Method for visualizing mesoscale determination of spontaneous combustion of loose coal and experimental device thereof

Abstract

The application discloses a mesoscale judging method for visualizing spontaneous combustion of loose coal and an experimental device thereof, and the method comprises the following steps: obtaining images in the process of spontaneous combustion of the coal and pre-processing, intercepting a single loose coal cluster in the pre-processed images, segmenting the single loose coal cluster to obtain a plurality of regions, merging the obtained regions according to ranks, finally calculating a fractal dimension of the loose coal, and determining a representative volume element scale of the loose coal under the mesoscale based on the fractal dimension of the loose coal. The application provides the mesoscale judging method for visualizing spontaneous combustion of loose coal and the experimental device thereof, solves the problem that the prior art is difficult to realize the research on the spontaneous combustion process of the coal under the mesoscale, realizes the analysis on the spontaneous combustion process of the loose coal under the mesoscale, and is favorable for the research on the spontaneous combustion characteristics and the mesoscale mechanism of the loose coal.

Description

Technical Field

[0001] This invention relates to the field of spontaneous combustion experiments on coal, specifically to a method and experimental apparatus for visualizing spontaneous combustion of loose coal bodies at the mesoscopic scale. Background Technology

[0002] Coal spontaneous combustion is a self-accelerating exothermic oxidation reaction. Oxygen molecules form physical and chemical adsorption heat on the coal surface, causing the coal temperature to rise slowly and releasing a large amount of reaction heat. This heat accumulates inside the coal, eventually leading to spontaneous combustion. This process is accompanied by complex physicochemical changes and poses serious hazards to the environment and human health. Loose coal, as a porous and heterogeneous medium, is widely used in experimental research on coal spontaneous combustion due to its easy spontaneous combustion characteristics. Current experimental research on coal spontaneous combustion mainly focuses on easily monitorable characteristics at the macroscopic scale (temperature, gas) and microscopic scale (functional groups, etc.), such as the temperature distribution characteristics in the high-temperature region of coal spontaneous combustion, the concentration changes of indicator gases, and the interconversion of functional groups. These characteristics can all be monitored using existing technologies.

[0003] However, the migration process of spontaneous coal combustion exhibits multi-scale characteristics and strong heterogeneity. Current research on spontaneous coal combustion mainly focuses on microscopic and macroscopic scales, with little exploration at the mesoscopic scale. This hinders the study of the spontaneous combustion characteristics and mesoscopic mechanisms of loose coal bodies. Furthermore, spontaneous coal combustion is a complex, multi-factor coupled process. The occurrence, development, and evolution of pores and fissures, as well as abrupt changes in morphology, can significantly affect temperature, gases, and functional groups. Previous studies have used indirect methods such as taking local coal samples from experimental furnaces at specific temperatures to observe fissures. This method has the problem that abrupt changes in temperature and fissures before and after monitoring lead to large errors in the experimental data. Summary of the Invention

[0004] This invention provides a method and experimental apparatus for visualizing the mesoscopic scale determination of spontaneous combustion of loose coal, which solves the problem that existing technologies are difficult to study the spontaneous combustion process of coal at the mesoscopic scale. It realizes the analysis of the spontaneous combustion process of loose coal at the mesoscopic scale, which is beneficial to the study of the spontaneous combustion characteristics and mesoscopic mechanism of loose coal.

[0005] This invention is achieved through the following technical solution:

[0006] Methods for determining the mesoscale of spontaneous combustion in visualized loose coal bodies include:

[0007] S1. Acquire images of the coal spontaneous combustion process and preprocess the images;

[0008] S2. Extract a single loose coal mass from the preprocessed image, and segment the single loose coal mass to obtain several regions;

[0009] S3. Merge the resulting regions according to their rank;

[0010] S4. Calculate the fractal dimension of loose coal seams;

[0011] S5. Based on the fractal dimension of loose coal body, determine the characterization volumetric scale of loose coal body at the mesoscale.

