Carbon dioxide methanation and methane cracking coupled carbon sequestration power generation system and method

Abstract

The invention relates to a carbon dioxide methanation and methane cracking coupled carbon sequestration power generation system and method. The system comprises a methane cracking unit, a methanation reaction unit and an energy recovery unit. According to the method, a molten medium catalyst is adopted to catalyze methane cracking to generate hydrogen and a solid carbon material; hydrogen generated by methane cracking is used for a Sabatier reaction to generate methane and water; methane generated by the Sabatier reaction is also used for cracking to produce hydrogen and solid carbon materials; the heat released by the Sabatier reaction and / or the heat flowing out after heat absorption of the methane cracking reaction are / is used for power generation of the heat-to-power conversion power generation system. Through process innovation and system integration, the problem of catalyst carbon deposition inactivation is solved, outsourced hydrogen dependence is reduced, and gradient utilization of energy in the reaction process is achieved.

Description

Technical Field

[0001] This disclosure pertains to the field of carbon capture, utilization, and storage (CCUS) technology, and relates to a carbon sequestration power generation system and method that couples carbon dioxide (CO2) methanation with methane cracking. It describes an integrated process and system that utilizes an indirect conversion pathway coupled with a CO2 methanation reaction and a methane catalytic cracking reaction, and uses the high-temperature steam generated exothermically from methanation for power generation. Background Technology

[0002] Faced with increasingly severe environmental challenges, carbon capture, utilization, and storage (CCUS) technology has emerged. This technology aims to capture and separate CO2 from combustion emission sources, transporting it to oil and gas fields or deep-sea locations for storage for thousands of years or even longer, thereby effectively preventing or significantly reducing greenhouse gas emissions and mitigating adverse effects on the global climate. However, current carbon sequestration still faces challenges such as high technical difficulty, high cost, and poor economic viability, hindering its large-scale application. Therefore, developing efficient CO2 conversion technologies has become an urgent priority. Currently, the main direct CO2 conversion pathways include direct thermal cracking and electrochemical reduction. Direct thermal cracking requires heating CO2 to above 2000℃ (CO2 = C + O2, ΔH = +293kJ / mol), resulting in extremely high energy consumption and making industrialization difficult. While electrochemical reduction can be carried out at low temperatures, it suffers from low electrolysis efficiency and short electrode lifespan.

[0003] Therefore, indirect conversion pathways have attracted much attention, among which the CO2 methanation combined with methane cracking technology route shows great potential. This route generally consists of two stages: first, CO2 is hydrogenated to CH4 via the Sabatier reaction (CO2 + 4H2 = CH4 + 2H2O, ΔH = -165 kJ / mol, i.e., carbon dioxide methanation, also known as the Sabatier reaction); then, CH4 is converted to solid carbon and H2 via methane cracking (CH4 = C + 2H2, ΔH = +75.6 kJ / mol, i.e., methane cracking reaction). This method not only lowers the reaction temperature but also produces high-value-added carbon materials and hydrogen.

[0004] However, existing technologies still face several bottlenecks regarding the CO2 methanation combined with methane cracking route: First, in the methane cracking stage, the deactivation of solid catalysts due to carbon buildup and low heat transfer efficiency restricts continuous production. Existing methane catalytic cracking technologies mostly use fixed-bed reactors for methane cracking, and their core defects are: (1) solid catalysts deactivate rapidly due to carbon buildup, requiring frequent regeneration or replacement, affecting continuous production; (2) the reactor has low heat transfer efficiency and significant scale-up effect. For example, although the composite metal oxide catalyst reported in patent CN119857489A improves the methane conversion rate, the catalyst life problem caused by carbon buildup still needs to be solved. Regarding the regeneration problem of catalyst carbon buildup, the existing technology CN104998654A discloses a nickel-based catalyst and its preparation method and a method for producing hydrogen from methane through catalytic cracking. This method integrates a cracking reactor, a settling tank, a regenerator, a regeneration inclined tube, and a waiting inclined tube. The deactivated catalyst is regenerated in the regenerator by oxidation with an oxygen source and then returned to the reactor. During the regeneration process, the reactor is in a catalyst-free state, which is an intermittent process and reduces the utilization efficiency of the reactor. At the same time, the introduction of oxygen during the regeneration process poses a safety risk and also causes the emission of carbon oxides. The prior art CN119346011A reports a continuous recycling regeneration device and system for methane catalytic cracking hydrogen production. The catalyst is regenerated through a steam reforming regeneration reactor. Although this avoids the safety hazards caused by oxygen entering, it ultimately leads to additional equipment costs and CO2 emissions.

[0005] Secondly, energy efficiency is a generally overlooked issue in system integration. Compared to independent methane cracking and methanation reactions, there are few reports of coupling the two, and the energy efficiency of integrated systems is rarely mentioned. The high-temperature heat required for methane cracking and the large amount of reaction heat released by methanation are not effectively recovered and utilized, leading to increased energy consumption for the entire system.

[0006] Some patents / systems propose combining the Sabatier reaction with downstream cracking reactions, for example, in life support systems, closed environments, or aerospace applications, where the two steps are connected in series (US10486967): CO2 is methanated, and CH4 is cracked to produce hydrogen, which is used as the hydrogen source for CO2 methanation. Simultaneously, the water produced in the methanation reaction is electrolyzed to produce oxygen for life support, and the hydrogen produced from the electrolysis can also be used as the hydrogen source for the methanation reaction. This type of design aims to maintain a closed-loop oxygen cycle for life support and is not suitable for large-scale CO2 carbon sequestration applications. Furthermore, other existing solutions typically involve first methanating CO2, then cracking the resulting methane, or using methanation for exothermic processes and heat recovery for preheating the cracking reaction, rather than a complete closed-loop process of "first cracking natural gas to produce hydrogen, using the cracked hydrogen as the hydrogen source for CO2 methanation, then cracking the resulting methane; simultaneously using high-grade waste heat as high-temperature steam for power generation and low-grade waste heat for preheating the feed gas." While some existing technologies mention exothermic reactions and waste heat recovery (e.g., for feed preheating or maintaining reaction temperature), none utilize the high-temperature steam generated during methanation for power generation or couple power generation with the heat required for the cracking step. Patent CN215249587U discloses a carbon dioxide resource recovery system that proposes using hydrogen produced by water electrolysis for the CO2 methanation reaction, converting the resulting methane into hydrogen and solid carbon via a thermal cracking unit. This patent utilizes water electrolysis to produce hydrogen; currently, this technology appears to have high hydrogen source costs, making it unsuitable for large-scale production.

[0007] Therefore, it is of great significance to develop a CO2 indirect conversion system that can solve the problems of catalyst deactivation and thermal management and realize energy cascade utilization. Summary of the Invention

[0008] To address at least one of the above problems, this disclosure provides a carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking, comprising a methane cracking unit, a methanation reaction unit, and an energy recovery unit. The methane cracking unit includes a bubble column reactor and a gas-solid separation device; the bubble column reactor is used to crack methane to produce hydrogen and solid carbon materials, and is provided with a first inlet and a first outlet, and is filled with a molten medium catalyst; the first outlet is connected to the feed inlet of the gas-solid separation device. The methanation reaction unit includes a methanation reactor, a gas-liquid separator, and a carbon dioxide inlet pipe. The methanation reactor uses hydrogen and carbon dioxide as reaction raw materials to catalytically produce methane. It is equipped with a second inlet and a second outlet and is filled with a catalyst for the methanation reaction. The second inlet is connected to the carbon dioxide inlet pipe. The gas outlet of the gas-liquid separator is connected to the first inlet. The energy recovery unit includes a heat exchanger and a heat-to-work power generation system; the heat exchanger includes a first heat exchanger and a second heat exchanger; the first outlet is connected to the second inlet through the first heat exchanger, and the first heat exchanger is also connected to the heat-to-work power generation system to transfer the heat flowing out of the bubbling tower reactor to the heat-to-work power generation system for power generation; the second outlet is connected to the feed inlet of the gas-liquid separator through the second heat exchanger, and the second heat exchanger is also connected to the heat-to-work power generation system to transfer the heat flowing out of the second outlet to the heat-to-work power generation system for power generation.

[0009] In some embodiments, the methanation reactor is connected to the heat-to-work power generation system to heat the water vapor formed by the medium water (i.e., water is used as a medium for heat transfer) flowing through the methanation reactor, which is then introduced into the heat-to-work power generation system for power generation; the heat-to-work power generation system includes one or more of a steam turbine generator set and an organic Rankine cycle generator set; the methanation reactor is selected from a fixed-bed reactor and / or a fluidized-bed reactor.

