Experimental device for migration law of underground coal gasification synthesis gas on overlying strata

Abstract

The utility model relates to the technical field of underground coal gasification, in particular to an experimental device for the migration law of underground coal gasification synthesis gas on overlying strata, which comprises a furnace body, a furnace cover and refractory bricks, the furnace cover is arranged at the top of the furnace body, the refractory bricks are arranged in the furnace body, a coal layer is arranged in the furnace body, and an overlying strata simulation device is arranged in the furnace body. A gasifying agent pipeline is arranged on one side of the furnace body, an air compressor is arranged at the inlet end of the gasifying agent pipeline, an oxygen bottle is arranged at the inlet end of the gasifying agent pipeline, a water supply pump is arranged at the inlet end of the gasifying agent pipeline, and a water tank is arranged at the input end of the water supply pump; the experimental device can simulate an air gasification mode, an oxygen-enriched gasification mode and a pure oxygen gasification mode, can simulate migration and diffusion of synthesis gas in the overlying strata of a roof under different conditions, and can effectively research migration and diffusion rules of airborne pollutants in the overlying strata; and a theoretical basis is provided for site selection of the gasification furnace, operation of the gasification furnace and prevention and control of gasification pollutants.

Description

Technical Field

[0001] This utility model relates to the field of underground coal gasification technology, and in particular to an experimental device for the migration law of syngas from underground coal gasification in overlying rocks. Background Technology

[0002] Underground coal gasification (ISC) is the process of directly converting coal into product gas through combustion and gasification reactions in underground coal seams in the presence of an oxidant. This product gas, commonly referred to as syngas, can then be used as feedstock for various applications, including fuel production, chemical production, and power generation. This underground coal gasification technology is applicable to most coal deposits. Given increasingly stringent environmental requirements for the mining industry and considering the associated labor and infrastructure costs, this technology is undoubtedly attractive. Surface drilling directly into the coal seam provides an effective channel for oxidant injection and product gas production. A pair of wells connected underground or extending horizontally constitute a substantially horizontal drilling channel; this channel facilitates oxidant injection and joie zone growth. And product gas transportation; one well used for oxidant injection is called an "injection well", and another well used for producing product gas is called a "product well"; both directional horizontal and vertical wells can serve as injection wells or product wells; underground coal gasification may require one or more vertical wells between injection wells and product wells; current research on the diffusion and migration patterns of gaseous pollutants generated by underground gasification still has many problems, and analysis can only be conducted through indirect methods such as borehole sampling and groundwater sampling. It is impossible to have a relatively intuitive understanding of the diffusion and migration patterns of pollutants generated by gasification under the porous media of the overburden. There is a lack of theoretical support for issues such as underground gasifier site selection, prevention and control of gasification-generated pollutants, and groundwater protection.

[0003] Current research on pollutants generated by gasification mainly focuses on the qualitative and quantitative analysis of the types of pollutants produced, the pathways by which gasification causes groundwater pollution, and studies on the degree of pollution after gasification through drilling technology and groundwater sampling analysis. However, current technical solutions have limited research on the migration and diffusion patterns of gaseous pollutants in the porous media of the overburden. Most studies rely on numerical simulations using software, which do not provide a clear understanding of the diffusion and migration patterns of gaseous pollutants. CN112943225A discloses an experimental device and method for simulating the migration patterns of coal gasification pyrolysis gas within the overburden. This device detects the migration patterns of coal pyrolysis gas within the overburden. This pyrolysis gas is produced by the pyrolysis of coal in an oxygen-free environment, which differs significantly from the syngas produced by the combustion and gasification reaction of coal with oxygen and water in actual underground coal gasification. Therefore, it cannot accurately reflect the migration patterns of syngas pollutants from underground coal gasification within the overburden.

