Carbon dioxide methanation coupled with methane cracking for carbon capture and power generation system and method

Abstract

The present disclosure 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. The method uses a molten medium catalyst to catalyze methane cracking to produce hydrogen and solid carbon material; the hydrogen produced by methane cracking is used for Sabatier reaction to generate methane and water; the methane generated by Sabatier reaction is used for hydrogen production and solid carbon material; the heat released by Sabatier reaction and / or the heat discharged after the endothermic methane cracking reaction is used for power generation by a heat power conversion power generation system. The present disclosure solves the problem of catalyst carbon deposition and deactivation through process innovation and system integration, reduces the dependence on purchased hydrogen, and realizes the step-by-step utilization of energy in the reaction process.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the field of carbon capture, utilization and storage (CCUS) technology, and relates to a carbon dioxide (CO2) methanation and methane cracking coupled carbon fixation power generation system and method. An indirect conversion path is coupled through a CO2 methanation reaction and a methane catalytic cracking reaction, and an integrated process and system for power generation using high-temperature steam generated by methanation exothermic. BACKGROUND

[0002] In the face of 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 and transport it to oil and gas fields or deep sea sites 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 storage still faces problems such as high technical difficulty, high cost, and poor economic efficiency, which restrict its large-scale popularization and application. Therefore, developing efficient CO2 conversion technology has become a top priority. Current CO2 direct conversion pathways mainly include direct thermal cracking and electrochemical reduction. Direct thermal cracking requires heating CO2 to above 2000°C (CO2 = C + O2, ΔH = +293 kJ / mol), which is extremely energy-intensive and difficult to industrialize; electrochemical reduction can be carried out at low temperatures, but has problems such as low electrolysis efficiency and short electrode life.

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

[0004] However, for the technical route of CO2 methanation combined with methane cracking, there are still several bottleneck problems in the existing technology:

[0005] Firstly, in the methane cracking stage, the deactivation of solid catalysts due to carbon deposition and the low heat transfer efficiency restrict the continuous production. The existing methane catalytic cracking technology mostly uses fixed bed reactors for methane cracking, and its core defects are: (1) the solid catalysts are quickly deactivated due to carbon deposition, and need to be regenerated or replaced frequently, affecting continuous production; (2) the heat transfer efficiency of the reactor is low, and the amplification effect is significant. Although the composite metal oxide catalyst reported in patent CN119857489A improves the methane conversion rate, the problem of catalyst life caused by carbon deposition still needs to be solved. In view of the regeneration problem of catalyst carbon deposition, the existing technology CN104998654A discloses a nickel-based catalyst, its preparation method and a method for producing hydrogen by catalytic cracking of methane. The method integrates a cracking reactor, a settler, a regenerator, a regenerated inclined pipe and a spent inclined pipe. The deactivated catalyst is regenerated by oxidation with an oxygen source in the regenerator and then returned to the reactor. During the regeneration process, the reactor is in a catalyst-free state, so it belongs to a batch process, which reduces the utilization efficiency of the reactor. At the same time, the introduction of oxygen in the regeneration process poses a safety risk and also poses a problem of carbon oxide emissions. The existing technology CN119346011A reports a catalyst continuous circulation regeneration methane catalytic cracking hydrogen production device and hydrogen production system. The catalyst is regenerated by a steam reforming regeneration reactor. Although it avoids the safety hazards brought by the introduction of oxygen, it ultimately leads to additional equipment costs and CO2 emissions.

[0006] Secondly, in terms of system integration, energy utilization efficiency is a problem that is generally overlooked. Compared with independent methane cracking and methanation reactions, there are few reports on coupling the two, and even fewer mention of the energy utilization efficiency of the integrated system. The high-temperature heat required for methane cracking and the large amount of reaction heat released by the methanation reaction are not effectively recovered and utilized, which will increase the energy consumption of the entire system.

[0007] Some patents / systems propose to combine Sabatier reaction with downstream cracking reaction, such as two steps in series in life support system, closed environment or space application (US10486967): after CO2 methanation, CH4 is cracked to produce hydrogen for hydrogen source of CO2 methanation, and water produced by methanation reaction is used to produce oxygen for life support by electrolysis of water, and hydrogen produced by electrolysis of water can also be used as hydrogen source for methanation reaction. Such design aims to recycle oxygen in closed system to maintain life, which is not suitable for large-scale application of CO2 carbon sequestration. In addition, other existing schemes usually first methanize CO2, then crack the obtained methane, or use methanation for heat release, and heat recovery for preheating of cracking reaction, rather than a complete closed-loop process of "cracking natural gas to produce hydrogen, using the hydrogen produced by cracking as hydrogen source for CO2 methanation reaction, and cracking the generated methane; meanwhile, high-grade waste heat is used in the form of high-temperature steam for power generation, and low-grade waste heat is used for preheating of raw gas". Although some existing technologies mention exothermic reactions and waste heat recovery (for example, for preheating of feed or maintaining reaction temperature), there is no mention of using high-temperature steam produced by methanation for power generation, and coupling power generation with the heat required for the cracking step. Patent CN215249587U discloses a carbon dioxide resource disposal system, which proposes to use hydrogen produced by electrolysis of water for CO2 methanation reaction, and the obtained methane is converted into hydrogen and solid carbon by a thermal cracking device. The patent uses hydrogen produced by electrolysis of water, which is currently considered to have high hydrogen source cost and is not suitable for large-scale production.

[0008] Therefore, it is of great significance to develop a CO2 indirect conversion system that can solve the problems of catalyst deactivation and heat management and realize energy cascade utilization. SUMMARY

[0009] To solve at least one of the above problems, the present disclosure provides a carbon dioxide methanation and methane cracking coupled carbon sequestration power generation system, comprising a methane cracking unit, a methanation reaction unit and an energy recovery unit;

[0010] The methane cracking unit comprises a bubble column reactor and a gas-solid separation device; the bubble column reactor is used for methane cracking to produce hydrogen and solid carbon material, and is provided with a first inlet and a first outlet and is filled with a molten medium catalyst inside; the first outlet is connected to the feed inlet of the gas-solid separation device;

[0011] The methanation reaction unit comprises 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, and is provided with a second inlet and a second outlet and is filled with a methanation catalyst inside; 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;

[0012] The energy recovery unit comprises a heat exchanger and a heat power conversion power generation system; the heat exchanger comprises 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 further connected to the heat power conversion power generation system, so that the heat of the bubbling tower reactor is exchanged to the heat power conversion 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 further connected to the heat power conversion power generation system, so that the heat of the second outlet is exchanged to the heat power conversion power generation system for power generation.

[0013] In some embodiments, the methanation reactor is connected to the heat power conversion power generation system, so that the heat of the methanation reaction is used to heat the water vapor formed by the medium water flowing through the methanation reactor (i.e. water is used as a medium for heat transfer), and the water vapor is introduced into the heat power conversion power generation system for power generation; the heat power conversion power generation system comprises 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.

[0014] In some embodiments, the first outlet is connected to the second inlet through 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 through the first heat exchanger.

[0015] In some embodiments, the first outlet is connected to the second inlet through the first heat exchanger, specifically, the first outlet is connected to the feed inlet of the gas-solid separation device through the first heat exchanger, and the gas outlet of the gas-solid separation device is connected to the second inlet.

[0016] In some embodiments, the methanation unit further comprises a combustor; the combustor is connected to the bubbling tower reactor for heating the bubbling tower reactor; the heat exchanger further comprises a third heat exchanger; the flue gas outlet of the combustor is connected to the third heat exchanger, and the third heat exchanger is further connected to the heat power conversion power generation system, so that the heat of the flue gas outlet of the combustor is exchanged to the heat power conversion power generation system for power generation.

[0017] In some embodiments, the heat exchanger further comprises 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 combustor 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 preheating the gas to be flowed into the first inlet.

[0018] In some embodiments, the heat exchanger further comprises 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 through the gas-solid separation device, the first heat exchanger and the fourth heat exchanger in sequence, so as to use the waste heat of the effluent of the bubble column reactor after heat exchange and cooling in the first heat exchanger for preheating the gas to be flowed into the first inlet.

