A coal pile temperature abnormal area monitoring and early warning method

Abstract

The present invention proposes a method for monitoring and early warning of abnormal temperature areas of coal piles, including: S1, drilling holes in the ground for stacking coal piles, and placing a shock wave receiving sensor in the hole; then drilling ground grooves according to the number of drill hole columns, if there are μ columns of drill holes, μ+1 ground grooves need to be drilled, so that any column of drill holes and any row of drill holes are connected through the ground grooves; S2, arranging shock wave sources on the outer surface of the coal pile: S3, collecting shock wave signal data; S4, after collecting the signal data of shock waves emitted by m sources received by n shock wave receiving sensors within a cycle, the shock wave signal data is transmitted to a shock wave data analysis and processing host; the data analysis and processing host performs real-time analysis and processing on the monitoring data, converts the shock wave signal into temperature, and thus issues an early warning based on the temperature. The method of the present invention can realize efficient monitoring, early warning and positioning of abnormal temperature areas of coal piles, and prevent the occurrence of coal spontaneous combustion.

Description

Technical Field

[0001] The patent of this invention relates to the field of mine safety and monitoring, specifically a method for monitoring and early warning of abnormal temperature areas in coal piles. Background Art

[0002] Coal still occupies a dominant position in my country's energy structure. Due to actual production needs, a large amount of coal is often piled up on the surface of thermal power plants, coal transportation ports, and mining areas to form coal piles. The broken coal piles are piled in the atmospheric environment for a long time, which poses a great safety hazard. In a good heat storage environment, the coal piles are very likely to heat up and turn into spontaneous combustion. In addition, the scale of open-air coal piles is large, and spontaneous combustion is difficult to quickly control. While threatening the safety of life and property, it will also cause a waste of coal resources and affect the safe operation of coal yards. Exploring new real-time monitoring technologies and methods for coal pile temperature is of great significance to the safety management of coal piles.

[0003] Some existing technologies use temperature sensors placed in coal piles to monitor the internal temperature of the coal pile, but this method is difficult to accurately perceive the abnormal temperature area perceived inside the coal pile, and this method has the disadvantage that the sensor is difficult to recover and cannot be reused, such as patent [CN203465807U]; some patents place a galvanized steel pipe in the center of the gangue mountain to monitor different height areas of the gangue mountain, but this method cannot accurately monitor the internal temperature of the gangue mountain, such as patent [CN112943372A]; in addition, there is also the use of infrared thermal imaging and spectral monitoring to achieve coal pile temperature monitoring, but this method is difficult to perceive and can only perceive the surface temperature of the coal pile, and it is difficult to accurately monitor the internal temperature of the coal pile, such as patents [CN102878983B, CN115979985A].

[0004] In addition, currently, infrared thermal imaging technology, deep base point temperature measurement, drone inspection and other methods are mostly used to monitor coal pile spontaneous combustion. There are mainly the following problems in the implementation process:

[0005] 1. Infrared thermal imaging technology is more sensitive and accurate in sensing surface temperature, but it is difficult to effectively capture the temperature deep inside;

[0006] 2. For larger coal piles, using deep base point temperature measurement technology to detect temperature is labor-intensive, time-consuming and labor-intensive;

[0007] 3. Infrared thermal imaging technology and deep base point temperature measurement technology are difficult to accurately determine the abnormal location of the perceived temperature abnormal area;

[0008] 4. Due to the limited endurance of drones, drone inspection technology cannot monitor the temperature of coal piles 24 hours a day, and cannot monitor in real time and grasp the temperature distribution in all directions;

[0009] 5. Deep base point temperature measurement technology: As the coal pile is removed and stacked, the measuring points need to be rearranged, and the sensors are difficult to reuse. Summary of the invention

[0010] The present invention aims to at least solve the technical problems existing in the prior art, and in particular innovatively proposes a method for monitoring and early warning of abnormal temperature areas in a coal pile.

[0011] In order to achieve the above-mentioned object of the present invention, the present invention provides a method for monitoring and early warning of abnormal temperature areas of coal piles, comprising:

[0012] S1, drilling holes in the ground for stacking coal piles, and placing vibration wave receiving sensors in the holes; N holes are arranged in a square, with a total of μ rows of holes, where the spacing between adjacent holes is a; then ground grooves are punched according to the number of holes, and if there are μ rows of holes, μ+1 ground grooves need to be punched, so that any row of holes and any column of holes are connected through the ground grooves;

[0013] The vibration wave collection line extending from the borehole is arranged in the ground groove based on the column, and finally from R x-1 The sensors are arranged in the ground grooves of the drilled holes, and then arranged in the ground grooves connecting the first row of drilled holes, and finally from R 1-1 The ground grooves where the sensors are located in the drilled holes are collected and connected to the vibration wave collection station.

