Temperature monitoring system for a working face goaf

Abstract

The application discloses a temperature monitoring system for a working face goaf, and solves the technical problem that the prior art is blind in preventing spontaneous combustion, cannot effectively prevent or delay the occurrence of spontaneous combustion in the working face goaf, and seriously affects safe and efficient production of the working face; the application acquires temperature data of the goaf through a distributed temperature measurement optical fiber, obtains a temperature distribution diagram according to the temperature data, divides the temperature distribution diagram into a plurality of sub-regions, can monitor, early warn and prevent different sub-regions, can effectively monitor the spontaneous combustion phenomenon in the goaf, and reduces the prevention and treatment cost; the application can divide the goaf into a plurality of sub-regions through the temperature distribution diagram, or can divide the goaf into a plurality of sub-regions in combination with index gas related data acquired by a beam tube device, can accurately assess the danger level of the sub-regions, and provides a basis for targeted prevention and treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mine safety intelligent detection, and particularly relates to a temperature monitoring system for a goaf of a working face. BACKGROUND

[0002] Spontaneous combustion is the focus of mine fire prevention and control, and most spontaneous combustion occurs in goafs. With the increase of the depth of coal mining, the area of the goaf is continuously increased, and the thickness of the residual coal in the goaf is continuously increased, which leads to frequent coal seam spontaneous combustion accidents in the goaf, and huge economic losses.

[0003] The comprehensive prevention and control measures for spontaneous combustion in the prior art, such as pressure equalization, injection of resistance agents, grouting, and inerting, all play a certain role in inhibiting coal spontaneous combustion; the prior art is blind and often costs a lot, and cannot effectively prevent or delay the occurrence of spontaneous combustion in the goaf of the working face, which seriously affects the safe and efficient production of the working face; therefore, a temperature monitoring system for the goaf of the working face is urgently needed. SUMMARY

[0004] The application aims to at least solve one of the technical problems in the prior art; for this purpose, the application provides a temperature monitoring system for the goaf of the working face, which is used to solve the technical problem that the prior art is blind, has high cost, cannot effectively prevent or delay the occurrence of spontaneous combustion in the goaf of the working face, and seriously affects the safe and efficient production of the working face when preventing and controlling spontaneous combustion.

[0005] The application collects temperature data of the goaf through the distributed temperature measurement optical fiber, obtains a temperature distribution map according to the temperature data, divides the temperature distribution map into a plurality of sub-regions, can monitor, warn and prevent different sub-regions, can effectively monitor the spontaneous combustion phenomenon in the goaf, and reduces the cost.

[0006] To achieve the above purpose, the first aspect of the application provides a temperature monitoring system for the goaf of the working face, which comprises a fiber temperature measurement host, a distributed temperature measurement optical fiber, a switch and an industrial computer, and the industrial computer and the fiber temperature measurement host are connected through the switch.

[0007] The fiber temperature measurement host is connected with the distributed temperature measurement substation through the transmission optical fiber, and the distributed temperature measurement substation collects temperature data of the goaf through the distributed temperature measurement optical fiber.

[0008] A temperature distribution map of the goaf is rendered and generated according to the temperature data; wherein the temperature distribution map is updated in real time or at a fixed time.

[0009] The temperature distribution map is regionally divided to obtain a plurality of sub-regions.

[0010] According to the temperature conditions of the sub-regions, the workers are warned, and prevention and treatment are performed based on the temperature conditions of the sub-regions.

[0011] Preferably, a temperature distribution map is obtained according to the temperature data, including:

[0012] The temperature data is obtained by the distributed temperature measurement optical fiber.

[0013] The temperature distribution map of the goaf is obtained by combining the fluid mechanics software and the temperature data.

[0014] Preferably, a plurality of sub-regions are obtained according to the temperature distribution map, including:

[0015] A temperature threshold is obtained; wherein the temperature threshold is used to distinguish the danger degree of the temperature of the goaf, including a second threshold and a third threshold, and the second threshold is less than the third threshold.

[0016] Data points with a temperature value less than the second threshold in the temperature distribution map are obtained, and are marked as first position points; and a region composed of the first position points is marked as a first region.

[0017] Position points with a temperature value greater than or equal to the third threshold in the temperature distribution map are obtained, and are marked as third position points; and a region composed of the third position points is marked as a third region.

[0018] Regions other than the first region and the third region in the goaf are marked as a second region.

[0019] Preferably, a plurality of sub-regions are obtained by combining the temperature distribution map and beam tube data, including:

[0020] The concentration of an index gas in the beam tube data is extracted; wherein the index gas includes carbon monoxide and methane.

[0021] When the concentration of the index gas exceeds a corresponding threshold, temperature data around a detection point corresponding to the index gas is obtained.

[0022] A region composed of position points with temperature data greater than or equal to the second threshold is marked as a danger region.

[0023] Preferably, the beam tube data is the concentration of a gas component of a detection point in the goaf, and the beam tube data is obtained by a beam tube detection device.

