Method and system for desorbing residual coal gas in protected goaf

Abstract

The invention relates to the technical field of coal mine safety, and provides a protected layer goaf residual coal gas desorption method and system. The method comprises the following steps: calculating an ideal gas desorption rate of residual coal at a working face open-off cut distance # imgabs 1 # at a desorption time # imgabs 2 # according to a goaf theoretical temperature at a working face open-off cut distance # imgabs 0 # in a protected layer goaf residual coal gas desorption process; meanwhile, according to a goaf residual coal lumpiness actual measurement value, a residual coal thickness actual measurement value and an actual measurement gas desorption rate at different distances from the working face open-off cut, a desorption correction coefficient # imgabs5 # of residual coal at the distance # imgabs3 # from the working face open-off cut at desorption time # imgabs4 # is calculated; and the ideal gas desorption rate and the desorption correction coefficient are input into the constructed gas desorption correction model, and the corrected gas desorption rate of the residual coal at the desorption time # imgabs7 # at the working face open-off cut distance # imgabs6 # is determined, so that the accuracy and the reliability of the gas desorption analysis of the residual coal in the goaf are effectively improved.

Description

Technical Field

[0001] This application relates to the technical field of coal mine safety, and particularly relates to a method and system for desorbing gas from residual coal in the goaf of a protected coal seam. Background Art

[0002] In coal mine safety production, the gas desorption process of residual coal in the goaf is coupled with the oxidation and temperature rise process, forming a complex environment with coexisting coal spontaneous combustion and gas disasters, which seriously threatens the safety of the mine. Existing research shows that an increase in temperature will significantly promote the gas desorption rate, and the goaf environment temperature is closely related to the exothermic oxidation of residual coal, and these are mutually influenced by factors such as air leakage intensity and void structure changes.

[0003] Currently, most research is limited to the short-term desorption characteristics of small coal particles under laboratory conditions, and only a short-term functional relationship between temperature and gas desorption volume has been established, lacking in-depth analysis of the coupling relationship among temperature, time, and desorption volume during the long-term unsteady desorption process; the influence of key parameters such as the thickness and particle size of residual coal in the goaf on the desorption rate has not been considered.

[0004] The method of extracting the protected coal seam to control the gas in the protected coal seam is one of the effective methods for preventing and controlling gas disasters at present. However, after the extraction of the protected coal seam, pressure relief changes occur in the overlying and underlying strata including the protected coal seam, resulting in more complex goaf conditions during the extraction of the protected coal seam, especially the development of coal and rock mass fractures, which affects the gas desorption change of residual coal in the goaf of the protected coal seam, making it more difficult to master the gas emission and migration changes in the protected coal seam. There is an urgent need for a method to accurately identify the gas desorption of residual coal in the goaf of the protected coal seam to efficiently guide the implementation of goaf gas control measures. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for desorbing gas from residual coal in the goaf of a protected coal seam to solve or alleviate the problems existing in the above-mentioned prior art.

[0006] To achieve the above purpose, this application provides the following technical solutions: This application provides a method for desorbing gas from residual coal in the goaf of a protected coal seam, including: according to the theoretical temperature of the goaf at the distance from the working face crosscut during the gas desorption process of residual coal in the goaf of the protected coal seam calculate the ideal gas desorption rate of the residual coal at the distance from the working face crosscut at the desorption time ; According to the measured values of the residual coal lump size, the measured value of the residual coal thickness, and the measured gas desorption rate at different distances from the working face crosscut, calculate the residual coal at the distance from the working face crosscut at the desorption time Desorption correction coefficient ; Input the ideal gas desorption rate and the desorption correction coefficient into the established gas desorption correction model to determine the corrected gas desorption rate of the residual coal at the distance from the working face cutting eye during the desorption time .

[0007] Preferably, based on the established first unsteady-state model, determine the theoretical temperature of the goaf at the distance from the working face cutting eye during the desorption process of the residual coal gas in the protected seam goaf; wherein, the first unsteady-state model characterizes the change of the theoretical temperature of the goaf with the desorption time of the residual coal gas at the distance from the working face cutting eye; Input the theoretical temperature of the goaf into the established second unsteady-state model to calculate the ideal gas desorption rate of the residual coal gas at the distance from the working face cutting eye during the desorption time ; wherein, the second unsteady-state model characterizes the change of the ideal gas desorption rate with the theoretical temperature of the goaf and the desorption time .

[0008] Preferably, the first unsteady-state model is:

[0009] In the formula, is the theoretical temperature of the goaf at the distance from the working face cutting eye during the desorption time in the coal particle adiabatic oxidation experiment, is the ambient temperature of the coal particle adiabatic oxidation experiment; is the mass of the coal sample of the residual coal in the goaf, is the specific heat capacity of the residual coal in the goaf; , are respectively different first exponential coefficients corresponding to the oxygen consumption rate in the coal particle adiabatic oxidation experiment, is the basic generation rate of carbon monoxide in the coal-oxygen reaction, is the maximum amount of carbon monoxide generated by chemical adsorption of coal under the condition of less than 100 °C, is the second exponential coefficient corresponding to the carbon monoxide generation rate in the coal particle adiabatic oxidation experiment; is the pressure and the temperature​ Standard heat of formation of carbon monoxide under the conditions is the difference between the heat of formation of carbon monoxide under pressure , the theoretical temperature of the gob conditions and the standard heat of formation . is the chemisorption heat of oxygen by the residual coal in the gob is the pressure , temperature conditions, the standard heat of formation of carbon dioxide is the difference between the heat of formation of carbon dioxide under pressure , the theoretical temperature of the gob conditions and the standard heat of formation . is the maximum value of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles is the growth coefficient of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles

[0010] Preferably, the second unsteady-state model is

[0011] wherein is the ideal gas desorption rate of the residual coal at the distance from the cutting hole of the working face at the desorption time ; are all different fitting parameters corresponding to the desorption time ; , , are respectively different third exponential coefficients corresponding to the fitting parameter ; , , are respectively different fourth exponential coefficients corresponding to the fitting parameter

[0012] Preferably, a distribution model of the vertical displacement of the gob is constructed to determine the predicted value of the vertical displacement of the residual coal at the distance from the cutting hole of the working face at the desorption time , and according to the measured values of the residual coal lump size and the measured gas desorption rate at different distances from the cutting hole of the working face, the predicted value of the vertical displacement is corrected to determine the first correction coefficient during the gas desorption process of the residual coal in the gob; According to the measured values of the residual coal thickness and the measured gas desorption rate at different distances from the cutting hole of the working face, the second correction coefficient during the gas desorption process of the residual coal in the gob is determined​

[0013] Preferably, in the gob data simulation model of the protected seam, a plurality of monitoring lines are arranged along the direction parallel to the cutting roadway starting from the cutting roadway of the working face to obtain the simulated vertical displacement values at different positions of the residual coal in the gob of the protected seam, so as to construct a distribution model of the vertical displacement in the gob and determine the residual coal at a distance from the cutting roadway of the working face at the desorption time ; According to the measured values of the residual coal lump size and the measured vertical displacement values at different distances from the cutting roadway of the working face, determine the displacement correction coefficient during the gas desorption process of the residual coal in the gob , so as to correct the predicted vertical displacement value of the residual coal at a distance from the cutting roadway of the working face at the desorption time .

[0014] Preferably, according to the formula:

[0015] Determine the desorption correction coefficient of the residual coal at the desorption time ; In the formula, is the first correction coefficient during the gas desorption process of the residual coal in the gob, is the second correction coefficient during the gas desorption process of the residual coal in the gob, is the displacement correction coefficient during the gas desorption process of the residual coal in the gob, is the predicted vertical displacement value of the residual coal at a distance from the cutting roadway of the working face at the desorption time , is the lump size influence factor during the gas desorption process of the residual coal in the gob, is the thickness influence factor during the gas desorption process of the residual coal in the gob, is the thickness of the residual coal

[0016] Preferably, according to the ideal gas desorption rate and the desorption correction coefficient , construct a non-steady state model of the corrected gas desorption rate with the theoretical temperature of the gob and the desorption time ; For the corrected gas desorption rate with the theoretical temperature of the gob and the desorption time The unsteady-state model is stabilized to obtain a modified gas desorption model.

[0017] Preferably, the modified gas desorption model is:

[0018]

[0019] In the formula, is the distance from the cutting hole of the working face where the gas desorbed from the residual coal at the desorption time is the modified gas desorption rate, is the desorption correction coefficient of the residual coal at the distance from the cutting hole of the working face at the desorption time ; are all different fitting parameters corresponding to the desorption time ; is the steady-state temperature of the gob area at the distance from the cutting hole of the working face; is the ambient temperature of the coal particle adiabatic oxidation experiment; is the mass of the coal sample of the residual coal in the gob area, is the specific heat capacity of the residual coal in the gob area; , are respectively different first exponential coefficients corresponding to the oxygen consumption rate in the coal particle adiabatic oxidation experiment, is the basic generation rate of carbon monoxide in the coal-oxygen reaction, is the maximum amount of carbon monoxide generated by chemical adsorption of coal under the condition of less than 100 °C, is the second exponential coefficient corresponding to the carbon monoxide generation rate in the coal particle adiabatic oxidation experiment; is the pressure , temperature condition, the standard heat of formation of carbon monoxide, is the difference between the heat of formation of carbon monoxide under the pressure , the theoretical temperature of the gob area condition and the standard heat of formation , is the chemisorption heat of oxygen by the residual coal in the gob area, is the pressure , temperature condition, the standard heat of formation of carbon dioxide, is the difference between the heat of formation of carbon dioxide under the pressure , the theoretical temperature of the gob area condition and the standard heat of formation , is the maximum value of the carbon dioxide concentration in the coal particle adiabatic oxidation experiment, is the growth coefficient of carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, is the advancing distance of the working face under coal mining conditions, is the average advancing speed under coal mining conditions.

[0020] The embodiment of the present application also provides a gas desorption system for the residual coal in the goaf of the protected seam, including: An ideal desorption unit configured to calculate the ideal gas desorption rate of the residual coal at the distance from the working face cut-through in the desorption time according to the theoretical temperature of the goaf at the distance from the working face cut-through during the gas desorption process of the residual coal in the goaf of the protected seam; of the goaf at the distance from the working face cut-through; from the working face cut-through, in the desorption time ; ; A correction coefficient determination unit configured to calculate the desorption correction coefficient of the residual coal at the distance from the working face cut-through in the desorption time t according to the measured value of the residual coal lump size, the measured value of the residual coal thickness and the measured gas desorption rate at different distances from the working face; from the working face cut-through, of the residual coal at the distance from the working face cut-through in the desorption time t; ; A desorption correction unit inputs the ideal gas desorption rate and the desorption correction coefficient into the constructed gas desorption correction model to determine the corrected gas desorption rate of the residual coal at the distance from the working face cut-through in the desorption time ; and the desorption correction coefficient from the working face cut-through, in the desorption time ; .