[0019] In some embodiments, the methane cracking unit further comprises a natural gas inlet pipe; the natural gas inlet pipe is also connected to the first inlet through the fourth heat exchanger, so that the natural gas delivered by the natural gas inlet pipe can be preheated in the fourth heat exchanger.

[0020] In some embodiments, the methanation reaction unit further comprises a compressor; the gas outlet of the gas-liquid separator is connected to the first inlet through the compressor and the fourth heat exchanger in sequence, so that the gas flowed out of the gas outlet of the gas-liquid separator is compressed by the compressor and then preheated by the fourth heat exchanger before entering the bubble column reactor.

[0021] In some embodiments, the fuel inlet of the combustor is connected to the gas outlet of the gas-solid separation device, so as to deliver the gas flowed out of the gas outlet of the gas-solid separation device into the combustor; the combustor is provided with an auxiliary agent inlet for introducing oxygen and / or air.

[0022] In some embodiments, the fuel inlet of the combustor is connected to the gas outlet of the gas-solid separation device through the first heat exchanger, so as to deliver the gas after heat exchange and cooling into the combustor.

[0023] In some embodiments, the heat exchanger further comprises a fifth heat exchanger; the second outlet is connected to the feed inlet of the gas-liquid separator through the second heat exchanger and the fifth heat exchanger in sequence, and the second inlet is connected to the carbon dioxide inlet pipe, and the fifth heat exchanger is arranged on the carbon dioxide inlet pipe, so that the product flowed out of the second outlet enters the gas-liquid separator after two-stage heat exchange and cooling, and the heat of the second outlet is exchanged to the heat power conversion and power generation system for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe.

[0024] In some embodiments, the methane cracking unit further comprises a solid carbon collector; the solid carbon collector is connected to the solid carbon outlet of the gas-solid separation device; the methanation reaction unit further comprises a condensate pump; the condensate pump is connected to the liquid outlet of the gas-liquid separator, and is used for pumping the liquid flowed out of the liquid outlet of the gas-liquid separator into downstream equipment.

[0025] In some embodiments, the downstream device comprises 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 purified water as the medium water of the first heat exchanger.

[0026] 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 purified water as the medium water of the second heat exchanger.

[0027] The heat exchanger further comprises a third heat exchanger; the flue gas outlet of the combustor is connected to the third heat exchanger, which is in turn connected to the heat-to-power conversion power generation system, so that the heat from the flue gas outlet of the combustor is used to heat 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.

[0028] The methanation reactor is connected to the heat-to-power conversion power generation system, so that the heat from the methanation reaction is used to heat the water vapor formed by the medium water flowing through the methanation reactor, which is introduced into 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 methanation reactor, with purified water as the medium water of the methanation reactor. The addition of the water purification device increases the operating cost, but it still has certain economic benefits when operating at sea or on islands. Therefore, in the application scenario where fresh water resources are lacking, a water purification device can be introduced to recycle the water generated in the methanation reactor.

[0029] In some embodiments, the heat-to-power conversion power generation system is electrically connected to the bubble column reactor, and the electrical energy obtained by the heat-to-power conversion power generation system can be used for methane cracking heating.

[0030] The present disclosure also provides a carbon dioxide methanation and methane cracking coupled carbon sequestration power generation method, which uses the system as described above; a molten medium catalyst is used to catalyze methane cracking to produce hydrogen and solid carbon material; the hydrogen produced by methane cracking is used for Sabatier reaction to generate methane and water; the methane generated by Sabatier reaction is used for hydrogen production by cracking and solid carbon material; the heat released by Sabatier reaction and / or the heat released after the endothermic methane cracking reaction is used for heat-to-power conversion power generation system power generation.

[0031] In some embodiments, the electricity generated by the heat conversion power generation system is used for heating of the methane cracking, or for other occasions requiring electricity; the heat released by the Sabatier reaction is also used for preheating of the carbon dioxide reactant of the Sabatier reaction.

[0032] In some embodiments, the molten medium catalyst is a molten metal, or a molten alloy, or a molten salt, or a molten metal / alloy-salt composite system; the catalyst for the Sabatier reaction is a Ni-based methanation catalyst.

[0033] In some embodiments, the methane cracking unit further comprises a combustor; the combustor is connected to the bubble column reactor for heating the bubble column reactor; the heat exchanger further comprises a third heat exchanger, a fourth heat exchanger and a fifth heat exchanger; the flue gas outlet of the combustor is connected to the third heat exchanger, which is in turn connected to the heat conversion power generation system, so that the heat from the flue gas outlet of the combustor is used for power generation of the heat conversion power generation system; 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 combustor is connected to the fourth heat exchanger through the third heat exchanger, so that the residual heat of the flue gas in the fourth heat exchanger is used for preheating of the gas to be flowed into the first inlet; the second outlet is connected to the feed inlet of the gas-liquid separator through the second heat exchanger and the fifth heat exchanger in sequence, and the second inlet is connected to the carbon dioxide inlet pipe, and the fifth heat exchanger is arranged on the carbon dioxide inlet pipe, so that the product flowed out of the second outlet is cooled by two-stage heat exchange and then enters the gas-liquid separator for separation, and the heat from the second outlet is used for power generation of the heat conversion power generation system and preheating of the carbon dioxide in the carbon dioxide inlet pipe; the first outlet is connected to the second inlet through 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 through the first heat exchanger.

[0034] The method comprises the following steps:

[0035] S1, the hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor are transported to the gas-solid separation device, while part of the molten medium catalyst and methane are brought in; the gas separated by the gas-solid separation device is cooled by heat exchange through the first heat exchanger, and part of it is mixed with the carbon dioxide transported by the carbon dioxide inlet pipe and then enters the methanation reactor to undergo the Sabatier reaction, and the other part enters the combustor to be combusted for heating of the methane cracking reaction; the carbon dioxide transported by the carbon dioxide inlet pipe is preheated by heat exchange through the fifth heat exchanger;

[0036] S2, the methane and water obtained from the Sabatier reaction are sequentially subjected to heat exchange and cooling in the second heat exchanger and the fifth heat exchanger, and then enter the gas-liquid separator; the gas obtained from the gas-liquid separator is subjected to heat exchange in the fourth heat exchanger, and then enters the bubble column reactor to participate in the methane cracking reaction; the medium water of the first heat exchanger, the second heat exchanger and the third heat exchanger is subjected to heat exchange and heating to generate power in the heat power conversion power generation system; the medium water of the methanation reactor absorbs the heat released from the Sabatier reaction to generate power in the heat power conversion power generation system;

[0037] S3, the flue gas generated by the combustor is subjected to heat exchange and cooling in the third heat exchanger and the fourth heat exchanger, and the heat is used for heating the medium water of the third heat exchanger in step S2 and preheating the methane cracking reaction gas in step S1, respectively; the electric energy generated by the heat power conversion power generation system is used for heating the methane cracking reaction in step S1.