[0024] Preferably, the beam tube detection device includes an air suction pump, a control cabinet and a multi-core beam tube; wherein the multi-core beam tube is a mine-used antistatic flame-retardant polyethylene beam tube.

[0025] Preferably, based on the data obtained by the optical fiber temperature measuring host, the distributed temperature measurement optical fiber, the switch and the industrial computer, a goaf spontaneous combustion mathematical model is established in combination with a pressure field and an oxygen concentration field in the goaf;

[0026] The goaf spontaneous combustion mathematical model is:

[0027]

[0028] Boundary conditions are:

[0029]

[0030] Wherein, K is a permeability coefficient of the porous medium, and the unit is m / s; p g is a gas density in the control body, and the unit is kg / m 3 ; g is a gravitational acceleration, and the unit is m / s 2 ; P is a sum of static pressure and velocity pressure, and the unit is Pa; a is a dip angle of the coal seam, and the unit is degrees; n is a porosity of the float coal in the goaf, and the unit is %; K O2 is a diffusion coefficient constant of oxygen; C O2 is a molar concentration of oxygen, and the unit is mol / m 3 ; T g is a gas temperature, and the unit is K; T s is a coal rock temperature, and the unit is K; p s is a density of the coal rock, and the unit is kg / m 3 ; C s is a specific heat capacity of the coal rock KJ / (kg·K); p s is a density of the solid particles, and the unit is kg / m 3 ; l g is a gas thermal conductivity coefficient, and the unit is W / m·℃; p g is a density of the goaf gas, and the unit is kg / m 3 ; C g is a specific heat capacity of the gas KJ / (kg·℃); u (t) is an oxygen consumption per unit volume per unit time, and the unit is mol / (s·m 3 ); l s is a thermal conductivity coefficient of the goaf caved coal rock, and the unit is W / m·℃; q (t) is a heat release of the residual coal in the control body per unit time, and the unit is kJ / (mol·s); K e is a convective heat transfer coefficient of the coal rock and the gas, and the unit is J / (m 2 ·s·K);

[0031] The solution method of the goaf spontaneous combustion mathematical model comprises the following steps: determining the solution range of the model, dividing the calculation region into grids, discretizing the model and its boundary conditions according to the finite volume method to obtain node equation groups of pressure, oxygen concentration and temperature, and finally coupling and solving the node equation groups by a computer program.

[0032] Preferably, the solution method of the goaf spontaneous combustion mathematical model specifically comprises the following steps:

[0033] S1, defining constants, variables and arrays;

[0034] S2, inputting basic parameters;

[0035] S3, profiling the goaf network;

[0036] S4, node correlation matrix;

[0037] S5, node array initialization;

[0038] S6, assigning values to the coefficient matrix of each field;

[0039] S7, iterative calculation;

[0040] S8, assigning iteration initial values to variables in each field;

[0041] S9, correcting the pressure coefficient matrix by density;

[0042] S10, calling a subroutine to solve the pressure field;

[0043] S11, taking the maximum value of pressure change and saving it;

[0044] S12, obtaining velocity components from pressure;

[0045] S13, modifying the oxygen concentration coefficient matrix by velocity and temperature;

[0046] S14, calling a subroutine to solve the oxygen concentration field;

[0047] S15, taking the maximum value of oxygen concentration change and saving it;

[0048] S16, modifying the temperature coefficient matrix by velocity and oxygen concentration;

[0049] S17, calling a subroutine to solve the temperature field;

[0050] S18, taking the maximum value of temperature field change and saving it;

[0051] S19, comparing the maximum values of changes in the three fields;

[0052] S20, taking the maximum value of the three;

[0053] S21, judge whether the precision is reached, yes to S22, otherwise return to S7;

[0054] S22, save the calculation result;

[0055] S23, output the distribution diagram of pressure, speed, oxygen concentration and temperature.

[0056] S24, post-processing software display;

[0057] S25, output the distribution diagram of pressure, speed, oxygen concentration and temperature.

[0058] Preferably, one said optical fiber temperature measuring host is configured with one said distributed temperature measuring substation, or

[0059] One said optical fiber temperature measuring host is configured with N said distributed temperature measuring substations; wherein, N is an integer greater than 1.

[0060] Preferably, a distributed temperature measuring optical fiber is laid in the machine lane of the goaf, and a plurality of distributed temperature measuring optical fibers are uniformly laid in the air lane of the goaf; wherein, the optical fiber temperature measuring optical fiber buried in the goaf is protected by a screen pipe, and the optical fiber temperature measuring optical fiber at the upper and lower corners of the goaf is protected by a high-pressure oil pipe.

[0061] Compared with the prior art, the beneficial effects of the present application are:

[0062] 1、The present application can effectively monitor the spontaneous combustion phenomenon of the goaf, and reduce the prevention and control cost.

