LNG cold energy carbon dioxide hydrate generation and ocean storage system and method

Abstract

The invention discloses an LNG cold energy carbon dioxide hydrate generation and ocean storage system and method, and belongs to the field of carbon dioxide conveying and storage. The system comprises an LNG gasification system, a cold energy continuous supply system, a pre-cooling system, a pressurization system, a hydrate generation system and a hydrate pipeline conveying system. The LNG gasification system and the cold energy continuous supply system continuously transfer cold energy released by LNG gasification to CO2 and seawater, the pre-cooling system and the pressurization system conduct pre-cooling and pressurization conveying of CO2 and seawater, the hydrate generation system prepares hydrate through CO2 and seawater, and the hydrate pipeline conveying system conveys the hydrate to a seabed reservoir through a pipeline. Liquid ammonia is used as a refrigerant to store cold energy released by LNG gasification, and continuous supply of the cold energy is ensured; the hydrate is rapidly and continuously prepared through continuous cold supply, pre-cooling, double reaction kettles, continuous stirring, cold insulation and gas-liquid circulation; hydrates and seawater are mixed and conveyed in proportion, and the hydrate slurry pipeline conveying efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the field of carbon dioxide transportation and storage, and in particular relates to a system and method for generating carbon dioxide hydrate using LNG cold energy and storing it in the ocean. Background Art

[0002] The utilization of LNG cold energy has received widespread attention in recent years. LNG is a natural gas cooled to about -162℃ and liquefied, and stored in LNG storage tanks. LNG generates a large amount of cold energy during the gasification process, which is a high-quality, low-cost energy. LNG cold energy can be used to provide air separation, refrigeration, power generation, etc., but its current scope of use is narrow and its utilization efficiency is low. Since the formation of carbon dioxide hydrate requires a low-temperature environment, the use of LNG cold energy to prepare carbon dioxide hydrate can improve the utilization efficiency of cold energy and reduce the energy consumption of cold energy manufacturing equipment during the formation of carbon dioxide hydrate.

[0003] Carbon dioxide is one of the main causes of global warming and extreme climate events. Therefore, a variety of carbon dioxide capture and storage methods have been proposed to cope with climate change, among which carbon dioxide hydrate storage is one of the most promising technologies. Carbon dioxide combines with water at a low temperature of about 1°C and a pressure of 1.5MPa to form solid hydrates, similar to "ice", and can be stored for a long time in the low temperature and high pressure environment of the seabed reservoir. Carbon dioxide mainly comes from coastal thermal power plants and chemical plants. The carbon dioxide produced by the plant is captured and transported to the carbon dioxide storage and transportation point near the LNG receiving station, and then the cold energy generated by the gasification of LNG is used to prepare carbon dioxide hydrates. This method reduces energy consumption in the preparation process, achieves energy saving and consumption reduction, and provides a new way for large-scale carbon dioxide capture and storage, which helps to achieve the goal of carbon neutrality.

[0004] At present, there are many problems in using LNG cold energy to generate carbon dioxide hydrates. For example, in summer, when gas consumption decreases, LNG is supplied to downstream users through intermittent gasification. When LNG stops gasifying, the supply of cold energy decreases and is insufficient to provide the cold energy required for hydrate formation. In addition, after carbon dioxide hydrates meet the formation conditions, they need to go through a certain induction period before they can be generated, and the synthesis rate of carbon dioxide hydrates is affected by factors such as the degree of supercooling in the generation environment. Increasing the degree of supercooling can effectively increase the generation rate. Therefore, if the continuous preparation and marine storage of carbon dioxide hydrates using LNG cold energy is to be realized, the problem of continuous supply of LNG cold energy must be solved, and the efficiency of hydrate preparation must be improved at the same time. Through investigation, it was found that in the "A Hydrate Cold Storage and Supply System Based on LNG Cold Energy" with patent number CN116907153A, LNG cold energy was used to generate hydrates, but in summer, users' demand for natural gas is reduced, and LNG is supplied by intermittent gasification. When LNG stops gasification, it is impossible to use LNG cold energy to generate carbon dioxide hydrates. For example, in the "A Method for Marine Storage of Carbon Dioxide Hydrates" with patent number CN116040138 B, this method cannot achieve the effect of continuous preparation in the hydrate preparation method. The present invention prepares carbon dioxide hydrates using LNG cold energy, and through the continuous supply of cold energy and the continuous hydrate generation process, it is expected to solve the problem of continuous hydrate preparation, and ultimately solve the marine storage of carbon dioxide hydrates. Summary of the invention

[0005] Aiming at some problems in the existing field of carbon dioxide hydrate storage, the present invention proposes a carbon dioxide hydrate generation and marine storage system and method using LNG cold energy.