[0010] In some implementations, the first outlet is connected to the second inlet via the first heat exchanger, specifically: the first outlet is connected to the feed inlet of the gas-solid separation device, and the gas outlet of the gas-solid separation device is connected to the second inlet via the first heat exchanger.

[0011] In some implementations, the first outlet is connected to the second inlet via the first heat exchanger, specifically: the first outlet is connected to the feed inlet of the gas-solid separation device via the first heat exchanger, and the gas outlet of the gas-solid separation device is connected to the second inlet.

[0012] In some embodiments, the methane cracking unit further includes a burner connected to the bubble column reactor for supplying heat to the bubble column reactor; the heat exchanger further includes a third heat exchanger; the flue gas outlet of the burner is connected to the third heat exchanger, which is in turn connected to the heat-to-work power generation system, so that the heat flowing out of the flue gas outlet of the burner is transferred to the heat-to-work power generation system for power generation.

[0013] In some embodiments, the heat exchanger further includes a fourth heat exchanger; the gas outlet of the gas-liquid separator is connected to the first inlet through the fourth heat exchanger, and the flue gas outlet of the burner is connected to the fourth heat exchanger through the third heat exchanger, so as to use the waste heat of the flue gas in the fourth heat exchanger for preheating the gas to flow into the first inlet.

[0014] In some embodiments, the heat exchanger further includes a fourth heat exchanger; the gas outlet of the gas-liquid separator is connected to the first inlet through the fourth heat exchanger, and the first outlet is connected to the second inlet in sequence through the gas-solid separation device, the first heat exchanger and the fourth heat exchanger, so as to use the waste heat of the gas flowing out of the bubble column reactor after being cooled by the first heat exchanger for preheating the gas to flow into the first inlet.

[0015] In some embodiments, the methane cracking unit further includes a natural gas inlet pipe; the natural gas inlet pipe is also connected to the first inlet via the fourth heat exchanger, so that the natural gas delivered by the natural gas inlet pipe can be preheated in the fourth heat exchanger.

[0016] In some embodiments, the methanation reaction unit further includes a compressor; the gas outlet of the gas-liquid separator is connected to the first inlet in sequence through the compressor and the fourth heat exchanger, so that the gas flowing out of the gas outlet of the gas-liquid separator is compressed by the compressor, preheated by the fourth heat exchanger, and then enters the bubble column reactor.

[0017] In some embodiments, the fuel inlet of the burner is connected to the gas outlet of the gas-solid separator to deliver the gas flowing out of the gas outlet of the gas-solid separator into the burner; the burner is provided with an additive inlet for introducing oxygen and / or air.

[0018] In some implementations, the fuel inlet of the burner is connected to the gas outlet of the gas-solid separation device via the first heat exchanger, so as to deliver the cooled gas to the burner.

[0019] In some embodiments, the heat exchanger further includes a fifth heat exchanger; the second outlet is connected to the inlet of the gas-liquid separator in sequence through the second heat exchanger and the fifth heat exchanger, and the second inlet is connected to the carbon dioxide inlet pipe. The fifth heat exchanger is installed on the carbon dioxide inlet pipe, so that the product flowing out of the second outlet enters the gas-liquid separator for separation after being cooled by two stages of heat exchange, and the heat flowing out of the second outlet is transferred to the heat-power conversion power generation system for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe.

[0020] In some embodiments, the methane cracking unit further includes a solid carbon collector connected to the solid carbon outlet of the gas-solid separation device; the methanation reaction unit further includes a condensate pump connected to the liquid outlet of the gas-liquid separator for pumping liquid flowing out of the liquid outlet of the gas-liquid separator into downstream equipment.

[0021] In some implementations, the downstream equipment includes a water purification device; the liquid outlet of the gas-liquid separator is connected to the heat-to-power conversion power generation system in sequence through the condensate pump, the water purification device and the first heat exchanger, with the purified water used as the medium water for the first heat exchanger. The liquid outlet of the gas-liquid separator is also connected to the heat-to-power conversion power generation system in sequence through the condensate pump, the water purification device and the second heat exchanger, with the purified water used as the medium water for the second heat exchanger. The heat exchanger also includes a third heat exchanger; the flue gas outlet of the burner is connected to the third heat exchanger, and the third heat exchanger is connected to the heat-to-power conversion power generation system, so that the heat flowing out of the flue gas outlet of the burner is transferred to the heat-to-power conversion power generation system for power generation; the liquid outlet of the gas-liquid separator is also connected to the heat-to-power conversion power generation system in sequence through the condensate pump, the water purification device and the third heat exchanger, with purified water as the medium water of the third heat exchanger; The methanation reactor is connected to the heat-to-work power generation system, so that the heat released from the methanation reaction heats the water vapor formed by the medium water flowing through the methanation reactor, which is then introduced into the heat-to-work power generation system for power generation. The liquid outlet of the gas-liquid separator is also connected to the heat-to-work power generation system in sequence through the condensate pump, the water purification device, and the methanation reactor, using purified water as the medium water for the methanation reactor. The addition of the water purification device increases operating costs, but it is still economical for offshore or island operations. Therefore, in application scenarios where freshwater resources are scarce, the introduction of a water purification device to reuse the water generated in the methanation reactor can be considered.

[0022] In some embodiments, the heat-to-work conversion power generation system is electrically connected to the bubbling tower reactor, and the electrical energy generated by the heat-to-work conversion power generation system can be used for methane cracking heating.

[0023] This disclosure also provides a carbon sequestration power generation method coupled with carbon dioxide methanation and methane cracking, which employs the system described above; a molten medium catalyst is used to catalyze the cracking of methane to produce hydrogen and solid carbon materials; the hydrogen produced by methane cracking is used in a Sabatier reaction to produce methane and water; the methane produced in the Sabatier reaction is then used for cracking to produce hydrogen and solid carbon materials; the heat released by the Sabatier reaction and / or the heat released after the methane cracking reaction is endothermic is used to generate electricity in a heat-to-work conversion power generation system.

[0024] In some implementations, the electrical energy generated by the heat-to-work conversion power generation system is used for methane cracking heating or for other applications requiring electrical energy; the heat released by the Sabatier reaction is also used for preheating the reactant carbon dioxide of the Sabatier reaction.

[0025] In some embodiments, the molten medium catalyst is a molten metal, or a molten alloy, or a molten salt, or a composite system of molten metal / alloy and molten salt; the catalyst for the Sabatier reaction is a Ni-based methanation catalyst.

[0026] In some embodiments, the methane cracking unit further includes a burner; the burner is connected to the bubble column reactor for supplying heat to the bubble column reactor; the heat exchanger further includes a third heat exchanger, a fourth heat exchanger, and a fifth heat exchanger; the flue gas outlet of the burner is connected to the third heat exchanger, which in turn is connected to the heat-to-work power generation system, so that the heat flowing out of the flue gas outlet of the burner is transferred to the heat-to-work power generation system for power generation; the gas outlet of the gas-liquid separator is connected to the first inlet through the fourth heat exchanger, and the flue gas outlet of the burner is connected to the fourth heat exchanger through the third heat exchanger, so that the waste heat of the flue gas in the fourth heat exchanger is used for the gas to flow into the first inlet. The first outlet is preheated; the second outlet is connected to the inlet of the gas-liquid separator via the second heat exchanger and the fifth heat exchanger in sequence, and the second inlet is connected to the carbon dioxide inlet pipe. The fifth heat exchanger is installed on the carbon dioxide inlet pipe, so that the product flowing out of the second outlet enters the gas-liquid separator for separation after being cooled by two stages of heat exchange, and the heat flowing out of the second outlet is transferred to the heat-power conversion power generation system for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe; the first outlet is connected to the second inlet via the first heat exchanger specifically: the first outlet is connected to the inlet of the gas-solid separation device, and the gas outlet of the gas-solid separation device is connected to the second inlet via the first heat exchanger. The method includes the following steps: S1. The hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor are transferred to the gas-solid separation device, while a portion of the molten medium catalyst and methane are introduced. The gas separated by the gas-solid separation device is cooled by heat exchange in the first heat exchanger. Part of the gas, together with the carbon dioxide supplied by the carbon dioxide inlet pipe, enters the methanation reactor to undergo the Sabatier reaction, while the other part enters the burner for combustion to provide heat for the methane cracking reaction. The carbon dioxide supplied by the carbon dioxide inlet pipe is preheated by heat exchange in the fifth heat exchanger. Methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second and fifth heat exchangers before entering the gas-liquid separator. The gas separated by the gas-liquid separator enters the bubble column reactor through the fourth heat exchanger to participate in the methane cracking reaction. The medium water in the first, second, and third heat exchangers is heated and used to generate electricity in the heat-to-work conversion power generation system. The medium water in the methanation reactor absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work conversion power generation system. S3. The flue gas generated by the burner is cooled by heat exchange in the third heat exchanger and the fourth heat exchanger. The heat is used to heat the medium water in the third heat exchanger in step S2 and to preheat the methane cracking reaction gas in step S1. The electrical energy generated by the heat-power conversion power generation system is used to heat the methane cracking reaction in step S1.