[0012] To address the difficulty in conducting mesoscale studies of coal spontaneous combustion processes in existing technologies, this invention first proposes a method for visually determining the mesoscale of loose coal spontaneous combustion. This method first acquires images of the coal spontaneous combustion process through visualization and preprocesses them. Preprocessing techniques can include commonly used image processing methods such as enhancement, denoising, clustering, cropping, edge detection, or grayscale conversion, which are not limited here. This method then extracts individual loose coal aggregates from the preprocessed images and segments these aggregates. Based on the segmentation results, several regions are obtained. Considering that segmentation of individual loose coal aggregates may lead to some oversegmented small regions in the image, this method uses rank-based merging to merge these oversegmented regions. The fractal dimension of the loose coal body can then be calculated, and the volumetric scale of the loose coal body at the mesoscale is determined based on the obtained fractal dimension.

[0013] It can be seen that this method can effectively define the characterization volumetric scale of spontaneous combustion of loose coal at the mesoscale, solve the problems of determining the mesoscale region and defining the characterization volumetric scale of spontaneous combustion of loose coal, fill the gap in the existing technology, and is of great significance to the study of spontaneous combustion characteristics and mesoscale mechanism of loose coal.

[0014] Furthermore, methods for merging the obtained regions by rank include:

[0015] S301. Obtain the grayscale image of each loose coal mass agglomeration in the preprocessed image; that is, obtain the grayscale image of each region.

[0016] S302. Treat the grayscale image as an undirected graph and calculate the grayscale difference of each undirected edge;

[0017] S303. Sort the undirected edges in ascending order according to their grayscale difference;

[0018] S304. According to the obtained sorting, starting from the undirected edge with the smallest sorting value, find the two vertices of the undirected edge.

[0019] S305. Determine whether the two vertices of the undirected edge satisfy the merging condition: if so, merge the regions corresponding to the two vertices of the undirected edge; wherein, the merging condition is:

[0020] ;

[0021] In the formula: C1 and C2 are the regions corresponding to the two vertices respectively, size(C1) is the size of region C1, size(C2) is the size of region C2, and β is a specified value.

[0022] The value of β is set adaptively according to the specific working conditions, and is not limited here.

[0023] Furthermore, methods for calculating the fractal dimension of loose coal bodies include:

[0024] S401. Select the fractal scale size M×M of the loose coal body, regard the selected loose coal body surface as a function coordinate in three-dimensional space, and perform meshing on the selected loose coal body surface.

[0025] S402. Based on the results of the gridding process, take the logarithm of the number of grid cell scales to obtain the fractal dimension of the loose coal body in the M×M region.

[0026] The grid cell size is:

[0027] ;

[0028] In the formula: L n n is the grid cell size; n is the grid side length.

[0029] The fractal dimension of the loose coal body within the M×M region is calculated using the following formula:

[0030] ;

[0031] In the formula: D(M×M) is the fractal dimension of the loose coal body within the M×M region; N r For a pixel to fall within the grid cell scale L n The quantity within.

[0032] Furthermore, methods for determining the volumetric scale of loose coal bodies at the mesoscale include:

[0033] S501. Select different M×M values ​​in sequence to obtain the fractal dimension at different grid unit scales; where M∈(1,C), and C is the scale of the original image region;

[0034] S502. Based on different fractal dimensions under different M×M, plot the relationship curve between grid cell size and fractal dimension;

[0035] S503. Select the fractal dimension of the changing region in the relationship curve that is in a stable stage as the fractal dimension, and use the grid cell scale corresponding to the fractal dimension as the volumetric scale.

[0036] The M×M dimensions can be selected sequentially from smallest to largest or from largest to smallest.

[0037] This application also proposes a mesoscopic-scale experimental apparatus for visualizing spontaneous combustion of loose coal, comprising:

[0038] The reaction system is used for the spontaneous combustion reaction of coal.

[0039] An air intake system is used to supply air to the reaction system;

[0040] The control system is used to control the pressure and ambient temperature of the coal inside the reaction system.

[0041] The monitoring system is used to monitor the gas concentration and temperature during the spontaneous combustion process of coal in the reaction system, and to acquire images of the spontaneous combustion process of coal.

[0042] A data processing system is used to execute the mesoscale determination method for visualizing spontaneous combustion of loose coal in this application.