[0038] In some embodiments, the methane cracking unit further comprises a combustor; the combustor is connected to the bubble column reactor to provide heat for the bubble column reactor; the heat exchanger further comprises a third heat exchanger, a fourth heat exchanger and a fifth heat exchanger; the flue gas outlet of the combustor is connected to the third heat exchanger, and the third heat exchanger is connected to the heat power conversion power generation system, so that the heat of the flue gas outlet of the combustor is used for heat exchange to generate power in the heat power conversion power generation system; 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 combustor 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 preheating the gas to be flowed into the first inlet; the second outlet is connected to the feed inlet of the gas-liquid separator through 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 arranged on the carbon dioxide inlet pipe, so that the products flowed out of the second outlet are subjected to two-stage heat exchange and cooling, and then enter the gas-liquid separator for separation, and the heat of the products flowed out of the second outlet is used for heat exchange to generate power in the heat power conversion power generation system and preheat the carbon dioxide in the carbon dioxide inlet pipe; the first outlet is connected to the second inlet through the first heat exchanger, specifically, the first outlet is connected to the feed inlet of the gas-solid separation device through the first heat exchanger, and the gas outlet of the gas-solid separation device is connected to the second inlet;

[0039] The method comprises the following steps:

[0040] S1, hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor are transferred to the gas-solid separation device after heat exchange and cooling by the first heat exchanger, while part of the molten medium catalyst and methane are brought in; part of the gas obtained by the gas-solid separation device enters the methanation reactor together with the carbon dioxide transported by the carbon dioxide inlet pipe to undergo Sabatier reaction, and the other part enters the combustor to be burned to provide heat for the methane cracking reaction; the carbon dioxide transported by the carbon dioxide inlet pipe is preheated by heat exchange and heating by the fifth heat exchanger;

[0041] S2, the methane and water obtained by Sabatier reaction are sequentially cooled by heat exchange by the second heat exchanger and the fifth heat exchanger and then enter the gas-liquid separator; the gas obtained by separation by the gas-liquid separator enters the bubble column reactor by the fourth heat exchanger to participate in the methane cracking reaction; the medium water of the first heat exchanger, the second heat exchanger and the third heat exchanger is heated by heat exchange to generate electricity in the heat power conversion power generation system; the medium water of the methanation reactor absorbs the heat released by Sabatier reaction to generate electricity in the heat power conversion power generation system;

[0042] S3, the flue gas produced by the combustor is cooled by heat exchange by the third heat exchanger and the fourth heat exchanger, and the heat is used for heating the medium water of the third heat exchanger in step S2 and preheating the methane cracking reaction gas in step S1, respectively; the electric energy generated by the heat power conversion power generation system is used for heating the methane cracking reaction in step S1.

[0043] In some embodiments, the methane cracking unit further comprises a combustor; the combustor is connected with the bubble column reactor for heating the bubble column reactor; the heat exchanger further comprises a third heat exchanger, a fourth heat exchanger and a fifth heat exchanger; the flue gas outlet of the combustor is connected with the third heat exchanger, and the third heat exchanger is connected with the heat power conversion power generation system, so that the heat of the flue gas outlet of the combustor is exchanged to the heat power conversion power generation system for power generation; the gas outlet of the gas-liquid separator is connected with the first inlet through the fourth heat exchanger, and the first outlet is connected with the second inlet through the gas-solid separation device, the first heat exchanger and the fourth heat exchanger in sequence, so that the waste heat of the bubble column reactor after being exchanged and cooled by the first heat exchanger is used for preheating the gas to be flowed into the first inlet; the second outlet is connected with the feed inlet of the gas-liquid separator through the second heat exchanger and the fifth heat exchanger in sequence, and the second inlet is connected with the carbon dioxide inlet pipe, and the fifth heat exchanger is arranged on the carbon dioxide inlet pipe, so that the product flowed out of the second outlet is separated in the gas-liquid separator after being exchanged and cooled by two stages, and the heat of the second outlet is exchanged to the heat power conversion power generation system for power generation and preheating the carbon dioxide in the carbon dioxide inlet pipe;

[0044] The method comprises the following steps:

[0045] S1, the hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor are transported to the gas-solid separation device, and part of the molten medium catalyst and methane are brought in; part of the gas separated by the gas-solid separation device is exchanged and cooled by the first heat exchanger and the fourth heat exchanger, and then enters the methanation reactor together with the carbon dioxide transported by the carbon dioxide inlet pipe to generate Sabatier reaction, and the other part is exchanged and cooled by the first heat exchanger and then enters the combustor for combustion to provide heat for the methane cracking reaction; the carbon dioxide transported by the carbon dioxide inlet pipe is exchanged and heated by the fifth heat exchanger for preheating;

[0046] S2, the methane and water generated by Sabatier reaction are exchanged and cooled by the second heat exchanger and the fifth heat exchanger in sequence and then enter the gas-liquid separator; the gas separated by the gas-liquid separator enters the bubble column reactor for methane cracking reaction through the fourth heat exchanger; the medium water of the first heat exchanger, the second heat exchanger and the third heat exchanger is exchanged and heated for power generation of the heat power conversion power generation system; the medium water of the methanation reactor absorbs the heat released by Sabatier reaction for power generation of the heat power conversion power generation system;

[0047] S3, the flue gas generated by the combustor is cooled by the third heat exchanger, and the heat is used for heating the medium water of the third heat exchanger in step S2; and the electric energy generated by the heat power conversion power generation system is used for heating in the methane cracking reaction in step S1.

[0048] The present disclosure provides a CO2 conversion system and method which can continuously, stably and efficiently operate, and has low comprehensive energy consumption. Through process innovation and system integration, the problem of catalyst deactivation due to carbon deposition is solved, the dependence on purchased hydrogen is reduced, and the cascade utilization of reaction process energy is realized.

[0049] The present disclosure has the following beneficial effects:

[0050] 1) Solve the problem of catalyst deactivation: the molten medium method (i.e., using a molten medium catalyst for methane cracking reaction) provides a new idea for this problem. The liquid molten medium (such as metal, salt) can be used as a "flowing" catalytic interface. The solid carbon material generated in the reaction will float to the surface of the molten medium catalyst due to the difference in density, thereby realizing the in-situ separation of the catalyst and the product, and fundamentally solving the problem of catalyst deactivation due to carbon deposition. The molten medium catalyst avoids the core problem of deactivation of solid catalysts due to carbon deposition, and ensures the long-term continuous and stable operation of the system.

[0051] 2) Maximize energy efficiency: through innovative heat cascade utilization (preheating, steam power generation), the operating cost is greatly reduced.

[0052] 3) High product value: the final products are solid carbon materials (such as flaky graphite or graphene nanosheets) and hydrogen, which have much higher economic value than simple carbon sequestration.

[0053] 4) Significant emission reduction effect: the conversion of CO2 into stable solid products is a technical path with negative carbon potential. For every ton of CO2 processed, 0.75 tons of CO2 equivalent can be reduced, and 0.7 tons of solid carbon material can be produced, and the steam power generation power is 80 kW (based on an efficiency of 80%).

[0054] The concept, specific structure and technical effects of the present disclosure will be further described below with reference to the accompanying drawings, so as to fully understand the purpose, features and effects of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without creative labor.

[0056] Figure 1is a structural schematic diagram of a carbon dioxide methanation and methane cracking coupled carbon sequestration power generation system of embodiment 1 of the present disclosure.

[0057] Figure 2 is a structural schematic diagram of a carbon dioxide methanation and methane cracking coupled carbon sequestration power generation system of embodiment 2 of the present disclosure.

[0058] Figure 3 is a structural schematic diagram of a carbon dioxide methanation and methane cracking coupled carbon sequestration power generation system of embodiment 3 of the present disclosure.

[0059] Reference signs:

[0060] 101: natural gas inlet pipe

[0061] 102: bubble column reactor

[0062] 103: combustor

[0063] 104: solid carbon collector

[0064] 109: carbon dioxide inlet pipe

[0065] 110: methanation reactor

[0066] 111: heat power conversion power generation system

[0067] 113: gas-liquid separator

[0068] 114: condensate pump

[0069] 115: condensate pipe

[0070] 116: gas-solid separation device

[0071] 201: first water pipe

[0072] 202: second water pipe

[0073] 203: third water pipe

[0074] 204: fourth water pipe

[0075] 205: first water vapor pipe

[0076] 206: second water vapor pipe

[0077] 207: third water vapor pipe

[0078] 208: fourth water vapor pipe

[0079] 301: third heat exchanger

[0080] 302: first heat exchanger

[0081] 303: second heat exchanger

[0082] 304: fourth heat exchanger

[0083] 305: fifth heat exchanger

[0084] 401: compressor

[0085] 11: first inlet

[0086] 12: first outlet

[0087] 13: fuel inlet of the combustor

[0088] 14: auxiliary agent inlet

[0089] 15: second inlet

[0090] 16: second outlet

[0091] 17: feed inlet of the gas-liquid separator

[0092] 18: gas outlet of the gas-liquid separator

[0093] 19: liquid outlet of the gas-liquid separator

[0094] 31: feed inlet of the gas-solid separation device

[0095] 32: gas outlet of the gas-solid separation device

[0096] 33: solid carbon outlet of the gas-solid separation device

[0097] 107: flue gas outlet of the combustor. DETAILED DESCRIPTION

[0098] For the convenience of those skilled in the art, some terms appearing in this text are explained and described.

