Coal sample temperature change resistivity testing device and using method thereof

Abstract

The invention provides a coal sample temperature change resistivity testing device and a using method thereof, and relates to the technical field of petrophysics and experimental geophysics. The device comprises an insulation and heat preservation device used for providing an insulation environment and a heat preservation environment; the shaft type sample bin is arranged in the insulation heat preservation device and is used for containing a test coal sample column; the transmission mechanism is used for driving the shaft type sample bin to rotate; the resistivity tester is electrically coupled with the test coal sample column to measure the resistivity of the test coal sample column in real time; the temperature rising device is arranged in the insulation and heat preservation device and is thermally coupled with the test coal sample column to realize heating; the thermodetector is arranged in the insulation heat preservation device and is thermally coupled with the test coal sample column to measure the temperature in real time; and the chassis is used for fixing and supporting the resistivity tester, the heating device and the thermodetector. According to the method, the resistivity of the prepared standard coal sample can be accurately and continuously measured in a controllable temperature field, and key data is provided for researching the rule that the coal electrical property changes along with the temperature.

Description

Technical Field

[0001] This invention relates to the fields of rock physics and experimental geophysics, and in particular to a device for testing the temperature-dependent resistivity of coal samples and its usage. Background Technology

[0002] Coal, as a complex porous medium, exhibits extremely sensitive resistivity to temperature changes. In-depth research into the variation of coal sample resistivity with temperature is of significant theoretical value and has broad potential applications for understanding the evolution of the physical properties of coal seams under thermal influence and revealing the electrical response mechanisms in related geological processes. Currently, experimental apparatus used to measure coal resistivity often faces the following technical limitations:

[0003] First, sample preparation is the primary factor affecting measurement accuracy. Current technologies often use natural coal lumps or simply crushed coal particles as test samples. Natural coal lumps have uneven mineral composition, well-developed fissures, and low mechanical strength, making them difficult to process into samples with smooth surfaces and regular geometric dimensions. This results in poor coupling between the sample and the electrode during testing, introducing significant contact resistance and severely interfering with the accurate measurement of resistivity.

[0004] Secondly, the uniformity and accuracy of temperature control are crucial. Many existing devices use static, fixed-point heating with a fixed heat source, resulting in uneven heating of different areas of the coal sample and a large internal temperature gradient. This uneven temperature field cannot accurately reflect the electrical changes of the medium under slow, uniform heating conditions, and the obtained data is difficult to accurately characterize the constitutive relationship between resistivity and temperature.

[0005] Furthermore, the stability of the coupling between the electrode and the coal sample at high temperatures faces challenges. Conventional electrode coupling materials or contact methods may experience increased contact resistance or even failure at elevated temperatures due to mismatched coefficients of thermal expansion, oxidation, or decreased adhesion. This can cause test signal drift or interruption, affecting the continuity and reliability of the data.

[0006] In summary, existing technologies for testing the temperature-dependent resistivity of coal samples have significant shortcomings in terms of sample standardization, temperature field uniformity, and electrode contact stability. There is an urgent need for a dedicated device that can provide stable, reliable, and efficient testing. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention, based on an in-depth analysis of the need for precise measurement of electrical parameters of coal samples under a controllable temperature field, proposes a coal sample temperature-varying resistivity testing device and its usage method. The aim is to provide an experimental device capable of accurately and continuously measuring the resistivity of artificially prepared standard coal samples under a controllable temperature field. This device is particularly suitable for studying the variation of coal electrical parameters with temperature, providing crucial experimental data for investigating the influence of temperature on the electrical properties of coal.

[0008] On the one hand, the present invention proposes a coal sample temperature-varying resistivity testing device, which includes: an insulation and heat preservation device, a shaft-type sample chamber, a transmission mechanism, a resistivity tester, a heating device, a temperature measuring instrument, and a base frame;

[0009] The insulation and heat preservation device is used to provide an insulating and heat preservation environment for the testing process; the base frame is fixedly connected to the outer wall of the insulation and heat preservation device, and the supporting surface of the base frame and the bottom surface of the insulation and heat preservation device are located on the same horizontal plane, which is used to fix and support the resistivity tester, the heating device and the temperature measuring instrument.

