Loose coal and rock mass multi-field coupling test system and method based on in-situ CT

Abstract

The invention provides a loose coal and rock mass multi-field coupling test system and method based on in-situ CT. The system comprises an in-situ reaction device, a CT device, a gas supply device, a gas analysis device and a data acquisition module, wherein the in-situ reaction device is used for filling loose coal rock mass, and a vacuum heat insulation chamber is arranged on the quartz outer wall of the in-situ reaction device; the in-situ reaction device is rotationally arranged in the CT device, and the CT device is used for performing tomography on the loose coal and rock mass and obtaining a structure image of the loose coal and rock mass; the data acquisition module is used for constructing a multi-field coupling evolution model of the loose coal and rock mass based on the temperature of the loose coal and rock mass, the gas product concentration of the loose coal and rock mass and the three-dimensional microstructure of the loose coal and rock mass. According to the loose coal and rock mass multi-field coupling test system and method based on the in-situ CT, temperature isolation inside and outside the in-situ reaction device can be achieved, stable operation of the CT device is guaranteed, and it is also guaranteed that rays can penetrate through the in-situ reaction device.

Description

Technical Field

[0001] This disclosure relates to the field of loose coal and rock mass testing technology, and in particular to a multi-field coupling testing system and method for loose coal and rock mass based on in-situ CT. Background Technology

[0002] During the mining and storage of coal resources, the interior of the coal seam is influenced by the coupled effects of temperature, seepage, and concentration fields. The flow state of gas within the pores of the coal seam, by affecting the heat generation and dissipation rates of the locally accumulated coal, becomes a decisive factor in the spontaneous combustion process. In particular, the porosity, permeability, and thermal conductivity of the coal itself become key regulatory parameters in the gas flow, oxygen diffusion, and heat transfer processes within the coal. Simultaneously, rising ambient temperature not only alters the oxidation reaction rate of the coal but also changes the physicochemical properties of the coal matrix surface, further affecting the pore structure and seepage field of the coal. It is noteworthy that this change is not unidirectional; the structural changes in the coal seam during the heating process also promote the multi-physical fields and the oxidation rate. The heating process of coal inevitably disrupts the original equilibrium system of the seepage, temperature, and concentration fields within the coal seam, inducing the coupled evolution of multi-physical fields and the coal structure. This mutual influence results in a highly nonlinear characteristic of the coal's self-heating process, significantly increasing the difficulty of disaster mechanism analysis and prevention. Therefore, based on a clear understanding of the multi-physical fields and structural laws during the coal heating process, studying the nonlinear dynamic changes of the coal pore network structure and the spatiotemporal evolution of coupled physical fields during the heating and oxidation process, and analyzing the disaster response caused by the multi-physical field coupling effect of coal self-heating, is the core issue in solving coal spontaneous combustion fire accidents in coal mining and storage.

[0003] Currently, most research methods are based on the static assumption of the coal matrix to assess temperature and gas production changes under multiphysics coupling. Since the internal components of CT cannot be exposed to high-temperature environments exceeding 60 degrees Celsius, current research methods can only perform structural scanning and reconstruction on coal samples that have been oxidized and cooled to room temperature, and cannot achieve dynamic scanning of structural changes during the evolution of coal and rock mass. Summary of the Invention

[0004] This disclosure aims to at least partially address one of the technical problems in the related art.

[0005] Therefore, the purpose of this disclosure is to provide a multi-field coupling testing system and method for loose coal and rock masses based on in-situ CT.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a multi-field coupling testing system for loose coal and rock masses based on in-situ CT, comprising: an in-situ reaction device, a CT device, a gas supply device, a gas analysis device, and a data acquisition module; wherein, the in-situ reaction device is used to fill the loose coal and rock mass, and the quartz outer wall of the in-situ reaction device is provided with a vacuum-insulated chamber; the in-situ reaction device is rotatably disposed within the CT device, and the CT device is used for tomographic scanning of the loose coal and rock mass and obtaining structural images of the loose coal and rock mass; the gas supply device's outlet end is connected to the inlet end of the in-situ reaction device, and the gas supply device is used to supply pre-gas to the in-situ reaction device. An oxidizing gas is introduced at a set temperature, gradually raising the temperature of the loose coal and rock mass to a target temperature. The inlet of the gas analysis device is connected to the outlet of the in-situ reaction device, and the gas analysis device is used to detect the concentration of gaseous products in the loose coal and rock mass. The data acquisition module is used to obtain rotational dynamic structural images of the loose coal and rock mass at different temperature stages through the CT device, and to reconstruct the structural images to obtain the three-dimensional microstructure of the loose coal and rock mass at different temperature stages. Based on the temperature, gaseous product concentration, and three-dimensional microstructure of the loose coal and rock mass, a multi-field coupled evolution model of the loose coal and rock mass is constructed.

[0007] Optionally, the in-situ reaction device includes: a reaction chamber, a reaction container, and a top cover; wherein, the reaction container is rotatably disposed within the CT device, and the reaction container is provided with an air inlet groove, the top cover is disposed over the opening of the air inlet groove and the air inlet groove forms an air inlet chamber, the air inlet end of the air inlet chamber is connected to the air outlet end of the gas supply device, the outer wall of the reaction container and the top cover are respectively provided with vacuum insulation chambers; the reaction chamber is disposed within the air inlet chamber, and the reaction chamber is provided with a reaction cavity, the reaction cavity is used to fill the loose coal and rock mass, the bottom of the reaction chamber is provided with a flow equalization plate, the reaction cavity and the air inlet chamber are connected through the flow equalization plate, and the air outlet end of the reaction cavity is connected to the air inlet end of the gas analysis device.

[0008] Optionally, the in-situ reaction device further includes: a heat-insulating base and a heat-insulating cylinder; wherein the heat-insulating base is rotatably disposed within the CT device, and the reaction vessel is disposed on the heat-insulating base; the heat-insulating cylinder is sleeved on the outside of the reaction vessel and the top cover.

[0009] Optionally, the in-situ reaction device further includes: a rotary joint and a conductive slip ring; wherein, the rotor of the rotary joint is disposed on the top cover, and the rotor of the rotary joint is provided with a first air inlet channel, a first air outlet channel, and a wiring harness channel, the air outlet end of the first air inlet channel is connected to the air inlet end of the air inlet chamber, and the air inlet end of the first air outlet channel is connected to the air outlet end of the reaction chamber; the stator of the rotary joint is rotatably sleeved on the rotor of the rotary joint, and the stator of the rotary joint is provided with a second air inlet channel and a second air outlet channel, the air inlet end of the second air inlet channel is connected to the air outlet end of the gas supply device, and the second air inlet channel... The outlet end of the second air outlet channel is arranged circumferentially along the stator and communicates with the inlet end of the first air inlet channel. The outlet end of the second air outlet channel is connected to the inlet end of the gas analyzer. The inlet end of the second air outlet channel is arranged circumferentially along the stator and communicates with the outlet end of the first air outlet channel. The rotor of the conductive slip ring is connected to the rotor of the rotary joint, and the stator of the conductive slip ring is rotatably sleeved on the rotor of the conductive slip ring and connected to the stator of the rotary joint. One end of the wire harness channel is connected to the reaction chamber, and the other end of the wire harness channel passes through the rotor of the conductive slip ring along the axial direction of the rotor of the rotary joint.

[0010] Optionally, the gas supply device includes a gas supply module and a heating module; wherein the gas supply module's outlet is connected to the inlet of the in-situ reaction device, and the gas supply module is used to introduce oxidizing gas into the in-situ reaction device; the heating module is disposed between the gas supply module's outlet and the inlet of the in-situ reaction device, and the heating module is used to heat the oxidizing gas so that the loose coal and rock mass gradually heats up to the target temperature.