[0006] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0007] The LNG gasification system and the cold energy continuous supply system are used to provide the cold energy required for the subsequent formation of carbon dioxide hydrate.

[0008] The LNG gasification system includes an LNG storage tank, an LNG pump, an LNG gasification processing device, and a condenser; the specific connection relationship is: the output end of the LNG storage tank is connected to the input end of the LNG pump, the output end of the LNG pump is connected to the input end of the condenser, the output end of the condenser is connected to the input end of the LNG gasification processing device, and the output end of the LNG gasification processing device is connected to the downstream user;

[0009] Furthermore, the LNG in the LNG storage tank is transported under pressure by an LNG pump, then releases cold energy through a condenser, and finally is gasified into natural gas through a gasification processing device and then sent to downstream users.

[0010] Furthermore, the LNG gasification system also includes a first pressure sensor, a first temperature sensor, a second pressure sensor, a second temperature sensor and a first flow meter, the pressure sensor is used to monitor the pressure of the LNG, the temperature sensor is used to monitor the temperature of the LNG, and the flow meter is used to measure the flow of the LNG.

[0011] The cold energy continuous supply system comprises a liquid ammonia storage tank, a liquid ammonia pump, a first vaporizer, a second vaporizer, an ammonia storage tank, a condenser and a first centrifugal compressor; the specific connection relationship is: the output end of the liquid ammonia storage tank is connected to the input end of the liquid ammonia pump, the output end of the liquid ammonia pump is connected to the input end of the first vaporizer, the output end of the first vaporizer is connected to the input end of the second vaporizer, the output end of the second vaporizer is connected to the input end of the ammonia storage tank, the output end of the ammonia storage tank is connected to the input end of the first centrifugal compressor, the output end of the first centrifugal compressor is connected to the input end of the condenser, and the output end of the condenser is returned and connected to the input end of the liquid ammonia storage tank, forming a complete circulation path;

[0012] Furthermore, the cold energy continuous supply system also includes a third pressure sensor, a third temperature sensor, a fourth pressure sensor, a fourth temperature sensor and a second flow meter, the pressure sensor is used to monitor the liquid ammonia pressure, the temperature sensor is used to monitor the liquid ammonia temperature, and the flow meter is used to measure the liquid ammonia flow.

[0013] Furthermore, the cold energy continuous supply system also includes a fifth pressure sensor, a fifth temperature sensor, a sixth pressure sensor, a sixth temperature sensor and a third flow meter, the pressure sensor is used to monitor the ammonia pressure, the temperature sensor is used to monitor the ammonia temperature, and the flow meter is used to measure the ammonia flow.

[0014] Furthermore, the liquid ammonia changes from liquid to gas after being vaporized by the first vaporizer and the second vaporizer, and is stored in an ammonia storage tank; the ammonia gas is then pressurized by the first centrifugal compressor, and then condensed into liquid ammonia again by the condenser, and refluxed to the liquid ammonia storage tank, thereby realizing the gas-liquid recycling of ammonia; at the same time, the cold energy obtained by the first vaporizer and the second vaporizer is transferred to carbon dioxide and seawater.

[0015] Furthermore, when the LNG gasification system is working, it provides cooling capacity to the condenser, and the ammonia gas is liquefied into liquid ammonia and stored in the liquid ammonia storage tank. At the same time, the gas-liquid circulation of liquid ammonia and ammonia gas provides cooling capacity to the first gasifier and the second gasifier. This process can provide cooling capacity through the gas-liquid conversion of liquid ammonia and ammonia gas, and can also utilize the liquefaction of ammonia gas into liquid ammonia to store cooling capacity. When the LNG gasification system stops working, the gas-liquid conversion of liquid ammonia and ammonia gas can be utilized to provide cooling capacity to the first gasifier and the second gasifier, thereby realizing the continuous provision of cooling capacity required for the subsequent continuous preparation of hydrates.