[0010] The axial sample chamber is located inside the insulation and heat preservation device and is used to hold the test coal sample column;

[0011] The drive end of the transmission mechanism is connected to the shaft-type sample chamber and is used to drive the rotation of the shaft-type sample chamber.

[0012] The resistivity tester is electrically coupled to the test coal sample column in the axial sample chamber, and is used to measure the resistivity of the test coal sample column in real time.

[0013] The heating temperature sensing element in the heating device is installed inside the insulating and heat preservation device and is thermally coupled to the test coal sample column in the axial sample chamber for heating the test coal sample column.

[0014] The temperature measuring element of the thermometer is installed inside the insulation and heat preservation device, and is used to measure the internal temperature of the insulation and heat preservation device in real time and as the temperature of the test coal sample column.

[0015] Furthermore, the insulation and heat preservation device includes: an insulation and heat preservation box and an openable and closable insulation and heat preservation cover; wherein the side wall of the insulation and heat preservation box is provided with a channel for installing and removing the shaft-type sample chamber, and the channel is closed by the insulation and heat preservation cover; a second bearing mounting hole is provided at the center of the insulation and heat preservation cover; a first bearing mounting hole coaxial with the second bearing mounting hole is provided on the side wall of the insulation and heat preservation box opposite to the insulation and heat preservation cover.

[0016] A first bearing housing is fixedly installed in the first bearing mounting hole; a first high-temperature resistant sealed bearing is installed in the first bearing housing; a second bearing housing is fixedly installed in the second bearing mounting hole; a second high-temperature resistant sealed bearing is installed in the second bearing housing.

[0017] Furthermore, the axial sample chamber includes: an insulating chamber body, an insulating chamber cover, a first electrode plate, a second electrode plate, a first rotating electrode shaft, and a second rotating electrode shaft;

[0018] The insulating chamber is used to hold the coal sample column; the insulating chamber cover is snapped into the insulating chamber to seal the insulating chamber; the first electrode plate and the second electrode plate are both located inside the insulating chamber, and the first electrode plate is coupled to one end of the test coal sample column, and the second electrode plate is coupled to the other end of the test coal sample column, for measuring resistivity at both ends of the test coal sample column.

[0019] The first electrode plate is also fixedly connected to one end of the first rotating electrode shaft, and the other end of the first rotating electrode shaft passes through the first high-temperature resistant sealed bearing; the second electrode plate is also fixedly connected to one end of the second rotating electrode shaft, and the other end of the second rotating electrode shaft passes through the second high-temperature resistant sealed bearing.

[0020] Furthermore, the transmission mechanism includes: a motor, a first rotating wheel, a second rotating wheel, a belt, a first conductive slip ring, a second conductive slip ring, and a fixed frame;

[0021] The motor is fixed to the base frame and provides rotational force to the drive shaft sample chamber; the first rotating wheel is mounted on the output shaft of the motor; the second rotating wheel is fixedly mounted on the first rotating electrode shaft and is coaxial with the first rotating electrode shaft; the first rotating wheel and the second rotating wheel are connected by belt drive; the rotating part of the first conductive slip ring is coaxially and electrically connected to the first rotating electrode shaft, and the first conductive slip ring is fixedly connected to the insulating and heat-preserving box body through a fixing frame; the rotating part of the second conductive slip ring is coaxially and electrically connected to the second rotating electrode shaft.

[0022] Furthermore, the resistivity tester includes: a resistivity measuring host, a first copper wire, and a second copper wire; wherein the positive terminal of the resistivity measuring host is connected to the stationary portion of the first conductive slip ring via the first copper wire; and the negative terminal of the resistivity measuring host is connected to the stationary portion of the second conductive slip ring via the second copper wire.

[0023] Furthermore, the heating device includes: a programmable temperature controller and a heating temperature sensing element; wherein the programmable temperature controller is fixedly installed at the connection between the outside of the insulation box and the base frame; the heating temperature sensing element is fixedly installed inside the insulation box and is used to heat the internal space of the insulation box, and controls the heating process by feeding back a temperature measurement signal to the programmable temperature controller; the programmable temperature controller is electrically connected to the heating temperature sensing element.

[0024] Furthermore, the temperature measuring instrument includes a temperature measuring host, a thermocouple, and a temperature measuring connection line; wherein the temperature measuring host is fixed on the base frame; the thermocouple is fixed inside the insulating box, and the thermocouple is connected to the temperature measuring host through the temperature measuring connection line.

