Coal underground gasification physical simulation device and method considering stress direction

Abstract

The invention belongs to the technical field of coal underground gasification simulation experiments, and discloses a coal underground gasification physical simulation device and method considering the stress direction, the coal underground gasification physical simulation device comprises a support frame, and a high temperature resistant simulation cabin is movably arranged on the support frame; the high-temperature-resistant simulation bin comprises a simulation bin body movably erected on a supporting frame, the simulation bin body is filled with a coal sample, and the side wall of the simulation bin body is provided with a horizontal pressurization assembly used for conducting horizontal plate pressurization on the coal sample. A simulation bin top cover is arranged at the top end of the simulation bin body in a sealing manner, and a vertical pressurizing assembly for vertically pressurizing a coal sample is arranged on the simulation bin top cover; a plurality of auxiliary components for assisting simulation experiments are arranged at the bottom end of the simulation bin body. The device is simple in structure, can artificially simulate and control the underground gasification process of a coal sample, explores gasification furnace cavity expansion control factors and technologies under a real stress field condition, and can provide physical experiment reference and basis for application of coal underground gasification engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of underground coal gasification simulation experiments, and in particular to an underground coal gasification physical simulation device and method taking stress direction into consideration. Background Art

[0002] The expansion and stabilization of the gasification furnace chamber is a key research direction in the field of underground coal gasification. The industry mainly uses physical simulation and numerical simulation to analyze the expansion law, scale, impact range and control mechanism of the gasification furnace chamber under geological conditions.

[0003] Physical simulation can intuitively display the physical phenomena and processes of UCG, and is closer to the actual engineering situation. However, the current physical simulation of UCG stress field only considers the stress magnitude, and it is uniform stress, and there is no physical simulation device that considers the stress field type and horizontal stress direction; at the same time, the expansion of the UCG gasification furnace chamber is affected by the gasification process and geological conditions, among which the stress field has an important control effect on the seepage of the gasifier, the expansion of thermal cracks, and the stability of the roof. However, there is a lack of physical simulation devices and methods that consider the control effect of the stress field type and the horizontal stress direction on the expansion of the UCG gasification furnace chamber.

[0004] Therefore, the present application designs a physical simulation device and method for underground coal gasification that takes stress direction into consideration to solve the above-mentioned technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a physical simulation device and method for underground coal gasification taking stress direction into consideration, so as to realize the research and characterization of the expansion characteristics of the UCG gasification furnace chamber under different stress fields and different horizontal stress direction constraints.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a physical simulation device for underground coal gasification taking stress direction into consideration, comprising a support frame, on which a high temperature resistant simulation chamber is movably arranged, and the high temperature resistant simulation chamber is used to perform a gasification simulation experiment on a coal sample;

[0007] The high temperature resistant simulation bin bag is movably mounted on a simulation bin body on the support frame, the coal sample is loaded in the simulation bin body, and a horizontal pressurizing component for pressurizing the coal sample through a horizontal plate is arranged on the side wall of the simulation bin body;

[0008] The top of the simulation bin body is sealed with a simulation bin cover, and the simulation bin cover is provided with a vertical pressurizing component for vertically pressurizing the coal sample;

[0009] The bottom end of the simulation chamber body is provided with a plurality of auxiliary components for assisting the simulation experiment.

[0010] Preferably, the vertical pressurizing assembly comprises a vertical pressurizing piston movably arranged on the top cover of the simulation bin; the vertical pressurizing piston extends into the simulation bin body and vertically pressurizes the top of the coal sample through a vertical pressure bearing.

[0011] Preferably, the simulation bin top cover is provided with a vertical pressurizing container, the top end of the vertical pressurizing piston extends into the vertical pressurizing container and slides sealingly with the vertical pressurizing container, and the vertical pressurizing container injects silicone oil through the first silicone oil injection port to apply pressure to the vertical pressurizing piston.

[0012] Preferably, the horizontal pressurizing assembly includes a number of horizontal pressurizing pistons equidistantly arranged on the side walls of the simulation chamber body, the horizontal pressurizing pistons extend into the simulation chamber body and are transmission-connected to a horizontal pressure-bearing shaft, and the horizontal pressure-bearing shaft abuts against the side walls of the coal sample through a tile-shaped pressure applicator to perform horizontal pressurization.

