Test system and test method for coupling non-focused microwave radiation pyrolysis of coal sample with permeation CT (Computed Tomography) scanning

Abstract

The invention provides a test system and method for coupling non-focused microwave radiation pyrolysis of a coal sample with permeation CT scanning, and belongs to the field of coal in-situ pyrolysis. The system comprises a microwave generation system, a pyrolysis seepage cavity, a pyrolysis seepage gas injection system, a loading system, a product collection system, a data acquisition system and a cooling system, the microwave generation system emits microwaves, a coal sample in the pyrolysis seepage cavity is heated, non-focused microwaves are formed in the cavity, and the in-situ microwave pyrolysis state is simulated; a pyrolysis experiment and a permeation experiment of the coal sample can be completed by injecting pyrolysis atmosphere or permeation gas into the cavity through the pyrolysis permeation gas injection system; the pyrolysis seepage cavity is directly placed on a CT scanner to be scanned, and the change conditions of coal sample hole fractures at different pyrolysis temperatures can be observed. The method can be used for analyzing the evolution law of microwave pyrolysis on the physical microstructure, permeability and mass and heat transfer of coal, and overcomes the defects of a traditional test method.

Description

Technical Field

[0001] The present application relates to the technical field of in-situ coal pyrolysis, and in particular to an experimental system and method for coupling non-focused microwave radiation pyrolysis of coal samples with penetration CT scanning. Background Art

[0002] In-situ pyrolysis of coal is a new coal mining method that directly pyrolyzes coal underground and then separates oil and gas. It is a green and efficient way of coal development and utilization that is both economical and environmentally friendly, and has received widespread attention from experts and scholars in the energy field at home and abroad.

[0003] Currently, the traditional pyrolysis heating method is electric heating, which conducts heat through an external heat source, which may cause problems such as slow heating rate, high energy consumption, and uneven temperature distribution. Microwave radiation heating uses the microwave electromagnetic field to interact with the polar molecules or conductive components in the coal, and directly heats the coal blocks through dielectric loss or eddy current effect. The energy of this heating method acts directly on the coal blocks, heating them simultaneously inside and outside, with a fast and uniform heating rate.

[0004] Patent CN111139099A provides a microwave pyrolysis device, including: a frame, a microwave generating device, a waveguide protection device, and a stirring device. It can perform pyrolysis treatment on large quantities of materials. Each device operates independently, is easy to maintain, and has high processing efficiency, overcoming the defect that large quantities of materials need to be processed in batches and in stages.

[0005] Patent CN118558271A provides a device and method for rapid and continuous modification of fly ash based on non-focused microwave heating. The device structure includes a conveyor belt, a microwave generator, and a shielding shell. A coaxial line is connected to the microwave generator, and the conveyor belt is arranged below the coaxial line and inside the shielding shell to achieve continuous transportation of coal powder and modification of fly ash under the action of microwave heating.

[0006] However, the above patent cannot simulate the real geological environment conditions, and thus cannot realize the research on some characteristics of coal in the laboratory, which restricts its application in the laboratory. Summary of the Invention

[0007] In order to solve the above technical problems, the present application proposes an experimental system and method for coupling non-focused microwave radiation pyrolysis of coal samples with penetration CT scanning.

