Coal underground gasification production well cooling system based on chemical heat pipe

Abstract

The present application relates to a kind of coal underground gasification production well cooling system based on chemical heat pipe, and the system raw material gas storage tank, methane reforming reactor, compressor, methanation reactor, regulation system;The raw material gas storage tank outlet is connected with the raw material gas import of methane reforming reactor;The methane reforming reactor generation gas outlet is connected with compressor;The compressor outlet is connected with methanation reactor;The methanation reactor outlet is connected with the raw material gas import of methane reforming reactor;The methane reforming reactor is arranged in the overburden of gasification furnace coal seam;The coal gas produced by the gasification furnace is exchanged with methane reforming reactor after entering into condensing tank by production well.The present application uses the strong endothermic characteristics of methane reforming reaction to reduce the temperature of coal gas produced in the process of coal underground gasification, and the methane reforming reactor in the present application is closed circulation system, eliminates the poison of hydrogen sulfide and other gases generated by coal underground gasification to catalyst, improves the service life of catalyst, reduces the replacement frequency of catalyst, and reduces production cost.

Description

Technical Field

[0001] This invention relates to a cooling system for underground coal gasification production wells based on chemical heat pipes, belonging to the field of underground coal gasification technology. Background Technology

[0002] Underground coal gasification (UCG) is a new clean energy technology that uses chemical mining methods to directly burn and gasify coal underground to produce combustible gases (mainly H2, CO, and CH4). It is a high-carbon resource development technology that reduces carbon emissions. It integrates the three major processes of well construction, coal mining, and gasification, transforming physical coal mining into chemical gas extraction. This eliminates the need for large, cumbersome coal mining equipment and heavy manual labor, thus offering advantages such as high safety, low investment, high efficiency, low cost, rapid results, and low pollution.

[0003] In the underground coal gasification process, the gasification process involves burning coal to generate a large amount of heat. Part of this heat provides heat for the coal reduction reaction, and another part of the heat is carried by the generated coal gas. Therefore, the generated coal gas has a high temperature. High-temperature coal gas can cause thermal damage and damp heat corrosion damage to the production well, mainly manifested as deformation or breakage of the production well casing, which leads to the production well being unable to produce gas normally.

[0004] Currently, several patents propose solutions to this problem. Chinese patent application number CN202011029662.3, "A Temperature Control System and Method for Coal Gas Transportation in Underground Coal Gasification Production Wells," and Chinese patent application number CN202111679810.0, "Gas Extraction Method and Wellhead Device for Underground Coal Gasification," both propose using cold water spraying to lower the gas temperature. However, this method uses a large amount of water, potentially causing secondary pollution. Furthermore, cold water spraying relies on the latent heat of vaporization of water to absorb heat, increasing the risk of heat loss during production. This loss does not conform to the principle of energy tiered utilization. The Chinese patent application number CN202210705974.4, entitled "A Method and System for Cooling and Saving Energy from Coal Underground Gasification Produced Gas," uses CO2 from the coal gas in the production well as the source of CO2 in its methane catalytic reforming system. Since the CO2 is not captured, gases such as hydrogen sulfide in the coal gas will poison the catalyst and reduce its lifespan. Furthermore, the methane catalytic reforming reaction is carried out in a coal gas atmosphere, which reduces the reaction rate and methane conversion rate, affecting the efficiency of reducing the temperature of the coal gas in the production well. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a cooling system for underground coal gasification production wells based on chemical heat pipes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a cooling system for underground coal gasification production wells based on chemical heat pipes includes a feed gas storage tank 1, a methane reforming reactor 2, a compressor 3, a methanation reactor 4, and a control system 5; the outlet of the feed gas storage tank 1 is connected to the feed gas inlet of the methane reforming reactor 2, and the feed gas is methane, carbon dioxide, and water; the product gas outlet of the methane reforming reactor 2 is connected to the compressor 3; the outlet of the compressor 3 is connected to the methanation reactor 4; the outlet of the methanation reactor 4 is only connected to the feed gas inlet of the methane reforming reactor 2, forming a closed system. The system consists of a circulating loop; the methane reforming reactor 2 is located in the overlying rock strata above the coal seam of the gasifier; the coal gas produced by the gasifier enters the condenser tank 6 after heat exchange with the methane reforming reactor 2 through the production well; in the methane reforming reactor 2, the reaction catalysts are rhodium-based catalysts and nickel-based catalysts, and the packing method is that the rhodium-based catalyst is at the bottom near the high-temperature zone, and the nickel-based catalyst is at the top in the medium-temperature zone; the excess hydrogen and carbon monoxide at the outlet of the methane reforming reactor 2 enter the water-gas conversion device 7 together with the coal gas at the outlet of the condenser tank 6; the outlet of the water-gas conversion device is connected to the desulfurization and decarbonization device 8.

[0007] The cooling system for underground coal gasification production wells based on chemical heat pipes is characterized in that the control system 5 controls the supply of raw material gas and the emission of production gas.

