Experimental device and method for simulating underground coal bed gasification combustion

Abstract

The invention belongs to the field of coal resource mining, and discloses an experimental device and method for simulating underground coal bed gasification combustion. The experimental device comprises a gasification combustion system, an injection system, a gas analysis system and a temperature and pressure monitoring system, according to the gasification combustion system, a plurality of connecting holes with the same hole diameter are formed in a gasification furnace body and a gasification furnace cover and used for being connected with an electric heating igniter, a stainless steel pipe production well, a thermocouple and a pressure sensor, the electric heating igniter simulates a vertical well and / or a horizontal well injection well, and the stainless steel pipe production well simulates a vertical well and / or a horizontal well production well. Various well patterns and well types are simulated by adjusting the positions, the number and the insertion depth of the electric heating igniters and the stainless steel pipe production wells; the thermocouple and the pressure sensor are arranged in the remaining connecting holes in a crossed mode and used for measuring the temperature and pressure of different positions of the gasifier. According to underground coal bed gasification combustion simulation, the influence of the field well spacing mode and the well pattern on the gasification effect is considered, and the simulation result is more real and accurate.

Description

Technical Field

[0001] The invention belongs to the field of coal resource mining, in particular to the field of coalbed methane experiments, and specifically to an experimental device and method for simulating underground coalbed gasification and combustion. Background Art

[0002] Coal is a basic renewable energy source and an important industrial raw material for modern economic society. The efficient and clean development of coal conversion technology has become a strategic choice for energy development. Underground coal gasification (UCG) is one of the effective ways to achieve clean utilization of underground coal seams. It uses oxygen, air, and water vapor as gasification agents to convert coal into gases with CO, H2, and CH4 as the main components through thermal and chemical reactions. Compared with traditional coal chemical processes, UCG technology has the advantages of good safety, low investment, high efficiency, and low pollution. It is one of the important research directions of coal mining in the world.

[0003] Indoor physical simulation experimental method is one of the important means to carry out basic research on underground coal seam gasification and combustion. It plays a vital role in understanding the characteristics and mechanism of coal seam gasification and combustion, and has become an effective way to explore and develop UCG technology. Through a series of indoor basic experimental studies, it is of great significance to clarify the enrichment and migration laws of the output gas in the gasification and combustion process, the combustion, pyrolysis, gasification, and penetration characteristics of the actual coal seam, the evolution law of the characteristic field of the gasification process, the characterization of the combustion cavity, and the changes in the thermophysical properties and caving laws of the overlying rocks of the coal seam under high temperature. The existing simulated underground coal seam gasification and combustion experimental equipment is still in its infancy. Although the experimental equipment generally has a relatively complete temperature and gas monitoring system and a certain pressure and temperature resistance, it still has certain limitations.

[0004] For example, Chinese patent CN109577936A provides a simulation experimental device and experimental method for increasing coalbed methane production by burning coal seams; a complete set of experimental devices and experimental methods for filling coal rocks, saturated methane, air injection, ignition, combustion, gas production, metering, etc. are designed; wherein the experimental device includes an injection unit, a coal rock combustion unit, an ignition unit, a gas production and metering unit, and a monitoring unit; the injection unit is used to provide a gas source and inject gas into a combustion tube so that the coal sample absorbs the gas; the coal rock combustion unit includes a coal rock combustion tube, a protective cover, and a water circulation cooling device; the The ignition unit is used to realize automatic ignition; the gas production and metering unit includes a vacuum pump, a cooler, an electronic flow meter and a gas collecting tank; the experiment can simulate the process and mechanism of coal rock burning underground, heating coal seams, and producing carbon dioxide, increasing the desorption, diffusion and seepage rates of coalbed methane, thereby increasing the production of coalbed methane wells; the experimental device can monitor the process of combustion front advancement, monitor the temperature and pressure at different positions, and simulate the changes in underground temperature and pressure fields; it can simulate and optimize the optimal air injection volume, gas injection rate, gas production rate, and combustion radius, and simulate the optimal timing for burning coal seams.

[0005] However, the inventors of the present invention found that the above technology has at least the following technical problems during the process of implementing the technical solutions of the embodiments of the present invention:

[0006] (1) The actual well layout on site cannot be accurately simulated, and the influence of well pattern and well type on gasification effect is not considered. The three-dimensional distribution characteristics of coal seam gasification cavity formation, expansion and migration obtained from the experiment are significantly different from the actual situation on site.

[0007] (2) Under the conditions of high temperature and high pressure (temperature>800℃, pressure>2MPa) of gasification combustion, the experimental device did not have thermal insulation measures and did not take into account the heat loss during the experiment, resulting in large errors between the combustion heat release, coal-to-gas heat, water production, thermal efficiency, etc. obtained by simulation calculation and the actual situation on site.

[0008] Therefore, it is necessary to establish an experimental device and method that can truly simulate on-site underground coalbed gasification and combustion. Summary of the invention

[0009] The present invention aims to address at least one technical problem existing in the prior art and to provide an experimental device and method for simulating underground coalbed gasification combustion. While meeting the requirements of existing coalbed gasification experiments for temperature resistance, pressure resistance and dynamic monitoring of output gas components, the present invention achieves the characterization of combustion chamber temperature and pressure at different reaction times. At the same time, the influence of on-site well layout and well pattern on the gasification effect is taken into account, so that the simulation results are more realistic, accurate and of greater guiding value.