[0013] Preferably, the side wall of the simulation chamber body is provided with a plurality of receiving grooves adapted to the tile-shaped pressure applicator, and the tile-shaped pressure applicator is embedded and accommodated in the receiving groove when no pressure is applied.

[0014] Preferably, the auxiliary component includes a plurality of temperature measuring holes arranged at the bottom end of the simulation chamber body, and temperature sensors are installed in the temperature measuring holes. The temperature sensors extend into the coal sample to measure the temperature of the coal sample.

[0015] Preferably, the auxiliary component includes an ignition device arranged at the bottom end of the simulation chamber body to complete the ignition process of the coal sample.

[0016] Preferably, the auxiliary component includes a synthesis gas extraction port and a plurality of gasification agent injection ports arranged at the bottom end of the simulation chamber body, and the synthesis gas extraction port and the gasification agent injection port are connected to the inner cavity of the simulation chamber body.

[0017] The present application also discloses a simulation method of a physical simulation device for underground coal gasification based on consideration of stress direction, comprising the following steps:

[0018] Cut out the coal sample and put it into the tested simulated bin;

[0019] Install the top cover of the simulation chamber to form a high temperature resistant simulation chamber, and test the air tightness of the high temperature resistant simulation chamber;

[0020] The coal sample is vertically and horizontally pressurized by a vertical pressurizing assembly and a horizontal pressurizing assembly;

[0021] Inject gasifier and combustion aid into the simulation chamber body through auxiliary components, observe the fluid state in the simulation chamber body, ignite and monitor the temperature after the pressure stabilizes;

[0022] Controlling the gasification process of the coal sample by controlling the temperature of the coal sample through auxiliary components, and monitoring the progress of the gasification process until the gasification process is completed;

[0023] After the gasification process is completed, melted wax oil is injected into the simulation chamber body through the auxiliary components, and the wax oil is waited for solidification;

[0024] After the wax oil solidifies, the stress is released through the horizontal pressure assembly and the vertical pressure assembly, and then the top cover of the simulation bin is removed, the coal sample and the wax model are taken out, and the wax model is subjected to CT scanning;

[0025] Clean and inspect the high temperature simulation chamber, and conduct simulation experiments with different stress fields and stress direction constraints after checking that everything is correct;

[0026] Organize and analyze experimental data to obtain experimental results.

[0027] Preferably, during the gasification process, the gasification progress is judged by real-time monitoring of the temperature array evolution characteristics of the temperature sensor. When the temperature of the measuring point of the temperature sensor near the synthesis gas extraction port or near the edge of the simulation chamber body reaches the set value, it is determined that the gasification process has reached the final stage, and the injection of gasifying agent is stopped, waiting for the gasification reaction to stop by itself.

[0028] Compared with the prior art, the present invention has the following advantages and technical effects: the present application discloses a physical simulation device and method for underground coal gasification taking stress direction into consideration, the high temperature resistant simulation chamber is fixed by a support frame to ensure the stability of the experimental process; the side wall of the simulation chamber body is provided with a horizontal pressurization assembly for horizontal pressurization, which is used to horizontally pressurize the coal sample, and the simulation chamber top cover at the top of the simulation chamber body is provided with a vertical pressurization assembly for vertically pressurizing the coal sample, and then combined with the horizontal pressurization assembly, the coal sample is subjected to triaxial loading, which can more realistically simulate the state of the coal sample under the formation, and controllably simulate underground coal gasification; the setting of the auxiliary assembly can control and monitor the gasification process of the coal sample, artificially control the gasification process of the coal sample, simulate the gasification process of the coal sample under different requirements, and obtain the specific parameters of the coal sample gasification process, so as to provide data support for the study of underground coal gasification.

