System and method for in-situ pyrolysis of oil-rich coal coupled with combustion of lean coal in a boiler

Abstract

This invention provides a system and method for in-situ pyrolysis of rich oil coal coupled with combustion in a lean coal boiler. The system includes a rich oil coal in-situ pyrolysis subsystem and a boiler subsystem. The rich oil coal in-situ pyrolysis subsystem includes a gas mixer, the outlet of which is connected to the inlet of an injection well. The boiler subsystem includes a boiler and a turbine unit. The gas mixer is used to mix the flue gas discharged from the boiler and the extraction steam from the turbine unit. The extraction well is used to supply the combustible gas generated from the in-situ pyrolysis of rich oil coal to the boiler. By performing in-situ pyrolysis of rich oil coal using a mixture of high-temperature flue gas and high-temperature extraction steam, the extraction efficiency of the rich oil coal in-situ pyrolysis can be improved. The heat generated by the combustion of the combustible gas produced from the pyrolysis of rich oil coal assists in the combustion of lean coal, thereby improving the combustion efficiency and stability of the lean coal boiler.

Description

Technical Field

[0001] This invention belongs to the field of in-situ pyrolysis technology of oil-rich coal, specifically relating to a system and method for in-situ pyrolysis of oil-rich coal coupled with combustion in a lean coal boiler. Background Technology

[0002] With the deepening of my country's energy endowment characteristics of "abundant coal, scarce oil, and limited gas," the high dependence on imported oil and gas resources has made the clean and efficient conversion of coal and its substitution for oil and gas a strategic choice to ensure national energy security. Oil-rich coal, as a special type of coal resource, has a high tar yield, and gaseous fuels can be extracted through pyrolysis, making it an ideal substitute raw material to fill the oil and gas resource gap. However, the mining and processing of oil-rich coal faces severe challenges: on the one hand, traditional underground mining of deep or structurally complex oil-rich coal seams is costly and carries significant safety risks; on the other hand, conventional surface pyrolysis processes suffer from high water consumption and difficulties in processing semi-coke, hindering its resource utilization.

[0003] Meanwhile, many lean coal boilers in my country's existing coal-fired power units suffer from poor low-load combustion stability and high oil consumption due to low volatile matter content, high ignition temperature, and difficult burnout. Especially with the rapid increase in the penetration rate of new energy sources, boilers require frequent deep peak shaving, further exacerbating the difficulty of stable combustion of lean coal. If oil-rich coal, which is difficult to mine, can be directly converted into high-quality pyrolysis gas and tar through in-situ (underground) pyrolysis technology, leaving semi-coke, it can not only avoid the mining difficulties under complex geological conditions and achieve in-situ upgrading of underground resources, but also introduce the high-calorific-value gaseous products generated by pyrolysis into lean coal boilers for co-firing, utilizing their high methane and hydrogen content to enhance the ignition and burnout performance of lean coal.

[0004] Therefore, developing a system that couples in-situ pyrolysis of oil-rich coal with combustion in lean coal boilers has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The embodiments of the present invention aim to at least solve one of the technical problems existing in the prior art, and provide a system and method for in-situ pyrolysis coupling of oil-rich coal with lean coal combustion in a boiler.

[0006] An embodiment of the first aspect of the present invention provides a system for in-situ pyrolysis of oil-rich coal coupled with combustion of lean coal in a boiler, comprising: an in-situ pyrolysis subsystem for oil-rich coal and a boiler subsystem; The oil-rich coal in-situ pyrolysis subsystem includes a gas mixer, the outlet of which is connected to the inlet of the injection well. The boiler subsystem includes a boiler and a turbine unit. The gas mixer is used to mix the flue gas discharged from the boiler and the steam extracted from the turbine unit. The extraction well is used to supply the combustible gas generated from the in-situ pyrolysis of oil-rich coal to the boiler.

[0007] In some embodiments of the present invention, the oil-rich coal in-situ pyrolysis subsystem further includes: An oil-gas separator, wherein the oil-gas inlet of the oil-gas separator is connected to the outlet of the extraction well, and the gas outlet of the oil-gas separator is connected to the gas nozzle of the boiler.