[0025] On the other hand, the present invention proposes a method for using a coal sample temperature-varying resistivity testing device, the method comprising the following steps:

[0026] Fresh coal blocks are collected and processed into coal powder according to predefined grinding standards, and the coal powder is pressed into shape to prepare a test coal sample column;

[0027] The test coal sample column is loaded into the insulating chamber and the insulating chamber cover is pressed tightly. Then the shaft sample chamber is loaded into the insulating and heat-preserving device, and the resistivity tester, heating device and temperature measuring instrument are connected and the parameters are set.

[0028] The test coal sample column is heated at a constant speed to the preset temperature, and the resistivity and temperature of the test coal sample column are measured simultaneously.

[0029] Furthermore, the predefined grinding standard is as follows: the particle size of the coal powder is between 0.05mm and 5mm, and the particles of 0.05mm-0.5mm in the coal powder are not less than 50%;

[0030] The shape of the test coal sample column matches the shape of the inner cavity of the insulating chamber.

[0031] The beneficial effects of adopting the above technical solution are as follows:

[0032] 1. High measurement accuracy and reliable data: The device of this invention prepares standard coal samples using a high-pressure tablet press, fundamentally solving the problems of poor electrode contact coupling and large test errors caused by loose structure and uneven surface. It improves the uniformity of coal samples and the electrode contact effect, and solves the problems of poor coupling stability and conductivity decay between electrodes and coal samples under high temperature conditions. Through structural design optimization, the coupling reliability is improved, ensuring tight coupling between electrodes and coal samples, significantly reducing contact resistance, and making the measurement results more accurately reflect the true bulk resistivity of the coal sample.

[0033] 2. Uniform Temperature Field and Realistic Process: This invention innovatively adopts a dynamic heating design of motor drive, synchronous belt transmission, and sample chamber rotation. Combined with the insulation of the insulated enclosure and the uniform heat distribution of the bottom heating element, it effectively overcomes the problems of localized overheating and disordered temperature field distribution in static heating modes. The temperature control unit precisely adjusts the target temperature and heating rate to ensure uniform heating of the coal sample throughout the heating process.

[0034] 3. Accurate data synchronization and strong correlation: Through integrated system design, the device of this invention realizes real-time and synchronous acquisition of coal sample temperature and resistivity, ensuring that each resistivity data point corresponds to an accurate temperature value. Attached Figure Description

[0035] Figure 1This is a schematic diagram of a coal sample temperature-varying resistivity testing device in this embodiment (viewpoint 1).

[0036] Figure 2 This is a schematic diagram of the structure of a coal sample temperature-varying resistivity testing device in this embodiment (viewpoint 2).

[0037] Figure 3 This is a flowchart illustrating the usage method of a coal sample temperature-varying resistivity testing device in this embodiment;

[0038] In the diagram: 101-Insulated box; 102-Insulated cover; 201-Insulated chamber; 202-Insulated chamber cover; 203-First electrode plate; 204-Second electrode plate; 205-First rotating electrode shaft; 206-Second rotating electrode shaft; 301-Motor; 302-First rotating wheel; 303-Second rotating wheel; 304-Belt; 305-First conductive slip ring; 306-Second conductive slip ring; 307-Fixing frame; 401-Resistivity measuring host; 4011-Positive terminal; 4012-Negative terminal; 402-First copper wire; 403-Second copper wire; 501-Programmable temperature controller; 502-Heating temperature sensing element; 601-Temperature measuring host; 602-Thermocouple; 603-Temperature measuring connection wire; 7-Base frame. Detailed Implementation

[0039] To facilitate understanding of this application, specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. The following embodiments are illustrative of the invention but are not intended to limit its scope. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0040] Example 1:

[0041] This embodiment provides a coal sample temperature-dependent resistivity testing device, such as... Figure 1 and Figure 2 As shown, the device includes: an insulation and heat preservation device, a shaft-type sample chamber, a transmission mechanism, a resistivity tester, a heating device, a temperature measuring instrument, and a base frame 7;

[0042] The insulation and heat preservation device is used to provide an insulating and heat preservation environment for the testing process; the base frame 7 is fixedly connected to the outer wall of the insulation and heat preservation device, and the supporting surface of the base frame 7 is on the same horizontal plane as the bottom surface of the insulation and heat preservation device, which is used to fix and support the resistivity tester, the heating device and the temperature measuring instrument.