[0027] In some embodiments, the methane cracking unit further includes a burner; the burner is connected to the bubble column reactor for supplying heat to the bubble column reactor; the heat exchanger further includes a third heat exchanger, a fourth heat exchanger, and a fifth heat exchanger; the flue gas outlet of the burner is connected to the third heat exchanger, which in turn is connected to the heat-to-work power generation system, so that the heat flowing out of the flue gas outlet of the burner is transferred to the heat-to-work power generation system for power generation; the gas outlet of the gas-liquid separator is connected to the first inlet through the fourth heat exchanger, and the flue gas outlet of the burner is connected to the fourth heat exchanger through the third heat exchanger, so that the waste heat of the flue gas in the fourth heat exchanger is used for the gas to flow into the first inlet. The first outlet is preheated; the second outlet is connected to the inlet of the gas-liquid separator via the second heat exchanger and the fifth heat exchanger in sequence, and the second inlet is connected to the carbon dioxide inlet pipe. The fifth heat exchanger is installed on the carbon dioxide inlet pipe, so that the product flowing out of the second outlet enters the gas-liquid separator for separation after being cooled by two stages of heat exchange, and the heat flowing out of the second outlet is transferred to the heat-power conversion power generation system for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe; the first outlet is connected to the second inlet via the first heat exchanger specifically: the first outlet is connected to the inlet of the gas-solid separation device via the first heat exchanger, and the gas outlet of the gas-solid separation device is connected to the second inlet. The method includes the following steps: S1. The hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor are cooled by heat exchange in the first heat exchanger and then transferred to the gas-solid separation device, while a portion of the molten medium catalyst and methane are introduced. Part of the gas separated by the gas-solid separation device enters the methanation reactor together with the carbon dioxide supplied by the carbon dioxide inlet pipe to undergo the Sabatier reaction, and the other part enters the burner for combustion to provide heat for the methane cracking reaction. The carbon dioxide supplied by the carbon dioxide inlet pipe is preheated by heat exchange in the fifth heat exchanger. Methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second and fifth heat exchangers before entering the gas-liquid separator. The gas separated by the gas-liquid separator enters the bubble column reactor through the fourth heat exchanger to participate in the methane cracking reaction. The medium water in the first, second, and third heat exchangers is heated and used to generate electricity in the heat-to-work conversion power generation system. The medium water in the methanation reactor absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work conversion power generation system. S3. The flue gas generated by the burner is cooled by heat exchange in the third heat exchanger and the fourth heat exchanger. The heat is used to heat the medium water in the third heat exchanger in step S2 and to preheat the methane cracking reaction gas in step S1. The electrical energy generated by the heat-power conversion power generation system is used to heat the methane cracking reaction in step S1.

[0028] In some embodiments, the methane cracking unit further includes a burner; the burner is connected to the bubble column reactor for supplying heat to the bubble column reactor; the heat exchanger further includes a third heat exchanger, a fourth heat exchanger, and a fifth heat exchanger; the flue gas outlet of the burner is connected to the third heat exchanger, which in turn is connected to the heat-to-work power generation system, so that the heat flowing out of the flue gas outlet of the burner is transferred to the heat-to-work power generation system for power generation; the gas outlet of the gas-liquid separator is connected to the first inlet through the fourth heat exchanger, and the first outlet sequentially passes through the gas-solid separation device, the first heat exchanger, and the fourth heat exchanger. The heat exchanger is connected to the second inlet to preheat the gas to be flowed into the first inlet using the residual heat from the bubble column reactor after being cooled by the first heat exchanger. The second outlet is connected to the inlet of the gas-liquid separator via the second heat exchanger and the fifth heat exchanger in sequence. The second inlet is connected to the carbon dioxide inlet pipe, and the fifth heat exchanger is installed on the carbon dioxide inlet pipe so that the product flowing out of the second outlet enters the gas-liquid separator for separation after being cooled by two stages of heat exchange. The heat flowing out of the second outlet is transferred to the heat-power conversion power generation system for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe. The method includes the following steps: S1. The hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor are transferred to the gas-solid separation device, while a portion of the molten medium catalyst and methane are introduced. Part of the gas separated by the gas-solid separation device is cooled by heat exchange in the first heat exchanger and the fourth heat exchanger, and then enters the methanation reactor together with the carbon dioxide supplied by the carbon dioxide inlet pipe to undergo the Sabatier reaction. The other part is cooled by heat exchange in the first heat exchanger and then enters the burner for combustion to provide heat for the methane cracking reaction. The carbon dioxide supplied by the carbon dioxide inlet pipe is preheated by heat exchange in the fifth heat exchanger. Methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second and fifth heat exchangers before entering the gas-liquid separator. The gas separated by the gas-liquid separator enters the bubble column reactor through the fourth heat exchanger to participate in the methane cracking reaction. The medium water in the first, second, and third heat exchangers is heated and used to generate electricity in the heat-to-work conversion power generation system. The medium water in the methanation reactor absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work conversion power generation system. S3. The flue gas generated by the burner is cooled by heat exchange in the third heat exchanger, and the heat is used to heat the medium water in the third heat exchanger in step S2; the electrical energy generated by the heat-power conversion power generation system is used to heat the methane cracking reaction in step S1.

[0029] This disclosure provides a CO2 conversion system and method that can operate continuously, stably, and efficiently with low overall energy consumption. Through process innovation and system integration, it solves the problem of catalyst deactivation due to carbon buildup, reduces dependence on purchased hydrogen, and achieves cascaded utilization of energy during the reaction process.

[0030] The beneficial effects of this disclosure are: 1) Solving the problem of catalyst deactivation: The molten medium method (i.e., using molten medium catalysts for methane cracking) provides a new approach to this problem. The liquid molten medium (such as metals or salts) can serve as a "flowing" catalytic interface. Due to the density difference, the solid carbon material generated in the reaction floats to the surface of the molten medium catalyst, thereby achieving in-situ separation of the catalyst and products and fundamentally solving the problem of catalyst deactivation due to carbon deposition. Molten medium catalysts avoid the core problem of solid catalyst deactivation due to carbon deposition, ensuring the long-term continuous and stable operation of the system.

[0031] 2) Maximize energy efficiency: Significantly reduce operating costs through innovative cascade utilization of thermal energy (preheating, steam power generation).

[0032] 3) High product value: The final products are solid carbon materials (such as sheet graphite or graphene nanosheets) and hydrogen, which have a much higher economic value than simple carbon sequestration.

[0033] 4) Significant emission reduction effect: It realizes the conversion of CO2 into stable solid products, which is a technological path with negative carbon potential. For every ton of CO2 processed, 0.75 tons of CO2 equivalent can be reduced, while producing 0.7 tons of solid carbon materials and generating 80 kW of steam power (based on an efficiency of 80%).

[0034] The following will further explain the concept, specific structure and technical effects of this disclosure in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking according to Embodiment 1 of this disclosure.

[0037] Figure 2 This is a schematic diagram of the carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking according to Embodiment 2 of this disclosure.

[0038] Figure 3 This is a schematic diagram of the carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking according to Embodiment 3 of this disclosure.

[0039] Figure label: 101: Natural Gas Inlet Pipe 102: Bubble Tower Reactor 103: Burner 104: Solid carbon collector 109: Carbon dioxide intake pipe 110: Methanation reactor 111: Heat-to-Work Conversion Power Generation System 113: Gas-liquid separator 114: Condensate pump 115: Condensate pipe 116: Gas-solid separation device 201: First Water Pipe 202: Second water pipe 203: Third water pipe 204: Fourth water pipe 205: First steam pipe 206: Second steam pipe 207: Third steam pipe 208: Fourth steam pipe 301: Third heat exchanger 302: First heat exchanger 303: Second heat exchanger 304: Fourth heat exchanger 305: Fifth heat exchanger 401: Compressor 11: First Import 12: First Exit 13: Fuel inlet of the burner 14: Import of additives 15: Second Import 16: Second Exit 17: Inlet of the gas-liquid separator 18: Gas outlet of the gas-liquid separator 19: Liquid outlet of the gas-liquid separator 31: Inlet of the gas-solid separation device 32: Gas outlet of the gas-solid separation unit 33: Solid carbon outlet of gas-solid separation unit 107: Flue gas outlet of the burner. Detailed Implementation

[0040] To facilitate understanding by those skilled in the art, some terms appearing in this document are explained and clarified.