[0014] S2, arrange the shock wave source on the outer surface of the coal pile:

[0015] S3, collecting vibration wave signal data;

[0016] S4, after collecting the signal data of the vibration waves emitted by m seismic sources received by n vibration wave receiving sensors within one cycle, the vibration wave signal data is transmitted to the vibration wave data analysis and processing host through the data transmission line; the data analysis and processing host performs real-time analysis and processing on the monitoring data, converts the vibration wave signal into temperature, and issues an early warning based on the temperature.

[0017] Furthermore, a hollow metal protection net is installed at the top of the drill hole to protect the shock wave receiving sensor.

[0018] Further, the shock wave sources are arranged on the outer surface of the coal pile as follows: the shock wave sources are arranged on the first layer, the second layer and the top of the coal pile respectively, the first layer is at a vertical height of 1 / 3H of the coal pile relative to the ground, the second layer is at a vertical height of 2 / 3H of the coal pile relative to the ground, and the third layer is at the top of the coal pile. The numbers of shock wave sources arranged at the three levels are m1, m2 and m3 respectively, and the shock wave sources at each level are evenly arranged in a ring shape on the surface of the coal pile at that level;

[0019] The row vector direction of the shock wave receiving sensor is taken as the positive direction of the polar axis, the counterclockwise direction is taken as the positive direction of rotation, and the jth source of the i-th level is represented by E i-j To express;

[0020] The seismic source of each layer periodically emits shock waves in sequence at short time intervals. The shock waves penetrate the coal pile and are received by n enabled shock wave receiving sensors arranged on the ground of the coal pile, where n is the number of shock wave receiving sensors enabled according to the detection purpose.

[0021] Furthermore, collecting vibration wave signal data includes:

[0022] S3-1, shock waves emitted by the source;

[0023] S3-2, the shock wave penetrates the coal pile and is received by n shock wave receiving sensors activated on the ground of the coal pile;

[0024] S3-3, the shock wave acquisition station collects the shock wave signals received by each shock wave receiving sensor through the shock wave acquisition survey line, and records the wave signal data of the corresponding source and the corresponding sensor, marked as S i-j-x-y .

[0025] Furthermore, the data analysis and processing host performs real-time analysis and processing on the monitoring data, converts the vibration wave signal into temperature, and issues an early warning based on the temperature. The steps include:

[0026] (1) First, the interior of the coal pile is divided into several spatial regions according to the positions of the shock wave source and the shock wave receiving sensor, and the detection area is divided into uniform grid points;

[0027] (2) For each grid point, determine the propagation paths from the earthquake source to that point and measure the propagation time of the shock waves along these paths;

[0028] (3) Based on the measured propagation time and propagation path length, the wave velocity at each grid point is calculated; then, based on the relationship between the wave velocity and temperature, the temperature of each temperature point in the coal pile area is obtained;

[0029] (4) Determine whether the difference between the lowest temperature point and the highest temperature point in the grid point is greater than the first temperature difference. If so, it indicates that the temperature difference in the grid point is too large and the current grid fine-grained evaluation accuracy is not high. Then, reduce the grid size until the difference between the lowest temperature point and the highest temperature point in the grid point is less than the first temperature difference.

[0030] Then determine whether the difference between the lowest temperature point and the highest temperature point in the grid point is greater than the second temperature difference (the first temperature difference is greater than the second temperature difference). If it is greater, it means that there is a significant temperature difference in the grid point. In order to effectively prevent local high temperature, the highest temperature in the grid point is used as the temperature value of the grid point; if it is less than, the average temperature of each point in the grid point is used as the temperature value of the grid point; among them, the first temperature difference and the second temperature difference can be set manually.

[0031] The temperature within the grid point obtained in this way can accurately represent the temperature of each grid point, rather than the general uniform grid division, and the average value is used as the grid point temperature; the temperature of the grid point obtained by the method of the present invention can greatly improve the monitoring ability of the coal pile temperature.

[0032] (5) The temperature data of all grid points are integrated to form a three-dimensional temperature field; if the temperature of a grid point is higher than the set high temperature alarm temperature T A , it is determined to be a local high temperature area; local high temperature may be a precursor to spontaneous combustion, so it is very important to focus on monitoring the temperature of these areas.

