Zero carbon emission offshore liquefied natural gas production system device and method

Abstract

Disclosed in the present invention is a zero carbon emission offshore liquefied natural gas production system device. The zero carbon emission offshore liquefied natural gas production system device comprises an offshore liquefied natural gas separation device, a water-electrolytic hydrogen production device, and a CO2 methanation device, wherein the offshore liquefied natural gas separation device comprises an offshore liquefied natural gas storage tank, a first raw material delivery pump, a first condenser, a first cryogenic rectification apparatus, a second raw material delivery pump, a second condenser, a second cryogenic rectification apparatus, a natural gas condensation and drying apparatus, and a natural gas pressurization and liquefaction apparatus; the water-electrolytic hydrogen production device comprises a water storage tank, a water delivery pump, a clean energy power generation apparatus, a water-electrolytic hydrogen production apparatus, and a hydrogen delivery apparatus; and the CO2 methanation device comprises a gas mixer, a heat exchanger, a multistage heat-transfer high-gravity reactor, and a third condenser. Using the multistage heat-transfer high-gravity reactor, the present invention can, on the one hand, solve the problem of heat transfer of the high-gravity device during the highly exothermic reaction, and on the other hand, can effectively reduce carbon deposition on the surface of the catalyst.

Description

A zero-carbon emission marine liquefied natural gas production system and method Technical Field

[0001] The present invention relates to the technical field of marine natural gas production technology and application, and more specifically, to a zero-carbon emission marine liquefied natural gas production system and method. Background Art

[0002] Over 10% of the world's natural gas resources are carbon-rich, primarily located in the South China Sea, the northwest Australian shelf, Central America, and southeastern Brazil. The South China Sea region boasts exceptionally rich natural gas resources, accounting for approximately 12% of the world's total oil and gas resources and one-third of China's total. Its CO2 content generally ranges from 15% to 80%, and 75% of the resources are located in deepwater areas, making development costly and challenging. The development of carbon-rich natural gas presents challenges not only from a technical perspective but also from environmental pressures. Directly releasing such large amounts of CO2 into the atmosphere could exacerbate global greenhouse effects and climate change, bringing disaster to humanity.

[0003] The zero-carbon marine LNG production process involves separating CO2 from natural gas extracted from offshore platforms and then producing LNG through a methanation reaction. This not only allows the resource utilization of CO2 in carbon-rich natural gas, reducing CO2 emissions, but also leverages the already well-established marine LNG infrastructure, integrating it with the existing marine LNG storage, transportation, distribution, and consumption network. Therefore, this process is of great significance in addressing the resource utilization of CO2 from marine natural gas.

[0004] Traditional natural gas decarbonization processes often use a dual-tower solvent absorption and desorption method to separate CO2 from natural gas. When applied to natural gas decarbonization on offshore platforms, this method requires the introduction of solvents such as ethanolamine to the offshore platform, which presents a series of challenges, including solvent transportation and handling. Furthermore, the large scale and complexity of dual-tower operations make them inadequate for the limited space available on offshore platforms. For example, Chinese patent application CN 105444527A discloses a natural gas processing device and method comprising a decarbonization system and a liquefaction system, the decarbonization system being connected to the liquefaction system, and a refrigeration system, each of which is connected to the refrigeration system. The decarbonization system comprises a first heat exchanger and a packed distillation column; the feed gas outlet of the first heat exchanger is connected to the feed gas inlet of the packed distillation column. By adopting a saddle-ring packed distillation column for decarbonization instead of traditional dual-tower decarbonization processes such as absorption and adsorption, and using the refrigeration system to provide cooling for the decarbonization process, the scale of the natural gas decarbonization device is reduced, the decarbonization process is simplified, and the power consumption of the processing device is reduced. Considering the space limitations of offshore platforms, it is necessary to use more compact distillation and separation equipment.

[0005] Furthermore, the CO2 methanation process utilizes a fixed-bed reactor, which increases the temperature and is difficult to control. This leads to carbon deposition and reduces catalyst activity, hindering efficient CO2 conversion. Therefore, developing an efficient, zero-carbon marine liquefied natural gas production process is of great practical significance and industrial application value. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a zero-carbon emission marine liquefied natural gas production system device.