[0008] The technical solution adopted in the present application is: an experimental system for non-focused microwave radiation pyrolysis of coal samples coupled with penetration CT scanning, comprising a microwave generating system, a pyrolysis seepage cavity, a loading system, a product collection system, a data acquisition system and a cooling system, the pyrolysis seepage cavity being connected to the loading system, a coal sample being placed in the pyrolysis seepage cavity, a glass fiber septum, an upper graphite packing, a lower graphite packing, an activated carbon layer and a closed support ring being arranged inside the pyrolysis seepage cavity, wherein the closed support ring is arranged in the middle of the pyrolysis seepage cavity for wrapping the coal sample, an activated carbon layer is wrapped around the outer side of the closed support ring, an upper graphite packing and a lower graphite packing are respectively arranged on the upper and lower sides of the closed support ring and the activated carbon layer, a glass fiber septum is arranged at the top of the pyrolysis seepage cavity, and a wave absorbing component is arranged at the lower end of the coal sample; The pyrolysis seepage cavity is provided with an upper outlet, a lower outlet and a temperature measuring point in the kettle. The upper outlet and the lower outlet are both provided with flow sensors, and the temperature measuring point in the kettle is provided with a thermocouple. The loading system includes a loading frame, on which a composite oil cylinder is installed. A microwave generating system is installed on the cylinder barrel of the composite oil cylinder. Pressure sensors are respectively installed at the bottom of the glass fiber spacer and the inner side of the activated carbon layer to measure the axial pressure and confining pressure applied by the loading system. The product collection system is connected to the upper outlet through an air pipe; The data acquisition system is connected to two flow sensors, thermocouples, and two pressure sensors through wires; The cooling system is arranged at the bottom of the pyrolysis seepage cavity.

[0009] Furthermore, it also includes a pyrolysis permeation gas injection system, which is connected to the lower outlet through a gas pipe, injects permeation gas, and sets the permeation pressure.

[0010] Furthermore, the absorbing component is composed of a ceramic fiber insulation layer and a silicon carbide-based absorption layer, wherein the ceramic fiber insulation layer is used to transmit microwaves and insulate the coal sample, and the silicon carbide-based absorption layer is used to absorb microwaves that penetrate the coal sample.

[0011] Furthermore, the loading system consists of an axial loading system and a lateral loading system. An upper table and a lower table are installed on the loading frame. A composite oil cylinder is installed on the upper table. The composite oil cylinder is connected to a hydraulic pump station. The composite oil cylinder includes an inner cylinder and an annular cylinder. A cylinder barrel is arranged below the composite oil cylinder. An inner wall aluminum alloy bushing, an upper outer wall pressure head and an upper inner wall pressure head are arranged on the outside of the cylinder barrel from the inside to the outside. The pressure is transmitted from the inner cylinder in the composite oil cylinder to the upper inner wall pressure head on the cylinder barrel to provide axial pressure for the coal sample. The pressure is transmitted from the annular cylinder in the composite oil cylinder to the upper outer wall pressure head on the cylinder barrel to provide confining pressure for the coal sample.

[0012] Furthermore, the microwave generating system is composed of a microwave generator, a microwave generating end and a metal refraction plate, the microwave generator is mounted on the cylinder, and the microwave generating end extends into the cylinder; The microwaves emitted by the microwave generator are directed toward the metal refraction plate through the microwave generating end to change the transmission direction of the microwave energy, thereby heating the coal sample.

[0013] Furthermore, the upper end of the pyrolysis seepage cavity is connected to the upper end gland of the loading system through bolts, and a gasket is provided between the upper end of the cavity and the upper end gland.

[0014] Furthermore, the data acquisition system generates dynamic curves of the pressure loading process, temperature change, and pore pressure change during the test by real-time collecting and recording the temperature in the pyrolysis seepage cavity, the axial pressure and confining pressure provided by the loading system, the osmotic pressure and gas flow rate when the pyrolysis seepage gas injection system injects gas, and the gas flow rate data at the outlet, and controls and outputs them.

[0015] Furthermore, the cooling system includes a lower water cooling device, and a water inlet and a water outlet are respectively provided on both sides of the lower water cooling device.

[0016] Furthermore, the metal refraction plate is made of high-purity aluminum, the surface is anodized, and the inclination angle is 45°±2°.