[0008] In some embodiments of the present invention, the oil-rich coal in-situ pyrolysis subsystem further includes: A tar storage tank, wherein the tar inlet of the tar storage tank is connected to the tar outlet of the oil-gas separator.

[0009] In some embodiments of the present invention, the gas nozzle includes a front arch combustible gas nozzle and a rear arch combustible gas nozzle; The front arch combustible gas nozzle is located in the front arch of the boiler, and the rear arch combustible gas nozzle is located in the rear arch of the boiler. The front arch combustible gas nozzle and the rear arch combustible gas nozzle are respectively connected to the gas outlet of the oil-gas separator.

[0010] In some embodiments of the present invention, the boiler subsystem further includes a dust collector; The inlet of the dust collector is connected to the flue gas outlet of the boiler, and the outlet of the dust collector is directly or indirectly connected to the inlet of the gas mixer.

[0011] In some embodiments of the present invention, the boiler subsystem further includes a flue gas storage device; The inlet of the flue gas storage device is connected to the outlet of the dust collector, and the outlet of the flue gas storage device is connected to the gas inlet of the gas mixer. The flue gas storage device is used to store the high-temperature flue gas discharged from the boiler.

[0012] In some embodiments of the present invention, the boiler subsystem further includes an induced draft fan and a chimney; The inlet of the induced draft fan is connected to the outlet of the dust collector, and the outlet of the induced draft fan is connected to the chimney.

[0013] A second aspect of the present invention provides a method for in-situ pyrolysis coupling of oil-rich coal with lean coal combustion in a boiler, the method being implemented according to the system for in-situ pyrolysis coupling of oil-rich coal with lean coal combustion described in any of the above embodiments, the method comprising: The flue gas generated by the boiler combustion and the extracted steam from the steam turbine unit are mixed in the gas mixer to form a mixed gas; The mixed gas is fed into the injection well to perform in-situ pyrolysis of oil-rich coal; The combustible gas obtained from the in-situ pyrolysis of oil-rich coal is fed into the boiler for combustion.

[0014] In some embodiments of the present invention, the method further includes: Oil and gas mixtures are extracted from the wells and separated into combustible gas and tar. The tar is stored in a tar storage tank.

[0015] In some embodiments of the present invention, the method further includes: The flue gas generated by the boiler combustion is subjected to dust removal treatment.

[0016] This invention relates to a system and method for in-situ pyrolysis of rich oil coal coupled with lean coal boiler combustion. In this system, the high-temperature flue gas generated after combustion in the boiler subsystem and the extraction steam from the turbine unit are both transported to a gas mixer in the rich oil coal in-situ pyrolysis subsystem for mixing. The resulting gas mixture is then fed into an injection well, where it in-situ pyrolyzes the rich oil coal to generate a mixture of combustible gas and tar. This mixture is extracted from the extraction well, and the combustible gas is transported to the boiler as supplementary fuel for combustion, thus improving the combustion stability of the lean coal boiler. By using a mixture of high-temperature flue gas and high-temperature extraction steam to in-situ pyrolyze the rich oil coal, the extraction efficiency of the rich oil coal in-situ pyrolysis can be improved. The heat generated by the combustion of the combustible gas produced from the pyrolysis of the rich oil coal aids in the combustion of the lean coal, thereby improving the combustion efficiency and stability of the lean coal boiler. Attached Figure Description

[0017] Figure 1 This is an overall assembly diagram of a system for in-situ pyrolysis coupling lean coal boiler combustion according to an embodiment of the present invention.

[0018] The labels in the attached diagram are as follows: 1. Gas mixer; 2. Injection well; 3. Extraction well; 4. Oil-gas separator; 5. Tar storage tank; 6. Front arch combustible gas nozzle; 7. Rear arch combustible gas nozzle; 8. Air preheater; 9. Dust collector; 10. Flue gas storage tank; 11. Exhaust fan; 12. Chimney; 13. Boiler. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit disclosure. The described embodiments are some, but not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0020] With the deepening of my country's energy endowment characteristics of "abundant coal, scarce oil, and limited gas," the high dependence on imported oil and gas resources has made the clean and efficient conversion of coal and its substitution for oil and gas a strategic choice to ensure national energy security. Oil-rich coal, as a special type of coal resource, has a high tar yield, and gaseous fuels can be extracted through pyrolysis, making it an ideal substitute raw material to fill the oil and gas resource gap. However, the mining and processing of oil-rich coal faces severe challenges: on the one hand, traditional underground mining of deep or structurally complex oil-rich coal seams is costly and carries significant safety risks; on the other hand, conventional surface pyrolysis processes suffer from high water consumption and difficulties in processing semi-coke, hindering its resource utilization.

