Apparatus and method for simulating coal-bed high-temperature gasification reaction and rock thermal spalling mechanism

Abstract

The application discloses a device and method for simulating high-temperature gasification reaction of coal seams and rock thermal spalling mechanism, and belongs to the field of underground coal gasification. The inner cavity of the hearth of the device reaction furnace body is provided with a heating device, a spalling particle collecting device and a test block clamp, the top of the test block clamp is connected with a weighing sensor; a plurality of pressure sensors and thermocouples are embedded in the test block depth direction in a stepped manner; the inner cavity of the hearth is connected with an external gas injection system through a gas inlet, and is connected with an external airtightness testing system and a gas collecting and analyzing system through a gas outlet. The application can control the gas injection conditions, measure the test block weight, the internal pore gas pressure and temperature of the test block, collect the spalled particles and the generated gas in real time during the gasification process, and record the whole process of the surface crack development of the test block through photography, overcomes the single parameter monitoring defect, and can carry out multi-parameter coupling research on the thermal spalling mechanism of the coal block and the surrounding rock mass, the pore pressure and temperature evolution, and the gas generation characteristics and composition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of underground coal gasification, and particularly relates to a device and method for simulating high-temperature gasification reaction and rock thermal spalling mechanism of coal seams, especially for multi-parameter coupling research on thermal spalling mechanism of coal blocks and surrounding rock, pore pressure and temperature evolution, and gas generation characteristics and composition. BACKGROUND

[0002] Underground coal gasification (UCG) is a clean and efficient utilization technology that injects reactive gases such as oxygen into deep coal seams in situ, causing pyrolysis and chemical reactions to produce CH4, CO, H2, and other combustible gases. It realizes the transformation from physical coal mining to chemical gas extraction, with advantages such as safety, economy, efficiency, and environmental protection.

[0003] The high-temperature gasification cavity (reaction furnace) formed during UCG continuously expands. The top coal seam is exposed to high temperatures and undergoes drying, pyrolysis, and other reactions, causing the coal blocks to crack and spall into the cavity. Spalling directly affects the growth rate and shape of the cavity, changes the boundary conditions of the gasification channel, and thus affects heat and mass transfer and chemical reactions. However, spalling also increases the reaction contact area, improves gasification efficiency and coal gas quality, and reduces impurities such as tar.

[0004] However, after UCG is completed, a large combustion cavity is formed, changing the support conditions of the surrounding rock. The high temperature of gasification (up to thousands of degrees) causes the physical and mechanical properties of the surrounding rock to change dramatically, leading to thermal damage and a decrease in strength, inducing cracking and spalling, and even instability, which seriously affects the implementation conditions and safety of the process. Therefore, it is crucial to explore the cracking and spalling mechanism of coal seams and surrounding rock.

[0005] China University of Mining and Technology has been researching underground coal gasification since 1984 and has developed a new process called "long channel, large section." In 1986, the first low-pressure gasification model device (6.8m x 0.85m x 0.2m) was built in China, which can simulate different coal seam inclinations and achieve two-dimensional temperature field visualization monitoring for the first time. However, there are limitations in simulating coal seam thickness, surrounding rock conditions, and optimizing gasification furnace structure.

[0006] The high-pressure simulation device of Aachen University of Technology in Germany (reaction chamber: 2m long x 0.5m diameter, pressure 2.5MPa) is limited by the scale space and high-pressure sealed environment, making it difficult to obtain complete gasification characteristic parameters (such as temperature field, pressure field) under real geological conditions, hindering key mechanism research.

[0007] Patents CN1186840A, CN1775920A, and CN2908510Y introduce a multi-nozzle opposed gasification furnace (for water-coal slurry / coal powder), which uses jet impact to enhance turbulence, prolong residence time, and improve mass transfer efficiency, but is mainly used for above-ground gasification.

[0008] Patents CN1117917C, CN1500967A, CN2600588Y, CN1419037A are designed for underground gasification furnace of mine, which is conducive to continuous production, coal pillar recovery and scale formation, but they are all for mine test.

[0009] Patent CN104122289A designs a multi-layer composite structure gasification furnace, which can simulate different dip angles, thickness of coal seam and movement of roof and floor, and overcomes the limitations of traditional tables that cannot simulate dip angles and rock layer changes, but the structure is complex, the operation is cumbersome, and the parameters are difficult to control accurately.