[0029] The invention has a simple structure and can artificially simulate and control the gasification process of coal samples underground, explore the control factors and technologies of gasification furnace cavity expansion under real stress field conditions, and can provide physical experimental reference and basis for the application of underground coal gasification engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the overall structure of the simulation bin top cover of the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the simulation chamber body from a bottom view of the present invention;

[0034] Figure 4 This is a schematic diagram of the structure of the gas level piston pressurizing unit of the present invention;

[0035] In the figure: 1. support frame; 2. simulation chamber fixing rod; 3. simulation chamber fixing bolt; 4. rotating handle; 5. simulation chamber body; 6. simulation chamber top cover; 7. top cover handle; 8. sealing bolt; 9. first silicone oil injection port; 10. silicone oil; 11. sealing ring; 12. vertical pressurizing piston; 13. coal sample; 14. horizontal pressurizing piston; 15. second silicone oil injection port; 16. tile-shaped pressure applicator; 17. temperature sensor; 18. ignition device; 19. gasification agent injection port; 20. synthesis gas extraction port; 21. simulation chamber fixing threaded hole; 22. horizontal piston pressurizing device injection port switch; 23. thin layer copper snare; 24. high temperature resistant sealing ring; 25. vertical pressure applicator; 26. vertical pressure shaft; 27. horizontal pressure shaft. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The UCG gasifier mentioned in the background technology of the present application is a key equipment of underground coal gasification (UCG for short) technology.

[0039] UCG gasifier refers to the equipment that ignites underground coal in situ and converts the coal into combustible gas (such as hydrogen, coal gas, methane, etc.) through a series of combustion control methods and then extracts it to the ground.

[0040] During the gasification process, gasifying agents (such as oxygen, water vapor, etc.) are injected into the underground coal seam, reacting chemically with the coal seam to generate combustible gases. These gases are collected through the channels of the gasifier and transported to the surface.

[0041] There are many types of UCG gasifiers, including vertical well gasifiers, U-shaped well gasifiers, and parallel structure gasifiers, etc. Among them, the U-shaped well gasifier is more suitable for deep underground coal gasification.

[0042] The U-shaped well gasifier consists of an injection well and a production well. The injection well is drilled horizontally for a long distance, and the production well is a vertical well. The two are connected at the bottom of the well to form a gasification channel.

[0043] U-shaped gasifier construction technology: It is necessary to design a gasifier with a reasonable structure to achieve a stable and controllable gasification process. The main advantage of the U-shaped well gasifier is that the gasification channel has a large amount of coal coverage, which is conducive to the construction of multiple furnaces, has strong production sustainability, and has great industrialization potential.

[0044] Controlled Injection Point Retreat Gasification Process (CRIP): This process uses a U-shaped gasifier and injects gasifier from a horizontal well through a coiled tubing to achieve controlled combustion. When the coal at the first ignition point is burned out, the first combustion cavity is formed, and then the injection point is controlled by the coiled tubing to retreat a distance of a combustion cavity to reach the second gas injection combustion point, and then it is advanced step by step to the vertical section of the horizontal injection well.

[0045] Application: UCG gasifier plays a key role in underground coal gasification technology. This technology omits the complex underground excavation coal mining equipment, reduces the safety issues of coal miners working underground, and reduces the investment cost of the coal industry. At the same time, this technology also has environmental advantages, and the pollutants produced are far less than ground combustion.

[0046] Challenges: Although UCG gasifiers have many advantages, they still face some challenges. For example, the geological conditions of deep coal seams are more complex, making UCG projects more difficult to implement. In addition, key technologies such as gasifier construction and gasification combustion control require further research and testing.

[0047] Reference Figure 1-4 As shown, this embodiment provides a physical simulation device for underground coal gasification taking stress direction into consideration, including a support frame 1, on which a high temperature resistant simulation chamber is movably provided, and the high temperature resistant simulation chamber is used to perform a gasification simulation experiment on a coal sample 13;

[0048] The high temperature resistant simulation bin bag is movably mounted on a simulation bin body 5 on a support frame 1, a coal sample 13 is loaded in the simulation bin body 5, and a horizontal pressurizing component for pressurizing the coal sample 13 through a horizontal plate is arranged on the side wall of the simulation bin body 5;

[0049] The top of the simulation bin body 5 is sealed with a simulation bin cover 6, and the simulation bin cover 6 is provided with a vertical pressurizing component for vertically pressurizing the coal sample 13;

[0050] The bottom end of the simulation chamber body 5 is provided with a number of auxiliary components for assisting the simulation experiment.