[0063] 2、The present application can divide the goaf into several sub-regions according to the temperature distribution diagram, and can also divide the goaf into several sub-regions according to the index gas related data obtained by the beam tube device, which can accurately evaluate the risk level of the sub-region and provide a basis for targeted prevention and control.

[0064] 3、The present application can establish a goaf spontaneous combustion mathematical model by combining the temperature detection result with the pressure field and oxygen concentration field in the goaf, and obtain the spontaneous combustion result of the goaf by solving the three fields, wherein the collected temperature data of the goaf provides accurate temperature data for the model, so that the spontaneous combustion simulation result and prediction result of the goaf can be accurately obtained. BRIEF DESCRIPTION OF DRAWINGS

[0065] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only represent some of the embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0066] Figure 1 Schematic diagram of working steps of the present application;

[0067] Figure 2 Schematic diagram of distribution of caving zone, fracture zone and bending subsidence zone;

[0068] Figure 3 Schematic diagram of position of abutment pressure zone;

[0069] Figure 4 Schematic diagram of abutment pressure before and after the working face;

[0070] Figure 5 Schematic diagram of stress distribution and stress shell shape of surrounding rock along the strike;

[0071] Figure 6 Schematic diagram of stress distribution and stress shell shape of surrounding rock along the dip;

[0072] Figure 7 Schematic diagram of moving coordinate and coal and rock temperature field boundary of goaf;

[0073] Figure 8 Schematic diagram of spontaneous combustion boundary condition of goaf;

[0074] Figure 9 Flowchart of solution method of mathematical model of spontaneous combustion of goaf. DETAILED DESCRIPTION

[0075] The technical solutions of the present application will be described clearly and completely in combination with the embodiments. Obviously, the described embodiments only represent some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0076] Spontaneous combustion is the key point of mine fire prevention and control work, and most of the spontaneous combustion occurs in goaf. With the increase of the depth of coal mining, the area of goaf is continuously increased, and the thickness of the residual coal in goaf is continuously increased, which leads to frequent coal seam spontaneous combustion accidents in goaf, and huge economic losses.

[0077] The comprehensive prevention and control measures for spontaneous combustion in the prior art, such as pressure equalization, injection of resistance agents, grouting, and inerting, have played a certain role in inhibiting coal spontaneous combustion; the prior art is blind and often consumes huge costs, and cannot effectively prevent or delay the occurrence of spontaneous combustion in the goaf of the working face, seriously affecting the safe and efficient production of the working face.

[0078] The application can effectively monitor the spontaneous combustion phenomenon in the goaf, and reduce the prevention and control cost.

[0079] Please refer to Figure 1 The first aspect embodiment of the application provides a temperature monitoring system for a goaf of a working face, comprising a fiber temperature measurement host, a distributed temperature measurement fiber, a switch and an industrial computer, and the industrial computer and the fiber temperature measurement host are connected through the switch;

[0080] The fiber temperature measurement host is connected with the distributed temperature measurement station through a transmission optical fiber, and the distributed temperature measurement station collects temperature data of the goaf through the distributed temperature measurement fiber;

[0081] The temperature distribution map of the goaf is rendered and generated according to the temperature data;

[0082] The temperature distribution map is regionally divided to obtain a plurality of sub-regions;

[0083] The staff is warned according to the temperature conditions of the plurality of sub-regions, and prevention and control are carried out based on the temperature conditions of the plurality of sub-regions.

[0084] The main purpose of the application is to render the collected temperature data to obtain the temperature distribution map of the goaf, and to monitor, warn and prevent the regions with different dangerous degrees in the temperature distribution map, so as to achieve the purpose of the application.

[0085] The fiber temperature measurement host and the distributed temperature measurement station in the application can be configured in the form of "1+1", that is, one fiber temperature measurement host is connected with one distributed temperature measurement station, and the two are connected through a professional communication ring network or a special communication optical fiber to realize remote real-time collection, display, storage and distribution of temperature data.

[0086] The fiber temperature measurement host and the distributed temperature measurement station in the application can also be configured in the form of "1+N", that is, one fiber temperature measurement host is connected with a plurality of distributed temperature measurement stations, and the configuration is flexible and can be determined according to the actual situation.

[0087] In one embodiment, the temperature distribution map is obtained according to the temperature data, comprising:

[0088] Obtaining temperature data through the distributed temperature measurement optical fiber;

[0089] Combining the fluid mechanics software and the temperature data to obtain the temperature distribution map of the goaf.

[0090] In the present application, the optical fiber temperature measurement host or the distributed temperature measurement substation obtains the temperature data of the goaf through the distributed optical fiber, and then uses the fluid mechanics software (such as CFD) to simulate the temperature data and the position of the distributed temperature measurement optical fiber, so as to obtain the temperature distribution map of the goaf.