[0004] Therefore, to address the above-mentioned problems, an experimental device for studying the migration patterns of syngas produced in underground coal gasification within overlying strata is proposed. This device simulates real underground coal gasification and uses air / oxygen-enriched / pure oxygen gas and water as gasifying agents. By adjusting the ratio and flow rate of the gasifying agents, the temperature inside the gasifier can be controlled. This device can realistically simulate various conditions of underground coal gasification and obtain the migration patterns of various components of syngas produced under different conditions within the overlying strata. Utility Model Content

[0005] In order to overcome the problem that in the daily operation of existing experimental devices for the migration of syngas from underground coal gasification in overburden, it is difficult to have a relatively intuitive understanding of the diffusion and migration patterns of pollutants generated during gasification in the porous media of the roof overburden, and the devices cannot truly reflect the migration patterns of syngas pollutants in underground coal gasification within the overburden.

[0006] The technical solution of this utility model is as follows: an experimental device for studying the migration law of syngas from underground coal gasification in overburden, comprising a furnace body, a furnace cover, and refractory bricks. The furnace cover is installed on the top of the furnace body, and refractory bricks are installed inside the furnace body, covering the interior of the furnace body. A coal seam is located inside the furnace body, and an overburden simulation device is installed inside the furnace body, positioned above the coal seam. A gasifying agent pipeline is installed on one side of the furnace body, penetrating the side end cover and extending to the bottom of the coal seam. The outlet end of the gasifying agent pipeline is connected to a horizontally positioned coal seam shaft. An air compressor, an oxygen cylinder, and a water pump are installed at the inlet end of the gasifying agent pipeline. The furnace is connected to an air compressor, oxygen cylinder, and water pump via pipes. A water tank is installed at the input end of the water pump, and the water tank and water pump are connected via pipes. A product well is installed inside the furnace body. The outlet end of the product well passes through the furnace cover, the overburden simulation device, and connects to the coal seam. Thermocouples are installed on the side wall of the furnace body. Multiple sets of thermocouples are installed and inserted horizontally into the side wall of the furnace body. The detection ends of the thermocouples are distributed at different depths in the coal seam well. A safety valve is installed outside the gasifying agent pipeline. A spray box is installed at the top of the furnace body. There are three sets of spray boxes. The spray box is connected to the inside of the furnace body via a bottom valve. An ignition device is installed inside the furnace body. The ignition end of the ignition device is located near the outlet end of the gasifying agent pipeline.

[0007] Preferably, the process involves adjusting the water pump, oxygen cylinder, air compressor, nitrogen cylinder, and safety valve to the ready-to-operate state, opening the oxygen cylinder outlet valve, starting the air compressor, and turning the water pump to the preset flow rate. After the gasifying agent enters the furnace, the ignition device is activated to ignite the gasifier. After successful ignition, the bottom outlet valves of the three spray boxes are opened to inject water under the rock to simulate groundwater. Once gasification and combustion are normal, the gasifier temperature, measured by thermocouples, is adjusted by regulating the gasifying agent flow rate and ratio. After reaching the designed experimental time, the simulated overburden mold is removed, and the similar overburden simulation material is completely extracted for stratified sampling. The obtained samples are then subjected to analytical experiments such as FTIR and differential absorption spectroscopy as needed to study airborne pollutants (SO2, NO). x The migration and diffusion patterns of CO, volatile organic compounds, polycyclic aromatic hydrocarbons, etc. in the top plate.

[0008] Preferably, the gasifying agent pipeline has a three-layer coaxial sleeve structure, including a central pipe, an intermediate annular gap and an outer annular gap. The central pipe and the outer annular gap are respectively connected to an air compressor and an oxygen cylinder, and the intermediate annular gap is connected to a water supply pump. The gas outlet ends of the central pipe and the outer annular gap form an atomization structure, and the water in the intermediate annular gap is sprayed into the coal seam well after atomization.