[0016] The precooling system, the pressurizing system, the hydrate generation system and the hydrate pipeline transportation system are used to transport the precooled carbon dioxide and seawater to two reactors respectively to generate hydrates, and effectively separate the unreacted carbon dioxide, unreacted seawater and generated hydrates through a three-phase separator; the unreacted carbon dioxide is transported to the carbon dioxide pipeline at the outlet of the low-temperature precooling water tank through a pipeline and before the second centrifugal compressor; the unreacted seawater is transported to the seawater pipeline at the bottom outlet of the low-temperature precooling water tank through a pipeline and before the pressure pump; the hydrate enters the slurry storage and distribution tank through the bottom outlet of the three-phase separator, the seawater in the slurry storage and distribution tank is provided by the low-temperature precooling water tank, the seawater in the slurry storage and distribution tank that passes through the low-temperature precooling water tank is volume-proportioned with hydrates, and the hydrate slurry formed by the proportioned seawater and hydrates is transported to the bottom of the seabed reservoir through the hydrate slurry transportation pipeline for sealing.

[0017] The precooling system comprises a low-temperature precooling water tank and a first vaporizer; the cold energy transmitted by the first vaporizer is used for precooling the low-temperature precooling water tank, the low-temperature precooling water tank is equipped with seawater and carbon dioxide pipelines, the carbon dioxide pipeline is connected to the low-temperature precooling water tank to precool under the low-temperature environment, and the seawater pipeline is connected to inject seawater into the low-temperature precooling water tank for precooling;

[0018] Furthermore, the low-temperature precooling water tank is provided with a fifteenth temperature sensor for monitoring the temperature inside the low-temperature precooling water tank 61, and by monitoring the temperature change, the release of the cooling capacity of the first vaporizer is controlled to improve the utilization efficiency of the cooling capacity.

[0019] Furthermore, the external carbon dioxide and seawater pass through the low-temperature precooling water tank, and the internal temperature is controlled at 4-6°C, which is used for precooling carbon dioxide and seawater; due to the high temperature of the external seawater and carbon dioxide, precooling is beneficial to reduce the load of the gasifier, increase the supercooling degree of the subsequent hydrate generation environment, shorten the induction period of hydrate growth, and ultimately increase the hydrate generation rate. Further, the volume of seawater inside the low-temperature precooling water tank is controlled at 90% of the volume of the low-temperature precooling water tank, which is used to improve the utilization efficiency of the low-temperature precooling water tank and to have sufficient precooled seawater and hydrate volume ratio when the hydrate slurry is transported in the subsequent hydrate pipeline transportation system.

[0020] The pressurizing system comprises a pressurizing pump, a second centrifugal compressor, a low-temperature precooling water tank, a first high-pressure reactor and a second high-pressure reactor; the specific connection relationship is: the seawater output end at the bottom end of the low-temperature precooling water tank is connected to the input end of the pressurizing pump, the pressurizing pump has two output ends, the first output end of the pressurizing pump is connected to the liquid phase input end of the first high-pressure reactor, and the second output end of the pressurizing pump is connected to the liquid phase input end of the second high-pressure reactor; the carbon dioxide pipeline is precooled by the low-temperature precooling water tank and then connected to the input end of the second centrifugal compressor, the second centrifugal compressor has two output ends, the first output end of the second centrifugal compressor is connected to the gas phase input end of the first high-pressure reactor, and the second output end of the second centrifugal compressor is connected to the gas phase input end of the second high-pressure reactor;

[0021] Furthermore, the booster pump is used to increase the delivery pressure of seawater and transport seawater; the second centrifugal compressor is used to increase the delivery pressure of carbon dioxide and transport carbon dioxide; the two output ends of the booster pump are respectively connected to the liquid phase input ends of the two reactors, and the two output ends of the second centrifugal compressor are respectively connected to the gas phase input ends of the two reactors.

[0022] Furthermore, the second centrifugal compressor in the pressurizing system is equipped with a seventh pressure sensor, a seventh temperature sensor, an eighth pressure sensor, an eighth temperature sensor, a fifth flowmeter and a seventh flowmeter before and after; wherein the pressure sensor is used to monitor the pressure of carbon dioxide, the temperature sensor is used to monitor the temperature of carbon dioxide, and the flowmeter is used to measure the flow of carbon dioxide; at the same time, the pressurizing pump is equipped with a ninth pressure sensor, a ninth temperature sensor, a tenth pressure sensor, a tenth temperature sensor, a fourth flowmeter and a sixth flowmeter before and after; the pressure sensor is used to monitor the pressure of seawater, the temperature sensor is used to monitor the temperature of seawater, and the flowmeter is used to measure the flow of seawater.