[0021] Beneficial effects: In the gas desorption method for the residual coal in the goaf of the protected seam provided by the embodiment of the present application, according to the theoretical temperature of the goaf at the distance from the working face cut-through during the gas desorption process of the residual coal in the goaf of the protected seam, the ideal gas desorption rate of the residual coal at the distance from the working face cut-through in the desorption time is calculated; at the same time, according to the measured value of the residual coal lump size, the measured value of the residual coal thickness and the measured gas desorption rate at different distances from the working face cut-through, the desorption correction coefficient of the residual coal at the distance from the working face cut-through in the desorption time is calculated; furthermore, the ideal gas desorption rate and the desorption correction coefficient are input into the constructed gas desorption correction model to determine the corrected gas desorption rate of the residual coal at the distance from the working face cut-through in the desorption time Corrected gas desorption rate , so as to effectively solve the problem that the coal particle desorption model under laboratory conditions cannot be directly applied to the field and it is difficult to accurately reflect the gas desorption law of large-size coal bodies, realize the accurate characterization of the gas desorption of the residual coal in the goaf, provide support for the multi-physical field coupling model of the gas-containing goaf and the prevention and control of spontaneous combustion disasters, and effectively improve the accuracy and reliability of the gas desorption analysis of the residual coal in the goaf. Description of the Drawings

[0022] The schematic drawings in the specification that form a part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. Among them: Figure 1 FIG. is a schematic flow chart of a method for gas desorption of residual coal in the goaf of a protected coal seam according to some embodiments of this application; Figure 2 FIG. is a schematic structural diagram of a coal particle adiabatic oxidation experimental system according to an embodiment of this application; Figure 3 FIG. is a schematic structural diagram of a gas adsorption and desorption experimental system according to an embodiment of this application; Figure 4 Schematic diagram of a data simulation model of the goaf of a protected coal seam according to an embodiment of this application; Figure 5 FIG. is a schematic diagram showing the change of the cumulative gas desorption amount of the residual coal in the goaf with the desorption time under different temperature conditions according to an embodiment of this application; Figure 6 is Figure 5 Schematic diagram showing the change of the cumulative gas desorption amount of the residual coal in the goaf with the desorption temperature in the same embodiment; Figure 7 FIG. is a schematic diagram showing the change of the gas desorption rate of the residual coal in the goaf with the desorption temperature at different desorption times according to an embodiment of this application; Figure 8 is the fitting parameter according to an embodiment of this application Schematic diagram showing the change with the desorption time; Figure 9 is the fitting parameter according to an embodiment of this application Schematic diagram showing the change with the desorption time; Figure 10 FIG. is a schematic diagram showing the change of the vertical displacement of the goaf at different distances from the intake airway according to an embodiment of this application; Figure 11 is the constant term according to an embodiment of this application Schematic diagram showing the change with the distance from the working face cutting eye; Figure 12The lumpiness coefficient provided according to an embodiment of the present application Schematic diagram of the variation with the distance from the working face cutting roadway Figure 13 The exponential factor provided according to an embodiment of the present application Schematic diagram of the variation with the distance from the working face cutting roadway Figure 14 Schematic diagram of the structure of a gob residual coal gas desorption system for a protected coal seam provided according to some embodiments of the present application Detailed implementation manners

[0023] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application rather than limiting the present application. In fact, those skilled in the art will clearly understand that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, features shown or described as part of one embodiment can be used in another embodiment to yield yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention shall fall within the scope of protection of the embodiments of the present invention

[0024] There are significant scale differences between laboratory coal particles and irregular coal blocks in the actual gob, resulting in the inability to directly apply the coal particle desorption model under laboratory conditions to the field, and it is difficult to accurately reflect the gas desorption law of large-size coal bodies. Based on this, the present application proposes a method for desorbing gas from residual coal in the gob of a protected coal seam, as Figures 1 to 13 shown, the method includes: Step S101, according to the theoretical temperature of the gob at the distance from the working face cutting roadway during the gas desorption process of the residual coal in the gob of the protected coal seam, calculate the ideal gas desorption rate of the residual coal at the distance from the working face cutting roadway at the desorption time .

[0025] In the present application, the coal-oxygen reaction during coal spontaneous combustion is simulated through a coal particle adiabatic oxidation experiment, and an unsteady-state model (i.e., the first unsteady-state model) between the theoretical temperature of the gob during the gas desorption process of the residual coal in the gob and the desorption time is constructed. The unsteady-state model characterizes the variation of the theoretical temperature of the gob during the gas desorption process of the residual coal in the gob with the desorption time of the gas in the residual coal at the distance from the working face cutting roadway , and according to the constructed first unsteady-state model, determine the theoretical temperature of the gob at the distance from the working face cutting roadway during the gas desorption process of the residual coal in the gob of the protected coal seam 。

[0026] Specifically, the residual coal in the gob is processed into coal sample particles with a weight of about 180 g per particle and an average particle size of 0.4 mm. Then, the coal sample particles are placed into a coal sample tank for the adiabatic oxidation experiment of coal particles. Based on the laboratory data obtained from the adiabatic oxidation experiment of coal particles, an oxygen concentration change model, a carbon monoxide concentration change model, and a carbon dioxide concentration change model for the coal-oxygen reaction are constructed. Among them, the oxygen concentration change model is as follows:

[0027] In the formula, is the desorption time in the adiabatic oxidation experiment of coal particles of the oxygen concentration, is the initial oxygen concentration in the adiabatic oxidation experiment of coal particles, are different oxygen consumption rate index coefficients (the first index coefficient) corresponding to the oxygen consumption rate in the adiabatic oxidation experiment of coal particles, and their values are all constants, which are obtained by fitting multiple sets of data of the oxygen consumption rate and desorption time obtained from the adiabatic oxidation experiment of coal particles.