[0010] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0011] An experimental device for simulating underground coal seam gasification and combustion, comprising a gasification and combustion system, an injection system, a gas analysis system and a temperature and pressure monitoring system;

[0012] The gasification and combustion system comprises a gasifier, which comprises a gasifier body and a gasifier cover, wherein the gasifier body and the gasifier cover are sealed together to form a closed experimental space for loading and burning coal samples of the target coal seam; a plurality of connecting holes with the same aperture are arranged around the side of the gasifier body and the gasifier cover, wherein the connecting holes are used to connect an electric heating igniter, a stainless steel pipe production well, a thermocouple and a pressure sensor, wherein the electric heating igniter is integrated with an air intake pipe and an electric heating rod, the electric heating igniter is used to simulate a vertical well and / or a horizontal well injection well for gas injection ignition, the stainless steel pipe production well is used to simulate a vertical well and / or a horizontal well production well, and by adjusting the installation position, installation quantity and insertion depth of the electric heating igniter and the stainless steel pipe production well, the simulation of various well patterns and well types is realized; the thermocouple and the pressure sensor are cross-arranged in the remaining connecting holes, and are used to measure the temperature and pressure at different positions of the gasifier;

[0013] The air intake pipe of the electric heating igniter is connected to the injection system through an injection main pipeline, and the injection system is used to provide a high-pressure air source, a nitrogen source, a steam source and a water source;

[0014] The stainless steel pipe production well is connected to the gas analysis system through a gas outlet pipeline, and the gas analysis system is used to analyze the gas composition and volume concentration of the gas produced by the combustion of the coal sample;

[0015] The temperature and pressure monitoring system is respectively connected to the injection system, gasification combustion system and gas analysis system, and is used to collect and display metering instrument data of each system, and to regulate the equipment opening of each system according to the collected metering instrument data.

[0016] Furthermore, the stainless steel pipe simulation well in the gasification combustion system is a stainless steel pipe; one end of the stainless steel pipe extends into the furnace body, and the other end extends outside the furnace body;

[0017] The stainless steel tube located inside the furnace body is drilled with an array of holes to simulate a downhole screen;

[0018] The stainless steel pipe outside the furnace body is sealed and connected to the gasifier body and / or the gasifier cover through bolts and graphite sealing rings, and the insertion depth of the stainless steel pipe is adjusted by loosening the bolts to adjust the simulated vertical well depth and / or horizontal well length.

[0019] Furthermore, the electric heating igniter comprises an electric heating rod, a middle through pressure cap, an intermediate connecting pipe and a sleeve;

[0020] The intermediate connecting pipe is fixedly connected to the connecting hole opened on the gasifier, the inner wall of the upper end of the intermediate connecting pipe is threadedly screwed to the middle through pressure cap, and the inner wall of the bottom end of the intermediate connecting pipe is threadedly screwed to the sleeve; the bottom of the sleeve passes through the gasifier body or the gasifier cover and extends to the inside of the furnace body; the upper end of the electric heating rod is connected to the middle through pressure cap, and the bottom extends into the sleeve;

[0021] An air intake pipe is connected to one side of the pipe wall of the intermediate connecting pipe, and the air intake pipe is connected to the injection main pipeline of the injection system.

[0022] Furthermore, graphite rings are provided at the connection points between the middle connecting pipe, the middle pressure cap and the connecting hole for sealing.

[0023] Furthermore, an array of holes is drilled on the casing near the bottom to simulate a downhole screen.

[0024] Furthermore, the outside of the gasifier is wrapped with a layer of thermal insulation cover, and the thermal insulation cover is made of electrically heated glass wool.

[0025] Furthermore, the gasifier body and the gasifier cover are screwed together by a plurality of limit screws and nuts, and a self-expanding sealing gasket is arranged between the limit screws and the nuts; the self-expanding sealing gasket, the limit screws and the nuts together form a self-expanding and self-tightening balanced seal.

[0026] Furthermore, a pressure gauge, a gas mass flow controller and a gas mass flow meter are provided on the injection main pipeline and the gas outlet pipeline.

[0027] Furthermore, the injection system includes an air injection pipeline, a nitrogen injection pipeline, a steam injection pipeline and a water injection pipeline;

[0028] The air injection pipeline is connected to an air storage tank, and the air storage tank is connected to an air compressor;

[0029] The nitrogen injection pipeline is connected to the nitrogen bottle;

[0030] The steam injection pipeline is connected to a steam generator;

[0031] The water source injection pipeline is connected to a constant speed and constant pressure pump, and the constant speed and constant pressure pump is also connected to the steam generator of the steam injection pipeline;

[0032] The air injection pipeline, the nitrogen injection pipeline, the steam injection pipeline and the water source injection pipeline are connected in parallel to form a main injection pipeline.

[0033] Furthermore, the air injection pipeline, the nitrogen injection pipeline, the steam injection pipeline and the water injection pipeline are all provided with a one-way valve to prevent the oil and gas pressure in the gasifier body from being too high and causing back-injection.

[0034] Furthermore, there are two air storage tanks on the air injection pipeline connected in parallel.

[0035] Further, the gas analysis system includes a gas-liquid separator, a weighing unit, a two-stage filter and a gas analysis and data output unit;

[0036] The gas outlet pipeline of the gasification and combustion system is connected to the gas-liquid separator, which is used to separate the output gas into gas and liquid;

[0037] The liquid outlet of the gas-liquid separator is connected to a weighing unit for weighing the liquid produced by gas separation;

[0038] The gas outlet of the gas-liquid separator is connected to a two-stage filter for filtering the gas separated from the output gas; the two-stage filter is connected to the gas analysis and data output unit for performing gas component analysis on the separated and purified gas in the output gas and outputting the percentage content of each gas component.