[0010] The gasification device of patent CN119124919A can simulate single-sided heating of coal, and proposes to use a weight loss rate threshold to determine spalling events, but the determination method is single and cannot deeply explore the spalling mechanism.

[0011] In summary, the existing technology mainly establishes an underground coal gasification simulation test furnace, and few test researches are conducted on high-temperature cracking of coal and rock and thermal spalling mechanism. Therefore, it is an urgent need in the field of underground coal gasification to develop a test device simulating high-temperature gasification reaction of coal seam and thermal spalling mechanism of rock and to propose a corresponding test method. SUMMARY

[0012] The purpose of the present application is to overcome the defects in the prior art and provide a device and method for simulating high-temperature gasification reaction of coal seam and thermal spalling mechanism of rock. The present application can measure the injected gas (components, gas pressure, flow rate), the weight of coal / rock blocks, and the internal pore pressure and temperature of coal / rock blocks in real time during the gasification process, collect the spalled particles and produced gas in time, and use a camera device to record the development process of surface cracks of coal / rock blocks through the observation window throughout the reaction process. The present application can carry out multi-parameter coupling research on the thermal spalling mechanism of coal blocks and surrounding rock, pore pressure and temperature evolution, and gas generation characteristics and composition.

[0013] The specific technical solutions adopted by the present application are as follows:

[0014] In a first aspect, the present application provides a device for simulating high-temperature gasification reaction of coal seams and rock thermal spalling mechanism, comprising a reaction furnace body; the reaction furnace body has a sealed and heat-insulated hearth inner cavity, a heating device is arranged at the bottom of the hearth inner cavity, a spalling particle collecting device is arranged above the heating device, a test block clamp for clamping a test block is hung above the spalling particle collecting device, the top of the test block clamp extends out of the reaction furnace body and is connected with a weighing sensor to record the mass loss of the test block; the test block clamp can make the test block have only the bottom surface and one surface perpendicular to the bottom surface exposed to the hearth inner cavity, and the one surface perpendicular to the bottom surface of the test block can be observed through an observation window arranged on the reaction furnace body; a plurality of pressure sensors and thermocouples are arranged in a stepped manner along the height direction of the test block to record the changes of the pore pressure and temperature in the test block; the hearth inner cavity is provided with a hearth temperature monitor for measuring the temperature between the heating device and the heated surface of the test block, is connected with an external gas injection system through an air inlet, and is connected with an external gas tightness testing system and a gas collection and analysis system through a gas outlet.

[0015] Preferably, the reaction furnace body comprises a shell, a heat insulation material layer, a hearth and a heat-resistant pad layer; the shell is in an inverted U-shaped structure, the bottom opening is arranged on the heat-resistant pad layer, the inside is provided with a sealed hearth, and the hearth and the shell are filled with the heat insulation material layer.

[0016] Further, the hearth is made of high-aluminum fiber and the inner wall is coated with a corrosion-resistant material; the shell is made of 310s stainless steel material; the heat insulation material layer is aluminum silicate fireproof and heat insulation cotton or is obtained by pouring refractory bricks and refractory cement; and the heating device is a silicon molybdenum rod or a resistance wire embedded in the bottom of the hearth.

[0017] Preferably, the spalling particle collecting device is a mesh structure made of high-temperature resistant stainless steel and is supported by a cantilever structure arranged on the two side walls of the hearth; an integrated spalling particle collecting hole is arranged on the shell, the heat insulation material layer and the hearth, and the spalling particle collecting device can be pulled out of the reaction furnace body in a drawer type.

[0018] Preferably, the bottom of the weighing sensor is detachably connected with the test block clamp, and the top is fixed on a supporting device, so that the test block clamp is kept in a suspended state; the test block clamp is made of high-temperature resistant stainless steel, and the weighing sensor is a hook tension sensor with an accuracy of ±5g.

[0019] Preferably, the observation window is made of high-temperature resistant quartz glass, and a camera device for recording the crack development of the test block is arranged outside the observation window.

[0020] As preferred, several gas pipes and thermocouples are inserted into the test block; the gas pipes are made of high-temperature-resistant stainless steel and filled with silicon oil, one end of the gas pipes is located inside the test block and the other end extends out of the reaction furnace and is connected with a pressure sensor; the thermocouples are K-type thermocouples; the pressure sensor, the thermocouples and the weighing sensor are connected with a data recording device.

