Rapid calculation method for inerting range of liquid CO2 in goaf

Abstract

The invention discloses a rapid calculation method for a goaf liquid CO2 inerting range. The rapid calculation method comprises the following steps: S1, constructing a liquid CO2 goaf cooling system; s2, calculating a goaf air flow field by taking the middle of the working face as an original point; s3, calculating the average temperature of the oxidation heating zone of the goaf; s4, calculating the gas diffusion range of the pressure-injected CO2 in the goaf; and S5, pressure injection of the CO2 cooling system is stopped, and the influence range of single-time pressure injection of liquid CO2 on the goaf is obtained. According to the rapid calculation method for the inerting range of the liquid CO2 in the goaf, the problem that the fire preventing and extinguishing effect is poor due to the fact that prediction of the diffusion range of the liquid CO2 in the goaf is not accurate is solved.

Description

Technical Field

[0001] This invention belongs to the field of fire prevention and extinguishing technology in goaf areas, specifically relating to a rapid calculation method for the inerting range of liquid CO2 in goaf areas. Background Technology

[0002] The current problem of oxidation and temperature rise in coal mine goaf areas poses a significant threat to mine safety, as high temperatures can easily trigger spontaneous combustion of coal. Traditional prediction methods mainly rely on physical models and empirical formulas, but their accuracy and reliability are significantly insufficient under complex geological and airflow conditions. Liquid CO2 inerting technology has become a common method in coal mine fire prevention and extinguishing due to its advantages such as rapid cooling and wide inerting range. However, current technologies lack precise calculation models for the airflow field distribution and gas diffusion range in goaf areas, making it difficult to dynamically predict the inerting effect. Therefore, developing a method that can quickly and accurately calculate the liquid CO2 inerting range in goaf areas is of urgent practical significance for improving the accuracy of coal mine spontaneous combustion disaster prediction and emergency response efficiency. The main problem with current technologies is the inability to accurately simulate the airflow field and temperature distribution within the goaf area, making it difficult to determine the CO2 inerting range. The movement of the airflow field in the goaf area determines the CO2 diffusion effect. Early warning and control systems can only control the timing and amount of inert gas injection, without considering the diffusion after injection. After inert gas is injected, it diffuses with the airflow field. Predicting the airflow field in the goaf using empirical formulas and traditional single models is rather mechanical and inaccurate, directly affecting the fire prevention and extinguishing effect of inert gas on the oxidation zone. First, models based on fixed parameters cannot quickly respond to dynamic changes in the goaf environment, failing to meet the timeliness requirements for fire prevention and extinguishing. Second, the lack of coupled modeling of the airflow field, temperature field, and CO2 diffusion process makes it impossible to accurately assess the inerting effect under different injection conditions, easily leading to wasted CO2 resources or inadequate fire prevention and extinguishing. To address these issues, we propose a rapid calculation method that dynamically couples the airflow, temperature, and CO2 diffusion characteristics of the goaf to achieve accurate prediction of the liquid CO2 inerting range, thereby improving the efficiency and safety of coal mine fire prevention and extinguishing. Summary of the Invention

[0003] The purpose of this invention is to provide a rapid calculation method for the inerting range of liquid CO2 in goaf areas, which solves the problem of inaccurate prediction of the diffusion range of liquid CO2 in goaf areas, resulting in poor fire prevention and extinguishing effects.

[0004] The technical solution adopted in this invention is a rapid calculation method for the inerting range of liquid CO2 in goaf areas, comprising the following steps:

[0005] S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; S3. Calculate the average temperature of the oxidation heating zone in the goaf; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

[0006] The invention is further characterized by: The liquid CO2 goaf cooling system includes a liquid CO2 goaf injection pipeline, a temperature sensor, and a wind speed sensor. The outlet of the liquid CO2 goaf injection pipeline is located on the side of the goaf oxidation and heating zone near the coal pillar. The wind speed sensor is located in the intake airway and the return airway. The temperature sensor is located at the upper corner, the lower corner, and the liquid CO2 injection port. Intrinsically safe wind speed sensors are selected and installed on both sides of the coal pillar in the intake and return airways. The sensors are positioned 2m above the vertical base and 50m from the upper and lower corners. These sensors are used to measure the wind speed in the intake and return airways. V 1. V 2. The wind speed sensor is connected to the on-site centralized processor via a wire. The wind speed sensor transmits the signal to the on-site centralized processor for calculation and data storage via the wire.

[0007] The temperature sensor is an intrinsically safe type. It is suspended from the top plate at the upper and lower corners, and is used to detect real-time temperature data at the upper and lower corners and the location of the liquid CO2 injection port. T j , T h , T g The temperature sensor is connected to the on-site centralized processor via a wire, and the temperature sensor transmits the signal to the on-site centralized processor for calculation and data storage.