[0011] Optionally, the gas supply module includes: a gas source, a pressure reducing valve, a mass flow controller, a one-way valve, a mixing tank, and a first pressure sensor; wherein, the outlet of the gas source is connected to the inlet of the pressure reducing valve, the outlet of the pressure reducing valve is connected to the inlet of the mass flow controller, the outlet of the mass flow controller is connected to the inlet of the one-way valve, the outlet of the one-way valve is connected to the inlet of the mixing tank, the outlet of the mixing tank is connected to the inlet of the in-situ reaction device, the heating module is disposed between the outlet of the mixing tank and the inlet of the in-situ reaction device, and the detection end of the first pressure sensor is disposed at the outlet of the mixing tank; the signal input end of the data acquisition module is connected to the signal output end of the first pressure sensor and the signal output end of the mass flow controller, respectively, and the signal output end of the data acquisition module is connected to the signal input end of the pressure reducing valve and the signal output end of the mass flow controller, respectively.

[0012] Optionally, the heating module includes a heater and a temperature sensor; wherein the heater is disposed between the gas outlet of the gas supply module and the gas inlet of the in-situ reaction device, and the detection end of the temperature sensor is disposed within the in-situ reaction device; the signal input end of the data acquisition module is connected to the signal output end of the temperature sensor, and the signal output end of the data acquisition module is connected to the signal input end of the heater, and the data acquisition module is used to control the heater according to the temperature detected by the temperature sensor, so that the oxidizing gas reaches the preset temperature.

[0013] Optionally, the CT device includes: a protective lead room, a rotating stage, an X-ray source, and a detector; wherein, the rotating stage is disposed inside the protective lead room, and the in-situ reaction device is disposed on the rotating stage, the rotating stage being used to drive the in-situ reaction device to rotate; the X-ray source and the detector are disposed opposite to each other and are respectively located on both sides of the in-situ reaction device, and the signal output terminal of the data acquisition module is connected to the signal input terminal of the X-ray source and the signal input terminal of the rotating stage, respectively, and the signal input terminal of the data acquisition module is connected to the signal output terminal of the detector, the data acquisition module being used to control the rotating stage to rotate at a preset speed, and to perform tomographic scanning of the loose coal and rock mass through the X-ray source and the detector to obtain rotational dynamic structural images of the loose coal and rock mass at different temperature stages.

[0014] Optionally, the gas analysis device includes: a heat tracing pipe, a condenser, a fume hood, a gas chromatograph, and a second pressure sensor; wherein, the inlet end of the first channel of the heat tracing pipe is connected to the outlet end of the in-situ reaction device, and the second channel of the heat tracing pipe is supplied with heat tracing fluid; the inlet end of the first channel of the condenser is connected to the outlet end of the first channel of the heat tracing pipe, and the second channel of the condenser is supplied with condensing fluid; the inlet end of the fume hood is connected to the outlet end of the first channel of the heat tracing pipe; the inlet end of the gas chromatograph is connected to the outlet end of the first channel of the condenser, and the signal output end of the gas chromatograph is connected to the signal input end of the data acquisition module, the data acquisition module being used to obtain the gas product concentration of the loose coal and rock mass through the gas chromatograph; the detection end of the second pressure sensor is located at the outlet end of the first channel of the heat tracing pipe, and the signal output end of the second pressure sensor is connected to the signal input end of the data acquisition module, the data acquisition module being used to obtain the gas pressure at the outlet end of the first channel of the heat tracing pipe through the second pressure sensor.

[0015] The second aspect of this disclosure provides a multi-field coupling testing method for loose coal and rock mass based on in-situ CT, comprising: loading the loose coal and rock mass into an in-situ reaction device within a CT apparatus; connecting the outlet of a gas supply device to the inlet of the in-situ reaction device; and connecting the inlet of a gas analysis device to the outlet of the in-situ reaction device, wherein the quartz outer wall of the in-situ reaction device is provided with a vacuum-insulated chamber; and introducing an oxidizing gas at a preset temperature into the in-situ reaction device through the gas supply device to gradually heat the loose coal and rock mass. The gas product concentration of the loose coal and rock mass is detected by the gas analysis device, and the structural image of the loose coal and rock mass is obtained by tomographic scanning of the loose coal and rock mass using the CT device. The rotational dynamic structural images of the loose coal and rock mass at different temperature stages are reconstructed to obtain the three-dimensional microstructure of the loose coal and rock mass at different temperature stages. Based on the temperature of the loose coal and rock mass, the gas product concentration of the loose coal and rock mass, and the three-dimensional microstructure of the loose coal and rock mass, a multi-field coupled evolution model of the loose coal and rock mass is constructed.

[0016] The technical solution provided in this disclosure may include the following beneficial effects:

[0017] The CT scanner obtains rotating dynamic structural images of loose coal and rock mass at different temperature stages, and reconstructs these images to obtain the three-dimensional microstructure of the loose coal and rock mass at different temperature stages. Furthermore, a multi-field coupled evolution model of the loose coal and rock mass is constructed based on its temperature, gas product concentration, and three-dimensional microstructure. This facilitates the analysis of multi-field coupled disaster-causing mechanisms using the multi-field coupled evolution model. Additionally, the quartz outer wall of the in-situ reaction device and its vacuum-insulated chamber not only achieve temperature isolation between the inside and outside of the in-situ reaction device, ensuring stable operation of the CT scanner, but also ensure that X-rays can penetrate the in-situ reaction device, thus facilitating dynamic scanning of structural changes during the evolution of the coal and rock mass.

[0018] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this disclosure will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which: Figure 1 This is a schematic diagram of the structure of a multi-field coupling testing system for loose coal and rock mass based on in-situ CT, according to an embodiment of this disclosure. Figure 2 This is a schematic diagram of the in-situ reaction device in a multi-field coupling testing system for loose coal and rock mass based on in-situ CT, according to an embodiment of this disclosure. Figure 3 This is a schematic diagram of the rotary joint structure in a multi-field coupling testing system for loose coal and rock mass based on in-situ CT, according to an embodiment of this disclosure. Figure 4 This is a schematic diagram of the CT device in a multi-field coupling testing system for loose coal and rock mass based on in-situ CT, according to an embodiment of this disclosure. Figure 5 This is a schematic diagram of the gas supply device and gas analysis device in a multi-field coupling testing system for loose coal and rock mass based on in-situ CT, according to an embodiment of this disclosure. As shown in the figure: 1. In-situ reaction device, 11. Reaction chamber, 12. Reaction vessel, 13. Top cover, 14. Vacuum insulation chamber, 15. Flow equalization plate, 16. Insulation base, 17. Insulation cylinder, 18. Rotary joint, 181. First air inlet channel, 182. First air outlet channel, 183. Wiring harness channel, 184. Second air inlet channel, 185. Second air outlet channel; 2. CT scanner; 21. Lead-lined protective room; 22. Rotary stage; 23. X-ray source; 24. Detector; 25. Exhaust fan; 3. Gas supply device; 31. Gas source; 32. Pressure reducing valve; 33. Mass flow controller; 34. Check valve; 35. Mixing tank; 36. First pressure sensor; 37. Heater; 38. Temperature sensor. 4. Gas analysis device; 41. Heat tracing pipe; 42. Condenser pipe; 43. Fume hood; 44. Gas chromatograph; 45. Second pressure sensor. 5. Data acquisition module; 51. Computer; 52. Data acquisition card; 6. Loose coal and rock mass. Detailed Implementation

[0020] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are used only to explain this disclosure, and should not be construed as limiting this disclosure. Rather, embodiments of this disclosure include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0021] like Figure 1As shown in the present invention, an embodiment of a multi-field coupling testing system for loose coal and rock mass 6 based on in-situ CT (Computed Tomography) is proposed, comprising: an in-situ reaction device 1, a CT device 2, a gas supply device 3, a gas analysis device 4, and a data acquisition module 5. The in-situ reaction device 1 is used to fill the loose coal and rock mass 6, and a vacuum insulated chamber 14 is provided on the quartz outer wall of the in-situ reaction device 1; the in-situ reaction device 1 is rotatably mounted inside the CT device 2, and the CT device 2 is used for tomographic scanning of the loose coal and rock mass 6 to obtain structural images of the loose coal and rock mass 6; the gas supply device 3 is connected to the gas inlet of the in-situ reaction device 1, and the gas supply device 3 is used to introduce oxidizing gas at a preset temperature into the in-situ reaction device 1 to gradually raise the temperature of the loose coal and rock mass 6 to the target temperature; the gas analysis device 4... The gas end is connected to the gas outlet of the in-situ reaction device 1, and the gas analysis device 4 is used to detect the concentration of gas products in the loose coal and rock mass 6; the data acquisition module 5 is used to obtain the rotational dynamic structure images of the loose coal and rock mass 6 at different temperature stages through the CT device 2, and to reconstruct the structure images to obtain the three-dimensional microstructure of the loose coal and rock mass 6 at different temperature stages, and to construct a multi-field coupled evolution model of the loose coal and rock mass 6 based on the temperature of the loose coal and rock mass 6, the concentration of gas products in the loose coal and rock mass 6, and the three-dimensional microstructure of the loose coal and rock mass 6.