[0023] The hydrate generation system comprises a low-temperature precooling water tank, a booster pump, a second centrifugal compressor, a first high-pressure reactor, a second high-pressure reactor, a first agitator, a second agitator, a second gasifier and a three-phase separator; the specific connection relationship is: the two output ends of the booster pump are respectively connected to the liquid phase input ends of the first high-pressure reactor and the second high-pressure reactor; the two output ends of the second centrifugal compressor are respectively connected to the gas phase input ends of the first high-pressure reactor and the second high-pressure reactor; the output ends at the bottom ends of the first high-pressure reactor and the second high-pressure reactor are connected to the input end at the top end of the three-phase separator; the gas phase output end at the top of the three-phase separator is connected to the carbon dioxide pipeline at the output end of the low-temperature precooling water tank and before the second centrifugal compressor; the liquid phase output end at the top of the three-phase separator is connected to the seawater pipeline at the output end of the bottom end of the low-temperature precooling water tank and before the booster pump; the solid phase output end at the bottom end of the three-phase separator is connected to the hydrate pipeline transportation system;

[0024] Furthermore, carbon dioxide and seawater enter the first high-pressure reactor and the second high-pressure reactor, and the internal pressure is maintained at 5 MPa. At the same time, the release of the cold capacity of the second gasifier is controlled to control the temperature of the two reactors at 0.5-1.5°C, and the internal environment is maintained at a low temperature and high pressure, in which hydrates will be generated; at the same time, there is a large degree of supercooling inside, and through the continuous stirring of the first agitator and the second agitator, the induction time is significantly shortened, and hydrates are quickly generated.

[0025] Furthermore, the first high-pressure reactor is equipped with an eleventh pressure sensor and an eleventh temperature sensor; the second high-pressure reactor is equipped with a twelfth pressure sensor and a twelfth temperature sensor; the pressure sensor is used to monitor the pressure of the two reactors, and the temperature sensor is used to monitor the temperature of the two reactors.

[0026] Furthermore, the hydrates generated by the two reactors pass through a three-phase separator, and an insulation layer is applied outside the three-phase separator to prevent the loss of cold. After the unreacted carbon dioxide is transported to the carbon dioxide pipeline at the output end of the low-temperature precooling water tank through the gas phase output end at the top of the three-phase separator, an insulation layer is applied outside the pipeline in front of the second centrifugal compressor. After the unreacted seawater is transported to the seawater pipeline at the bottom output end of the low-temperature precooling water tank through the liquid phase output end at the top of the three-phase separator, an insulation layer is applied outside the pipeline in front of the booster pump. The hydrates separated from the bottom solid phase output end are transported to the hydrate pipeline transportation system.

[0027] Furthermore, in the hydrate generation system, hydrates are prepared through two reactors, and a three-phase separator is used to separate unreacted carbon dioxide, unreacted seawater and hydrates; since carbon dioxide is dissolved in the unreacted seawater, this part of the seawater will subsequently generate a part of hydrates, and in order to improve the storage efficiency of carbon dioxide, the carbon dioxide and seawater are transported through pipelines to re-enter the two reactors for hydrate preparation; and the generated hydrates are separated through the solid phase output end at the bottom of the three-phase separator and enter the hydrate pipeline transportation system, and an insulation layer is applied outside the pipeline; in the hydrate preparation process, the carbon dioxide pipeline and the seawater pipeline form a cycle, and at the same time, the LNG gasification system and the cold energy continuous supply system are used to provide continuous cold energy, thereby ultimately realizing the continuous preparation of hydrates.

[0028] The hydrate pipeline transportation system comprises a low-temperature precooling water tank, a three-phase separator, a slurry storage and distribution tank, a mixed transfer pump, and a hydrate slurry transportation pipeline; the specific connection relationship is: the solid phase output end at the bottom of the three-phase separator is connected to the input end at the top of the slurry storage and distribution tank, the output end at the bottom of the low-temperature precooling water tank is connected to the input end at the bottom of the slurry storage and distribution tank, the output end at the bottom of the slurry storage and distribution tank is connected to the input end of the mixed transfer pump, and the output end of the mixed transfer pump is connected to the hydrate slurry transportation pipeline; the pipeline between the seawater outlet at the bottom of the low-temperature precooling water tank and the inlet at the bottom of the slurry storage and distribution tank and the pipelines before and after the mixed transfer pump are all laid with a thermal insulation layer;

[0029] Furthermore, hydrates and seawater enter a slurry storage and distribution tank, and the volume ratio of low-temperature seawater and hydrates in the slurry storage and distribution tank is controlled. The hydrate slurry formed after stirring is stirred by a third agitator, and then is transported to the seabed reservoir through a mixing pump and a hydrate slurry transportation pipeline for hydrate sealing.