[0043] In operation, this device involves loading loose coal into the reaction system and introducing the necessary gas for the spontaneous combustion experiment through the gas intake system. The control system regulates the temperature and pressure within the reaction system, inducing spontaneous combustion of the loose coal. A monitoring system tracks the gas concentration and temperature during the combustion process and acquires images of the combustion process. Finally, a data processing system processes the monitoring data and applies a mesoscopic scale determination method for visualizing loose coal combustion, providing real-time volumetric representations of the spontaneous combustion at the mesoscopic scale. This device can dynamically track and display the mesoscopic volumetric representations of coal combustion, facilitating the study of the complete mesoscopic process and significantly improving the feasibility of researching the characteristics and mesoscopic mechanisms of loose coal combustion.

[0044] Furthermore, the reaction system includes a tank, a heating ring located on the outer side of the lower wall of the tank, a monitoring hole and a viewing window opened on the side wall of the tank, a pressure flange located at the top of the tank, and a flange cover located above the pressure flange; a piston is slidably fitted inside the pressure flange, the bottom of the piston is connected to the pressure base, and a displacement sensor for monitoring the displacement of the piston is also included; a hydraulic inlet and a hydraulic outlet are opened on the side of the pressure flange above the piston.

[0045] This solution uses a hydraulic inlet to introduce high-pressure liquid, which drives the piston to slide downwards, thereby driving the pressure-applying chassis to move downwards synchronously, thus applying pressure to the loose coal inside the tank. The tank is heated as a whole from the outside of the lower wall through a heating ring. The temperature and gas concentration of the coal and reaction products during the spontaneous combustion process are monitored through monitoring holes. The piston displacement is recorded by a displacement sensor, which is more conducive to the control of the applied pressure.

[0046] This method employs hydraulic pressurization to apply pressure to the target coal sample, solving the problems of bulky and limited pressure range associated with traditional mechanical pressurization equipment, thus reducing experimental costs and equipment scale. Furthermore, the use of a heating ring to externally heat the coal sample allows for phased and uniform heating, avoiding the excessively rapid and uneven heating effects associated with peak-heating equipment such as heating rods, and better simulating the spontaneous combustion of coal under real-world conditions.

[0047] Furthermore, the air intake system includes a gas cylinder and an air inlet on the cylinder body. A pressure reducing valve, a pressure regulating valve, and a flow controller are connected sequentially between the gas cylinder and the air inlet. This air intake system allows for precise measurement and control of gas flow.

[0048] Furthermore, the control system includes a booster oil pump and a temperature controller; the output and input ends of the booster oil pump are connected to the hydraulic inlet and hydraulic outlet, respectively; the temperature controller is used to control the heating ring.

[0049] Furthermore, the monitoring system includes a laser gas detection device and a temperature detection device connected to the monitoring port, as well as an image acquisition device facing the viewing window; the data processing system includes a processor and a display connected by signals.

[0050] This solution utilizes laser gas detection equipment and temperature detection equipment to monitor the gas concentration and temperature of a designated area in real time, providing auxiliary reference for workers to understand the coal spontaneous combustion process. Simultaneously, image acquisition equipment captures real-time images of the spontaneous combustion process inside the tank from a viewing window, obtaining the required images of the coal spontaneous combustion process. The processor processes the data monitored by the system, and the display shows the processed parameters in real time.

[0051] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0052] 1. The present invention provides a method and experimental apparatus for visualizing the mesoscopic scale determination of spontaneous combustion of loose coal, which can effectively define the characterization volumetric scale of spontaneous combustion of loose coal at the mesoscopic scale. It solves the problems in the determination of the mesoscopic scale region and the definition of the characterization volumetric scale of spontaneous combustion of loose coal, and is of great significance to the study of the characteristics and mesoscopic mechanism of spontaneous combustion of loose coal.

[0053] 2. The mesoscopic scale determination method and experimental apparatus for visualizing spontaneous combustion of loose coal in this invention significantly improves the stability, reliability and accuracy of experimental results of spontaneous combustion experiments of loose coal under high pressure, high temperature and visualization.