[0043] To achieve both insulation and thermal insulation, in this embodiment, the housing of the insulation and thermal insulation device can be made of alloy material, and the inner surface of the housing can be coated with a functional coating of insulation and thermal insulation material with high electrical insulation and low thermal radiation coefficient, such as a ceramic coating, to provide dual protection of electrical insulation and thermal insulation in addition to structural strength.

[0044] The insulation and heat preservation device includes: an insulation and heat preservation box 101 and an openable and closable insulation and heat preservation cover 102; wherein the side wall of the insulation and heat preservation box 101 is provided with a channel for installing and removing the shaft-type sample chamber, and the channel is closed by the insulation and heat preservation cover 102; a second bearing mounting hole is provided at the center of the insulation and heat preservation cover 102; a first bearing mounting hole coaxial with the second bearing mounting hole is provided on the side wall of the insulation and heat preservation box 101 opposite to the insulation and heat preservation cover 102.

[0045] In this embodiment, the insulating cover 102 and the side wall of the insulating box 101 are pressed and sealed together by bolts, nuts or quick-release locks (such as cam locks or latch locks).

[0046] A first bearing housing is fixedly installed in the first bearing mounting hole; a first high-temperature resistant sealed bearing is installed in the first bearing housing; a second bearing housing is fixedly installed in the second bearing mounting hole; a second high-temperature resistant sealed bearing is installed in the second bearing housing.

[0047] The axial sample chamber is located inside the insulation and heat preservation device and is used to hold the test coal sample column.

[0048] The axial sample chamber includes: an insulating chamber body 201, an insulating chamber cover 202, a first electrode plate 203, a second electrode plate 204, a first rotating electrode shaft 205, and a second rotating electrode shaft 206.

[0049] The insulating chamber 201 is used to hold the coal sample column; the insulating chamber cover 202 is snapped into the insulating chamber 201 to seal the insulating chamber 201; the first electrode plate 203 and the second electrode plate 204 are both located inside the insulating chamber 201, and the first electrode plate 203 is coupled to one end of the test coal sample column, and the second electrode plate 204 is coupled to the other end of the test coal sample column, for measuring resistivity at both ends of the test coal sample column.

[0050] The first electrode plate 203 is also fixedly connected to one end of the first rotating electrode shaft 205, and the other end of the first rotating electrode shaft 205 passes through the first high-temperature resistant sealed bearing; the second electrode plate 204 is also fixedly connected to one end of the second rotating electrode shaft 206, and the other end of the second rotating electrode shaft 206 passes through the second high-temperature resistant sealed bearing.

[0051] In this embodiment, the insulating cover 202 is used to seal the insulating chamber 201 to prevent the test coal sample column from falling off or being disturbed by the external environment during rotation. After the test coal sample column is inserted, axial manual pressure is applied to make the left and right end faces of the inner side of the insulating chamber 201 fit tightly against the first electrode plate 203 and the second electrode plate 204, respectively. The static friction generated by the contact surface is used to transmit the rotational torque, so that the insulating chamber 201 rotates synchronously with the first rotating electrode shaft 205 and the second rotating electrode shaft 206.

[0052] The drive end of the transmission mechanism is connected to the shaft-type sample chamber and is used to drive the rotation of the shaft-type sample chamber.

[0053] In this embodiment, the transmission mechanism ensures that the coal sample column is heated evenly by rotating the drive shaft sample chamber.

[0054] The transmission mechanism includes: a motor 301, a first rotating wheel 302, a second rotating wheel 303, a belt 304, a first conductive slip ring 305, a second conductive slip ring 306, and a fixed frame 307.

[0055] The motor 301 is fixed on the base frame 7 and is used to provide rotational force for the drive shaft sample chamber; the first rotating wheel 302 is mounted on the output shaft of the motor 301; the second rotating wheel 303 is fixedly mounted on the first rotating electrode shaft 205 and is coaxially arranged with the first rotating electrode shaft 205; the first rotating wheel 302 and the second rotating wheel 303 are connected by a belt 304; the rotating part of the first conductive slip ring 305 is coaxially and electrically connected to the first rotating electrode shaft 205, and the first conductive slip ring 305 is fixedly connected to the insulating and heat-preserving box 101 through a fixing frame 307; the rotating part of the second conductive slip ring 306 is coaxially and electrically connected to the second rotating electrode shaft 206.