[0099] In this text, the singular forms "one", "a", and "said" include their plural forms unless the context indicates otherwise.

[0100] In this text, unless otherwise specified, the terms "contain", "include", "have", or "comprise" mean containing the listed technical features, but also do not exclude containing other technical features.

[0101] In this text, the ordinal numbers "first", "second", etc. appearing before a component are used to distinguish the components, and are not sorted in the order of ordinal numbers.

[0102] In this text, the term "and / or" refers to any one of the three cases, for example, the three cases of A and / or B are: either A, or B, or A and B.

[0103] In the present text, the terms "connected" and "connection" can refer to both a direct connection between two components and an indirect connection between two components via one or more other components.

[0104] Example 1

[0105] Figure 1 The general structure of the carbon sequestration power generation system of the present example is shown in the form of a structural diagram. The system comprises a methane cracking unit, a methanation reaction unit and an energy recovery unit.

[0106] The methane cracking unit comprises a bubble column reactor 102, a gas-solid separation device 116, a combustor 103, a solid carbon collector 104 and a natural gas inlet pipe 101. The bubble column reactor 102 is used for producing hydrogen and solid carbon material by methane cracking, and is provided with a first inlet 11 and a first outlet 12, and is internally packed with a molten medium catalyst. The first outlet 12 is connected to the feed inlet 31 of the gas-solid separation device. The feed inlet 31 of the gas-solid separation device is located on the side of the gas-solid separation device 116, the gas outlet 33 of the gas-solid separation device is located at the top of the gas-solid separation device 116, and the solid carbon outlet 33 of the gas-solid separation device is located at the bottom of the gas-solid separation device 116.

[0107] The methanation reaction unit comprises a methanation reactor 110, a gas-liquid separator 113, a compressor 401 and a carbon dioxide inlet pipe 109. The methanation reactor 110 catalytically produces methane using hydrogen and carbon dioxide as raw materials, and is provided with a second inlet 15 and a second outlet 16, and is internally packed with a methanation catalyst. 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.

[0108] The energy recovery unit comprises a heat exchanger and a heat-to-power conversion power generation system 111. The heat exchanger comprises 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-power conversion power generation system 111 comprises a steam turbine generator set and an organic Rankine cycle generator set. For the high-grade heat source from the bubble column reactor 102 and the combustor 103, the steam turbine generator set is preferably used for energy recovery; for the medium and low-grade heat source from the methanation reactor 110, the organic Rankine cycle generator set is preferably used for energy recovery.

[0109] 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, and the gas outlet 32 of the gas-solid separation device is connected to the second inlet 15 through the first heat exchanger 302, so that the heat of the bubbling tower reactor 102 is exchanged to the steam turbine generator set for power generation.

[0110] 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 connected to the steam turbine generator set, so that the heat of the second outlet 16 is exchanged to the steam turbine generator set for power generation.

[0111] The methanation reactor 110 is connected to the organic Rankine cycle generator set, so that the heat of the methanation reaction is used to heat the water vapor formed by the medium water flowing through the methanation reactor 110, and the water vapor is introduced into the organic Rankine cycle generator set for power generation. The combustor 103 is arranged at the bottom of the bubbling tower reactor 102 (in other embodiments, it can be arranged at the side or top), which is used to supply heat for the bubbling tower reactor 102. The flue gas outlet 107 of the combustor is connected to the third heat exchanger 301, and the third heat exchanger 301 is connected to the steam turbine generator set, so that the heat of the flue gas outlet 107 of the combustor is exchanged to the steam turbine generator set for power generation.

[0112] 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 combustor 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 for preheating the gas to be flowed into the first inlet 11.

[0113] 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.

[0114] The gas outlet 18 of the gas-liquid separator is connected to the first inlet 11 through the compressor and the fourth heat exchanger 304 in sequence, so that the gas flowed 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 bubbling tower reactor 102.

[0115] The fuel inlet 13 of the combustor is connected to the gas outlet 32 of the gas-solid separation device, so that the gas flowed out of the gas outlet 32 of the gas-solid separation device is transported into the combustor 103. The combustor 103 is provided with an additive inlet 14 for introducing oxygen and / or air.

[0116] The fuel inlet 13 of the combustor is connected to the gas outlet 32 of the gas-solid separation device through the first heat exchanger 302, so that the gas cooled by heat exchange is transported into the combustor 103.

[0117] The second outlet 16 is connected to the feed inlet 17 of the gas-liquid separator in sequence through the second heat exchanger 303 and the fifth heat exchanger 305, the second inlet 15 is connected to the carbon dioxide inlet pipe 109, and the fifth heat exchanger 305 is arranged on the carbon dioxide inlet pipe 109, so that the product flowing out of the second outlet 16 is cooled by two-stage heat exchange and then enters the gas-liquid separator 113 for separation, and the heat of the product flowing out of the second outlet 16 is exchanged to the organic Rankine cycle generator set for power generation and preheating of the carbon dioxide in the carbon dioxide inlet pipe 109.

[0118] The solid carbon collector 104 is connected to the solid carbon outlet 33 of the gas-solid separation device. The methanation reaction unit further comprises a condensed water pump 114. The condensed water 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 to downstream equipment.

[0119] The heat power conversion power generation system 111 is electrically connected to the bubbling column reactor 102, and the electric energy obtained by the heat power conversion power generation system 111 is used for heating of the methane cracking or for other occasions requiring electric energy.

[0120] The embodiment also provides a carbon dioxide methanation and methane cracking coupled carbon sequestration power generation method, which uses a molten medium catalyst to catalyze methane cracking to produce hydrogen and solid carbon material; the hydrogen produced by the methane cracking is used for Sabatier reaction to generate methane and water; the methane generated by the Sabatier reaction is used for hydrogen production and solid carbon material; the heat released by the Sabatier reaction and / or the heat flowing out after the endothermic methane cracking reaction is used for heat power conversion power generation system to generate power. The molten medium catalyst is a molten metal, or a molten alloy, or a molten salt, or a molten metal / alloy and molten salt composite system. The catalyst for the Sabatier reaction is a Ni-based methanation catalyst.

[0121] Specifically, the carbon sequestration power generation method uses the system described in the embodiment, and comprises the following steps:

[0122] S1, the hydrogen and solid carbon material produced by the methane cracking reaction (the operating temperature is maintained at 900-1050℃) in the bubbling column reactor 102 are transported to the gas-solid separation device 116, while part of the molten medium catalyst and methane are brought in. After the gas separated by the gas-solid separation device 116 is cooled by heat exchange through the first heat exchanger 302, part of it is mixed with the carbon dioxide transported by the carbon dioxide inlet pipe 109 and then enters the methanation reactor 110 to undergo Sabatier reaction, and the other part enters the combustor 103 to be combusted to provide heat for the methane cracking reaction; the carbon dioxide transported by the carbon dioxide inlet pipe 109 is preheated by heat exchange through the fifth heat exchanger 305. Step S1 comprises (1) a methane cracking stage and (2) a gas-solid separation stage.

[0123] (1) Methane cracking stage:

[0124] CH4gas is preheated by the fourth heat exchanger 304 and then introduced from the bottom of the bubble column reactor 102, passing through the molten medium catalyst, to undergo a cracking reaction:

[0125] CH4= C + 2H2(ΔH = +75.6 kJ / mol)

[0126] The methane conversion rate can reach more than 70%. The methane cracking raw material (natural gas and Sabatier reaction product gas) is preheated and introduced from the bottom of the bubble column reactor 102 in the form of bubbles, and the bubbles undergo catalytic cracking reaction to generate solid carbon material and hydrogen during the rising process, which are taken out of the bubble column reactor 102 into the gas-solid separation device 116 by the gas flow.