[0054] 3. The present invention provides a method for determining the mesoscopic scale of spontaneous combustion of loose coal and its experimental apparatus. The method uses hydraulic pressurization to apply pressure to the target coal sample, which solves the problems of bulky and small pressure range of traditional mechanical pressurization equipment, and reduces the experimental cost and equipment scale.

[0055] 4. The mesoscopic scale determination method and experimental device for visualizing spontaneous combustion of loose coal in this invention can uniformly heat the coal sample in stages, avoiding the effects of excessively rapid heating and uneven heating caused by heating equipment such as heating rods with peak heating, and better simulating the spontaneous combustion of coal under real environment. Attached Figure Description

[0056] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0057] Figure 1 This is a schematic diagram of a specific embodiment of the present invention;

[0058] Figure 2 This is an original image of the coal spontaneous combustion process in a specific embodiment of the present invention;

[0059] Figure 3 The image shown is a preprocessed image in a specific embodiment of the present invention;

[0060] Figure 4 This is a schematic diagram illustrating the determination of the characterization volumetric scale in a specific embodiment of the present invention;

[0061] Figure 5 Connection diagram of a specific embodiment of the present invention;

[0062] Figure 6 A schematic diagram of the reaction system in a specific embodiment of the present invention;

[0063] Figure 7 A cross-sectional view of the reaction system in a specific embodiment of the present invention;

[0064] Figure 8 A schematic diagram of the connection of the view window in a specific embodiment of the present invention.

[0065] The attached diagram shows the markings and corresponding component names:

[0066] 1-Gas cylinder, 2-Pressure reducing valve, 3-Pressure regulating valve, 4-Flow controller, 5-Laser gas detection equipment, 51-Laser emitter, 52-Laser receiver, 6-Temperature detection equipment, 7-Temperature controller, 8-Tank body, 81-Pressure flange, 811-Hydraulic inlet, 812-Hydraulic outlet, 82-Flange cover, 821-Flange cover bolt, 83-Piston, 84-Exhaust port, 85-Displacement sensor, 86-O-ring, 87-Pressure base, 88-Fixing flange, 881-Boss, 882-Fixing flange 883-Flange I, 884-Flange II, 89-Viewing window, 891-Groove, 90-Heating ring, 91-Air inlet, 911-Guide disc, 912-Guide hole, 92-Monitoring hole, 93-Loose coal body, 94-Image acquisition device, 10-Boost oil pump, 101-First valve, 102-Second valve, 11-Data acquisition card, 12-Display, 121-Pressure display module, 122-Temperature display module, 123-Gas display module, 124-Image display module. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0068] Example 1:

[0069] like Figure 1 The method for determining the mesoscale of spontaneous combustion of loose coal shown includes:

[0070] S1, obtain as follows Figure 2 The image of the spontaneous combustion process of coal shown is preprocessed to obtain the following result: Figure 3 The image shown is the preprocessed image.

[0071] S2. Extract a single loose coal mass from the preprocessed image, and segment the single loose coal mass to obtain several regions.

[0072] S3. Merge the resulting regions according to their rank. Specific merging methods include:

[0073] S301. Obtain the grayscale image of each loose coal mass agglomeration in the preprocessed image;

[0074] S302. Treat the grayscale image as an undirected graph and calculate the grayscale difference of each undirected edge;

[0075] S303. Sort the undirected edges in ascending order according to their grayscale difference; e.g., e0, e1, e2, e3, ..., e ∞ ;

[0076] S304. According to the obtained sorting, starting from the undirected edge e0 with the smallest sorting, find the two vertices of the undirected edge.

[0077] S305. Determine whether the two vertices of the undirected edge satisfy the merging condition: if so, merge the regions corresponding to the two vertices of the undirected edge; wherein, the merging condition is:

[0078] ;

[0079] In the formula: C1 and C2 are the regions corresponding to the two vertices respectively, size(C1) is the size of region C1, size(C2) is the size of region C2, and β is a specified value.