[0008] S2 specifically refers to: S2.1 Obtain information on the heat dissipation zone and oxidation heating zone within the goaf; Define the furthest distance on one side of the heat dissipation duct intake as H ji That is, the closest distance on the air inlet side of the oxidation heating zone is H ji The furthest distance on one side of the heat dissipation belt return airway is H hi That is, the closest distance on the air inlet side of the oxidation heating zone is H hi The furthest distance on the air inlet side of the oxidation heating zone is... H jm The furthest distance on the return air side of the oxidation heating zone is Hhm ; S2.2 Calculate the airflow path within the goaf, taking the center of the working face as the origin; Due to the influence of airflow in the goaf, the goaf is divided into a heat dissipation zone and an oxidation heating zone. The lower corner is the air inlet and the upper corner is the air outlet. The airflow path is approximated as an ellipse. The working face support is used as the symmetrical dividing line of the ellipse to calculate the airflow path in the goaf. S2.3 Obtain wind speed information at the intake and return airways; S2.4. Based on the airflow path and wind speed information, the transport time of the airflow into the goaf is calculated using formula (1). (1); In the formula, t This refers to the transport time of underground airflow into the goaf. M s1 This is the distance from when the airflow first enters the heat dissipation zone before entering the oxidation and heating zone. M y This represents the transport distance of the airflow in the oxidation heating zone. M s2 This refers to the transport distance of the airflow after it leaves the oxidation heating zone and re-enters the heat dissipation zone; S2.5. Based on the airflow path, wind speed information and transport time, the airflow field of the goaf is calculated using formula (2); (2); In the formula, a Let be a dimensionless constant for the airflow path, based on the calculation of the elliptical airflow path in... x The maximum distance setting for the axis.

[0009] S3 specifically refers to: S3.1 Obtain temperature information at the upper and lower corner positions; S3.2. Based on wind speed and temperature information, the total heat of air temperature rise caused by residual coal in the goaf is calculated using formula (3). (3); In the formula, T c The total heat dissipation is the heat generated in the oxidation and heating zone of the goaf, expressed in W. S j The average cross-sectional size of the intake airway is given in meters. 2 ; S h The average cross-sectional size of the return airway is given in meters. 2 ; 1.2 represents the average density of the gas in the tunnel, kg / m³ 3 1005 is the specific heat capacity of air, J / (kg). K); S3.3 Calculate the total heat dissipation of the oxidation and heating zone of the residual coal in the goaf; The total heat dissipation of the residual coal oxidation and heating zone in the goaf consists of the heat dissipation zone of the goaf and the residual coal in the oxidation and heating zone. Due to the influence of wind speed, the residual coal in the heat dissipation zone is unlikely to accumulate heat and undergo oxidation reaction, which is mainly concentrated in the oxidation and heating zone. Therefore, the total heat caused by the residual coal to raise the temperature of the air is equal to the total heat dissipation of the residual coal oxidation and heating zone. S3.4 Calculate the temperature of the residual coal in the oxidation heating zone of the goaf according to formulas (4), (5), and (6); (4); (5); (6); In the formula, S yy The estimated surface area of ​​residual coal in the oxidation and heating zone of the goaf, in m. 2 ; α The convective heat transfer coefficient is W / (m²). 2 K), is generally obtained through experimental means or by substituting the empirical constant 14.7; T ym The temperature of the residual coal in the oxidation and heating zone of the goaf is K.

[0010] S4 specifically refers to: S4.1 Obtain liquid CO2 pipeline injection information; the injection information includes pipeline pressure, pipeline diameter, and injection duration; S4.2 Input the goaf airflow field obtained in S2.5, the temperature of residual coal in the goaf oxidation heating zone obtained in S3.4, and the liquid CO2 injection information obtained in S4.1 into the CO2 injection range coupling model; S4.3 Obtain the range of CO2 influence under different injection times.

[0011] S2.2 Airflow path within the goaf: with the middle of the support as the origin (0,0), the length of the working face is... H The coordinates of the lower corner are (0, H / 2), the coordinates of the upper corner are (0, - H / 2).

[0012] In S2.4, the transport time consists of the transport time of the airflow in the two heat dissipation zones within the goaf and the transport time of the oxidation heating zone. The gas transport velocity in the heat dissipation zone is taken as the gas transport velocity in the intake or return airway closer to one side, and the gas transport velocity in the oxidation heat dissipation zone is fixed at 0.2 m / min.

[0013] The CO2 injection range coupling model in S4.2 is as follows: S4.2.1 Using CFD simulation software, a liquid CO2 injection model for the goaf is constructed. The injection model is used to simulate the CO2 gas diffusion range in the goaf under different injection conditions. S4.2.2 Using CO2 concentrations of 1%, 5%, and 20% in the goaf as thresholds, the furthest distance of CO2 gas diffusion to the three key thresholds under different initial conditions is calculated using a pressure injection model. x 20 , y 20 ), ( x 5, y 5), ( x 1, y 1) Obtain experimental datasets of the farthest diffusion distance under different injection conditions; S4.2.3 Using the Gaussian smoke model as the baseline model, the diffusion coefficient in the original model was optimized through experimental datasets, thus optimizing the Gaussian smoke model; S4.2.4 Obtain the optimized injection range coupling model.

[0014] The specific optimization of the diffusion coefficient in the original model in S4.2.3 is as follows: the diffusion coefficient is calculated according to formulas (7) to (11); (7); (8); (9); (10); (11); in, C ( x , y ) is in spatial location ( x , y CO2 gas concentration at ( ), kg / m³ 3 ; Q Injection rate, kg / s; u The ambient wind speed is in m / s. σ x , σ y , σ z These are the diffusion coefficients in the horizontal and vertical directions, the horizontal axis direction, and the vertical direction, respectively; that is, the diffusion coefficients in the downwind, crosswind, and vertical wind directions, in meters. r Let be the radius of the injection pipe, in meters (m). P The pressure inside the pipe is in Pa; M This represents the relative molecular mass of the injected gas; R This is the constant amount of injection gas; λThe adiabatic coefficient of the gas; y’ The tangent of the airflow in the goaf area is different from that in the directly administered area; θ The angle of the airflow relative to the origin; K The optimal diffusion coefficient; x 0, y 0) indicates the location of the CO2 injection port. C’ (20%) C’ (5%) C’ (1%) are the inverse functions of formula (1) for gas at CO2 concentrations of 20%, 5%, and 1%, respectively, i.e., the corresponding coordinate positions.