[0127] (2) Gas-solid separation stage:

[0128] The generated solid carbon floats on the surface of the molten medium catalyst and is continuously collected by the solid carbon collector 104 from the upper end of the bubble column reactor 102 into the downstream gas-solid separation device 116; the generated H2-rich cracking gas is cooled by the first heat exchanger 302, part of the cracking gas enters the burner 103 for combustion to provide energy, and the rest is mixed with CO2 and then enters the methanation reactor 110.

[0129] S2, the methane and water obtained by the Sabatier reaction are sequentially cooled by the second heat exchanger 303 and the fifth heat exchanger 305 and then enter 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, and the liquid is condensed by the condensate pump 114 and then flows into the condensate pipe 115 for discharge. The medium water 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, is heated and turned into water vapor, and then flows into the heat power conversion power generation system 111 through the second water vapor pipe 206, the fourth water vapor pipe 208 and the first water vapor pipe 205 respectively for power generation. The medium water for heat transfer also enters the methanation reactor 110 through the third water pipe 203 to absorb the heat released by the Sabatier reaction, is heated and turned into water vapor, and then flows into the heat power conversion power generation system 111 through the third water vapor pipe 207 for power generation. Step S2 includes (3) methanation reaction stage and (4) gas-liquid separation stage.

[0130] (3) Methanation reaction stage:

[0131] CO2 and H2 are mixed in a ratio of n(H2):n(CO2)=4:1, CO2 is preheated to 200°C by using the waste heat of the cracking gas, and then enters the methanation reactor 110. Under the action of the catalyst, the Sabatier reaction occurs at 320°C and 1.5 MPa:

[0132] CO2+ 4H2= CH4+ 2H2O (ΔH = -165 kJ / mol)

[0133] The reaction conversion rate can reach more than 90%, and the methane selectivity is more than 95%.

[0134] (4) Gas-liquid separation stage:

[0135] The gas mixture after the methanation reaction first passes through a primary heat exchanger (second heat exchanger 303) to generate medium-pressure steam, which is transported to the heat power conversion power generation system 111 through the fourth steam pipe 208; the product gas then passes through a secondary heat exchanger (fifth heat exchanger 305) to use low-quality heat for preheating CO2. After that, the product gas enters the gas-liquid separator 113 for separation; the separated water (about 30-50°C) is discharged through the condensate pump 114; the dry CH4 gas (purity >95%) is pressurized by the compressor 401 and then preheated with the methane raw material transported by the natural gas inlet pipe 101 through the fourth heat exchanger 304 before entering the bubble column reactor 102.

[0136] S3, the flue gas generated by the burner 103 is cooled by the third heat exchanger 301 and the fourth heat exchanger 304, and the heat is used for heating the liquid entering the third heat exchanger 301 in step S2 and preheating the methane cracking reaction gas in step S1, respectively; the electric energy generated by the heat power conversion power generation system 111 is used for heating the methane cracking reaction in step S1. Step S3 includes (5) energy recovery stage.

[0137] (5) Energy recovery stage:

[0138] The high-temperature gas (about 980°C) at the outlet of the bubble column reactor 102 passes through the first heat exchanger 302 to generate high-temperature steam from the medium water transported by the second water pipe 202, which is transported to the heat power conversion power generation system 111 through 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) to generate high-temperature steam from the medium water transported by the first water pipe 201, which is transported to the heat power conversion power generation system 111 through the first steam pipe 205. The flue gas continues to pass through the pipeline to the second-stage heat exchanger (fourth heat exchanger 304) to preheat the raw material gas for the cracking reaction.

[0139] The heat of the methanation reaction is used to generate high temperature steam from the medium water fed by the third water pipe 203 through the heat exchange tubes in the methanation reactor 110, which is fed to the heat power conversion system 111 for power generation. The high temperature product gas generated from the reaction is used to convert the medium water fed by the fourth water pipe 204 into high temperature steam through the first heat exchanger (second heat exchanger 303), which is fed to the heat power conversion system 111 for power generation. The product gas is then used to further recover low quality heat source for the preliminary preheating of CO2 through the second heat exchanger (fifth heat exchanger 305).

[0140] The steam is used to generate power in the heat power conversion system 111, which is used to power the internal equipment or to be exported.

[0141] Test Example 1

[0142] The system and method of Example 1 are used. The process is described as follows, and the results are summarized in Table 1.

[0143] 1. Methane cracking stage

[0144] Methane is fed through the natural gas inlet pipe 101 at a rate of 126.2 tons / day and a pressure of 2.1 MPa.

[0145] The Sabatier reaction produces methane and a small amount of unreacted CO2 (about 95 vol.% CH4, about 5 vol.% CO2), i.e., recycle gas, at a rate of 126.4 tons / day and a pressure of 2 MPa.

[0146] After mixing, the total gas flow is 252.6 tons / day, which is preheated by the fourth heat exchanger 304 to a pressure of about 1.9 MPa and a temperature of about 600°C, and then enters the bubble column reactor 102 for the cracking reaction.

[0147] The methane cracking reaction product has a methane conversion rate of 75%, and generates solid carbon at a rate of 133.2 tons / day; the gas product flow is about 119.4 tons / day, which has a pressure of about 1.5 MPa and a temperature of about 320°C after passing through the first heat exchanger 302, and a composition of about 85.7% H2 and 14.3% CH4. Of this, 93.2 tons / day of the cracking gas is used for the methanation reaction, and the remaining 26.2 tons / day is depressurized (from about 1.5 MPa to about 0.02 MPa) and enters the burner 103 to provide a heat source for heating / maintaining the temperature of the bubble column reactor 102. The calculations for this test example are performed without considering the power generation of the heat power conversion system 111 to heat the bubble column reactor 102. The power generation of the heat power conversion system 111 can be used to heat the bubble column reactor 102 as needed, i.e., the methane cracking reaction can be heated by electric heating and / or burner heating.

[0148] 2. Methanation stage

[0149] The gaseous product of the methane cracking, i.e. the cracking gas (93.2 tons / day) is mixed with CO2gas 183.3 tons / day (25°C, 1.5 MPa) and fed into the methanation reactor 110.

[0150] The reaction of CO2+ 4H2= CH4+ 2H2O is completed at the presence of a Ni-based catalyst (250-350°C, about 1.5-2.5 MPa), with a CO2conversion of 96.5%, and the main components of the product gas after the reaction are 44.3 vol.% CH4, 53.6 vol.% H2O, 2.0 vol.% CO2. After the secondary heat exchange (second heat exchanger 303 and fifth heat exchanger 305) and gas-liquid separation, about 126.4 tons / day of recycle gas is obtained (about 95 vol.% CH4, about 5 vol.% CO2), which is returned to the cracking reactor for cracking.

[0151] 3. High temperature steam power generation and heat recovery

[0152] The steam generated from the medium water is pressurized and heated to 8 MPa, 500°C, with a flow rate of about 500 tons / day, and is used in the heat power conversion system 111 for power generation. Based on a power generation efficiency of about 80%, about 14.6 MW of power can be generated.

[0153] 4. Net CO2 emission / emission reduction effect

[0154] In this process, 183.3 tons / day of CO2 is used for methanation reaction, and the CO2 emission reduction is 183.3 tons / day. The amount of CO2 emitted by the burner 103 is 44.5 tons / day. Therefore, the net CO2 emission reduction is 138.8 tons / day.

[0155] In addition, the process utilizes high temperature steam power of 14.6 MW, and if the same amount of power is provided by burning natural gas, 118.2 tons / day of CO2 will be emitted. According to the calculation, the CO2 emission reduction in the entire process is about 257 tons / day.

[0156] Table 1, Energy / material / thermodynamic balance table

[0157]

[0158] Example 2

[0159] Figure 2The overall structure of the carbon sequestration power generation system of the present embodiment is shown in the form of a structural diagram. The difference between the present embodiment and embodiment 1 is that 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 through the gas-solid separation device 116, the first heat exchanger 302, and the fourth heat exchanger 304 in sequence, so as to use the waste heat of the effluent from the bubbling column reactor 102 after heat exchange and cooling in the first heat exchanger 302 for preheating of the gas to be flowed into the first inlet 11. The rest is the same as in embodiment 1.