[0021] Meanwhile, many lean coal boilers in my country's existing coal-fired power units suffer from poor low-load combustion stability and high oil consumption due to low volatile matter content, high ignition temperature, and difficult burnout. Especially with the rapid increase in the penetration rate of new energy sources, boilers require frequent deep peak shaving, further exacerbating the difficulty of stable combustion of lean coal. If oil-rich coal, which is difficult to mine, can be directly converted into high-quality pyrolysis gas and tar through in-situ (underground) pyrolysis technology, leaving semi-coke, it can not only avoid the mining difficulties under complex geological conditions and achieve in-situ upgrading of underground resources, but also introduce the high-calorific-value gaseous products generated by pyrolysis into lean coal boilers for co-firing, utilizing their high methane and hydrogen content to enhance the ignition and burnout performance of lean coal.

[0022] Therefore, developing a system that couples in-situ pyrolysis of rich oil-bearing coal with combustion in lean coal boilers can replace traditional mining with underground pyrolysis, breaking the deadlock in the development of rich oil-bearing coal. Simultaneously, using pyrolysis gas as a high-quality combustion-supporting fuel for lean coal boilers can replace some of the oil used for combustion, improving low-load stable combustion capabilities while supplementing oil and gas resources. This technological approach aligns with the industrial orientation of green development of rich oil-bearing coal and provides a self-produced clean gaseous fuel source for the flexible retrofitting of existing lean coal units, which is of significant practical importance for reducing dependence on oil and gas imports and promoting the graded utilization of coal.

[0023] like Figure 1 As shown, an embodiment of the first aspect of the present invention provides a system for in-situ pyrolysis of oil-rich coal coupled with combustion in a lean coal boiler, comprising: an in-situ pyrolysis subsystem for oil-rich coal and a boiler subsystem; The in-situ pyrolysis subsystem for oil-rich coal includes a gas mixer 1, the outlet of which is connected to the inlet of the injection well 2. The boiler subsystem includes boiler 13 and turbine unit (not shown in the figure). Gas mixer 1 is used to mix the flue gas discharged from boiler 13 and the steam extracted from turbine unit. Extraction well 3 is used to supply combustible gas generated from in-situ pyrolysis of oil-rich coal to boiler 13.

[0024] The system of in-situ pyrolysis of rich oil coal coupled with combustion of lean coal boiler according to an embodiment of the present invention includes a rich oil coal in-situ pyrolysis subsystem and a boiler subsystem. Specifically, the high-temperature flue gas generated after combustion in the boiler 13 of the boiler subsystem and the steam extracted from the turbine unit are both transported to the gas mixer 1 of the rich oil coal in-situ pyrolysis subsystem for mixing. The mixed flue gas and steam gas mixture is sent into the injection well 2. The gas mixture pyrolyzes the rich oil coal in the injection well 2 in-situ to generate a mixture of combustible gas and tar. The mixture of combustible gas and tar is extracted from the extraction well 3, and the combustible gas in the mixture is transported to the boiler 13 and used as supplementary fuel for combustion in the boiler 13 to make the combustion of lean coal boiler 13 more stable. By performing in-situ pyrolysis of oil-rich coal using a mixture of high-temperature flue gas and high-temperature steam extraction, the extraction efficiency of in-situ pyrolysis of oil-rich coal can be improved. The heat generated by the combustion of combustible gas produced by pyrolysis of oil-rich coal can assist in the combustion of lean coal, thereby improving the combustion efficiency and stability of lean coal boiler 13.