[0033] Furthermore, the wave velocity of each grid point is calculated based on the measured propagation time and propagation path length; then, the temperature of each temperature point in the coal pile area is obtained based on the relationship between the wave velocity and the temperature; including:

[0034] Assume that the inverse distribution of the wave velocity in the detection area is f(x,y,h), then the vibration wave propagation path S i-j-x-y The propagation time t i-j-x-y It can be expressed as:

[0035]

[0036] Among them, ds is the integral differential element of the propagation path length of the shock wave;

[0037] S i-j-x-y The source E i-j To the shock wave receiving sensor R x-y the distance of this propagation path;

[0038] t i-j-x-y From the source E i-j Transmit shock waves to shock wave receiving sensor R x-y The time it takes to receive the shock wave;

[0039] Therefore, the inverse wave velocity distribution f(x, y, h) in the detection area within the coal pile can be expressed as:

[0040]

[0041] P represents the total number of divided grids;

[0042] β p It represents the inverse distribution of wave velocity in the coal pile;

[0043] represents the inverse approximation function of the wave velocity of the pth grid;

[0044] e is the rank of matrix b, which is the set of integrals of P radial basis functions over S propagation paths;

[0045] θ represents the shape parameter of the radial basis function;

[0046] (x, y, h) represent the spatial coordinates in the coal pile;

[0047] (x p ,y p ,h p ) represents the spatial coordinates of the center point of the pth grid.

[0048] After obtaining the three-dimensional wave velocity field of the detection area in the coal pile, the temperature information of the detection area of ​​the coal pile is determined according to the relationship between wave velocity and temperature:

[0049]

[0050] Where T represents the temperature of each temperature point in the coal pile area, which is the thermodynamic absolute temperature;

[0051] c e is the wave velocity value of the three-dimensional wave velocity field in the detection area within the coal pile;

[0052] Generally take a constant value;

[0053] y is the ratio of the specific heat capacity at constant pressure to the specific heat capacity at constant volume of the gas medium;

[0054] R represents the gas constant, usually 8.314 J / (mol·K);

[0055] q represents the molecular weight of the gas, in kg / mol.

[0056] Furthermore, the data analysis and processing host performs real-time analysis and processing on the monitoring data, including:

[0057] The overall temperature of the coal pile, the temperatures of different grid points inside the coal pile and their importance or weights are calculated by the weighted method to obtain a representative average temperature value, which helps to understand the temperature status of the entire coal pile.

[0058] Different areas of the coal pile have different effects on the overall temperature of the coal pile, as follows:

[0059] Central area: The central area of ​​the coal pile is far away from the outside air, so it accumulates more heat and dissipates heat more slowly. Therefore, the temperature in the central area is often higher, which has a significant impact on the overall temperature of the coal pile.

[0060] Bottom area: The bottom area may be under pressure from the upper coal layer, which may cause heat conduction to be blocked. At the same time, if the bottom is poorly ventilated, heat may accumulate. Therefore, the temperature of the bottom area may also have a greater impact on the overall temperature of the coal pile.

[0061] Edge area: The edge area may have a faster heat dissipation rate due to its contact with the outside world, but the temperature of the edge area may also vary due to the influence of the external environment (such as wind speed and humidity).

[0062] Therefore, the overall temperature of the coal pile is calculated in the following way:

[0063]

[0064] Where T represents the overall temperature of the coal pile;

[0065] T 1i , T 2i , T 3i , T 4i Represent the temperature of the i-th grid point in the center area, bottom area, edge area, and general area respectively;

[0066] w i is the weight coefficient of the i-th grid point;

[0067] α and β are the correction coefficients of the grid points in the center area and the grid points in the bottom area, respectively, both of which are greater than 1;

[0068] χ is the correction coefficient of the grid points in the edge area, which is less than 1;

[0069] L1, L2, L3, and L4 are the number of grid points in the center area, bottom area, edge area, and general area, respectively.

[0070] The overall temperature of the coal pile is calculated using a weighted average method. This method takes into account the temperatures of different grid points inside the coal pile and their importance or weights to obtain a representative average temperature value, which helps to understand the temperature status of the entire coal pile.

[0071] In summary, due to the adoption of the above technical solution, the method of the present invention only arranges detectors at the bottom and surface of the coal pile, which is convenient to arrange; it can accurately sense the abnormal temperature area sensed inside the coal pile, and can accurately detect the temperature inside the coal pile. The method of the present invention is simple, easy to implement, and effective, without the need for too many data monitoring instruments, and can accurately estimate the temperature of the coal pile, thereby realizing the monitoring and early warning of abnormal areas of the coal pile.

[0072] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0074] Figure 1 It is a structural schematic diagram of the present invention.

[0075] Figure 2 It is a flow chart of the method of the present invention.

[0076] Figure 3 It is a top plan view of the drilling arrangement of the shock wave receiving sensor of the present invention.

[0077] Figure 4 It is a schematic diagram of the layout of the ground grooves of the present invention.