[0028] The carbon monoxide concentration change model is as follows:

[0029] In the formula, is the desorption time in the adiabatic oxidation experiment of coal particles of the carbon monoxide concentration; is the basic generation rate of carbon monoxide in the coal-oxygen reaction, the maximum amount of carbon monoxide generated by the chemical adsorption of coal under the condition of less than 100 °C, is the carbon monoxide generation rate index coefficient (i.e., the second index coefficient) corresponding to the carbon monoxide generation rate in the adiabatic oxidation experiment of coal particles. Here, their values are all constants, which are obtained by fitting multiple sets of data of the carbon monoxide generation rate and desorption time obtained from the adiabatic oxidation experiment of coal particles.

[0030] The carbon dioxide concentration change model is as follows:

[0031] In the formula, is the desorption time in the adiabatic oxidation experiment of coal particles of the carbon dioxide concentration, is the maximum value of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, is the growth coefficient of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles; among them, The values are all constants, obtained by fitting multiple sets of data of the carbon dioxide generation rate and desorption time in the adiabatic oxidation experiment of coal particles.

[0032] During the adiabatic oxidation experiment of coal particles, the heat release intensity of the coal sample changes with the desorption time and is characterized by the heat release intensity model of the coal sample. Specifically, the heat release intensity model of the coal sample is:

[0033] In the formula, is the heat release intensity of the coal sample at the desorption time during the adiabatic oxidation experiment of coal particles; is the chemisorption heat of oxygen by the residual coal in the goaf, are the oxygen consumption rate, carbon monoxide generation rate, and carbon dioxide generation rate at the desorption time during the adiabatic oxidation experiment of coal particles respectively, is the pressure , temperature under the standard heat of formation of carbon monoxide, is the difference between the heat of formation and the standard heat of formation of carbon monoxide under the pressure , the theoretical temperature of the goaf ; is the standard heat of formation of carbon dioxide under the pressure , temperature ; is the difference between the heat of formation and the standard heat of formation of carbon dioxide under the pressure , the theoretical temperature of the goaf , . Among them, according to the formula: According to the formula: According to the formula:

[0034] to determine the oxygen consumption rate , carbon monoxide generation rate , and carbon dioxide generation rate at the desorption time .

[0035] Furthermore, there is a relationship between the heat release intensity and the released heat in the adiabatic oxidation experiment of coal particles, which is specifically as follows:

[0036] And the relationship between the released heat and the theoretical temperature of the goaf in the adiabatic oxidation experiment of coal particles is:

[0037] Combined with the relationship among the heat release intensity, heat quantity, and temperature in the adiabatic oxidation experiment of coal particles, the theoretical temperature of the gob area during the gas desorption process of residual coal in the gob area is generated. With the distance from the cutting line of the working face The desorption time of the residual coal gas at The first non-steady state model of the change is as follows:

[0038] In the formula, Is the theoretical temperature of the gob area at In the adiabatic oxidation experiment of coal particles at the distance from the cutting line of the working face during the desorption time , Is the environmental temperature of the adiabatic oxidation experiment of coal particles; Is the mass of the coal sample of the residual coal in the gob area, Is the specific heat capacity of the residual coal in the gob area; , Are respectively different first exponential coefficients (oxygen consumption rate exponential coefficients) corresponding to the oxygen consumption rate in the adiabatic oxidation experiment of coal particles, Is the basic generation rate of carbon monoxide in the coal-oxygen reaction, Is the maximum amount of carbon monoxide generated by chemical adsorption of coal under the condition of less than 100 °C, Is the carbon monoxide generation rate exponential coefficient (i.e., the second exponential coefficient) corresponding to the carbon monoxide generation rate in the adiabatic oxidation experiment of coal particles; Is the pressure , temperature The standard heat of formation of carbon monoxide under the conditions of, Is the difference between the heat of formation of carbon monoxide under the conditions of pressure , the theoretical temperature of the gob area And the standard heat of formation , Is the chemical adsorption heat of the residual coal in the gob area for oxygen, Is the pressure , temperature The standard heat of formation of carbon dioxide under the conditions of, Is the difference between the heat of formation of carbon dioxide under the conditions of pressure , the theoretical temperature of the gob area And the standard heat of formation , Is the maximum value of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, Is the growth coefficient of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles.

[0039] Then, the obtained theoretical temperature of the gob area In the second unsteady state model of the input construction, calculate the distance from the cutting hole of the working face where the gas desorbed from the residual coal at the time of desorption time is the ideal gas desorption rate . Among them, through the coal particle gas adsorption and desorption experiment, the gas desorption concentration data under different temperature conditions are obtained, and the coal particle gas desorption rate (ideal gas desorption rate ) and the theoretical temperature of the goaf , desorption time are used to obtain the unsteady function relationship (i.e., the second unsteady state model).

[0040] When simulating the gas desorption process of the residual coal in the goaf through the gas adsorption and desorption experiment, the obtained residual coal in the goaf is made into coal sample particles with a particle size of 2-100 mesh for the gas adsorption and desorption experiments of coal particles under different temperature conditions. After pretreatment, the coal sample particles are placed in the coal sample tank of the gas adsorption and desorption experiment device.

[0041] According to the gas desorption data obtained from the gas adsorption and desorption experiment, as the desorption time increases, the gas desorption rate conforms to the decreasing trend of the power function monotonically. The experimental data of the gas adsorption and desorption experiment are fitted to obtain the quantitative empirical model of the gas desorption rate of the residual coal (ideal gas desorption rate ) and temperature. Specifically, the second unsteady state model is as follows:

[0042] In the formula, is the ideal gas desorption rate of the residual coal at the distance of from the cutting hole of the working face at the desorption time ; are all different fitting parameters corresponding to the desorption time , and are obtained by fitting multiple groups of data of the gas desorption rate and desorption time obtained from the gas adsorption and desorption experiment; , , are respectively different third exponential coefficients corresponding to the fitting parameter ; , , are respectively different fourth exponential coefficients corresponding to the fitting parameter .