[0009] Preferably, the overburden simulation device includes a detachable simulated overburden mold, which is filled with a similar simulated material consisting of a mixture of 10-mesh to 250-mesh sand and gypsum. The standard dimensions of the simulated overburden mold are 1000mm in length, 400mm in width, and 150mm in height, and it is formed into a porous media structure through layered pressing.

[0010] Preferably, multiple sets of thermocouples are horizontally inserted along the side wall of the furnace and extend to different depths in the coal seam well. The arrangement direction of the thermocouples is parallel to the extension direction of the coal seam well, and the temperature distribution of the gasifier is monitored in real time by an external temperature control device.

[0011] Preferably, there are three sets of spray boxes, which are evenly distributed on the top of the furnace cover. The outlet of the spray box is connected to the inside of the furnace body through an independent valve to simulate the process of groundwater infiltration.

[0012] As a preferred option, refractory bricks are used to cover the inner wall of the furnace body and the inner wall of the furnace cover, forming a heat-insulating cavity between the refractory bricks and the furnace body. The thickness of the refractory bricks is 50-100mm, and the material is alumina refractory material.

[0013] Preferably, the product well is a vertical pipe structure, with its bottom end connected to the coal seam well and its top end penetrating the furnace cover. The outlet end of the product well is equipped with a gas sampling port for collecting syngas and detecting its composition.

[0014] The beneficial effects of this utility model are:

[0015] By adjusting the water pump, oxygen cylinder, air compressor, nitrogen cylinder, and safety valve to the ready-to-operate state, opening the oxygen cylinder outlet valve, starting the air compressor, and turning the water pump to the preset flow rate, the gasification furnace is ignited after the gasifying agent enters the furnace body. After successful ignition, the bottom outlet valves of the three spray boxes are opened to inject water under the rock to simulate groundwater. After normal gasification and combustion, the gasification furnace temperature, measured by thermocouples, is adjusted by regulating the gasifying agent flow rate and ratio. After reaching the designed experimental time, the simulated overburden mold is removed, and the similar overburden simulation material is completely extracted for stratified sampling. The obtained samples are then analyzed according to experimental needs, such as by FTIR and differential absorption spectroscopy, to study airborne pollutants (SO2, NO). x The study investigates the migration and diffusion patterns of syngas (such as CO, volatile organic compounds, and polycyclic aromatic hydrocarbons) in the roof, thereby simulating real underground coal gasification. It utilizes air / oxygen-enriched / pure oxygen gas and water as gasifying agents, and controls the temperature inside the gasifier by adjusting the ratio and flow rate of the gasifying agents. This allows for a realistic simulation of various conditions in underground coal gasification, revealing the migration patterns of various components of syngas produced under different conditions within the overlying strata. Attached Figure Description

[0016] Figure 1 The diagram shows a three-dimensional structure of the experimental apparatus for the migration of syngas from underground coal gasification in overlying rocks according to this utility model.

[0017] Figure 2 The diagram shown is a three-dimensional cross-sectional view of the experimental apparatus for the migration of syngas from underground coal gasification in overlying rocks according to this utility model.

[0018] Figure 3 The diagram shows a partial cross-sectional view of the experimental apparatus for the migration of syngas from underground coal gasification in overlying rocks according to this utility model.

[0019] Figure 4 The diagram shows a plan view of the experimental apparatus for the migration of syngas from underground coal gasification in overlying rocks according to this utility model.

[0020] Figure 5 The diagram shows a cross-sectional view of the gasifying agent pipeline in the experimental apparatus for studying the migration law of syngas from underground coal gasification in overburden.