[0021] As preferred, the gas injection system comprises a high-pressure gas tank, a steam generator, an air compressor, a gas storage tank, a gas mixing device and a preheating device; the high-pressure gas tank is used for storing nitrogen or oxygen, the air compressor is connected with the inlet of the gas storage tank, the gas outlets of the high-pressure gas tank, the air compressor and the gas storage tank are respectively connected with the gas mixing device through pipelines provided with pressure reducing valves and flow meters, and the gas mixing device is connected with the gas inlet through the preheating device.

[0022] Further, the gas tightness inspection system comprises a pressure gauge and a one-way valve, and the gas outlet is connected with the pressure gauge and the one-way valve through pipelines in sequence; the gas collection and analysis system comprises a condensing device, a coal tar filtering device and a gas analysis device, and the one-way valve is connected with the condensing device, the coal tar filtering device and the gas analysis device through pipelines in sequence.

[0023] In the second aspect, the application provides a test method using the device for simulating the high-temperature gasification reaction of coal seams and the rock thermal spalling mechanism.

[0024] S1: fill the gas pipes with silicon oil, insert the gas pipes filled with silicon oil and the thermocouples into the test block, put the test block into the test block clamp, connect the upper end of the test block clamp with the weighing sensor, fix the weighing sensor on the external support device, and hang the test block clamp fixed with the test block in the inner cavity of the furnace hearth;

[0025] S2: use the gas injection system and the gas tightness inspection system to inspect the gas tightness of the high-temperature furnace body;

[0026] S3: after the gas tightness inspection, start the heating device and simultaneously inject reaction gas into the inner cavity of the furnace hearth using the gas injection system;

[0027] S4: during the reaction process, record the changes of the internal pore gas pressure, temperature and mass loss of the test block in real time through the pressure sensor, the thermocouples and the weighing sensor respectively;

[0028] S5: during the reaction process, collect the particles spalled from the test block by the spalling particle collection device, and collect and analyze the generated gas in the reaction process of the test block by the gas collection and analysis system.

[0029] S6: during the reaction process, record the development process of the surface cracks of the test block through the observation window by the camera device.

[0030] The present application has the following beneficial effects relative to the prior art:

[0031] The present application first realizes real-time measurement and collection of parameters such as pore pressure, temperature and mass in the high-temperature gasification process through modular design. Secondly, the development process of surface cracks of the coal test block is recorded by the camera equipment throughout the process to explore the crack development law. Finally, the integration of the spalling particle collection device and the gas collection and analysis system significantly improves the experimental efficiency and data reliability, providing key experimental support for the industrial application of UCG technology. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structure diagram of main components of the device of the present application;

[0033] Figure 2 It is a connection structure diagram of the device of the present application during testing;

[0034] Figure 3 It is an observation view of the reaction furnace body;

[0035] Figure 4 It is a flow chart of the method of the present application;

[0036] In the drawings, the reference signs are: high-pressure gas tank 1, pressure reducing valve 2, flow meter 3, steam generator 4, air compressor 5, gas storage tank 6, gas mixing equipment 7, preheating device 8, support device 9, data recording equipment 10, gas guide pipe 11, pressure sensor 12, thermocouple 13, weighing sensor 14, shell 15, thermal insulation material layer 16, furnace chamber 17, heat-resistant pad layer 18, test block 19, test block clamp 20, gas inlet 21, gas outlet 22, spalling particle collection device 23, heating equipment 24, pressure gauge 25, one-way valve 26, condensing device 27, coal tar filtering device 28, gas analysis device 29, in-chamber temperature monitor 30, observation window 31, camera equipment 32, spalling particle collection hole 33. DETAILED DESCRIPTION

[0037] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below in combination with the drawings. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present application can be combined accordingly without conflict.

[0038] In the description of the present application, it needs to be understood that when one element is considered to be "connected" to another element, it can be directly connected to the other element or indirectly connected, that is, there is an intermediate element. In contrast, when an element is referred to as being "directly" connected to another element, there is no intermediate element.

[0039] In the description of the present application, it needs to be understood that the expression "high pressure" in the component "high pressure gas tank 1" is only used for differentiation purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the pressure limit of the indicated technical feature.

[0040] As shown in Figure 1 A device for simulating coal seam high-temperature gasification reaction and rock thermal spalling mechanism is provided, which mainly comprises a reaction furnace body (i.e. a high-temperature furnace body), and the reaction furnace body has a sealed and heat-insulated hearth inner cavity for providing a space required for reaction.