[0015] The beneficial effects of this invention are: This invention provides a rapid calculation method for the inerting range of liquid CO2 in goaf areas. By approximating the airflow path in the goaf as an ellipse and combining real-time wind speed and temperature data collected by sensors, a dynamic airflow field and a three-dimensional temperature distribution field are constructed. This achieves precise coupled modeling of the airflow field, temperature field, and CO2 diffusion process, effectively solving the problems of traditional methods in accurately simulating complex goaf environments and insufficient prediction accuracy. Furthermore, by correcting the diffusion direction of the Gaussian plume model through coordinate transformation and optimizing the diffusion coefficient piecewise according to the CO2 concentration threshold, it breaks through the traditional model's "constant airflow" limitation. The limitations of the assumptions were overcome, significantly improving the pertinence and reliability of inerting range calculations under different injection conditions; relying on the underground ring network to realize real-time transmission of sensor data and dynamic model correction, it can quickly respond to the dynamic changes in the goaf environment and meet the timeliness requirements of fire prevention and extinguishing work; by accurately determining the actual influence range of liquid CO2, it provides a reliable basis for coal mines to formulate scientific and reasonable injection plans, which not only avoids the waste of CO2 resources, but also ensures sufficient inerting coverage of the oxidation and heating zone of the goaf, effectively reducing the risk of coal spontaneous combustion and greatly improving the efficiency and safety of coal mine fire prevention and extinguishing work. Attached Figure Description

[0016] Figure 1 This is a flowchart of the rapid calculation method for the inerting range of liquid CO2 in goaf areas according to the present invention; Figure 2 This is a schematic diagram of the liquid CO2 goaf injection pipeline layout in Embodiment 6 of the present invention; Figure 3 This is a schematic diagram of the simulated three-band design in Embodiment 6 of the present invention; Figure 4 This is a schematic diagram of the airflow path in Embodiment 6 of the present invention; Figure 5 This is a schematic diagram of the average temperature of the oxidation and heating zone in the goaf area in Embodiment 6 of the present invention.

[0017] In the diagram, 4 is the liquid CO2 injection pipeline in the goaf, 6 is the intake airway, 8 is the return airway, 10 is the temperature sensor, and 11 is the wind speed sensor. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 The rapid calculation method for the liquid CO2 inerting range in goaf areas proposed in this embodiment is as follows: Figure 1 As shown, it includes the following steps: S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; S3. Calculate the average temperature of the oxidation heating zone in the goaf; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

[0020] Example 2 The rapid calculation method for the inerting range of liquid CO2 in a goaf proposed in this embodiment includes a liquid CO2 goaf injection pipe 4, a temperature sensor 10, and a wind speed sensor 11. The outlet of the liquid CO2 goaf injection pipe 4 is located on the side of the goaf oxidation and heating zone near the coal pillar. The wind speed sensor 11 is located in the intake airway and the return airway. The temperature sensor 10 is located at the upper corner, lower corner, and liquid CO2 injection port. The wind speed sensor 11 is an intrinsically safe wind speed sensor, installed in the intake airway 6 and the return airway 8 near the coal pillar on both sides. The wind speed sensor 11 is installed 2m high vertically to the bottom plate and 50m away from the upper and lower corners. The wind speed sensor 11 is used to measure the wind speed in the intake airway 6 and the return airway 8. V 1. V 2. The wind speed sensor 11 is connected to the on-site centralized processor via a wire. The wind speed sensor 11 transmits signals to the on-site centralized processor for calculation and data storage via the wire; for example... Figure 1 As shown, it includes the following steps: S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; S3. Calculate the average temperature of the oxidation heating zone in the goaf; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

[0021] Example 3 The rapid calculation method for the inerting range of liquid CO2 in a goaf proposed in this embodiment includes a liquid CO2 goaf injection pipe 4, a temperature sensor 10, and a wind speed sensor 11. The outlet of the liquid CO2 goaf injection pipe 4 is located on the side of the goaf oxidation and heating zone near the coal pillar. The wind speed sensor 11 is located in the intake airway and the return airway. The temperature sensor 10 is located at the upper corner, lower corner, and liquid CO2 injection port. The wind speed sensor 11 is an intrinsically safe wind speed sensor, installed in the intake airway 6 and the return airway 8 near the coal pillar on both sides. The wind speed sensor 11 is installed 2m high vertically to the bottom plate and 50m away from the upper and lower corners. The wind speed sensor 11 is used to measure the wind speed in the intake airway 6 and the return airway 8. V 1. V 2. The wind speed sensor 11 is connected to the on-site centralized processor via a wire. The wind speed sensor 11 transmits signals to the on-site centralized processor for calculation and data storage. The temperature sensor 10 is an intrinsically safe temperature sensor. The temperature sensor 10 is suspended from the top plate at the upper and lower corners. The temperature sensor 10 is used to detect real-time temperature data at the upper and lower corners and at the liquid CO2 injection port. T j , T h , T g Temperature sensor 10 is connected to the wellhead central processor via a wire, and the temperature sensor 10 transmits signals to the wellhead central processor for calculation and data storage; such as Figure 1 As shown, it includes the following steps: S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; S3. Calculate the average temperature of the oxidation heating zone in the goaf; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