[0043] In a specific example, the adiabatic oxidation experimental system for coal particles includes: an air compressor, a data processor, a controller, a pressure pump, an intake mixing chamber, an outlet mixing chamber, a gas chromatograph analyzer, a preheating copper tube, a program temperature control box, a heat insulation layer, a carbon dioxide pressure reducer, an oxygen pressure reducer, a nitrogen pressure reducer, a pressure valve, a pressure stabilizing valve, a three-way valve, an adiabatic coal sample tank, a temperature probe, a fan, and a heater. During the experiment, first, load the coal sample into the coal sample tank, connect the intake pipe, the outlet pipe, and the temperature probe, and check the airtightness of the gas path.

[0044] Connect the nitrogen gas cylinder, and introduce nitrogen gas into the reactor at a flow rate of 0.05 g / min. Set the temperature control box to a constant temperature of 105°C, and use the nitrogen gas flow to dry the coal sample for 10 hours to eliminate the influence of external moisture; after drying, lower the temperature to the starting temperature of the experiment in 5 hours, and maintain nitrogen protection during the cooling process.

[0045] After the temperature of the coal sample stabilizes, weigh it to obtain the drying water loss; introduce dry air or oxygen with different concentrations, set the tracking heating temperature difference, ensure that the air environment temperature is lower than the coal sample temperature and rises according to the difference. This operation can not only ensure the adiabatic state of the coal sample but also preheat the intake gas, prevent the gas flow from taking away the heat of coal sample oxidation, and avoid the interference of the ambient temperature at the same time. During the experiment, record the change data of the oxygen, carbon monoxide, and carbon dioxide concentrations over time.

[0046] In another specific example, the gas adsorption and desorption experimental system for gas includes: a vacuum pump, a needle valve, a pressure valve, a gas cylinder, a digital acquisition unit, a coal sample tank, a reference tank, a controller, and an isothermal box. During the experiment, weigh 30 g of coal sample and place it in a drying oven in the pretreatment area, and place it under vacuum conditions at 105°C for 5 hours; inject helium gas into the coal sample tank and the reference tank, and check the airtightness of the device.

[0047] Each time, take 6.5 g from the dried coal sample and load it into the adsorption tank; set the initial gas desorption pressure value to 0.5 MPa, and set the temperatures of each group of experiments to 25°C, 30°C, 40°C, 50°C, 60°C, and 65°C respectively; automatically perform adsorption measurement until dynamic equilibrium is reached. Among them, the equilibrium pressure value in the coal sample tank is the initial gas desorption pressure value; operate the vacuum pump to extract the gas from the coal sample tank until the pressure reaches the atmospheric pressure of 0.1 MPa, then close the vacuum pump, and let the gas adsorbed by the coal sample desorb freely. When the pressure in the coal sample tank remains stable, the desorption is completed. At this time, the gas adsorption and desorption data within the total test time can be output.

[0048] Check whether the gas used in the experiment reaches the required concentration, and use nitrogen or carbon dioxide as the inert gas to prepare oxygen with volume fractions of 10%, 20%, and 30% respectively to test the process of coal-oxygen reaction under different oxygen concentration conditions in the experiment.

[0049] According to the experimental data, the gas desorption amount data within 150 minutes after the initial desorption conditions are extracted to calculate the gas desorption rate per unit mass per minute. Within 150 minutes of gas desorption, a total of 18 groups of experimental data are extracted and used to plot the curves of gas desorption rate versus time under different temperature conditions. The data selection method is as follows: within 1 - 10 minutes, the data interval is 1 minute, with a total of 10 groups of data; within 10 - 30 minutes, the data interval is 5 minutes, with a total of 4 groups of data; within 30 - 50 minutes, the data interval is 10 minutes, with a total of 2 groups of data; within 50 - 150 minutes, the data interval is 50 minutes, with a total of 2 groups of data; the above totals 18 groups of data. According to the data obtained from the gas adsorption and desorption experiments, the fitting parameters for different particle sizes are processed and . Specifically, as shown in Table 1: Table 1 Fitting Parameters and

[0050]

[0051] Then, the fitting parameters 、 versus the desorption time are fitted. The fitting results are as shown in Figure 9 . Different third exponential coefficients corresponding to the fitting parameter 、 、 are respectively determined, as well as different fourth exponential coefficients corresponding to the fitting parameter 、 、 .

[0052] Step S102: According to the measured values of the goaf residual coal lump size, the measured value of the residual coal thickness, and the measured gas desorption rate at different distances from the working face cutting eye, calculate the desorption correction coefficient of the residual coal at the distance from the working face cutting eye at the desorption time .

[0053] In this application, by constructing a numerical simulation model of the protective layer goaf, theoretical simulation data of the goaf residual coal thickness and the residual coal lump size are obtained, and a distribution function of the goaf residual coal lump size is constructed. Specifically, in the data simulation model of the protected layer goaf, multiple monitoring lines are arranged along the direction parallel to the cutting eye starting from the working face cutting eye, and the vertical displacement simulation values at different positions of the goaf residual coal in the protected layer are obtained, and a distribution model of the goaf vertical displacement is constructed.

[0054] Among them, in the numerical simulation model of the goaf in the protective layer, the upper part is the working face of the protective layer after mining, and the lower part is the working face of the protected layer being mined. In the numerical simulation model, the monitoring lines are arranged according to the goaf formed after coal seam mining. Specifically, the monitoring lines are arranged starting from the cutting hole of the working face. In the direction parallel to the cutting hole, several monitoring lines are arranged every 5 m; in the direction perpendicular to the cutting hole, several detection lines are arranged every 5 m; until the goaf is fully covered.