[0080] S4. Calculate the fractal dimension of loose coal bodies; specific calculation methods include:

[0081] S401. Select the fractal scale size M×M of the loose coal body, and regard the selected loose coal body surface as a function coordinate (x, y, f(x, y)) in three-dimensional space, where x and y are the X-axis and Y-axis coordinates of the image pixel point, and f(x, y) is the gray value of the image pixel point (x, y). Perform meshing processing on the selected loose coal body surface.

[0082] S402. Based on the results of the gridding process, take the logarithm of the number of grid cell scales to obtain the fractal dimension of the loose coal body in the M×M region.

[0083] The grid cell scale is as follows:

[0084] ;

[0085] In the formula: L n n is the grid cell size; n is the grid side length.

[0086] The fractal dimension of the loose coal body within the M×M region is calculated using the following formula:

[0087] ;

[0088] In the formula: D(M×M) is the fractal dimension of the loose coal body within the M×M region; N r For a pixel to fall within the grid cell scale L n The quantity within.

[0089] S5. Based on the fractal dimension of loose coal, the volumetric scale representing loose coal at the mesoscale is determined using the following method:

[0090] S501. Select different M×M values ​​in sequence to obtain the fractal dimension at different grid unit scales; where M∈(1,C), and C is the scale of the original image region;

[0091] S502. Based on different fractal dimensions under different M×M scales, plot the relationship curve between grid cell size and fractal dimension, such as... Figure 4 As shown;

[0092] S503. Select the fractal dimension of the stable phase in the changing region of the relationship curve as the fractal dimension, and use the grid cell scale corresponding to the fractal dimension as the volumetric scale; corresponding to... Figure 4 In this context, the middle region along the horizontal axis is used as the mesoscopic scale. The corresponding fractal dimension of this region is in the range of 2.04 to 2.11, and the corresponding voxel scale is 10⁵ to 360.

[0093] Example 2:

[0094] The mesoscopic-scale determination method for visualizing spontaneous combustion of loose coal is based on Example 1. This example employs an improved GBIS clustering algorithm to segment individual loose coal agglomerations. The GBIS algorithm abstractly represents the image as a weighted undirected graph, where each pixel represents a vertex. Pixels are connected by undirected edges, and the values ​​of these edges describe the similarity between pixels, i.e., their weights. The GBIS algorithm generates multiple regions to segment individual loose coal bodies, ensuring that pixels within the same region are similar, while pixels in different regions are dissimilar.

[0095] The GBIS algorithm also performs pre-merging on the segmented individual loose coal seam regions. The pre-merging method uses rank merging and path compression criteria. Rank merging connects the lower-level spanning tree to the higher-level spanning tree in the two minimum spanning trees. Path compression connects the top-level node of the lower-level tree to the top-level node / parent node of the higher-level tree. Specific merging conditions are as follows:

[0096] ;

[0097] In the formula: P max P represents the maximum pixel value within a single loose coal mass agglomeration. min γ represents the minimum pixel value within a single loose coal mass cluster; γ is a set threshold.

[0098] Example 3:

[0099] A mesoscopic-scale experimental apparatus for visualizing spontaneous combustion of loose coal, such as... Figures 5 to 7 As shown, it includes:

[0100] The reaction system is used for the spontaneous combustion reaction of coal.

[0101] An air intake system is used to supply air to the reaction system;

[0102] The control system is used to control the pressure and ambient temperature of the coal inside the reaction system.

[0103] The monitoring system is used to monitor the gas concentration and temperature during the spontaneous combustion process of coal in the reaction system, and to acquire images of the spontaneous combustion process of coal.

[0104] A data processing system for performing the determination method as described in Example 1 or 2.

[0105] In this embodiment, the reaction system includes a tank 8, a heating ring 90 located on the outer side of the lower wall of the tank 8, a monitoring hole 92 and a viewing window 89 opened on the side wall of the tank 8, a pressure flange 81 located at the top of the tank 8, and a flange cover 82 located on the pressure flange 81; a piston 83 is slidably fitted inside the pressure flange 81, and the bottom of the piston 83 is connected to a pressure base 87, and a displacement sensor 85 for monitoring the displacement of the piston 83 is also included; a hydraulic inlet 811 and a hydraulic outlet 812 are opened on the side of the pressure flange 81 above the piston 83.