[0022] Example 4 The rapid calculation method for the inerting range of liquid CO2 in a goaf proposed in this embodiment includes a liquid CO2 goaf injection pipe 4, a temperature sensor 10, and a wind speed sensor 11. The outlet of the liquid CO2 goaf injection pipe 4 is located on the side of the goaf oxidation and heating zone near the coal pillar. The wind speed sensor 11 is located in the intake airway and the return airway. The temperature sensor 10 is located at the upper corner, lower corner, and liquid CO2 injection port. The wind speed sensor 11 is an intrinsically safe wind speed sensor, installed in the intake airway 6 and the return airway 8 near the coal pillar on both sides. The wind speed sensor 11 is installed 2m high vertically to the bottom plate and 50m away from the upper and lower corners. The wind speed sensor 11 is used to measure the wind speed in the intake airway 6 and the return airway 8. V 1. V 2. The wind speed sensor 11 is connected to the on-site centralized processor via a wire. The wind speed sensor 11 transmits signals to the on-site centralized processor for calculation and data storage. The temperature sensor 10 is an intrinsically safe temperature sensor. The temperature sensor 10 is suspended from the top plate at the upper and lower corners. The temperature sensor 10 is used to detect real-time temperature data at the upper and lower corners and at the liquid CO2 injection port. T j , T h , T g Temperature sensor 10 is connected to the wellhead central processor via a wire, and the temperature sensor 10 transmits signals to the wellhead central processor for calculation and data storage; such as Figure 1 As shown, it includes the following steps: S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; Specifically: S2.1 Obtain information on the heat dissipation zone and oxidation heating zone within the goaf; Define the furthest distance on one side of the heat dissipation duct intake as H ji That is, the closest distance on the air inlet side of the oxidation heating zone is H ji The furthest distance on one side of the heat dissipation belt return airway is H hi That is, the closest distance on the air inlet side of the oxidation heating zone is H hi The furthest distance on the air inlet side of the oxidation heating zone is... H jm The furthest distance on the return air side of the oxidation heating zone is H hm ; S2.2 Calculate the airflow path within the goaf, taking the center of the working face as the origin; Due to the influence of airflow in the goaf, the goaf is divided into a heat dissipation zone and an oxidation heating zone. The lower corner is the air inlet and the upper corner is the air outlet. The airflow path is approximated as an ellipse. The working face support is used as the symmetrical dividing line of the ellipse to calculate the airflow path in the goaf. S2.3 Obtain wind speed information at the intake and return airways; S2.4. Based on the airflow path and wind speed information, the transport time of the airflow into the goaf is calculated using formula (1). (1); In the formula, t This refers to the transport time of underground airflow into the goaf. M s1 This is the distance from when the airflow first enters the heat dissipation zone before entering the oxidation and heating zone. M y This represents the transport distance of the airflow in the oxidation heating zone. M s2 This refers to the transport distance of the airflow after it leaves the oxidation heating zone and re-enters the heat dissipation zone; S2.5. Based on the airflow path, wind speed information and transport time, the airflow field of the goaf is calculated using formula (2); (2); In the formula, a Let be a dimensionless constant for the airflow path, based on the calculation of the elliptical airflow path in... x Maximum distance setting for the axis; S3. Calculate the average temperature of the oxidation heating zone in the goaf; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