[0017] A test method for coupling non-focused microwave radiation pyrolysis of coal samples with penetrant CT scanning, using the test system for coupling non-focused microwave radiation pyrolysis of coal samples with penetrant CT scanning, comprises the following steps: Step 1: Before the experiment, the coal sample was processed; Step 2: Place the coal sample into the pyrolysis seepage chamber and seal it, tightening the bolts to prevent gas leakage; Step 3: Connect the pyrolysis permeate gas injection system, product collection system and data acquisition system, and use the loading system to perform axial pressure and confining pressure loading; Step 4: inject pyrolysis atmosphere through the lower outlet, start the cooling system, start the microwave generation system to pyrolyze the coal sample, set the required pyrolysis temperature, keep the temperature for a period of time when the set pyrolysis temperature is reached, and start the product collection system to complete the collection of pyrolysis products; Step 5: Scan the pyrolyzed coal sample with a CT scanner to analyze the effect of microwave heating on the changes in the pores and cracks of the coal sample; Step 6: Start the pyrolysis permeation gas injection system to conduct a permeation experiment on the coal sample after pyrolysis, monitor, collect and process data in real time, and conduct a permeability test on the coal sample; Step 7: Use the data acquisition system to analyze and process the experimental data. At this point, the non-focused microwave radiation pyrolysis coal sample coupled penetration CT scanning test is completed.

[0018] The beneficial effects of this application compared to the prior art are: 1. This application can simulate the in-situ microwave pyrolysis state of coal samples. Specifically, the microwave absorbing component (silicon carbide-based absorption layer and ceramic fiber insulation layer) at the bottom of the cavity absorbs the transmitted microwaves, reduces reflection interference, forms a non-focused microwave field, and simulates the in-situ microwave pyrolysis of coal. Second, this application can perform real stress simulation, and the experimental data is more comprehensive. The loading system can accurately reproduce the actual stress state of the coal seam. The cavity integrates thermocouples (accuracy ±0.5°C), pressure sensors and flow sensors to monitor temperature, pressure and gas flow in real time. Combined with the PLC control system, dynamic closed-loop adjustment is achieved. The comprehensiveness of data collection far exceeds that of traditional equipment. This application integrates microwave pyrolysis, coal sample CT scanning, and permeability testing. The titanium alloy cavity (with excellent transmission properties) can be directly transferred to CT scanning without repeated coal sample disassembly, enabling triaxial stress scanning before and after pyrolysis. The lower outlet supports N2 atmosphere control, meeting the needs of multiple experiments such as permeability testing (pressure drop method) and pyrolysis gas extraction (condensation separation). Its functional scalability significantly exceeds that of a single pyrolysis device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present application will be further described below with reference to the accompanying drawings: Figure 1 A schematic diagram of the overall structure of the device provided in the embodiment of the present application; Figure 2 for Figure 1 Schematic diagram of the structure of the pyrolysis seepage cavity and the loading system; In the figure: 1 is the microwave generation system; 2 is the pyrolysis seepage cavity; 3 is the loading system; 4 is the pyrolysis seepage gas injection system; 5 is the product collection system; 6 is the data acquisition system; 7 is the cooling system; 101 is the microwave generator; 102 is the microwave generation end; 103 is the metal refraction plate; 201 is the coal sample; 202 is the upper end of the cavity; 203 is the closed support ring; 204 is the glass fiber spacer; 205 is the upper graphite packing; 206 is the lower graphite packing; 207 is the activated carbon layer; 208 is the ceramic fiber insulation layer; 209 is the silicon carbide-based absorption layer; 210 is the temperature measuring point in the kettle; 211 is the lower outlet; 212 is the upper outlet; 301 is the upper table; 302 is the lower table; 303 is the loading frame; 304 is the composite oil cylinder; 305 is the inner cylinder; 306 is the annular cylinder; 307 is the upper inner wall pressure head; 308 is the upper outer wall pressure head; 309 is the inner wall aluminum alloy bushing; 310 is the upper end pressure cover; 311 is the bolt; 312 is the gasket; 701 is the lower water cooling device; 702 is the water inlet; 703 is the water outlet. DETAILED DESCRIPTION

[0020] like Figure 1 and2 As shown, the present application provides a test system for non-focused microwave radiation pyrolysis of coal samples coupled with permeability CT scanning, which can simulate real geological environmental conditions. According to the conditions of ground stress and temperature field under the geological conditions of mineral occurrence, it can meet the requirements of simulating in-situ microwave radiation pyrolysis of coal samples in the laboratory, and performing CT scanning and permeability testing, and analyzing the pore and fracture characteristics and seepage characteristics changes of coal. It is an advanced, efficient, intuitive, reliable and safe test system.