[0008] The cooling system for underground coal gasification production wells based on chemical heat pipes is characterized in that the methane reforming reactor 2 is arranged in two ways in the underground coal gasification production well: a suspended arrangement and a tube arrangement along the inner wall of the production well. Furthermore, preheating fins can be arranged on the outer surface of the methane reforming reactor 2.

[0009] The cooling system for underground coal gasification production wells based on chemical heat pipes is characterized in that the methane reforming reactor 2 is divided into a shell side and a tube side, with the catalyst arranged in the tube side, and the feed gas entering from the shell side and exiting from the tube side.

[0010] The cooling system for underground coal gasification production wells based on chemical heat pipes is characterized in that the heat released by the methanation reactor 4 can generate steam as a UCG gasification agent or be used for power generation, heating, etc., using low-boiling-point media.

[0011] The cooling system for underground coal gasification production wells based on chemical heat pipes is characterized in that the sulfur dioxide captured by the desulfurization and decarbonization device 8 is used as the raw material for the methane reforming reactor.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. This invention solves the problem that excessively high coal temperature generated by underground coal gasification causes deformation or breakage of the production well casing, preventing gas from being produced.

[0014] 2. This invention utilizes the strong endothermic properties of methane reforming to reduce the temperature of coal gas produced during underground coal gasification. Compared with cooling by spraying water in the production well, this reduces environmental pollution and can recover the sensible heat in the coal gas, thus reducing heat loss.

[0015] 3. The methane reforming reactor of this invention is a closed-loop system, which eliminates the poisoning of catalysts by gases such as hydrogen sulfide produced by underground coal gasification, improves catalyst lifespan, reduces the number of catalyst replacements, and lowers production costs.

[0016] 4. The carbon dioxide source for the methane reforming reactor of this invention is provided by carbon dioxide capture from coal gas, thereby achieving carbon dioxide emission reduction.

[0017] 5. The raw materials for the methane reforming reactor of this invention are methane, carbon dioxide and water, which prevents carbon buildup in the methane and carbon dioxide reforming reaction, and the water is liquid under high pressure (3MPa, 300℃) for easy transportation.

[0018] 6. The catalyst filling of the methane reforming reactor of the present invention is a rhodium-based catalyst at the bottom and a nickel-based catalyst at the top, which can improve the conversion efficiency of methane. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a cooling system for an underground coal gasification production well based on a chemical heat pipe, according to the present invention.

[0020] In the diagram, 1-raw material gas storage tank, 2-methane reforming reactor, 3-compressor, 4-methanation reactor, 5-control system, 6-condenser, 7-water-gas conversion device, and 8-desulfurization and decarbonization device.

[0021] Figure 2 This is a schematic diagram of the methane catalytic reforming reactor of the present invention, arranged in a suspended manner within the production well;

[0022] Figure 3 This is a schematic diagram of the methane catalytic reforming reactor of the present invention arranged in a tubular configuration within a production well. Detailed Implementation

[0023] To better understand the technical essence and beneficial effects of the present invention, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] Combination Figure 1This invention relates to a cooling system for underground coal gasification production wells based on chemical heat pipes. The system includes a feed gas storage tank 1, a methane reforming reactor 2, a compressor 3, a methanation reactor 4, and a control system 5. The outlet of the feed gas storage tank 1 is connected to the feed gas inlet of the methane reforming reactor 2, and the feed gas consists of methane, carbon dioxide, and water. The product gas outlet of the methane reforming reactor 2 is connected to the compressor 3. The outlet of the compressor 3 is connected to the methanation reactor 4. The outlet of the methanation reactor 4 is only connected to the feed gas inlet of the methane reforming reactor 2, forming a closed loop. The methane reforming reactor 2 is located in the overlying rock strata above the coal seam of the gasifier; the coal gas produced by the gasifier enters the condenser 6 after heat exchange with the methane reforming reactor 2 through the production well; in the methane reforming reactor 2, the reaction catalysts are rhodium-based catalysts and nickel-based catalysts, and the packing method is that the rhodium-based catalyst is at the bottom near the high temperature zone, and the nickel-based catalyst is at the top in the medium temperature zone; the excess hydrogen and carbon monoxide at the outlet of the methane reforming reactor 2 enter the water-gas conversion device 7 together with the coal gas at the outlet of the condenser 6; the outlet of the water-gas conversion device is connected to the desulfurization and decarbonization device 8.

[0025] The control system 5 controls the supply of raw gas and the emission of production gas.

[0026] The methane reforming reactor 2 is arranged in the underground coal gasification production well in two ways: a hoisting arrangement and a tube arrangement along the inner wall of the production well. Preheating fins can be arranged on the outer surface of the methane reforming reactor 2.

[0027] The methane reforming reactor 2 is divided into a shell side and a tube side, with the catalyst arranged in the tube side and the feed gas entering from the shell side and exiting from the tube side.