[0160] The carbon sequestration power generation method of the present embodiment corresponds to the carbon sequestration power generation system of the present embodiment, which uses a molten medium catalyst to catalyze the methane cracking to produce hydrogen and solid carbon material; the hydrogen produced by the methane cracking is used for the Sabatier reaction to generate methane and water; the methane generated by the Sabatier reaction is used for the hydrogen production and solid carbon material; the heat released by the Sabatier reaction and / or the heat of the effluent after the endothermic methane cracking reaction is used for the heat power conversion system to generate power. The molten medium catalyst is a molten metal, or a molten alloy, or a molten salt, or a molten metal / alloy and molten salt composite system. Specifically, the system of the present embodiment comprises the following steps:

[0161] S1, the hydrogen and solid carbon material produced by the methane cracking reaction in the bubbling column reactor 102 are transported to the gas-solid separation device 116, while part of the molten medium catalyst and methane are brought in; the gas separated by the gas-solid separation device 116 is partly cooled by 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, and the other part is cooled by 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 the fifth heat exchanger 305;

[0162] S2, the methane and water obtained by the Sabatier reaction are cooled by the second heat exchanger 303 and the fifth heat exchanger 305 in sequence and then enter the gas-liquid separator 113; the gas separated by the gas-liquid separator 113 enters the bubbling column reactor 102 through the fourth heat exchanger 304 to participate in the methane cracking reaction; the medium water of the first heat exchanger 302, the second heat exchanger 303, and the third heat exchanger 301 is heated and used for the heat power conversion system 111 to generate power; the medium water of the methanation reactor 110 absorbs the heat released by the Sabatier reaction and is used for the heat power conversion system 111 to generate power;

[0163] S3, the flue gas generated by the combustor 103 is cooled by 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 electric energy generated by the heat power conversion power generation system 111 is used to heat the methane cracking reaction in step S1.

[0164] Embodiment 3

[0165] Figure 3 The general structure of the carbon sequestration power generation system of the carbon dioxide methanation and methane cracking coupling of the present embodiment is shown in the form of a structural diagram. The difference between the present embodiment and embodiment 1 is that 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. That is, the material flowing out of the first outlet 12 is first heat-exchanged and then enters the gas-solid separation device 116 for subsequent operations, instead of first entering the gas-solid separation device 116 to separate the gas and then heat-exchanged and subsequently operated as in embodiment 1. The rest is the same as in embodiment 1.

[0166] The carbon sequestration power generation method corresponding to the present embodiment adopts a molten medium catalyst to catalyze the methane cracking to produce hydrogen and solid carbon material; the hydrogen produced by the methane cracking is used for the Sabatier reaction to generate methane and water; the methane generated by the Sabatier reaction is used for the hydrogen production and solid carbon material; the heat released by the Sabatier reaction and / or the heat released after the endothermic methane cracking reaction is used for the heat power conversion power generation system to generate electricity. The molten medium catalyst is a molten metal, or a molten alloy, or a molten salt, or a molten metal / alloy and molten salt composite system. Specifically, the system described in the present embodiment comprises the following steps:

[0167] S1, the hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor 102 are heat-exchanged and cooled by the first heat exchanger 302, and then transmitted to the gas-solid separation device 116, while part of the molten medium catalyst and methane are brought in; the gas separated by the gas-solid separation device 116 is partly mixed with the carbon dioxide delivered by the carbon dioxide inlet pipe 109 and enters the methanation reactor 110 to undergo the Sabatier reaction, and the other part enters the combustor 103 to be combusted to provide heat for the methane cracking reaction; the carbon dioxide delivered by the carbon dioxide inlet pipe 109 is heat-exchanged and heated by the fifth heat exchanger 305;

[0168] S2, the methane and water obtained by Sabatier reaction are sequentially heat-exchanged and cooled by the second heat exchanger 303 and the fifth heat exchanger 305, and then enter the gas-liquid separator 113; the gas obtained by separation of the gas-liquid separator 113 enters the bubble column reactor 102 to participate in the methane cracking reaction by the fourth heat exchanger 304; the medium water of the first heat exchanger 302, the second heat exchanger 303 and the third heat exchanger 301 is heat-exchanged and heated to generate electricity in the heat power conversion power generation system 111; the medium water of the methanation reactor 110 absorbs the heat released by the Sabatier reaction to generate electricity in the heat power conversion power generation system 111;

[0169] S3, the flue gas generated by the burner 103 is heat-exchanged and cooled by the third heat exchanger 301 and the fourth heat exchanger 304, and the heat thereof is respectively used for heating the medium water of the third heat exchanger 301 in step S2 and preheating the methane cracking reaction gas in step S1; the electric energy generated by the heat power conversion power generation system 111 is used for heating in the methane cracking reaction in step S1.

[0170] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used for helping to understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed, and the changes and improvements of the present application will be possible, and will not exceed the concept and range defined by the claims; in summary, the content of the examples in the present specification should not be understood as the limitation of the present application.

Claims

1. A carbon capture and power generation system coupling carbon dioxide methanation and methane cracking, characterized in that, The system comprises a methane cracking unit, a methanation reaction unit and an energy recovery unit; The methane cracking unit comprises a bubble column reactor (102) and a gas-solid separation device (116); the bubble column reactor (102) is used for preparing hydrogen and solid carbon material by cracking methane, and is provided with a first inlet (11) and a first outlet (12) and is filled with a molten medium catalyst; the first outlet (12) is connected with a feeding port (31) of the gas-solid separation device; The methanation reaction unit comprises a methanation reactor (110), a gas-liquid separator (113) and a carbon dioxide feeding pipe (109); the methanation reactor (110) is used for catalytically preparing methane by using hydrogen and carbon dioxide as raw materials, and is provided with a second inlet (15) and a second outlet (16) and is filled with a methanation catalyst; the second inlet (15) is connected with the carbon dioxide feeding pipe (109); a gas outlet (18) of the gas-liquid separator is connected with the first inlet (11); The energy recovery unit comprises a heat exchanger and a heat power conversion power generation system (111); the heat exchanger comprises a first heat exchanger (302) and a second heat exchanger (303); the first outlet (12) is connected with the second inlet (15) through the first heat exchanger (302), and the first heat exchanger (302) is further connected with the heat power conversion power generation system (111) to exchange heat of the bubble column reactor (102) to the heat power conversion power generation system (111) for power generation; the second outlet (16) is connected with a feeding port (17) of the gas-liquid separator through the second heat exchanger (303), and the second heat exchanger (303) is further connected with the heat power conversion power generation system (111) to exchange heat of the second outlet (16) to the heat power conversion power generation system (111) for power generation.

2. The carbon capture and utilization system of claim 1, wherein, The methanation reactor (110) is connected with the heat power conversion power generation system (111) to heat steam formed by medium water flowing through the methanation reactor (110) by using heat released by the methanation reaction, and the steam is introduced into the heat power conversion power generation system (111) for power generation; the heat power conversion power generation system (111) comprises 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 capture and utilization system of claim 1, wherein, The first outlet (12) is connected with the second inlet (15) through the first heat exchanger (302) in particular that the first outlet (12) is connected with the feeding port (31) of the gas-solid separation device, and a gas outlet (32) of the gas-solid separation device is connected with the second inlet (15) through the first heat exchanger (302).

4. The carbon capture and utilization system of claim 1, wherein, The first outlet (12) is connected with the second inlet (15) through the first heat exchanger (302), specifically, the first outlet (12) is connected with a feeding port (31) of the gas-solid separation device through the first heat exchanger (302), and a gas outlet (32) of the gas-solid separation device is connected with the second inlet (15).

5. The carbon capture and utilization system of claim 1, wherein, The methane cracking unit further comprises a combustor (103) connected with the bubbling column reactor (102) for heating the bubbling column reactor (102); the heat exchanger further comprises a third heat exchanger (301); a flue gas outlet (107) of the combustor is connected with the third heat exchanger (301), and the third heat exchanger (301) is connected with the heat power conversion power generation system (111) so that the heat of the flue gas outlet (107) of the combustor is exchanged to the heat power conversion power generation system (111) for power generation.

