Method for determining key pressure-injection parameters for preventing oxidation of residual coal in goaf by using liquid CO2

Abstract

The invention belongs to the technical field of coal mines, discloses a method and a system for determining key pressure injection parameters of liquid CO2 for preventing oxidation of residual coal in a goaf, and aims at taking a coal mine as a research object, and obtaining comprehensive basic data by measuring the inclination length and mining height of a working face and the air distribution amount of the working face in detail. Meanwhile, the oxygen concentrations of different burial depths of the air inlet side of the working face in the test area are measured, and the pressure injection amount of the liquid CO2 and the inhibition effect of the liquid CO2 on coal seam oxidation can be analyzed more accurately in combination with oxygen concentration distribution in the actual coal mine environment. By analyzing the pressure injection period of the liquid CO2, the oxidation reaction of the residual coal is effectively controlled on the premise of not influencing the normal coal mine production. The method not only can be used for fire extinguishing and oxidation control under emergency conditions, but also can use a liquid CO2 injection technology as a daily prevention and control measure, so that the efficiency of coal mine safety production is improved, the risk of fire caused by oxidation is reduced, and the method has a wide industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mines, and in particular relates to a method and system for determining key injection parameters of liquid CO2 to prevent oxidation of residual coal in goaf areas. Background Art

[0002] Fire is one of the five disasters in coal mines, which seriously affects the safe, efficient and stable production of coal mines. According to statistics, about 70% of mine fires are caused by spontaneous combustion of coal. When a mine fire gets out of control, a large amount of coal resources are burned. During the combustion process, a large amount of toxic gases and smoke are released to flow in the underground tunnels, causing casualties among underground workers. It may also cause gas or coal dust explosions. During the fire fighting process, water-gas explosions may occur, which will expand the extent of the disaster.

[0003] The "Detailed Rules for Fire Prevention and Fire Fighting in Coal Mines" has relevant requirements: "Article 7: Mines that mine coal seams that are prone to spontaneous combustion and self-ignition... adopt two or more fire prevention and fire fighting technical means such as grouting, inert gas injection, and spraying of inhibitors according to the specific conditions of the mine, and implement active prevention..." However, with the emergence of the main disaster-causing factors in mines (such as rock burst) and changes in the supply and demand structure, the working face tends to be an ultra-wide working face (taking the Binchang mining area as an example), resulting in slow advancement of the working face, long oxidation time of the goaf coal, large space left in the goaf, large amount of gas desorbed by the coal, easy breakage of the protective coal pillar, easy formation of air leakage channels, large amount of coal left in the goaf, and easy accumulation to form a good heat storage environment, which brings huge pressure to the fire prevention and fire fighting working face in the goaf area. At this time, conventional nitrogen injection fire prevention and extinguishing measures face problems such as large nitrogen injection volume, easy drift, low fire prevention and extinguishing efficiency, high gas concentration in the goaf, easy to reach the explosion limit, large goaf space, poor effect of inerting and cooling measures, large amount of coal residue, wide distribution, and more hidden high-temperature points. Nitrogen injection measures have gradually failed to meet current needs, and there is an urgent need for an inert gas that can quickly inert and cool, release a large amount that is not easy to drift, and suppress gas explosions.

[0004] A large number of theoretical studies and field practices have shown that liquid carbon dioxide is a very good inerting and explosion-suppressing gas, and its fire prevention and explosion suppression effects are better than the nitrogen injection technology used on site. It has been widely used in the prevention of spontaneous combustion of coal in coal mines, emergency fire control, explosion suppression and other practical work, and the application effect is good. In addition, liquid carbon dioxide technology also meets the relevant requirements of the current "Coal Mine Fire Prevention and Extinguishing Regulations": "Article 7 Mines that mine coal seams that are prone to spontaneous combustion and spontaneous combustion... According to the specific conditions of the mine, two or more fire prevention and extinguishing technical means such as grouting, inert gas injection, and spraying of inhibitors shall be adopted to implement active prevention..." "Article 67 When underground production is concentrated and the demand for inert gas is large, ground fixed nitrogen production stations or liquid nitrogen, liquid carbon dioxide storage tanks and gasification devices can be centrally arranged; when the production (pan) areas are far apart and the demand for inert gas is large, ground fixed nitrogen production stations or liquid nitrogen, liquid carbon dioxide storage tanks and gasification devices can be arranged in different areas." However, liquid CO2 is currently commonly used for emergency control and extinguishing of spontaneous combustion of coal in mines. How to transform liquid CO2 from emergency control and extinguishing to daily prevention and control measures requires urgent exploration of a method for determining the key injection parameters of liquid CO2 to prevent oxidation of residual coal in goafs based on the actual situation of the on-site working face.

[0005] Through the above analysis, the problems and defects of the prior art are as follows:

[0006] Daily nitrogen injection preventive measures in mines have gradually failed to meet the current mine production needs. Currently, liquid CO2 is often used for emergency control and extinguishing of spontaneous combustion of coal in mines. How to transform liquid CO2 from emergency extinguishing to daily prevention and control measures requires urgent exploration of a method for determining the key injection parameters of liquid CO2 to prevent oxidation of residual coal in goafs based on the actual situation of the on-site working face. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a method for determining key injection parameters of liquid CO2 for preventing oxidation of residual coal in goaf areas.