[0091] In an optional embodiment, a plurality of sub-regions are obtained according to the temperature distribution map, including:

[0092] Obtaining a temperature threshold value;

[0093] Obtaining data points with a temperature value less than a second threshold value in the temperature distribution map, marking the data points as first position points, and marking a region composed of the first position points as a first region;

[0094] Obtaining position points with a temperature value greater than or equal to a third threshold value in the temperature distribution map, marking the position points as third position points, and marking a region composed of the third position points as a third region;

[0095] Marking a region other than the first region and the third region in the goaf as a second region.

[0096] The temperature threshold value in the present embodiment is obtained according to actual experience or research analysis, and the temperature threshold value is used to distinguish the danger degree of the temperature of the goaf, including the second threshold value and the third threshold value, and the second threshold value is less than the third threshold value; the goaf is divided into three regions through the second threshold value and the third threshold value, the position points corresponding to the temperature less than the second threshold value are the first region, the position points corresponding to the temperature greater than or equal to the second threshold value and less than the third threshold value are the second region, and the position points corresponding to the temperature greater than or equal to the third threshold value are the third region.

[0097] It can be understood that the danger degree of the first region, the second region and the third region increases in turn.

[0098] The present embodiment divides the simulated temperature distribution map, and different prevention and control measures can be used according to the type of the division result, and the specific prevention and control measures can be any one of the existing technologies, and the staff can make different prevention and control measures according to the temperature of each sub-region.

[0099] In an optional embodiment, a plurality of sub-regions are obtained by combining the temperature distribution map and the beam tube data, including:

[0100] Extracting the concentration of the index gas in the beam tube data;

[0101] When the concentration of the index gas exceeds the corresponding threshold value, temperature data around the detection point of the index gas is acquired;

[0102] An area composed of position points with temperature data greater than or equal to the second threshold value is marked as a dangerous area.

[0103] In the embodiment, the index gas includes carbon monoxide and methane, and the beam tube device is used to acquire the index gas, analyze the index gas first, and then divide the goaf in combination with the temperature area.

[0104] The main purpose of the embodiment is to divide the danger degree of the goaf by two indexes, i.e., the index gas and the temperature threshold value, and mark the area as a dangerous area when both indexes meet the corresponding threshold value requirements.

[0105] Although the beam tube has problems such as gas leakage, positioning failure, and low accuracy, it is still an important means for monitoring the spontaneous combustion of the goaf and the index gas, and can complement the optical fiber temperature measurement system. The beam tube monitoring is a complete set of devices for remotely extracting gas samples from monitoring sites by using an air pump and a plastic pipe cable with multiple cores, automatically analyzing the samples by using a special gas chromatograph, and determining the gas component concentration of each monitoring point in real time. When the concentration of the index gas exceeds the threshold value, the device can issue an alarm.

[0106] The application can warn the staff according to the temperature conditions of the sub-areas. The warning method can be a threshold warning method in the prior art, specifically, when the temperature value in a certain sub-area reaches a preset alarm threshold value, the information is fed back to the staff in time, such as alarm by a buzzer, flash screen display by a display screen, etc. The application can also prevent and treat based on the temperature conditions of the sub-areas.

[0107] Coal spontaneous combustion is mainly caused by the combination of coal and oxygen and the release of heat. After coal contacts with air, physical and chemical reactions occur to release reaction heat, and the accumulated heat changes the environmental conditions of the coal. Therefore, the heat release of coal oxidation is one of the sources of spontaneous heat generation, and is one of the fundamental reasons for coal spontaneous combustion. Coal spontaneous combustion must meet four conditions: (1) the broken coal after mining has spontaneous combustion tendency, and the stacking thickness varies depending on the broken state of the coal, generally, the coal powder is greater than 0.2m, and the floating coal in each goaf is generally greater than 0.4m.(2) the broken coal is flowed through by the gas with high oxygen content to cause continuous oxygen supply conditions (experiments show that when O2>15%, the oxidation proceeds quickly).(3) the broken coal has an environment for accumulating oxidation heat.(4) the time when the above three conditions coexist is greater than the natural ignition period of the coal. The four conditions are indispensable, the first three are necessary conditions for coal spontaneous combustion, and the last one is a sufficient condition.

[0108] Currently, there are two main criteria for classifying the "three zones" of spontaneous combustion in goaf areas:

[0109] (1) Air leakage velocity index: Foreign scholars believe that areas with an air leakage intensity of 0.1 to 0.24 m / min in the goaf are prone to spontaneous combustion.

[0110] (2) Oxygen concentration: Some domestic scholars have concluded through coal heating and oxidation experiments that coal basically no longer undergoes exothermic oxidation reaction when the oxygen concentration is below 9%.

[0111] like Figure 2 As shown, when the goaf is managed using the total caving method, it can generally be divided into three zones based on the degree of overlying rock movement and damage: the caving zone, the fracture zone, and the bending subsidence zone.