[0039] Furthermore, the temperature and pressure monitoring system includes a data acquisition unit, a data storage and display unit, and a device control unit;

[0040] The data acquisition unit is used to collect the metering instrument data of each system, and store and display it in real time in the data storage and display unit; the device control unit is used to control the equipment opening of each system according to the metering instrument data displayed by the data storage and display unit.

[0041] At the same time, the present invention also provides an experimental method for simulating underground coal seam gasification combustion, which is implemented using the experimental device as described in any of the above items, and the experimental method comprises the following steps:

[0042] Step S1: preparing experimental samples;

[0043] According to the physical properties of the stratum to be simulated, a certain mass of clay and water are weighed and made into a mud cap layer according to a certain ratio; and a certain mass of the target coal seam debris coal sample is weighed;

[0044] Step S2: loading of experimental samples, layout of well pattern and type, and air tightness inspection of experimental device;

[0045] Step S201: coating a layer of mud cover on the inner wall of the gasifier body and the gasifier cover, and laying a layer of crushed coal on the bottom of the gasifier body to simulate the underground coal seam;

[0046] Step S202: fasten the electric heating igniter to the connection hole of the gasifier to simulate the gas injection vertical well / horizontal well; fasten the stainless steel pipe production well to the connection hole of the gasifier to simulate the production vertical well / horizontal well; connect the thermocouple and pressure sensor to the other connection holes of the gasifier, wrap the outside of the gasifier with a heat insulation cover, and complete the well pattern layout;

[0047] Step S203: Connect the gas outlet pipeline to the stainless steel pipe production well, connect the injection main pipeline to the electric heating igniter, then open the valve on the nitrogen injection pipeline, introduce nitrogen, and close the valve on the gas outlet pipeline to check the air tightness of the entire experimental device;

[0048] Step S3: system testing and preheating of the gasifier body;

[0049] Step S301: Check the connectivity and sealing performance of the pipelines between the systems. After confirming that they are connected and leak-free, adjust the injection flow rate on the injection main pipeline, record the inlet and outlet pressure differences corresponding to different injection flows, and calculate the porosity and permeability of the simulated coal seam corresponding to different injection flows;

[0050] Step S302: Turn on the control system power supply, adjust the nitrogen injection flow rate to less than 1L / min, and set the temperature of the electric heating igniter for preheating according to the actual needs of the project site;

[0051] Step S4: starting the coalbed gasification experiment and performing experimental regulation;

[0052] Step S401: adjust the temperature of the electric heating igniter, switch the injection pipeline of the injection system, inject air into the gasifier body and adjust the injection flow rate on the injection main pipeline, and start the coalbed gasification experiment; record the temperature of each temperature point and the pressure value of each pressure measuring point according to the experimental process, and analyze the experimental progress according to the temperature and pressure value data;

[0053] Step S402: During the experiment, the output gas components, various temperature and pressure value data are comprehensively considered to adjust the temperature of the electric heating igniter, the injection flow rate of the injection main pipeline and the valve size on the gas outlet pipeline to maintain stable combustion of the simulated coal seam;

[0054] Step S403: When the highest temperature of the temperature measuring point on the gasifier body rises to above 850°C, the temperature of the electric heating igniter is adjusted to 0°C, the injection flow rate of the injection main pipeline is reduced to 0L / min, and the experimental simulation is terminated;

[0055] Step S404: switch the injection pipeline of the injection system, inject nitrogen into the gasifier body until the gasifier body cools down, then open the gasifier cover, take photos of the simulated coal seam in the gasifier body and take samples for analysis;

[0056] Step S405: export the experimental data and calculate the experimental parameters.

[0057] Furthermore, in step S405, the derived experimental data include temperature, pressure and gas composition; the calculated experimental parameters include combustion coal quality, heat release and water production.

[0058] Compared with the prior art, the beneficial effects of the present invention are:

[0059] (1) The experimental device for simulating underground coal seam gasification and combustion of the present invention has a gasification and combustion system with multiple connection holes of the same diameter on the side of the gasifier body and the gasifier cover for connecting the electric heating igniter, the stainless steel pipe production well, the thermocouple and the pressure sensor, wherein the electric heating igniter is integrated with an air inlet pipe and an electric heating rod for simulating the injection well for gas injection and automatic ignition, the stainless steel pipe production well is used to simulate the vertical well and / or horizontal well production well, and by adjusting the position, number and insertion depth of the electric heating igniter and the stainless steel pipe production well, the simulation of various well patterns can be effectively realized; the thermocouple and the pressure sensor are cross-arranged in the remaining connection holes for real-time measurement of the temperature and pressure at different positions of the gasifier; through the above-mentioned structural design, the experimental device of the present invention can more realistically and accurately simulate the actual production conditions of different well patterns on site, further clarify the coal seam gasification and combustion mechanism, and optimize and guide the well layout method on site;

[0060] (2) The experimental device for simulating underground coal seam gasification combustion of the present invention has an electric heating igniter which can effectively realize the temperature control, heating and ignition functions of 0-700°C through structural design. At the same time, the sealing performance is good when the injection pressure does not exceed 5MPa and the combustion temperature does not exceed 1000°C, which can better meet the experimental requirements and effectively ensure the safety and controllability of the ignition process. At the same time, the electric heating igniter is small in size and reliable in connection. It can ensure that the thermal efficiency of the electric heating igniter can be maintained stable as the gas injection amount increases, avoiding the possibility of experimental failure caused by insufficient coal seam combustion due to reduced heating efficiency due to increased gas injection amount, thereby improving the operational reliability of the experimental device;