[0041] As a preferred embodiment of the present application, the reaction furnace body mainly comprises a shell 15, a heat-insulating material layer 16, a hearth 17 and a heat-resistant pad layer 18. The shell 15 has an inverted U-shaped structure in vertical cross section, and the opening at the bottom is arranged on the heat-resistant pad layer 18. The shell 15 and the heat-resistant pad layer 18 enclose an area inside which the hearth 17 is arranged in a sealed manner. The heat-insulating material layer 16 is filled between the hearth 17 and the shell 15 to achieve the heat-insulating effect of the hearth inner cavity.

[0042] As a preferred embodiment of the present application, the size (i.e. length x width x height) of the hearth 17 inner cavity is 400mm x 350mm x 300mm, which is made of high-aluminum fiber material, and the inner wall is coated with a corrosion-resistant material, which can be a chromium oxide coating. The shell 15 is made of 310s stainless steel material. The heat-insulating material layer 16 is aluminum silicate fireproof and heat-insulating cotton, and can also be a heat-insulating layer obtained by pouring refractory bricks and refractory cement.

[0043] In the device of the present application, the bottom of the hearth inner cavity is provided with a heating device 24 capable of heating the upper test block 19. The upper side of the heating device 24 is provided with a spalling particle collecting device 23 for collecting the particles falling from the test block 19 during the heating process.

[0044] As a preferred embodiment of the present application, the heating device 24 can use silicon-molybdenum rods, or use resistance wires embedded in the bottom of the hearth 17.

[0045] As a preferred embodiment of the present application, the spalling particle collecting device 23 is located below the test block clamp 20 to collect the test block particles spalled. The spalling particle collecting device 23 can adopt a net-like structure made of high-temperature resistant stainless steel material, which is supported by a cantilever structure arranged on the two side walls of the hearth 17. Figure 3As shown, the shell 15, the heat insulation layer 16 and the hearth 17 are provided with a peeling particle collection hole 33 which is integral (i.e. in the same position and the same size hole) with the peeling particle collection device 23, and the peeling particle collection device 23 can be pulled out of the peeling particle collection hole 33.

[0046] In the device of the present application, the peeling particle collection device 23 is suspended above the test block clamp 20 which is used to clamp the test block 19. The test block clamp 20 extends into the high-temperature furnace chamber at one end and extends out of the reaction furnace body at the top end, and is connected with the weighing sensor 14 which is used to record the mass loss of the test block 19. When the test block 19 is installed and fixed in the test block clamp 20, only the bottom surface and the surface perpendicular to the bottom surface of the test block 19 are exposed to the high-temperature environment in the furnace chamber.

[0047] As a preferred embodiment of the present application, the bottom of the weighing sensor 14 is detachably connected with the test block clamp 20, and the top is fixed on the support device 9, and the test block 19, the test block clamp 20 and the weighing sensor 14 are suspended by the support device 9. The weighing sensor 14 can monitor and record the mass loss of the test block in real time. The test block clamp 20 can be made of high-temperature resistant stainless steel, and a round hole is left at the top end of the test block clamp 20, through which the weighing sensor 14 can be connected.

[0048] As a preferred embodiment of the present application, the weighing sensor 14 can use a hook tension sensor, and the sensor accuracy is ±5g, and the sensor is connected with the data recording device 10 through a wire. In actual use, data can be read every 1s and stored in the data recording device 10, and in the experiment process, the mass change curve of the test block with time, i.e. the thermal gravimetric curve of the test block, is obtained.

[0049] In the device of the present application, a transparent observation window 31 is provided on the reaction furnace body, through which the surface perpendicular to the bottom surface of the test block 19 can be observed.

[0050] As a preferred embodiment of the present application, the observation window 31 has a size (i.e. length x width) of 350mm x 300mm and is made of high-temperature resistant quartz glass. Figure 3 As shown, a camera device 32 is provided outside the observation window 31, and the crack development of the test block 19 can be recorded throughout the experiment by the camera device 32.

[0051] In the device of the present application, a plurality of pressure sensors 12 are arranged in a stepped manner along the height direction of the test block 19, and the pressure sensors 12 are used to record the pore pressure inside the test block 19. A plurality of thermocouples 13 are arranged in a stepped manner along the height direction of the test block 19, and the thermocouples 13 are used to record the temperature change inside the test block 19.