[0023] Example 5 The rapid calculation method for the inerting range of liquid CO2 in a goaf proposed in this embodiment includes a liquid CO2 goaf injection pipe 4, a temperature sensor 10, and a wind speed sensor 11. The outlet of the liquid CO2 goaf injection pipe 4 is located on the side of the goaf oxidation and heating zone near the coal pillar. The wind speed sensor 11 is located in the intake airway and the return airway. The temperature sensor 10 is located at the upper corner, lower corner, and liquid CO2 injection port. The wind speed sensor 11 is an intrinsically safe wind speed sensor, installed in the intake airway 6 and the return airway 8 near the coal pillar on both sides. The wind speed sensor 11 is installed 2m high vertically to the bottom plate and 50m away from the upper and lower corners. The wind speed sensor 11 is used to measure the wind speed in the intake airway 6 and the return airway 8. V 1. V2. The wind speed sensor 11 is connected to the on-site centralized processor via a wire. The wind speed sensor 11 transmits signals to the on-site centralized processor for calculation and data storage. The temperature sensor 10 is an intrinsically safe temperature sensor. The temperature sensor 10 is suspended from the top plate at the upper and lower corners. The temperature sensor 10 is used to detect real-time temperature data at the upper and lower corners and at the liquid CO2 injection port. T j , T h , T g Temperature sensor 10 is connected to the wellhead central processor via a wire, and the temperature sensor 10 transmits signals to the wellhead central processor for calculation and data storage; such as Figure 1 As shown, it includes the following steps: S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; Specifically: S2.1 Obtain information on the heat dissipation zone and oxidation heating zone within the goaf; Define the furthest distance on one side of the heat dissipation duct intake as H ji That is, the closest distance on the air inlet side of the oxidation heating zone is H ji The furthest distance on one side of the heat dissipation belt return airway is H hi That is, the closest distance on the air inlet side of the oxidation heating zone is H hi The furthest distance on the air inlet side of the oxidation heating zone is... H jm The furthest distance on the return air side of the oxidation heating zone is H hm ; S2.2 Calculate the airflow path within the goaf, taking the center of the working face as the origin; Due to the influence of airflow in the goaf, the goaf is divided into a heat dissipation zone and an oxidation heating zone. The lower corner is the air inlet and the upper corner is the air outlet. The airflow path is approximated as an ellipse. The working face support is used as the symmetrical dividing line of the ellipse to calculate the airflow path in the goaf. Airflow path within the goaf: with the center of the support as the origin (0,0), the length of the working face is... H The coordinates of the lower corner are (0, H / 2), the coordinates of the upper corner are (0, - H / 2); S2.3 Obtain wind speed information at the intake and return airways; S2.4. Based on the airflow path and wind speed information, the transport time of the airflow into the goaf is calculated using formula (1). (1); In the formula, t This refers to the transport time of underground airflow into the goaf. M s1 This is the distance from when the airflow first enters the heat dissipation zone before entering the oxidation and heating zone. M y This represents the transport distance of the airflow in the oxidation heating zone. M s2 This refers to the transport distance of the airflow after it leaves the oxidation heating zone and re-enters the heat dissipation zone; The transport time consists of the transport time of the airflow in the two heat dissipation zones within the goaf and the transport time in the oxidation heating zone. The gas transport velocity in the heat dissipation zone is taken as the gas transport velocity in the intake or return airway closer to one side, and the gas transport velocity in the oxidation heat dissipation zone is fixed at 0.2 m / min. S2.5. Based on the airflow path, wind speed information and transport time, the airflow field of the goaf is calculated using formula (2); (2); In the formula, a Let be a dimensionless constant for the airflow path, based on the calculation of the elliptical airflow path in... x Maximum distance setting for the axis; S3. Calculate the average temperature of the oxidation heating zone in the goaf; Specifically: S3.1 Obtain temperature information at the upper and lower corner positions; S3.2. Based on wind speed and temperature information, the total heat of air temperature rise caused by residual coal in the goaf is calculated using formula (3). (3); In the formula, T c The total heat dissipation is the heat generated in the oxidation and heating zone of the goaf, expressed in W. S j The average cross-sectional size of the intake airway is given in meters. 2 ; S h The average cross-sectional size of the return airway is given in meters. 2 ; 1.2 represents the average density of the gas in the tunnel, kg / m³ 3 1005 is the specific heat capacity of air, J / (kg). K); S3.3 Calculate the total heat dissipation of the oxidation and heating zone of the residual coal in the goaf; The total heat dissipation of the residual coal oxidation and heating zone in the goaf consists of the heat dissipation zone of the goaf and the residual coal in the oxidation and heating zone. Due to the influence of wind speed, the residual coal in the heat dissipation zone is unlikely to accumulate heat and undergo oxidation reaction, which is mainly concentrated in the oxidation and heating zone. Therefore, the total heat caused by the residual coal to raise the temperature of the air is equal to the total heat dissipation of the residual coal oxidation and heating zone. S3.4 Calculate the temperature of the residual coal in the oxidation heating zone of the goaf according to formulas (4), (5), and (6); (4); (5); (6); In the formula, S yy The estimated surface area of ​​residual coal in the oxidation and heating zone of the goaf, in m. 2 ; α The convective heat transfer coefficient is W / (m²). 2 K), is generally obtained through experimental means or by substituting the empirical constant 14.7; T ym Temperature of residual coal in the oxidation and heating zone of the goaf, in K; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S4 specifically refers to: S4.1 Obtain liquid CO2 pipeline injection information; the injection information includes pipeline pressure, pipeline diameter, and injection duration; S4.2 Input the goaf airflow field obtained in S2.5, the temperature of residual coal in the goaf oxidation heating zone obtained in S3.4, and the liquid CO2 injection information obtained in S4.1 into the CO2 injection range coupling model; The specific coupling model for CO2 injection range is as follows: S4.2.1 Using CFD simulation software, a liquid CO2 injection model for the goaf is constructed. The injection model is used to simulate the CO2 gas diffusion range in the goaf under different injection conditions. S4.2.2 Using CO2 concentrations of 1%, 5%, and 20% in the goaf as thresholds, the furthest distance of CO2 gas diffusion to the three key thresholds under different initial conditions is calculated using a pressure injection model. x 20 , y 20 ), ( x 5, y 5), ( x 1, y 1) Obtain experimental datasets of the farthest diffusion distance under different injection conditions; S4.2.3 Using the Gaussian smoke model as the baseline model, the diffusion coefficient in the original model was optimized through experimental datasets, thus optimizing the Gaussian smoke model; S4.2.4 Obtain the optimized injection range coupling model; S4.3 Obtain the range of CO2 influence under different injection times; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