[0112] (1) Collapse zone

[0113] The caving zone is the rock strata that collapse into the goaf caused by mining, resulting in the destruction of the overlying strata. The fractured rock blocks collapse irregularly and are arranged very irregularly, with a relatively high looseness coefficient, generally reaching 1.3 to 1.5. After recompaction, the looseness coefficient can be reduced to around 1.03. This area is adjacent to the mined coal seam and is often formed by the collapse of the immediate roof strata. Under top-coal caving mining conditions, the height of the caving zone is approximately 3.7 times the mining height.

[0114] The caving zone is generally formed after the immediate roof collapses, but when the immediate roof is thin and the coal seam is very thick, the basic roof may also enter the caving zone.

[0115] The height of the caving zone depends on the mining height of the coal seam, the lithology of the overlying strata, the coefficient of breccia, and the dip angle of the coal seam. For coal seams of medium dip or shallower, when there are extremely hard strata in the overlying strata of the coal seam roof that can form a suspended roof during mining, the height of the caving zone can be calculated by the following formula when the goaf is filled:

[0116] In the formula: H K M represents the caving zone height in meters (m); K represents the coal seam mining height in meters (m); P α is the rock fragmentation coefficient; α is the coal seam dip angle, in degrees.

[0117] When the roof of a coal seam is a hard, medium-hard, or soft rock layer or an interbedded layer thereof, the subsidence of the roof must be considered. The height of the caving zone formed after coal seam mining can be calculated by the following formula:

[0118] In the formula: w is the amount of subsidence of the roof during the collapse process, and the unit is meters.

[0119] The strata behavior of fully mechanized top coal caving face is closely related to the height of the overlying caving zone, which is related to the dilatancy coefficient of the overlying caving rock and the bending subsidence of the fractured rock beam.

[0120] (2) Fractured zone

[0121] The fractured zone is the area where the rock blocks are still arranged in order after the rock strata break. It is located above the caving zone, and the dilatancy coefficient is small because of the relatively neat arrangement.

[0122] (3) Bending subsidence zone

[0123] All the rock strata from the top boundary of the fractured zone to the ground surface are called the bending subsidence zone. The significant feature of the rock strata movement in the bending subsidence zone is the continuity and integrity of the movement process, i.e., the movement of the rock strata from the top boundary of the fractured zone to the ground surface occurs in layers and as a whole, and the subsidence difference between the upper and lower parts in the vertical section is small.

[0124] As shown in Figure 3 , due to the destruction of the original rock stress field balance around the roadway during the excavation of the upper and lower roadways of the working face, stress redistribution occurs, forming a plastic damage zone around the roadway. During the mining of the working face, the roadway is again damaged due to the influence of the working face mining. A support pressure zone is formed around the goaf due to the influence of the working face mining.

[0125] An advanced support pressure is formed in front of the working face, which moves forward with the advancement of the working face, called mobile support pressure or temporary support pressure. The support pressure formed on the coal body on the side of the open-off cut along the inclined and inclined directions of the working face does not change significantly after a period of working face mining, called fixed support pressure or residual support pressure.

[0126] After the working face advances a certain distance, the overburden strata movement in the goaf will tend to be stable, and the maturing of the caving gangue in some areas of the goaf will gradually compact, supporting the upper uncaving rock strata to a certain extent. Therefore, a small support pressure may also occur in the goaf at a certain distance from the working face, called goaf support pressure.

[0127] The support pressure state in front of and behind the working face is shown in Figure 4 , which is divided into stress reduction area b (decompression zone), stress increase area a (pressure increase zone) and stress constant area (stable pressure zone).

[0128] The peak value of the support pressure in front of the working face to the coal wall is the limit equilibrium zone, and to the inside of the coal body is the elastic zone.

[0129] Research findings:

[0130] The surrounding rock of fully mechanized caving face has a macro stress shell composed of high stress beams, and the position and shape of the stress shell during mining are shown in Figure 5 and Figure 6 .

[0131] The shell base of the stress shell is located in the stress increasing area, and the surrounding rock movement shape along the strike can be divided into five areas:

[0132] ① stress change area I in front of the working face; ② working face roof control area II; ③ loose area of caving rock III; ④ gradually compressed area of caving rock IV; ⑤ compacted area of caving rock V.

[0133] The relationship between the "three zones" of the goaf and the "horizontal three zones" of the fully mechanized caving face along the advancing direction and the "five zones" of the stress shell is shown in Table 1.

[0134] Table 1

[0135]

[0136] The spontaneous combustion of the goaf is the result of the mutual coupling of the gas seepage velocity, oxygen concentration and temperature in the goaf.

[0137] As the mining face advances continuously, the boundary of the goaf changes continuously and the spatial range expands continuously. Therefore, the moving coordinate system is introduced to convert the goaf with expanding depth into a stable and regionally fixed research object.

[0138] As shown in Figure 7 , the air inlet is taken as the origin (o), the y-axis is set on the top cutting line of the working face, and the x-axis is along the strike of the goaf. The movement speed of the working face can be approximately regarded as a fixed constant.

[0139] As shown in Figure 8 , the selected goaf control unit contains enough floating coal and debris, forming a porous structure. The size of the caving gangue is much smaller than that of the goaf, so the goaf medium can be theoretically regarded as a continuous porous medium.