[0007] The second technical problem to be solved by the present invention is to provide a method for producing marine liquefied natural gas with zero carbon emissions using the above-mentioned system device.

[0008] In order to solve the above-mentioned first technical problem, the technical solution adopted by the invention is as follows:

[0009] A zero-carbon emission marine liquefied natural gas production system device, including a marine natural gas separation device, a water electrolysis hydrogen production device and a CO2 methanation device;

[0010] The marine natural gas separation device includes a marine natural gas storage tank, a first raw material delivery pump, a first condenser, a first cryogenic distillation device, a second raw material delivery pump, a second condenser, a second cryogenic distillation device, a natural gas condensation and drying device, and a natural gas pressurized liquefaction device;

[0011] The marine natural gas storage tank, the first raw material delivery pump, the first condenser, and the first cryogenic distillation equipment are connected in sequence through pipelines;

[0012] The top of the first cryogenic distillation equipment is connected to the inlet of the second raw material delivery pump through a pipeline;

[0013] The outlet of the second raw material delivery pump is connected to the inlet of the second condenser through a pipeline, and the outlet of the second condenser is connected to the inlet of the second cryogenic distillation equipment through a pipeline; the outlet of the second cryogenic distillation equipment passes through the natural gas condensation and drying equipment and the natural gas pressure liquefaction equipment, and is then transported to external users through the natural gas transmission pipeline network;

[0014] The bottom outlet of the first cryogenic rectification equipment is connected to a gas mixer via a pipeline;

[0015] The water electrolysis hydrogen production device includes a water storage tank, a water delivery pump, clean energy power generation equipment, water electrolysis hydrogen production equipment and hydrogen delivery equipment;

[0016] The water storage tank is connected to the water electrolysis hydrogen production equipment through a pipeline and a water delivery pump;

[0017] The clean energy power generation equipment is electrically connected to the water electrolysis hydrogen production equipment to provide it with electrical energy;

[0018] The water electrolysis hydrogen production equipment is connected to the gas mixer via the hydrogen delivery equipment;

[0019] The CO2 methanation device includes a gas mixer, a heat exchanger, a multi-stage heat transfer type high gravity reactor and a third condenser;

[0020] The gas mixer, heat exchanger, multi-stage heat transfer high-gravity reactor and third condenser are connected in sequence; the outlet of the third condenser is divided into two branches; the gas phase of the first branch is led to the natural gas condensation and drying equipment and the natural gas pressurized liquefaction equipment, and then transported to external users through the natural gas transmission pipeline network; the liquid phase of the second branch is led through a pipeline to the pipeline connecting the water storage tank and the water delivery pump.

[0021] Preferably, the multi-stage heat transfer type high gravity reactor includes a motor, a shell, a rotor, a heat exchange component, a heat exchange medium inlet, a reaction material inlet, a dynamic seal, a heat exchange medium outlet, and a generated material outlet.

[0022] Preferably, the first cryogenic distillation equipment and the second cryogenic distillation equipment are rotary distillation separation equipment that can enhance gas-liquid mass transfer; the first cryogenic distillation equipment is used to separate carbon dioxide from the raw marine natural gas; the second cryogenic distillation equipment is used to separate nitrogen from the raw marine natural gas.

[0023] Preferably, the operating temperature of the first cryogenic distillation equipment is -100 to 50°C and the operating pressure is 0.1 to 10 MPa; the operating temperature of the second cryogenic distillation equipment is -180 to -50°C and the operating pressure is 0.1 to 10 MPa.

[0024] Preferably, the rotor of the multi-stage heat transfer high-gravity reactor is loaded with a catalyst for catalyzing CO2 methanation, and the catalyst is loaded in a regular loading type or in bulk.

[0025] Preferably, the reaction temperature in the rotor of the multi-stage heat transfer high gravity reactor is 150-500°C, and the reaction pressure is 0.1-10 MPa. More preferably, the reaction temperature in the rotor is 250-400°C, and the reaction pressure is 0.1-2 MPa.

[0026] Preferably, the rotor speed in the multi-stage heat transfer high gravity reactor is 100 to 3000 r / min, more preferably, the speed range is 500 to 1500 r / min.