[0025] In some embodiments of the present invention, the in-situ pyrolysis subsystem for rich oil-bearing coal further includes: an oil-gas separator 4, the oil-gas inlet of which is connected to the outlet of the extraction well 3, and the gas outlet of the oil-gas separator 4 connected to the gas injection port of the boiler 13. Specifically, a mixture of high-temperature flue gas and extracted steam is fed into the injection well 2, where the gas mixture pyrolyzes the rich oil-bearing coal in the injection well 2 in situ to generate a mixture of combustible gas and tar, which is then extracted from the extraction well 3. The mixture of combustible gas and tar extracted from the extraction well 3 undergoes oil-gas separation in the oil-gas separator 4 to separate the combustible gas and tar. The combustible gas is then transported to the gas injection port of the boiler 13 and enters the boiler 13 for combustion.

[0026] In some embodiments of the present invention, the in-situ pyrolysis subsystem for oil-rich coal further includes a tar storage tank 5, the tar inlet of which is connected to the tar outlet of the oil-gas separator 4. Specifically, the tar separated by the oil-gas separator 4 is discharged through the tar outlet of the oil-gas separator 4 and enters the tar storage tank 5 through the tar inlet, where the tar is stored in the oil storage tank.

[0027] In some embodiments of the present invention, the gas nozzle includes a front arch combustible gas nozzle 6 and a rear arch combustible gas nozzle 7. The front arch combustible gas nozzle 6 and the rear arch combustible gas nozzle 7 are respectively connected to the gas outlet of the oil-gas separator 4. The front arch combustible gas nozzle 6 is located in the front arch of the boiler 13, and the rear arch combustible gas nozzle 7 is located in the rear arch of the boiler 13. Specifically, by setting gas nozzles in the front arch and rear arch of the boiler 13 respectively, lean coal can be effectively aided in combustion, and the uniformity of combustion in the furnace can be improved.

[0028] In some embodiments of the present invention, the boiler subsystem further includes an air preheater 8, which is disposed within the flue of the boiler 13 and is located near the outlet of the flue. The air preheater 8 absorbs heat from the high-temperature flue gas flowing through the flue and releases the heat to the air supplied to the boiler 13, thereby increasing the temperature of the air entering the boiler 13 and improving the combustion efficiency of the boiler 13.

[0029] In some embodiments of the present invention, the boiler subsystem further includes a dust collector 9; the inlet of the dust collector 9 is connected to the flue gas outlet of the boiler 13, and the outlet of the dust collector 9 is directly or indirectly connected to the inlet of the gas mixer 1. Specifically, a dust collector 9 is provided at the flue gas outlet of the boiler 13. The high-temperature flue gas generated by the combustion of the boiler 13 flows through the flue and is discharged into the dust collector 9 through the flue gas outlet of the flue. The dust collector 9 performs dust removal treatment on the flue gas. A portion of the dust-removed flue gas is discharged into the atmosphere, and the other portion of the dust-removed flue gas is transported into the gas mixer 1.

[0030] In some embodiments of the present invention, the boiler subsystem further includes a flue gas storage tank 10; the inlet of the flue gas storage tank 10 is connected to the outlet of the dust collector 9, and the outlet of the flue gas storage tank 10 is connected to the gas inlet of the gas mixer 1. The flue gas storage tank 10 is used to store the high-temperature flue gas discharged from the boiler 13. Specifically, the flue gas storage tank 10 is disposed between the dust collector 9 and the gas mixer 1. After the flue gas is treated by dust removal in the dust collector 9, a portion is transported to the flue gas storage tank 10 for storage, so that the flue gas can be transported to the gas mixer 1 according to the pyrolysis requirements of the rich oil coal. By setting up the flue gas storage tank 10, the flue gas can be temporarily stored. When the lean coal boiler 13 needs combustible gas as supplementary fuel for combustion, the flue gas in the flue gas storage tank 10 is transported to the gas mixer 1 to be mixed with high-temperature extraction steam, and then the mixed gas is used to pyrolyze the rich oil coal.

[0031] In some embodiments of the present invention, the boiler subsystem further includes an induced draft fan 11 and a chimney 12; the inlet of the induced draft fan 11 is connected to the outlet of the dust collector 9, and the outlet of the induced draft fan 11 is connected to the chimney 12. Specifically, a portion of the flue gas after dust removal by the dust collector 9 is introduced into the chimney 12 through the induced draft fan 11 and discharged into the atmosphere through the chimney 12.