[0022] Since the loose coal and rock mass 6 is filled in the in-situ reaction device 1, and the in-situ reaction device 1 is rotatably installed in the CT device 2, the CT device 2 can perform tomographic scanning on the loose coal and rock mass 6 in the in-situ reaction device 1. Furthermore, since the outlet end of the gas supply device 3 is connected to the inlet end of the in-situ reaction device 1, the gas supply device 3 can introduce oxidizing gas at a preset temperature into the in-situ reaction device 1 and gradually raise the temperature of the loose coal and rock mass 6 to the target temperature. At the same time, since the inlet end of the gas analysis device 4 is connected to the outlet end of the in-situ reaction device 1, the gas analysis device 4 can detect the concentration of gaseous products in the loose coal and rock mass 6.

[0023] Based on this, the CT device 2 obtains rotational dynamic structural images of the loose coal and rock mass 6 at different temperature stages, and reconstructs the structural images to obtain the three-dimensional microstructure of the loose coal and rock mass 6 at different temperature stages. Furthermore, a multi-field coupled evolution model of the loose coal and rock mass 6 is constructed based on the temperature, gas product concentration, and three-dimensional microstructure of the loose coal and rock mass 6. This facilitates the analysis of the multi-field coupled disaster mechanism using the multi-field coupled evolution model. In addition, the quartz outer wall of the in-situ reaction device 1 and the vacuum insulation chamber 14 of the outer wall not only achieve temperature isolation between the inside and outside of the in-situ reaction device 1, ensuring the stable operation of the CT device 2, but also ensure that the X-rays can penetrate the in-situ reaction device 1, thereby facilitating the dynamic scanning of structural changes during the evolution of the coal and rock mass.

[0024] In addition, the method of heating the loose coal and rock mass 6 by introducing gas can perform a circumferential heating of the loose coal and rock mass 6, which can make the sample heat evenly and solve the heating problem of materials with low thermal conductivity. At the same time, it can cover a variety of sample material types.

[0025] The in-situ reaction device 1 is used to fill the loose coal and rock mass 6, the CT device 2 is used to perform tomographic scanning of the loose coal and rock mass 6 and obtain structural images of the loose coal and rock mass 6, the gas supply device 3 is used to introduce oxidizing gas at a preset temperature into the in-situ reaction device 1 and gradually raise the temperature of the loose coal and rock mass 6 to the target temperature, and the gas analysis device 4 is used to detect the concentration of gaseous products in the loose coal and rock mass 6. The specific types of the gas supply device 3, the in-situ reaction device 1, the CT device 2 and the gas analysis device 4 can be set according to actual needs and there are no restrictions on them.

[0026] For example, such as Figure 5 As shown, the data acquisition module 5 may include a data acquisition card 52 and a computer 51. The data acquisition card 52 (e.g., a multi-channel data acquisition instrument) is used to acquire various types of data. The computer 51 is used to perform calculations and processing based on the data acquired by the data acquisition card 52 to obtain a multi-field coupled evolution model of the loose coal and rock mass 6 based on its temperature, gas product concentration, and three-dimensional microstructure. Based on the hardware such as the data acquisition card 52 and the computer 51, as well as software such as scanning reconstruction software and concentration-temperature scanning frequency control software, the data acquisition module 5 is used to simultaneously acquire and process structural images and temperature-concentration data, control the scanning frequency, and visualize the temperature and concentration fields.

[0027] like Figure 2 and Figure 4 As shown, in some embodiments, the in-situ reaction device 1 includes a reaction chamber 11, a reaction container 12, and a top cover 13. The reaction container 12 is rotatably mounted inside the CT device 2 and has an air inlet groove. The top cover 13 covers the opening of the air inlet groove, forming an air inlet chamber. The air inlet end of the air inlet chamber is connected to the air outlet end of the gas supply device 3. Vacuum insulated chambers 14 are respectively provided on the outer wall of the reaction container 12 and the top cover 13. The reaction chamber 11 is located inside the air inlet chamber and has a reaction cavity for filling loose coal and rock mass 6. A flow equalization plate 15 is provided at the bottom of the reaction chamber 11, and the reaction cavity and the air inlet chamber are connected through the flow equalization plate 15. The air outlet end of the reaction cavity is connected to the air inlet end of the gas analysis device 4.

[0028] The preheated gas supplied by the gas supply device 3 enters the air inlet chamber and diffuses evenly into the reaction chamber from the flow equalization plate 15 at the bottom of the reaction chamber, thereby achieving uniform heating of the loose coal and rock mass 6 in the reaction chamber. Furthermore, by utilizing the vacuum insulation chamber 14 of the outer wall of the reaction container 12 and the top cover 13, temperature isolation between the inside and outside of the in-situ reaction device 1 can be achieved, ensuring the stable operation of the CT device 2.

[0029] The reactor includes a reaction chamber 11 for filling loose coal and rock mass 6. A breathable and heat-resistant flow equalization plate 15 is integrated at the bottom of the reactor to support the loose coal and rock mass 6 particles and disperse and equalize the airflow. The specific type of reaction chamber 11 can be configured according to actual needs and is not limited thereto. For example, the reaction chamber 11 can be made of quartz glass, and a switch structure matching the top cover 13 can be installed on the top. The reaction vessel 12 is used to support the reaction chamber 11, top cover 13, etc., and simultaneously achieves thermal isolation and X-ray penetration during the testing process. The specific type of the reaction vessel 12 can be set according to actual needs and is not limited thereto. For example, the reaction vessel 12 has a diameter of 200mm and a height of 200mm, and is composed of double-walled thick quartz glass, forming a vacuum insulated chamber 14 in the middle. Specifically, the thickness of the vacuum insulated chamber 14 is 5mm, and the thickness of the quartz wall is 2mm.

[0030] The reaction vessel 12 can be equipped with a hot air temperature control device with a heating rate of 0.1℃ / min-10℃ / min, and the hot air heater can achieve ventilation heating from 20℃ to 260℃.

[0031] The top cover 13 is used to seal the opening of the slot, forming a closed space for filling the loose coal and rock mass 6. The specific type of the top cover 13 can be set according to actual needs and is not limited thereto. For example, it is composed of double-layered thick-walled quartz glass, forming a vacuum insulated chamber 14 in the middle.

[0032] like Figure 2 and Figure 4 As shown, in some embodiments, the in-situ reaction device 1 further includes a heat-insulating base 16 and a heat-insulating cylinder 17. The heat-insulating base 16 is rotatably disposed inside the CT device 2, and the reaction container 12 is disposed on the heat-insulating base 16. The heat-insulating cylinder 17 is sleeved on the outside of the reaction container 12 and the top cover 13.

[0033] Since the heat insulation base 16 is rotatably installed inside the CT device 2 and the reaction container 12 is installed on the heat insulation base 16, the reaction container 12 can be arranged inside the CT device 2 using the heat insulation base 16, and the heat insulation base 16 can also be used to achieve heat isolation, thereby blocking the conduction of heat to the CT device 2 and preventing thermal drift from causing imaging artifacts.

[0034] In addition, since the heat insulation cylinder 17 is fitted on the outside of the reaction vessel 12 and the top cover 13, the heat insulation cylinder 17 can provide heat insulation protection for the reaction vessel 12 and the top cover 13, thereby further reducing the conduction of heat to the CT device 2.