[0051] The present application discloses a physical simulation device and method for underground coal gasification that takes stress direction into consideration. A high-temperature resistant simulation chamber is fixed by a support frame 1 to ensure the stability of the experimental process. A horizontal pressurizing component for horizontal pressurization is disposed on the side wall of the simulation chamber body 5 to perform horizontal pressurization on the coal sample 13, and a vertical pressurizing component is disposed on the simulation chamber top cover 6 at the top of the simulation chamber body 5 to perform vertical pressurization on the coal sample 13. Then, the coal sample 13 is subjected to triaxial loading in combination with the horizontal pressurizing component, which can more realistically simulate the state of the coal sample 13 under the formation and controllably simulate underground coal gasification. The setting of the auxiliary components can control and monitor the gasification process of the coal sample 13, artificially control the gasification process of the coal sample 13, simulate the gasification process of the coal sample 13 under different requirements, and obtain specific parameters of the gasification process of the coal sample 13, so as to provide data support for the study of underground coal gasification. The present invention has a simple structure, can artificially simulate and control the gasification process of coal sample 13 underground, explore the control factors and technologies of gasification furnace cavity expansion under real stress field conditions, and can provide physical experimental reference and basis for the application of underground coal gasification engineering.

[0052] In one embodiment of the present application, the simulation bin body 5 and the simulation bin top cover 6 are made of high temperature resistant stainless steel with a temperature resistance of not less than 1800°C; the simulation bin body 5 is a cylinder with a hollow interior as a coal seam bin for placing coal samples 13.

[0053] In one embodiment of the present application, the simulation bin body 5 has an outer diameter of 61 cm and a height of 50 cm; the hollow coal seam bin has a diameter of 50 cm and a height of 45 cm.

[0054] In one embodiment of the present application, simulation bin fixing rods 2 are respectively provided on both sides of the simulation bin body 5 , and the simulation bin fixing rods 2 are mounted on the support frame 1 through simulation bin fixing bolts 3 for easy fixation.

[0055] In one embodiment of the present application, rotating handles 4 are respectively provided at both ends of the simulation chamber fixing rod 2 for controlling the movement of the high temperature resistant simulation chamber and facilitating the lifting of the simulation chamber body 5 .

[0056] In one embodiment of the present application, a plurality of top cover handles 7 are provided on the outer side of the simulation bin top cover 6 to facilitate loading and unloading of the simulation bin top cover 6 .

[0057] In one embodiment of the present application, a plurality of simulation bin fixing threaded holes 21 arranged in a ring shape are provided on the simulation bin body 5 , and the simulation bin top cover 6 is locked and fixed to the simulation bin body 5 by a plurality of sealing bolts 8 .

[0058] In one embodiment of the present application, a sealing groove is provided between the simulation bin top cover 6 and the simulation bin body 5 for accommodating a high temperature resistant sealing ring 24, and the sealing ring 11 has a temperature resistance of not less than 1000°C.

[0059] In an embodiment of the present application, the number of the sealing bolts 8 is preferably twelve.

[0060] Further optimization scheme, the vertical pressurizing assembly includes a vertical pressurizing piston 12 movably arranged on the simulation bin top cover 6; the vertical pressurizing piston 12 extends into the simulation bin body 5 and vertically pressurizes the top of the coal sample 13 through the vertical pressure-bearing shaft 26; the simulation bin top cover 6 is provided with a vertical pressurizing container, the top of the vertical pressurizing piston 12 extends into the vertical pressurizing container and slides with the vertical pressurizing container in a sealed manner, and the vertical pressurizing container injects silicone oil 10 through the first silicone oil injection port 9 to pressurize the vertical pressurizing piston 12. In addition to its own rigid structure, the simulation bin top cover 6 is provided with a vertical pressurizing container at its center for applying vertical stress; when working, high-temperature resistant silicone oil 10 is pumped into the vertical pressurizing container through a constant speed and pressure pump and the first silicone oil injection port 9 arranged on the vertical pressurizing container, and the vertical pressurizing piston 12 is pushed by the silicone oil 10, and the vertical pressurizing piston 12 passes through the simulation bin top cover 6 and pressurizes the coal sample 13 through the vertical pressure-bearing shaft 26 to simulate different stress fields.