[0024] Example 6 The rapid calculation method for the liquid CO2 inerting range in goaf areas proposed in this embodiment is as follows: Figure 2 As shown, the system includes a liquid CO2 goaf injection pipeline 4, a temperature sensor 10, and a wind speed sensor 11. The outlet of the liquid CO2 goaf injection pipeline 4 is located on the side of the goaf oxidation and heating zone near the coal pillar. The wind speed sensor 11 is located in the intake and return airways. The temperature sensor 10 is located at the upper and lower corners and the liquid CO2 injection port. The wind speed sensor 11 is an intrinsically safe wind speed sensor. The wind speed sensor 11 is installed on both sides of the intake airway 6 and return airway 8 near the coal pillar. The wind speed sensor 11 is installed 2m high vertically from the bottom plate and 50m away from the upper and lower corners. The wind speed sensor 11 is used to measure the wind speed in the intake airway 6 and return airway 8. V 1. V 2. The wind speed sensor 11 is connected to the on-site centralized processor via a wire. The wind speed sensor 11 transmits signals to the on-site centralized processor for calculation and data storage. The temperature sensor 10 is an intrinsically safe temperature sensor. The temperature sensor 10 is suspended from the top plate at the upper and lower corners. The temperature sensor 10 is used to detect real-time temperature data at the upper and lower corners and at the liquid CO2 injection port. T j , T h , T g Temperature sensor 10 is connected to the wellhead central processor via a wire, and the temperature sensor 10 transmits signals to the wellhead central processor for calculation and data storage; such as Figure 1 As shown, it includes the following steps: S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; Specifically: S2.1 Obtain information on the heat dissipation zone and oxidation heating zone within the goaf, such as... Figure 3 As shown; Define the furthest distance on one side of the heat dissipation duct intake as H jiThat is, the closest distance on the air inlet side of the oxidation heating zone is H ji The furthest distance on one side of the heat dissipation belt return airway is H hi That is, the closest distance on the air inlet side of the oxidation heating zone is H hi The furthest distance on the air inlet side of the oxidation heating zone is... H jm The furthest distance on the return air side of the oxidation heating zone is H hm ; S2.2 Calculate the airflow path within the goaf, taking the center of the working face as the origin; Due to the influence of airflow in the goaf, the goaf is divided into a heat dissipation zone and an oxidation heating zone. The lower corner is the air inlet and the upper corner is the air outlet. The airflow path is approximated as an ellipse. The working face support is used as the symmetrical dividing line of the ellipse to calculate the airflow path in the goaf. Airflow path within the goaf: with the center of the support as the origin (0,0), the length of the working face is... H The coordinates of the lower corner are (0, H / 2), the coordinates of the upper corner are (0, - H / 2); S2.3 Obtain wind speed information at the intake and return airways; S2.4. Based on the airflow path and wind speed information, the transport time of the airflow into the goaf is calculated using formula (1). (1); In the formula, t This refers to the transport time of underground airflow into the goaf. M s1 This is the distance from when the airflow first enters the heat dissipation zone before entering the oxidation and heating zone. M y This represents the transport distance of the airflow in the oxidation heating zone. M s2 This refers to the transport distance of the airflow after it leaves the oxidation heating zone and re-enters the heat dissipation zone; The transport time consists of the transport time of the airflow in the two heat dissipation zones within the goaf and the transport time in the oxidation heating zone. The gas transport velocity in the heat dissipation zone is taken as the gas transport velocity in the intake or return airway closer to one side, and the gas transport velocity in the oxidation heat dissipation zone is fixed at 0.2 m / min. S2.5. Based on the airflow path, wind speed information, and transport time, the airflow field of the goaf is calculated using formula (2), such as... Figure 4 As shown; (2); In the formula, aLet be a dimensionless constant for the airflow path, based on the calculation of the elliptical airflow path in... x Maximum distance setting for the axis; S3. Calculate the average temperature of the oxidation heating zone in the goaf; Specifically: S3.1 Obtain temperature information at the upper and lower corner positions; S3.2. Based on wind speed and temperature information, the total heat of air temperature rise caused by residual coal in the goaf is calculated using formula (3). (3); In the formula, T c The total heat dissipation is the heat generated in the oxidation and heating zone of the goaf, expressed in W. S j The average cross-sectional size of the intake airway is given in meters. 2 ; S h The average cross-sectional size of the return airway is given in meters. 2 ; 1.2 represents the average density of the gas in the tunnel, kg / m³ 3 1005 is the specific heat capacity of air, J / (kg). K); S3.3 Calculate the total heat dissipation of the oxidation and heating zone of the residual coal in the goaf; The total heat dissipation of the residual coal oxidation and heating zone in the goaf consists of the heat dissipation zone of the goaf and the residual coal in the oxidation and heating zone. Due to the influence of wind speed, the residual coal in the heat dissipation zone is unlikely to accumulate heat and undergo oxidation reaction, which is mainly concentrated in the oxidation and heating zone. Therefore, the total heat caused by the residual coal to raise the temperature of the air is equal to the total heat dissipation of the residual coal oxidation and heating zone. S3.4. Calculate the temperature of the residual coal in the oxidation and heating zone of the goaf according to formulas (4), (5), and (6), such as... Figure 5 As shown; (4); (5); (6); In the formula, S yy The estimated surface area of ​​residual coal in the oxidation and heating zone of the goaf, in m. 2 ; α The convective heat transfer coefficient is W / (m²). 2 K), is generally obtained through experimental means or by substituting the empirical constant 14.7; T ym Temperature of residual coal in the oxidation and heating zone of the goaf, in K; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S4 specifically refers to: S4.1 Obtain liquid CO2 pipeline injection information; the injection information includes pipeline pressure, pipeline diameter, and injection duration; S4.2 Input the goaf airflow field obtained in S2.5, the temperature of residual coal in the goaf oxidation heating zone obtained in S3.4, and the liquid CO2 injection information obtained in S4.1 into the CO2 injection range coupling model; The specific coupling model for CO2 injection range is as follows: S4.2.1 Using CFD simulation software, a liquid CO2 injection model for the goaf is constructed. The injection model is used to simulate the CO2 gas diffusion range in the goaf under different injection conditions. S4.2.2 Using CO2 concentrations of 1%, 5%, and 20% in the goaf as thresholds, the furthest distance of CO2 gas diffusion to the three key thresholds under different initial conditions is calculated using a pressure injection model. x 20 , y 20 ), ( x 5, y 5), ( x 1, y 1) Obtain experimental datasets of the farthest diffusion distance under different injection conditions; S4.2.3 Using the Gaussian smoke model as the baseline model, the diffusion coefficient in the original model was optimized through experimental datasets, thus optimizing the Gaussian smoke model; The diffusion coefficient in the original model is optimized as follows: the diffusion coefficient is calculated according to formulas (7) to (11); (7); (8); (9); (10); (11); in, C ( x , y ) is in spatial location ( x , y CO2 gas concentration at ( ), kg / m³ 3 ; Q Injection rate, kg / s; u The ambient wind speed is in m / s. σ x , σ y , σ zThese are the diffusion coefficients in the horizontal and vertical directions, the horizontal axis direction, and the vertical direction, respectively; that is, the diffusion coefficients in the downwind, crosswind, and vertical wind directions, in meters. r Let be the radius of the injection pipe, in meters (m). P The pressure inside the pipe is in Pa; M This represents the relative molecular mass of the injected gas; R This is the constant amount of injection gas; λ The adiabatic coefficient of the gas; y’ The tangent of the airflow in the goaf area is different from that in the directly administered area; θ The angle of the airflow relative to the origin; K The optimal diffusion coefficient; x 0, y 0) indicates the location of the CO2 injection port. C’ (20%) C’ (5%) C’ (1%) are the inverse functions of gas formula (1) for CO2 concentrations of 20%, 5%, and 1%, respectively, i.e., the corresponding coordinate positions; S4.2.4 Obtain the optimized injection range coupling model; S4.3 Obtain the range of CO2 influence under different injection times; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