[0008] The present invention is implemented in this way: a method for determining key injection parameters of liquid CO2 to prevent oxidation of coal in goaf areas includes:

[0009] Step 1: Take a coal mine as the research object, measure the working face inclination length, mining height and working face air volume, which are recorded as W, H and Q respectively; the air leakage volume is recorded as Q 漏 , calculated at 4% to 5% of the air volume; the porosity of the goaf is recorded as Pick

[0010] Step 2: Measure the different buried depths and corresponding oxygen concentrations on the air inlet side of the working face in the test area, and record them as L and

[0011] Step 3: Based on the data in step 2, draw a distribution diagram of oxygen concentration at different burial depths on the air inlet side; determine the lower and upper limits of the oxygen concentration range curve in the oxidation temperature rise zone, which are recorded as and The corresponding burial depths are recorded as L 1 With L 2 ; Draw a local fitting curve and fit the oxygen concentration range curve of the oxidation heating zone with a quadratic function;

[0012] A coal mine can obtain the oxygen volume within the oxidation temperature rise zone through integration

[0013]

[0014] W, H, L 1 and L 2 Substituting into formula (1), we can obtain the oxygen volume within the oxidation temperature rise zone:

[0015] Step 4: Liquid CO 2 The injection volume is analyzed, liquid CO 2 After phase change and gasification, its expansion ratio is 600 times; phase change forms CO 2 Filled in the oxidation and heating zone of the goaf, For the purpose of dilution inertization, the relationship (2) is established:

[0016]

[0017] By rearranging equation (2), we can obtain the liquid CO in the oxidation heating zone: 2 The injection volume is calculated by formula (3);

[0018]

[0019] Will W. H.L 1 and L 2 Liquid CO can be obtained by using formula (3) 2 Injection volume

[0020] Step 5: Analyze the injection cycle; the oxygen concentration in the oxidation heating zone of the goaf reaches As the boundary, the equation is established considering the influence of air leakage, as shown in formula (4);

[0021]

[0022] In the formula, is the oxygen concentration in the fresh air flow, %; k is the CO2 displacement by air leakage in the goaf2 Effective coefficient, due to CO 2 The molecular mass is large, compared with air, the displacement efficiency is lower, and the value is 0.6;

[0023] By rearranging equation (4), we can obtain the liquid CO in the oxidation warming zone: 2 The injection cycle calculation formula is (5);

[0024]

[0025] Will W. H.L 1 , L 2 , Q 漏 , k and Liquid CO can be obtained by using formula (5) 2 Injection cycle T;

[0026] Step 6: The thickness of coal left in the goaf of the working face is:

[0027]

[0028] Where, h is the thickness of coal left in the goaf, m; k 1 is the recovery rate of the working face, %, and takes the value as 97%;

[0029] The total amount of coal left in the oxidation and warming zone of the goaf is:

[0030]

[0031] Where M is the total amount of coal left in the goaf, t; ρ is the density of the coal body, t / m 3 ;(ρ=1.4t / m 3 )

[0032] From step 5, liquid CO 2 The injection cycle is T. Combined with the coal spontaneous ignition experiment, it can be seen that the oxidation and temperature rise rate of coal in the latent stage is relatively slow, basically 0.5℃ / d. Therefore, the maximum coal temperature change during the injection cycle is 0.5T℃, that is, Δt=0.5T℃;

[0033] According to the laws of thermodynamics, the heat generated by the oxidation and temperature rise of the residual coal during the injection cycle is:

[0034] q=cMΔt (8)

[0035] Where c is the specific heat capacity of coal, kJ / (kg·K); (c=1.00~1.26kJ / (kg·K))

[0036] Combine equations (6) to (8), and let H, k 1 , By introducing the parameter ρ, we can obtain the heat q generated by the oxidation and temperature rise of the residual coal during the injection cycle;

[0037] Step 7: per kilogram of liquid CO 2 The heat absorbed by the phase change is:

[0038] Q t =i t +C pp Δt (9)

[0039] Liquid CO 2 The heat absorbed by the phase change is greatly affected by the saturation temperature. After calculation, the liquid CO 2 The temperature in the tank is around -25°C, the saturated vapor pressure is 1.66MPa, and the CO 2 The latent heat of vaporization is 293.63 kJ / kg;

[0040] In step 4, the calculated liquid CO 2 Injection volume Then the liquid CO injected into the goaf can be calculated as 2 Heat absorbed by phase change Q t .

[0041] Q t Compare and analyze with q. If there is Q t >q relationship, the key parameters injection cycle and injection volume are verified from the perspective of cooling.

[0042] Another object of the present invention is to provide a liquid CO 2 The key injection parameter determination system for preventing oxidation of coal in goaf includes:

[0043] The measurement module is used to measure the inclined length, mining height and air volume of the working face of a coal mine; and to measure the different buried depths and corresponding oxygen concentrations on the air inlet side of the working face in the test area;

[0044] The determination module is used to draw the oxygen concentration distribution map at different buried depths on the air inlet side; determine the lower and upper limits of the oxygen concentration range curve in the oxidation warming zone, which are recorded as and The corresponding burial depths are recorded as L 1 With L 2 ; Draw a local fitting curve and fit the oxygen concentration range curve of the oxidation heating zone with a quadratic function;

[0045] Analysis module for liquid CO 2 The injection volume is analyzed, liquid CO 2 After phase change and gasification, the injection cycle is analyzed;

[0046] Calculation module, used to calculate the thickness of coal left in the goaf of the working face; per kilogram of liquid CO 2 The heat absorbed by the phase change verifies the key parameters from a thermal point of view.