[0078] Figure 5 It is a schematic diagram of drilling and installing a shock wave receiving sensor of the present invention.

[0079] Figure 6 It is a schematic diagram of the shape of the hollow metal mesh of the present invention.

[0080] Figure 7 It is a front view of the arrangement of the shock wave source of the present invention.

[0081] Figure 8 It is a top view of the arrangement of the shock wave sources of the present invention.

[0082] Fig. 9 It is a top view of the shock wave transmission path of the present invention.

[0083] Fig.10 It is a front view of the shock wave transmission path of the present invention.

[0084] Fig.11 It is a schematic diagram of three-dimensional multi-layer isotherms of the internal space of a coal pile according to the present invention.

[0085] Fig.12 It is a high temperature alarm flow chart of the present invention. DETAILED DESCRIPTION

[0086] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0087] The present invention is used for monitoring, early warning and positioning systems for abnormal temperature areas in coal piles, such as Figure 1 As shown, it includes a shock wave transmitting module, a shock wave collecting module, and a shock wave data analyzing and processing module.

[0088] The shock wave transmitting module comprises three levels m1, m2, and m3, with a total of M shock wave sources (1), and the sources of each level are evenly arranged in a ring shape on the surface of the coal pile at that level. The shock wave collecting module comprises N shock wave receiving sensors (2), a shock wave collecting survey line (3), and a shock wave collecting station (4). The shock wave collecting station (4) is connected to the shock wave receiving sensors (2) at N measuring points through the shock wave collecting survey line (3), and collects the wave signals received by the shock wave receiving sensors. The N shock wave receiving sensors (2) are embedded in the boreholes (7) on the ground of the coal pile, and the shock wave collecting survey line (3) is arranged in the groove on the ground of the coal pile. The vibration wave data analysis and processing module comprises a vibration wave data analysis and processing host (5) and a data transmission line (6). The data analysis and processing host is connected to the vibration wave acquisition station (4) via the data transmission line (6) and is responsible for receiving and storing the wave signals of M vibration sources (1) received by n vibration wave receiving sensors (2) collected by the vibration wave acquisition station (4), analyzing and processing the wave signals, obtaining the three-dimensional space temperature field data inside the coal pile through data model calculation, and realizing real-time monitoring, historical data query, high temperature alarm and other functions based on the three-dimensional space temperature field data inside the coal pile.

[0089] The present invention discloses a coal pile temperature abnormal area monitoring and early warning system and a positioning method thereof, comprising the steps of installing a shock wave receiving sensor, arranging a shock wave source, collecting shock wave data, processing shock wave signal data, converting shock wave velocity and temperature data, processing and analyzing three-dimensional temperature data, and the like. The specific steps are as follows: Figure 2 As shown:

[0090] S1. Before stacking the coal, drill holes and make grooves on the ground of the coal pile and install vibration wave receiving sensors.

[0091] The arrangement of ground drilling holes is as follows Figure 3 As shown, the borehole size should be able to fully accommodate the vibration wave receiving sensor. The borehole layout is a square layout. According to the size of the coal pile on the ground, a total of N cylindrical boreholes are drilled. The distance between adjacent boreholes is a. The size of a is determined according to the actual size of the coal pile and the required detection accuracy. The smaller a is, the higher the detection accuracy is, and the larger a is, the lower the detection accuracy is.

[0092] The arrangement of the grooves is as follows Figure 4 As shown, ground grooves are drilled according to the number of drill hole columns. If there are μ columns of drill holes, μ+1 ground grooves need to be drilled, and the extra grooves are used to integrate all the survey lines together; any column of drill holes and the first row of drill holes are connected through the ground grooves.

[0093] The vibration wave collection line extending from the borehole is arranged in the ground groove based on the column, and finally from R x-1 The sensors are arranged in the ground grooves of the drilled holes, and then arranged in the ground grooves connecting the first row of drilled holes, and finally from R 1-1 The ground groove of the borehole where the sensor is located is collected and connected to the vibration wave collection station. When connecting the vibration wave receiving sensor and the vibration wave collection station through the vibration wave collection line, pay attention to the channel number of the collection station and the vibration wave receiving sensor R x-y The collection measurement lines correspond to each other to ensure that the actual shock wave receiving sensor corresponds to the connection position, and the spatial position information of each shock wave receiving sensor is recorded for the conversion of shock wave velocity and temperature data.

[0094] like Figure 5 , Figure 6 As shown, a shock wave receiving sensor is installed in the borehole and a shock wave collection measuring line is connected. After completion, a hollow metal protection net is installed on the shock wave receiving sensor, i.e., the top of the borehole. The hollow metal protection net is responsible for protecting the shock wave receiving sensor.

