A system and method for producing carbon dioxide and generating power using coal gasification product gas

Abstract

The application discloses a kind of carbon dioxide and power generation system and method for preparing by coal gasification output gas, belong to unconventional coal underground gasification technical field, the system includes dust removal and water removal module, product separation module, power generation module;The dust removal and water removal module includes production well, underground dust removal cavity, wellhead device and dust removal and water removal device, the product separation module includes compressor, acid gas separation device, sedimentation cavity and N2 separation device, the power generation module includes annulus, thermoelectric generator and heating device.The system and method of the application fully recover the heat energy and kinetic energy of the crude coal gas itself, the separated CO2 is further compressed using the kinetic energy of the crude coal gas and used as a refrigerant or as a byproduct, reducing project costs, increasing byproduct income, while avoiding greenhouse gas emissions.

Description

Technical Field

[0001] This invention belongs to the field of unconventional underground coal gasification technology, specifically relating to a system and method for producing carbon dioxide and generating electricity using coal gasification output gas. Background Technology

[0002] Underground coal gasification technology is a novel green coal mining technology that integrates shaft construction, coal mining, and gasification processes, providing a new approach to the development of coal chemical industry. The combustion zone temperature in the underground coal gasification chamber reaches as high as 1000℃, while the production shaft temperature is around 800℃. Furthermore, the shaft contains crude coal gas with multiple components, including hydrogen, carbon dioxide, carbon monoxide, and methane. To lower the shaft temperature, a spray cooling process is employed within the production shaft. After spray cooling, the temperature of the underground coal gas produced is between 300℃ and 450℃, the wellhead pressure is between 12MPa and 25MPa, and the flow rate is 100,000 cubic meters per day.

[0003] The gas produced by underground coal gasification technology contains byproducts such as CO2, H2S, and water vapor. How to efficiently and conveniently separate and utilize these byproducts to improve economic benefits will be an important research direction.

[0004] Chinese patent publication CN106121616A discloses a gas purification and separation technology based on underground coal gasification, which solves the problem of separating the components of the produced gas. The method involves compressing the initially purified gas, then cooling and separating it at low temperature. The liquid separated at low temperature is then physically adsorbed to obtain CO2. The gas after physical adsorption undergoes cryogenic separation, followed by distillation to obtain liquid CH4 and gaseous H2 and CO. However, this method requires multiple compression, cooling, and distillation operations, resulting in high energy consumption and making it difficult to meet economic requirements. Furthermore, this method only performs heat exchange treatment on the crude coal gas, leading to high energy loss.

[0005] Chinese patent publication CN107013201A discloses a method for generating electricity using coal gasification products. The method involves transporting crude syngas to the surface through a production well, and obtaining dry syngas through cooling, washing, and separation units. The dry syngas is then directly transported to a combustion unit and a mechanical coupling unit for power generation. This method fails to practically consider the actual needs of underground coal gasification projects, directly burning and utilizing the refined coal gas. The thermal and kinetic energy of the crude coal gas itself is not utilized. Furthermore, the utilization and collection of the large amount of CO2 in the crude coal gas are not considered, resulting in economic losses and greenhouse gas emissions.

[0006] The main problems with the existing technology are as follows: (1) The supporting facilities above ground for underground coal gasification technology are not yet perfect, and the thermal and kinetic energy of the syngas cannot be effectively utilized, resulting in energy waste. (2) The treatment of CO2 is limited to separation and absorption, without utilization, and the economic benefits of CO2 are not reflected. (3) The existing gas separation and purification process is complex and energy-intensive, which increases the overall cost. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention aims to provide a system and method for producing carbon dioxide and generating electricity using coal gasification. The method fully recovers the thermal and kinetic energy of the crude coal gas itself. The separated CO2 is further compressed using the kinetic energy of the crude coal gas and used as a refrigerant or as a by-product. The system and method reduce project costs, increase by-product revenue, and avoid greenhouse gas emissions.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] This invention provides a system for producing carbon dioxide and generating electricity using coal gasification product gas, including a dust removal and water removal module, a product separation module, and a power generation module;

[0010] The dust removal and water removal module includes a production well, an underground dust removal chamber, a wellhead device, and a dust removal and water removal device. The underground dust removal chamber is located at the bottom of the production well; the wellhead device is located at the top of the production well; and the wellhead device is connected to the air inlet of the dust removal and water removal device.

