodiments can be combined in any appropriate manner. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination manners.

[0040] Furthermore, any combination can be made among various different embodiments of the present disclosure, as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. A method for preventing spontaneous combustion of coal in goaf using flue gas from a power plant, characterized in that: The method comprises the following steps: (1) Monitoring O2, CO, and NO in power plant flue gas x The concentrations of SO2 are recorded as P1, P2, P3, and P4 respectively. When P1 ≤ the inerting threshold, the flue gas from the power plant is used as the pipeline to be taken out. The unit of P1 is %; the units of P2, P3, and P4 are mg / Nm 3 ; (2) Calculate CO and NO based on the maximum concentration of harmful gases underground x The maximum underground flue gas injection volume allowed for each gas, SO2, is recorded as M2, M3, and M4, respectively, in m 3 / h; determine the alarm threshold K5 of harmful gas exceeding the standard in the goaf, where K5 is M -1000 to M Any value between -800, M The minimum value among M2, M3 and M4; the unit of K5 is m 3 / h; (3) Based on the allowable flue gas injection volume of the goaf Q Y Determine the target flue gas injection rate K6 of the goaf, K6 is Q Y +300 to Q Y Any value in +800; Q Y The unit of K6 is m 3 / h; (4) When the value of K5-K6 is greater than 1000, the flue gas in the pipeline to be extracted is injected into the goaf. The injection flow rate N is any value between [K6-800, K6+800], and the unit of N is m 3 / h.

2. The method according to claim 1, wherein: The inertization threshold is an oxygen concentration of 9% or less, preferably 3-9%.

3. The method according to claim 1, wherein: In step (2), CO, NO x , SO2 Maximum allowable underground flue gas injection volume for each gas M According to formula (1), , formula (1), in, M The unit is m 3 / h ; C 限 For the "Coal Mine Safety Regulations" on CO and NO x , SO2 limit threshold of each gas, unit is mg / Nm 3 ;CO, NO x 、SO2 C max They are P2, P3, and P4 respectively, and the unit is mg / Nm 3 ; Q is the air volume of the working surface, in m 3 / h.

4. The method according to claim 1, wherein: In step (3), the allowable flue gas injection volume in the goaf is Q Y According to formula (2), , formula (2), in, Q Y The unit is m 3 / h; Q o is the air leakage in the oxidation zone of the goaf, in m 3 / min; C 1 is the average oxygen concentration in the oxidation zone of the goaf, unit is %; C 2 is the inertization threshold; C N is the concentration of non-combustible gas in flue gas, unit is %; K is an empirical coefficient, which can be any value between 1.2 and 1.

4.

5. The method according to claim 4, wherein: C N It is 100-P1.

6. The method according to claim 1, wherein: The method further comprises: Monitor the flue gas composition of multiple gas intake channels of the power plant, and compare the values ​​of P1, P2, P3, and P4 in the flue gas of multiple gas intake channels. If P1 of the plurality of gas intake channels are all greater than the inertization threshold, the plurality of gas intake channels are closed; If P1 of a certain air intake channel is less than or equal to the inertization threshold, then the air intake channel is used as the pipeline to be taken out of the air; If P1 of the plurality of air intake channels are all ≤ the inertization threshold, the air intake channel with the minimum P1 value among the plurality of air intake channels is used as the pipeline to be taken out of air.

7. The method according to claim 6, wherein: The method further comprises: If P1 of the plurality of gas intake channels are all ≤ the inertization threshold, and P1 of any two gas intake channels are the same, the gas intake channel with the minimum P2 value among the two gas intake channels is selected as the gas intake pipeline to be taken out; If P1 of the plurality of gas intake channels is less than or equal to the inertization threshold, and the P1 and P2 values ​​of any two gas intake channels are the same, then the gas intake channel with the minimum P3 value among the two gas intake channels is selected as the gas intake pipeline to be taken out; If P1 of the plurality of air intake channels is less than or equal to the inertization threshold, and the P1, P2 and P3 values ​​of any two air intake channels are the same, the air intake channel with the minimum P4 value among the two air intake channels is selected as the air intake pipeline to be taken out.

8. The method according to claim 1, wherein: The method further comprises: using an induced draft fan to lead the power plant flue gas in the gas extraction pipeline to a flue gas treatment workshop for desulfurization treatment to obtain desulfurized flue gas; and using the induced draft fan to inject the desulfurized flue gas into the goaf.

9. The method according to claim 8, wherein: The injection flow rate N is any value between [K6-600, K6+600].

10. The method according to claim 1 or 9, wherein: Monitor N and K5 regularly. If N≥K5, close the gas pipeline to be taken out and use liquid nitrogen for inerting.

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