[0021] Explanation of reference numerals in the attached drawings: 1. Furnace body; 2. Furnace cover; 3. Air compressor; 4. Oxygen cylinder; 5. Nitrogen cylinder; 6. Water tank; 7. Water supply pump; 8. Gasifying agent pipeline; 9. Side end cap; 10. Safety valve; 11. Ignition device; 12. Product well; 13. Thermocouple; 14. Coal seam; 15. Overburden simulation device; 16. Spray box; 17. Refractory brick. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Please see Figure 1 , Figure 2 and Figure 3 This utility model provides an experimental device for studying the migration law of syngas from underground coal gasification in overburden, comprising a furnace body 1, a furnace cover 2, and refractory bricks 17. The furnace cover 2 is provided on the top of the furnace body 1, and the refractory bricks 17 are arranged inside the furnace body 1, covering the interior of the furnace body 1. A coal seam 14 is arranged inside the furnace body 1, and an overburden simulation device 15 is arranged inside the furnace body 1, located above the coal seam 14. A gasifying agent pipe 8 is arranged on one side of the furnace body 1, passing through a side end cap 9 and extending to the bottom of the coal seam 14. The outlet end of the gasifying agent pipe 8 is connected to a horizontally arranged well of the coal seam 14. An air compressor 3 is arranged at the inlet end of the gasifying agent pipe 8, an oxygen cylinder 4 is arranged at the inlet end of the gasifying agent pipe 8, and a water pump 7 is arranged at the inlet end of the gasifying agent pipe 8. The air compressor 3, oxygen cylinder 4, and water pump 7 are connected by pipes. The input end of the water pump 7 is equipped with a water tank 6. The water tank 6 and the water pump 7 are connected by pipes. A product well 12 is set inside the furnace body 1. The outlet end of the product well 12 passes through the furnace cover 2 and the overburden simulation device 15 and is connected to the coal seam 14. Thermocouples 13 are set on the side wall of the furnace body 1. There are multiple sets of thermocouples 13. The multiple sets of thermocouples 13 are inserted into the side wall of the furnace body 1 in a horizontal direction. The detection ends of the thermocouples 13 are distributed at different depths in the coal seam 14 well. A safety valve 10 is set outside the gasifying agent pipe 8. A spray box 16 is set on the top of the furnace body 1. There are three sets of spray boxes 16. The spray box 16 is connected to the inside of the furnace body 1 through a bottom valve. An ignition device 11 is set inside the furnace body 1. The ignition end of the ignition device 11 is set near the outlet end of the gasifying agent pipe 8.

[0024] Please see Figure 4 and Figure 5In this embodiment, the gasifying agent pipeline 8 is a three-layer coaxial sleeve structure, including a central pipe, an intermediate annular gap, and an outer annular gap. The central pipe and the outer annular gap are respectively connected to the air compressor 3 and the oxygen cylinder 4. The intermediate annular gap is connected to the water supply pump 7. The gas outlet ends of the central pipe and the outer annular gap form an atomization structure. The water in the intermediate annular gap is atomized and sprayed into the coal seam 14 wellbore. During use, the air compressor 3 and the oxygen cylinder 4 can supply the air, oxygen-enriched gas, or pure oxygen gas required for gasification. The nitrogen cylinder 5 supplies nitrogen for airtightness testing and purging the system during shutdown. The water supply pump 7... Water tank 6 is used to store the water needed for gasification. Gasifying agent pipeline 8 is an injection well simulating underground coal gasification. The pipeline has three layers from the inside out: the innermost central pipe carries air, oxygen-enriched gas, or pure oxygen gas; the outermost annular layer carries water; and the outermost annular layer carries air, oxygen-enriched gas, or pure oxygen gas. This allows the gas from the central pipe and the outermost layer to atomize the water in the middle annular layer at the outlet of gasifying agent pipeline 8, resulting in a more uniform water distribution at the outlet area, which is beneficial for the coal gasification reaction. Gasifying agent pipeline 8 is constructed using a belt-type... The flange is connected and sealed to the side end cover 9 of the furnace body 1. The overburden simulation device 15 includes a detachable simulated overburden mold. The mold is filled with a similar simulated material consisting of a mixture of 10-mesh to 250-mesh sand and gypsum. The standard dimensions of the simulated overburden mold are 1000mm in length, 400mm in width, and 150mm in height. It is formed into a porous medium structure through layered pressing. Multiple sets of thermocouples 13 are horizontally inserted along the side wall of the furnace body 1 and extend to different depths in the coal seam 14 shaft. The arrangement direction of the thermocouples 13 is parallel to the extension direction of the coal seam 14 shaft. The temperature distribution of the gasifier is monitored in real time by an external temperature control device. During use, thermocouple 13 can measure whether the ignition device 11 is successfully ignited, measure the temperature distribution of the gasifier during normal experiments, and measure the growth of the gasification combustion zone. It can also control the water and gas intake according to the temperature to achieve the purpose of controlling the gasifier temperature. The ignition device 11 is used for igniting the gasifier, and the safety valve 10 is used for safety protection. When the pressure inside the gasifier exceeds a certain range during the gasification combustion process, it will automatically lift up to release pressure, effectively protecting the gasifier and the safety of the operators.