[0140] The boundary near the working face is Γ1, the upper and lower two rows of coal pillars are Γ2 and Γ3 boundaries, the roof boundary is Γ5, the floor boundary is Γ6, and the deep boundary is Γ4. The boundary of the solid temperature field of the goaf is relatively complex, because the heat generated by the oxidation of residual coal is not only transferred within the actual boundary of the goaf, but also dissipated to the surrounding coal wall, roof and floor. The heat flux on the actual boundary is uncertain, so the actual boundary cannot be used as the calculation boundary of the solid temperature field, and needs to be extended to the protective coal pillars on both sides, i.e. the boundaries on both sides are extrapolated to the position where the heat flux is almost 0, so that it can be set as the second type of boundary condition.

[0141] Based on the data obtained by the optical fiber temperature measuring host, distributed temperature measuring optical fiber, switch and industrial computer, combined with the pressure field and oxygen concentration field in the goaf, the mathematical model of spontaneous combustion in goaf is established.

[0142] The mathematical model of spontaneous combustion in goaf is:

[0143]

[0144] The boundary conditions are:

[0145]

[0146] Wherein, K is the permeability coefficient of porous medium, the unit is m / s; p g is the gas density in the control body, the unit is kg / m 3 ; g is the acceleration of gravity, the unit is m / s 2 ; P is the sum of static pressure and velocity pressure, the unit is Pa; a is the inclination of coal seam, the unit is degree; n is the porosity of floating coal in goaf, the unit is %; K O2 is the diffusion coefficient constant of oxygen; C O2 is the molar concentration of oxygen, the unit is mol / m 3 ; T g is the gas temperature, the unit is K; T s is the temperature of coal and rock, the unit is K; p s is the density of coal and rock, the unit is kg / m 3 ; C s is the specific heat capacity of coal and rock KJ / (kg·K); p s is the density of solid particles, the unit is kg / m 3 ; l g is the gas thermal conductivity, the unit is W / m·℃; p g is the density of goaf gas, the unit is kg / m 3 ; C g is the specific heat capacity of gas KJ / (kg·℃); u (t) is the oxygen consumption per unit volume per unit time, the unit is mol / (s·m 3 ); l s is the thermal conductivity of caving coal and rock in goaf, the unit is W / m·℃; q (t) is the heat release of residual coal in the control body per unit time, the unit is kJ / (mol·s); K e is the convective heat transfer coefficient between coal and gas, the unit is J / (m 2 ·s·K);

[0147] The solution method of the goaf spontaneous combustion mathematical model comprises the following steps: determining the solution range of the model, dividing the calculation region into grids, discretizing the model and its boundary conditions according to the finite volume method to obtain node equation groups of pressure, oxygen concentration and temperature, and finally coupling and solving the node equation groups by a computer program.

[0148] Specifically, as shown in Figure 9 the solution method of the goaf spontaneous combustion mathematical model specifically comprises the following steps:

[0149] S1, defining constants, variables and arrays;

[0150] S2, inputting basic parameters;

[0151] S3, profiling the goaf network;

[0152] S4, node correlation matrix;

[0153] S5, node array initialization;

[0154] S6, coefficient matrix assignment of each field;

[0155] S7, iterative calculation;

[0156] S8, variable assignment in each field;

[0157] S9, using density to correct the pressure coefficient matrix;

[0158] S10, calling a subroutine to solve the pressure field;

[0159] S11, taking the maximum value of pressure change and saving;

[0160] S12, obtaining velocity components from pressure;

[0161] S13, modifying the oxygen concentration coefficient matrix from velocity and temperature;

[0162] S14, calling a subroutine to solve the oxygen concentration field;

[0163] S15, taking the maximum change value of oxygen concentration and saving;

[0164] S16, modifying the temperature coefficient matrix from velocity and oxygen concentration;

[0165] S17, calling a subroutine to solve the temperature field;

[0166] S18, taking the maximum change value of the temperature field and saving;

[0167] S19, comparing the maximum change values in the three fields;

[0168] S20, taking the maximum value of the three;

[0169] S21, judging whether the precision is reached, yes to S22, otherwise returning to S7;

[0170] S22, saving the calculation result;

[0171] S23, outputting the.dat file of pressure, velocity, oxygen concentration and temperature;

[0172] S24, showing the picture by post-processing software;

[0173] S25, outputting the distribution graph of pressure, velocity, oxygen concentration and temperature.

[0174] Correspondingly, according to the goaf spontaneous combustion mathematical model and its solving method, a goaf spontaneous combustion three-dimensional simulation system can be built, and the system has the following characteristics:

[0175] (1) a goaf spontaneous combustion mathematical model is established, which is coupled with the goaf air leakage flow field, oxygen concentration field and temperature field under the mobile coordinate;

[0176] (2) the flow field model is established based on the non-Darcy equation, which is more accurate than other flow field models established based on Darcy's law to reflect the actual air flow movement law in the goaf;

[0177] (3) the grid is encrypted in the area where the field changes greatly, i.e. near the intake and return airways and the working face area;

[0178] (4) the finite volume method is used to solve the model, which is more accurate than the finite element method;

[0179] (5) the data file after solving can be directly recognized by the post-processing software such as Tecplot, and the visual image display of the solving data is easily realized.