[0032] The working principle of the system of in-situ pyrolysis coupled with lean coal boiler combustion of the present invention: The high-temperature flue gas generated by the combustion of boiler 13 is mixed with the high-temperature extraction steam of the turbine unit in the gas mixer 1. The mixed flue gas and extraction steam gas mixture is sent into injection well 2. The gas mixture pyrolyzes the oil-rich coal in injection well 2 in situ to generate a mixture of combustible gas and tar. The mixture of combustible gas and tar is extracted from extraction well 3 and transported to oil-gas separator 4. Oil-gas separator 4 separates combustible gas and tar. The tar is stored in the fuel storage tank. The combustible gas is transported to boiler 13 through front arch combustible gas nozzle 6 and rear arch combustible gas nozzle 7 as supplementary fuel for combustion in boiler 13. The high-temperature flue gas generated by the combustion of lean coal and combustible gas in boiler 13 flows through its flue and transfers some of the heat to air preheater 8. The high-temperature flue gas is discharged to dust collector 9 through the flue gas outlet of the flue. Dust collector 9 removes dust from the high-temperature flue gas. A portion of the flue gas after dust removal is introduced into chimney 12 by induced draft fan 11 and discharged into the atmosphere. The other portion of the flue gas after dust removal is stored in flue gas storage tank 10. When it is necessary to pyrolyze oil-rich coal, the flue gas in flue gas storage tank 10 is transported to gas mixer 1 and mixed with the steam extracted from the steam turbine unit.

[0033] The key point of this invention is that by using the combustible gas generated from the in-situ pyrolysis of oil-rich coal to aid the combustion of lean coal in a lean coal boiler, the combustion efficiency of lean coal can be improved.

[0034] The key point of this invention is that combustible gas nozzles are arranged in both the front and rear arches of the lean coal boiler, which can effectively aid the combustion of lean coal and improve the uniformity of combustion in the furnace.

[0035] The key point of this invention is that by using the high-pressure cylinder of the steam turbine to extract steam and mix it with flue gas, the injected gas contains N2, CO2 and high-temperature water vapor, which can improve the efficiency of in-situ pyrolysis of oil-rich coal.

[0036] The key point of this invention is that the coupling of the oil-rich coal in-situ pyrolysis subsystem and the boiler subsystem can simultaneously produce industrial products such as tar, electricity, and steam, thus realizing chemical polygeneration.

[0037] A second aspect of the present invention provides a method for in-situ pyrolysis coupling of oil-rich coal with lean coal combustion in a boiler. The method is implemented according to the system implementation of in-situ pyrolysis coupling of oil-rich coal with lean coal combustion in any of the above embodiments, and includes: S100: The flue gas generated by boiler combustion is mixed with the extracted steam from the turbine unit in a gas mixer to form a mixed gas; S200: Injection well for in-situ pyrolysis of oil-rich coal; S300: The combustible gas obtained from the in-situ pyrolysis of oil-rich coal is sent into the boiler for combustion.

[0038] This invention discloses a method for in-situ pyrolysis of rich oil-bearing coal coupled with combustion in a lean coal boiler. First, the flue gas generated from boiler combustion is mixed with extraction steam from a turbine unit in a gas mixer to form a mixed gas. Then, the mixed gas is sent to an injection well for in-situ pyrolysis of the rich oil-bearing coal. Finally, the combustible gas produced from the in-situ pyrolysis of the rich oil-bearing coal is sent into the boiler for combustion. By using a mixture of high-temperature flue gas and high-temperature extraction steam to perform in-situ pyrolysis of the rich oil-bearing coal, the extraction efficiency of the in-situ pyrolysis of the rich oil-bearing coal can be improved. Furthermore, the heat generated from the combustion of the combustible gas produced by the pyrolysis of the rich oil-bearing coal aids in the combustion of the lean coal, thereby improving the combustion efficiency and stability of the lean coal boiler.

[0039] In some embodiments of the present invention, the method further includes: Oil and gas mixtures are extracted from the wells and separated into combustible gas and tar. The tar is stored in tar storage tanks.

[0040] Specifically, after S200 and before S300, oil and gas mixture is extracted from the extraction well, and then separated into combustible gas and tar by an oil and gas separator. The tar is stored in a tar storage tank, and the combustible gas is transported to the boiler.