6. The carbon capture and utilization system of claim 5, wherein the carbon dioxide methanation and methane cracking coupled carbon capture power generation system is characterized by, The heat exchanger further comprises a fourth heat exchanger (304); the gas outlet (18) of the gas-liquid separator is connected with the first inlet (11) through the fourth heat exchanger (304), and the flue gas outlet (107) of the combustor is connected with 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 for preheating the gas to be flowed into the first inlet (11).

7. The carbon dioxide methanation and methane cracking coupled carbon capture power generation system of claim 5, wherein, The heat exchanger further comprises a fourth heat exchanger (304); the gas outlet (18) of the gas-liquid separator is connected with the first inlet (11) through the fourth heat exchanger (304), and the first outlet (12) is connected with the second inlet (15) through the gas-solid separation device (116), the first heat exchanger (302) and the fourth heat exchanger (304) in sequence so that the waste heat of the bubbling column reactor (102) after heat exchange and cooling through the first heat exchanger (302) is used for preheating the gas to be flowed into the first inlet (11).

8. The carbon capture and storage power generation system that couples carbon dioxide methanation and methane cracking according to claim 6 or 7, wherein, The methane cracking unit further comprises a natural gas inlet pipe (101); the natural gas inlet pipe (101) is also connected with 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 capture and electricity generation system that couples carbon dioxide methanation and methane cracking according to claim 6 or 7, wherein, The methanation reaction unit further comprises a compressor (401); the gas outlet (18) of the gas-liquid separator is connected with the first inlet (11) through the compressor (401) and the fourth heat exchanger (304) in sequence, so that the gas flowed 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 bubbling column reactor (102).

10. The carbon capture and utilization system of claim 5, wherein, The fuel inlet (13) of the combustor is connected with the gas outlet (32) of the gas-solid separation device to deliver the gas flowing out of the gas outlet (32) of the gas-solid separation device into the combustor (103); and the combustor (103) is provided with an auxiliary agent inlet (14) for introducing oxygen and / or air.

11. The carbon capture and utilization system of claim 10, wherein the carbon dioxide methanation and methane cracking coupled carbon capture power generation system is characterized by, The fuel inlet (13) of the combustor is connected with the gas outlet (32) of the gas-solid separation device through the first heat exchanger (302) to deliver the gas cooled by heat exchange into the combustor (103).

12. The carbon capture and utilization system of claim 5, wherein, The methane cracking unit further comprises a solid carbon collector (104); the solid carbon collector (104) is connected with the solid carbon outlet (33) of the gas-solid separation device; the methanation reaction unit further comprises a condensate pump (114); the condensate pump (114) is connected with the liquid outlet (19) of the gas-liquid separator to pump the liquid flowing out of the liquid outlet (19) of the gas-liquid separator into downstream equipment.

13. The carbon capture and utilization system of claim 12, wherein the carbon dioxide methanation and methane cracking coupled carbon capture power generation system is characterized by, The downstream equipment comprises a water purification device; the liquid outlet (19) of the gas-liquid separator is connected with the heat power conversion power generation system (111) in sequence through the condensate pump (114), the water purification device and the first heat exchanger (302) to use the purified water as medium water of the first heat exchanger (302); The liquid outlet (19) of the gas-liquid separator is further connected with the heat power conversion power generation system (111) in sequence through the condensate pump (114), the water purification device and the second heat exchanger (303) to use the purified water as medium water of the second heat exchanger (303); The heat exchanger further comprises a third heat exchanger (301); the flue gas outlet (107) of the combustor is connected with the third heat exchanger (301), and the third heat exchanger (301) is further connected with the heat power conversion power generation system (111) to make the heat flowing out of the flue gas outlet (107) of the combustor exchange heat for the heat power conversion power generation system (111) to generate power; and the liquid outlet (19) of the gas-liquid separator is further connected with the heat power conversion power generation system (111) in sequence through the condensate pump (114), the water purification device and the third heat exchanger (301) to use the purified water as medium water of the third heat exchanger (301); The methanation reactor (110) is connected with the heat power conversion power generation system (111) to heat the water vapor formed by the medium water flowing through the methanation reactor (110) by using the heat released by the methanation reaction to introduce the water vapor into the heat power conversion power generation system (111) to generate power; and the liquid outlet (19) of the gas-liquid separator is further connected with the heat power conversion power generation system (111) in sequence through the condensate pump (114), the water purification device and the methanation reactor (110) to use the purified water as medium water of the methanation reactor (110).

14. The carbon capture and utilization system of claim 1, wherein, The heat exchanger further comprises a fifth heat exchanger (305); the second outlet (16) is connected with the feed inlet (17) of the gas-liquid separator in sequence through the second heat exchanger (303) and the fifth heat exchanger (305), the second inlet (15) is connected with the carbon dioxide inlet pipe (109), and the fifth heat exchanger (305) is arranged on the carbon dioxide inlet pipe (109), so that the product flowing out of the second outlet (16) is cooled by two-stage heat exchange and then enters the gas-liquid separator (113) for separation, and the heat of the product flowing out of the second outlet (16) is exchanged 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 capture and power generation system of any one of claims 1 to 7 or 10 to 14, wherein, The heat power conversion power generation system (111) is electrically connected with the bubbling column reactor (102), and the electric energy obtained by the heat power conversion power generation system (111) can be used for heating of the methane cracking.

16. A carbon capture and power generation method coupling carbon dioxide methanation and methane cracking, characterized in that, The system as claimed in claim 1 is adopted; a molten medium catalyst is used to catalyze methane cracking to produce hydrogen and solid carbon material; the hydrogen produced by the methane cracking is used for Sabatier reaction to generate methane and water; the methane generated by the Sabatier reaction is used for hydrogen production by cracking and solid carbon material; the heat released by the Sabatier reaction and / or the heat released after the heat absorption of the methane cracking reaction is used for power generation by a heat power conversion power generation system.

17. The carbon capture and storage power generation process that couples carbon dioxide methanation with methane cracking of claim 16, wherein, The electric energy obtained by the heat power conversion power generation system (111) is used for heating of the methane cracking or other occasions requiring electric energy; and the heat released by the Sabatier reaction is also used for preheating of the reactant carbon dioxide of the Sabatier reaction.

18. The carbon capture and storage power generation method of coupling carbon dioxide methanation with methane cracking of claim 16, wherein, The molten medium catalyst is a molten metal, or a molten alloy, or a molten salt, or a molten metal / alloy and molten salt composite system; and the catalyst for the Sabatier reaction is a Ni-based methanation catalyst.