[0047] Another object of the present invention is to provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for determining key injection parameters of liquid CO2 to prevent oxidation of coal left in goaf areas.

[0048] Another object of the present invention is to provide a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the method for determining key injection parameters of liquid CO2 to prevent oxidation of coal left in goaf areas.

[0049] Another object of the present invention is to provide an information data processing terminal, which is used to implement the key injection parameter determination system of the liquid CO2 to prevent the oxidation of coal left in the goaf.

[0050] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0051] First, the present invention takes a coal mine as the research object, measures the inclination length of its working face, mining height and working face air distribution; measures the different burial depths and corresponding oxygen concentrations on the air inlet side of the working face in the test area; analyzes the liquid CO2 injection volume; analyzes the injection cycle; and can transform liquid CO2 from emergency control to daily prevention and control measures.

[0052] Second, the expected benefits and commercial value of the technical solution of the present invention after transformation are as follows: more than 90% of my country's coal seams are prone to spontaneous combustion and self-ignition coal seams, and more than 130 large and medium-sized mining areas in 25 major coal-producing provinces and regions in the country are threatened by spontaneous combustion of coal seams to varying degrees. Article 7 of the "Detailed Rules for Coal Mine Fire Prevention and Extinguishing" stipulates that mines that mine coal seams prone to spontaneous combustion and self-ignition must prepare special designs for mine fire prevention and extinguishing. As an important part of the special design for fire prevention and extinguishing, injection measures have significant economic benefits in promotion and application.

[0053] The technical solution of the present invention fills the technical gap in the industry at home and abroad: currently liquid CO2 is often used for emergency control and extinguishing of spontaneous combustion of coal in mines. How to transform liquid CO2 from emergency control and extinguishing to daily prevention and control measures, there is no method for calculating key parameters for daily prevention and control. Therefore, this method proposes a method for calculating key parameters for daily prevention and control of liquid CO2.

[0054] Third, the present invention has made significant progress in solving many technical problems existing in the industrial application of existing technologies. First, the existing technology lacks effective means in the prevention and control of oxidation of coal residues in goaf areas, and cannot accurately control the injection volume and cycle of liquid CO2, resulting in the inability to fundamentally solve the problem of oxidation of coal residues in goaf areas. The present invention can accurately determine the injection volume and cycle of liquid CO2 through a scientific parameter calculation method, thereby effectively inhibiting the oxidation and temperature rise of coal residues in goaf areas and preventing the occurrence of spontaneous combustion accidents.

[0055] Secondly, traditional methods generally have problems such as low efficiency and complex operation in practical applications, and cannot cope with the complex geological conditions of goaf areas. This invention proposes an innovative method based on field measurement and data analysis. By integrating multiple measurement data, such as the inclination length of the working face, mining height, oxygen concentration, etc., it realizes accurate monitoring and control of the oxidation warming zone in the goaf area. This method not only improves the simplicity of operation, but also greatly improves work efficiency and accuracy.

[0056] In addition, another shortcoming of the prior art is that it mostly uses a single method to treat the oxidation and heating zone in the goaf, which lacks systematicity and comprehensiveness and often cannot completely eliminate fire hazards. The present invention introduces liquid CO2 injection technology and combines it with thermodynamic calculations to effectively cool the coal-residing area, forming an inert environment and further enhancing the fire prevention effect. This multi-level prevention and control strategy has made it possible to more thoroughly solve the problem of coal oxidation in the goaf.

[0057] Finally, the present invention has demonstrated significant technological progress in practical applications, which is specifically reflected in the innovation, practicality and operability of its technical solution. By optimizing the usage and injection cycle of liquid CO2, the present invention not only reduces costs, but also reduces the impact on the environment, with good economic and environmental benefits. Overall, the present invention greatly improves the safety and reliability of goaf fire prevention and control, and provides a solid technical guarantee for safe production in coal mines.

[0058] Fourth, the present invention solves the technical problem of spontaneous combustion of coal body due to air leakage and changes in oxygen concentration in the oxidation warming zone during the oxidation of coal in existing coal mine goaf areas. By determining the key liquid CO2 injection parameters, the present invention can effectively control the oxygen concentration in the oxidation warming zone, thereby reducing the oxidation rate of the coal body and preventing the occurrence of spontaneous combustion. In the existing coal mine goaf fire prevention technology, the use of liquid CO2 has significant advantages. It can not only quickly cool the coal body, but also further inhibit the oxidation and heating of the coal body through its phase change endothermic process, thereby improving the fire prevention effect.

[0059] The method calculates the air leakage and porosity of the goaf by accurately measuring parameters such as the inclined length of the working face, the mining height, and the air distribution, and then determines the oxygen concentration distribution in the oxidation warming zone and its corresponding burial depth range. Combining the expansion multiple of liquid CO2 after phase change and gasification and the target diluted oxygen concentration, the present invention establishes a mathematical model for calculating the liquid CO2 injection amount to ensure that the amount of CO2 injected each time can effectively cover and dilute the oxygen concentration in the oxidation warming zone. The automated control and remote monitoring functions of this process make the operation easier and more accurate.