Claims

1. A rapid calculation method for the inerting range of liquid CO2 in goaf areas, characterized in that, Includes the following steps: S1. Construct a liquid CO2 cooling system for the goaf; S2. Calculate the airflow field in the goaf with the center of the working face as the origin; S3. Calculate the average temperature of the oxidation heating zone in the goaf; S4. Calculate the gas diffusion range of injected CO2 in the goaf; S5. Stop the CO2 cooling system injection to obtain the impact range of a single injection of liquid CO2 on the goaf.

2. The rapid calculation method for the inerting range of liquid CO2 in goaf according to claim 1, characterized in that, The liquid CO2 goaf cooling system includes a liquid CO2 goaf injection pipe (4), a temperature sensor (10), and a wind speed sensor (11); the outlet of the liquid CO2 goaf injection pipe (4) is located on the side of the goaf oxidation heating zone near the coal pillar; the wind speed sensor (11) is located in the intake airway and the return airway; the temperature sensor (10) is located at the upper corner, the lower corner, and the liquid CO2 injection port. The wind speed sensor (11) is an intrinsically safe wind speed sensor. The wind speed sensor (11) is installed on both sides of the coal pillar in the intake airway (6) and the return airway (8). The wind speed sensor (11) is installed at a height of 2m vertically to the bottom plate and at a distance of 50m from the upper and lower corners. The wind speed sensor (11) is used to measure the wind speed in the intake airway (6) and the return airway (8). V 1. V 2. The wind speed sensor (11) is connected to the on-site centralized processor via a wire. The wind speed sensor (11) transmits the signal to the on-site centralized processor via the wire for calculation and data storage.

3. The rapid calculation method for the inerting range of liquid CO2 in goaf areas according to claim 1, characterized in that, The temperature sensor (10) is an intrinsically safe temperature sensor. The temperature sensor (10) is suspended from the top plate at the upper and lower corners. The temperature sensor (10) is used to detect real-time temperature data at the upper and lower corners and the location of the liquid CO2 injection port. T j , T h , T g The temperature sensor (10) is connected to the on-site centralized processor via a wire, and the temperature sensor (10) transmits the signal to the on-site centralized processor for calculation and data storage via the wire.

4. The rapid calculation method for the inerting range of liquid CO2 in goaf according to claim 1, characterized in that, Specifically, S2 is: S2.1 Obtain information on the heat dissipation zone and oxidation heating zone within the goaf; Define the furthest distance on one side of the heat dissipation duct intake as H ji That is, the closest distance on the air inlet side of the oxidation heating zone is H ji The furthest distance on one side of the heat dissipation belt return airway is H hi That is, the closest distance on the air inlet side of the oxidation heating zone is H hi ; The furthest distance on the air inlet side of the oxidation heating zone is H jm The furthest distance on the return air side of the oxidation heating zone is H hm ; S2.2 Calculate the airflow path within the goaf, taking the center of the working face as the origin; Due to the influence of airflow in the goaf, the goaf is divided into a heat dissipation zone and an oxidation heating zone. The lower corner is the air inlet and the upper corner is the air outlet. The airflow path is approximated as an ellipse. The working face support is used as the symmetrical dividing line of the ellipse to calculate the airflow path in the goaf. S2.3 Obtain wind speed information at the intake and return airways; S2.

4. Based on the airflow path and wind speed information, the transport time of the airflow into the goaf is calculated using formula (1). （1）； In the formula, t This refers to the transport time of underground airflow into the goaf. M s1 This is the distance from when the airflow first enters the heat dissipation zone before entering the oxidation and heating zone. M y This represents the transport distance of the airflow in the oxidation heating zone. M s2 This refers to the transport distance of the airflow after it leaves the oxidation heating zone and re-enters the heat dissipation zone; S2.

5. Based on the airflow path, wind speed information and transport time, the airflow field of the goaf is calculated using formula (2); （2）； In the formula, a Let be a dimensionless constant for the airflow path, based on the calculation of the elliptical airflow path in... x The maximum distance setting for the axis.