[0035] The heat-insulating base 16 is used to support the reaction vessel 12 and provide heat insulation, while the heat-insulating cylinder 17 is used for heat insulation. The specific types of the heat-insulating base 16 and the heat-insulating cylinder 17 can be set according to actual needs and are not limited thereto.

[0036] The in-situ reaction device 1 consists of a top cover 13 and a reaction vessel 12 forming a sealed chamber structure. A heat-insulating base 16 is installed at the bottom to prevent the high temperature generated during the reaction from being conducted to the transmission components at the bottom, thus protecting the equipment. Internally, it integrates a reaction chamber 11 and a flow equalization plate 15. After the gas enters the reaction chamber 11, it is buffered and evenly distributed through the micropores of the porous flow equalization plate 15. The top cover 13 is sealed on top of the reaction vessel 12, forming a closed reaction space in conjunction with the heat-insulated reaction vessel 12. An external carbon fiber heat insulation cylinder 17 is provided. The entire in-situ reaction device 1 is mounted on the rotating stage 22 of the CT device 2 via the heat-insulating base 16, enabling in-situ rotational scanning.

[0037] like Figure 3 As shown, in some embodiments, the in-situ reaction device 1 further includes: a rotary joint 18 and a conductive slip ring (not shown in the figure). The rotor of the rotary joint 18 is mounted on the top cover 13, and the rotor of the rotary joint 18 has a first air inlet channel 181, a first air outlet channel 182, and a wiring harness channel 183. The air outlet end of the first air inlet channel 181 is connected to the air inlet end of the air inlet chamber, and the air inlet end of the first air outlet channel 182 is connected to the air outlet end of the reaction chamber. The stator of the rotary joint 18 is rotatably mounted on the rotor of the rotary joint 18, and the stator of the rotary joint 18 has a second air inlet channel 184 and a second air outlet channel 185. The air inlet end of the second air inlet channel 184 is connected to the air outlet end of the gas supply device 3. The outlet end is arranged along the circumference of the stator and is connected to the inlet end of the first inlet channel 181. The outlet end of the second outlet channel 185 is connected to the inlet end of the gas analyzer 4. The inlet end of the second outlet channel 185 is arranged along the circumference of the stator and is connected to the outlet end of the first outlet channel 182. The rotor of the conductive slip ring is connected to the rotor of the rotary joint 18, and the stator of the conductive slip ring is rotatably sleeved on the rotor of the conductive slip ring and connected to the stator of the rotary joint 18. One end of the wire harness channel 183 is connected to the reaction chamber, and the other end of the wire harness channel 183 passes through the rotor of the rotary joint 18 along the axial direction of the rotor to the rotor of the conductive slip ring.

[0038] Since the rotor of the rotary joint 18 is mounted on the top cover 13, and the stator of the rotary joint 18 is rotatably mounted on the rotor of the rotary joint 18, the rotor of the rotary joint 18 can rotate with the reaction vessel 12 while the stator of the rotary joint 18 can remain stationary, thus facilitating the connection of the gas supply device 3, the gas analysis device 4, etc.

[0039] Furthermore, since the outlet end of the first air intake channel 181 is connected to the air intake end of the air intake chamber, and the air intake end of the second air intake channel 184 is connected to the outlet end of the air supply device 3, and the outlet end of the second air intake channel 184 is arranged along the circumference of the stator and communicates with the air intake end of the first air intake channel 181, the air outlet end of the air supply device 3 and the air intake end of the air intake chamber can be connected by the cooperation of the first air intake channel 181 and the second air intake channel 184, and at the same time, it can adapt to the rotation between the rotor and the stator of the rotary joint 18.

[0040] Furthermore, since the inlet end of the first outlet channel 182 is connected to the outlet end of the reaction chamber, and the outlet end of the second outlet channel 185 is connected to the inlet end of the gas analyzer 4, and the inlet end of the second outlet channel 185 is arranged along the circumference of the stator and communicates with the outlet end of the first outlet channel 182, the inlet end of the gas analyzer 4 and the outlet end of the reaction chamber can be connected by the cooperation of the first outlet channel 182 and the second outlet channel 185, while also being able to accommodate the rotation between the rotor and the stator of the rotary joint 18.

[0041] Furthermore, since the rotor of the conductive slip ring is connected to the rotor of the rotary joint 18, and the stator of the conductive slip ring is rotatably mounted on the rotor of the conductive slip ring and connected to the stator of the rotary joint 18, one end of the wiring harness channel 183 is connected to the reaction chamber, and the other end of the wiring harness channel 183 passes through the rotor of the rotary joint 18 along the axial direction to the rotor of the conductive slip ring. This allows the wiring harnesses of the devices arranged in the reaction chamber to be connected to the outside through the wiring harness channel 183 and the cooperation between the rotor and the stator of the conductive slip ring. For example, the wiring harness of the temperature sensor 38 passes through the wiring harness channel 183 and is connected to the rotor of the conductive slip ring. At the same time, the wiring harness of the stator is connected to the data acquisition module 5, etc.

[0042] Both the rotary joint 18 and the conductive slip ring have rotors and stators. The rotor and stator of the rotary joint 18 are used to conduct air passages and pass through the wire harness, while the rotor and stator of the conductive slip ring are used to conduct circuits.

[0043] Specifically, for the first air intake channel 181 and the second air intake channel 184, for example, the first air intake channel 181 is arranged in an L-shape and the second air intake channel 184 is arranged in a straight line. At the same time, the air outlet of the second air intake channel 184 is set as an annular groove structure, and the air intake end of the first air intake channel 181 is located inside the annular groove structure.

[0044] For the first air outlet channel 182 and the second air outlet channel 185, for example, the first air outlet channel 182 is arranged in an L-shape and the second air outlet channel 185 is arranged in a straight line. At the same time, the air inlet end of the second air outlet channel 185 is set as an annular groove structure, and the air outlet end of the first air outlet channel 182 is located inside the annular groove structure.

[0045] The rotor of the rotary joint 18 extends outward and is fixedly connected to the rotor of the conductive slip ring to form a synchronously rotating integral rotating unit. The stator of the rotary joint 18 is fixed relative to the stator of the conductive slip ring to form a stationary unit. The main body material of the rotary joint 18 is polyetheretherketone (PEEK).

[0046] To meet the requirement of simultaneous gas transmission and electrical signal conduction during the rotation of the in-situ reaction device 1, a rotary joint 18 and a conductive slip ring are arranged in series along the axial direction. When the rotary joint 18 is working, the external gas source 31 enters through the side interface of the rotary joint 18, is transmitted to the reaction vessel 12 through the annular flow channel and then discharged. The conductive slip ring is coaxially arranged at the top of the rotary joint 18. The circuit is connected to the internal sensor (e.g., temperature sensor 38) of the reaction vessel 12 through the central wire harness channel 183. The electrical signal is transmitted to the data acquisition card 52 through the central wire harness, the conductive slip ring rotor, and the conductive slip ring stator.

[0047] In general, the reaction chamber 11, reaction container 12, top cover 13, heat insulation base 16, heat insulation cylinder 17, etc. form a sealed cylinder, which is placed on the rotating stage 22 of the CT device 2 to hold the sample (loose coal and rock mass 6).

[0048] The reaction vessel 12 is composed of double-layered quartz glass with a vacuum insulation design between the layers; the top cover 13 is provided with an inlet and outlet for connecting the gas passage and is connected to the gas supply device 3 and the gas analysis device 4 through a rotary joint 18; the outer surface of the top cover 13 is provided with an insulation layer; the heat insulation base 16 is made of rigid ceramic fiber board and supports the reaction vessel 12 through multiple protrusions; the heat insulation cylinder 17 is made of low-density ceramic fiber material, which has the advantages of high temperature resistance, stable performance and good heat insulation performance.

[0049] During the heating phase, the CT device 2 requires a temperature not exceeding 60 degrees Celsius. However, the in-situ reaction device 1 needs to maintain both its internal and external temperatures in an adiabatic environment. Therefore, traditional methods cannot achieve simultaneous adiabatic programmed heating experiments during CT scanning. Based on this, the system of this embodiment achieves uniform programmed heating of the coal sample while meeting the temperature requirements for CT scanning.