[0052] As a preferred embodiment of the present application, a plurality of gas pipes 11 and a plurality of thermocouples 13 are inserted into the test block 19. The gas pipes 11 are made of high-temperature-resistant stainless steel and filled with silicon oil. One end of the gas pipes 11 is located inside the test block 19, and the other end extends out of the reaction furnace body and is connected to the pressure sensor 12. The pressure sensor 12 can monitor and record the changes in the pore pressure inside the test block in real time. In actual use, the pressure sensor 12 can be connected to the data recording device 10. The pressure sensor 12 is a diffusion silicon pressure transmitter, which reads data every 1s and stores it in the data recording device.

[0053] As a preferred embodiment of the present application, the gas pipes 11 are inserted into the test block 19 to transmit the pore pressure generated inside the test block 19 to the pressure sensor. In this embodiment, the gas pipes 11 are made of high-temperature-resistant stainless steel and filled with silicon oil. The pore pressure acts on the silicon oil, causing the silicon oil to be squeezed in the direction of the pressure sensor, so that the value of the pore pressure can be measured.

[0054] As a preferred embodiment of the present application, the thermocouples 13 are inserted into the test block 19 to measure the temperature at the position where the pore pressure is generated inside the test block 19. In this embodiment, the thermocouples 13 are K-type thermocouple wires. The thermocouples 13 can also be connected to the data recording device 10 to transmit and store the measured data to the data recording device 10.

[0055] In the device of the present application, the furnace cavity is provided with an internal bore temperature monitor 30 for measuring the temperature changes between the heating device 24 and the heated surface of the test block 19.

[0056] As a preferred embodiment of the present application, the internal bore temperature monitor 30 is placed on the side of the furnace 17 to measure the temperature between the heating surface and the heated surface of the test block. In this embodiment, the temperature monitor 30 is a K-type thermocouple.

[0057] In the device of the present application, the furnace cavity is connected to the external gas injection system through the gas inlet 21 and connected to the external airtightness testing system and gas collection and analysis system through the gas outlet 22.

[0058] As a preferred embodiment of the present application, as shown in FIG. 1, the device of the present application comprises a furnace 17, a heating device 24, a test block 19, a data recording device 10, a pressure sensor 12, a gas pipe 11, a thermocouple 13, a gas inlet 21, a gas outlet 22, and an internal bore temperature monitor 30. Figure 2As shown in the figure, the gas injection system is arranged at the front end of the reaction furnace body, and injects reaction gas into the inner cavity of the furnace chamber through the gas inlet 21. The gas injection system mainly includes a high-pressure gas tank 1, a steam generator 4, an air compressor 5, a gas storage tank 6, a gas mixing device 7, and a preheating device 8. The high-pressure gas tank 1 is used to store nitrogen or oxygen, the gas mixing device 7 is used to mix oxygen, water vapor or air, the air compressor 5 is connected to the inlet of the gas storage tank 6, the gas outlets of the high-pressure gas tank 1, the air compressor 5 and the gas storage tank 6 are respectively connected to the gas mixing device 7 through pipelines provided with pressure reducing valves 2 and flow meters 3, and the gas mixing device 7 is connected to the gas inlet 21 through the preheating device 8. During the reaction process, the gas injection system can be used to inject nitrogen, oxygen or a mixture of oxygen, water vapor or air into the inner cavity of the furnace chamber, and the temperature of the gas injected into the inner cavity of the furnace chamber can be adjusted through the preheating device 8.

[0059] As a preferred embodiment of the present application, as shown in the figure, Figure 2 As shown in the figure, the gas-tightness inspection system is arranged at the rear end of the reaction furnace body and connected to the gas outlet 22. The gas-tightness inspection system mainly includes a pressure gauge 25 and a one-way valve 26, and the gas outlet 22 is connected to the pressure gauge 25 and the one-way valve 26 through pipelines in sequence. The gas collection and analysis system mainly includes a condensing device 27, a coal tar filtering device 28 and a gas analysis device 29, and the one-way valve 26 is connected to the condensing device 27, the coal tar filtering device 28 and the gas analysis device 29 through pipelines in sequence.

[0060] Based on the above-mentioned device for simulating coal seam high-temperature gasification reaction and rock thermal spalling mechanism, the present application also provides a test method, which takes the reaction furnace body as the center, connects the gas injection system at the front end of the furnace body, and connects the gas-tightness inspection system and the gas collection and analysis system at the rear end of the furnace body. The flow of the test method of the present application is shown in the figure Figure 4 As shown in the figure, the steps are as follows:

[0061] S1: Fill the gas guide pipe 11 with silicone oil using a syringe, insert the filled silicone oil into the gas guide pipe 11 and the thermocouple 13 into the test block 19 respectively, install the test block 19 into the test block clamp 20, connect the upper end of the test block clamp 20 to the weighing sensor 14, and fix the weighing sensor 14 on the external support device 9, so that the test block clamp 20 with the test block 19 fixed thereon is hung in the inner cavity of the furnace chamber.