[0095] S2. Pile the coal in the ground drilling area, and then arrange the shock wave source on the outer surface of the coal pile.

[0096] The arrangement of the shock wave source is as follows Figure 7 , Figure 8 As shown in the figure, the first layer is at a vertical height of 1 / 3H of the coal pile relative to the ground, the second layer is at a vertical height of 2 / 3H of the coal pile relative to the ground, and the third layer is at the top of the coal pile. The number of shock wave sources arranged at the three levels are m1, m2, and m3 respectively. The shock wave sources at each level are evenly arranged in a ring on the surface of the coal pile at that level. Figure 8 As shown in the figure, with the geometric center of the top view of the coal pile as the origin, the row vector direction of the shock wave receiving sensor as the positive direction of the polar axis, and the counterclockwise direction as the positive direction of rotation, the jth seismic source at the i-th level can be expressed by E i-j The seismic source of each layer periodically emits shock waves in sequence at short time intervals, and the shock waves penetrate the coal pile and are received by n enabled shock wave receiving sensors arranged on the ground of the coal pile (n is the number of shock wave receiving sensors enabled according to the detection purpose);

[0097] S3. Shock wave data collection.

[0098] During the data collection process, the transmission path of the shock wave is as follows: Fig. 9 , Fig.10As shown in FIG. 1 , m different seismic sources perform the following operations periodically: (1) the seismic source emits a shock wave; (2) the shock wave penetrates the coal pile and is received by n shock wave receiving sensors activated on the coal pile ground; (3) the shock wave acquisition station collects the shock wave signals received by each shock wave receiving sensor through the shock wave acquisition survey line and records the wave signal data of the corresponding seismic source and the corresponding sensor, which is marked as S i-j-x-y , finally, after collecting the signal data of the shock waves emitted by m seismic sources received by n shock wave receiving sensors in one cycle, the shock wave signal data is transmitted to the shock wave data analysis and processing host through the data transmission connection;

[0099] S4. The data analysis and processing host performs real-time analysis and processing on the monitoring data, including data processing of the vibration wave signal, conversion of the vibration wave velocity and temperature data, and processing and analysis of the three-dimensional temperature data. Fig.11 shown.

[0100] The vibration wave data analysis and processing host is based on the vibration wave signal data of one cycle transmitted by the vibration wave acquisition station and the vibration wave receiving sensors R x-y and source E i-j The spatial information (X, Y, H) of the coal pile is obtained, and the acoustic time of the shock wave propagating in the coal pile is obtained from the shock wave data. By constructing a three-dimensional wave velocity field inversion model in the detection area of ​​the coal pile, solving the model and correcting the errors, the shock wave velocity field information (X, Y, H, c e ), and based on the correspondence between the wave velocity information and the coal temperature in the coal pile, the three-dimensional temperature field of the detection area inside the coal pile is obtained.

[0101] Based on the above analysis, a forward and inverse problem model of the three-dimensional wave velocity field in the coal pile is constructed. First, the forward problem of the reconstruction of the three-dimensional wave velocity field in the coal pile is constructed. The forward problem of the reconstruction of the three-dimensional wave velocity field is to calculate the acoustic time of the vibration wave in each propagation path given the spatial position information of the vibration wave receiving sensor and the source and the inverse distribution of the wave velocity in the detection area in the coal pile. Suppose the inverse distribution of the wave velocity in the detection area is f(x, y, h), then the vibration wave in the propagation path S i-j-x-y The propagation time t i-j-x-y It can be expressed as:

[0102]

[0103] Among them, ds is the integral differential element of the shock wave propagation path length.

[0104] Since the distribution of f(x, y, h) in the detection area inside the coal pile is very complex, it is difficult to give its accurate function expression. Therefore, a linear combination of a set of Markov radial basis functions can be used to approximate f(x, y, h). In the three-dimensional space of the detection area inside the coal pile, the expression of the Markov radial basis function is:

[0105]

[0106] Wherein, θ is the shape parameter of the radial basis function, θ>0, and (x0, y0, h0) is the center of the radial basis function.

[0107] At the same time, in order to realize the reconstruction of the three-dimensional wave velocity field in the detection area, the detection area needs to be divided into P uniform grids. At the same time, when dividing the grids, it should be ensured that the number of divided grids is greater than the number of propagation paths. After the grid division is completed, the center points of these grids are used as the center points of the radial basis functions to construct P Markov radial basis functions, and the linear combination of these radial basis functions is used to approximate the complex f(x,y,h) function, so f(x,y,h) can be expressed as:

[0108]

[0109] Among them, β p is a parameter used to describe the inverse distribution of wave velocity, (x p ,y p ,h p ) is the spatial coordinate of the center point of the pth grid.