[0021] like Figure 1 As shown, the experimental system for the non-focused microwave radiation pyrolysis of coal samples coupled with permeation CT scanning proposed in this application mainly consists of a microwave generating system 1, a pyrolysis seepage cavity 2, a loading system 3, a pyrolysis seepage gas injection system 4, a product collection system 5, a data acquisition system 6 and a cooling system 7. The pyrolysis seepage cavity 2 is an important component of the experimental system. The entire cavity is made of titanium alloy (with excellent transmission performance). The upper end 202 of the cavity is connected to the upper end pressure cover 310 of the loading system 3 by a bolt 311. A gasket 312 is provided between the upper end 202 of the cavity and the upper end pressure cover 310. After tightening the bolt 311, the airtightness of the entire cavity can be ensured; a glass fiber spacer 204, an upper graphite packing 205, a lower graphite packing 206, an activated carbon layer 207 and a closed support ring 203 are provided inside the pyrolysis seepage cavity 2 for supporting and fixing the coal sample 201; the glass fiber spacer 20 4 can transmit microwaves and transmit pressure to act on the coal sample 201 (cylindrical coal sample). The cavity is provided with an upper outlet 212, a lower outlet 211 and a temperature measuring point 210 in the kettle. The upper outlet 212 and the lower outlet 211 are both provided with flow sensors. The temperature measuring point 210 in the kettle is provided with a thermocouple to measure the flow of the gas at the upper outlet 212 and the lower outlet 211 and the temperature in the cavity in real time. A wave absorbing component is provided at the lower end of the place where the coal sample 201 is placed. The wave absorbing component consists of a ceramic fiber insulation layer 208 and a silicon carbide-based absorption layer 209. The ceramic fiber insulation layer 208 can transmit microwaves and has the function of heat preservation and heat insulation, blocking the conductive heating of the silicon carbide-based heat to the coal sample 201. The silicon carbide-based absorption layer 209 can absorb the microwaves that penetrate the coal sample 201, reduce the reflection of the microwaves in the furnace cavity, form a non-focused microwave field, and simulate the state of in-situ microwave radiation heating of the coal seam.

[0022] The microwave generating system 1 consists of a microwave generator 101, a microwave generating end 102 and a metal refraction plate 103. The microwave generator 101 can emit microwaves, which are emitted to the metal refraction plate 103 through the microwave generating end 102 to change the transmission direction of the microwave energy, thereby heating the coal sample 201. The metal refraction plate 103 is made of high-purity aluminum, and its surface is anodized to improve the microwave reflection efficiency. The inclination angle is 45°±2° to ensure that the microwaves evenly cover the surface of the coal sample 201.

[0023] The loading system 3 consists of an axial loading system and a lateral loading system. The axial loading system and the lateral loading system consist of a loading frame 303 containing an upper table 301 and a lower table 302, a composite oil cylinder 304 installed on the upper table 301, and a hydraulic pump station connected to the composite oil cylinder 304. The composite oil cylinder 304 includes an inner cylinder 305 and an annular cylinder 306. A cylinder barrel is provided below the composite oil cylinder 304. The cylinder barrel is provided with an inner wall aluminum alloy bushing 309, an upper outer wall pressure head 308 and an upper inner wall pressure head 307 from the inside to the outside. The microwave generator 101 is installed on the cylinder barrel, and the microwave generating end 102 extends into the cylinder barrel. The pressure is transmitted to the upper inner wall pressure head 307 on the cylinder barrel through the inner cylinder 305 in the composite oil cylinder 304, providing axial pressure for the coal sample 201, and the pressure is transmitted to the upper outer wall pressure head 308 on the cylinder barrel through the annular cylinder 306 in the composite oil cylinder 304, providing confining pressure for the coal sample 201.