[0060] In addition, the present invention scientifically determines the cycle and injection volume of CO2 injection by analyzing the oxygen concentration in the oxidation heating zone and the heat generated by the oxidation heating of the residual coal, combined with the thermodynamic characteristics of the coal body and the latent heat of liquid CO2 gasification. Through theoretical calculation and experimental verification, it is ensured that during the injection cycle, the liquid CO2 can effectively absorb the heat generated by the oxidation heating, prevent the continuous increase of the coal body temperature, and further enhance the reliability of fire prevention.

[0061] In summary, the present invention has made significant technical progress in the prevention and control of spontaneous combustion of coal in coal mine goaf areas. Through reasonable liquid CO2 injection volume and cycle control, the present invention not only improves mine safety, but also reduces the risk of coal mine fire accidents. This technology can be widely used in fire prevention projects in coal mine goaf areas, and has high industrial application value and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a flow chart of a method for determining key injection parameters of liquid CO2 for preventing oxidation of residual coal in goaf areas provided by an embodiment of the present invention.

[0063] Figure 2 This is a structural block diagram of a system for determining key injection parameters of liquid CO2 for preventing oxidation of coal residues in goaf areas provided by an embodiment of the present invention.

[0064] Figure 3 This is a distribution diagram of oxygen concentration at different buried depths on the air inlet side provided by an embodiment of the present invention.

[0065] Figure 4 The embodiment of the present invention provides a method for injecting liquid CO into the goaf. 2 After O 2 Schematic diagram of concentration variation over time. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0067] Example 1: Fire prevention application in large open-pit coal mine goaf

[0068] In a large open-pit coal mine, a large number of goafs have been formed due to long-term mining. These areas are at high risk of spontaneous combustion due to oxidation and heating of the coal body. In order to prevent the occurrence of spontaneous combustion accidents, the mine adopts the liquid CO2 injection method of the present invention. First, the engineering and technical personnel measured the inclined length, mining height and air distribution of the working face, calculated the air leakage and the porosity of the goaf, and determined the oxygen concentration distribution and burial depth range of the oxidation and heating zone. According to the expansion multiple and dilution target of the liquid CO2, the amount of CO2 injected at one time is calculated, and the injection cycle is set in combination with the actual situation on site.

[0069] In actual operation, liquid CO2 is injected into the oxidation warming zone of the goaf through a specific pipeline system. The rapid expansion of CO2 after gasification effectively covers the entire oxidation warming zone. The phase change of CO2 absorbs the heat generated by the oxidation of the coal body, significantly reduces the temperature, and inhibits the oxidation process. In the pilot application of the entire mining area, this method successfully prevented the occurrence of multiple spontaneous combustion in the goaf, providing a strong guarantee for the safe production of open-pit coal mines.

[0070] Example 2: Fire protection application under complex geological conditions in underground coal mines

[0071] In an underground coal mine with complex geological conditions, the risk of spontaneous combustion of coal in the deep goaf of the mine increased due to changes in stratum pressure and air leakage. In order to meet this challenge, the mine management introduced the liquid CO2 injection technology of the present invention. The technical team arranged multiple measurement points in the working face and goaf of the mine, measured and analyzed the oxygen concentration and burial depth data of the oxidation warming zone, and determined the range of the oxidation warming zone and the optimal location for CO2 injection.

[0072] During the implementation process, liquid CO2 was injected into the goaf in batches, and the multi-point injection method was used to ensure that CO2 was evenly distributed in the oxidation and heating zone to prevent spontaneous combustion caused by excessive local oxygen concentration. The application of this method not only successfully controlled the rise in coal temperature, but also ensured the continued effectiveness of CO2 by real-time monitoring and adjusting the injection parameters. In the long-term application of this mine, no spontaneous combustion accidents in the goaf occurred, which effectively extended the safe mining period of the mine and significantly improved the economic benefits of the mining area.

[0073] like Figure 1 As shown, a method for determining key injection parameters of liquid CO2 to prevent oxidation of coal in goaf provided by an embodiment of the present invention includes the following steps:

[0074] S101, taking a coal mine as the research object, measured its working face inclination length, mining height and working face air volume;

[0075] They are denoted as W, H and Q respectively; the air leakage is denoted as Q 漏 , calculated at 4% to 5% of the air volume; the porosity of the goaf is recorded as Pick

[0076] S102, measuring different buried depths and corresponding oxygen concentrations on the air inlet side of the working face in the test area;

[0077] Denoted as L and

[0078] S103, based on the data in S102, draw a distribution diagram of oxygen concentration at different burial depths on the air inlet side; determine the lower limit and upper limit of the oxygen concentration range curve in the oxidation temperature rise zone;

[0079] Denoted as and The corresponding burial depths are recorded as L 1 With L 2 ; Draw a local fitting curve and fit the oxygen concentration range curve of the oxidation heating zone with a quadratic function;

[0080] A coal mine can obtain the oxygen volume within the oxidation temperature rise zone through integration

[0081]

[0082] W, H, L 1 and L 2 Substituting into formula (1), we can obtain the oxygen volume within the oxidation temperature rise zone:

[0083] S104, for liquid CO 2 Analyze the injection volume;

[0084] Liquid CO 2 After phase change and gasification, its expansion ratio is 600 times; phase change forms CO 2 Filled in the oxidation and heating zone of the goaf, For the purpose of dilution inertization, the relationship (2) is established:

[0085]

[0086] By rearranging equation (2), we can obtain the liquid CO in the oxidation heating zone: 2 The injection volume is calculated by formula (3);

[0087]

[0088] Will W. H.L 1 and L 2 Liquid CO can be obtained by using formula (3) 2 Injection volume

[0089] S105, analyzing the injection cycle;

[0090] The oxygen concentration in the goaf oxidation heating zone reaches As the boundary, the equation is established considering the influence of air leakage, as shown in formula (4);

[0091]

[0092] In the formula, is the oxygen concentration in the fresh air flow, %; k is the CO2 displacement by air leakage in the goaf 2 Effective coefficient, due to CO 2 The molecular mass is large, compared with air, the displacement efficiency is lower, and the value is 0.6;

[0093] By rearranging equation (4), we can obtain the liquid CO in the oxidation warming zone: 2 The injection cycle calculation formula is (5);

[0094]

[0095] Will W. H.L 1 , L 2 , Q 漏 , k and Liquid CO can be obtained by using formula (5) 2 Injection cycle T;

[0096] S106, the thickness of coal residue in the goaf of the working face is:

[0097]

[0098] Where, h is the thickness of coal left in the goaf, m; k 1 is the recovery rate of the working face, %, and takes the value as 97%;

[0099] The total amount of coal left in the oxidation and warming zone of the goaf is:

[0100]

[0101] Where M is the total amount of coal left in the goaf, t; ρ is the density of the coal body, t / m 3 ;(ρ=1.4t / m 3 )

[0102] S105 liquid CO 2The injection cycle is T. Combined with the coal spontaneous ignition experiment, it can be seen that the oxidation and temperature rise rate of coal in the latent stage is relatively slow, basically 0.5℃ / d. Therefore, the maximum coal temperature change during the injection cycle is 0.5T℃, that is, Δt=0.5T℃;

[0103] According to the laws of thermodynamics, the heat generated by the oxidation and temperature rise of the residual coal during the injection cycle is:

[0104] q = cMΔt (8) where c is the specific heat capacity of coal, kJ / (kg·K); (c = 1.00 to 1.26 kJ / (kg·K))

[0105] Combine equations (6) to (8), and let H, k 1 , By introducing the parameter ρ, we can obtain the heat q generated by the oxidation and temperature rise of the residual coal during the injection cycle;

[0106] S107, per kg liquid CO 2 The heat absorbed by the phase change is:

[0107] Q t =i t +C pp Δt (9)

[0108] Liquid CO 2 The heat absorbed by the phase change is greatly affected by the saturation temperature. After calculation, the liquid CO 2 The temperature in the tank is around -25°C, the saturated vapor pressure is 1.66MPa, and the CO 2 The latent heat of vaporization is 293.63 kJ / kg;

[0109] In S104, the calculated liquid CO 2 Injection volume Then the liquid CO injected into the goaf can be calculated as 2 Heat absorbed by phase change Q t .

[0110] Q t Compare and analyze with q. If there is Q t >q relationship, the key parameters injection cycle and injection volume are verified from the perspective of cooling.

[0111] like Figure 2 As shown, a key injection parameter determination system for liquid CO2 to prevent oxidation of coal in goaf provided by an embodiment of the present invention includes:

[0112] The measurement module is used to measure the inclined length, mining height and air volume of the working face of a coal mine; and to measure the different buried depths and corresponding oxygen concentrations on the air inlet side of the working face in the test area;

[0113] The determination module is used to draw the oxygen concentration distribution map at different buried depths on the air inlet side; determine the lower and upper limits of the oxygen concentration range curve in the oxidation warming zone, which are recorded as and The corresponding burial depths are recorded as L 1 With L 2 ; Draw a local fitting curve and fit the oxygen concentration range curve of the oxidation heating zone with a quadratic function;

[0114] Analysis module for liquid CO 2 The injection volume is analyzed, liquid CO 2 After phase change and gasification, the injection cycle is analyzed;

[0115] Calculation module, used to calculate the thickness of coal left in the goaf of the working face; per kilogram of liquid CO 2 The heat absorbed by the phase change verifies the key parameters from a thermal point of view.

[0116] Another object of the present invention is to provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for determining key injection parameters of liquid CO2 to prevent oxidation of coal left in goaf areas.

[0117] Another object of the present invention is to provide a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the method for determining key injection parameters of liquid CO2 to prevent oxidation of coal left in goaf areas.

[0118] Another object of the present invention is to provide an information data processing terminal, which is used to implement the key injection parameter determination system of the liquid CO2 to prevent the oxidation of coal left in the goaf.