[0106] In this embodiment, the air intake system includes a gas cylinder 1 and an air inlet 91 opened on the tank body 8. A pressure reducing valve 2, a pressure regulating valve 3, and a flow controller 4 are connected in sequence between the gas cylinder 1 and the air inlet 91.

[0107] In this embodiment, the control system includes a booster oil pump 10 and a temperature controller 7; the output end and input end of the booster oil pump 10 are connected to the hydraulic inlet 811 and the hydraulic outlet 812, respectively; the temperature controller 7 is used to control the heating ring 90.

[0108] In this embodiment, the monitoring system includes a laser gas detection device 5 and a temperature detection device 6 connected to the monitoring port 92, and an image acquisition device 94 facing the viewing window 89; the data processing system includes a processor 11 and a display 12 connected by signals. The image acquisition device 94 preferably uses a high-definition image acquisition instrument.

[0109] Preferably, the top of the piston 83 may have an exhaust port 84 for communicating with the inside of the tank 8, and the laser gas detection device 5 and the temperature detection device 6 may also monitor the gas concentration and temperature at the exhaust port 84.

[0110] Preferably, the booster pump 10 is connected to a first valve 101 and a second valve 102, which are respectively connected to the hydraulic inlet 811 and hydraulic outlet 812 of the pressure flange 81 on the upper part of the tank body 8, for pressurizing the loose coal mass 93.

[0111] The working process of this embodiment includes:

[0112] Step 1: After crushing the coal sample with a jaw crusher, analyze the particle size distribution of the coal sample and check the airtightness and accuracy of the experimental equipment.

[0113] Step 2: After crushing and screening the coal sample, the coal sample after particle size distribution analysis is loaded into the tank 8. The spatial position of the coal sample at the top of the loose coal body 93 is adjusted by the pressure base plate 87 and piston 83, and the displacement sensor 85 records the current position.

[0114] Step 3: Secure the flange cover 82 and the pressure flange 81 to the tank body 8 using the flange cover bolts 821 on the top of the flange cover 82;

[0115] Step 4: Connect the air intake system's connecting pipe to the air inlet 91 of the tank 8; connect the heating ring 90 to the temperature controller 7 of the control system; connect the hydraulic inlet 811 and hydraulic outlet 812 of the tank 8 to the first valve 101 and the second valve 102 of the booster oil pump 10, respectively; insert the detection probes of the laser gas detection device 5 and the temperature detection device 6 into the designated positions inside the monitoring hole 92, while maintaining connection with the exhaust port 84; adjust the height and position of the image acquisition device 94, and set the autofocus range.

[0116] Step 5: Open gas cylinder 1, pressure reducing valve 2, and pressure regulating valve 3. Control the flow rate through flow controller 4 so that the gas enters the loose coal body 93 through the air inlet 91 at the bottom of tank 8 under controlled conditions. At the same time, the temperature controller 7 starts to control the tank 8 to heat up in stages, and the image acquisition device 94 and displacement sensor 85 start to record data.

[0117] Step 6: The gas reacted inside the tank 8 enters the flue of the laser gas detection device 5 through the exhaust port 84 and the monitoring hole 92. The laser emitted by the semiconductor laser emitter 51 passes through the gas to be tested through the sensing probe and is projected onto the laser detector of the receiving unit. The laser receiver 52 transmits the weakened laser electrical signal to the emitting unit through the photoelectric converter. The data processing system built into the emitting unit calculates the concentration of the gas to be tested.

[0118] Step 7: The image acquisition device 94 controls the current generated by the photodiode through the control signal circuit in the photosensitive element to excite and release the charge. The current is output by the current transmission circuit. The image acquisition device will collect the electrical signals generated by the single imaging and output them to the amplifier. After amplification and filtering, the electrical signals are converted into digital signals.

[0119] Step 8: The data acquisition card 11 in the data processing system automatically acquires the analog or digital signals of the control system and monitoring system into the host computer, and performs analysis and processing steps such as the judgment method in Example 1 or 2. Then, the processed results are transmitted to the display 12, which displays the temperature, gas, crack morphology, characterization volumetric scale, etc. in real time during the dynamic evolution of the spontaneous combustion of the coal sample.