[0061] In one embodiment of the present application, the vertical pressure-bearing shaft 26 abuts against the vertical pressure applicator 25 on the coal sample 13 so that the top of the coal sample 13 is evenly stressed.

[0062] In one embodiment of the present application, the vertical pressure applicator 25 is adapted to the inner cavity of the simulation chamber body 5, and has a diameter of 50 cm and a thickness of 5 cm.

[0063] In one embodiment of the present application, a sealing ring 11 is provided between the vertical pressure container and the vertical pressure piston 12 to prevent leakage of the silicone oil 10 and ensure stable transmission of pressure.

[0064] A further optimized solution is that the horizontal pressurizing assembly includes a number of horizontal pressurizing pistons 14 movably arranged at equal intervals on the side wall of the simulation chamber body 5. The horizontal pressurizing pistons 14 extend into the simulation chamber body 5 and are transmission-connected to a horizontal pressure-bearing shaft 27. The horizontal pressure-bearing shaft 27 abuts against the side wall of the coal sample 13 through a tile-shaped pressure applicator 16 to perform horizontal pressurization. Twelve horizontal piston pressure vessels are arranged in the side wall of the simulation bin body 5 for horizontal pressure application; the centers of the horizontal piston pressure vessels are spaced 1 / 12 of the circumference in the side wall of the simulation bin body 5; when in operation, high temperature resistant silicone oil 10 is pumped into the horizontal pressure vessel through a constant speed and pressure pump and a second silicone oil injection port 15 arranged on the horizontal piston pressure vessel, and the horizontal pressure piston 14 is pushed by the silicone oil 10. The horizontal pressure piston 14 passes through the simulation bin body 5 and applies pressure to the coal sample 13 through the horizontal pressure-bearing shaft 27 to simulate different stress fields; 12 split tile-shaped pressure applicators 16 are arranged between the inner wall of the simulation bin body 5 and the coal sample 13, and the corresponding arc of a single tile-shaped pressure applicator 16 is 1 / 12 of the circumference; the center of the tile-shaped pressure applicator 16 is connected to the horizontal pressure-bearing shaft 27 in the corresponding orientation, and the bottom end of the tile-shaped pressure applicator 16 contacts the bottom of the simulation bin body 5, and high temperature resistant lubricating grease needs to be applied to the contact point between the two when in use.

[0065] In one embodiment of the present application, the tile-shaped pressure applicator 16 has a height of 44.95 cm and a thickness of 0.5 cm.

[0066] In one embodiment of the present application, the side wall of the simulation chamber body 5 is provided with a plurality of horizontal piston pressurizing device injection port switches 22 corresponding to the horizontal pressurizing pistons 14, which can control the horizontal pressurization at the corresponding positions.

[0067] In one embodiment of the present application, when the horizontal pressure piston 14 performs horizontal pressure application, two diagonally opposite ones are required to form a horizontal stress application group to avoid damaging the coal sample 13 .

[0068] In one embodiment of the present application, the magnitude and direction of the horizontal stress are controlled by controlling the pumping pressure of a constant pressure pump; the pumping pressure range of the constant speed constant pressure pump is 0-50MPa, and the control accuracy is ±0.01MPa.

[0069] As a further optimization scheme, the side wall of the simulation chamber body 5 is provided with a plurality of receiving grooves adapted to the tile-shaped pressure applicator 16. When no pressure is applied, the tile-shaped pressure applicator 16 is embedded in the receiving groove. The horizontal pressure bearing shaft 27 is connected to the horizontal pressure piston 14, and the whole is installed in the receiving groove embedded in the inner wall of the simulation chamber body 5, so as to avoid affecting the entry and exit of the coal sample 13 when no horizontal pressure is applied.