[0050] The system uses quartz glass that meets the requirements for X-ray penetration of coal samples during CT scanning, while also possessing sufficient high-temperature resistance and strength for temperature-increasing tests. This embodiment employs a wave-transparent quartz container and vacuum insulation design to eliminate metal artifacts and achieve high-quality imaging. Furthermore, to prevent heat loss that could damage the detector 24 and to prevent positional changes due to thermal expansion and contraction, the reaction device utilizes a double-layer quartz glass vacuum insulation design. This design effectively blocks thermal radiation to protect the CT detector 24 and controls heat loss to prevent thermal deformation of the precision rotating stage 22 that could cause sample position drift, thus enabling in-situ scanning under high-temperature conditions.

[0051] In some embodiments, the gas supply device 3 includes a gas supply module and a heating module. The gas supply module's outlet is connected to the inlet of the in-situ reaction device 1, and the gas supply module is used to introduce oxidizing gas into the in-situ reaction device 1. The heating module is disposed between the gas supply module's outlet and the inlet of the in-situ reaction device 1, and the heating module is used to heat the oxidizing gas, thereby gradually raising the temperature of the loose coal and rock mass 6 to the target temperature.

[0052] Since the outlet of the gas supply module is connected to the inlet of the in-situ reaction device 1, and the heating module is located between the outlet of the gas supply module and the inlet of the in-situ reaction device 1, the in-situ reaction device 1 can obtain oxidizing gas at a preset temperature by utilizing the cooperation of the gas supply module and the heating module, so that the loose coal and rock mass 6 inside can be gradually heated to the target temperature.

[0053] The specific types of the gas supply module and heating module can be set according to actual needs, and there are no restrictions on them.

[0054] like Figure 5 As shown, in some embodiments, the gas supply module includes: a gas source 31, a pressure reducing valve 32, a mass flow controller 33, a one-way valve 34, a mixing tank 35, and a first pressure sensor 36. The gas source 31 has its outlet connected to the pressure reducing valve 32's inlet, the pressure reducing valve 32's outlet connected to the mass flow controller 33's inlet, the mass flow controller 33's outlet connected to the check valve 34's inlet, the check valve 34's outlet connected to the mixing tank 35's inlet, the mixing tank 35's outlet connected to the in-situ reaction device 1's inlet, a heating module positioned between the mixing tank 35's outlet and the in-situ reaction device 1's inlet, and the first pressure sensor 36's detection end positioned at the mixing tank 35's outlet. The data acquisition module 5's signal input is connected to the first pressure sensor 36's signal output and the mass flow controller 33's signal output, and the data acquisition module 5's signal output is connected to the pressure reducing valve 32's signal input and the mass flow controller 33's signal output.

[0055] The oxidizing gas output from the gas source 31 passes through the pressure-regulating valve 32, the mass flow control of the mass flow controller 33, the one-way valve 34, and the mixing buffer of the mixing tank 35 before entering the in-situ reaction device 1, thereby achieving stable heating of the loose coal and rock mass 6 in the in-situ reaction device 1.

[0056] Since the signal input terminal of the data acquisition module 5 is connected to the signal output terminal of the first pressure sensor 36 and the signal output terminal of the mass flow controller 33 respectively, and the signal output terminal of the data acquisition module 5 is connected to the signal input terminal of the pressure reducing valve 32 and the signal output terminal of the mass flow controller 33 respectively, the data acquisition module 5 can monitor the oxidation gas parameters (such as pressure, flow rate, etc.) obtained by the in-situ reaction device 1, and can also control the oxidation gas using the pressure reducing valve 32, the mass flow controller 33, etc., thereby ensuring the stable and efficient delivery of oxidation gas to the in-situ reaction device 1.

[0057] The system includes: a gas source 31 for supplying oxidizing gas; a pressure reducing valve 32 for stabilizing the pressure of the oxidizing gas; a mass flow controller 33 for regulating the flow rate of the oxidizing gas; a check valve 34 for preventing backflow of the oxidizing gas; a mixing tank 35 for mixing and buffering the oxidizing gas to ensure a smooth and uniform gas flow into the in-situ reaction device 1; and a first pressure sensor 36 for detecting the gas pressure at the outlet of the mixing tank 35. The specific types of the gas source 31, pressure reducing valve 32, mass flow controller 33, check valve 34, mixing tank 35, and first pressure sensor 36 can be configured according to actual needs and are not limited thereto.

[0058] like Figure 5 As shown, in some embodiments, the heating module includes a heater 37 and a temperature sensor 38. The heater 37 is disposed between the outlet of the gas supply module and the inlet of the in-situ reaction device 1, and the detection end of the temperature sensor 38 is disposed within the in-situ reaction device 1. The signal input end of the data acquisition module 5 is connected to the signal output end of the temperature sensor 38, and the signal output end of the data acquisition module 5 is connected to the signal input end of the heater 37. The data acquisition module 5 is used to control the heater 37 according to the temperature detected by the temperature sensor 38, so that the oxidizing gas reaches a preset temperature.

[0059] Since the heater 37 is located between the outlet of the gas supply module and the inlet of the in-situ reaction device 1, the heater 37 can heat the oxidizing gas entering the in-situ reaction device 1, thereby ensuring uniform heating and stable temperature rise of the loose coal and rock mass 6. Furthermore, since the detection end of the temperature sensor 38 is located inside the in-situ reaction device 1, the temperature sensor 38 can detect the temperature inside the in-situ reaction device 1.

[0060] In addition, since the signal input terminal of the data acquisition module 5 is connected to the signal output terminal of the temperature sensor 38, and the signal output terminal of the data acquisition module 5 is connected to the signal input terminal of the heater 37, the data acquisition module 5 can control the heater 37 according to the temperature detected by the temperature sensor 38 so that the oxidizing gas reaches the preset temperature, thereby using closed-loop control to ensure the precise heating of the loose coal and rock mass 6 in the in-situ reaction device 1.

[0061] The heater 37 and the temperature sensor 38 work together to achieve closed-loop temperature control, which can accurately perform heating according to experimental requirements. The specific types of heater 37 and temperature sensor 38 can be set according to actual needs and are not limited thereto.

[0062] For example, temperature sensor 38 can be a thermocouple, with thermocouple probes positioned in the inlet passage, outlet passage, and slightly above the center of the coal sample to meet the requirements of temperature control, thermal balance analysis, and spontaneous combustion stage determination. Heater 37 employs a coil structure, controlling the gas heating based on the temperature measured by the thermocouple to achieve a set heating rate. Furthermore, temperature sensor 38 can perform tests within a range of 0°C to 260°C.

[0063] The heated oxidizing gas is introduced into the in-situ reaction device 1 to heat or keep warm the loose coal and rock mass 6. The high-temperature airflow blows through the accumulated coal particles to heat them up, simulating the real convection heat transfer process to the greatest extent. The heating method conforms to the nature of spontaneous combustion.

[0064] like Figure 4 As shown, in some embodiments, the CT device 2 includes: a protective lead room 21, a rotating stage 22, an X-ray source 23, and a detector 24. The rotating stage 22 is housed within the protective lead room 21, and the in-situ reaction device 1 is mounted on the rotating stage 22. The rotating stage 22 drives the in-situ reaction device 1 to rotate. The X-ray source 23 and the detector 24 are positioned opposite each other and located on opposite sides of the in-situ reaction device 1. The signal output terminal of the data acquisition module 5 is connected to the signal input terminal of the X-ray source 23 and the signal input terminal of the rotating stage 22, respectively. The signal input terminal of the data acquisition module 5 is connected to the signal output terminal of the detector 24. The data acquisition module 5 controls the rotating stage 22 to rotate at a preset speed and performs tomographic scanning of the loose coal and rock mass 6 using the X-ray source 23 and the detector 24 to obtain dynamic structural images of the loose coal and rock mass 6 at different temperature stages.