[0055] The vertical displacement simulation values at different positions obtained from the monitoring lines are used to construct the distribution model of the vertical displacement in the goaf. Specifically, the distribution model of the vertical displacement in the goaf is as follows:

[0056] In the formula, is the predicted vertical displacement value of the remaining coal at a distance from the cutting hole of the working face at the desorption time ; is the distance between the monitoring line and the cutting hole of the working face; is the distance between the monitoring line and the intake airway; is the lumpiness coefficient of the remaining coal at a distance from the cutting hole of the working face, is the cutting hole of the working face at a distance the predicted vertical displacement value of the exponential factor; is the cutting hole of the working face at a distance the predicted vertical displacement value of the constant term; are respectively the fitting coefficients corresponding to the lumpiness coefficient ; are respectively the fitting coefficients corresponding to the key parameters ; are respectively the key parameters corresponding to the constant term ;

[0057] In a specific example, a data simulation model of the goaf in the protected layer is constructed. The upper part is the working face of the protective layer after mining, and the lower part is the working face of the protected layer being mined. Monitoring lines are arranged for the goaf formed after the coal seam mining of the working face of the protected layer. Among them, the monitoring lines are arranged starting from the cutting hole of the working face. In the direction parallel to the cutting hole, several monitoring lines are arranged every 5 m.

[0058] According to the simulation data obtained from the vertical displacement simulation of the goaf, a result graph of the vertical displacement in the goaf is drawn. A total of 12 groups of experimental data are extracted to draw the curves of the vertical displacement in the goaf and the distances from the intake airway and the cutting hole of the working face. According to the data obtained from the numerical simulation, the parameters of different particle sizes in the coal mine are processed as shown in Table 2 specifically: Table 2

[0059] Furthermore, according to the results in Table 2, the curves of the key parameters changing with the distance between the detection line and the cutting roadway of the working face are respectively plotted and fitted, and the fitting coefficients corresponding to the key parameters are obtained; the fitting coefficients corresponding to the key parameters are obtained; the fitting coefficients corresponding to the key parameters .

[0060] While constructing the distribution model of the vertical displacement in the goaf, according to the measured values of the coal block size and the vertical displacement of the goaf at different distances from the cutting roadway of the working face, multiple groups of data of the measured values of the coal block size and the vertical displacement of the goaf are fitted to obtain the displacement correction coefficient in the process of gas desorption of the goaf coal, and the vertical displacement prediction value of the coal left in the goaf at a distance from the cutting roadway of the working face at the desorption time is corrected through the displacement correction coefficient to determine the first correction coefficient in the process of gas desorption of the goaf coal. Specifically, according to the formula:

[0061] the first correction coefficient in the process of gas desorption of the goaf coal is determined; where is the block size influence factor in the process of gas desorption of the goaf coal, which is specifically obtained by fitting the coal left in the goaf with different block sizes and the corresponding gas desorption rates obtained from on-site surveys of the goaf, and the influence factor of the coal block size on the gas desorption of the goaf coal in the process of gas desorption of the goaf coal is obtained.

[0062] At the same time, according to the measured values of the thickness of the coal left in the goaf and the measured gas desorption rate at different distances from the cutting roadway of the working face, the second correction coefficient in the process of gas desorption of the goaf coal is determined. Specifically, according to the formula:

[0063] the second correction coefficient in the process of gas desorption of the goaf coal is determined; where is the thickness of the coal left in the goaf at a distance from the cutting roadway of the working face, is the thickness influence factor during the gas desorption process of residual coal in the gob area. Specifically, it is obtained by fitting the residual coal with different thicknesses obtained from on-site surveys of the gob area and the corresponding gas desorption rates, and the influence factor of the residual coal thickness on the gas desorption of residual coal during the gas desorption process in the gob area is obtained. 。

[0064] Finally, multiply the first correction coefficient during the gas desorption process of residual coal in the gob area by the second correction coefficient during the gas desorption process of residual coal in the gob area to obtain the desorption correction coefficient at the distance from the working face cutting eye at the desorption time 。That is, the desorption correction coefficient 。

[0065] Step S103: Input the ideal gas desorption rate and the desorption correction coefficient into the constructed gas desorption correction model to determine the corrected gas desorption rate of the residual coal at the distance from the working face cutting eye at the desorption time 。

[0066] In this application, a non-steady state model of the gas desorption rate of residual coal in the gob area with respect to the gob area temperature and the desorption time is established:

[0067] where

[0068] Obtain the non-steady state model of the gas desorption rate of the residual coal in the gob area with respect to the gob area temperature and the desorption time :

[0069] Here, by performing a steady-state treatment on the non-steady state model of the gas desorption rate of the residual coal in the gob area with respect to the gob area temperature and the desorption time , a quantitative model of the gas desorption rate of residual coal in the gob area with respect to temperature is established. Specifically, convert the desorption time into the ratio of the working face advance distance to the average advance speed to complete the gas desorption rate of the residual coal in the gob area with respect to the gob area temperature and the desorption time Steady-state processing is carried out on the unsteady-state model.