[0025] There are three sets of spray boxes 16, which are evenly distributed on the top of the furnace cover 2. The water outlet of the spray box 16 is connected to the inside of the furnace body 1 through an independent valve to simulate the process of groundwater infiltration. In use, the spray box 16 injects water under the rock to simulate the process of groundwater entering the combustion zone through the rock strata during underground coal gasification. The water supply can be used to measure the change in gasifier pressure and the impact on syngas diffusion. During operation, the pressure of the gasifier is slightly greater than the static water pressure of the combustion zone. Refractory bricks 17 cover the inner wall of the furnace body 1 and the inner wall of the furnace cover 2, forming a heat insulation cavity between the refractory bricks 17 and the furnace body 1. The thickness of the refractory bricks 17 is 50-100mm, and the material is alumina refractory material.

[0026] As a preferred embodiment, the product well 12 is a vertical pipe structure. The bottom end of the product well 12 is connected to the coal seam 14 well passage, and the top end penetrates the furnace cover 2. The outlet end of the product well 12 is equipped with a gas sampling port for collecting syngas and detecting the migration parameters of gaseous pollutants. In use, the product well 12 is the channel through which the syngas produced after gasification leaves the coal seam 14.

[0027] When carrying out the work, firstly, based on the experimental conditions and the geological characteristics to be simulated, determine the size and proportion of the similar simulation material to be prepared, and select the size of the simulated overburden mold of the overburden simulation device 15 as needed. The standard simulated overburden mold of this device can be used to prepare a cuboid similar simulation material of overburden with a length of 1000mm, a width of 400mm, and a height of 150mm. Load the coal to be tested into the furnace body 1, filling it to a height of about 500mm, and at the same time, forcefully compact the coal.

[0028] After preparing the coal sample, the simulated overburden mold in the overburden simulation device 15 is removed. According to experimental requirements, a similar overburden simulation material is pressed. This material is made by mixing 10-250 mesh sand with gypsum. After drying and solidification, the simulated overburden mold containing the material is placed on top of the coal inside the furnace body 1. A hole is drilled through the side end cap 9 of the furnace body 1 to open the connection channel between the injection well and the product well 12 in the horizontal section. After successful opening, the gasifying agent pipe 8 is inserted into this channel to the ignition position. Then, the flanged gasifying agent pipe 8 is connected and sealed to the side end cap 9 of the furnace body 1 using a flange. The product well 12 is then drilled, and the pipe in the product well 12 is inserted into the opened product well. At well 12, insert the thermocouple into the horizontal airflow channel from the top. Drill dozens of thermocouple holes 13 from the side of the furnace body 1 at the set positions using an electric drill. These holes extend from the side edge to different depths in the gasifier. Then insert the thermocouples 13. Similarly, drill a hole on the side of the horizontal airflow channel of the gasifier near the product well 12. Then insert the ignition device 11 and extend it to the vicinity of the outlet of the gasifying agent pipe 8 in the gasifier for ignition. Connect and install the refractory bricks 17 to the furnace body 1 and the furnace cover 2. Place the furnace cover 2 on the furnace body 1 and tighten it with flange bolts and nuts. Install three spray boxes 16, fill the spray boxes 16 with water, close the bottom valve of the spray box 16, and open the valve when needed.