[0024] The axial loading system transmits pressure from the inner cylinder 305 in the composite oil cylinder 304 to the upper inner wall pressure head 307 on the cylinder barrel, and applies axial pressure to the coal sample 201 through the glass fiber spacer 204; the pressurization principle of the lateral loading system is: a closed support ring 203 and an upper graphite packing 205 and a lower graphite packing 206 as a pressure transmission medium are arranged on the side of the coal sample 201, and the lateral loading of the annular cylinder 306 of the composite oil cylinder 304 is received through the upper outer wall pressure head 308 to apply confining pressure. After pressurization, the loading system 3 can provide axial pressure and confining pressure to the coal sample 201, simulating the vertical stress and horizontal stress of the coal seam underground, and restoring the real coal seam geological conditions.

[0025] Pressure sensors are respectively provided at the bottom of the glass fiber spacer 204 and the inner side of the activated carbon layer 207 for measuring the axial pressure and confining pressure applied by the loading system 3 .

[0026] The pyrolysis permeation gas injection system 4 is connected to the lower outlet 211 through a gas pipe, and can inject permeation gas (N2) to set the required permeation pressure and provide N2 atmosphere for pyrolysis.

[0027] The product collection system 5 is connected to the upper outlet 212 via an air pipe, and the condensing device therein separates the generated tar and gas for oil and gas composition analysis.

[0028] The data acquisition system 6 adopts a PLC control system, which is connected to the flow sensors and thermocouples set at the upper outlet 212, the lower outlet 211 and the temperature measuring point 210 in the kettle, as well as two pressure sensors. It collects and records data such as the temperature in the cavity, the axial pressure and confining pressure provided by the loading system 3, the osmotic pressure and gas flow rate when the pyrolysis permeation gas injection system 4 injects gas, and the gas flow rate at the outlet in real time, and generates dynamic curves of the pressure loading process, temperature change dynamic curves, and pore pressure change dynamic curves during the test process for control and output.

[0029] The cooling system 7 mainly comprises a lower water cooling device 701 . Water enters through a water inlet 702 provided on the side of the lower water cooling device 701 and flows out through a water outlet 703 opposite to the water inlet 702 .

[0030] In this embodiment, the microwave generator 101 in the microwave generating system 1 can emit an industrial standard frequency of 2.45 GHz, with a power range of 800-3000 W, which can be dynamically adjusted according to experimental requirements.

[0031] In this embodiment, the coal sample 201 may be a standard cylindrical coal sample with a diameter of 50 mm and a height of 100 mm.

[0032] In this embodiment, the pressure range of the loading system 3 is 0-50 MPa, the pressure sensor accuracy is ±0.1 MPa, and closed-loop control is supported.

[0033] In this embodiment, the pyrolysis permeate gas injection system 4 has an osmotic pressure adjustment range of 0.1-6 MPa, and a gas flow control accuracy of ±0.01 L / min.

[0034] In this embodiment, the operating temperature of the condensing device of the product collection system 5 is -20°C to 5°C, the tar separation efficiency is ≥95%, and the volume of the gas collection bag is 10 to 50L.

[0035] In this embodiment, the data acquisition system 6 acquires data from each sensor at a frequency of ≥1 Hz and generates a dynamic curve.

[0036] In the absorbing assembly of this embodiment, the thickness of the ceramic fiber insulation layer 208 is 20 mm, the thickness of the silicon carbide-based absorption layer 209 is 30 mm, and the microwave absorption rate is ≥90%.