[0061] (3) The experimental device of the present invention includes: a gasifier body with temperature and pressure monitoring function, a gas injection system, and a gas analysis system, which can quickly and efficiently carry out three-dimensional underground coalbed gasification simulation experiments; the equipment is simple to operate and fully functional, and has a large combustion space (greater than 60L), a high pressure-bearing gasifier body (pressure resistance 5MPa), and good temperature resistance (temperature resistance 1000℃); the gasifier body adopts an internal mud cover layer + an external glass wool insulation sleeve, which has good insulation effect and low heat loss; the gasifier body is large enough and is simulated according to the on-site well layout and well pattern; compared with the existing experimental simulation device, the experimental device of the present invention simulates the change law that is more real, accurate, and fits the site; and adopts an electric ignition method, which has better safety and controllability;

[0062] (4) The experimental method for simulating underground coal seam gasification combustion provided by the present invention not only meets the requirements of existing coal seam gasification experimental temperature resistance, pressure resistance strength and dynamic monitoring of output gas components, but also realizes the characterization of temperature and pressure in the combustion chamber at different positions and different reaction times. At the same time, combined with experimental data calculation and coal seam morphology characterization after combustion, important parameters in the coal seam combustion process can be obtained, and the following series of mechanisms in the underground coal seam gasification combustion process can be explored, including: the three-dimensional distribution characteristics of gas cavity formation, expansion and migration during coal seam gasification combustion, the influence of different well patterns on gasification effect, the change of thermal physical properties and caving law of coal seam overburden under high temperature (cavities will be formed after coal seam combustion. After the experiment is completed, the model body is opened to observe the morphology of the cavity. Combined with the physical property analysis of the coal seam after combustion, the change of thermal physical properties and caving law of coal seam overburden under high temperature can be studied), etc., which provides a theoretical basis for underground coal seam screening, optimization of well layout and control of injection and production parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a schematic diagram of the overall structure of the experimental device according to an embodiment of the present invention;

[0064] Figure 2 A schematic diagram of the structure of a gasifier according to an embodiment of the present invention;

[0065] Figure 3 A schematic diagram of the structure of a gasification furnace cover according to an embodiment of the present invention;

[0066] Figure 4 It is a schematic diagram of the structure of an electric heating igniter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0067] 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.

[0068] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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.

[0069] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0070] Example 1

[0071] Combination Figure 1-4 As shown, an embodiment of the present invention provides an experimental device for simulating underground coal seam gasification and combustion, including an injection system 1, a gasification and combustion system 2, a gas analysis system 3 and a temperature and pressure monitoring system (not shown);

[0072] The gasification and combustion system 1 includes a gasifier, which includes a gasifier body 201 and a gasifier cover 202. The gasifier body 201 and the gasifier cover 202 are sealed together to form a closed experimental space for loading and burning coal samples of the target coal seam; the gasifier body 201 is provided with a plurality of first connecting holes 2011 around the side, and the gasifier cover 202 is provided with a plurality of second connecting holes 2021. The first connecting holes 2011 and the second connecting holes 2021 are used to connect the electric heating igniter 4, the stainless steel pipe production well 6, and the thermocouple and a pressure sensor, wherein the electric heating igniter is integrated with an air inlet pipe 4031 and an electric heating rod 401, which are used to simulate a vertical well and / or a horizontal well injection well for gas injection and automatic ignition, and the stainless steel pipe production well 6 is used to simulate a vertical well and / or a horizontal well production well, and by adjusting the installation position, installation quantity and insertion depth of the electric heating igniter 4 and the stainless steel pipe production well 6, the simulation of various well patterns and well types is realized; the thermocouple and the pressure sensor are cross-arranged in the remaining connection holes, which are used to measure the temperature and pressure at different positions of the gasifier;

[0073] The air inlet pipe 4031 of the electric heating igniter 4 is connected to the injection system 1 through the injection main pipeline 21, and the injection system 1 is used to provide a high-pressure air source, a nitrogen source, a steam source and a water source;

[0074] The stainless steel pipe production well 6 is connected to the gas analysis system 3 through a gas outlet pipeline 22, and the gas analysis system 3 is used to analyze the gas composition and volume concentration of the gas produced by the combustion of the coal sample;

[0075] The temperature and pressure monitoring system is respectively connected to the injection system 1, the gasification and combustion system 2 and the gas analysis system 3, and is used to collect and display the metering instrument data of each system, and to adjust the equipment opening of each system according to the collected metering instrument data.

[0076] Specifically, if Figure 2 As shown, the gasifier body 201 is a high-pressure cylindrical combustion chamber with an inner diameter of Φ400mm×height of 776mm, a wall thickness of 100mm, and a material of N10276, with a pressure resistance of 0-5MPa and a temperature resistance of 0-1000°C.

[0077] Combination Figure 3 As shown, the gasifier body 201 and the gasifier cover 202 are tightly connected by a plurality of limit screws 2024 and nuts 2023, and a self-expanding sealing gasket (not shown) is arranged between the limit screws 2024 and the nuts 2023; the self-expanding sealing gasket, the limit screws and the nuts together form a self-expanding and self-tightening balanced seal.

[0078] The gasifier body 201 is provided with a plurality of first connection holes 2011 with a hole diameter of 6 mm on the side, and the gasifier cover 202 is provided with a plurality of second connection holes 2021 with a hole diameter of 6 mm. By setting the first connection holes 2011 provided on the side of the gasifier body 201 and the second connection holes 2021 provided on the gasifier cover 202 to have the same hole diameter, the installation positions of the electric heating igniter 4, the stainless steel pipe production well 6, the thermocouple and the pressure sensor can be conveniently and directly adjusted to simulate various well patterns and well types, wherein the electric heating igniter 4 connected on the side of the gasifier body 201 is used to simulate the vertical well injection ignition well, and the stainless steel pipe production well 6 connected on the side of the gasifier body 201 is used to simulate the vertical well production well; the electric heating igniter 4 connected on the gasifier cover 202 is used to simulate the horizontal well injection ignition well, and the stainless steel pipe production well 6 connected on the gasifier cover 202 is used to simulate the horizontal well production well.