[0011] The dust removal and water removal device is connected to the product separation module. The product separation module includes a compressor, an acid gas separation device, a sedimentation chamber, and an N2 separation device. The first air inlet of the compressor is connected to the air outlet of the dust removal and water removal device, the air outlet of the compressor is connected to the air inlet of the acid gas separation device, the air inlet of the sedimentation chamber is connected to the first air outlet of the acid gas separation device, the air outlet of the sedimentation chamber is connected to the second air inlet of the compressor, and the N2 separation device is connected to the second air outlet of the acid gas separation device.

[0012] The production well is connected to the power generation module, which includes an annulus, a thermoelectric generator, and a heating device. The annulus is connected in sequence to the thermoelectric generator and the heating device, and the outlet of the heating device is connected to the room temperature inlet of the annulus.

[0013] Furthermore, the lower edge of the underground dust removal chamber has an inclination angle of 15-30°, and the depth of the underground dust removal chamber is 5-15m.

[0014] In a further aspect of the present invention, the outlet of the sedimentation chamber is connected to the inlet of the dust removal and water removal device.

[0015] Furthermore, the N2 separation device is connected to a gas injection well.

[0016] Furthermore, in this invention, the acidic gas separation device uses diethanolamine for chemical adsorption and separation.

[0017] Furthermore, the dust removal and water removal device uses H2SO4 solution for water removal.

[0018] In a further step of the present invention, the precipitation chamber is used for separation using Cu2SO4 solution.

[0019] This invention provides a method for producing carbon dioxide and power generation using coal gasification gas, comprising the following steps:

[0020] Coal undergoes an oxidation-reduction reaction in the gasification chamber to produce crude coal gas. The crude coal gas flows through an underground dust removal chamber, a production well, a wellhead device, and a dust and water removal device to remove dust and water, resulting in dry coal gas.

[0021] The dry coal gas enters the compressor, driving the compressor to work, and then enters the acid gas separation device for chemical adsorption and separation to obtain acid gas and combustible gas; the acid gas enters the precipitation chamber to obtain gaseous CO2; the gaseous CO2 enters the compressor for compression to obtain liquid CO2; the combustible gas enters the N2 separation device to separate N2, obtaining methane gas and N2;

[0022] The thermal energy of the crude coal gas is transferred to the annulus via the production well; room temperature water is injected into the room temperature water inlet of the annulus, and the room temperature water is vaporized into water vapor; the water vapor drives the thermoelectric generator to work, generate electricity and condense into high temperature water, and then the high temperature water enters the heating device to exchange heat with the environment for heating.

[0023] In a further step of the present invention, the high-temperature water is cooled to room temperature water in the heating device and then injected into the annulus for recycling.

[0024] Furthermore, in this invention, the N2 enters the injection well as a protective gas circulation.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention provides a system for producing carbon dioxide and generating electricity using coal gasification products. It utilizes the high temperature, high speed, and high pressure characteristics of the raw coal gas itself to generate electricity. Heat energy is extracted at the bottom of the well and combined with a surface thermoelectric generator to generate electricity through a power generation module, fully utilizing the thermal and kinetic energy of the raw coal gas. The product separation module simplifies the separation process and also yields byproducts, reducing emissions of harmful and greenhouse gases. It eliminates the need for depressurization and cooling of the syngas, minimizing formation energy loss, lowering coalfield production costs, and improving overall economic efficiency.

[0027] Furthermore, the present invention allows the underground dust removal chamber to remove dust and impurities from the crude coal gas by relying on the gravity of the solid impurities themselves. The solid particles will be sealed at the bottom of the well without additional treatment, thus avoiding environmental pollution. At the same time, since the temperature inside the coal gasification production well is too high, water injection is often required to cool it down during production. The underground dust removal chamber can store the water accumulated at the bottom of the well, preventing water from flowing back into the gasification chamber and causing the entire well to be scrapped.

[0028] Furthermore, the compressor can be driven by high-speed and high-pressure dry coal gas, which further utilizes the energy of the strata and improves the resource utilization rate.

[0029] Furthermore, when H2S is precipitated using Cu2SO4 solution, the generated byproduct H2SO4 can be used to further remove dust and impurities from the crude coal gas, while simultaneously cooling and removing water from the crude coal gas. This fully utilizes the economic benefits of the byproduct and reduces the process steps.

[0030] This invention provides a working method for a coal gasification gasification and power generation system, which fully recovers the thermal and kinetic energy of the raw coal gas itself. The separated CO2 is further compressed using the kinetic energy of the raw coal gas and used as a refrigerant or as a by-product. This reduces project costs, increases by-product revenue, and avoids greenhouse gas emissions. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of the present invention.