[0110] Substituting the approximate function of the inverse function of the wave velocity into the acoustic time calculation formula of the vibration wave along different propagation paths, the path S can be obtained. i-j-x-y The sound time t i-j-x-y :

[0111]

[0112] For the convenience of representation, we define: β=(β1,β2,...,β P ) T , b=(b sp ) S×P , t=(t1,t2,...,t S ) T , s=1,2,...,S,p=1,2,...,P,S is the total number of vibration wave propagation paths in the detection area of ​​the coal pile, P is the total number of grids, and the matrix b is the set of integrals of P radial basis functions on S propagation paths, b sp represents the integral of the pth radial basis function on the sth path; vector t is the acoustic time vector of the vibration wave, t i-j-x-y ∈t. Then the above formula can be written as:

[0113] t=bβ

[0114] The above formula is a three-dimensional wave velocity field inversion forward problem model in the coal pile established by approximating the inverse wave velocity distribution f(x, y, h) in the detection area in the coal pile through a linear combination of P Markov radial basis functions.

[0115] After completing the establishment of the forward problem of the three-dimensional wave velocity field inversion in the coal pile, it is also necessary to solve its inverse problem. The inverse problem of the three-dimensional wave velocity field inversion in the coal pile is to solve the wave velocity distribution of the shock wave in the detector area in the coal pile when the spatial position information of the shock wave receiving sensor and the source and the multi-path sound of the shock wave are known.

[0116] At the same time, since the inverse problem of the three-dimensional velocity field of the shock wave is ill-posed, singular value decomposition (SVD) and Tikhonov regularization are needed to overcome the ill-posedness of the inverse problem. The singular value decomposition of the matrix b is as follows:

[0117] bv i =δ i u i , b T u i =δ i v i

[0118] Among them, δ i are the singular values ​​of matrix b, u i is the left singular value vector of matrix b, v i is the right singular value vector of matrix b.

[0119] If the rank of matrix b is R(b) = e, then there exist orthogonal matrices U and V such that the singular value decomposition of matrix b is as follows:

[0120]

[0121] Among them, Σ=diag(δ1,δ2,...,δ e ), the singular values ​​of matrix b are δ1≥δ2≥...δ e > 0. Therefore, the pseudo-inverse of matrix b can be expressed as:

[0122]

[0123] Among them, Σ -1 =diag(1 / δ1,1 / δ2,...,1 / δ e ).

[0124] From the above, we can see that the least squares solution of the inverse problem of the three-dimensional wave velocity field inversion in the coal pile can be expressed as:

[0125]

[0126] β represents the least square solution of the inverse problem of the three-dimensional wave velocity field inversion in the coal pile;

[0127] e represents the number of layers of the matrix rank;

[0128] δ i represents the i-th singular value of matrix b;

[0129] Indicates u i The transpose of u i Represents the left singular value vector of matrix b;

[0130] v i represents the right singular value vector of matrix b;

[0131] t represents the acoustic time vector.

[0132] In order to avoid the ill-posedness of the inverse problem, which causes many approximate zero values ​​in the singular values ​​of the coefficient matrix b and amplifies the noise in the acoustic time vector, Tikhonov regularization is used to deal with the ill-posedness of the inverse problem. By using the prior knowledge represented by the square of the 2-norm of β and determining the regularization parameter λ through the L-curve method, the regularized solution is used as the approximate solution of the inverse problem of the three-dimensional wave velocity field in the coal pile:

[0133]

[0134] (b T b+λI)β=b T t

[0135]

[0136] Among them, the regularization parameter λ>0, I is the unit matrix.

[0137] After obtaining the three-dimensional wave velocity field of the detection area in the coal pile, the temperature information of the detection area of ​​the coal pile is determined according to the relationship between wave velocity and temperature. The calculation steps of wave velocity and coal temperature are as follows.

[0138] Based on the fact that the wave velocity in the propagation medium is the first function of the absolute temperature of the medium, the internal temperature or temperature field information of the medium in the detected area is obtained.

[0139]

[0140] Where: c e is the wave velocity, m / s; y is the ratio of the specific heat capacity at constant pressure to the specific heat capacity at constant volume of the gas medium; R is the gas constant, usually 8.314 J / (mol·K); T is the absolute thermodynamic temperature, unit K; q is the gas molecular weight, unit kg / mol. Take a constant value. The specific confirmation method is to construct a small-sized coal pile to be measured, and use the previous experimental test to determine the relationship between the sound velocity and temperature of the small coal pile.

[0141]

[0142] According to the above formula and the three-dimensional wave velocity field calculated previously, the three-dimensional temperature field information of the detection area in the coal pile can be obtained.