[0079] At the same time, the number of the electric heating igniter 4 and the stainless steel pipe production well 6 can be one or more, the insertion depth of the electric heating igniter 4 represents the ignition position, and the insertion depth of the stainless steel pipe simulation well 6 represents the vertical well depth and / or the horizontal section length of the horizontal well. These field data can be converted into the insertion length of the simulation well in the laboratory using similar criteria.

[0080] By arranging the position, quantity and insertion depth of the electric heating igniter 4 and the stainless steel pipe production well 6, it is possible to simulate various well patterns and well types such as common well patterns (such as five-point type, inverted seven-point type, inverted nine-point type, etc.) and common well types (such as vertical wells, horizontal wells, double horizontal wells, U-shaped horizontal wells, one injection and multiple production, multiple injections and multiple production, etc.), and it is also possible to simulate the actual production conditions of different well patterns and well types on site more realistically and accurately, further clarify the coalbed gasification combustion mechanism, and optimize and guide the on-site well layout method according to the simulation results.

[0081] In an embodiment of the present invention, the stainless steel pipe simulation well 6 is a stainless steel pipe; one end of the stainless steel pipe extends into the furnace body, and the other end extends outside the furnace body; wherein, the stainless steel pipe located inside the furnace body is drilled with an array of holes for simulating the downhole screen pipe; the stainless steel pipe located outside the furnace body is sealed and connected to the gasifier body and / or the gasifier cover through bolts and graphite sealing rings; the stainless steel pipe simulation well 6 can change the length of the vertical well and the horizontal well by unscrewing the screws to change the insertion depth of the stainless steel pipe when the model body is under pressure during the experiment, thereby realizing the simulation of the new underground coal seam gasification process "controlled retreat gasification process" (the controlled retreat gasification process refers to the process of artificially changing the length of the production well during the coal seam combustion process to realize the axial movement and combustion of the coal seam along the horizontal section pipeline).

[0082] like Figure 4As shown, the electric heating igniter 4 is connected to the gasifier body 201, has a power of 500KW, can realize gas injection and temperature control heating at the same time, and is used to simulate the gas injection ignition of the vertical well injection well.

[0083] The electric heating igniter 4 includes an electric heating rod 401, a center-through pressure cap 402, an intermediate connecting pipe 403 and a sleeve 404; the intermediate connecting pipe 403 is fixedly connected to the first connecting hole 2011 opened on the gasifier body 201, the inner wall of the upper end of the intermediate connecting pipe 403 is threadedly screwed to the center-through pressure cap 402, and the inner wall of the bottom end of the intermediate connecting pipe 403 is threadedly screwed to the sleeve 404; the sleeve 404 passes through the gasifier body 202 and extends to the inside of the furnace body, and an array hole 4041 is drilled near the bottom of the sleeve 404 to simulate a downhole screen pipe; the upper end of the electric heating rod 401 is connected to the center-through pressure cap 402, and the bottom extends into the sleeve 404; one side of the pipe wall of the intermediate connecting pipe 403 is connected to an air intake pipe 4031, and the air intake pipe 4031 is connected to the injection main pipeline 21 of the injection system 1.

[0084] At the same time, graphite rings are provided at the connection points between the middle connecting tube 403, the middle pressure cap 402 and the first connecting hole 2011 for sealing. The graphite ring sealing structure is simple, the connection is reliable, and it has good sealing, thermal conductivity and high temperature resistance.

[0085] The electric heating igniter can effectively realize the temperature control, heating and ignition functions of 0-700℃ through structural design. At the same time, it has good sealing performance when the injection pressure does not exceed 5MPa and the combustion temperature does not exceed 1000℃, which can better meet the experimental needs and effectively ensure the safety and controllability of the ignition process. At the same time, the electric heating igniter is small in size and reliable in connection. It can ensure that the thermal efficiency of the electric heating igniter can remain stable as the gas injection volume increases, avoiding the possibility of insufficient coal seam combustion and experimental failure due to increased gas injection volume and reduced heating efficiency, and improving the reliability of the operation of the experimental device.

[0086] In addition, the outside of the gasifier is wrapped with a layer of thermal insulation cover 5, which is made of electrically heated glass wool (artificial inorganic fiber) material, which can effectively avoid heat loss during the experiment and more realistically simulate the original formation temperature.

[0087] The end of the gasifier body 201 away from the gasifier cover 202 is the bottom of the gasifier body, and a plurality of first furnace body supports 14 are arranged at the bottom of the gasifier body. A plurality of second furnace body supports 15 are arranged on the side wall of the gasifier body in a direction perpendicular to the first furnace body supports 14. The first furnace body supports 14 and the second furnace body supports 15 are used to support the gasifier body vertically or horizontally. The gasifier body 201 is also provided with two first lifting ears 2012 for convenient installation and lifting, and the gasifier cover 202 is also provided with two second lifting ears 2022 for convenient installation and lifting.

[0088] The injection main pipeline 21 and the gas outlet pipeline 22 are both provided with a pressure gauge 7, a gas mass flow controller 8 and a gas mass flow meter (not shown). The pressure gauge 7 is used to measure the injection pressure and the production pressure; the gas mass flow controller 8 is used to control the mass flow of the injected gas and the produced gas, and the flow adjustment range of the gas mass flow controller is 0-30L / min, the error is ±0.1%, and the pressure resistance is 10MPa; the gas mass flow meter is used to accurately measure the gas injection volume and the gas production volume.