5. The rapid calculation method for the inerting range of liquid CO2 in goaf according to claim 1, characterized in that, Specifically, S3 is: S3.1 Obtain temperature information at the upper and lower corner positions; S3.

2. Based on wind speed and temperature information, the total heat of air temperature rise caused by residual coal in the goaf is calculated using formula (3). （3）； In the formula, T c The total heat dissipation is the heat generated in the oxidation and heating zone of the goaf, expressed in W. S j The average cross-sectional size of the intake airway is given in meters. 2 ; S h The average cross-sectional size of the return airway is given in meters. 2 ; 1.2 represents the average density of the gas in the tunnel, in kg / m³. 3 1005 is the specific heat capacity of air, J / (kg). K); S3.3 Calculate the total heat dissipation of the oxidation and heating zone of the residual coal in the goaf; The total heat dissipation of the residual coal oxidation and heating zone in the goaf consists of the heat dissipation zone of the goaf and the residual coal in the oxidation and heating zone. Due to the influence of wind speed, the residual coal in the heat dissipation zone is unlikely to accumulate heat and undergo oxidation reaction, which is mainly concentrated in the oxidation and heating zone. Therefore, the total heat caused by the residual coal to raise the temperature of the air is equal to the total heat dissipation of the residual coal oxidation and heating zone. S3.4 Calculate the temperature of the residual coal in the oxidation heating zone of the goaf according to formulas (4), (5), and (6); （4）； （5）； （6）； In the formula, S yy The estimated surface area of ​​residual coal in the oxidation and heating zone of the goaf, in m. 2 ; α The convective heat transfer coefficient is W / (m²). 2 K), is generally obtained through experimental means or by substituting the empirical constant 14.7; T ym The temperature of the residual coal in the oxidation and heating zone of the goaf is K.

6. The rapid calculation method for the inerting range of liquid CO2 in goaf areas according to claim 1, characterized in that, Specifically, S4 is: S4.1 Obtain liquid CO2 pipeline injection information; the injection information includes pipeline pressure, pipeline diameter, and injection duration; S4.2 Input the goaf airflow field obtained in S2.5, the temperature of residual coal in the goaf oxidation heating zone obtained in S3.4, and the liquid CO2 injection information obtained in S4.1 into the CO2 injection range coupling model; S4.3 Obtain the range of CO2 influence under different injection times.

7. The rapid calculation method for the inerting range of liquid CO2 in goaf according to claim 4, characterized in that, The airflow path within the goaf described in S2.2: with the middle of the support as the origin (0, 0), the length of the working face is... H The coordinates of the lower corner are (0, H / 2), the coordinates of the upper corner are (0, - H / 2).

8. The rapid calculation method for the inerting range of liquid CO2 in goaf according to claim 4, characterized in that, The transport time mentioned in S2.4 consists of the transport time of the airflow in the two heat dissipation zones and the transport time of the oxidation heating zone in the goaf. The gas transport velocity in the heat dissipation zone is taken as the gas transport velocity of the intake or return air roadway closer to one side. The gas transport velocity in the oxidation heat dissipation zone is fixed at 0.2 m / min.

9. The rapid calculation method for the inerting range of liquid CO2 in goaf according to claim 6, characterized in that, The CO2 injection range coupling model described in S4.2 is specifically as follows: S4.2.1 Using CFD simulation software, a liquid CO2 injection model for the goaf is constructed. The injection model is used to simulate the CO2 gas diffusion range in the goaf under different injection conditions. S4.2.2 Using CO2 concentrations of 1%, 5%, and 20% in the goaf as thresholds, the furthest distance of CO2 gas diffusion to the three key thresholds under different initial conditions is calculated using a pressure injection model. x 20 , y 20 ), ( x 5, y 5), ( x 1, y 1) Obtain experimental datasets of the farthest diffusion distance under different injection conditions; S4.2.3 Using the Gaussian smoke model as the baseline model, the diffusion coefficient in the original model was optimized through experimental datasets, thus optimizing the Gaussian smoke model; S4.2.4 Obtain the optimized injection range coupling model.

10. The rapid calculation method for the inerting range of liquid CO2 in goaf according to claim 9, characterized in that, The optimization of the diffusion coefficient in the original model described in S4.2.3 is specifically as follows: the diffusion coefficient is calculated according to formulas (7) to (11); （7）； （8）； （9）； （10）； （11）； in, C ( x , y ) is in spatial location ( x , y CO2 concentration at ( ), kg / m³ 3 ; Q Injection rate, kg / s; u The ambient wind speed is in m / s. σ x , σ y , σ z These are the diffusion coefficients in the horizontal and vertical directions, the horizontal axis direction, and the vertical direction, respectively; that is, the diffusion coefficients in the downwind, crosswind, and vertical wind directions, in meters. r Let be the radius of the injection pipe, in meters (m). P The pressure inside the pipe is in Pa; M This represents the relative molecular mass of the injected gas; R This is the constant amount of injection gas; λ The adiabatic coefficient of the gas; y’ The tangent of the airflow in the goaf area is different from that in the directly administered area; θ The angle of the airflow relative to the origin; K The optimal diffusion coefficient; x 0, y 0) indicates the location of the CO2 injection port. C’ (20%) C’ (5%) C’ (1%) are the inverse functions of formula (1) for gas at CO2 concentrations of 20%, 5%, and 1%, respectively, i.e., the corresponding coordinate positions.

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