[0062] S2: Perform gas-tightness inspection on the high-temperature furnace body using the gas injection system and the gas-tightness inspection system.

[0063] As a preferred embodiment of the present application, the air tightness test method used in this embodiment is as follows: nitrogen gas with a certain pressure (for example, 0.2-1 MPa) is injected by using the gas injection system, the one-way valve 26 at the rear end of the furnace body is closed, and the gas pressure gauge 25 is observed for several hours. If the pressure measured by the gas pressure gauge 25 does not decrease significantly, the device is considered to be air-tight. It should be noted that the specific numerical range for judging whether the pressure decreases significantly or not can be set and adjusted according to actual needs.

[0064] S3: After the air tightness test is passed, the heating device 24 is started and at the same time the gas injection system is used to inject the reaction gas into the inner cavity of the furnace.

[0065] As a preferred embodiment of the present application, the composition and proportion of the reaction gas (i.e. gasification agent) can be changed according to different test purposes, for example, a mixed gas with a molar ratio of oxygen to steam of 2:1 can be used. The inlet temperature of the gasification agent can be changed according to different test purposes, for example, the inlet temperature can be set to 200°C, 400°C or 600°C, and the inlet temperature of the gasification agent can be adjusted by the preheating device 8.

[0066] S4: During the reaction process, the internal pore pressure, temperature and mass loss of the test block 19 are recorded in real time by the pressure sensor 12, the thermocouple 13 and the weighing sensor 14, respectively.

[0067] S5: During the reaction process, the particles peeled off from the test block 19 are collected by the spalling particle collection device 23, and the output gas during the reaction process of the test block 19 is collected and analyzed by the gas collection and analysis system.

[0068] S6: During the reaction process, the surface crack development process of the test block 19 (coal block / rock block) is recorded by the camera device 32 through the observation window 31.

[0069] In the above process, the parameters obtained about the coal bed gasification reaction and the thermal spalling mechanism include: the internal pore pressure and the corresponding temperature of the test block, the mass loss of the test block, the morphological characteristics, elemental composition and mineral composition of the particles peeled off by heating, the gas composition of the output gas, the morphological characteristics of the heated surface of the test block, and the crack development process and law of the vertical exposed surface.

[0070] The present application will be described in more detail below in conjunction with the drawings and specific embodiments.

[0071] Embodiment

[0072] In this embodiment, before the test starts, the selected test block is subjected to corresponding pre-detection analysis. The gas injection system, the weighing sensor 14, the pressure sensor 12, the bore temperature monitor 30, the thermocouple 13 and the camera device 32 are checked to be in normal working state.

[0073] The test block 19 is cut into a cuboid with dimensions of 250x200x160mm by wire cutting, and the bottom surface of the test block is almost free of angular deviation from the test block bedding plane. In order to simulate the actual gasification conditions, the surface of the test block can be simply mechanically polished to remove external impurities to ensure its true reaction state.

[0074] After cutting and polishing, the side surface of the test block is coated with a heat insulation coating, and only the heated surface and one surface perpendicular to the heated surface are exposed. The heat insulation coating can be a nano-zirconium oxide heat insulation coating.

[0075] The test block 19 is drilled to install the gas guide pipe 11 and the thermocouple 13, and the thermocouple 13 is located at a distance of 2mm, 10mm, 20mm, 30mm and 40mm from the heated surface, and the gas guide pipe 11 is located at a distance of 10mm, 20mm, 30mm and 40mm from the heated surface. The gap between the gas guide pipe 11 and the thermocouple 13 and the test block 19 can be filled with the same kind of broken block or powder as the test block 19, and an adhesive is used to ensure its integrity.

[0076] The drilled test block 19 is placed in the test block clamp 20, and the test block clamp 20 is connected with the weighing sensor 14. The gas guide pipe 11 and the thermocouple 13 are inserted into the drilled holes. The gap between the gas guide pipe 11 and the test block clamp 20 and the furnace hole is about 1-2mm, which can be filled with a small amount of asbestos material, and a small amount of silicone oil is applied to the surface of the gas guide pipe 11 and the clamp to ensure lubricity and reduce test error.