[0056] In this embodiment, when the transmission mechanism is working, the motor 301 drives the first rotating wheel 302 to rotate, which in turn drives the second rotating wheel 303 and the first rotating electrode shaft 205 fixed thereto to rotate synchronously via the belt 304, thereby precisely and smoothly driving the axial sample chamber to rotate. A first conductive slip ring 305 is provided to prevent the first copper wire 402 connected to the resistivity meter from becoming entangled due to the rotation of the first rotating electrode shaft 205. A second conductive slip ring 306 is provided to prevent the second copper wire 403 connected to the resistivity meter from becoming entangled due to the rotation of the second rotating electrode shaft 206.

[0057] The measuring end of the resistivity tester is electrically coupled to the test coal sample column in the axial sample chamber, and is used to measure the resistivity of the test coal sample column in real time.

[0058] The resistivity tester includes: a resistivity measuring host 401, a first copper wire 402, and a second copper wire 403; wherein the positive terminal 4011 of the resistivity measuring host 401 is connected to the stationary part of the first conductive slip ring 305 through the first copper wire 402; and the negative terminal 4012 of the resistivity measuring host 401 is connected to the stationary part of the second conductive slip ring 306 through the second copper wire 403.

[0059] The heating temperature sensing element in the heating device is located inside the insulating and heat-preserving device and is thermally coupled to the test coal sample column in the axial sample chamber for heating the test coal sample column.

[0060] The heating device includes a programmable temperature controller 501 and a heating temperature sensing element 502; wherein the programmable temperature controller 501 is fixedly installed on the outside of the insulating box 101 at the connection with the base frame 7; the heating temperature sensing element 502 is fixedly installed inside the insulating box 101, used to heat the internal space of the insulating box 101, and to control the heating process by feeding back a temperature measurement signal to the programmable temperature controller 501; the programmable temperature controller 501 is electrically connected to the heating temperature sensing element 502.

[0061] In this embodiment, the programmable temperature controller 501 is used to input the target temperature and the heating rate, and to control the heating temperature sensing element 502 to heat up according to the target temperature and the heating rate.

[0062] The temperature measuring element of the thermometer is installed inside the insulation and heat preservation device, and is used to measure the internal temperature of the insulation and heat preservation device in real time and as the temperature of the test coal sample column.

[0063] The temperature measuring instrument includes a temperature measuring host 601, a thermocouple 602, and a temperature measuring connection line 603; wherein the temperature measuring host 601 is fixed on the base frame 7; the thermocouple 602 is fixed inside the insulating and heat-preserving box 101, and the thermocouple 602 is connected to the temperature measuring host 601 through the temperature measuring connection line 603.

[0064] In this embodiment, thermocouple 602 serves as the temperature-sensing element of the thermometer. The temperature measuring host 601 measures and displays the temperature of the environment inside the insulating box 101 containing the coal sample column in real time during the experiment via thermocouple 602. It should be noted that by setting the target temperature of 800℃ and the heating rate of 2℃ / min for the programmable temperature controller 501, a slow and controllable heating condition is achieved inside the insulating device, allowing sufficient time for heat radiation and heat conduction through the internal air / medium. This ensures that the thermocouple 602 and the test coal sample column are heated simultaneously and uniformly. Therefore, in this embodiment, the temperature data obtained by the thermometer is directly used as the actual temperature of the test coal sample column.

[0065] The base frame 7 is used to fix the insulation and heat preservation device, the transmission mechanism, the resistivity measuring host 401, the programmable temperature controller 501, and the temperature measuring host 601.

[0066] Example 2:

[0067] This embodiment describes the method of using a coal sample temperature-varying resistivity testing device, such as... Figure 3 As shown, the method includes the following steps:

[0068] Fresh coal blocks are collected and processed into coal powder according to predefined grinding standards. The coal powder is then pressed into a test coal sample column.