[0120] This embodiment can solve the problems in the prior art such as the unclear definition of the mesoscopic scale of coal spontaneous combustion, the inability to accurately, effectively and in real time monitor the cracks, voids and morphology of high-temperature areas, etc. It can not only control the temperature, pressure and other conventional environmental factors during the spontaneous combustion process of loose coal, but also accurately and effectively monitor the cracks, voids and morphology of high-temperature areas of coal spontaneous combustion in real time.

[0121] Example 4:

[0122] A mesoscopic-scale experimental apparatus for visualizing spontaneous combustion of loose coal, based on Example 3:

[0123] Heating ring 90 is heated by nickel-chromium alloy wire, which has the characteristics of rapid heating and high thermal efficiency. The nickel-chromium alloy wire is in a ring shape and attached to the outer wall of the tank 8 to uniformly heat the tank 8. Heating ring 90 is connected to temperature controller 7 in the control system to control heating characteristics.

[0124] The monitoring hole 92 has a diameter of 9mm and a length of about 30mm. It has internal threads and can be sealed with an M8×30 ​​bolt when not in use.

[0125] An O-ring 86 can be installed between the pressure flange 81 and the tank body 8 to ensure a sealing effect while reducing wear on the pressure flange.

[0126] like Figure 8 As shown, the viewing window 89 is installed on the surface of the tank body through two fixed flanges 88. Each fixed flange is provided with several bolt holes 882. The inner side of the fixed flange 88 is provided with a boss 881 for fitting and fixing with the groove 891 on the outer side of the viewing window 89. In this embodiment, the installation of the viewing window 89 is achieved by the cooperation of flange I 883 and flange II 884 through mortise and tenon connection, which solves the sealing problem between the viewing window 89 and the fixed flange 88.

[0127] Preferably, the viewing window 89 is made of sapphire material, which can withstand a maximum temperature of 1400℃.

[0128] Preferably, the heating controller 7 is equipped with a temperature control backplate 71, which can set the heating rate according to the usage requirements; the heating controller 7 can also be equipped with a voltage regulation module to control heating loads of different voltages; the booster oil pump 10 and the heating controller 7 are respectively connected to the data processing system.

[0129] Preferably, the laser gas detection device 5 includes a laser emitter 51 and a laser receiver 52. This embodiment adopts the single-line spectral measurement principle, which can realize the accurate measurement of the concentration of a single gas between the laser emitter 51 and the laser receiver 52. The laser emitting unit 51 and the laser receiving unit 52 are connected by an optical cable. The single gas includes, but is not limited to, CO2, O2, CH4, etc.

[0130] Preferably, the temperature detection device 6 can use existing temperature sensors such as resistive, current or voltage types.

[0131] Preferably, the data processing system includes a data acquisition card 11 and a display processor 12; wherein, the data acquisition card 11 is used to automatically acquire and analyze the monitoring signals of the device, including to execute the determination method as in Embodiment 1 or 2;

[0132] The input terminal of the data acquisition card 11 is connected to the laser gas detection device 5, the temperature detection device 6, the image acquisition device 94, the booster oil pump 10, and the temperature controller 7. Its output terminal is connected to the display 12. The display 12 includes a pressure display module 121, a temperature display module 122, a gas display module 123, and an image display module 124.