[0065] Since the in-situ reaction device 1 is set on the rotating platform 22 inside the protective lead room 21, the in-situ reaction device 1 can rotate using the rotating platform 22. Furthermore, since the radiation source 23 and the detector 24 are arranged opposite each other and located on both sides of the in-situ reaction device 1, and the signal output terminal of the data acquisition module 5 is connected to the signal input terminal of the radiation source 23 and the signal input terminal of the rotating platform 22 respectively, and the signal input terminal of the data acquisition module 5 is connected to the signal output terminal of the detector 24, the data acquisition module 5 can control the rotating platform 22 to rotate at a preset speed, and obtain the rotational dynamic structure image of the loose coal rock mass 6 at different temperature stages by tomographic scanning of the loose coal rock mass 6 through the radiation source 23 and the detector 24, thereby obtaining a multi-field coupled evolution model of the loose coal rock mass 6 based on the rotational dynamic structure image.

[0066] For example, the data acquisition module 5 starts the CT device 2 according to the set requirements. The entire scanning process of the CT device 2 is carried out in a fully enclosed protective lead room 21. When the CT scan starts, high-power X-rays are emitted towards the uniformly rotating loose coal and rock mass 6. After the X-rays are absorbed by the coal and rock particles, their energy is attenuated and projected onto the imaging plate detector 24, obtaining the residual X-ray energy distribution of different cross sections of the loose coal and rock mass 6. Through image reconstruction processing, the coal and rock mass accumulation structure at different oxidation times is obtained, that is, the rotational dynamic structure image of the loose coal and rock mass 6 at different temperature stages. Simultaneously, the data acquisition module 5 records the temperature of the loose coal and rock mass 6 and the concentration of gaseous products in the in-situ reaction device 1.

[0067] The protective lead room 21 is used for radiation isolation and protection, the rotating stage 22 is used for the uniform rotation of the in-situ reaction device 1, and the radiation source 23 and detector 24 are used to obtain rotating dynamic structural images of the loose coal and rock mass 6 at different temperature stages by emitting and receiving X-rays. The specific types of the protective lead room 21, rotating stage 22, radiation source 23 and detector 24 can be set according to actual needs and there are no restrictions on them.

[0068] The CT device 2 is housed inside a protective lead-lined enclosure 21. It is used for dynamic scanning and three-dimensional reconstruction of the coal pile's stacked structure during spontaneous combustion, and the lead layer effectively prevents radiation leakage, ensuring operational safety. To maintain thermal balance within the enclosed space, exhaust fans 25 are installed on the inner wall of the lead-lined enclosure. Forced air cooling effectively removes heat generated during the operation of the radiation source 23 and detector 24, as well as during high-temperature reactions, preventing localized overheating from affecting imaging accuracy or damaging the equipment. Inside the lead-lined enclosure, the radiation source 23 and detector 24 are positioned opposite each other, defining the CT imaging area. The in-situ reaction device 1 is mounted on a rotating stage 22 at the center of the imaging area.

[0069] For example, the dimensions of the fully enclosed protective lead room 21 are 800 mm long, 1300 mm wide, and 2100 mm high. The radiation source 23 has a power of 500 W, a standard mode reconstruction resolution of 180 μm, a high-precision mode resolution of 100 μm, a rotating stage 22 with a rotation accuracy of 5 μm, a maximum load weight of 5 kg, and a maximum load size of 250 mm in diameter and 300 mm in height.

[0070] like Figure 5 As shown, in some embodiments, the gas analysis device 4 includes: a heat tracing pipe 41, a condenser pipe 42, a fume hood 43, a gas chromatograph 44, and a second pressure sensor 45. The heat tracing pipe 41 has its first channel inlet connected to the outlet of the in-situ reaction device 1, and its second channel is supplied with heat tracing fluid. The condenser pipe 42 has its first channel inlet connected to the outlet of the heat tracing pipe 41, and its second channel is supplied with condensing fluid. The fume hood 43 has its inlet connected to the outlet of the heat tracing pipe 41. The gas chromatograph 44 has its inlet connected to the outlet of the condenser pipe 42, and its signal output is connected to the signal input of the data acquisition module 5. The data acquisition module 5 is used to obtain the gaseous product concentration of the loose coal and rock mass 6 through the gas chromatograph 44. The detection end of the second pressure sensor 45 is located at the outlet of the first channel of the heat tracing pipe 41, and its signal output is connected to the signal input of the data acquisition module 5. The data acquisition module 5 is used to obtain the gas pressure at the outlet of the first channel of the heat tracing pipe 41 through the second pressure sensor 45.

[0071] Since the first channel inlet of the heat tracing pipe 41 is connected to the outlet of the in-situ reaction device 1, and the first channel inlet of the condenser pipe 42 is connected to the outlet of the first channel of the heat tracing pipe 41, and the inlet of the gas chromatograph 44 is connected to the outlet of the first channel of the condenser pipe 42, the gaseous products of the loose coal and rock mass 6 in the in-situ reaction device 1 can enter the gas chromatograph 44 for concentration detection after passing through the first channel of the heat tracing pipe 41 and the first channel of the condenser pipe 42.

[0072] Furthermore, since the signal output terminal of the gas chromatograph 44 is connected to the signal input terminal of the data acquisition module 5, the data acquisition module 5 can obtain the gas product concentration of the loose coal rock mass 6 through the gas chromatograph 44, and then obtain the multi-field coupled evolution model of the loose coal rock mass 6 based on the gas product concentration of the loose coal rock mass 6.

[0073] In addition, since the air inlet of the fume hood 43 is connected to the air outlet of the first channel of the heat tracing pipe 41, the remaining gaseous products can be discharged through the fume hood 43, ensuring the stable reaction of the loose coal and rock mass 6 in the in-situ reaction device 1.

[0074] In this system, since the second channel of the heat tracing pipe 41 is supplied with a heat tracing fluid (which may be heated oxidizing gas from the gas supply device 3), the gaseous products can be heated and kept warm by the heat tracing fluid when passing through the first channel of the heat tracing pipe 41, thereby solving the problem of gas condensation and blockage. Furthermore, since the second channel of the condenser pipe 42 is supplied with a condensing fluid, the gaseous products can be cooled by the condensing fluid when passing through the first channel of the condenser pipe 42, thereby ensuring the accurate detection of the gaseous product concentration by the gas chromatograph 44.

[0075] Furthermore, since the detection end of the second pressure sensor 45 is located at the gas outlet end of the first channel of the heat tracing pipe 41, and the signal output end of the second pressure sensor 45 is connected to the signal input end of the data acquisition module 5, the data acquisition module 5 can obtain the gas pressure at the gas outlet end of the first channel of the heat tracing pipe 41 through the second pressure sensor 45, thereby realizing gas pressure monitoring and ensuring stable operation of the system.

[0076] The heat tracing pipe 41 is used to heat the gaseous product using a heat tracing fluid; the condenser pipe 42 is used to condense the gaseous product using a condensing fluid; the fume hood 43 is used for the emission of the gaseous product; the gas chromatograph 44 is used for real-time detection of the gaseous product concentration; and the second pressure sensor 45 is used for detection of the gaseous product pressure. The specific types of the heat tracing pipe 41, condenser pipe 42, fume hood 43, gas chromatograph 44, and second pressure sensor 45 can be configured according to actual needs and are not limited thereto.

[0077] For example, the gas chromatograph 44 tests the concentration of index gas at the outlet of the in-situ reaction device 1. The instrument's operating temperature is 0℃-60℃, the operating humidity is 5%RH-95%RH, the operating voltage is 220V±10%, the split ratio is 12500:1, and the minimum detection limit is ≤0.9pg / ml.

[0078] The exhaust gas (gaseous products) generated during the reaction is split into two paths after discharge. One path connects to a gas chromatograph 44 for online component analysis of the reaction products, while the other path is discharged into a fume hood 43. The entire system operates with the computer 51 of the data acquisition module 5 as the control core. It collects CT image data through the data acquisition card 52 and establishes electrical connections with the mass flow controller 33, heater 37, temperature sensor 38, first pressure sensor 36, and second pressure sensor 45, respectively, to achieve precise feedback control and centralized data acquisition of experimental parameters such as gas flow, temperature, and pressure.