[0027] Preferably, the clean energy power generation equipment is one or more of solar photovoltaic power generation equipment, wind power generation equipment, and other surplus energy power generation equipment on offshore natural gas platforms.

[0028] Preferably, the source of the raw water for the water electrolysis hydrogen production device is one or a combination of seawater, desalinated seawater, and water separated by the third condenser.

[0029] Preferably, the water electrolysis hydrogen production equipment is one of an alkaline electrolyzer, a proton exchange membrane electrolyzer, a high-temperature solid oxide water electrolyzer or a solid polymer anion exchange membrane electrolyzer.

[0030] In order to solve the above second technical problem, the present invention adopts the following technical solution:

[0031] A method for producing marine liquefied natural gas with zero carbon emissions using the above system device comprises the following steps:

[0032] S1. After pretreatment, the natural gas raw material mainly containing CH4, CO2, and N2 is transported by pipeline to the marine natural gas storage tank, and then partially condensed by the first raw material delivery pump and the first condenser and transported to the first cryogenic distillation equipment. The first cryogenic distillation equipment separates CH4 and N2 at the top of the tower, and separates high-purity CO2 at the bottom of the tower;

[0033] S2: CH4 and N2 extracted from the top of the first cryogenic distillation equipment are condensed by the second raw material delivery pump and the second condenser, and then transported to the second cryogenic distillation equipment. The N2 extracted from the top of the second cryogenic distillation equipment is discharged, and high-purity CH4 is separated at the bottom of the tower. It is further condensed and dried in the natural gas condensation and drying equipment, pressurized and liquefied in the natural gas pressure liquefaction equipment, and then transported to the external natural gas transportation network;

[0034] S3, using a water electrolysis hydrogen production device powered by clean energy power generation equipment to produce high-purity hydrogen;

[0035] S4. The high-purity CO2 separated at the bottom of the first cryogenic distillation equipment and the H2 produced by the water electrolysis hydrogen production equipment are mixed in proportion in a gas mixer, and then preheated in a heat exchanger before entering a multi-stage heat transfer high-gravity reactor; in the multi-stage heat transfer high-gravity reactor, they alternately pass through the rotor reaction area and the stator heat exchange area to undergo CO2 methanation reaction and heat exchange, respectively. Finally, the product is condensed in the third condenser to obtain natural gas that meets the requirements, and is further condensed and dried in a natural gas condensation and drying equipment, pressurized and liquefied in a natural gas pressurized liquefaction equipment, and then transported to the external natural gas transportation pipeline network.

[0036] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0037] Unless otherwise specified, all raw materials in the present invention can be purchased commercially, and the equipment used in the present invention can adopt conventional equipment in the relevant field or refer to the existing technology in the relevant field.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The present invention provides a zero-carbon emission marine liquefied natural gas production system and production method. On the one hand, this method uses green hydrogen obtained by electrolyzing water with renewable energy and CO2 separated from marine natural gas to carry out methanation reaction, thereby realizing the resource utilization of CO2 in marine natural gas, which is in line with the development trend of energy conservation and emission reduction. On the other hand, it can make use of the existing liquefied natural gas transportation pipeline, reducing the investment in transportation and other equipment.

[0040] 2. Compared with the traditional natural gas decarbonization process on offshore platforms, the present invention provides a low-temperature distillation natural gas decarbonization method, which avoids the transportation and treatment of solvents, reduces the number and scale of equipment, and better meets the actual needs of limited space on offshore platforms. In addition, it is more surprising to find that the use of more compact rotary distillation separation equipment will further reduce the equipment volume, which is conducive to reducing the equipment space for the resource utilization process of CO2.