[0028] The heat released by the methanation reactor 4 can generate steam as a UCG vaporizer or be used for power generation, heating, etc., using low-boiling-point media.

[0029] The sulfur dioxide collected by the desulfurization and decarbonization device 8 is used as the feedstock for the methane reforming reactor.

[0030] Example 1

[0031] An underground coal gasification furnace, capable of producing 300,000 Nm³ per day. 3 The gas produced is coal gas. The production well casing has a temperature resistance of 300℃, and the gasifier operates at a pressure of 3.6 MPa. The reaction space velocity of methane catalytic reforming reactor 2 is 8000 h⁻¹. -1 .

[0032] The catalytic reforming reaction of methane is: 2CH4 + H2O + CO2 = 3CO + 5H2 ΔH = 454.1 kJ / mol

[0033] The catalyst filling method is hoisting arrangement. Figure 2) or tubular arrangement ( Figure 3 ).

[0034] The coal gas enters the production well through the combustion chamber. The high-temperature coal gas exchanges heat with the methane catalytic reforming reactor 2, causing the gas temperature to drop from 600℃ to 300℃. This process requires the methane catalytic reforming reactor 2 to provide a heat exchange capacity of 1830 KJ / s, and the methane consumption rate is 162.5 m³ / s. 3 / h, the catalyst loading of the methane catalytic reforming reactor 2 is 81.25L. The feedstock (methane, carbon dioxide, and water) for the methane catalytic reforming reaction comes from the feedstock gas storage tank 1. The gas produced after the methane catalytic reforming reaction (carbon monoxide and hydrogen) enters the methanation reactor 4 through the compressor 3 to react and produce methane and a large amount of heat. The produced methane can be used as a feedstock in the methane catalytic reforming reaction, and the heat released by the methanation reactor 4 can generate steam as a UCG gasification agent or for power generation, heating, etc. The gas after heat exchange exits from the production well and enters the condenser 6 to remove tar and moisture from the gas. The control system 5 sends the excess hydrogen and carbon monoxide from the feedstock gas outlet of the methane reforming reactor together with the gas from the outlet of the condenser 6 into the water-gas conversion device 7. The gas from the water-gas conversion device 7 enters the desulfurization and decarbonization device 8 to remove CO2 and H2S. CO2 can be used as a feedstock in the methane catalytic reforming reaction. The purified gas can be used as a raw material for chemical synthesis, extraction of pure hydrogen, synthesis of natural gas, IGCC power generation, etc.

[0035] The specific embodiments of the present invention have been described above. The present invention is not limited to the examples described above. Changes made by those skilled in the art within the scope of the present invention are also within the protection scope of the present invention.

Claims

1. A cooling system for underground coal gasification production wells based on chemical heat pipes, characterized in that, The system includes a feed gas storage tank, a methane reforming reactor, a compressor, a methanation reactor, and a control system. The outlet of the feed gas storage tank is connected to the feed gas inlet of the methane reforming reactor, and the feed gas consists of methane, carbon dioxide, and water. The product gas outlet of the methane reforming reactor is connected to the compressor. The outlet of the compressor is connected to the methanation reactor. The outlet of the methanation reactor is connected only to the feed gas inlet of the methane reforming reactor, forming a closed loop. The methane reforming reactor is located above the coal seam of the gasifier in the production well. In a portion of the rock strata; the gas produced by the gasifier exchanges heat with the methane reforming reactor through a production well and then enters a condenser connected to the production well; in the methane reforming reactor, the reaction catalysts are rhodium-based catalysts and nickel-based catalysts, and the packing method is that the rhodium-based catalyst is at the bottom near the high-temperature zone, and the nickel-based catalyst is at the top in the medium-temperature zone; the excess hydrogen and carbon monoxide from the outlet of the methane reforming reactor enter the water-gas conversion device connected to the condenser along with the gas from the outlet of the condenser; the outlet of the water-gas conversion device is connected to the desulfurization and decarbonization device.

2. The cooling system for underground coal gasification production wells based on chemical heat pipes according to claim 1, characterized in that, The control system regulates the supply of raw gas and the emission of production gas.

3. The cooling system for underground coal gasification production wells based on chemical heat pipes according to claim 1, characterized in that, The methane reforming reactor is arranged in two ways in underground coal gasification production wells: a hoisting arrangement and a tube-line arrangement along the inner wall of the production well. Preheating fins are arranged on the outer surface of the methane reforming reactor.

4. The cooling system for underground coal gasification production wells based on chemical heat pipes according to claim 1, characterized in that, The methane reforming reactor is divided into a shell side and a tube side, with the catalyst arranged in the tube side and the feed gas entering from the shell side and exiting from the tube side.

5. The cooling system for underground coal gasification production wells based on chemical heat pipes according to claim 1, characterized in that, The carbon dioxide captured by the desulfurization and decarbonization unit is used as feedstock for the methane reforming reactor.

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