[0079] This disclosure also proposes a multi-field coupling testing method for loose coal and rock masses based on in-situ CT, including: Loose coal and rock mass 6 is filled into the in-situ reaction device 1 inside the CT device 2, and the gas outlet of the gas supply device 3 is connected to the gas inlet of the in-situ reaction device 1, and the gas inlet of the gas analysis device 4 is connected to the gas outlet of the in-situ reaction device 1. The quartz outer wall of the in-situ reaction device 1 is provided with a vacuum heat insulation chamber 14. Oxidizing gas at a preset temperature is introduced into the in-situ reaction device 1 through the gas supply device 3, and the loose coal rock mass 6 is gradually heated to the target temperature. The concentration of gas products in the loose coal rock mass 6 is detected by the gas analysis device 4. The loose coal rock mass 6 is then subjected to tomographic scanning by the CT device 2 to obtain a structural image of the loose coal rock mass 6. The rotational dynamic structure images of loose coal rock mass 6 at different temperature stages were reconstructed to obtain the three-dimensional microstructure of loose coal rock mass 6 at different temperature stages. Based on the temperature of loose coal rock mass 6, the concentration of gas products of loose coal rock mass 6, and the three-dimensional microstructure of loose coal rock mass 6, a multi-field coupled evolution model of loose coal rock mass 6 was constructed.

[0080] The CT device 2 obtains rotational dynamic structural images of the loose coal and rock mass 6 at different temperature stages, and reconstructs the structural images to obtain the three-dimensional microstructure of the loose coal and rock mass 6 at different temperature stages. Based on the temperature, gas product concentration, and three-dimensional microstructure of the loose coal and rock mass 6, a multi-field coupled evolution model of the loose coal and rock mass 6 is constructed, which facilitates the analysis of the multi-field coupled disaster mechanism. In addition, the quartz outer wall of the in-situ reaction device 1 and the vacuum insulation chamber 14 of the outer wall not only achieve temperature isolation between the inside and outside of the in-situ reaction device 1 to ensure the stable operation of the CT device 2, but also ensure that the X-rays can penetrate the in-situ reaction device 1, thereby facilitating the dynamic scanning of structural changes during the evolution of the coal and rock mass.

[0081] The testing system in this embodiment can not only record and observe the temperature and gas production of loose coal in real time during the heating process, but also conduct in-situ dynamic tests under the coupling effect of multiple physics fields, and use CT technology to quantitatively visualize the microstructural features of coal samples. It is particularly suitable for simulating the evolution of coal body structure during the spontaneous combustion process of coal.

[0082] Furthermore, the testing method has the following steps: Step 1: Sample loading and system connection. The prepared loose coal and rock mass particle 6 sample is loaded into the reaction vessel 12, which is a double-layered hollow quartz cylinder, in the specially designed in-situ reaction device 1. The top cover 13 is installed and sealed. The in-situ reaction device 1 is fixed on the high-precision rotating stage 22 of the CT device 2. The gas supply device 3 is connected to the gas inlet of the in-situ reaction device 1, and the gas analysis device 4 is connected to the gas outlet of the in-situ reaction device 1. The thermocouple probe is inserted into the predetermined temperature measurement point inside the coal sample.

[0083] Step 2: Equipment debugging and initial scan. Turn on the data acquisition module 5, check whether the signals of each sensor are normal, start the CT device 2, and perform the first scan on the loose coal and rock mass 6 under normal temperature conditions. Set the power of the X-ray source 23 to 500W, select the accuracy mode according to the particle size, and obtain the basic data of the initial packing structure and pore distribution of the coal body.

[0084] Step 3: Programmed Temperature Rise Oxidation and Multi-Field Monitoring. Experimental conditions are set via the gas supply module and heating module. Gas source 31 is turned on to introduce gas, the gas flow rate is set, and heater 37 is started. The in-situ reaction device 1 is heated according to the preset temperature rise program. During the temperature rise process, temperature and gas monitoring are performed. Temperature monitoring uses a data acquisition instrument to record real-time temperature changes within the coal body within the range of 0℃-260℃. Gas monitoring uses a gas analysis device 4 to extract the outlet gas in real-time, and a gas chromatograph 44 analyzes the concentration of the target gas.

[0085] Step 4: In-situ dynamic CT scan. When the coal temperature reaches the preset temperature point, the heating module is controlled to maintain a constant temperature, and the CT device 2 is started to perform an in-situ scan of the coal sample at this temperature. At this time, the gas circuit device rotates at the same speed as the rotating stage 22 to ensure that 360° rotation imaging is completed without interrupting the gas supply or disconnecting the connection, so as to obtain dynamic structural images after thermal expansion and oxidation erosion.

[0086] Step 5: Data Processing and 3D Reconstruction. After the experiment, the scanning and reconstruction software on the data acquisition workstation was used to perform 3D reconstruction of the CT projection data at different temperature nodes, obtaining a 3D model of the evolution of coal sample porosity and specific surface area with temperature. Combining the synchronously acquired temperature data and gas concentration data, a multi-field coupled evolution model of the internal temperature field, concentration field, and microstructure field of loose coal-rock mass 6 was constructed using visualization software to analyze the multi-field coupled disaster-causing mechanism.

[0087] The core idea of ​​the testing system and method implemented here is to simulate the oxidation process of coal under different stacking conditions based on the actual working conditions of coal spontaneous combustion, and to record the changes in the macroscopic and microscopic structure of the coal body in situ in real time. It has at least the following beneficial effects: 1. Multi-parameter synchronous in-situ measurement: During the experiment, for the CT device 2, the rotating stage 22 drives the in-situ reaction device 1 to rotate 360 ​​degrees. With the gas connection structure at the top, the heating process and the scanning process are carried out simultaneously, and the temperature, structure and gas production data of the heating process are obtained in-situ.

[0088] 2. Anti-interference design: Through the structure of heat insulation cylinder 17 and double-layer vacuum shell, the problem of damage to CT equipment during heating in traditional in-situ scanning heating experimental devices is solved. At the same time, the combined use of reaction chamber 11 and flow equalization plate 15 ensures the accuracy of coal oxidation reaction kinetic data. The setting of heat insulation base 16 effectively blocks heat transfer and prevents rotating precision parts from deforming or being damaged due to heat.

[0089] 3. Equipment compatibility optimization: For materials with different thermal conductivity, hot air heating is used in conjunction with reaction chamber 11 and flow equalization plate 15 to effectively heat the sample to be tested.

[0090] 4. Thermal insulation gas-electric combination slip ring design: The rotary joint 18 has a relatively stationary stator end and a rotor end that rotates with the reactor. It forms an independent air inlet and outlet passage. The conductive slip ring is coaxially set on the wiring harness channel 183. Through the integrated structure of the dual-channel rotary joint 18 and the conductive slip ring, together with the internally connected air inlet, outlet and wiring harness channels 183, continuous conduction of gas circulation and electrical signal transmission is achieved under the condition of 360-degree rotational CT scanning in the in-situ reaction device 1, effectively avoiding the risk of external cable entanglement.

[0091] In the description of this disclosure, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0092] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of preferred embodiments of this disclosure includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this disclosure pertain.

[0093] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0094] Although embodiments of the present disclosure have been shown and described above, these embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A multi-field coupling testing system for loose coal and rock masses based on in-situ computed tomography (CT), characterized in that, include: In-situ reaction device, CT device, gas supply device, gas analysis device and data acquisition module; The in-situ reaction device is used to fill the loose coal and rock mass, and the quartz outer wall of the in-situ reaction device is provided with a vacuum insulated chamber. The in-situ reaction device is rotatably mounted inside the CT device, and the CT device is used for tomographic scanning of the loose coal and rock mass and to obtain structural images of the loose coal and rock mass; The outlet of the gas supply device is connected to the inlet of the in-situ reaction device, and the gas supply device is used to introduce oxidizing gas at a preset temperature into the in-situ reaction device and gradually heat the loose coal and rock mass to the target temperature. The gas analyzer is connected to the gas outlet of the in-situ reaction device, and the gas analyzer is used to detect the concentration of gaseous products in the loose coal and rock mass. The data acquisition module is used to obtain rotational dynamic structural images of the loose coal and rock mass at different temperature stages through the CT device, and to reconstruct the structural images to obtain the three-dimensional microstructure of the loose coal and rock mass at different temperature stages. Furthermore, it constructs a multi-field coupled evolution model of the loose coal and rock mass based on the temperature of the loose coal and rock mass, the concentration of gas products of the loose coal and rock mass, and the three-dimensional microstructure of the loose coal and rock mass.

2. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 1, characterized in that, The in-situ reaction apparatus includes: Reaction chamber, reaction vessel, and top cover; The reaction vessel is rotatably disposed inside the CT device, and the reaction vessel is provided with an air inlet groove. The top cover is disposed on the opening of the air inlet groove and the air inlet groove forms an air inlet chamber. The air inlet end of the air inlet chamber is connected to the air outlet end of the air supply device. The outer wall of the reaction vessel and the top cover are respectively provided with vacuum insulation chambers. The reaction chamber is located inside the air inlet chamber, and the reaction chamber is equipped with a reaction cavity for filling the loose coal and rock mass. A flow equalization plate is provided at the bottom of the reaction chamber. The reaction cavity and the air inlet chamber are connected through the flow equalization plate. The air outlet of the reaction cavity is connected to the air inlet of the gas analysis device.

3. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 2, characterized in that, The in-situ reaction apparatus further includes: Insulated base and insulation cylinder; The heat-insulating base is rotatably disposed within the CT device, and the reaction vessel is disposed on the heat-insulating base; The heat insulation cylinder is fitted onto the outside of the reaction vessel and the top cover.

4. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 2, characterized in that, The in-situ reaction apparatus further includes: Rotary joints and conductive slip rings; The rotor of the rotary joint is disposed on the top cover, and the rotor of the rotary joint is provided with a first air inlet channel, a first air outlet channel and a wire harness channel. The air outlet end of the first air inlet channel is connected to the air inlet end of the air inlet chamber, and the air inlet end of the first air outlet channel is connected to the air outlet end of the reaction chamber. The stator of the rotary joint is rotatably mounted on the rotor of the rotary joint. The stator of the rotary joint is provided with a second air inlet channel and a second air outlet channel. The air inlet end of the second air inlet channel is connected to the air outlet end of the air supply device. The air outlet end of the second air inlet channel is arranged along the circumference of the stator and communicates with the air inlet end of the first air inlet channel. The air outlet end of the second air outlet channel is connected to the air inlet end of the gas analysis device. The air inlet end of the second air outlet channel is arranged along the circumference of the stator and communicates with the air outlet end of the first air outlet channel. The rotor of the conductive slip ring is connected to the rotor of the rotary joint, and the stator of the conductive slip ring is rotatably sleeved on the rotor of the conductive slip ring and connected to the stator of the rotary joint. One end of the wire harness channel is connected to the reaction chamber, and the other end of the wire harness channel passes through the rotor of the rotary joint along the axial direction to the rotor of the conductive slip ring.

5. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 1, characterized in that, The gas supply device includes: Gas supply module and heating module; The outlet of the gas supply module is connected to the inlet of the in-situ reaction device, and the gas supply module is used to introduce oxidizing gas into the in-situ reaction device. The heating module is located between the gas outlet of the gas supply module and the gas inlet of the in-situ reaction device, and the heating module is used to heat the oxidizing gas so that the loose coal and rock mass gradually heats up to the target temperature.

6. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 5, characterized in that, The gas supply module includes: Gas source, pressure reducing valve, mass flow controller, check valve, mixing tank, and first pressure sensor; The gas source outlet is connected to the pressure reducing valve inlet, the pressure reducing valve outlet is connected to the mass flow controller inlet, the mass flow controller outlet is connected to the check valve inlet, the check valve outlet is connected to the mixing tank inlet, the mixing tank outlet is connected to the inlet of the in-situ reaction device, the heating module is located between the mixing tank outlet and the in-situ reaction device inlet, and the detection end of the first pressure sensor is located at the mixing tank outlet. The signal input terminal of the data acquisition module is connected to the signal output terminal of the first pressure sensor and the signal output terminal of the mass flow controller, respectively. The signal output terminal of the data acquisition module is connected to the signal input terminal of the pressure reducing valve and the signal output terminal of the mass flow controller, respectively.

7. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 5, characterized in that, The heating module includes: Heater and temperature sensor; The heater is located between the outlet of the gas supply module and the inlet of the in-situ reaction device, and the detection end of the temperature sensor is located inside the in-situ reaction device. The signal input terminal of the data acquisition module is connected to the signal output terminal of the temperature sensor, and the signal output terminal of the data acquisition module is connected to the signal input terminal of the heater. The data acquisition module is used to control the heater according to the temperature detected by the temperature sensor so that the oxidizing gas reaches the preset temperature.

8. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 1, characterized in that, The CT device includes: Protective lead room, rotating stage, radiation source and detector; The rotating platform is located inside the protective lead room, and the in-situ reaction device is located on the rotating platform. The rotating platform is used to drive the in-situ reaction device to rotate. The radiation source and the detector are arranged opposite each other and located on both sides of the in-situ reaction device. The signal output terminal of the data acquisition module is connected to the signal input terminal of the radiation source and the signal input terminal of the rotating stage, respectively. The signal input terminal of the data acquisition module is connected to the signal output terminal of the detector. The data acquisition module is used to control the rotating stage to rotate at a preset speed, and to perform tomographic scanning of the loose coal and rock mass through the radiation source and the detector to obtain rotational dynamic structural images of the loose coal and rock mass at different temperature stages.

9. The multi-field coupling testing system for loose coal and rock masses based on in-situ CT according to claim 1, characterized in that, The gas analysis device includes: Heat tracing pipe, condenser pipe, fume hood, gas chromatograph, and second pressure sensor; The first channel of the heat tracing pipe is connected to the air inlet of the in-situ reaction device, and the second channel of the heat tracing pipe is filled with heat tracing fluid. The first channel of the condenser is connected to the air inlet of the first channel of the heat tracing pipe, and the second channel of the condenser is filled with condensing fluid. The air inlet of the fume hood is connected to the air outlet of the first channel of the heat tracing pipe. The gas chromatograph's inlet is connected to the gas outlet of the first channel of the condenser, and the gas chromatograph's signal output is connected to the signal input of the data acquisition module. The data acquisition module is used to obtain the concentration of gaseous products of the loose coal and rock mass through the gas chromatograph. The detection end of the second pressure sensor is located at the gas outlet end of the first channel of the heat tracing pipe, and the signal output end of the second pressure sensor is connected to the signal input end of the data acquisition module. The data acquisition module is used to obtain the gas pressure at the gas outlet end of the first channel of the heat tracing pipe through the second pressure sensor.

10. A multi-field coupling testing method for loose coal and rock masses based on in-situ CT, characterized in that, include: The loose coal and rock mass is filled into the in-situ reaction device in the CT device, and the gas outlet of the gas supply device is connected to the gas inlet of the in-situ reaction device, and the gas inlet of the gas analysis device is connected to the gas outlet of the in-situ reaction device. The quartz outer wall of the in-situ reaction device is provided with a vacuum heat-insulating chamber. The gas supply device introduces oxidizing gas at a preset temperature into the in-situ reaction device, gradually raising the temperature of the loose coal rock mass to the target temperature. The gas analysis device detects the concentration of gas products in the loose coal rock mass. The CT device performs tomographic scanning of the loose coal rock mass and obtains a structural image of the loose coal rock mass. The three-dimensional microstructure of the loose coal and rock mass at different temperature stages is obtained by reconstructing the rotational dynamic structure images of the loose coal and rock mass at different temperature stages. Based on the temperature of the loose coal and rock mass, the concentration of gas products of the loose coal and rock mass, and the three-dimensional microstructure of the loose coal and rock mass, a multi-field coupled evolution model of the loose coal and rock mass is constructed.

Images