[0041] In some embodiments of the present invention, the method further includes: Dust removal treatment is performed on the flue gas generated by boiler combustion.

[0042] Specifically, before the flue gas generated by boiler combustion is conveyed to the gas mixer, the flue gas is treated with dust removal. The flue gas after dust removal is stored in a flue gas storage tank. According to the pyrolysis requirements, the flue gas in the flue gas storage tank is conveyed to the gas mixer.

[0043] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A system for in-situ pyrolysis of oil-rich coal coupled with combustion of lean coal in a boiler, characterized in that, include: Oil-rich coal in-situ pyrolysis subsystem and boiler subsystem; The oil-rich coal in-situ pyrolysis subsystem includes a gas mixer, the outlet of which is connected to the inlet of the injection well. The boiler subsystem includes a boiler and a turbine unit. The gas mixer is used to mix the flue gas discharged from the boiler and the steam extracted from the turbine unit. The extraction well is used to supply the combustible gas generated from the in-situ pyrolysis of oil-rich coal to the boiler.

2. The system for in situ pyrolysis of oil-rich coal coupled with combustion of lean coal in a boiler according to claim 1, characterized in that, The oil-rich coal in-situ pyrolysis subsystem also includes: An oil-gas separator, wherein the oil-gas inlet of the oil-gas separator is connected to the outlet of the extraction well, and the gas outlet of the oil-gas separator is connected to the gas injection port of the boiler.

3. The system for in situ pyrolysis of oil-rich coal coupled with lean coal boiler combustion according to claim 2, characterized in that, The oil-rich coal in-situ pyrolysis subsystem also includes: A tar storage tank, wherein the tar inlet of the tar storage tank is connected to the tar outlet of the oil-gas separator.

4. The system for in situ pyrolysis of oil-rich coal coupled with combustion of lean coal in a boiler according to claim 2, characterized in that, The gas nozzle includes a front arch combustible gas nozzle and a rear arch combustible gas nozzle; The front arch combustible gas nozzle is located in the front arch of the boiler, and the rear arch combustible gas nozzle is located in the rear arch of the boiler. The front arch combustible gas nozzle and the rear arch combustible gas nozzle are respectively connected to the gas outlet of the oil-gas separator.

5. The system for in situ pyrolysis of oil-rich coal coupled with lean coal boiler combustion according to claim 1, characterized in that, The boiler subsystem also includes a dust collector; The inlet of the dust collector is connected to the flue gas outlet of the boiler, and the outlet of the dust collector is directly or indirectly connected to the inlet of the gas mixer.

6. The system for in situ pyrolysis of oil-rich coal coupled with lean coal boiler combustion according to claim 5, characterized in that, The boiler subsystem also includes a flue gas storage unit; The inlet of the flue gas storage device is connected to the outlet of the dust collector, and the outlet of the flue gas storage device is connected to the gas inlet of the gas mixer. The flue gas storage device is used to store the high-temperature flue gas discharged from the boiler.

7. The system for in-situ pyrolysis coupled with lean coal boiler combustion according to claim 5, characterized in that, The boiler subsystem also includes an induced draft fan and a chimney; The inlet of the induced draft fan is connected to the outlet of the dust collector, and the outlet of the induced draft fan is connected to the chimney.

8. A method for in-situ pyrolysis of oil-rich coal coupled with combustion of lean coal in a boiler, the method being a systematic implementation according to any one of claims 1 to 7, characterized in that... The method includes: The flue gas generated by the boiler combustion and the extracted steam from the steam turbine unit are mixed in the gas mixer to form a mixed gas; The mixed gas is fed into the injection well to perform in-situ pyrolysis of oil-rich coal; The combustible gas obtained from the in-situ pyrolysis of oil-rich coal is fed into the boiler for combustion.

9. The method for in-situ pyrolysis coupled with lean coal boiler combustion according to claim 8, characterized in that, The method further includes: Oil and gas mixtures are extracted from the wells and separated into combustible gas and tar. The tar is stored in a tar storage tank.

10. The method for in-situ pyrolysis coupled with lean coal combustion in a boiler according to claim 8, characterized in that, The method further includes: The flue gas generated by the boiler combustion is subjected to dust removal treatment.

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