[0070] That is, through the formula:

[0071] For the formula:

[0072] Steady-state processing is carried out to obtain the gas desorption rate of the residual coal in the gob and the steady-state model of the theoretical temperature of the gob (i.e., the gas desorption correction model):

[0073]

[0074] In the formula, is the corrected gas desorption rate of the residual coal gas at the distance from the cutting hole of the working face at the desorption time , is the desorption correction coefficient of the residual coal at the distance from the cutting hole of the working face at the desorption time ; is the steady-state temperature of the gob at the distance from the cutting hole of the working face; is the environmental temperature of the coal particle adiabatic oxidation experiment; is the mass of the coal sample of the residual coal in the gob, is the specific heat capacity of the residual coal in the gob; , are respectively different first exponential coefficients corresponding to the oxygen consumption rate in the coal particle adiabatic oxidation experiment, is the basic generation rate of carbon monoxide in the coal-oxygen reaction, is the maximum amount of carbon monoxide generated by chemical adsorption of coal under the condition of less than 100 °C, is the carbon monoxide generation rate exponential coefficient (i.e., the second exponential coefficient) corresponding to the carbon monoxide generation rate in the coal particle adiabatic oxidation experiment; is the pressure , temperature conditions, the standard heat of formation of carbon monoxide, is the difference between the heat of formation of carbon monoxide under the pressure , the theoretical temperature of the gob conditions and the standard heat of formation , is the chemical adsorption heat of the residual coal in the gob to oxygen, is the pressure , temperature Standard heat of formation of carbon dioxide under conditions, is the difference between the heat of formation of carbon dioxide under the pressure and the theoretical temperature of the gob area and the standard heat of formation ; is the maximum value of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, is the growth coefficient of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, is the advancing distance of the working face under coal mining conditions, is the average advancing speed under coal mining conditions.

[0075] Therefore, by constructing a non-steady state model of the corrected gas desorption rate of the residual coal in the gob area and the theoretical temperature of the gob area , desorption time , and performing a steady-state treatment on the constructed non-steady state model of the corrected gas desorption rate , a steady-state model of the gas desorption rate of the residual coal in the gob area and the gob area temperature is established to evaluate the external wire desorption rate of the residual coal in the gob area under coal mining conditions, making it more in line with the actual conditions of coal mine mining, better reflecting the gas desorption law of the residual coal in the gob area, and providing theoretical support for the coupling law of the gas of the residual coal in the gob area and the multi-physical fields of spontaneous combustion.

[0076] The embodiment of the present application also provides a gas desorption system for the residual coal in the gob area of the protected seam, as Figure 14 shown, the system includes: Ideal desorption unit 1401, configured to calculate the ideal gas desorption rate of the residual coal at the distance from the working face cutting eye during the gas desorption process of the residual coal in the gob area of the protected seam according to the theoretical temperature of the gob area at the distance from the working face cutting eye at the desorption time ; Correction coefficient determination unit 1402, configured to calculate the desorption correction coefficient of the residual coal at the distance from the working face cutting eye at the desorption time t according to the measured values of the residual coal block size, the measured value of the residual coal thickness, and the measured gas desorption rate at different distances from the working face; Desorption correction unit 1403, inputs the ideal gas desorption rate and the desorption correction coefficient into the constructed gas desorption correction model to determine the residual coal at the distance from the working face cutting eye at the desorption time Corrected gas desorption rate .

[0077] The gob residual coal gas desorption system of the protected coal seam provided by the embodiments of the present application can implement the steps and processes of the gob residual coal gas desorption method of any one of the above embodiments and achieve the same technical effects, which will not be elaborated herein one by one.

[0078] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0079] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0080] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for desorbing gas from residual coal in a mined-out area of a protected layer, characterized in that, Including: According to the distance from the gob goaf coal gas desorption process in the protected layer to the working face cutting The theoretical temperature of the gob area at the place , calculate the distance from the working face cutting The ideal gas desorption rate of the gob coal at the place during the desorption time ; ; According to the measured values of the size of residual coal blocks, the measured thickness of residual coal, and the measured gas desorption rate at different distances from the cutting roadway of the working face , calculate the distance from the cutting roadway of the working face The desorption correction coefficient of the residual coal at the time of desorption ; ; Input the ideal gas desorption rate and the desorption correction coefficient into the established gas desorption correction model to determine the corrected gas desorption rate of the residual coal at the distance from the working face cutting roadway at the desorption time . .

2. The method according to claim 1, characterized in that Based on the constructed first unsteady state model, determine the theoretical temperature of the goaf at the distance from the working face cutting hole during the gas desorption process of the residual coal in the goaf of the protected seam ; wherein, the first unsteady state model characterizes the theoretical temperature of the goaf varying with the desorption time of the residual coal gas at the distance from the working face cutting hole ; ​ Input the theoretical temperature of the gob area into the constructed second unsteady-state model to calculate the ideal gas desorption rate of the residual coal gas at the distance from the cutting hole of the working face at the desorption time ; where the second unsteady-state model characterizes the change of the ideal gas desorption rate with the theoretical temperature of the gob area and the desorption time .

3. The method according to claim 2, wherein The first non-steady state model is: ； In the formula, is the theoretical temperature of the gob at the desorption time at a distance of from the cutting roadway of the working face in the adiabatic oxidation experiment of coal particles, is the ambient temperature of the adiabatic oxidation experiment of coal particles; is the mass of the coal sample of the residual coal in the gob, is the specific heat capacity of the residual coal in the gob; , are respectively different first exponential coefficients corresponding to the oxygen consumption rate in the adiabatic oxidation experiment of coal particles, is the basic generation rate of carbon monoxide during the coal-oxygen reaction, is the maximum amount of carbon monoxide generated by chemical adsorption of coal under the condition of less than 100 °C, is the second exponential coefficient corresponding to the carbon monoxide generation rate in the adiabatic oxidation experiment of coal particles; is the pressure , temperature under the conditions of , the standard heat of formation of carbon monoxide, , the difference between the heat of formation of carbon monoxide under the conditions of pressure and the theoretical temperature of the gob and the standard heat of formation is the chemical adsorption heat of the residual coal in the gob for oxygen, is the pressure , temperature under the conditions of , the standard heat of formation of carbon dioxide, , the difference between the heat of formation of carbon dioxide under the conditions of pressure and the theoretical temperature of the gob and the standard heat of formation is the maximum value of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, is the growth coefficient of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles.