[0070] To further optimize the solution, the auxiliary components include a plurality of temperature measuring holes arranged at the bottom end of the simulation bin body 5, in which temperature sensors 17 are installed, and the temperature sensors 17 extend into the coal sample 13 to measure the temperature of the coal sample 13; the auxiliary components include an ignition device 18 arranged at the bottom end of the simulation bin body 5 to complete the ignition process of the coal sample 13; the auxiliary components include a synthesis gas extraction port 20 and a plurality of gasification agent injection ports 19 arranged at the bottom end of the simulation bin body 5, and the synthesis gas extraction port 20 and the gasification agent injection port 19 are connected to the inner cavity of the simulation bin body 5. The bottom of the simulation chamber body 5 is equipped with 20 temperature sensor mounting holes, 1 ignition device mounting port, 1 synthesis gas extraction port 20 and 5 gasification agent injection ports 19. The temperature sensor mounting hole is used to insert the temperature sensor 17 into the coal sample 13 so as to monitor the temperature of the coal sample 13 during the UCG process and judge the gasification process by the temperature evolution characteristics; the ignition device 18 is installed in the temperature sensor mounting hole to complete the ignition process of underground coal gasification; the gasification agent injection port 19 is used for the initial gasification agent and combustion-supporting agent injection and the subsequent gasification process control; the synthesis gas extraction port 20 is used for the extraction of synthesis gas and the subsequent gasification furnace cavity morphology fixed extraction.

[0071] In one embodiment of the present application, the temperature sensor 17 has a measurement range of 0-1500°C and an accuracy of ±0.1°C.

[0072] The present application also discloses a simulation method of a physical simulation device for underground coal gasification based on consideration of stress direction, comprising the following steps:

[0073] Cut out the coal sample 13, and put the coal sample 13 into the tested simulation chamber body 5;

[0074] Install the simulation chamber top cover 6 to form a high temperature resistant simulation chamber, and test the air tightness of the high temperature resistant simulation chamber;

[0075] The coal sample 13 is vertically pressurized and horizontally pressurized by using a vertical pressurizing assembly and a horizontal pressurizing assembly;

[0076] Inject gasifying agent and combustion-supporting agent into the simulation chamber body 5 through auxiliary components, observe the fluid state in the simulation chamber body 5, ignite and monitor the temperature after the pressure stabilizes;

[0077] controlling the temperature of the coal sample 13 through the auxiliary component to control the gasification process of the coal sample 13, and monitoring the progress of the gasification process until the gasification process is completed;

[0078] After the gasification process is completed, melted wax oil is injected into the simulation chamber body 5 through the auxiliary component, and the wax oil is waited for solidification;

[0079] After the wax oil solidifies, the stress is released through the horizontal pressurizing assembly and the vertical pressurizing assembly, and then the simulation bin top cover 6 is removed, the coal sample 13 and the wax mold are taken out, and the wax mold is subjected to CT scanning;

[0080] Clean and inspect the high temperature simulation chamber, and conduct simulation experiments with different stress fields and stress direction constraints after checking that everything is correct;

[0081] Organize and analyze experimental data to obtain experimental results.

[0082] The detailed experimental process is as follows:

[0083] Step 1: Select raw coal with complete coal structure and less cracks, use wire cutting instrument to prepare columnar samples with a diameter of 50 cm and a height of 45 cm vertically along the bedding, and grind them to be smooth to form coal sample 13;

[0084] Step 2: Wrap the coal sample 13 with a thin copper snare 23 with a thickness of 0.5 mm, and place the coal sample 13 in the coal seam bin with the help of an external lifting device;

[0085] Step 3: Install the vertical pressurizing assembly and the simulation bin top cover 6 in sequence, and connect and fix the simulation bin top cover 6 and the simulation bin body 5 by fixing bolts;

[0086] Step 4: Inject nitrogen into the simulation chamber body 5 and perform an airtightness check;

[0087] Step 5: After the air tightness check is completed, connect the vacuum pump to extract the gas in the simulation chamber;