[0041] In this document, the singular forms “an,” “a,” and “the” include their plural forms, unless the context otherwise requires.

[0042] In this document, unless otherwise stated, the terms “comprising,” “including,” “having,” or “containing” mean that the listed technical features are included, but do not exclude the inclusion of other technical features.

[0043] In this article, ordinal numbers such as "first" and "second" added before a component are used to distinguish these components, not to sort them according to the order of the ordinal numbers.

[0044] In this paper, the term "and / or" refers to any one of three cases, for example, the three cases of A and / or B are: either A, or B, or A and B.

[0045] In this article, the terms "connected" or "linked" can refer to a direct connection between two components or an indirect connection between two components through one or more other components.

[0046] Example 1 Figure 1 The general structure of the carbon sequestration and power generation system coupled with carbon dioxide methanation and methane cracking in this embodiment is shown in a simplified structural diagram. The system includes a methane cracking unit, a methanation reaction unit, and an energy recovery unit.

[0047] The methane cracking unit includes a bubble column reactor 102, a gas-solid separator 116, a burner 103, a solid carbon collector 104, and a natural gas inlet pipe 101. The bubble column reactor 102 is used for methane cracking to produce hydrogen and solid carbon materials. It is equipped with a first inlet 11 and a first outlet 12, and is filled with a molten catalyst medium. The first outlet 12 is connected to the feed inlet 31 of the gas-solid separator. The feed inlet 31 of the gas-solid separator is located on the side of the gas-solid separator 116, the gas outlet 33 of the gas-solid separator is located at the top of the gas-solid separator 116, and the solid carbon outlet 33 of the gas-solid separator is located at the bottom of the gas-solid separator 116.

[0048] The methanation reaction unit includes a methanation reactor 110, a gas-liquid separator 113, a compressor 401, and a carbon dioxide inlet pipe 109. The methanation reactor 110 uses hydrogen and carbon dioxide as reactants to catalytically produce methane. It is equipped with a second inlet 15 and a second outlet 16, and is internally filled with a catalyst for the methanation reaction. The methanation reactor 110 adopts a fixed-bed or fluidized-bed design and is internally loaded with a Ni-based methanation catalyst. The second inlet 15 is connected to the carbon dioxide inlet pipe 109. The gas outlet 18 of the gas-liquid separator is connected to the first inlet 11.

[0049] The energy recovery unit includes heat exchangers and a heat-to-work power generation system 111. The heat exchangers include a first heat exchanger 302, a second heat exchanger 303, a third heat exchanger 301, a fourth heat exchanger 304, and a fifth heat exchanger 305. The heat-to-work power generation system 111 includes a steam turbine generator set and an organic Rankine cycle generator set. For the high-grade heat source from the bubbling tower reactor 102 and the burner 103, a steam turbine generator set is preferably used for energy recovery; for the medium- and low-grade heat source from the methanation reactor 110, an organic Rankine cycle generator set is preferably used for energy recovery.

[0050] The first heat exchanger 302 is connected to the steam turbine generator set, and the first outlet 12 is connected to the feed inlet 31 of the gas-solid separation device. The gas outlet 32 ​​of the gas-solid separation device is connected to the second inlet 15 through the first heat exchanger 302, thereby exchanging the heat flowing out of the bubbling tower reactor 102 to the steam turbine generator set for power generation.

[0051] The second outlet 16 is connected to the inlet 17 of the gas-liquid separator via the second heat exchanger 303. The second heat exchanger (303) is also connected to the steam turbine generator set to exchange the heat flowing out of the second outlet 16 with the steam turbine generator set for power generation.

[0052] The methanation reactor 110 is connected to an organic Rankine cycle generator set to heat the steam formed by the medium water flowing through the methanation reactor 110, which is then introduced into the organic Rankine cycle generator set for power generation. A burner 103 is located at the bottom of the bubble column reactor 102 (in other embodiments, it may be located on the side or top) to heat the bubble column reactor 102. The burner's flue gas outlet 107 is connected to a third heat exchanger 301, which is in turn connected to a steam turbine generator set, so that the heat flowing out of the burner's flue gas outlet 107 is transferred to the steam turbine generator set for power generation.

[0053] The gas outlet 18 of the gas-liquid separator is connected to the first inlet 11 through the fourth heat exchanger 304, and the flue gas outlet 107 of the burner is connected to the fourth heat exchanger 304 through the third heat exchanger 301, so as to use the waste heat of the flue gas in the fourth heat exchanger 304 to preheat the gas to be flowed into the first inlet 11.

[0054] The natural gas inlet pipe 101 is also connected to the first inlet 11 through the fourth heat exchanger 304, so that the natural gas transported by the natural gas inlet pipe 101 can be preheated in the fourth heat exchanger 304.

[0055] The gas outlet 18 of the gas-liquid separator is connected to the first inlet 11 in sequence through a compressor and a fourth heat exchanger 304, so that the gas flowing out of the gas outlet 18 of the gas-liquid separator is compressed by the compressor 401, and then preheated by the fourth heat exchanger 304 before entering the bubble column reactor 102.

[0056] The fuel inlet 13 of the burner is connected to the gas outlet 32 ​​of the gas-solid separator to deliver the gas flowing out of the gas outlet 32 ​​of the gas-solid separator into the burner 103. The burner 103 is provided with an additive inlet 14 for introducing oxygen and / or air.

[0057] The fuel inlet 13 of the burner is connected to the gas outlet 32 ​​of the gas-solid separation device through the first heat exchanger 302, so as to deliver the gas cooled by heat exchange to the burner 103.

[0058] The second outlet 16 is connected to the inlet 17 of the gas-liquid separator via the second heat exchanger 303 and the fifth heat exchanger 305 in sequence. The second inlet 15 is connected to the carbon dioxide inlet pipe 109. The fifth heat exchanger 305 is installed on the carbon dioxide inlet pipe 109, so that the product flowing out of the second outlet 16 enters the gas-liquid separator 113 for separation after being cooled by two stages of heat exchange. The heat flowing out of the second outlet 16 is transferred to the organic Rankine cycle generator set for power generation and preheating of the carbon dioxide in the carbon dioxide inlet pipe 109.

[0059] Solid carbon collector 104 is connected to the solid carbon outlet 33 of the gas-solid separation unit. The methanation reaction unit also includes a condensate pump 114. The condensate pump 114 is connected to the liquid outlet 19 of the gas-liquid separator and is used to pump the liquid flowing out of the liquid outlet 19 of the gas-liquid separator into downstream equipment.

[0060] The heat-to-work conversion power generation system 111 is electrically connected to the bubble column reactor 102. The electrical energy generated by the heat-to-work conversion power generation system 111 is used for methane cracking heating or for other occasions that require electrical energy.

[0061] This embodiment also provides a carbon sequestration power generation method coupled with carbon dioxide methanation and methane cracking. It employs a molten medium catalyst to catalyze the cracking of methane to produce hydrogen and solid carbon materials. The hydrogen produced by methane cracking is used in a Sabatier reaction to produce methane and water. The methane produced in the Sabatier reaction is then used for cracking to produce hydrogen and solid carbon materials. The heat released by the Sabatier reaction and / or the heat released after the methane cracking reaction is endothermic is used to generate electricity in a heat-to-work conversion power generation system. The molten medium catalyst is a molten metal, a molten alloy, a molten salt, or a composite system of molten metal / alloy and molten salt. The catalyst for the Sabatier reaction is a Ni-based methanation catalyst.

[0062] Specifically, this carbon sequestration power generation method, using the system described in this embodiment, includes the following steps: S1. The hydrogen and solid carbon material produced by the methane cracking reaction (operating temperature maintained at 900-1050℃) in the bubble column reactor 102 are transferred to the gas-solid separation device 116, while some molten medium catalyst and methane are introduced. The gas separated by the gas-solid separation device 116 is cooled by heat exchange in the first heat exchanger 302. Part of it enters the methanation reactor 110 together with the carbon dioxide transported by the carbon dioxide inlet pipe 109 to undergo the Sabatier reaction, and the other part enters the burner 103 for combustion to provide heat for the methane cracking reaction; the carbon dioxide transported by the carbon dioxide inlet pipe 109 is preheated by heat exchange in the fifth heat exchanger 305. Step S1 includes (1) the methane cracking stage and (2) the gas-solid separation stage.