[0143] By drawing an image based on the temperature information and the spatial temperature information of the coal pile, the three-dimensional spatial temperature conditions inside the coal pile can be visualized.

[0144] In the above process, by taking a constant for the Z value, the calculation inversion of the coal pile temperature can be realized. It can be seen from the above formula that the Z value plays an important role in the conversion process of the vibration wave velocity to the temperature of each area of ​​the coal pile, and directly affects the inversion result of the coal pile temperature. However, during the spontaneous combustion of the coal pile, the temperature of the coal pile will change, and the temperature distribution of the coal body is not uniform. For different types of coal, the medium is also different. Therefore, in fact, the above Z value is somewhat different. For this point, a further solution improvement is to obtain a more accurate temperature by correcting the Z value of the wave velocity temperature mapping function. The specific operation is to conduct multiple small-scale coal pile heating experiments of the same type of coal to determine the relationship between the coal pile temperature and the medium, and then obtain a more accurate Z value, thereby improving the accuracy of the wave velocity to temperature mapping, and thus obtaining a more accurate three-dimensional temperature field in the coal pile detection area.

[0145] S5. When the temperature of the coal pile is too high, a high temperature alarm will be sounded.

[0146] The monitoring software of the vibration wave data analysis and processing host can realize functions such as historical temperature query and high temperature alarm. By selecting the detection area and calling the stored detection temperature data, the historical temperature change function of different areas can be realized; Fig.12 As shown, the high temperature alarm temperature T is set by computer software A When there is an abnormally high temperature area inside the coal pile, the temperature field inside the coal pile obtained by real-time monitoring is used to determine whether the temperature T at each location is greater than the preset high temperature alarm temperature T A , when T>T A, it is determined that the point belongs to the abnormal high temperature area, and the temperature of the surrounding area is determined until the temperature of the position is less than the high temperature alarm temperature. After the judgment is completed, all the internal positions of the coal pile determined to belong to the abnormal high temperature area are marked in the three-dimensional multi-layer isotherm diagram, indicating the position of the high temperature area and alarming. In addition, in view of the possible errors in the temperature field reconstruction process, which may lead to the undiscovery of the possible high temperature area, the host can realize the discrimination of the suspicious high temperature area through the auxiliary discrimination function. The host monitors the acoustic time data of the coal pile collected by the base station in real time. When there is a temperature rise in some areas in the coal pile detection area, the wave velocity of the vibration wave measurement line passing through the area will change, resulting in changes in the acoustic time. By monitoring the acoustic time data of each vibration wave transmission path, if the acoustic time data continues to decrease in multiple cycles, the area is divided into a suspicious high temperature area. The high temperature alarm function is realized by combining the above-mentioned high temperature abnormal area delineation based on temperature field inversion and the auxiliary discrimination function based on acoustic time change. Through the above-mentioned real-time monitoring, high temperature early warning and other functions, the monitoring and positioning of the abnormal high temperature area inside the coal pile is realized, so as to take timely measures to prevent spontaneous combustion inside the coal pile.

[0147] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for monitoring and early warning of abnormal temperature areas in coal piles, characterized in that: include: S1, drilling a hole in the ground for stacking coal, and placing a vibration wave receiving sensor in the hole; S2, arranging the shock wave source on the outer surface of the coal pile; S3, collecting vibration wave signal data; S4, after collecting one cycle, the n vibration wave receiving sensors receive the signal data of the vibration waves emitted by the m seismic sources, and transmit the vibration wave signal data to the vibration wave data analysis and processing host; the data analysis and processing host performs real-time analysis and processing on the monitoring data, converts the vibration wave signal into temperature, and issues an early warning based on the temperature; The data analysis and processing host performs real-time analysis and processing on the monitoring data, converts the vibration wave signal into temperature, and issues an early warning based on the temperature. The steps include: (1) First, the interior of the coal pile is divided into several spatial regions according to the positions of the shock wave source and the shock wave receiving sensor, and the detection area is divided into uniform grid points; (2) For each grid point, determine the propagation paths from the earthquake source to that point and measure the propagation time of the shock waves along these paths; (3) Based on the measured propagation time and propagation path length, the wave velocity at each grid point is calculated; then, based on the relationship between the wave velocity and temperature, the temperature of each temperature point in the coal pile area is obtained; (4) determining whether the difference between the lowest temperature point and the highest temperature point in the grid points is greater than a first temperature difference; if so, indicating that a first degree of temperature difference exists in the grid points, the grid size is reduced until the difference between the lowest temperature point and the highest temperature point in the grid points is less than the first temperature difference; Then, it is determined whether the difference between the lowest temperature point and the highest temperature point in the grid point is greater than the second temperature difference. The first temperature difference is greater than the second temperature difference. If it is greater, it means that there is a second degree of temperature difference in the grid point. In order to effectively prevent local high temperature, the highest temperature in the grid point is used as the temperature value of the grid point. If it is less than, the average temperature of each point in the grid point is used as the temperature value of the grid point. (5) The temperature data of all grid points are integrated to form a three-dimensional temperature field; if the temperature of a grid point is higher than the set high temperature alarm temperature T A , it is judged as a local high temperature area.