[0037] The present application also proposes a test method for coupling non-focused microwave radiation pyrolysis of coal samples with permeability CT scanning. The above-mentioned non-focused microwave radiation pyrolysis of coal samples coupled with permeability CT scanning test system can simulate real geological environmental conditions. The method first processes the coal sample 201 to the required size for the experiment, then seals it in the pyrolysis seepage cavity 2, loads it to a set stress value through the loading system 3, sets different temperature nodes for microwave radiation heating, and when the temperature reaches the set value and stabilizes for 2 hours to complete pyrolysis, uses a CT scanner to observe changes in the pores and cracks of the coal sample 201 after pyrolysis, and conducts a CT scanning experiment. Alternatively, the pyrolysis permeation gas injection system 4 can be turned on, the required osmotic pressure for the experiment can be set, and changes in gas flow can be observed to conduct a coal sample permeability experiment. The specific implementation steps are as follows: Step 1: Before the experiment, the coal sample 201 was processed to make a standard cylindrical coal sample; Step 2: Place the coal sample 201 into the pyrolysis seepage chamber 2 and seal it, tightening the bolts 311 to prevent gas leakage; Step 3: Connect the pyrolysis permeate gas injection system 4, the product collection system 5 and the data acquisition system 6, and use the loading system 3 to perform axial pressure and confining pressure loading; Step 4: Inject pyrolysis atmosphere (N2) through the lower outlet 211, start the cooling system 7, start the microwave generation system 1 to pyrolyze the coal sample 201, set the desired pyrolysis temperature, keep the temperature for 2 hours when the set pyrolysis temperature is reached, and start the product collection system 5 to complete the collection of pyrolysis products; Step 5: Perform CT scanning on the coal sample 201 after pyrolysis to analyze the effect of microwave heating on the changes in the pores and cracks of the coal sample 201; Step 6: Start the pyrolysis permeation gas injection system 4 to conduct a permeation experiment on the coal sample 201 after pyrolysis, monitor, collect and process data in real time, and conduct a permeability test on the coal sample 201; Step 7: Analyze and process the experimental data using the data acquisition system 6. At this point, the non-focused microwave radiation pyrolysis coal sample coupled with penetration CT scanning test is completed.

[0038] The spatial resolution of the CT scanner used in this embodiment is ≤10 μm, and the scanning interval can be determined according to experimental requirements. CT scanning under three-dimensional stress can be performed according to different temperature nodes.

[0039] The test method of the present application is described below based on specific examples.

[0040] This embodiment uses a standard cylindrical coal sample with a diameter of 50 mm and a height of 100 mm as an example. The temperature loading is selected to be 450°C. The test is conducted using a non-focused microwave radiation pyrolysis coal sample coupled with a penetration CT scanning test system, including the following steps: Step 1: Before the experiment, the coal sample 201 was processed into a standard cylindrical coal sample with a diameter of 50 mm and a height of 100 mm; Step 2: Place the coal sample 201 into the pyrolysis seepage chamber 2 and seal it, tightening the bolts 311 to prevent gas leakage; Step 3: Connect all monitoring sensors and use loading system 3 to perform axial pressure and confining pressure loading. The axial pressure is set to 80 MPa and the confining pressure is set to 64 MPa. Step 4: Inject pyrolysis atmosphere (N2) through the lower outlet 211, start the microwave generation system 1 to pyrolyze the coal sample 201, set the desired pyrolysis temperature, keep the temperature for 2 hours when the set pyrolysis temperature is reached, and start the product collection system 5 to complete the collection of pyrolysis products; Step 5: Perform CT scanning on the coal sample 201 after pyrolysis to analyze the effect of microwave heating on the changes in the pores and cracks of the coal sample 201; Step 6: Start the pyrolysis permeation gas injection system 4 to conduct a permeation experiment on the coal sample 201 after pyrolysis, monitor, collect and process data in real time, and conduct a permeability test on the coal sample 201; Step 7: Analyze and process the experimental data using the data acquisition system 6. At this point, the non-focused microwave radiation pyrolysis coal sample coupled with penetration CT scanning test is completed.