[0029] After the pipe connections and flange connections between the equipment are installed, an air tightness test is conducted. First, open and close the corresponding valves to purge nitrogen gas. After purging for a period of time, close the valves and observe the pressure change. If the air tightness is good, proceed with the next test. If the air tightness is poor, seal the leak by applying soapy water. Then, conduct another air tightness test. Only after passing the test can the experiment continue. Adjust the water pump, oxygen cylinder 4, air compressor 3, nitrogen cylinder 5, and safety valve 10 to the ready-to-run state. Open the outlet valve of oxygen cylinder 4, start the air compressor 3, and turn on the water pump to the preset flow rate. After the gasifying agent enters the furnace body 1, start the ignition device 11 to ignite the gasifier. After successful ignition, open the bottom outlet valves of the three spray boxes 16 to inject water under the rock to simulate groundwater. After the gasification and combustion are normal, adjust the gasifier flow rate and ratio to adjust the gasifier temperature measured by thermocouple 13.

[0030] After the designed experimental time is reached, the simulated overburden mold is removed, the similar simulated overburden material is completely taken out, and layered sampling is carried out. The obtained samples are then subjected to analytical experiments such as FTIR and differential absorption spectroscopy as needed to study the migration and diffusion laws of airborne pollutants in the roof.

[0031] Through the above steps, the water pump, oxygen cylinder 4, air compressor 3, nitrogen cylinder 5, and safety valve 10 are adjusted to the ready-to-operate state. The outlet valve of oxygen cylinder 4 is opened, air compressor 3 is started, and the water pump is turned on to the preset flow rate. After the gasifying agent enters the furnace body 1, the ignition device 11 is started to ignite the gasifier. After successful ignition, the bottom outlet valves of the three spray boxes 16 are opened to inject water under the rock to simulate groundwater. After normal gasification and combustion, the gasifier temperature measured by thermocouple 13 is adjusted by regulating the gasifying agent flow rate and ratio. After the designed experimental time is reached, the simulated surface is covered... The rock mold is removed, and the overburden-like simulation material is completely taken out for stratified sampling. The obtained samples are then subjected to analytical experiments such as FTIR and differential absorption spectroscopy as needed to study the migration and diffusion laws of gaseous pollutants in the roof, thereby simulating real underground coal gasification. Air / oxygen-enriched / pure oxygen gas and water can be used as gasifying agents. The temperature inside the gasifier can be controlled by adjusting the ratio and flow rate of the gasifying agents. Various conditions of underground coal gasification can be realistically simulated to obtain the migration laws of various components of syngas produced under different conditions in the overburden.