[0069] The predefined grinding standard is: the particle size of the coal powder is between 0.05mm and 5mm, and the particles of 0.05mm-0.5mm in the coal powder are not less than 50%.

[0070] In this embodiment, 5 kg of fresh coal was collected, crushed, and ground in the laboratory to form coal powder. To ensure that the prepared test coal sample has sufficient structural strength, a uniform conductive contact surface, and can truly reflect the electrical properties of the macroscopic coal body, this embodiment limits the coal powder particle size range to 0.05 mm-5 mm, and requires that the proportion of particles of 0.05 mm-0.5 mm is not less than 50%.

[0071] The shape of the test coal sample column matches the inner cavity shape of the insulating chamber 201.

[0072] In this embodiment, after the obtained coal powder is uniformly stirred, the coal powder is loaded into a high-pressure tablet press and a pressure of 20 MPa is applied to make the coal powder into a test coal sample column that matches the shape of the insulating chamber 201.

[0073] The test coal sample column is loaded into the insulating chamber 201 and the insulating chamber cover 202 is pressed tightly. Then the shaft sample chamber is loaded into the insulating and heat-preserving device, and the resistivity tester, heating device and temperature measuring instrument are connected and the parameters are set.

[0074] In this embodiment, the insulating cover 102 is opened, the shaft-type sample chamber is taken out, the insulating chamber cover 202 is opened, the prepared coal sample column is filled into the insulating chamber 201, the insulating chamber cover 202 is pressed tight, the shaft-type sample chamber containing the coal sample column is placed into the insulating box 101, and the insulating cover 102 is fastened for testing.

[0075] The test coal sample column is heated at a constant speed to the preset temperature, and the resistivity and temperature of the test coal sample column are measured simultaneously.

[0076] In this embodiment, by setting the target temperature of the programmable temperature controller 501 to 800℃ and the heating rate to 2℃ / min, the transmission mechanism, resistivity tester, heating device and temperature measuring instrument are started simultaneously. The temperature measuring host 601 records the temperature of the environment where the test coal sample column is located in real time during the heating process, and the resistivity measuring host 401 records the resistivity of the test coal sample column in real time during the heating process.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the present invention.

Claims

1. A device for testing the temperature-dependent resistivity of coal samples, characterized in that, The device includes: an insulation and heat preservation device, a shaft-type sample chamber, a transmission mechanism, a resistivity tester, a heating device, a temperature measuring instrument, and a base frame; The insulation and heat preservation device is used to provide an insulating and heat preservation environment for the testing process; the base frame is fixedly connected to the outer wall of the insulation and heat preservation device, and the supporting surface of the base frame and the bottom surface of the insulation and heat preservation device are located on the same horizontal plane, which is used to fix and support the resistivity tester, the heating device and the temperature measuring instrument. The axial sample chamber is located inside the insulation and heat preservation device and is used to hold the test coal sample column; The drive end of the transmission mechanism is connected to the shaft-type sample chamber and is used to drive the rotation of the shaft-type sample chamber. The measuring end of the resistivity tester is electrically coupled to the test coal sample column in the axial sample chamber, and is used to measure the resistivity of the test coal sample column in real time. The heating temperature sensing element in the heating device is installed inside the insulating and heat preservation device and is thermally coupled to the test coal sample column in the axial sample chamber for heating the test coal sample column. The temperature measuring element of the thermometer is installed inside the insulation and heat preservation device, and is used to measure the internal temperature of the insulation and heat preservation device in real time and as the temperature of the test coal sample column.

2. The coal sample temperature-varying resistivity testing device according to claim 1, characterized in that, The insulation and heat preservation device includes: an insulation and heat preservation box and an openable and closable insulation and heat preservation cover; wherein the side wall of the insulation and heat preservation box is provided with a channel for installing and removing the shaft-type sample chamber, and the channel is closed by the insulation and heat preservation cover; a second bearing mounting hole is provided at the center of the insulation and heat preservation cover; a first bearing mounting hole coaxial with the second bearing mounting hole is provided on the side wall of the insulation and heat preservation box opposite to the insulation and heat preservation cover. A first bearing housing is fixedly installed in the first bearing mounting hole; a first high-temperature resistant sealed bearing is installed in the first bearing housing; a second bearing housing is fixedly installed in the second bearing mounting hole; a second high-temperature resistant sealed bearing is installed in the second bearing housing.