[0063] (1) Methane cracking stage: After being preheated by the fourth heat exchanger 304, CH4 gas is introduced from the bottom of the bubble column reactor 102, passes through the molten catalyst medium, and undergoes a cracking reaction. CH4= C + 2H2 (ΔH = +75.6 kJ / mol) The methane conversion rate can reach over 70%. The feedstock for the methane cracking reaction (natural gas and Sabatier reaction product gas) is preheated and then bubbled into the bottom of the bubble column reactor 102 in the form of bubbles. During the rising process, the bubbles undergo catalytic cracking reaction to generate solid carbon materials and hydrogen. Both are carried out of the bubble column reactor 102 by the gas flow and enter the gas-solid separation device 116.

[0064] (2) Gas-solid separation stage: The generated solid carbon floats on the surface of the molten medium catalyst and is carried by the reaction gas flow from the top of the bubble column reactor 102 to the downstream gas-solid separation device 116, where it is continuously collected by the solid carbon collector 104. The generated H2-rich cracked gas passes through the first heat exchanger 302, and part of the cracked gas enters the burner 103 for combustion to provide energy, while the rest is mixed with CO2 and then enters the methanation reactor 110.

[0065] Methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second heat exchanger 303 and the fifth heat exchanger 305 before entering the gas-liquid separator 113. The gas separated by the gas-liquid separator 113 enters the bubble column reactor 102 through the fourth heat exchanger 304 to participate in the methane cracking reaction, while the liquid is condensed by the condensate pump 114 and flows into the condensate pipe 115 for discharge. The water used for heat transfer enters the first heat exchanger 302, the second heat exchanger 303, and the third heat exchanger 301 through the second water pipe 202, the fourth water pipe 204, and the first water pipe 201, respectively, and is heated to steam. After being heated to steam, it flows into the heat-to-work power generation system 111 through the second steam pipe 206, the fourth steam pipe 208, and the first steam pipe 205, respectively, for power generation. The water used for heat transfer also enters the methanation reactor 110 through the third water pipe 203 to absorb the heat released by the Sabatier reaction, and is heated into water vapor, which flows into the heat-to-work power generation system 111 through the third steam pipe 207 for power generation. Step S2 includes (3) the methanation reaction stage and (4) the gas-liquid separation stage.

[0066] (3) Methanation reaction stage: CO2 and H2 are mixed in a ratio of n(H2):n(CO2) = 4:1. The CO2 is preheated to 200°C using the waste heat from the cracked gas before entering the methanation reactor 110. Under the action of a catalyst, the Sabatier reaction occurs at 320°C and 1.5 MPa. CO2+ 4H2= CH4+ 2H2O (ΔH = -165 kJ / mol) The reaction conversion rate can reach over 90%, and the methane selectivity exceeds 95%.

[0067] (4) Gas-liquid separation stage: The gas mixture after methanation first passes through a primary heat exchanger (second heat exchanger 303) to generate medium-pressure steam, which is then transported to the heat-to-power conversion power generation system 111 via the fourth steam pipe 208. The product gas then passes through a secondary heat exchanger (fifth heat exchanger 305) to preheat CO2 using low-quality heat. Afterward, the product gas enters a gas-liquid separator 113 for separation. The separated water (approximately 30-50°C) is discharged via a condensate pump 114. The dried CH4 gas (purity >95%) is pressurized by a compressor 401 and, together with the methane feedstock transported by the natural gas inlet pipe 101, is preheated by the fourth heat exchanger 304 before entering the bubble column reactor 102.

[0068] S3. The flue gas generated by the burner 103 is cooled by heat exchange in the third heat exchanger 301 and the fourth heat exchanger 304. The heat is used to heat up the liquid entering the third heat exchanger 301 in step S2 and to preheat the methane cracking reaction gas in step S1. The electrical energy generated by the heat-to-work conversion power generation system 111 is used to heat the methane cracking reaction in step S1. Step S3 includes (5) the energy recovery stage.

[0069] (5) Energy recovery stage: The high-temperature gas (approximately 980°C) exiting the bubbling tower reactor 102 passes through the first heat exchanger 302, where it generates high-temperature steam from the medium water transported via the second water pipe 202. This steam is then transported to the heat-to-work power generation system 111 via the second steam pipe 206. The high-temperature flue gas generated by the burner 103 passes through the first-stage heat exchanger (third heat exchanger 301), where it generates high-temperature steam from the medium water transported via the first water pipe 201. This steam is then transported to the heat-to-work power generation system 111 via the first steam pipe 205. The flue gas continues through pipelines to the second-stage heat exchanger (fourth heat exchanger 304) to preheat the feed gas for the pyrolysis reaction.

[0070] The heat from the methanation reaction is generated in two ways: firstly, the medium water transported by the third water pipe 203 passes through the heat exchange tubes inside the methanation reactor 110 to produce high-temperature steam, which is then transported to the heat-to-work power generation system 111 via the third steam pipe 207 for power generation; secondly, the high-temperature product gas generated by the reaction passes through the first-stage heat exchanger (second heat exchanger 303) to convert the medium water transported by the fourth water pipe 204 into high-temperature steam, which is then transported to the heat-to-work power generation system 111 via the fourth steam pipe 208 for power generation. The product gas then passes through the second-stage heat exchanger (fifth heat exchanger 305) for further recovery of low-quality heat sources for preliminary CO2 preheating.

[0071] Steam enters the heat-to-work conversion power generation system 111 to generate electricity, which is used to power internal equipment or to transmit power to external systems.

[0072] Experimental Example 1 The system and method of Example 1 are used. The process is described below, and the results are summarized in Table 1: 1. Methane cracking stage Methane is fed through natural gas inlet pipe 101 at a rate of 126.2 tons / day and a pressure of 2.1 MPa.

[0073] The Sabatier reaction produces methane and a small amount of incompletely reacted CO2 (approximately 95 vol.% CH4 and approximately 5 vol.% CO2), which constitutes the circulating gas: 126.4 tons / day at a pressure of 2 MPa.

[0074] The mixed gas, totaling 252.6 tons / day, is preheated by the fourth heat exchanger 304 to a pressure of approximately 1.9 MPa and a temperature of approximately 600 ℃ before entering the bubble column reactor 102 for pyrolysis reaction.

[0075] Methane cracking reaction products: Methane conversion rate 75%, producing 133.2 tons / day of solid carbon; gaseous product flow rate approximately 119.4 tons / day, after passing through the first heat exchanger 302, the gas pressure is approximately 1.5 MPa, the temperature is approximately 320 °C, and the composition is approximately 85.7% H2 and 14.3% CH4. Of this, 93.2 tons / day of cracked gas is used for the methanation reaction, and the remaining 26.2 tons / day is depressurized (from approximately 1.5 MPa to approximately 0.02 MPa) and enters burner 103 to provide a heat source for heating / maintaining the temperature of the bubble column reactor 102. The calculations in this experimental example are performed without considering the heat-to-work conversion power generation system 111 generating electricity to heat the bubble column reactor 102. The heat-to-work conversion power generation system 111 can generate electricity to heat the bubble column reactor 102 as needed. That is, heat can be supplied to the methane cracking reaction through electric heating and / or burner heating.

[0076] 2. Methanation stage The gaseous products of methane cracking, namely cracked gas (93.2 tons / day), are mixed with CO2 gas (183.3 tons / day, 25 ℃, 1.5 MPa) and fed into methanation reactor 110.

[0077] Under the action of a Ni-based catalyst (250-350 ℃, approximately 1.5-2.5 MPa), the reaction CO2 + 4H2 = CH4 + 2H2O is completed, with a CO2 conversion rate of 96.5%. The main components of the product gas after the reaction are 44.3 vol.% CH4, 53.6 vol.% H2O, and 2.0 vol.% CO2. After two-stage heat exchange (second heat exchanger 303 and fifth heat exchanger 305) and gas-liquid separation, approximately 126.4 tons / day of recycle gas (approximately 95 vol.% CH4 and approximately 5 vol.% CO2) is obtained. This recycle gas is returned to the pyrolysis reactor for pyrolysis.

[0078] 3. High-temperature steam power generation and heat recovery The steam generated by the medium water is pressurized and heated to 8 MPa and 500 °C, with a flow rate of approximately 500 tons / day, and used in the heat-to-power conversion power generation system 111. Based on a power generation efficiency of approximately 80%, it can generate approximately 14.6 MW of electricity.

[0079] 4. Net CO2 emissions / reduction effect In this process, 183.3 tons / day of CO2 is used for the methanation reaction, resulting in a CO2 emission reduction of 183.3 tons / day. Burner 103 emits 44.5 tons / day of CO2. Therefore, the net CO2 emission reduction is 138.8 tons / day.

[0080] In addition, this process utilizes high-temperature steam to generate 14.6 MW of electricity. If the same amount of electricity were generated by burning natural gas, it would require CO2 emissions of 118.2 tons per day. Based on this calculation, the CO2 emission reduction for the entire process is approximately 257 tons per day.