[0041] 3. Since CO2 methanation uses a multi-stage heat transfer high-gravity reactor, it can achieve rapid heat transfer and effectively control the contact time between the reactants and products and the catalyst, without causing excessive heat accumulation, and is easy to operate. The process of the present invention unexpectedly discovered that the introduction of a multi-stage heat transfer high-gravity reactor for the CO2 methanation reaction can reduce carbon deposition on the catalyst surface, improve the activity of the catalyst, and at the same time reduce investment in equipment and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] FIG1 shows a schematic diagram of a zero-carbon emission marine liquefied natural gas production system according to the present invention;

[0044] FIG2 is a schematic diagram of a multi-stage heat transfer high-gravity reactor in a zero-carbon emission marine liquefied natural gas production system according to the present invention;

[0045] FIG3 shows a schematic diagram of a production system device in Comparative Example 5 in which three single-stage high-gravity reactors and two heat exchangers are used instead of the multi-stage heat transfer high-gravity reactor. DETAILED DESCRIPTION

[0046] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0047] 1 , as one aspect of the present invention, a zero-carbon emission marine liquefied natural gas production system device includes a marine natural gas separation device 100, a water electrolysis hydrogen production device 200, and a CO2 methanation device 300;

[0048] The marine natural gas separation device 100 includes a marine natural gas storage tank 101, a first raw material delivery pump 102, a first condenser 103, a first cryogenic distillation device 104, a second raw material delivery pump 105, a second condenser 106, a second cryogenic distillation device 107, a natural gas condensation and drying device 108, and a natural gas pressurized liquefaction device 109;

[0049] The first cryogenic distillation equipment 104 is used to separate carbon dioxide from the raw marine natural gas; the second cryogenic distillation equipment 107 is used to separate nitrogen from the raw marine natural gas;

[0050] The marine natural gas storage tank 101, the first raw material delivery pump 102, the first condenser 103, and the first cryogenic distillation equipment 104 are connected in sequence through pipelines;

[0051] The top of the first cryogenic distillation equipment 104 is connected to the inlet of the second raw material delivery pump 105 through a pipeline;

[0052] The outlet of the second raw material delivery pump 105 is connected to the inlet of the second condenser 106 through a pipeline, and the outlet of the second condenser 106 is connected to the inlet of the second cryogenic distillation equipment 107 through a pipeline; the outlet of the second cryogenic distillation equipment 107 passes through the natural gas condensation and drying equipment 108 and the natural gas pressure liquefaction equipment 109, and is then transported to external users through the natural gas transmission pipeline network;

[0053] The bottom outlet of the first cryogenic rectification equipment 104 is connected to the gas mixer 301 through a pipeline;

[0054] The electrolytic water hydrogen production device 200 includes a water storage tank 201, a water delivery pump 202, a clean energy power generation device 203, an electrolytic water hydrogen production device 204 and a hydrogen delivery device 205;

[0055] The water storage tank 201 is connected to the water electrolysis hydrogen production equipment 204 through a pipeline and a water delivery pump 202;

[0056] The clean energy power generation equipment 203 is electrically connected to the water electrolysis hydrogen production equipment 204 to provide it with electrical energy;

[0057] The water electrolysis hydrogen production equipment 204 is connected to the gas mixer 301 through the hydrogen delivery equipment 205;

[0058] The CO2 methanation device 300 includes a gas mixer 301, a heat exchanger 302, a multi-stage heat transfer high gravity reactor 303 and a third condenser 304;

[0059] The gas mixer 301, the heat exchanger 302, the multi-stage heat transfer supergravity reactor 303 and the third condenser 304 are connected in sequence; the outlet of the third condenser 304 is divided into two branches; the gas phase of the first branch is led to the natural gas condensation and drying equipment 108 and the natural gas pressurized liquefaction equipment 109 and then transported to external users through the natural gas transmission pipeline network; the liquid phase of the second branch is led to the pipeline connecting the water storage tank 201 and the water delivery pump 202 through a pipeline.

[0060] 2 , the multi-stage heat transfer high-gravity reactor 303 includes a motor 3031, a housing 3032, a rotor 3033, a heat exchange component 3034, a heat exchange medium inlet 3035, a reaction material inlet 3036, a dynamic seal 3037, a heat exchange medium outlet 3038, and a product material outlet 3039. In the multi-stage heat transfer high-gravity reactor 303, the rotor 3033 and the catalyst therein are rotating components, and the heat exchange component 3034 is fixed to the housing.