[0133] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the mesoscopic scale of spontaneous combustion in visual loose coal bodies, characterized in that, include: S1. Acquire images of the coal spontaneous combustion process and preprocess the images; S2. Extract a single loose coal mass from the preprocessed image, and segment the single loose coal mass to obtain several regions; S3. Merge the resulting regions according to their rank; methods include: S301. Obtain the grayscale image of each loose coal mass agglomeration in the preprocessed image; S302. Treat the grayscale image as an undirected graph and calculate the grayscale difference of each undirected edge; S303. Sort the undirected edges in ascending order according to their grayscale difference; S304. According to the obtained sorting, starting from the undirected edge with the smallest sorting value, find the two vertices of the undirected edge. S305. Determine whether the two vertices of the undirected edge satisfy the merging condition: if so, merge the regions corresponding to the two vertices of the undirected edge; wherein, the merging condition is: ； In the formula: C1 and C2 are the regions corresponding to the two vertices respectively, size(C1) is the size of region C1, size(C2) is the size of region C2, and β is a specified value; S4. Calculate the fractal dimension of loose coal bodies; methods include: S401. Select the fractal scale size M×M of the loose coal body, regard the selected loose coal body surface as a function coordinate in three-dimensional space, and perform meshing on the selected loose coal body surface. S402. Based on the results of the gridding process, take the logarithm of the number of grid cell scales to obtain the fractal dimension of the loose coal body in the M×M region; The grid cell size is: ； In the formula: L n n is the grid cell size; n is the grid side length. The fractal dimension of the loose coal body within the M×M region is calculated using the following formula: ； In the formula: D(M×M) is the fractal dimension of the loose coal body within the M×M region; N r For a pixel to fall within the grid cell scale L n The quantity within; S5. Based on the fractal dimension of loose coal body, determine the characterization volumetric scale of loose coal body at the mesoscale.

2. The method for determining the mesoscopic scale of spontaneous combustion of loose coal as described in claim 1, characterized in that, Methods for determining the volumetric scale of loose coal bodies at the mesoscale include: S501. Select different M×M values ​​in sequence to obtain the fractal dimension at different grid unit scales; where M∈(1,C), and C is the scale of the original image region; S502. Based on different fractal dimensions under different M×M, plot the relationship curve between grid cell size and fractal dimension; S503. Select the fractal dimension of the changing region in the relationship curve that is in a stable stage as the fractal dimension, and use the grid cell scale corresponding to the fractal dimension as the volumetric scale.

3. An experimental apparatus for visualizing the spontaneous combustion of loose coal at the mesoscopic scale, characterized in that, include: The reaction system is used for the spontaneous combustion reaction of coal. An air intake system is used to supply air to the reaction system; The control system is used to control the pressure and ambient temperature of the coal inside the reaction system. The monitoring system is used to monitor the gas concentration and temperature during the spontaneous combustion process of coal in the reaction system, and to acquire images of the spontaneous combustion process of coal. A data processing system for executing the determination method as described in any one of claims 1 to 2.

4. The experimental apparatus for determining the mesoscopic scale of spontaneous combustion of loose coal as described in claim 3, characterized in that, The reaction system includes a tank (8), a heating ring (90) located on the outer side of the lower wall of the tank (8), a monitoring hole (92) and a viewing window (89) opened on the side wall of the tank (8), a pressure flange (81) located at the top of the tank (8), and a flange cover (82) located on the pressure flange (81); a piston (83) is slidably fitted inside the pressure flange (81), the bottom of the piston (83) is connected to a pressure base (87), and a displacement sensor (85) for monitoring the displacement of the piston (83) is also included; a hydraulic inlet (811) and a hydraulic outlet (812) are opened on the side of the pressure flange (81) located above the piston (83).

5. The experimental apparatus for determining the mesoscopic scale of spontaneous combustion of loose coal as described in claim 4, characterized in that, The air intake system includes a gas cylinder (1) and an air inlet (91) opened on the tank body (8). A pressure reducing valve (2), a pressure regulating valve (3), and a flow controller (4) are connected in sequence between the gas cylinder (1) and the air inlet (91).

6. The experimental apparatus for determining the mesoscopic scale of spontaneous combustion of loose coal as described in claim 4, characterized in that, The control system includes a booster oil pump (10) and a temperature controller (7); the output end and input end of the booster oil pump (10) are connected to the hydraulic inlet (811) and the hydraulic outlet (812) respectively; the temperature controller (7) is used to control the heating ring (90).

7. The experimental apparatus for determining the mesoscopic scale of spontaneous combustion of loose coal as described in claim 4, characterized in that, The monitoring system includes a laser gas detection device (5) and a temperature detection device (6) connected to the monitoring hole (92), and an image acquisition device (94) facing the viewing window (89). The data processing system includes a processor (11) and a display (12) connected by signals.

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