[0081] Table 1. Energy / Material / Thermal Balance Table Example 2 Figure 2 The general structure of the carbon sequestration and power generation system coupled with carbon dioxide methanation and methane cracking in this embodiment is shown in a simplified structural diagram. The difference between this embodiment and Embodiment 1 is that the gas outlet 18 of the gas-liquid separator is connected to the first inlet 11 via a fourth heat exchanger 304, and the first outlet 12 is connected to the second inlet 15 sequentially via a gas-solid separation device 116, a first heat exchanger 302, and a fourth heat exchanger 304, so that the residual heat from the bubbling tower reactor 102 after being cooled by the first heat exchanger 302 is used to preheat the gas to be introduced into the first inlet 11. The rest is the same as in Embodiment 1.

[0082] The carbon sequestration and methane cracking coupled carbon fixation power generation method in this embodiment uses a molten medium catalyst to catalyze the cracking of methane to produce hydrogen and solid carbon materials. The hydrogen produced by methane cracking is used in the Sabatier reaction to produce methane and water. The methane produced in the Sabatier reaction is then used for cracking to produce hydrogen and solid carbon materials. The heat released by the Sabatier reaction and / or the heat released after the methane cracking reaction is endothermic is used to generate electricity in a heat-to-work conversion power generation system. The molten medium catalyst is a molten metal, a molten alloy, a molten salt, or a composite system of molten metal / alloy and molten salt. Specifically, the system described in this embodiment includes the following steps: S1. The hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor 102 are transferred to the gas-solid separation device 116, along with some molten medium catalyst and methane. Part of the gas separated by the gas-solid separation device 116 is cooled by heat exchange in the first heat exchanger 302 and the fourth heat exchanger 304, and then enters the methanation reactor 110 together with the carbon dioxide transported by the carbon dioxide inlet pipe 109 to undergo the Sabatier reaction. The other part is cooled by heat exchange in the first heat exchanger 302 and then enters the burner 103 for combustion to provide heat for the methane cracking reaction. The carbon dioxide transported by the carbon dioxide inlet pipe 109 is preheated by heat exchange in the fifth heat exchanger 305. The methane and water obtained from the S2 and Sabatier reactions are cooled by heat exchangers 303 and 305 respectively before entering the gas-liquid separator 113. The gas separated by the gas-liquid separator 113 enters the bubble column reactor 102 via the fourth heat exchanger 304 to participate in the methane cracking reaction. The medium water in the first heat exchanger 302, the second heat exchanger 303 and the third heat exchanger 301 is heated by heat exchange and used to generate electricity in the heat-to-work power generation system 111. The medium water in the methanation reactor 110 absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work power generation system 111. S3. The flue gas generated by the burner 103 is cooled by heat exchange in the third heat exchanger 301, and the heat is used to heat the medium water in the third heat exchanger 301 in step S2. The electrical energy generated by the heat-to-power conversion power generation system 111 is used to heat the methane cracking reaction in step S1.

[0083] Example 3 Figure 3The general structure of the carbon sequestration and methane cracking coupled carbon sequestration power generation system of this embodiment is shown in a simplified structural diagram. The difference between this embodiment and Embodiment 1 is that the first outlet 12 is connected to the inlet 31 of the gas-solid separation device via a first heat exchanger 302, and the gas outlet 32 ​​of the gas-solid separation device is connected to the second inlet 15. That is, the material flowing out of the first outlet 12 undergoes heat exchange before entering the gas-solid separation device 116 for subsequent processing, instead of entering the gas-solid separation device 116 first to separate the gas before heat exchange and subsequent processing as in Embodiment 1. The rest is the same as Embodiment 1.

[0084] The carbon sequestration and methane cracking coupled carbon fixation power generation method in this embodiment uses a molten medium catalyst to catalyze the cracking of methane to produce hydrogen and solid carbon materials. The hydrogen produced by methane cracking is used in the Sabatier reaction to produce methane and water. The methane produced in the Sabatier reaction is then used for cracking to produce hydrogen and solid carbon materials. The heat released by the Sabatier reaction and / or the heat released after the methane cracking reaction is endothermic is used to generate electricity in a heat-to-work conversion power generation system. The molten medium catalyst is a molten metal, a molten alloy, a molten salt, or a composite system of molten metal / alloy and molten salt. Specifically, the system described in this embodiment includes the following steps: S1. The hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor 102 are cooled by heat exchange in the first heat exchanger 302 and then transferred to the gas-solid separation device 116, while carrying in some molten medium catalyst and methane. Part of the gas separated by the gas-solid separation device 116 enters the methanation reactor 110 together with the carbon dioxide transported by the carbon dioxide inlet pipe 109 to undergo the Sabatier reaction, and the other part enters the burner 103 for combustion to provide heat for the methane cracking reaction. The carbon dioxide transported by the carbon dioxide inlet pipe 109 is preheated by heat exchange in the fifth heat exchanger 305. The methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second heat exchanger 303 and the fifth heat exchanger 305 before entering the gas-liquid separator 113. The gas separated by the gas-liquid separator 113 enters the bubble column reactor 102 through the fourth heat exchanger 304 to participate in the methane cracking reaction. The medium water in the first heat exchanger 302, the second heat exchanger 303 and the third heat exchanger 301 is heated and used to generate electricity in the heat-to-work power generation system 111. The medium water in the methanation reactor 110 absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work power generation system 111. S3. The flue gas generated by the burner 103 is cooled by heat exchange in the third heat exchanger 301 and the fourth heat exchanger 304. The heat is used to heat the medium water in the third heat exchanger 301 in step S2 and to preheat the gas in the methane cracking reaction in step S1. The electrical energy generated by the heat-power conversion power generation system 111 is used to heat the methane cracking reaction in step S1.

[0085] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Modifications and improvements to the present invention are possible without exceeding the concept and scope defined by the claims. Therefore, the content of the embodiments in this specification should not be construed as a limitation of the present invention.

Claims

1. A carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking, characterized in that, It includes a methane cracking unit, a methanation reaction unit, and an energy recovery unit; The methane cracking unit includes a bubble column reactor (102) and a gas-solid separation device (116); the bubble column reactor (102) is used for methane cracking to produce hydrogen and solid carbon materials, and is provided with a first inlet (11) and a first outlet (12), and is filled with molten medium catalyst; the first outlet (12) is connected to the feed port (31) of the gas-solid separation device. The methanation reaction unit includes a methanation reactor (110), a gas-liquid separator (113), and a carbon dioxide inlet pipe (109). The methanation reactor (110) uses hydrogen and carbon dioxide as reaction raw materials to catalytically produce methane. It is equipped with a second inlet (15) and a second outlet (16) and is filled with a catalyst for the methanation reaction. The second inlet (15) is connected to the carbon dioxide inlet pipe (109). The gas outlet (18) of the gas-liquid separator is connected to the first inlet (11). The energy recovery unit includes a heat exchanger and a heat-to-work power generation system (111); the heat exchanger includes a first heat exchanger (302) and a second heat exchanger (303); the first outlet (12) is connected to the second inlet (15) through the first heat exchanger (302), and the first heat exchanger (302) is also connected to the heat-to-work power generation system (111) to exchange the heat flowing out of the bubble column reactor (102) with the heat-to-work power generation system (111) for power generation; the second outlet (16) is connected to the feed inlet (17) of the gas-liquid separator through the second heat exchanger (303), and the second heat exchanger (303) is also connected to the heat-to-work power generation system (111) to exchange the heat flowing out of the second outlet (16) with the heat-to-work power generation system (111) for power generation.

2. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 1, characterized in that, The methanation reactor (110) is connected to the heat-to-work power generation system (111) so that the heat released by the methanation reaction heats the water flowing through the methanation reactor (110) to form steam, which is then introduced into the heat-to-work power generation system (111) for power generation; the heat-to-work power generation system (111) includes one or more of a steam turbine generator set and an organic Rankine cycle generator set; the methanation reactor (110) is selected from a fixed bed reactor and / or a fluidized bed reactor.

3. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 1, characterized in that, The first outlet (12) is connected to the second inlet (15) through the first heat exchanger (302). Specifically, the first outlet (12) is connected to the feed port (31) of the gas-solid separation device, and the gas outlet (32) of the gas-solid separation device is connected to the second inlet (15) through the first heat exchanger (302).

4. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 1, characterized in that, The first outlet (12) is connected to the second inlet (15) through the first heat exchanger (302). Specifically, the first outlet (12) is connected to the feed port (31) of the gas-solid separation device through the first heat exchanger (302), and the gas outlet (32) of the gas-solid separation device is connected to the second inlet (15).

5. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 1, characterized in that, The methane cracking unit also includes a burner (103); the burner (103) is connected to the bubble column reactor (102) and is used to heat the bubble column reactor (102); the heat exchanger also includes a third heat exchanger (301); the flue gas outlet (107) of the burner is connected to the third heat exchanger (301), and the third heat exchanger (301) is connected to the heat-to-power conversion power generation system (111) so that the heat flowing out of the flue gas outlet (107) of the burner is exchanged to the heat-to-power conversion power generation system (111) for power generation.

6. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 5, characterized in that, The heat exchanger also includes a fourth heat exchanger (304); the gas outlet (18) of the gas-liquid separator is connected to the first inlet (11) through the fourth heat exchanger (304), and the flue gas outlet (107) of the burner is connected to the fourth heat exchanger (304) through the third heat exchanger (301) so as to use the waste heat of the flue gas in the fourth heat exchanger (304) for preheating the gas to flow into the first inlet (11).

7. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 5, characterized in that, The heat exchanger also includes a fourth heat exchanger (304); the gas outlet (18) of the gas-liquid separator is connected to the first inlet (11) through the fourth heat exchanger (304), and the first outlet (12) is connected to the second inlet (15) in sequence through the gas-solid separation device (116), the first heat exchanger (302) and the fourth heat exchanger (304) so ​​as to use the residual heat of the bubbling tower reactor (102) after being cooled by the first heat exchanger (302) for the preheating of the gas to flow into the first inlet (11).

8. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 6 or 7, characterized in that, The methane cracking unit also includes a natural gas inlet pipe (101); the natural gas inlet pipe (101) is also connected to the first inlet (11) through the fourth heat exchanger (304), so that the natural gas transported by the natural gas inlet pipe (101) can be preheated in the fourth heat exchanger (304).

9. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 6 or 7, characterized in that, The methanation reaction unit also includes a compressor (401); the gas outlet (18) of the gas-liquid separator is connected to the first inlet (11) in sequence through the compressor (401) and the fourth heat exchanger (304), so that the gas flowing out of the gas outlet (18) of the gas-liquid separator is compressed by the compressor (401), and then preheated by the fourth heat exchanger (304) before entering the bubble column reactor (102).

10. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 5, characterized in that, The fuel inlet (13) of the burner is connected to the gas outlet (32) of the gas-solid separator to transport the gas flowing out of the gas outlet (32) of the gas-solid separator to the burner (103); the burner (103) is provided with an additive inlet (14) for introducing oxygen and / or air.

11. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 10, characterized in that, The fuel inlet (13) of the burner is connected to the gas outlet (32) of the gas-solid separation device through the first heat exchanger (302) so as to transport the gas cooled by heat exchange to the burner (103).

12. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 5, characterized in that, The methane cracking unit also includes a solid carbon collector (104); the solid carbon collector (104) is connected to the solid carbon outlet (33) of the gas-solid separation device; the methanation reaction unit also includes a condensate pump (114); the condensate pump (114) is connected to the liquid outlet (19) of the gas-liquid separator and is used to pump the liquid flowing out of the liquid outlet (19) of the gas-liquid separator into downstream equipment.

13. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 12, characterized in that, The downstream equipment includes a water purification device; the liquid outlet (19) of the gas-liquid separator is connected to the heat-to-power conversion power generation system (111) in sequence through the condensate pump (114), the water purification device and the first heat exchanger (302), with purified water as the medium water of the first heat exchanger (302); The liquid outlet (19) of the gas-liquid separator is also connected to the heat-to-power conversion power generation system (111) in sequence through the condensate pump (114), the water purification device and the second heat exchanger (303), with the purified water as the medium water of the second heat exchanger (303); The heat exchanger also includes a third heat exchanger (301); the flue gas outlet (107) of the burner is connected to the third heat exchanger (301), and the third heat exchanger (301) is connected to the heat-to-power conversion power generation system (111) so that the heat flowing out of the flue gas outlet (107) of the burner is transferred to the heat-to-power conversion power generation system (111) for power generation; the liquid outlet (19) of the gas-liquid separator is also connected to the heat-to-power conversion power generation system (111) in sequence through the condensate pump (114), the water purification device and the third heat exchanger (301), so that the purified water is used as the medium water of the third heat exchanger (301); The methanation reactor (110) is connected to the heat-to-work power generation system (111) so that the heat released by the methanation reaction heats the water vapor formed by the medium water flowing through the methanation reactor (110) and introduces it into the heat-to-work power generation system (111) for power generation; the liquid outlet (19) of the gas-liquid separator is also connected to the heat-to-work power generation system (111) in sequence through the condensate pump (114), the water purification device and the methanation reactor (110), so that the purified water is used as the medium water of the methanation reactor (110).

14. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in claim 1, characterized in that, The heat exchanger also includes a fifth heat exchanger (305); the second outlet (16) is connected to the inlet (17) of the gas-liquid separator in sequence through the second heat exchanger (303) and the fifth heat exchanger (305), and the second inlet (15) is connected to the carbon dioxide inlet pipe (109). The fifth heat exchanger (305) is provided on the carbon dioxide inlet pipe (109), so that the product flowing out of the second outlet (16) enters the gas-liquid separator (113) for separation after being cooled by two stages of heat exchange, and the heat flowing out of the second outlet (16) is transferred to the heat-power conversion power generation system (111) for power generation and preheating of the carbon dioxide in the carbon dioxide inlet pipe (109).

15. The carbon sequestration power generation system coupled with carbon dioxide methanation and methane cracking as described in any one of claims 1-7 or 10-14, characterized in that, The heat-to-power conversion power generation system (111) is electrically connected to the bubble column reactor (102), and the electrical energy generated by the heat-to-power conversion power generation system (111) can be used for methane cracking heating.

16. A carbon sequestration power generation method coupling carbon dioxide methanation and methane cracking, characterized in that, The system described in claim 1 is used; a molten medium catalyst is used to catalyze the cracking of methane to produce hydrogen and solid carbon materials; the hydrogen produced by the cracking of methane is used in the Sabatier reaction to produce methane and water; the methane produced by the Sabatier reaction is then used for cracking to produce hydrogen and solid carbon materials; the heat released by the Sabatier reaction and / or the heat released after the methane cracking reaction is endothermic is used for the heat-to-work conversion power generation system to generate electricity.

17. The carbon sequestration power generation method coupled with carbon dioxide methanation and methane cracking as described in claim 16, characterized in that, The electrical energy generated by the heat-to-work conversion power generation system (111) is used for methane cracking heating or for other occasions requiring electrical energy; the heat released by the Sabatier reaction is also used for preheating the reactant carbon dioxide of the Sabatier reaction.

18. The carbon sequestration and power generation method coupled with carbon dioxide methanation and methane cracking as described in claim 16, characterized in that, The molten medium catalyst is a molten metal, a molten alloy, a molten salt, or a composite system of molten metal / alloy and molten salt; the catalyst for the Sabatier reaction is a Ni-based methanation catalyst.