[0180] The system simulation includes the following processes:

[0181] (1) the mining feature parameters of the stope (including the mining technology of the working face, the ventilation system, the geometric shape of the goaf, the inhomogeneity of the caving, the permeation characteristics and other physical and mechanical parameters);

[0182] (2) the movement of the coal mining working face;

[0183] (3) the distribution of the residual coal in the goaf;

[0184] (4) the air leakage and seepage state of the goaf;

[0185] (5) the thermodynamic process of coal spontaneous combustion and oxidation;

[0186] (6) the temperature change process of the caving rock in the goaf;

[0187] (7) the temperature variation process of the gas in the goaf;

[0188] (8) the coupling between the flow velocity, oxygen concentration and temperature in the goaf.

[0189] Main calculation and analysis functions

[0190] (1) Goaf flow field calculation: the air pressure distribution and velocity field of the caving heterogeneous goaf;

[0191] (2) Goaf oxygen concentration calculation: oxygen consumption and concentration distribution in the goaf;

[0192] (3) Goaf caving rock temperature field calculation: temperature distribution of the caving rock in the goaf;

[0193] (4) Goaf gas temperature field calculation: gas temperature distribution in the goaf.

[0194] The visualized graphical display of the data results adopts Tecplot9.0 software, and provides the contour maps, 3D grid line maps and chroma distribution maps of the quantity distribution, the variation process curve maps of the quantities, the divided grid maps and the auxiliary explanatory texts, parameters and data in addition to the graphics.

[0195] It is worth noting that the several sub-regions are monitored, warned and prevented in the application, and the main purpose is to reduce the probability of spontaneous combustion in the most dangerous region, that is, the dangerous region (including the second region and the third region) is mainly considered to be treated by what prevention and control measures, and it is possible to only take prevention and control measures for a certain region, or it is possible to take prevention and control measures for all regions, but the ways of taking the measures can be different.

[0196] At the same time, the workers can be warned according to the danger degree, so as to ensure the safety of the workers.

[0197] Working principle of the application:

[0198] The distributed temperature measurement substation collects the temperature data of the goaf through the distributed temperature measurement optical fiber; the optical fiber temperature measurement host or the distributed temperature measurement substation divides the temperature distribution map into several sub-regions based on the fluid mechanics software.

[0199] The several sub-regions are prevented according to the characteristics of different prevention and control measures, and the workers are warned according to the several sub-regions.

[0200] The above examples are only used to illustrate the technical method of the application but not to limit the application, and although the application is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical method of the application can be modified or replaced equivalently without departing from the spirit and scope of the technical method of the application.

Claims

1. A temperature monitoring system for the goaf area of ​​a working face, comprising a fiber optic temperature measurement host, distributed temperature measurement fibers, a switch, and an industrial control computer, wherein the industrial control computer and the fiber optic temperature measurement host are connected via a switch, characterized in that: The fiber optic temperature measurement host is connected to the distributed temperature measurement substation via a transmission fiber, and the distributed temperature measurement substation collects temperature data of the goaf area via a distributed temperature measurement fiber. A temperature distribution map of the goaf is generated based on temperature data; the temperature distribution map is updated in real time or at regular intervals. The temperature distribution map is divided into regions by combining temperature thresholds to obtain several sub-regions; among them, the temperature thresholds are used to distinguish the degree of danger of temperature in the goaf, including a second threshold and a third threshold, and the second threshold is less than the third threshold. Early warnings are issued to staff based on the temperature conditions of several sub-regions, and prevention and control measures are implemented based on the temperature conditions of several sub-regions. The process of obtaining a temperature distribution map based on the temperature data includes: Temperature data is acquired through distributed temperature-sensing optical fibers; By combining fluid dynamics software with temperature data, a temperature distribution map of the goaf can be obtained. The temperature distribution map is used to obtain several sub-regions, including: Data points with temperature values ​​less than the second threshold in the temperature distribution map are obtained and marked as first location points. The area composed of the first location points is marked as the first region. The locations in the temperature distribution map with temperature values ​​greater than or equal to the third threshold are identified and marked as the third location points. The region composed of the third location points is then marked as the third region. The area in the goaf, excluding the first and third zones, is designated as the second zone. The temperature distribution map and the bundle tube data are combined to obtain several sub-regions, including: Extract the concentration of indicator gases from the bundle tube data; the indicator gases include carbon monoxide and methane. When the concentration of the indicator gas exceeds the corresponding threshold, acquire the temperature data around the detection point corresponding to the indicator gas. The area consisting of locations with temperature data greater than or equal to the second threshold is marked as a danger zone.