4. The method according to claim 2, wherein The second non-steady state model is: ； In the formula, is the ideal gas desorption rate of the residual coal at the distance from the cutting hole of the working face at the desorption time ; are all different fitting parameters corresponding to the desorption time ; , , are different third exponential coefficients corresponding to the fitting parameter respectively; , , are different fourth exponential coefficients corresponding to the fitting parameter respectively.

5. The method according to claim 1, characterized in that Build a distribution model of the vertical displacement in the gob area to determine the predicted value of the vertical displacement of the residual coal at the distance from the cutting hole of the working face at the desorption time . And based on the measured values of the residual coal lump size and the measured gas desorption rate at different distances from the cutting hole of the working face, correct the predicted value of the vertical displacement to determine the first correction coefficient during the gas desorption process of the residual coal in the gob area ; Determine the second correction coefficient during the gas desorption process of the residual coal in the goaf according to the measured values of the residual coal thickness and the measured gas desorption rate at different distances from the cutting roadway of the working face .

6. The method according to claim 5, characterized in that In the gob data simulation model of the protected seam, multiple monitoring lines are arranged parallel to the cutting roadway starting from the cutting roadway of the working face to obtain the simulated vertical displacement values at different positions of the residual coal in the gob of the protected seam, so as to construct the distribution model of the vertical displacement in the gob and determine the vertical displacement prediction value of the residual coal at the position at the desorption time of the residual coal ; Determine the displacement correction coefficient during the gas desorption process of the residual coal in the goaf according to the measured values of the lump size and vertical displacement of the residual coal in the goaf at different distances from the cutting roadway of the working face , so as to correct the predicted value of the vertical displacement of the residual coal at the distance of from the cutting roadway of the working face at the desorption time . ​ 7. The method according to claim 5, characterized in that According to the formula: ； Determine the distance from the cutting roadway of the working face The desorbed coal left at The desorption correction coefficient at the desorption time ; In the formula, is the first correction coefficient in the gas desorption process of residual coal in the gob, is the second correction coefficient in the gas desorption process of residual coal in the gob, is the displacement correction coefficient in the gas desorption process of residual coal in the gob, is the distance from the cutting hole of the working face The predicted value of the vertical displacement of the residual coal at the time of the desorption time is is the particle size influence factor in the gas desorption process of residual coal in the gob, is the thickness influence factor in the gas desorption process of residual coal in the gob, is the distance from the cutting hole of the working face The thickness of the residual coal at the place is 8. The method according to claim 1, characterized in that According to the ideal gas desorption rate and the desorption correction coefficient , a non-steady state model of the corrected gas desorption rate is constructed with the theoretical temperature of the gob , the desorption time ; For the corrected gas desorption rate and the theoretical temperature of the goaf , desorption time The unsteady model is stabilized to obtain a corrected gas desorption model.

9. The method according to claim 8, wherein The gas desorption correction model is: ； ； In the formula, is the distance from the gob cut along the working face where the gas desorbed from the residual coal at the desorption time is the corrected gas desorption rate; is the distance from the gob cut along the working face where the desorption correction coefficient of the residual coal at the desorption time is; are all different fitting parameters corresponding to the desorption time respectively; is the steady-state temperature of the gob area at a distance from the cutting roadway of the working face ; is the environmental temperature of the adiabatic oxidation experiment of coal particles; is the mass of the coal sample of the residual coal in the gob area, is the specific heat capacity of the residual coal in the gob area; , are respectively different first exponential coefficients corresponding to the oxygen consumption rate in the adiabatic oxidation experiment of coal particles, is the basic generation rate of carbon monoxide in the coal-oxygen reaction, is the maximum amount of carbon monoxide generated by chemical adsorption of coal at temperatures below 100 °C, is the second exponential coefficient corresponding to the carbon monoxide generation rate in the adiabatic oxidation experiment of coal particles; is the pressure , temperature conditions, the standard heat of formation of carbon monoxide, is the heat of formation of carbon monoxide at pressure , the theoretical temperature of the gob area conditions and the difference between the heat of formation and the standard heat of formation ; is the chemisorption heat of the residual coal in the gob area for oxygen, is the pressure , temperature conditions, the standard heat of formation of carbon dioxide, is the heat of formation of carbon dioxide at pressure , the theoretical temperature of the gob area conditions and the difference between the heat of formation and the standard heat of formation ; is the maximum value of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, is the growth coefficient of the carbon dioxide concentration in the adiabatic oxidation experiment of coal particles, is the advancing distance of the working face under coal mining conditions, is the average advancing speed under coal mining conditions.

10. A gob coal gas desorption system with a protected layer, characterized in that, Including: An ideal desorption unit configured to calculate the ideal gas desorption rate of the residual coal at a distance from the working face cutting hole at the theoretical temperature of the goaf during the gas desorption process of the residual coal in the goaf of the protected seam, according to the distance from the working face cutting hole at the desorption time ; ; A correction coefficient determination unit configured to calculate a desorption correction coefficient of the residual coal at a distance from the gob cut at the desorption time t according to the measured values of the residual coal lump size, the measured residual coal thickness, and the measured gas desorption rate at different distances from the working face , at a distance from the working face where the residual coal is located ; Desorption correction unit, ideal gas desorption rate and desorption correction coefficient are input into the constructed gas desorption correction model to determine the distance from the working face cutting The corrected gas desorption rate of the remaining coal at the place at the desorption time .

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