[0061] In the present invention, a multi-stage heat transfer supergravity reactor 303 is used as a reactor for CO2 methanation. Its purpose is not to simply enhance mass transfer and thereby improve reaction efficiency. Rather, it is because the use of a fixed-bed reactor is prone to carbon deposition, which leads to catalyst deactivation and reduced catalyst activity, which is not conducive to the efficient conversion of CO2. The supergravity reactor effectively regulates the contact time between the reactants and products and the catalyst, which does not cause localized excessive accumulation of heat and is easy to operate. The supergravity reactor of the present invention is used for CO2 methanation reaction, which can reduce carbon deposition on the catalyst surface and improve catalyst activity. In addition, by adding a heat exchange area in the middle of the multi-stage rotor, the problem of difficulty in heat transfer in the supergravity device used for CO2 methanation, a highly exothermic reaction process, is effectively solved.

[0062] In certain embodiments, the first cryogenic distillation apparatus 104 and the second cryogenic distillation apparatus 107 are selected from rotary distillation separation apparatus capable of enhancing gas-liquid mass transfer; the first cryogenic distillation apparatus 104 is used to separate carbon dioxide from the raw marine natural gas; and the second cryogenic distillation apparatus 107 is used to separate nitrogen from the raw marine natural gas. The present invention unexpectedly discovered that using cryogenic distillation apparatus to separate carbon dioxide from the raw marine natural gas, compared to the prior art adsorption decarbonization process, not only avoids the transportation and handling of solvents, reduces the number and scale of equipment, and better meets the practical needs of limited space on offshore platforms, but also significantly improves production efficiency by at least 20%.

[0063] In certain embodiments, the operating temperature of the first cryogenic distillation unit 104 is -100°C to 50°C and the operating pressure is 0.1 to 10 MPa; the operating temperature of the second cryogenic distillation unit 107 is -180°C to -50°C and the operating pressure is 0.1 to 10 MPa. Temperatures and pressures below or above these ranges may reduce the corresponding separation and recovery efficiency and increase separation energy consumption.

[0064] In certain embodiments, the rotor of the multi-stage heat transfer high-gravity reactor 303 is loaded with a catalyst for catalyzing CO 2 methanation, and the catalyst is loaded in a regular loading type or in bulk.

[0065] In certain embodiments, the reaction temperature within the rotor of the multi-stage heat transfer high-gravity reactor 303 is 150-500°C and the reaction pressure is 0.1-10 MPa. More preferably, the reaction temperature within the rotor is 250-400°C and the reaction pressure is 0.1-2 MPa. During the reaction process, if the reaction temperature is higher than 500°C, the catalyst may be deactivated due to sintering, and the selectivity of CH4 will be thermodynamically limited. However, if the reaction temperature is too low, the reaction rate will slow down. Increasing the pressure is beneficial to increasing the reaction rate and equilibrium conversion rate, but excessive pressure will lead to increased equipment investment and energy consumption.

[0066] In some embodiments, the internal rotor speed of the multi-stage heat transfer high gravity reactor 303 is 100-3000 r / min, more preferably, the speed range is 500-1500 r / min.

[0067] In some embodiments, the clean energy power generation equipment 203 is one or more of solar photovoltaic power generation equipment, wind power generation equipment, and other residual energy power generation equipment on an offshore natural gas platform.

[0068] In some embodiments, the source of the raw water for the water electrolysis hydrogen production device 200 is seawater, desalinated seawater, or water separated by the third condenser, or a combination thereof.

[0069] In some embodiments, the water electrolysis hydrogen production equipment 204 is one of an alkaline electrolyzer, a proton exchange membrane electrolyzer, a high-temperature solid oxide water electrolyzer, or a solid polymer anion exchange membrane electrolyzer.