[0119] The present invention is specifically implemented:

[0120] 1. Analysis from the perspective of dilution and inerting

[0121] 1.1 Oxygen volume in the oxidation heating zone (V (O2) )analyze

[0122] Depend on Figure 3 It can be seen that the goaf O 2 The oxygen concentration is nonlinearly attenuated along the buried depth, and the concentration distribution is uneven. Therefore, the analysis by a set oxygen concentration is prone to large errors in the results. Therefore, the oxygen volume in the oxidation heating zone of the goaf is solved by integration. The inclined length of a coal mine working face is W = 300m, the mining height is H = 9.8m, and the working face air volume is Q = 3000m 3 / h, the air leakage is calculated as 4% to 5% of the air supply volume, Q漏 =120~150m 3 / h, the porosity of the goaf is calculate.

[0123] According to the oxygen concentration distribution at different buried depths on the air inlet side of the working face, the oxidation temperature rise zone (lower limit: C 1(O2) =8%; Upper limit: C 2(O2) =18%) range curve is fitted with a quadratic function (where C (O2) =17.6%, L 1 =128.5m; when C (O2) =9.7%, L 2 =198.7m). A coal mine can obtain the oxygen volume (V (O2) ):

[0124]

[0125] W, H, L 1 and L 2 Substituting into formula (1), we can obtain the oxygen volume V within the oxidation temperature rise zone: (O2) is: 2799.3504m 3 .

[0126] 1.2 Liquid CO 2 Injection volume (V LCO2 )analyze

[0127] To make liquid CO 2 Fire prevention and extinguishing has become a routine preventive measure, requiring liquid CO 2 The injection volume is analyzed, liquid CO 2 After phase change and gasification, its expansion ratio is 600 times. Phase change forms CO 2 Filled in the oxidation and warming zone of the goaf, the C 1(O2) =8% is the dilution inerting target, and the relationship (2) is established.

[0128]

[0129] By rearranging equation (2), we can obtain the liquid CO in the oxidation heating zone: 2 The injection volume is calculated using formula (3).

[0130]

[0131] V (O2) , C 1(O2) ,W, H.L 1 and L 2 Liquid CO can be obtained by using formula (3)2 The injection volume is 23.92t.

[0132] 1.3 Liquid CO 2 Injection cycle (T) analysis

[0133] Liquid CO 2 As a routine preventive measure, due to the constant air leakage in the goaf, the CO in the oxidation heating zone 2 will be driven by wind currents, but due to CO 2 The molecular mass is larger, heavier than air, and the expulsion efficiency is lower. 2 It can be left in the goaf for a period of time. Therefore, in addition to the single injection volume, the injection cycle needs to be analyzed. 2(O2) =18% is taken as the boundary, and the influence of air leakage is considered to establish the equation, as shown in formula (4).

[0134]

[0135] In the formula, C 0(O2) is the oxygen concentration in the fresh air flow, %; k is the CO2 displacement by air leakage in the goaf 2 Effective coefficient, due to CO 2 The molecular mass is large, and the displacement efficiency is lower than that in air, taking 0.6.

[0136] By rearranging equation (4), we can obtain the liquid CO in the oxidation warming zone: 2 The injection cycle is calculated using formula (5).

[0137]

[0138] C 2(O2) 、V (O2) 、V LCO2 ,W, H.L 1 , L 2 , Q 漏 , k and C 0(O2) Liquid CO can be obtained by using formula (5) 2 The injection cycle is 8 to 10 days.

[0139] 2. Analysis from the perspective of phase change cooling

[0140] 2.1 Analysis of heat dissipation of coal residue in goaf

[0141] The thickness of coal residue in the goaf of the working face is:

[0142]

[0143] Where, h is the thickness of coal left in the goaf, m; k 1is the recovery rate of the working face, %, and takes the value as 97%;

[0144] The total amount of coal left in the oxidation and warming zone of the goaf is:

[0145]

[0146] Where M is the total amount of coal left in the goaf, t; ρ is the density of the coal body, t / m 3 . (ρ=1.4t / m 3 )

[0147] Liquid CO 2 The injection cycle is 8 to 10 days. Combined with the coal spontaneous ignition experiment, it can be seen that the oxidation and temperature rise rate of coal in the latent stage is slow, basically 0.5℃ / d. Therefore, the maximum coal temperature change during the injection cycle is 5℃, that is, Δt=5℃.

[0148] According to the laws of thermodynamics, the heat generated by the oxidation and temperature rise of the residual coal during the injection cycle is:

[0149] q=cMΔt (8)

[0150] Where c is the specific heat capacity of coal, kJ / (kg·K). (c=1.00~1.26kJ / (kg·K))

[0151] Combine equations (6) to (8), and let H, k 1 , By inputting parameters such as ρ, it can be obtained that the heat generated by the oxidation and temperature rise of the residual coal during the injection cycle is 1430250~1802115kJ.

[0152] 2.2 Liquid CO 2 Phase change absorption heat analysis

[0153] Per kg of liquid CO 2 The heat absorbed by the phase change is:

[0154] Q t =i t +C pp Δt (9)

[0155] Liquid CO 2 The heat absorbed by the phase change is greatly affected by the saturation temperature. After calculation, the liquid CO 2 The temperature in the tank is around -25°C, the saturated vapor pressure is 1.66MPa, and the CO 2 The latent heat of vaporization is 293.63 kJ / kg.

[0156] Calculated liquid CO 2 The injection volume is 23.92t, and the liquid CO injected into the goaf 2 The heat absorbed by phase change is: 7023629.6kJ.