[0032] Wherein: 1-Raw coal gas; 2-Production well; 3-Solid particulate impurities; 4-Downhole dust removal chamber; 5-Wellhead device; 6-Thermal energy; 7-Annulus; 8-Room temperature water; 9-Water vapor; 10-Thermoelectric generator; 11-Electric energy; 12-High temperature water; 13-Heating device; 14-Dust and water removal device; 15-Dry coal gas; 16-Compressor; 17-Acid gas separation device; 18-Acid gas; 19-Combustible gas; 20-Sedimentation chamber; 21-Gaseous CO2; 22-Liquid CO2; 23-H2SO4; 24-CuS; 25-N2 separation device; 26-Methane gas; 27-N2; 28-Injection well. Detailed Implementation

[0033] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0034] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0035] This invention provides a system and method for producing carbon dioxide and generating electricity using coal gasification gas.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] A system for producing carbon dioxide and generating electricity using coal gasification gas includes a dust removal and water removal module, a product separation module, and a power generation module.

[0038] The dust removal and water removal module includes a production well 2, an underground dust removal chamber 4, a wellhead device 5, and a dust removal and water removal device 14. The underground dust removal chamber 4 is located at the bottom of the production well 2; the wellhead device 5 is located at the top of the production well 2; and the wellhead device 5 is connected to the air inlet of the dust removal and water removal device 14.

[0039] The dust removal and water removal device 14 is connected to the product separation module, which includes a compressor 16, an acid gas separation device 17, a sedimentation chamber 20, and an N2 separation device 25.

[0040] The first air inlet of the compressor 16 is connected to the air outlet of the dust removal and water removal device 14, the air outlet of the compressor 16 is connected to the air inlet of the acid gas separation device 17, the air inlet of the sedimentation chamber 20 is connected to the first air outlet of the acid gas separation device 17, and the air outlet of the sedimentation chamber 20 is connected to the second air inlet of the compressor 16; the water outlet of the sedimentation chamber 20 is connected to the water inlet of the dust removal and water removal device 14; the sedimentation chamber 20 is provided with a third outlet, which is the outlet for the by-product CuS24; the air inlet of the N2 separation device 25 is connected to the second air outlet of the acid gas separation device 17; the compressor 16 also includes a water outlet; the first air outlet of the N2 separation device 25 is connected to the gas injection well 28; the N2 separation device 25 is provided with a second air outlet, which is the outlet for the by-product methane gas 28.

[0041] The production well 2 of the dust removal and water removal module is connected to the power generation module. The power generation module includes an annulus 7, a thermoelectric generator 10, and a heating device 13. The annulus 7 is connected in sequence to the thermoelectric generator 10 and the heating device 13. The outlet of the heating device 13 is connected to the room temperature water inlet of the annulus 7.

[0042] A method for using coal gasification gas to produce carbon dioxide and a power generation system includes the following steps:

[0043] a. When the crude coal gas 1 flows through the production well 2 to the wellhead device 5, most of the solid particulate impurities 3 fall into the underground dust removal chamber 4 due to inertia in the production well 2, and the crude coal gas 1 is subjected to the first dust removal.

[0044] In step a, the downhole dust removal chamber 4 is established during drilling. When the production well is drilled to the target layer, it continues to drill downwards at a certain angle to a certain depth. When the synthesis gas flows through the production well wall, due to inertia, most of the solid impurities will fall into the downhole dust removal chamber, thereby performing the initial dust removal on the crude coal gas 1.

[0045] The lower edge of the underground dust removal chamber 4 has an inclination angle of 15 to 30°, and the depth of the underground dust removal chamber 4 is 5 to 15 m.

[0046] In step a, when the crude coal gas 1 enters the wellhead device 5, its components are CO, CO2, H2, CH4, H2S, water vapor, and solid impurities.

[0047] b. The crude coal gas 1 produced by the wellhead device 5 first enters the dust removal and dehydration device 14 for dust removal and dehydration treatment, obtaining dry coal gas 15 free of solid particulate impurities 3 and moisture. The dry coal gas 15 is driven by its own high pressure and high speed to operate the compressor 16. Then, the dry coal gas 15 enters the acid gas separation device 17 and is separated into two parts of gas. One part of the gas is acid gas 18, and the other part is combustible gas 19.

[0048] In step b, the acid gas 18 is composed of CO2 and H2S, and the combustible gas 19 contains N2.

[0049] In step b, the dust removal and dehydration device 14 utilizes the water absorption property of H2SO4 solution to remove water and dust from the syngas, forming dust-free dry coal gas 15.