2. A method for monitoring and early warning of abnormal temperature areas of coal piles according to claim 1, characterized in that: A hollow metal protective net is installed at the top of the drill hole to protect the shock wave receiving sensor.

3. The method for monitoring and early warning of abnormal temperature areas of coal piles according to claim 1, characterized in that: Arranging the shock wave sources on the outer surface of the coal pile: arranging the shock wave sources on the first layer, the second layer and the top of the coal pile respectively, the first layer is at a vertical height of 1 / 3H of the coal pile relative to the ground, the second layer is at a vertical height of 2 / 3H of the coal pile relative to the ground, and the third layer is at the top of the coal pile, the numbers of shock wave sources arranged at the three levels are m1, m2, and m3 respectively, and the shock wave sources at each level are evenly arranged in a ring shape on the surface of the coal pile at that level; The jth earthquake source at the i-th level is represented by E i-j To express; The seismic source of each layer periodically emits shock waves in sequence at short time intervals. The shock waves penetrate the coal pile and are received by n enabled shock wave receiving sensors arranged on the ground of the coal pile, where n is the number of shock wave receiving sensors enabled according to the detection purpose.

4. A method for monitoring and early warning of abnormal temperature areas of coal piles according to claim 1, characterized in that: Collect shock wave signal data, including: S3-1, the source emits shock waves; S3-2, the shock wave penetrates the coal pile and is received by n shock wave receiving sensors activated on the ground of the coal pile; S3-3, collect the shock wave signals received by each shock wave receiving sensor, and record the wave signal data of the corresponding source and the corresponding sensor, marked as S i-j-x-y .

5. The method for monitoring and early warning of abnormal temperature areas of coal piles according to claim 1, characterized in that: The wave velocity at each grid point is calculated based on the measured propagation time and propagation path length; then, the temperature of each temperature point in the coal pile area is obtained based on the relationship between the wave velocity and the temperature; including: Assume that the inverse distribution of the wave velocity in the detection area is f(x,y,h), then the vibration wave propagation path S i-j-x-y The propagation time t i-j-x-y It can be expressed as: Among them, ds is the integral differential element of the propagation path length of the shock wave; S i-j-x-y The source E i-j To the shock wave receiving sensor R x-y the distance of this propagation path; t i-j-x-y From the source E i-j Transmit shock waves to shock wave receiving sensor R x-y The time it takes to receive the shock wave; Therefore, the inverse wave velocity distribution f(x, y, h) in the detection area within the coal pile can be expressed as: P represents the total number of divided grids; β p It represents the inverse distribution of wave velocity in the coal pile; represents the inverse approximation function of the wave velocity of the pth grid; e is the rank of matrix b, which is the set of integrals of P radial basis functions over S propagation paths; θ represents the shape parameter of the radial basis function; (x, y, h) represent the spatial coordinates in the coal pile; (x p ,y p ,h p ) represents the spatial coordinates of the center point of the pth grid; After obtaining the three-dimensional wave velocity field of the detection area in the coal pile, the temperature information of the detection area of ​​the coal pile is determined according to the relationship between wave velocity and temperature: Where T represents the temperature of each temperature point in the coal pile area; c e is the wave velocity value of the three-dimensional wave velocity field in the detection area within the coal pile; y is the ratio of the specific heat capacity at constant pressure to the specific heat capacity at constant volume of the gas medium; R represents the gas constant; q represents the molecular weight of the gas.

6. The method for monitoring and early warning of abnormal coal pile temperature areas according to claim 1, characterized in that: The data analysis and processing host performs real-time analysis and processing of monitoring data, including: Since different areas of the coal pile have different effects on the overall temperature of the coal pile, the overall temperature of the coal pile is calculated in the following way: Where T represents the overall temperature of the coal pile; T 1i , T 2i , T 3i , T 4i Represent the temperature of the i-th grid point in the center area, bottom area, edge area, and general area respectively; w i is the weight coefficient of the i-th grid point; α and β are the correction coefficients of the grid points in the center area and the grid points in the bottom area, respectively, both of which are greater than 1; χ is the correction coefficient of the grid points in the edge area, which is less than 1; L1, L2, L3, and L4 are the number of grid points in the center area, bottom area, edge area, and general area, respectively.

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