19. The carbon sequestration power generation method coupled with carbon dioxide methanation and methane cracking as described in claim 16, characterized in that, The methane cracking unit also includes a burner (103); the burner (103) is connected to the bubble column reactor (102) and is used to supply heat to the bubble column reactor (102); The heat exchanger further includes a third heat exchanger (301), a fourth heat exchanger (304), and a fifth heat exchanger (305); the flue gas outlet (107) of the burner is connected to the third heat exchanger (301), and the third heat exchanger (301) is connected to the heat-to-power conversion power generation system (111), so that the heat flowing out of the flue gas outlet (107) of the burner is transferred to the heat-to-power conversion power generation system (111) for power generation; the gas outlet (18) of the gas-liquid separator is connected to the first inlet (11) through the fourth heat exchanger (304), and the flue gas outlet (107) of the burner is connected to the fourth heat exchanger (304) through the third heat exchanger (301), so that the waste heat of the flue gas in the fourth heat exchanger (304) is used to preheat the gas to flow into the first inlet (11); the second outlet (16) is connected in sequence through the second heat exchanger (303) and the fifth heat exchanger (305). The fifth heat exchanger (305) is connected to the feed inlet (17) of the gas-liquid separator, and the second inlet (15) is connected to the carbon dioxide inlet pipe (109). The fifth heat exchanger (305) is installed on the carbon dioxide inlet pipe (109), so that the product flowing out of the second outlet (16) enters the gas-liquid separator (113) for separation after being cooled by two stages of heat exchange, and the heat flowing out of the second outlet (16) is transferred to the heat-power conversion power generation system (111) for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe (109); the first outlet (12) is connected to the second inlet (15) through the first heat exchanger (302). Specifically, the first outlet (12) is connected to the feed inlet (31) of the gas-solid separation device, and the gas outlet (32) of the gas-solid separation device is connected to the second inlet (15) through the first heat exchanger (302). The method includes the following steps: S1. The hydrogen and solid carbon material generated by the methane cracking reaction in the bubble column reactor (102) are transferred to the gas-solid separation device (116), and a portion of the molten medium catalyst and methane are introduced at the same time. After the gas separated by the gas-solid separation device (116) is cooled by heat exchange in the first heat exchanger (302), a portion of it enters the methanation reactor (110) together with the carbon dioxide transported by the carbon dioxide inlet pipe (109) to undergo the Sabatier reaction, and another portion enters the burner (103) for combustion to provide heat for the methane cracking reaction. The carbon dioxide transported by the carbon dioxide inlet pipe (109) is preheated by heat exchange in the fifth heat exchanger (305). The methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second heat exchanger (303) and the fifth heat exchanger (305) before entering the gas-liquid separator (113). The gas separated by the gas-liquid separator (113) enters the bubble column reactor (102) through the fourth heat exchanger (304) to participate in the methane cracking reaction. The medium water in the first heat exchanger (302), the second heat exchanger (303), and the third heat exchanger (301) is heated and used to generate electricity in the heat-to-work conversion power generation system (111). The medium water in the methanation reactor (110) absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work conversion power generation system (111). S3. The flue gas generated by the burner (103) is cooled by heat exchange through the third heat exchanger (301) and the fourth heat exchanger (304). The heat is used to heat the medium water in the third heat exchanger (301) in step S2 and to preheat the methane cracking reaction gas in step S1. The electrical energy generated by the heat-power conversion power generation system (111) can be used to heat the methane cracking reaction in step S1.

20. The carbon sequestration and power generation method coupled with carbon dioxide methanation and methane cracking as described in claim 16, characterized in that, The methane cracking unit also includes a burner (103); the burner (103) is connected to the bubble column reactor (102) and is used to supply heat to the bubble column reactor (102); The heat exchanger further includes a third heat exchanger (301), a fourth heat exchanger (304), and a fifth heat exchanger (305); the flue gas outlet (107) of the burner is connected to the third heat exchanger (301), and the third heat exchanger (301) is connected to the heat-to-power conversion power generation system (111), so that the heat flowing out of the flue gas outlet (107) of the burner is transferred to the heat-to-power conversion power generation system (111) for power generation; the gas outlet (18) of the gas-liquid separator is connected to the first inlet (11) through the fourth heat exchanger (304), and the flue gas outlet (107) of the burner is connected to the fourth heat exchanger (304) through the third heat exchanger (301), so that the waste heat of the flue gas in the fourth heat exchanger (304) is used to preheat the gas to flow into the first inlet (11); the second outlet (16) is connected in sequence through the second heat exchanger (303) and the fifth heat exchanger (305). The fifth heat exchanger (305) is connected to the feed inlet (17) of the gas-liquid separator, and the second inlet (15) is connected to the carbon dioxide inlet pipe (109). The fifth heat exchanger (305) is installed on the carbon dioxide inlet pipe (109), so that the product flowing out of the second outlet (16) enters the gas-liquid separator (113) for separation after two stages of heat exchange and cooling, and the heat flowing out of the second outlet (16) is transferred to the heat-power conversion power generation system (111) for power generation and preheating of the carbon dioxide in the carbon dioxide inlet pipe (109); the first outlet (12) is connected to the second inlet (15) through the first heat exchanger (302). Specifically, the first outlet (12) is connected to the feed inlet (31) of the gas-solid separation device through the first heat exchanger (302), and the gas outlet (32) of the gas-solid separation device is connected to the second inlet (15). The method includes the following steps: S1. The hydrogen and solid carbon material generated by the methane cracking reaction in the bubble column reactor (102) are cooled by heat exchange in the first heat exchanger (302) and then transferred to the gas-solid separation device (116), while carrying in some molten medium catalyst and methane. Part of the gas separated by the gas-solid separation device (116) and the carbon dioxide transported by the carbon dioxide inlet pipe (109) enter the methanation reactor (110) to undergo the Sabatier reaction, and the other part enters the burner (103) for combustion to provide heat for the methane cracking reaction. The carbon dioxide transported by the carbon dioxide inlet pipe (109) is preheated by heat exchange in the fifth heat exchanger (305). The methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second heat exchanger (303) and the fifth heat exchanger (305) before entering the gas-liquid separator (113). The gas separated by the gas-liquid separator (113) enters the bubble column reactor (102) through the fourth heat exchanger (304) to participate in the methane cracking reaction. The medium water in the first heat exchanger (302), the second heat exchanger (303), and the third heat exchanger (301) is heated and used to generate electricity in the heat-to-work conversion power generation system (111). The medium water in the methanation reactor (110) absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work conversion power generation system (111). S3. The flue gas generated by the burner (103) is cooled by heat exchange through the third heat exchanger (301) and the fourth heat exchanger (304). The heat is used to heat the medium water in the third heat exchanger (301) in step S2 and to preheat the methane cracking reaction gas in step S1. The electrical energy generated by the heat-power conversion power generation system (111) is used to heat the methane cracking reaction in step S1.

21. The carbon sequestration and power generation method coupled with carbon dioxide methanation and methane cracking as described in claim 16, characterized in that, The methane cracking unit also includes a burner (103); the burner (103) is connected to the bubble column reactor (102) and is used to supply heat to the bubble column reactor (102); The heat exchanger further includes a third heat exchanger (301), a fourth heat exchanger (304), and a fifth heat exchanger (305); the flue gas outlet (107) of the burner is connected to the third heat exchanger (301), and the third heat exchanger (301) is connected to the heat-to-power conversion power generation system (111), so that the heat flowing out of the flue gas outlet (107) of the burner is transferred to the heat-to-power conversion power generation system (111) for power generation; the gas outlet (18) of the gas-liquid separator is connected to the first inlet (11) through the fourth heat exchanger (304), and the first outlet (12) is connected to the second inlet (15) in sequence through the gas-solid separation device (116), the first heat exchanger (302), and the fourth heat exchanger (304), so as to connect the bubbling tower reactor (115) to the gas-liquid separator. 02) The residual heat after being cooled by the first heat exchanger (302) is used to preheat the gas to be flowed into the first inlet (11); the second outlet (16) is connected to the feed port (17) of the gas-liquid separator in sequence through the second heat exchanger (303) and the fifth heat exchanger (305), and the second inlet (15) is connected to the carbon dioxide inlet pipe (109). The fifth heat exchanger (305) is provided on the carbon dioxide inlet pipe (109), so that the product flowing out of the second outlet (16) enters the gas-liquid separator (113) for separation after being cooled by two stages of heat exchange, and the heat flowing out of the second outlet (16) is transferred to the heat-power conversion power generation system (111) for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe (109); The method includes the following steps: S1. The hydrogen and solid carbon material generated by the methane cracking reaction in the bubble column reactor (102) are transferred to the gas-solid separation device (116), and a portion of the molten medium catalyst and methane are introduced at the same time. Part of the gas separated by the gas-solid separation device (116) is cooled by heat exchange in the first heat exchanger (302) and the fourth heat exchanger (304), and then enters the methanation reactor (110) together with the carbon dioxide transported by the carbon dioxide inlet pipe (109) to undergo the Sabatier reaction. The other part is cooled by heat exchange in the first heat exchanger (302) and then enters the burner (103) for combustion to provide heat for the methane cracking reaction. The carbon dioxide transported by the carbon dioxide inlet pipe (109) is preheated by heat exchange in the fifth heat exchanger (305). The methane and water obtained from the S2 and Sabatier reactions are cooled and exchanged in sequence through the second heat exchanger (303) and the fifth heat exchanger (305) before entering the gas-liquid separator (113). The gas separated by the gas-liquid separator (113) enters the bubble column reactor (102) through the fourth heat exchanger (304) to participate in the methane cracking reaction. The medium water in the first heat exchanger (302), the second heat exchanger (303), and the third heat exchanger (301) is heated and used to generate electricity in the heat-to-work conversion power generation system (111). The medium water in the methanation reactor (110) absorbs the heat released by the Sabatier reaction and is used to generate electricity in the heat-to-work conversion power generation system (111). S3. The flue gas generated by the burner (103) is cooled by heat exchange in the third heat exchanger (301), and the heat is used to heat the medium water in the third heat exchanger (301) in step S2; the electrical energy generated by the heat-power conversion power generation system (111) is used to heat the methane cracking reaction in step S1.

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