[0089] Since the gas mass flow controller 8 will have certain errors after being used for a long time, the on-site measurement error will seriously affect the accuracy of the simulation results. Therefore, in the embodiment of the present invention, a gas mass flow meter is added to the injection main pipeline 21 and the gas outlet pipeline 22 to accurately measure the gas injection volume and gas production volume, further improve the measurement accuracy, reduce the measurement error, and improve the simulation accuracy.

[0090] See also Figure 1 As shown, the injection system 1 includes an air injection pipeline, a nitrogen injection pipeline, a steam injection pipeline and a water source injection pipeline.

[0091] The air injection pipeline is connected to two parallel air tanks, namely the first air tank 10 and the second air tank 11, and the two parallel air tanks are both connected to an air compressor 9; the maximum pressure of the air compressor 9 reaches 8MPa, and the capacity of the two parallel air tanks is 50L and the pressure resistance is 8MPa. By caching the compressed high-pressure air source by the air compressor 9 into the two parallel air tanks, the air supply can be maintained uninterruptedly.

[0092] The nitrogen injection pipeline is connected to a nitrogen bottle 12, and the volume of the nitrogen bottle 12 is 40L and the pressure is 15MPa.

[0093] The steam injection pipeline is connected to a steam generator 13. The steam generator 13 can provide a maximum steam temperature of 300°C and a mass flow rate of 0-2kg / h.

[0094] The water source injection pipeline is connected to a constant speed and constant pressure pump 14, and the pumping speed of the constant speed and constant pressure pump 14 is 0-200ml / min; at the same time, the constant speed and constant pressure pump 14 is also connected to the steam generator 13 of the steam injection pipeline, for providing steam water source for the steam generator 13.

[0095] The air injection pipeline, the nitrogen injection pipeline, the steam injection pipeline and the water injection pipeline are connected in parallel to the injection main pipeline 21.

[0096] The air injection pipeline, nitrogen injection pipeline, steam injection pipeline and water injection pipeline are all provided with a one-way valve 23 to prevent the oil and gas pressure in the gasifier body from being too high and being back-injected into each injection pipeline.

[0097] The gas analysis system 3 includes a gas-liquid separator 17, a weighing unit 18, a two-stage filter 19 and a gas analysis and data output unit 20;

[0098] The gas outlet pipeline 22 of the gasification combustion system 2 is connected to the gas-liquid separator 17 for performing gas-liquid separation on the output gas;

[0099] The liquid outlet of the gas-liquid separator 17 is connected to a weighing unit 18 for weighing the liquid separated from the gas;

[0100] The gas outlet of the gas-liquid separator 17 is connected to a two-stage filter 19, which is used to filter the gas separated from the output gas and further filter out the liquid and solid impurities therein; the two-stage filter 19 is connected to the gas analysis and data output unit 20, which is used to perform gas component analysis on the gas separated and purified from the output gas and output the percentage content of each gas component.

[0101] The temperature and pressure monitoring system includes a data acquisition unit, a data storage and display unit, and a device control unit; the data acquisition unit is used to collect metering instrument data of each system, and store and display it in real time in the data storage and display unit; the device control unit is used to control the equipment opening of each system according to the metering instrument data displayed by the data storage and display unit.

[0102] Example 2

[0103] The embodiment of the present invention provides an experimental method for simulating underground coal seam gasification combustion, which is implemented using the experimental device described in Example 1. The experimental method includes the following steps:

[0104] Step S1: preparing experimental samples;

[0105] According to the physical properties of the stratum to be simulated, a certain mass of clay and water is weighed and prepared into a mud cap layer in a certain ratio; and a certain mass of the target coal seam debris coal sample is weighed.

[0106] Step S2: loading of experimental samples, layout of well pattern and type, and air tightness inspection of experimental device;

[0107] Step S201: coating a layer of mud cover on the inner wall of the gasifier body and the gasifier cover; laying a layer of 45 cm high and 20 cm thick shredded coal (Xukuang coal) at the bottom of the gasifier body to simulate the underground coal seam;

[0108] Since the mud cap layer is prepared according to the physical properties of the formation to be simulated, it can be used to insulate the gasifier body, reduce heat loss, and make thermal efficiency calculations more realistic and accurate. On the other hand, it can make the simulation experiment more in line with the physical properties of the formation to be simulated on site, further ensuring that the simulation results are authentic and reliable.

[0109] Step S202: fasten the electric heating igniter to the connection hole of the gasifier to simulate the gas injection vertical well / horizontal well; fasten the stainless steel pipe production well to the connection hole of the gasifier to simulate the production vertical well / horizontal well; connect the thermocouple and pressure sensor to the other connection holes of the gasifier, wrap the outside of the gasifier with a heat insulation cover, and complete the well pattern layout;

[0110] Step S203: Connect the gas outlet pipeline to the stainless steel pipe production well, connect the injection main pipeline to the electric heating igniter, then open the valve on the nitrogen injection pipeline, introduce nitrogen, and close the valve on the gas outlet pipeline to check the air tightness of the entire experimental device;

[0111] Step S3: system testing and preheating of the gasifier body;

[0112] Step S301: Check the connectivity and sealing performance of the pipelines between the systems. After confirming that they are connected and leak-free, adjust the injection flow rate on the injection main pipeline to 1L / min, 3L / min, and 5L / min, respectively, record the inlet and outlet pressure differences corresponding to different injection flow rates, and calculate the porosity and permeability of the simulated coal seam corresponding to different injection flow rates;