[0077] The test block clamp 20 is connected with the support device 9. The furnace door of the reaction furnace body is closed, and the device is subjected to air tightness test.

[0078] After the air tightness test is passed, the gas injection system injects oxygen into the furnace cavity at a flow rate of 800ml / min. After the air in the device is discharged, the temperature control equipment is started to heat the heating equipment 24 to reach the set temperature condition, which is divided into four stages: 1. Initial heating stage: room temperature-300℃; 2. Medium-high temperature stage: 300℃-600℃; 3. High temperature stage: 600℃-1000℃; 4. Cooling stage: 1000℃-room temperature.

[0079] Since the test block 19 used in the embodiment is a porous medium with complex pore structure, it usually contains free water, capillary water and adsorbed water. During heating, the water in the test block gradually evaporates, and the vapor pressure in the test block gradually rises with the accumulation of steam, which can cause a tensile stress from inside to outside in the test block. When the tensile stress exceeds the tensile strength of the test block, the structure of the test block will break along the weak structure or crack, thereby causing the structure to break and peel off. On the other hand, due to the poor thermal conductivity of the test block, the temperature of the heated surface of the test block rises rapidly while the internal temperature rises relatively slowly, which forms a large temperature gradient. This temperature gradient causes the surface layer of the test block to expand, while the lower internal temperature limits its deformation, generating a tensile stress; and the diffusion of the evaporated water outward is blocked, and the vapor pressure is further increased. Under the combined action of temperature gradient and vapor pressure, the surface layer of the test block peels off. With the peeling of the surface layer of the test sample, a fresh heated surface is exposed, and the gasification and thermal peeling process continues to develop, causing the thermal peeling range and mass loss to expand, and affecting the gas production and gas composition.

[0080] In summary, during the heating process of the test block, the generation and accumulation of vapor pressure is one of the core mechanisms that cause the peeling phenomenon of the test block. The vapor is generated from the gasification of water in the test block, and factors such as the pore structure of the test block, the heating rate and the water content jointly determine the formation efficiency and accumulation degree of the vapor pressure. Under the coupling action of vapor pressure and temperature gradient, stress concentration areas are easily formed on the surface layer or inside of the test block, which eventually leads to the expansion of micro-cracks, surface breakage and thermal peeling phenomenon.

[0081] During the test, the surface crack changes of the test block 19 are recorded by the camera device 32, the weight changes of the test block 19 are monitored in real time by the weighing sensor 14, the changes of the internal pore pressure and temperature of the test block are recorded in real time by the pressure sensor 12 and the thermocouple 13, the particles peeled off are collected every 60 minutes by the particle collection system, and the produced gas is collected every 60 minutes by the gas collection system and analyzed for gas composition.

[0082] After the test is completed, the test block 19 after the reaction is taken out, and the surface morphology of the heated surface is observed and recorded.

[0083] The above-described embodiment is only a preferred scheme of the present application, and is not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, any technical scheme obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. A device for simulating high temperature gasification reactions of coal seams and rock thermal spalling mechanisms, characterized in that, The reaction furnace body includes a reaction furnace body; the reaction furnace body has a sealed and heat-insulated hearth inner cavity, the bottom of the hearth inner cavity is provided with a heating device (24), the heating device (24) is provided with a spalling particle collecting device (23) above, the spalling particle collecting device (23) is provided with a test block clamp (20) for clamping a test block (19) above, the top of the test block clamp (20) extends out of the reaction furnace body and is connected with a weighing sensor (14) to record the mass loss of the test block (19); the test block clamp (20) can make the test block (19) have only the bottom surface and the surface perpendicular to the bottom surface exposed to the hearth inner cavity, and the surface perpendicular to the bottom surface of the test block (19) can be observed through the observation window (31) provided on the reaction furnace body; a plurality of pressure sensors (12) and thermocouples (13) are arranged in a stepped manner along the height direction of the test block (19) to record the changes of the internal pore pressure and temperature of the test block (19); the hearth inner cavity is provided with a hearth temperature monitor (30) for measuring the temperature between the heating device (24) and the heated surface of the test block (19), is connected with the external gas injection system through the air inlet (21), and is connected with the external airtightness inspection system and the gas collection and analysis system through the gas outlet (22); The observation window (31) is made of high-temperature-resistant quartz glass, and a camera device (32) for recording the crack development of the test block (19) is arranged outside the observation window (31); The test block (19) is internally provided with a plurality of gas guide pipes (11) and thermocouples (13); the gas guide pipe (11) is made of high-temperature-resistant stainless steel material, is filled with silicon oil, has one end located in the test block (19) and the other end extending out of the reaction furnace body and connected with the pressure sensor (12); the thermocouple (13) is a K-type thermocouple wire; the pressure sensor (12), the thermocouple (13) and the weighing sensor (14) are connected with a data recording device (10).