[0050] In step b, the acid gas separation device 17 uses diethanolamine to chemically adsorb and separate CO2 and H2S. The chemical reaction formula is as follows:

[0051]

[0052] c. The acidic gas 18 separated by the acidic gas separator 17 then enters the precipitation chamber 20 and reacts with H2S and CuSO4 to separate gaseous CO221. The separated gaseous CO221 enters the compression chamber of the compressor 16 and is compressed and liquefied into liquid CO222.

[0053] In step c, the precipitation chamber 20 uses the chemical reaction between Cu2SO4 solution and H2S to separate CO2 and H2S.

[0054] Because CO2 is a weak acid, it will not react with Cu2SO4 and H2SO4. H2S reacts with Cu2SO4 to produce CuS and H2SO4. The chemical reaction equation is as follows:

[0055] H₂S↑ + CuSO₄ = CuS↓ + H₂SO₄

[0056] The byproduct H2SO423 enters the dust removal and dehydration unit 14 to treat the crude coal gas 1 for dust removal and dehydration. The byproduct CuS24 can be further processed or sold.

[0057] d. The combustible gas 19 obtained by the acid gas separation device 17 then enters the N2 separation device 25 to separate N227, and finally obtains methane gas 26, the final underground coal gasification product. The composition of methane gas 26 is CH4, CO and H2.

[0058] The byproduct N227 enters injection well 28 and is used as protective gas in the circulation.

[0059] e. When the crude gas 1 flows through the production well 2, a large amount of heat energy 6 in the production well 2 is transferred to the annulus 7; room temperature water 8 is injected from the annulus 7 and vaporized into water vapor 9 to drive the thermoelectric generator 10 to generate electricity 11.

[0060] f. Water vapor 9 is condensed into high-temperature water 12 after passing through the thermoelectric generator 10. The high-temperature water 12 then enters the heating device 13 to exchange heat with the environment for heating. After the high-temperature water 12 is cooled to room temperature water 8, it is injected into the annulus 7 for recycling.

[0061] Example

[0062] Dust and water removal module: After coal undergoes an oxidation-reduction reaction in the gasification chamber, it generates crude coal gas 1. As crude coal gas 1 flows through the bottom of production well 2, most of the solid particulate impurities 3 in it enter the dust removal chamber 4 due to inertia. At this point, the temperature at the bottom of production well 2 reaches approximately 900℃. Subsequently, crude coal gas 1 enters the wellhead device 5 through the shaft of production well 2. The temperature at the wellhead of device 5 is between 300℃ and 450℃. After flowing through wellhead device 5, crude coal gas 1 enters the dust and water removal device 14 for dust and water removal. The dust and water removal device 14 mainly utilizes the hygroscopic property of H2SO4 to absorb water vapor in the crude coal gas. Simultaneously, the solid particulate impurities 3 settle to the bottom of the dust and water removal device 14 under inertia. The resulting dry coal gas 15, after dust and water removal, flows out through the outlet at the top of the dust and water removal device 14.

[0063] Product separation module: At this time, the temperature of dry coal gas 15 is 100℃, and the pressure is between 3MPa and 7MPa. Dry coal gas 15 then enters the power chamber of compressor 16, where its own pressure drives the drive shaft of compressor 16, thus powering compressor 16. Simultaneously, while driving compressor 16, dry coal gas 15 reduces its own pressure, and then enters the acid gas separation device 17.

[0064] The acid gas separation device 17 uses diethanolamine to adsorb CO2 and H2S to obtain combustible gas 19 that does not contain acid gas 18. The combustible gas 19 further enters the N2 separation device 25 to separate N2 27, and obtains the final product methane gas 26. The by-product N2 27 can be reinjected into the injection well 28 as a protective gas for recycling.

[0065] The acidic gas 18 separated by the acidic gas separator 17 enters the precipitation chamber 20. The precipitation chamber 20 uses CuSO4 to convert H2S gas into CuS24 and H2SO423, obtaining pure gaseous CO221. The gaseous CO221 then enters the compression chamber of the compressor 16 for compression, obtaining liquid CO222. The liquid CO222 can be sold to improve economic efficiency.

[0066] The byproduct H2SO423 enters the dust removal and dehydration device 14 to remove dust and water from the crude coal gas 1. The byproduct CuS24 can be further refined to extract sulfur or sold as an upstream product in the inorganic industry.

[0067] Power generation module: The temperature inside the annulus 7 in production well 2 reaches approximately 400°C after heat conduction. Room temperature water 8 is injected into the annulus 7 and vaporizes into 300°C high-temperature steam 9. The high-temperature steam 9 drives the thermoelectric generator 10 to generate electricity 11. At the same time, the high-temperature steam 9 liquefies into approximately 70°C high-temperature water 12. Subsequently, the high-temperature water 12 enters the heating device 13 to heat the plant. After the temperature of the high-temperature water 12 drops to room temperature, it is injected back into the annulus 7 for reuse.