[0088] Step 6: According to the experimental design, use a constant speed and constant pressure pump to pump high temperature resistant silicone oil 10 into the vertical pressure container and the horizontal pressure container at the same time, and control the vertical stress and horizontal stress by setting the target pressure of the constant speed and constant pressure pump; Note: When the horizontal stress is loaded, the target pressure of the constant speed and constant pressure pump should be set to the minimum horizontal principal stress. When the vertical stress and the horizontal stress are fully loaded, close the piston injection port valve and wait for the stress to stabilize; then, according to the maximum horizontal principal stress and direction of the experimental design, open the injection port valve of the horizontal piston pressurizing unit group (the two piston pressurizing units corresponding to the diagonal line are a group) that needs to continue to load stress, set the constant speed and constant pressure pump pressure to inject high temperature resistant silicone oil 10 into it to increase the stress in this direction;

[0089] Step 7: After stress loading is completed, the gasifier and combustion aid are injected into the high temperature simulation chamber through the external gasifier injection device, and the fluid pressure in the high temperature simulation chamber is observed through the pressure gauge. After the pressure is stable, ignition and temperature monitoring preparation are carried out;

[0090] Step 8: Ignite through the ignition port by using the external ignition device 18, and determine whether the ignition is successful by monitoring the temperature array characteristics;

[0091] Step 9: After ignition is completed, the coal gasification process is controlled through different gasification agent injection ports 19, and the synthesis gas is collected through the synthesis gas extraction port 20; during the experiment, the temperature array evolution characteristics are monitored in real time to determine the gasification process. When the temperature of the temperature measurement point near the synthesis gas extraction port 20 or near the edge of the high-temperature simulation chamber reaches 1000°C, it is determined that the gasification process has reached the final stage, and the injection of gasification agent is stopped until the gasification reaction stops automatically. If the gasification reaction does not end after a period of time, nitrogen should be injected to manually stop the gasification process;

[0092] Step 10: After the gasification process stops, wait for the high temperature simulation chamber and the coal sample 13 to cool to room temperature, then inject melted wax oil into the high temperature simulation chamber through the synthesis gas extraction port 20 with the help of an external wax oil injection device to extract the morphological characteristics of the gasification furnace chamber, and wait for the wax oil to solidify after the injection is completed;

[0093] Step 11: After the wax oil is completely solidified, the applied vertical and horizontal stresses are released, and after the stress release is completed, the high temperature simulation chamber is opened to take out the coal sample 13, and at the same time, the orientation of the solidified furnace cavity wax model is marked, and the morphological characteristics of the wax model are quantitatively characterized using a CT scanning device;

[0094] Step 12: Clean and check the experimental device. After checking, design different stress fields and stress direction constraints according to the experimental plan, and repeat steps 1 to 12;

[0095] Step 13: Organize, process and analyze the experimental data to explore the furnace chamber expansion law and its control mechanism during underground coal gasification under different stress fields and stress direction constraints.

[0096] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0097] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A physical simulation device for underground coal gasification taking stress direction into consideration, characterized in that: It comprises a support frame (1), on which a high temperature resistant simulation chamber is movably arranged, and the high temperature resistant simulation chamber is used to perform a gasification simulation experiment on a coal sample (13); The high temperature resistant simulation bin bag is movably mounted on a simulation bin body (5) on the support frame (1), the coal sample (13) is loaded in the simulation bin body (5), and the side wall of the simulation bin body (5) is provided with a horizontal pressurizing component for pressurizing the coal sample (13) through a horizontal plate; The top of the simulation bin body (5) is sealed with a simulation bin top cover (6), and the simulation bin top cover (6) is provided with a vertical pressurizing component for vertically pressurizing the coal sample (13); The bottom end of the simulation chamber body (5) is provided with a plurality of auxiliary components for assisting the simulation experiment.

2. The underground coal gasification physical simulation device considering stress direction according to claim 1, characterized in that: The vertical pressurizing assembly comprises a vertical pressurizing piston (12) movably arranged on the simulation bin top cover (6); the vertical pressurizing piston (12) extends into the simulation bin body (5) and vertically pressurizes the top of the coal sample (13) through a vertical pressure bearing shaft (26).