[0070] As a second aspect of the present invention, a method for producing marine liquefied natural gas with zero carbon emissions using the above-mentioned system device comprises the following steps:

[0071] S1. After pretreatment, the natural gas raw material mainly containing CH4, CO2, and N2 is transported by pipeline to the marine natural gas storage tank 101, and then partially condensed by the first raw material delivery pump 102 and the first condenser 103 and transported to the first cryogenic distillation equipment 104. The first cryogenic distillation equipment 104 separates CH4 and N2 at the top of the tower, and separates high-purity CO2 at the bottom of the tower;

[0072] S2, CH4 and N2 extracted from the top of the first cryogenic distillation equipment 104 are condensed by the second raw material delivery pump 105 and the second condenser 106, and then transported to the second cryogenic distillation equipment 107. The N2 extracted from the top of the second cryogenic distillation equipment 107 is discharged, and high-purity CH4 is separated at the bottom of the tower. It is further condensed and dried by the natural gas condensation and drying equipment 108 and pressurized and liquefied by the natural gas pressure liquefaction equipment 109 before being transported to the external natural gas transportation network;

[0073] S3, the water electrolysis hydrogen production equipment 204, which is powered by the clean energy power generation equipment 203, produces high-purity hydrogen;

[0074] S4. High-purity CO2 separated at the bottom of the first cryogenic distillation equipment 104 and H2 produced by the water electrolysis hydrogen production equipment 204 are mixed in proportion in the gas mixer 301, and then preheated in the heat exchanger 302 before entering the multi-stage heat transfer high-gravity reactor 303. In the multi-stage heat transfer high-gravity reactor 303, the CO2 alternately passes through the rotor reaction area and the stator heat exchange area, where CO2 methanation reaction and heat exchange occur respectively. Finally, the product is condensed and dried in the third condenser 306 to obtain natural gas that meets the requirements. The natural gas is further condensed and dried in the natural gas condensation and drying equipment 108 and pressurized and liquefied in the natural gas pressure liquefaction equipment 109 before being transported to the external natural gas transportation pipeline network.

[0075] Example 1

[0076] A method for producing marine liquefied natural gas with zero carbon emissions using the above-mentioned system device as shown in FIG1 includes the following steps:

[0077] S1. After pretreatment, the natural gas raw material, which mainly contains about 40% CH4, 55% CO2, and 5% N2 by volume, is transported by pipeline to an offshore natural gas storage tank, and then partially condensed by a first raw material delivery pump and a first condenser before being transported to a first cryogenic distillation device. The first cryogenic distillation device separates 88% CH4 and 12% N2 at the top of the tower, and separates high-purity 85% CO2 at the bottom of the tower;

[0078] S2, CH4 and N2 extracted from the top of the first cryogenic distillation equipment are condensed by the second raw material delivery pump and the second condenser, and then transported to the second cryogenic distillation equipment. 97% N2 is extracted from the top of the second cryogenic distillation equipment and discharged to the air. High-purity 97% CH4 is separated from the bottom of the tower, further condensed and dried in the natural gas condensation and drying equipment, pressurized and liquefied in the natural gas pressure liquefaction equipment, and then transported to the external natural gas transportation pipeline network;

[0079] S3, a water electrolysis hydrogen production device powered by solar power generation equipment produces high-purity 99% hydrogen;

[0080] S4. NiMn / Al2O3 catalysts are respectively loaded and formed in the rotor of the multi-stage heat transfer high-gravity reactor. CO2 and H2 produced by the water electrolysis hydrogen production equipment are separated at the bottom of the first low-temperature distillation equipment, mixed in a gas mixer at a volume ratio of 1:4, and then preheated in a heat exchanger. The mixture enters the multi-stage heat transfer high-gravity reactor and undergoes a CO2 methanation reaction under 2MPa and 300°C. Finally, the product is condensed and dried in the third condenser to obtain natural gas that meets the requirements. The product is further condensed and dried in the natural gas condensation and drying equipment, pressurized and liquefied in the natural gas pressurized liquefaction equipment, and then transported to the external natural gas transportation pipeline network.

[0081] Comparative Example 1

[0082] Example 1 was repeated, with the only difference being that a monoethanolamine double-tower absorption and desorption decarbonization process was used instead of the first cryogenic distillation equipment to remove CO2.

[0083] The results show that the investment cost of decarbonization equipment will increase by 26%, the annual operating investment cost will increase by 22%; and the decarbonization efficiency will decrease by 23%.

[0084] Comparative Example 2

[0085] Example 1 was repeated, with the only difference being that three fixed-bed reactors were used instead of the multi-stage heat transfer high-gravity reactor for the CO2 methanation reaction.