[0068] The present invention discloses a system and method for producing carbon dioxide and generating electricity using coal gasification products. It utilizes the high temperature, high speed and high pressure characteristics of crude coal gas to generate electricity, thereby reducing the emission of harmful gases and greenhouse gases. It eliminates the need for special depressurization and cooling operations on the syngas, reducing the loss of formation energy, lowering coalfield production costs and improving overall economic benefits.

[0069] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A system for producing carbon dioxide and generating electricity using coal gasification gas, characterized in that, Includes a dust removal and water removal module, a product separation module, and a power generation module; The dust removal and water removal module includes a production well (2), a downhole dust removal chamber (4), a wellhead device (5), and a dust removal and water removal device (14). The downhole dust removal chamber (4) is located at the bottom of the production well (2). The lower edge of the downhole dust removal chamber (4) has an inclination angle of 15~30° and a depth of 5~15m. The wellhead device (5) is located at the top of the production well (2). The wellhead device (5) is connected to the air inlet of the dust removal and water removal device (14). The dust removal and water removal device (14) is connected to the product separation module, which includes a compressor (16), an acid gas separation device (17), a sedimentation chamber (20), and an N2 separation device (25). The first air inlet of the compressor (16) is connected to the air outlet of the dust removal and water removal device (14), the air outlet of the compressor (16) is connected to the air inlet of the acid gas separation device (17), the air inlet of the sedimentation chamber (20) is connected to the first air outlet of the acid gas separation device (17), the air outlet of the sedimentation chamber (20) is connected to the second air inlet of the compressor (16), the water outlet of the sedimentation chamber (20) is connected to the water inlet of the dust removal and water removal device (14), the N2 separation device (25) is connected to the second air outlet of the acid gas separation device (17), and the N2 separation device (25) is connected to an injection well (28). The production well (2) is connected to the power generation module, which includes annulus (7), thermoelectric generator (10) and heating device (13). The annulus (7) is connected to the thermoelectric generator (10) and heating device (13) in sequence. The outlet of the heating device (13) is connected to the room temperature inlet of the annulus (7).

2. The system for producing carbon dioxide and generating electricity using coal gasification gas according to claim 1, characterized in that, The acid gas separation device (17) uses diethanolamine for chemical adsorption and separation.

3. The system for producing carbon dioxide and generating electricity using coal gasification gas according to claim 1, characterized in that, The dust removal and water removal device (14) uses H2SO4 solution for water removal.

4. The system for producing carbon dioxide and generating electricity using coal gasification gas according to claim 1, characterized in that, The precipitation chamber (20) is used for separation with Cu2SO4 solution.

5. The working method of the system for producing carbon dioxide and generating electricity using coal gasification product gas as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Coal undergoes an oxidation-reduction reaction in the gasification chamber to generate crude coal gas (1). The crude coal gas (1) flows through the underground dust removal chamber (4), the production well (2), the wellhead device (5), and the dust removal and water removal device (14) to remove dust and water, thus obtaining dry coal gas (15). The dry coal gas (15) enters the compressor (16) to drive the compressor (16) to work, and then enters the acid gas separation device (17) for chemical adsorption and separation to obtain acid gas (18) and combustible gas (19); the acid gas (18) enters the sedimentation chamber (20) to obtain gaseous CO2 (21); the gaseous CO2 (21) enters the compressor (16) for compression to obtain liquid CO2 (22); the combustible gas (19) enters the N2 separation device (25) to separate N2 (27) to obtain methane gas (26) and N2 (27); The thermal energy (6) of the crude coal gas (1) is transferred to the annulus (7) through the production well (2); room temperature water (8) is injected into the room temperature water inlet of the annulus (7), and the room temperature water (8) is vaporized into water vapor (9); the water vapor (9) drives the thermoelectric generator (10) to work, generate electrical energy (11) and condense into high temperature water (12), and then the high temperature water (12) enters the heating device (13) to exchange heat with the environment for heating.

6. The working method of the system for producing carbon dioxide and generating electricity using coal gasification product gas according to claim 5, characterized in that, The high-temperature water (12) is cooled to room temperature water (8) in the heating device (13) and then injected into the annulus (7) for recycling.

7. The working method of the system for producing carbon dioxide and generating electricity using coal gasification product gas according to claim 5, characterized in that, The N2 (27) enters the injection well (28) as a protective gas circulation.

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