[0113] Step S302: Turn on the control system power supply, adjust the nitrogen injection flow rate to less than 1L / min, set the electric heating igniter temperature for preheating according to the actual needs of the site, and use the injected inert gas nitrogen for heat conduction to preheat the entire model to the original formation temperature;

[0114] Step S4: starting the coalbed gasification experiment and performing experimental regulation;

[0115] Step S401: adjust the temperature of the electric heating igniter, switch the injection pipeline of the injection system, inject air into the gasifier body and adjust the injection flow rate on the injection main pipeline, and start the coalbed gasification experiment; record the temperature of each temperature point and the pressure value of each pressure measuring point according to the experimental process, and analyze the experimental progress according to the temperature and pressure value data;

[0116] Step S402: During the experiment, the output gas components, various temperature and pressure value data are comprehensively considered to adjust the temperature of the electric heating igniter, the injection flow rate of the injection main pipeline and the valve size on the gas outlet pipeline to maintain stable combustion of the simulated coal seam;

[0117] Step S403: When the highest temperature of the temperature measuring point on the gasifier body rises to above 850°C, the temperature of the electric heating igniter is adjusted to 0°C, the injection flow rate of the injection main pipeline is reduced to 0L / min, and the experimental simulation is terminated;

[0118] Step S404: switch the injection pipeline of the injection system, inject nitrogen into the gasifier body until the gasifier body cools down, then open the gasifier cover, take photos of the simulated coal seam in the gasifier body and take samples for analysis;

[0119] Step S405: Export the experimental data such as temperature, pressure, gas composition, etc., and calculate the experimental parameters such as combustion coal quality, heat release, water production, etc.

[0120] The above description is only an embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the application scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. An experimental device for simulating underground coal seam gasification and combustion, characterized in that: Including gasification and combustion system, injection system, gas analysis system and temperature and pressure monitoring system; The gasification and combustion system comprises a gasifier, which comprises a gasifier body and a gasifier cover, wherein the gasifier body and the gasifier cover are sealed together to form a closed experimental space for loading and burning coal samples of the target coal seam; a plurality of connecting holes with the same aperture are arranged around the side of the gasifier body and the gasifier cover, wherein the connecting holes are used to connect an electric heating igniter, a stainless steel pipe production well, a thermocouple and a pressure sensor, wherein the electric heating igniter is integrated with an air intake pipe and an electric heating rod, the electric heating igniter is used to simulate a vertical well and / or a horizontal well injection well for gas injection ignition, the stainless steel pipe production well is used to simulate a vertical well and / or a horizontal well production well, and by adjusting the installation position, installation quantity and insertion depth of the electric heating igniter and the stainless steel pipe production well, the simulation of various well patterns and well types is realized; the thermocouple and the pressure sensor are cross-arranged in the remaining connecting holes, and are used to measure the temperature and pressure at different positions of the gasifier; The air intake pipe of the electric heating igniter is connected to the injection system through an injection main pipeline, and the injection system is used to provide a high-pressure air source, a nitrogen source, a steam source and a water source; The stainless steel pipe production well is connected to the gas analysis system through a gas outlet pipeline, and the gas analysis system is used to analyze the gas composition and volume concentration of the gas produced by the combustion of the coal sample; The temperature and pressure monitoring system is respectively connected to the injection system, gasification combustion system and gas analysis system, and is used to collect and display metering instrument data of each system, and to regulate the equipment opening of each system according to the collected metering instrument data.

2. The experimental device according to claim 1, characterized in that: The stainless steel pipe simulation well in the gasification combustion system is a stainless steel pipe; one end of the stainless steel pipe extends into the furnace body, and the other end extends outside the furnace body; The stainless steel tube located inside the furnace body is drilled with an array of holes to simulate a downhole screen; The stainless steel pipe outside the furnace body is sealed and connected to the gasifier body and / or the gasifier cover through bolts and graphite sealing rings, and the insertion depth of the stainless steel pipe is adjusted by loosening the bolts to adjust the simulated vertical well depth and / or horizontal well length.

3. The experimental device according to claim 1, characterized in that: The electric heating igniter comprises an electric heating rod, a middle through pressure cap, an intermediate connecting pipe and a sleeve; The intermediate connecting pipe is fixedly connected to the connecting hole opened on the gasifier, the inner wall of the upper end of the intermediate connecting pipe is threadedly screwed to the middle through pressure cap, and the inner wall of the bottom end of the intermediate connecting pipe is threadedly screwed to the sleeve; the bottom of the sleeve passes through the gasifier body or the gasifier cover and extends to the inside of the furnace body; the upper end of the electric heating rod is connected to the middle through pressure cap, and the bottom extends into the sleeve; An air intake pipe is connected to one side of the pipe wall of the intermediate connecting pipe, and the air intake pipe is connected to the injection main pipeline of the injection system.

4. The experimental device according to claim 3, characterized in that: The connection between the middle connecting pipe, the middle pressure cap and the connecting hole is provided with a graphite ring for sealing.

5. The experimental device according to claim 3, characterized in that: The casing is drilled with array holes near the bottom to simulate the downhole screen.

6. The experimental device according to claim 1, characterized in that: The outside of the gasifier is wrapped with a thermal insulation cover, and the thermal insulation cover is made of electrically heated glass wool.

7. The experimental device according to any one of claims 1 to 6, characterized in that: The gasifier body and the gasifier cover are connected by tightening through a plurality of limiting screws and nuts, and a self-expanding sealing gasket is arranged between the limiting screws and the nuts; the self-expanding sealing gasket, the limiting screws and the nuts together form a self-expanding and self-tightening balanced seal.