3. The coal sample temperature-varying resistivity testing device according to claim 2, characterized in that, The axial sample chamber includes: an insulating chamber body, an insulating chamber cover, a first electrode plate, a second electrode plate, a first rotating electrode shaft, and a second rotating electrode shaft; The insulating chamber is used to hold the coal sample column; the insulating chamber cover is snapped into the insulating chamber to seal the insulating chamber; the first electrode plate and the second electrode plate are both located inside the insulating chamber, and the first electrode plate is coupled to one end of the test coal sample column, and the second electrode plate is coupled to the other end of the test coal sample column, for measuring resistivity at both ends of the test coal sample column. The first electrode plate is also fixedly connected to one end of the first rotating electrode shaft, and the other end of the first rotating electrode shaft passes through the first high-temperature resistant sealed bearing; the second electrode plate is also fixedly connected to one end of the second rotating electrode shaft, and the other end of the second rotating electrode shaft passes through the second high-temperature resistant sealed bearing.

4. The coal sample temperature-varying resistivity testing device according to claim 3, characterized in that, The transmission mechanism includes: a motor, a first rotating wheel, a second rotating wheel, a belt, a first conductive slip ring, a second conductive slip ring, and a fixed frame; The motor is fixed to the base frame and provides rotational force to the drive shaft sample chamber; the first rotating wheel is mounted on the output shaft of the motor; the second rotating wheel is fixedly mounted on the first rotating electrode shaft and is coaxial with the first rotating electrode shaft; the first rotating wheel and the second rotating wheel are connected by belt drive; the rotating part of the first conductive slip ring is coaxially and electrically connected to the first rotating electrode shaft, and the first conductive slip ring is fixedly connected to the insulating and heat-preserving box body through a fixing frame; the rotating part of the second conductive slip ring is coaxially and electrically connected to the second rotating electrode shaft.

5. The coal sample temperature-varying resistivity testing device according to claim 4, characterized in that, The resistivity tester includes: a resistivity measuring host, a first copper wire, and a second copper wire; wherein the positive terminal of the resistivity measuring host is connected to the stationary portion of a first conductive slip ring via the first copper wire; and the negative terminal of the resistivity measuring host is connected to the stationary portion of a second conductive slip ring via the second copper wire.

6. The coal sample temperature-varying resistivity testing device according to claim 5, characterized in that, The heating device includes a programmable temperature controller and a heating temperature sensing element; wherein the programmable temperature controller is fixedly installed at the connection between the outside of the insulation box and the base frame; the heating temperature sensing element is fixedly installed inside the insulation box and is used to heat the internal space of the insulation box, and controls the heating process by feeding back a temperature measurement signal to the programmable temperature controller; the programmable temperature controller is electrically connected to the heating temperature sensing element.

7. The coal sample temperature-varying resistivity testing device according to claim 6, characterized in that, The temperature measuring instrument includes a temperature measuring host, a thermocouple, and a temperature measuring connection line; wherein the temperature measuring host is fixed on the base frame; the thermocouple is fixed inside the insulating box, and the thermocouple is connected to the temperature measuring host through the temperature measuring connection line.

8. A method of using a coal sample temperature-dependent resistivity testing device, implemented using the coal sample temperature-dependent resistivity testing device according to any one of claims 1-7, characterized in that, This method includes the following steps: Fresh coal blocks are collected and processed into coal powder according to predefined grinding standards, and the coal powder is pressed into shape to prepare a test coal sample column; The test coal sample column is loaded into the insulating chamber and the insulating chamber cover is pressed tightly. Then the shaft sample chamber is loaded into the insulating and heat-preserving device, and the resistivity tester, heating device and temperature measuring instrument are connected and the parameters are set. The test coal sample column is heated at a constant speed to the preset temperature, and the resistivity and temperature of the test coal sample column are measured simultaneously.

9. The method of using the coal sample temperature-varying resistivity testing device according to claim 8, characterized in that, The predefined grinding standard is as follows: the particle size of the coal powder is between 0.05mm and 5mm, and the particles of 0.05mm-0.5mm in the coal powder shall not be less than 50%; The shape of the test coal sample column matches the shape of the inner cavity of the insulating chamber.

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