[0041] In summary, the present application can be used for experimental research on microwave radiation thermal decomposition coupled with penetration CT scanning of coal rocks, etc. At the same time, the experimental system of the present application is also suitable for non-focused microwave thermal decomposition and seepage CT coupling experiments of shale and other porous media materials.

[0042] Compared with traditional devices and methods, the present application can simulate the in-situ microwave pyrolysis state of coal sample 201 by setting absorbing components around and at the bottom of the cavity, absorb microwaves that penetrate the coal sample 201, reduce the reflection interference of microwaves in the furnace cavity, and finally form a non-focused microwave heating field; at the same time, the experimental device sets a three-axis loading system for the coal sample 201 to simulate real geological conditions and conduct in-situ pyrolysis experiments; the pyrolysis seepage cavity is made of titanium alloy (with excellent transmission performance), which is convenient for in-situ CT scanning experiments of coal sample 201, and the lower outlet on the lower side of the pyrolysis seepage cavity 2 is connected to the pyrolysis seepage gas injection system 4 to inject seepage gas (N2), which is convenient for permeation experiments of coal sample 201.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A test system for unfocused microwave radiation pyrolysis of coal samples coupled with penetration CT scanning, characterized by: The invention comprises a microwave generating system (1), a pyrolysis seepage cavity (2), a loading system (3), a product collecting system (5), a data acquisition system (6) and a cooling system (7); the pyrolysis seepage cavity (2) is connected to the loading system (3); a coal sample (201) is placed in the pyrolysis seepage cavity (2); a glass fiber spacer (204), an upper graphite packing (205), a lower graphite packing (206), an activated carbon layer (207) and a closed support ring ( 203), wherein the closed support ring (203) is arranged in the middle of the pyrolysis seepage cavity (2) for wrapping the coal sample (201), the outer side of the closed support ring (203) is wrapped with an activated carbon layer (207), the upper and lower sides of the closed support ring (203) and the activated carbon layer (207) are respectively provided with an upper graphite packing (205) and a lower graphite packing (206), a glass fiber spacer (204) is arranged on the top of the pyrolysis seepage cavity (2), and a wave absorbing component is provided at the lower end of the coal sample (201); The pyrolysis seepage cavity (2) is provided with an upper outlet (212), a lower outlet (211) and a temperature measuring point (210) in the kettle. Flow sensors are provided on the upper outlet (212) and the lower outlet (211), and a thermocouple is provided on the temperature measuring point (210) in the kettle. The loading system (3) includes a loading frame (303), a composite oil cylinder (304) is installed on the loading frame (303), a microwave generating system (1) is installed on the cylinder of the composite oil cylinder (304), and pressure sensors are respectively provided at the bottom of the glass fiber spacer (204) and the inner side of the activated carbon layer (207) for measuring the axial pressure and confining pressure applied by the loading system (3); The product collection system (5) is connected to the upper outlet (212) via an air pipe; The data acquisition system (6) is connected to two flow sensors, a thermocouple, and two pressure sensors via wires; The cooling system (7) is arranged at the bottom of the pyrolysis seepage cavity (2).

2. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 1, characterized in that: It also includes a pyrolysis permeation gas injection system (4), which is connected to the lower outlet (211) through a gas pipe, injects permeation gas, and sets the permeation pressure.

3. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 2, characterized in that: The absorbing component consists of a ceramic fiber insulation layer (208) and a silicon carbide-based absorption layer (209), wherein the ceramic fiber insulation layer (208) is used to transmit microwaves and provide thermal insulation for the coal sample (201), and the silicon carbide-based absorption layer (209) is used to absorb microwaves that penetrate the coal sample (201).

4. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 2, characterized in that: The loading system (3) is composed of an axial loading system and a lateral loading system. An upper table (301) and a lower table (302) are installed on the loading frame (303). A composite oil cylinder (304) is installed on the upper table (301). The composite oil cylinder (304) is connected to a hydraulic pump station. The composite oil cylinder (304) includes an inner cylinder (305) and an annular cylinder (306). A cylinder barrel is provided below the composite oil cylinder (304). The outer side of the cylinder barrel is from the inner to the outer side. An inner wall aluminum alloy bushing (309), an upper outer wall pressure head (308) and an upper inner wall pressure head (307) are provided on the outside. Pressure is transmitted to the upper inner wall pressure head (307) on the cylinder barrel through the inner cylinder (305) in the composite oil cylinder (304), thereby providing axial pressure for the coal sample (201). Pressure is transmitted to the upper outer wall pressure head (308) on the cylinder barrel through the annular cylinder (306) in the composite oil cylinder (304), thereby providing confining pressure for the coal sample (201).

5. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 4, characterized in that: The microwave generating system (1) is composed of a microwave generator (101), a microwave generating end (102), and a metal refraction plate (103); the microwave generator (101) is mounted on the cylinder, and the microwave generating end (102) extends into the cylinder; The microwaves emitted by the microwave generator (101) are directed toward the metal refraction plate (103) through the microwave generating end (102) to change the transmission direction of the microwave energy, thereby heating the coal sample (201).

6. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 2, characterized in that: The upper end (202) of the pyrolysis seepage cavity (2) is connected to the upper end pressure cover (310) of the loading system (3) via bolts (311), and a gasket (312) is provided between the upper end (202) of the cavity and the upper end pressure cover (310).

7. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 2, characterized in that: The data acquisition system (6) collects and records the temperature in the pyrolysis seepage cavity (2), the axial pressure and confining pressure provided by the loading system (3), the osmotic pressure and gas flow rate when the pyrolysis seepage gas injection system (4) injects gas, and the gas flow rate data at the outlet in real time, and generates a dynamic curve of the pressure loading process, a dynamic curve of the temperature change, and a dynamic curve of the pore pressure change during the test, and controls and outputs them.

8. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 2, characterized in that: The cooling system (7) comprises a lower water cooling device (701), and a water inlet (702) and a water inlet (702) are respectively provided on both sides of the lower water cooling device (701).

9. The test system for coal sample pyrolysis by unfocused microwave radiation coupled with penetration CT scanning according to claim 5, characterized in that: The metal refraction plate (103) is made of high-purity aluminum, the surface of which is anodized, and the inclination angle is 45°±2°.

10. A method for testing coal samples by unfocused microwave radiation pyrolysis coupled with penetrant CT scanning, using the test system for unfocused microwave radiation pyrolysis coupled with penetrant CT scanning according to any one of claims 2 to 9, characterized in that: The following steps are involved: Step 1: Before the experiment, the coal sample (201) was processed; Step 2: Place the coal sample (201) into the pyrolysis seepage cavity (2) and seal it, and tighten the bolts (311) to prevent gas leakage; Step 3: Connect the pyrolysis permeation gas injection system (4), the product collection system (5) and the data acquisition system (6), and use the loading system (3) to perform axial pressure and confining pressure loading; Step 4: injecting pyrolysis atmosphere through the lower outlet (211), turning on the cooling system (7), starting the microwave generating system (1) to pyrolyze the coal sample (201), setting the desired pyrolysis temperature, keeping the temperature for a period of time when the set pyrolysis temperature is reached, and turning on the product collecting system (5) to complete the collection of pyrolysis products; Step 5: Scan the pyrolyzed coal sample (201) through a CT scanner to analyze the effect of microwave heating on the changes in pores and cracks in the coal sample (201); Step 6: Start the pyrolysis permeation gas injection system (4), conduct a permeation experiment on the coal sample (201) after pyrolysis, monitor, collect and process data in real time, and conduct a permeability test on the coal sample (201); Step 7: Analyze and process the experimental data using the data acquisition system (6). At this point, the non-focused microwave radiation pyrolysis coal sample coupled with penetration CT scanning test is completed.

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