8. The experimental device according to any one of claims 1 to 6, characterized in that: The injection main pipeline and the gas outlet pipeline are both provided with a pressure gauge, a gas mass flow controller and a gas mass flow meter.

9. The experimental device according to claim 8, characterized in that: The injection system includes an air injection pipeline, a nitrogen injection pipeline, a steam injection pipeline and a water source injection pipeline; The air injection pipeline is connected to an air storage tank, and the air storage tank is connected to an air compressor; The nitrogen injection pipeline is connected to the nitrogen bottle; The steam injection pipeline is connected to a steam generator; The water source injection pipeline is connected to a constant speed and constant pressure pump, and the constant speed and constant pressure pump is also connected to the steam generator of the steam injection pipeline; The air injection pipeline, the nitrogen injection pipeline, the steam injection pipeline and the water source injection pipeline are connected in parallel to form a main injection pipeline.

10. The experimental device according to claim 9, characterized in that: The air injection pipeline, the nitrogen injection pipeline, the steam injection pipeline and the water injection pipeline are all provided with a one-way valve to prevent the oil and gas pressure in the gasifier body from being too high and causing back-injection.

11. The experimental device according to claim 9, characterized in that: There are two air storage tanks on the air injection pipeline connected in parallel.

12. The experimental device according to claim 9, characterized in that: The gas analysis system includes a gas-liquid separator, a weighing unit, a two-stage filter and a gas analysis and data output unit; The gas outlet pipeline of the gasification and combustion system is connected to the gas-liquid separator, which is used to separate the output gas into gas and liquid; The liquid outlet of the gas-liquid separator is connected to a weighing unit for weighing the liquid produced by gas separation; The gas outlet of the gas-liquid separator is connected to a two-stage filter for filtering the gas separated from the output gas; the two-stage filter is connected to the gas analysis and data output unit for performing gas component analysis on the separated and purified gas in the output gas and outputting the percentage content of each gas component.

13. The experimental device according to claim 1, characterized in that: The temperature and pressure monitoring system includes a data acquisition unit, a data storage and display unit, and a device control unit; The data acquisition unit is used to collect the metering instrument data of each system, and store and display it in real time in the data storage and display unit; The device control unit is used to control the device opening of each system according to the metering instrument data displayed by the data storage and display unit.

14. An experimental method for simulating underground coal seam gasification combustion, implemented using the experimental device according to any one of claims 1 to 13, characterized in that: The experimental method comprises the following steps: Step S1: preparing experimental samples; According to the physical properties of the stratum to be simulated, a certain mass of clay and water are weighed and made into a mud cap layer according to a certain ratio; and a certain mass of the target coal seam debris coal sample is weighed; Step S2: loading of experimental samples, layout of well pattern and type, and air tightness inspection of experimental device; Step S201: coating a layer of mud cover on the inner wall of the gasifier body and the gasifier cover, and laying a layer of crushed coal on the bottom of the gasifier body to simulate the underground coal seam; Step S202: fasten the electric heating igniter to the connection hole of the gasifier to simulate the gas injection vertical well / horizontal well; fasten the stainless steel pipe production well to the connection hole of the gasifier to simulate the production vertical well / horizontal well; connect the thermocouple and pressure sensor to the other connection holes of the gasifier, wrap the outside of the gasifier with a heat insulation cover, and complete the well pattern layout; Step S203: Connect the gas outlet pipeline to the stainless steel pipe production well, connect the injection main pipeline to the electric heating igniter, then open the valve on the nitrogen injection pipeline, introduce nitrogen, and close the valve on the gas outlet pipeline to check the air tightness of the entire experimental device; Step S3: system testing and preheating of the gasifier body; Step S301: Check the connectivity and sealing performance of the pipelines between the systems. After confirming that they are connected and leak-free, adjust the injection flow rate on the injection main pipeline, record the inlet and outlet pressure differences corresponding to different injection flows, and calculate the porosity and permeability of the simulated coal seam corresponding to different injection flows; Step S302: Turn on the control system power supply, adjust the nitrogen injection flow rate to less than 1L / min, and set the temperature of the electric heating igniter for preheating according to the actual needs of the project site; Step S4: starting the coalbed gasification experiment and performing experimental regulation; Step S401: adjusting the temperature of the electric heating igniter, switching the injection pipeline of the injection system, injecting air into the gasifier body and adjusting the injection flow rate on the injection main pipeline, and starting the coalbed gasification experiment; Record the temperature of each temperature point and the pressure value of each pressure measuring point according to the experimental process, and analyze the experimental progress based on the temperature and pressure value data; Step S402: During the experiment, the output gas components, various temperature and pressure value data are comprehensively considered to adjust the temperature of the electric heating igniter, the injection flow rate of the injection main pipeline and the valve size on the gas outlet pipeline to maintain stable combustion of the simulated coal seam; Step S403: When the highest temperature of the temperature measuring point on the gasifier body rises to above 850°C, the temperature of the electric heating igniter is adjusted to 0°C, the injection flow rate of the injection main pipeline is reduced to 0L / min, and the experimental simulation is terminated; Step S404: switch the injection pipeline of the injection system, inject nitrogen into the gasifier body until the gasifier body cools down, then open the gasifier cover, take photos of the simulated coal seam in the gasifier body and take samples for analysis; Step S405: export the experimental data and calculate the experimental parameters.

15. The experimental method according to claim 14, characterized in that: In step S405, the derived experimental data include temperature, pressure and gas composition; the calculated experimental parameters include combustion coal quality, heat release and water production.

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