[0157] From the above analysis, we can see that liquid CO 2 The heat generated by phase change adsorption is about 4-5 times the heat generated by coal oxidation, which can consume the heat generated by the oxidation of residual coal and reduce the temperature of the goaf.

[0158] like Figure 4 As shown in the figure, according to the injection volume calculated by a coal mine, after liquid CO2 is injected into the goaf, the O2 concentration in the oxidation warming zone is diluted and rapidly reduced to around 5%; with the continuous air leakage in the goaf, the CO2 concentration in the oxidation warming zone is gradually carried away by the wind flow, and the O2 concentration gradually increases; when the O2 concentration in the oxidation warming zone gradually rises to around 18%, liquid CO2 is injected again at an interval of 10d (cycle) to achieve daily prevention and control of spontaneous combustion of coal in the goaf.

[0159] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0160] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for determining key injection parameters of liquid CO2 to prevent oxidation of coal in goaf, characterized in that: The following steps are involved: a) Measure the inclined length (W), mining height (H) and air supply (Q) of the coal mine working face, and calculate the air leakage (Q leakage) and the porosity (φ) of the goaf, where Q leakage is calculated as 4% to 5% of the air supply, and φ is taken as 10%; b) Measure different burial depths (L) and corresponding oxygen concentrations (C) on the air inlet side of the working face, draw an oxygen concentration distribution diagram based on the data, determine the upper and lower limits (C1, C2) of the oxygen concentration range in the oxidation warming zone and its corresponding burial depths (L1, L2), and calculate the oxygen volume (V) within the oxidation warming zone by integration; c) According to the expansion multiple of liquid CO2 after phase change and gasification and the target diluted oxygen concentration, a calculation formula for the liquid CO2 injection volume in the oxidation warming zone is established to calculate the liquid CO2 injection volume for one time.

2. The method according to claim 1, characterized in that The following steps are involved: a) Analyze the injection cycle of liquid CO2 in the oxidation warming zone, take the oxygen concentration in the oxidation warming zone of the goaf as 18% as the boundary, combine the air leakage (Qleakage) and the effective coefficient (k) of air leakage in the goaf to displace CO2, establish an equation to calculate the injection cycle (T) of liquid CO2; b) Based on the thermodynamic properties of coal and the latent heat of gasification of liquid CO2, the heat generated by the oxidation and temperature rise of the residual coal during the injection cycle and the heat absorbed by the phase change of liquid CO2 are calculated to verify the rationality of the injection cycle and injection volume.

3. The method according to claim 1, characterized in that The specific steps include: Step 1: Take the coal mine as the research object, measure the working face inclination length, mining height and working face air volume, which are recorded as W, H and Q respectively; the air leakage volume is recorded as Q 漏 , calculated at 4% to 5% of the air volume; the porosity of the goaf is recorded as Pick Step 2: Measure the different buried depths and corresponding oxygen concentrations on the air inlet side of the working face in the test area, and record them as L and Step 3: Based on the data in step 2, draw a distribution diagram of oxygen concentration at different burial depths on the air inlet side; determine the lower and upper limits of the oxygen concentration range curve in the oxidation temperature rise zone, which are recorded as and The corresponding burial depths are recorded as L1 and L2 respectively; a local fitting curve is drawn, and a quadratic function is fitted to the oxygen concentration range curve of the oxidation warming zone; Coal mines can obtain the oxygen volume within the oxidation temperature rise zone through integration W, H, Substituting L1 and L2 into formula (1), we can obtain the oxygen volume within the oxidation temperature rise zone. Step 4: Analyze the injection volume of liquid CO2. After the liquid CO2 changes phase and becomes gas, its expansion multiple is 600 times. The phase change forms CO2 and fills the oxidation and warming zone in the goaf. For the purpose of dilution inertization, the relationship (2) is established: By rearranging formula (2), we can obtain the calculation formula (3) for the amount of liquid CO2 injected once in the oxidation warming zone; Will W. Substituting H, L1 and L2 into formula (3) can obtain the liquid CO2 injection volume Step 5: Analyze the injection cycle; the oxygen concentration in the oxidation heating zone of the goaf reaches As the boundary, the equation is established considering the influence of air leakage, as shown in formula (4); In the formula, is the oxygen concentration in the fresh air flow, %; k is the effective coefficient of CO2 displacement by air leakage in the goaf. Since the molecular mass of CO2 is large, the displacement efficiency is lower than that in air, so it is taken as 0.6; By rearranging formula (4), we can obtain the calculation formula (5) for the liquid CO2 injection cycle in the oxidation warming zone; Will W. H, L1, L2, Q 漏 , k and Substituting into formula (5) can obtain the liquid CO2 injection cycle T; Step 6: The thickness of coal left in the goaf of the working face is: Where, h is the thickness of coal left in the goaf, m; k1 is the recovery rate of the working face, %, and the value is 97%; The total amount of coal left in the oxidation and warming zone of the goaf is: Where M is the total amount of coal left in the goaf, t; ρ is the density of the coal body, t / m 3 ;(ρ=1.4t / m 3 ) The injection cycle of liquid CO2 in step 5 is T. Combined with the coal spontaneous combustion experiment, it can be seen that the oxidation and temperature rise rate of coal in the latent stage is relatively slow, basically 0.5℃ / d. Therefore, the maximum coal temperature change during the injection cycle is 0.5T℃, that is, Δt=0.5T℃; According to the laws of thermodynamics, the heat generated by the oxidation and temperature rise of the residual coal during the injection cycle is: q=cMΔt (8) Where c is the specific heat capacity of coal, kJ / (kg·K); (c=1.00~1.26kJ / (kg·K)) Combine equations (6) to (8), and transform H, k1, By introducing the parameter ρ, we can obtain the heat q generated by the oxidation and temperature rise of the residual coal during the injection cycle; Step 7: The heat absorbed by the phase change of each kilogram of liquid CO2 is: Q t =i t +C pp Δt (9) The heat absorbed by the phase change of liquid CO2 is greatly affected by the saturation temperature. After calculation, the temperature in the liquid CO2 storage tank is about -25℃, the saturated vapor pressure is 1.66MPa, and the latent heat of CO2 gasification is 293.63kJ / kg; In step 4, the calculated liquid CO2 injection volume Then the heat absorbed by the phase change of liquid CO2 injected into the goaf can be calculated as Q t ; Q t Compare and analyze with q. If there is Q t >q relationship, the key parameters injection cycle and injection volume are verified from the perspective of cooling.