19. The carbon capture and storage power generation method of coupling carbon dioxide methanation with methane cracking of claim 16, wherein, The methane cracking unit further comprises a burner (103); the burner (103) is connected with the bubbling column reactor (102) and is used for heating of the bubbling column reactor (102); The heat power conversion power generation system (111) is electrically connected with the bubbling column reactor (102), and the electric energy obtained by the heat power conversion power generation system (111) can be used for heating of the methane cracking. The heat exchanger further comprises a third heat exchanger (301), a fourth heat exchanger (304) and a fifth heat exchanger (305); the flue gas outlet (107) of the combustor is connected with the third heat exchanger (301), and the third heat exchanger (301) is connected with the heat power conversion power generation system (111) again, so that the heat of the flue gas outlet (107) of the combustor is exchanged to the heat power conversion power generation system (111) for power generation; the gas outlet (18) of the gas-liquid separator is connected with the first inlet (11) through the fourth heat exchanger (304), and the flue gas outlet (107) of the combustor is connected with 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 for preheating the gas to be flowed into the first inlet (11); the second outlet (16) is connected with the feed inlet (17) of the gas-liquid separator in turn through the second heat exchanger (303) and the fifth heat exchanger (305), the second inlet (15) is connected with the carbon dioxide inlet pipe (109), and the fifth heat exchanger (305) is arranged on the carbon dioxide inlet pipe (109), so that the product flowed out of the second outlet (16) enters the gas-liquid separator (113) after two-stage heat exchange and cooling for separation, and the heat of the second outlet (16) is exchanged 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 with the second inlet (15) through the first heat exchanger (302), specifically, the first outlet (12) is connected with the feed inlet (31) of the gas-solid separation device, and the gas outlet (32) of the gas-solid separation device is connected with the second inlet (15) through the first heat exchanger (302); The method comprises the following steps: S1, the hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor (102) are transported to the gas-solid separation device (116), while part of the molten medium catalyst and methane are brought in; the gas separated by the gas-solid separation device (116) is cooled and heat-exchanged by the first heat exchanger (302), part of which is introduced into the methanation reactor (110) together with the carbon dioxide transported by the carbon dioxide inlet pipe (109) to generate Sabatier reaction, and the other part is introduced into the combustor (103) to be combusted to provide heat for the methane cracking reaction; the carbon dioxide transported by the carbon dioxide inlet pipe (109) is heat-exchanged and heated by the fifth heat exchanger (305) for preheating; S2, the methane and water obtained from the Sabatier reaction are sequentially cooled by the second heat exchanger (303) and the fifth heat exchanger (305), and then enter the gas-liquid separator (113); the gas obtained from the gas-liquid separator (113) enters the bubble column reactor (102) to participate in the methane cracking reaction through the fourth heat exchanger (304); the medium water of the first heat exchanger (302), the second heat exchanger (303) and the third heat exchanger (301) is heated to generate power in the heat power conversion power generation system (111); the medium water of the methanation reactor (110) absorbs the heat released from the Sabatier reaction to generate power in the heat power conversion power generation system (111); S3, the flue gas generated by the combustor (103) is cooled by the third heat exchanger (301) and the fourth heat exchanger (304), and the heat is used for heating the medium water of the third heat exchanger (301) in step S2 and the preheating of the methane cracking reaction gas in step S1, respectively; the electric energy generated by the heat power conversion power generation system (111) can be used for heating the methane cracking reaction in step S1.

20. The carbon capture and storage power generation method of coupling carbon dioxide methanation with methane cracking of claim 16, wherein, The methane cracking unit further comprises a combustor (103); the combustor (103) is connected with the bubble column reactor (102) to provide heat for the bubble column reactor (102); The heat exchanger further comprises a third heat exchanger (301), a fourth heat exchanger (304) and a fifth heat exchanger (305); the flue gas outlet (107) of the combustor is connected with the third heat exchanger (301), and the third heat exchanger (301) is connected with the heat power conversion power generation system (111) again, so that the heat of the flue gas outlet (107) of the combustor is exchanged to the heat power conversion power generation system (111) for power generation; the gas outlet (18) of the gas-liquid separator is connected with the first inlet (11) through the fourth heat exchanger (304), and the flue gas outlet (107) of the combustor is connected with 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 for preheating the gas to be flowed into the first inlet (11); the second outlet (16) is connected with the feed inlet (17) of the gas-liquid separator in turn through the second heat exchanger (303) and the fifth heat exchanger (305), the second inlet (15) is connected with the carbon dioxide inlet pipe (109), and the fifth heat exchanger (305) is arranged on the carbon dioxide inlet pipe (109), so that the product flowed out of the second outlet (16) enters the gas-liquid separator (113) after two-stage heat exchange and cooling for separation, and the heat of the second outlet (16) is exchanged 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 with the second inlet (15) through the first heat exchanger (302), specifically, the first outlet (12) is connected with 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 with the second inlet (15); The method comprises 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 through the first heat exchanger (302), and then transmitted to the gas-solid separation device (116) while part of the molten medium catalyst and methane are brought in; the gas separated by the gas-solid separation device (116) is partly mixed with the carbon dioxide delivered by the carbon dioxide inlet pipe (109) and then enters the methanation reactor (110) to generate Sabatier reaction, and the other part enters the combustor (103) to be combusted to provide heat for the methane cracking reaction; the carbon dioxide delivered by the carbon dioxide inlet pipe (109) is preheated by heat exchange through the fifth heat exchanger (305); S2, the methane and water obtained by Sabatier reaction are sequentially heat-exchanged and cooled by the second heat exchanger (303) and the fifth heat exchanger (305) and then enter the gas-liquid separator (113); the gas separated by the gas-liquid separator (113) enters the bubbling column reactor (102) to participate in the methane cracking reaction through the fourth heat exchanger (304); the medium water of the first heat exchanger (302), the second heat exchanger (303) and the third heat exchanger (301) is heat-exchanged and heated to generate power in the heat power conversion power generation system (111); the medium water of the methanation reactor (110) absorbs the heat released by Sabatier reaction to generate power in the heat power conversion power generation system (111); S3, the flue gas generated by the combustor (103) is heat-exchanged and cooled by the third heat exchanger (301) and the fourth heat exchanger (304), and the heat is used for heating the medium water of the third heat exchanger (301) in step S2 and preheating the methane cracking reaction gas in step S1, respectively; the electric energy generated by the heat power conversion power generation system (111) is used for heating in the methane cracking reaction in step S1.

21. The carbon capture and storage power generation method of coupling carbon dioxide methanation and methane cracking of claim 16, wherein, The methane cracking unit further comprises a combustor (103); the combustor (103) is connected with the bubbling column reactor (102) and used for heating the bubbling column reactor (102); The heat exchanger further comprises a third heat exchanger (301), a fourth heat exchanger (304) and a fifth heat exchanger (305); the flue gas outlet (107) of the combustor is connected with the third heat exchanger (301), and the third heat exchanger (301) is connected with the heat power conversion power generation system (111) to make the heat of the flue gas outlet (107) of the combustor heat-exchanged to the heat power conversion power generation system (111) for power generation; the gas outlet (18) of the gas-liquid separator is connected with the first inlet (11) through the fourth heat exchanger (304), the first outlet (12) is connected with the second inlet (15) through the gas-solid separation device (116), the first heat exchanger (302) and the fourth heat exchanger (304) in sequence to make the waste heat of the bubbling column reactor (102) heat-exchanged and cooled by the first heat exchanger (302) used for preheating the gas to be flowed into the first inlet (11); the second outlet (16) is connected with the feed inlet (17) of the gas-liquid separator through the second heat exchanger (303) and the fifth heat exchanger (305) in sequence, the second inlet (15) is connected with the carbon dioxide inlet pipe (109), and the fifth heat exchanger (305) is arranged on the carbon dioxide inlet pipe (109) to make the product flowed out of the second outlet (16) heat-exchanged and cooled by two stages and then enter the gas-liquid separator (113) for separation, and the heat of the second outlet (16) is heat-exchanged 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 comprises the following steps: S1, transmitting the hydrogen and solid carbon material produced by the methane cracking reaction in the bubble column reactor (102) to the gas-solid separation device (116), while bringing part of the molten medium catalyst and methane; the gas separated by the gas-solid separation device (116) is cooled by 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 generate Sabatier reaction, and another part is cooled by the first heat exchanger (302) and then enters the combustor (103) to generate combustion heat for the methane cracking reaction; the carbon dioxide transported by the carbon dioxide inlet pipe (109) is preheated by the fifth heat exchanger (305); S2, the methane and water generated by Sabatier reaction are cooled by the second heat exchanger (303) and the fifth heat exchanger (305) in sequence and then enter the gas-liquid separator (113); the gas separated by the gas-liquid separator (113) enters the bubble column reactor (102) to participate in the methane cracking reaction by the fourth heat exchanger (304); the medium water of the first heat exchanger (302), the second heat exchanger (303) and the third heat exchanger (301) is heated and used for power generation of the heat power conversion system (111); the medium water of the methanation reactor (110) absorbs the heat released by Sabatier reaction and is used for power generation of the heat power conversion system (111); S3, the flue gas generated by the combustor (103) is cooled by the third heat exchanger (301), and the heat is used for heating the medium water of the third heat exchanger (301) in step S2; the electric energy generated by the heat power conversion system (111) is used for heating the methane cracking reaction in step S1.

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