[0086] The results showed that the CO2 conversion rate decreased by 16% and the CH4 selectivity decreased by 7%.

[0087] Comparative Example 3

[0088] Example 1 was repeated except that three fixed-bed reactors were used instead of the multi-stage heat transfer high-gravity reactor for the CO2 methanation reaction. It was found that, while achieving the same methane yield, the operating time of the system apparatus using the multi-stage heat transfer high-gravity reactor was 28% shorter than that of the system apparatus using the fixed-bed reactor. Further XRD analysis of the catalyst discharged from the reactor revealed that the specific surface area of ​​the catalyst in the fixed-bed reactor was approximately 24% smaller than that in the high-gravity reactor.

[0089] It can be seen that when achieving the same conversion rate, the system device using three fixed-bed reactors will cause the catalyst activity to decrease due to carbon deposition, resulting in a shorter service life and a lower conversion rate.

[0090] Comparative Example 4

[0091] Example 1 was repeated except that a fixed-bed reactor with multi-stage heat transfer was used instead of a multi-stage heat transfer high-gravity reactor for the CO2 methanation reaction. It was found that, while achieving the same methane production, the operating time of the system apparatus using the high-gravity reactor was 22% shorter than that of the system apparatus using the fixed-bed reactor. In addition, it was found that the investment cost of the methanation reaction equipment would increase by 29%, and the annual operating investment cost would increase by 12%.

[0092] This is mainly because the use of a fixed-bed reactor with multiple heat transfer stages will also cause carbon deposition, which will reduce the catalyst activity, shorten its service life, and reduce the conversion rate.

[0093] Comparative Example 5

[0094] 3 , Example 1 was repeated, with the only difference being that three single-stage high-gravity reactors and two heat exchangers were used instead of the multi-stage heat transfer high-gravity reactor for the CO 2 methanation reaction.

[0095] The results show that while maintaining the same CO2 conversion rate, the equipment investment cost will increase by 13% and the annual operating investment cost will increase by 8%.

[0096] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications based on the above description are possible. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A zero-carbon emission marine liquefied natural gas production system, characterized by: Including marine natural gas separation device, water electrolysis hydrogen production device and CO2 methanation device; The marine natural gas separation device includes a marine natural gas storage tank, a first raw material delivery pump, a first condenser, a first cryogenic distillation device, a second raw material delivery pump, a second condenser, a second cryogenic distillation device, a natural gas condensation and drying device, and a natural gas pressurized liquefaction device; The marine natural gas storage tank, the first raw material delivery pump, the first condenser, and the first cryogenic distillation equipment are connected in sequence through pipelines; The top of the first cryogenic distillation equipment is connected to the inlet of the second raw material delivery pump through a pipeline; The outlet of the second raw material delivery pump is connected to the inlet of the second condenser through a pipeline, and the outlet of the second condenser is connected to the inlet of the second cryogenic distillation equipment through a pipeline; the outlet of the second cryogenic distillation equipment passes through the natural gas condensation and drying equipment and the natural gas pressure liquefaction equipment and then is transported to external users through the natural gas transmission pipeline network; The bottom outlet of the first cryogenic rectification equipment is connected to a gas mixer via a pipeline; The water electrolysis hydrogen production device comprises a water storage tank, a water delivery pump, clean energy power generation equipment, water electrolysis hydrogen production equipment and hydrogen delivery equipment; The water storage tank is connected to the water electrolysis hydrogen production equipment through a pipeline and a water delivery pump; The clean energy power generation equipment is electrically connected to the water electrolysis hydrogen production equipment to provide electrical energy therefor; The water electrolysis hydrogen production equipment is connected to the gas mixer via the hydrogen delivery equipment; The CO2 methanation device comprises a gas mixer, a heat exchanger, a multi-stage heat transfer type ultra-gravity reactor and a third condenser; The gas mixer, heat exchanger, multi-stage heat transfer ultra-gravity reactor and the third condenser are connected in sequence; the outlet of the third condenser is divided into two branches; the gas phase of the first branch leads to the natural gas condensation and drying equipment and the natural gas pressurized liquefaction equipment and then is transported to external users through the natural gas transmission pipeline network; the liquid phase of the second branch leads to the pipeline connecting the water storage tank and the water delivery pump through the pipeline.

2. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The multi-stage heat transfer ultragravity reactor includes a motor, a shell, a rotor, a heat exchange component, a heat exchange medium inlet, a reaction material inlet, a dynamic seal, a heat exchange medium outlet, and a generated material outlet; preferably, the first low-temperature distillation equipment and the second low-temperature distillation equipment are selected from rotary distillation separation equipment that can enhance gas-liquid mass transfer.

3. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The operating temperature of the first cryogenic distillation equipment is -100 to 50° C., and the operating pressure is 0.1 to 10 MPa; the operating temperature of the second cryogenic distillation equipment 107 is -180 to -50° C., and the operating pressure is 0.1 to 10 MPa.

4. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The multi-stage heat transfer ultra-gravity reactor has a rotating reaction module and a fixed heat transfer module from bottom to top, and the number of layers of the reaction module and the heat exchange module is 1-10 layers. Preferably, the number of layers of the reaction module and the heat exchange module is 2-6 layers; the rotor is loaded with a catalyst for catalyzing CO2 methanation, and the catalyst is loaded in a regular loading type or a bulk type.

5. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The temperature in the reaction rotor region of the multi-stage heat transfer type ultra-gravity reactor is 150-500° C., and the reaction pressure is 0.1-10 MPa. Preferably, the temperature in the rotor region is 250-400° C., and the reaction pressure is 0.1-2 MPa.

6. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The internal rotor speed of the multi-stage heat transfer ultra-gravity reactor is 100-3000 r / min, preferably, the speed range is 500-1500 r / min.

7. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The clean energy power generation equipment is one or more of solar photovoltaic power generation equipment, wind power generation equipment, and other surplus energy power generation equipment on an offshore natural gas platform.

8. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The source of the raw water of the water electrolysis hydrogen production device is one or a combination of seawater, desalinated seawater, and water separated by the third condenser.

9. The zero-carbon emission marine liquefied natural gas production system according to claim 1, characterized in that: The water electrolysis hydrogen production equipment is one of an alkaline electrolyzer, a proton exchange membrane electrolyzer, a high-temperature solid oxide water electrolyzer or a solid polymer anion exchange membrane electrolyzer.

10. A method for producing marine liquefied natural gas using the system device described in any one of claims 1 to 9, characterized in that: The following steps are involved: S1, the natural gas raw material mainly containing CH4, CO2, and N2 after pretreatment is transported to the marine natural gas storage tank by pipeline, and then partially condensed by the first raw material delivery pump and the first condenser and transported to the first cryogenic distillation equipment, and CH4 and N2 are separated at the top of the first cryogenic distillation equipment, and high-purity CO2 is separated at the bottom of the tower; S2, CH4 and N2 extracted from the top of the first cryogenic distillation equipment are condensed by the second raw material delivery pump and the second condenser, and then transported to the second cryogenic distillation equipment. The N2 extracted from the top of the second cryogenic distillation equipment is discharged, and high-purity CH4 is separated from the bottom of the tower. It is further condensed and dried by the natural gas condensation and drying equipment, pressurized and liquefied by the natural gas pressure liquefaction equipment, and then transported to the external natural gas transportation pipeline network; S3, the water electrolysis hydrogen production equipment which is powered by clean energy power generation equipment produces high purity hydrogen; S4. The high-purity CO2 separated at the bottom of the first low-temperature distillation equipment and the H2 produced by the water electrolysis hydrogen production equipment are mixed in proportion in a gas mixer, and then preheated by a heat exchanger and enter a multi-stage heat transfer type ultra-gravity reactor; in the multi-stage heat transfer type ultra-gravity reactor, they alternately pass through a rotating reaction module and a fixed heat transfer module to perform CO2 methanation reaction and heat exchange respectively, and finally the product is condensed by a third condenser to obtain natural gas that meets the requirements, and is further condensed and dried by a natural gas condensation and drying equipment, pressurized and liquefied by a natural gas pressurized liquefaction equipment, and then transported to the external natural gas transportation pipeline network.

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