2. The temperature monitoring system for the goaf area of ​​a working face according to claim 1, characterized in that, The bundled tube data refers to the gas component concentration at the detection point in the goaf, and the bundled tube data is obtained through a bundled tube detection device.

3. The temperature monitoring system for the goaf area of ​​a working face according to claim 2, characterized in that, The tube testing device includes an air pump, a control cabinet, and a multi-core tube; wherein the multi-core tube is a mining-grade anti-static flame-retardant polyethylene tube.

4. The temperature monitoring system for the goaf area of ​​a working face according to claim 1, characterized in that, Based on the data obtained by the fiber optic temperature measurement host, the distributed temperature measurement fiber, the switch and the industrial control computer, a mathematical model for spontaneous combustion in the goaf is established by combining the pressure field and oxygen concentration field in the goaf. The mathematical model for spontaneous combustion in the goaf is: ； The boundary conditions are: ； Where K is the permeability coefficient of the porous medium, with units of m / s; ρ g To control the density of gases within the body, the unit is kg / m³. 3 g is the acceleration due to gravity, and its unit is m / s². 2 P is the sum of static pressure and rapid pressure, in Pa; α is the dip angle of the coal seam, in degrees; n is the porosity of the loose coal in the goaf, in %; K O2 C is the diffusion coefficient constant of oxygen; O2 This refers to the molar concentration of oxygen, with units of mol / m³. 3 ;T g Temperature of the gas, in Kelvin (K); T s ρ represents the temperature of coal and rock, measured in Kelvin (K). s This refers to the density of coal and rock, expressed in kg / m³. 3 C s Specific heat capacity of coal and rock (kJ / (kg·K)); ρ s Density of solid particles, in kg / m³ 3 ;λ g ρ is the thermal conductivity of a gas, measured in W / m·℃. g This refers to the density of the gas in the goaf, expressed in kg / m³. 3 C g Specific heat capacity of gas (kJ / (kg·℃)); u （t） Oxygen consumption per unit volume per unit time, expressed in mol / (s·m). 3 ); λ s q represents the thermal conductivity of the collapsed coal and rock in the goaf, expressed in W / m·℃. （t） The heat released by the body's residual coal per unit time is expressed in kJ / (mol·s); K e The convective heat transfer coefficient between coal / rock and gas is expressed in J / (m³). 2 ·s·K); The solution method of the mathematical model for spontaneous combustion in the goaf includes: determining the solution range of the model, dividing the computational region into grids, discretizing the model and its boundary conditions using the finite volume method to obtain the nodal equations for pressure, oxygen concentration and temperature, and finally solving the nodal equations by coupling them using a computer program.

5. The temperature monitoring system for the goaf area of ​​a working face according to claim 4, characterized in that, The solution method for the mathematical model of spontaneous combustion in the goaf specifically includes the following steps: S1. Define constants, variables, and arrays; S2. Input basic parameters; S3, Goaf subdivision network; S4, Node Association Matrix; S5. Initialize the node array; S6. Assign values ​​to the coefficient matrix of each field; S7, Iterative calculation; S8. Assign initial values ​​to the variables in each field during iteration; S9. Correct the pressure coefficient matrix using density; S10. Call the subroutine to solve the pressure field; S11. Take the maximum pressure change value and save it; S12. Determine the velocity component from the pressure; S13. Modify the oxygen concentration coefficient matrix based on velocity and temperature; S14. Call the subroutine to calculate the oxygen concentration field; S15. Record the maximum change in oxygen concentration and save it. S16. Modify the temperature coefficient matrix based on velocity and oxygen concentration; S17. Call the subroutine to solve the temperature field; S18. Save the maximum change value of the temperature field; S19. Compare the maximum changes in the three fields; S20. Take the maximum value of the three; S21. Determine if the required precision has been achieved. If yes, proceed to S22; otherwise, return to S7. S22. Save the calculation results; S23, Output pressure, speed, oxygen concentration, and temperature in a .dat file; S24. Post-processing software displays the image; S25. Output pressure, speed, oxygen concentration, and temperature distribution diagram.

6. The temperature monitoring system for the goaf area of ​​a working face according to claim 1, characterized in that, One of the aforementioned fiber optic temperature measurement main units is configured with one of the aforementioned distributed temperature measurement substations, or One fiber optic temperature measurement host is configured with N distributed temperature measurement substations; where N is an integer greater than 1.

7. The temperature monitoring system for the goaf area of ​​a working face according to claim 1, characterized in that, A distributed temperature-measuring optical fiber is laid in the machine roadway of the goaf, and several distributed temperature-measuring optical fibers are evenly laid in the ventilation roadway of the goaf. Among them, the optical fiber temperature-measuring optical fibers buried inside the goaf are protected by screen tubes, and the optical fiber temperature-measuring optical fibers at the upper and lower corners of the goaf are protected by high-pressure oil pipes.

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