3. The underground coal gasification physical simulation device considering stress direction according to claim 2, characterized in that: The simulation bin top cover (6) is provided with a vertical pressurizing container, the top end of the vertical pressurizing piston (12) extends into the vertical pressurizing container and slides in a sealed manner with the vertical pressurizing container, and the vertical pressurizing container injects silicone oil (10) through the first silicone oil injection port (9) to apply pressure to the vertical pressurizing piston (12).

4. The underground coal gasification physical simulation device considering stress direction according to claim 1, characterized in that: The horizontal pressurizing assembly comprises a plurality of horizontal pressurizing pistons (14) movably arranged at equal intervals on the side wall of the simulation chamber body (5); the horizontal pressurizing pistons (14) extend into the simulation chamber body (5) and are transmission-connected to a horizontal pressure-bearing shaft (27); the horizontal pressure-bearing shaft (27) abuts against the side wall of the coal sample (13) through a tile-shaped pressure applicator (16) to perform horizontal pressurization.

5. The physical simulation device for underground coal gasification considering stress direction according to claim 4 is characterized in that: The side wall of the simulation chamber body (5) is provided with a plurality of receiving grooves adapted to the tile-shaped pressure applicator (16). When no pressure is applied, the tile-shaped pressure applicator (16) is embedded and stored in the receiving groove.

6. The underground coal gasification physical simulation device considering stress direction according to claim 1, characterized in that: The auxiliary component comprises a plurality of temperature measuring holes arranged at the bottom end of the simulation chamber body (5), wherein a temperature sensor (17) is installed in the temperature measuring hole, and the temperature sensor (17) extends into the coal sample (13) to measure the temperature of the coal sample (13).

7. The underground coal gasification physical simulation device considering stress direction according to claim 1, characterized in that: The auxiliary component comprises an ignition device (18) arranged at the bottom end of the simulation chamber body (5) to complete the ignition process of the coal sample (13).

8. The underground coal gasification physical simulation device considering stress direction according to claim 1, characterized in that: The auxiliary component comprises a synthesis gas extraction port (20) and a plurality of gasification agent injection ports (19) arranged at the bottom end of the simulation chamber body (5); the synthesis gas extraction port (20) and the gasification agent injection port (19) are connected to the inner cavity of the simulation chamber body (5).

9. A method for physics simulation of underground coal gasification taking into account stress direction, based on the device for physics simulation of underground coal gasification taking into account stress direction as claimed in any one of claims 1 to 8, characterized in that The following steps are involved: Cut out a coal sample (13), and place the coal sample (13) into the tested simulation chamber body (5); The simulation chamber top cover (6) is installed to form a high temperature resistant simulation chamber, and the air tightness of the high temperature resistant simulation chamber is tested; The coal sample (13) is vertically pressurized and horizontally pressurized by using a vertical pressurizing assembly and a horizontal pressurizing assembly; Injecting a gasifying agent and a combustion-supporting agent into the simulation chamber body (5) through the auxiliary components, observing the state of the fluid in the simulation chamber body (5), and igniting and monitoring the temperature after the pressure is stabilized; Controlling the temperature of the coal sample (13) through the auxiliary component to control the gasification process of the coal sample (13), and monitoring the progress of the gasification process until the gasification process is completed; After the gasification process is completed, melted wax oil is injected into the simulation chamber body (5) through the auxiliary component, and the wax oil is waited for solidification; After the wax oil solidifies, the stress is released by the horizontal pressure assembly and the vertical pressure assembly, and then the simulation bin top cover (6) is removed, the coal sample (13) and the wax mold are taken out, and the wax mold is subjected to CT scanning; Clean and inspect the high temperature simulation chamber, and conduct simulation experiments with different stress fields and stress direction constraints after checking that everything is correct; Organize and analyze experimental data to obtain experimental results.

10. The physical simulation method for underground coal gasification considering stress direction according to claim 9, characterized in that: During the gasification process, the gasification progress is judged by real-time monitoring of the temperature array evolution characteristics of the temperature sensor (17). When the temperature of the temperature measuring point of the temperature sensor (17) near the synthesis gas extraction port (20) or near the edge of the simulation chamber body (5) reaches the set value, it is determined that the gasification process has reached the final stage, and the injection of the gasifying agent is stopped, waiting for the gasification reaction to stop by itself.

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