2. The apparatus of claim 1, wherein, The reaction furnace body includes a shell (15), a heat insulation material layer (16), a hearth (17) and a heat-resistant pad layer (18); the shell (15) is a reverse U-shaped structure, the bottom opening is arranged on the heat-resistant pad layer (18), and the inside is provided with a sealed hearth (17), and the hearth (17) and the shell (15) are filled with the heat insulation material layer (16).

3. The apparatus of claim 2, wherein, The hearth (17) is made of high-aluminum fiber, and the inner wall is coated with a corrosion-resistant material; the shell (15) is made of 310s stainless steel material; the heat insulation material layer (16) is obtained by pouring aluminum silicate fireproof heat insulation cotton or refractory bricks and refractory cement; the heating device (24) is a silicon molybdenum rod or a resistance wire embedded in the bottom of the hearth (17).

4. The apparatus of claim 2, wherein, The spalling particle collecting device (23) is a net structure made of high-temperature-resistant stainless steel, which is supported by the cantilever structure arranged on the two side walls of the hearth (17); the shell (15), the heat insulation material layer (16) and the hearth (17) are provided with an integrated spalling particle collecting hole (33), and the spalling particle collecting device (23) can be pulled out of the reaction furnace body in a drawer type from the spalling particle collecting hole (33).

5. The apparatus of claim 1, wherein, The bottom of the weighing sensor (14) is detachably connected with the test block clamp (20), and the top is fixed on the support device (9), so that the test block clamp (20) is kept in a suspended state; the test block clamp (20) is made of high-temperature-resistant stainless steel, and the weighing sensor (14) is a hook tension sensor with an accuracy of ±5g.

6. The apparatus of claim 1, wherein, The gas injection system comprises a high-pressure gas tank (1), a steam generator (4), an air compressor (5), a gas storage tank (6), a gas mixing device (7) and a preheating device (8); the high-pressure gas tank (1) is used for storing nitrogen or oxygen, the air compressor (5) is connected with the inlet of the gas storage tank (6), the gas outlets of the high-pressure gas tank (1), the air compressor (5) and the gas storage tank (6) are respectively connected with the gas mixing device (7) through pipelines provided with pressure reducing valves (2) and flow meters (3), and the gas mixing device (7) is connected with the gas inlet (21) through the preheating device (8).

7. The apparatus of claim 6, wherein, The gas tightness inspection system comprises a pressure gauge (25) and a one-way valve (26), and the gas outlet (22) is connected with the pressure gauge (25) and the one-way valve (26) through pipelines in sequence; the gas collection and analysis system comprises a condensing device (27), a coal tar filtering device (28) and a gas analysis device (29), and the one-way valve (26) is connected with the condensing device (27), the coal tar filtering device (28) and the gas analysis device (29) through pipelines in sequence.

8. A test method using the device for simulating the high-temperature gasification reaction of coal seams and the rock thermal spalling mechanism according to any one of claims 1 to 7, characterized in that, The specific implementation is as follows: S1: fill the gas guide pipes (11) with silicon oil, insert the silicon oil filled gas guide pipes (11) and the thermocouple (13) into the test block (19) respectively, put the test block (19) into the test block clamp (20), connect the upper end of the test block clamp (20) with the weighing sensor (14), and fix the weighing sensor (14) on the external support device (9), so that the test block clamp (20) with the test block (19) is hung in the furnace cavity; S2: use the gas injection system and the gas tightness inspection system to inspect the gas tightness of the high-temperature furnace body; S3: after the gas tightness inspection is passed, start the heating device (24) and simultaneously inject the reaction gas into the furnace cavity using the gas injection system; S4: during the reaction process, record the changes of the internal pore gas pressure, temperature and mass loss of the test block (19) in real time through the pressure sensor (12), the thermocouple (13) and the weighing sensor (14) respectively; S5: during the reaction process, collect the particles peeled off from the test block (19) through the spalling particle collection device (23), and collect and analyze the generated gas in the reaction process of the test block (19) through the gas collection and analysis system; S6: during the reaction process, record the development process of the surface cracks of the test block (19) through the camera device (32) through the observation window (31).

Images