4. A system for determining key injection parameters of liquid CO2 for preventing oxidation of coal residues in goafs, which implements the method for determining key injection parameters of liquid CO2 for preventing oxidation of coal residues in goafs as claimed in claim 1, characterized in that: The key injection parameter determination system of the liquid CO2 to prevent oxidation of coal in goaf includes: The measurement module is used to measure the inclined length, mining height and air volume of the working face of a coal mine; and to measure the different buried depths and corresponding oxygen concentrations on the air inlet side of the working face in the test area; The determination module is used to draw the oxygen concentration distribution map at different buried depths on the air inlet side; determine the lower and upper limits of the oxygen concentration range curve in the oxidation warming zone, which are recorded as and The corresponding burial depths are recorded as L1 and L2 respectively; a local fitting curve is drawn, and a quadratic function is fitted to the oxygen concentration range curve of the oxidation warming zone; The analysis module is used to analyze the injection volume of liquid CO2 and the injection cycle after the liquid CO2 phase changes and gasifies; The calculation module is used to calculate the thickness of the residual coal in the goaf of the working face; the heat absorbed by the phase change of each kilogram of liquid CO2 is used to verify the key parameters from a thermal perspective.

5. A liquid CO2 injection method for preventing oxidation and spontaneous combustion of coal in coal mine goaf, characterized in that: The following steps are involved: a) Measure the inclined length (W), mining height (H) and air supply (Q) of the coal mine working face, and calculate the air leakage (Qleakage) based on 4% to 5% of the air supply, and determine the porosity (φ) of the goaf to be 10%; b) Measure different burial depths (L) and corresponding oxygen concentrations (C) on the air inlet side of the working face, draw an oxygen concentration distribution diagram, determine the upper and lower limits (C1, C2) of the oxygen concentration range of the oxidation warming zone and its corresponding burial depths (L1, L2), and calculate the oxygen volume (V) within the oxidation warming zone by integration; c) According to the expansion multiple of liquid CO2 after phase change and gasification and the target diluted oxygen concentration, a calculation formula for the liquid CO2 injection volume in the oxidation warming zone is established to calculate the liquid CO2 injection volume for one time.

6. The method according to claim 5, characterized in that Further comprising the steps of: a) Analyze the injection cycle of liquid CO2 in the oxidation warming zone, take the oxygen concentration in the oxidation warming zone of the goaf as 18% as the boundary, combine the air leakage (Qleakage) and the effective coefficient (k) of air leakage in the goaf to displace CO2, and calculate the injection cycle (T) of liquid CO2; b) Based on the thermodynamic properties of coal and the latent heat of gasification of liquid CO2, the heat generated by the oxidation and temperature rise of the residual coal and the heat absorbed by the phase change of liquid CO2 during the injection cycle are calculated to verify the rationality of the injection cycle and injection volume.

7. A liquid CO2 injection system for fire prevention in open-pit coal mine goaf, characterized in that: The system comprises: a) Equipped with devices for measuring the inclination length of the working face, the mining height and the air supply volume, so as to calculate the air leakage volume and the porosity of the goaf; b) Monitor the oxygen concentration on the air inlet side of the working face through infrared or other sensors, and draw an oxygen concentration distribution map based on the monitored data; c) A device is provided for automatically controlling the injection volume and cycle of liquid CO2, so as to prevent spontaneous combustion of coal by adjusting the injection volume and cycle of liquid CO2.

8. A method for fire prevention injection of liquid CO2 in underground coal mine goaf with complex geological conditions, characterized in that: The method comprises: a) Arrange multiple measurement points in the deep goaf of the mine to measure the oxygen concentration and burial depth data of the oxidation warming zone, determine the range of the oxidation warming zone and the optimal injection position of liquid CO2; b) Based on the thermodynamic parameters of coal density and specific heat capacity, calculate the heat generated by the oxidation and heating of the residual coal during the injection cycle, and adjust the CO2 injection parameters in combination with the latent heat of phase change of liquid CO2 to ensure that the temperature in the oxidation and heating zone is always within a safe range.

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