[0032] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. An experimental device for studying the migration law of coal underground gasification synthetic gas in overburden rock, comprising a furnace body (1), a furnace cover (2) and firebricks (17); characterized in that: The furnace body (1) is provided with a furnace cover (2) at the top, and the inside of the furnace body (1) is provided with refractory bricks (17) which are covered in the inside of the furnace body (1), and the inside of the furnace body (1) is provided with a coal seam (14), and the inside of the furnace body (1) is provided with an overburden simulation device (15) which is located above the coal seam (14), and one side of the furnace body (1) is provided with a gasification agent pipeline (8) which penetrates through the side end cover (9) and extends to the bottom of the coal seam (14), and the outlet end of the gasification agent pipeline (8) is communicated with the horizontal coal seam (14) shaft, and the inlet end of the gasification agent pipeline (8) is provided with an air compressor (3), and the inlet end of the gasification agent pipeline (8) is provided with an oxygen cylinder (4), and the inlet end of the gasification agent pipeline (8) is provided with a water supply pump (7), and the inlet end of the gasification agent pipeline (8) is connected with the air compressor (3), the oxygen cylinder (4) and the water supply pump (7) through pipelines respectively, and the input end of the water supply pump (7) is provided with a water tank (6), and the water tank (6) and the water supply pump (7) are connected through a pipeline, and the inside of the furnace body (1) is provided with a product shaft (12), and the outlet end of the product shaft (12) penetrates through the furnace cover (2), the overburden simulation device (15) and is communicated with the coal seam (14), and the side wall of the furnace body (1) is provided with a thermocouple (13), and the thermocouple (13) is provided with multiple groups, and the multiple thermocouples (13) are inserted into the side wall of the furnace body (1) along the horizontal direction, and the detection end of the thermocouple (13) is distributed at different depth positions of the coal seam (14) shaft, and the outside of the gasification agent pipeline (8) is provided with a safety valve (10), and the top of the furnace body (1) is provided with a spraying tank (16), and the spraying tank (16) is provided with three groups, and the spraying tank (16) is communicated with the inside of the furnace body (1) through the bottom valve, and the inside of the furnace body (1) is provided with an ignition device (11), and the ignition end of the ignition device (11) is arranged close to the outlet end of the gasification agent pipeline (8).

2. The experimental device for studying the migration law of coal underground gasification synthetic gas in overburden rock according to claim 1, characterized in that: The gasification agent pipeline (8) is a three-layer coaxial sleeve structure, including a center pipe, an intermediate annular gap and an outer annular gap, the center pipe and the outer annular gap are respectively communicated with the air compressor (3) and the oxygen cylinder (4), the intermediate annular gap is communicated with the water supply pump (7), the gas outlet ends of the center pipe and the outer annular gap form an atomization structure, and the water in the intermediate annular gap is sprayed into the coal seam (14) shaft after atomization.

3. The experimental device for studying the migration law of coal underground gasification synthetic gas in overburden rock according to claim 1, characterized in that: The overburden simulation device (15) includes a detachable simulation overburden mold, the mold is filled with similar simulation material mixed by 10-250 mesh sand particles and plaster, the standard size of the simulation overburden mold is 1000mm long, 400mm wide and 150mm high, and the mold forms a porous medium structure by layering and pressing.

4. The experimental device for studying the migration law of coal underground gasification synthetic gas in overburden rock according to claim 1, characterized in that: The multiple thermocouples (13) are inserted into the side wall of the furnace body (1) along the horizontal direction and extend to different depths of the coal seam (14) shaft, the arrangement direction of the thermocouples (13) is parallel to the extension direction of the coal seam (14) shaft, and the temperature distribution of the gasification furnace is monitored in real time by an external temperature control device.

5. The experimental device for studying the migration law of coal underground gasification synthetic gas in overburden rock according to claim 1, characterized in that: The number of the spraying tank (16) is three, the three spraying tanks (16) are uniformly distributed on the top of the furnace cover (2), the water outlets of the spraying tanks (16) are communicated with the inside of the furnace body (1) through independent valves, and are used for simulating the process of underground water infiltration.

6. The experimental device for studying the migration law of coal underground gasification synthetic gas in overburden rock according to claim 1, characterized in that: Fireproof bricks (17) are coated on the inner wall of the furnace body (1) and the inner wall of the furnace cover (2), a heat insulation cavity is formed between the fireproof bricks (17) and the furnace body (1), the thickness of the fireproof bricks (17) is 50-100mm, and the material is alumina refractory material.

7. The experimental device for studying the migration law of coal underground gasification synthetic gas in overburden rock according to claim 1, characterized in that: The product well (12) is a vertical pipeline structure, the bottom end of the product well (12) is communicated with the shaft of the coal seam (14), the top end penetrates through the furnace cover (2), and the outlet end of the product well (12) is provided with a gas sampling port for collecting the synthesis gas and detecting the gas composition.

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