[0030] Furthermore, the slurry storage and distribution tank mixes hydrates and seawater in a certain volume ratio. The volume ratio of the liquid-solid mixture is determined according to the characteristics of the hydrate particles (size, shape, density), the characteristics of the seawater (viscosity, surface tension), the characteristics of the transportation pipeline (diameter, roughness, etc.) and the transportation pressure. The hydrate slurry is then transported to the seabed reservoir through the booster of the mixing pump using the hydrate slurry transportation pipeline.

[0031] Furthermore, the hydrate pipeline transportation system also includes a thirteenth pressure sensor, a thirteenth temperature sensor, a fourteenth pressure sensor, a fourteenth temperature sensor and an eighth flow meter; the pressure sensor is used to monitor the hydrate slurry pressure, the temperature sensor is used to monitor the hydrate slurry temperature, and the flow meter is used to measure the hydrate slurry flow.

[0032] Furthermore, in the hydrate pipeline transportation system, the hydrate slurry transportation pipeline should be provided with an insulation layer to keep the pipeline cold so as to prevent the decomposition of hydrates and the escape of carbon dioxide; the temperature of the seabed decreases with the increase of depth; therefore, when the pipeline reaches a certain depth on the seabed, the insulation layer may not be laid, which can reduce the cost during construction; when the temperature at a certain location on the seabed is detected to be 1°C, the hydrate slurry transportation pipeline is provided with an insulation layer above the location, and no insulation layer may be laid below the location.

[0033] Furthermore, all pressure sensors, temperature sensors and flow sensors in the LNG gasification system, cold energy continuous supply system, precooling system, pressurization system, hydrate generation system and hydrate pipeline transportation system transmit pressure, temperature and flow information to the computer data acquisition device to monitor the operating conditions in real time.

[0034] Furthermore, one-way stop valves are provided at the output ends of the LNG pump, liquid ammonia pump, first centrifugal compressor, second centrifugal compressor, booster pump and mixed transfer pump to prevent backflow of fluid, maintain the pressure of each system, and ensure normal inflow and outflow of fluid.

[0035] Furthermore, regulating valves are installed in the LNG gasification system, cold energy continuous supply system, precooling system, pressurization system, hydrate generation system, and hydrate pipeline transportation system to adjust the flow rate of the fluid in each system.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. By utilizing the cold energy generated by LNG gasification to prepare carbon dioxide hydrate, the related cold energy manufacturing equipment is reduced, and the energy consumption in the process of carbon dioxide hydrate generation is greatly reduced.

[0038] 2. First, cold energy is used to precool carbon dioxide and seawater, and then precooling is performed again in the two reactors to generate hydrates. The carbon dioxide and seawater are precooled twice to reduce the load of the gasifier and make the gasifier work more stably. At the same time, an insulation layer is laid on the carbon dioxide and seawater reinjection pipelines, and an insulation layer is laid on the outside of the three-phase separator and in the hydrate pipeline transportation system. The above-mentioned two precooling and cold preservation measures realize efficient utilization of cold energy.

[0039] 3. When the LNG gasification system is working, ammonia gas is condensed into liquid ammonia and stored in a liquid ammonia storage tank. At the same time, the gas-liquid circulation of liquid ammonia and ammonia gas is used to provide cooling for hydrate formation. This process can not only provide sufficient cooling for hydrate formation, but also store sufficient cooling. When the LNG gasification system stops working, cooling continues to be provided through the gas-liquid conversion between liquid ammonia and ammonia gas, thereby achieving a continuous supply of cooling required for hydrate formation.

[0040] 4. Hydrates are prepared by continuous cold supply, precooling, double reactors, and continuous stirring; a three-phase separator is used to separate the prepared hydrates, unreacted carbon dioxide, and unreacted seawater; the separated unreacted carbon dioxide and seawater are transported through pipelines and then enter the two reactors; at the same time, an insulation layer is laid outside the carbon dioxide reinjection pipeline, the seawater reinjection pipeline, and the three-phase separator to provide cold preservation measures, thereby ultimately achieving continuous preparation of hydrates.

[0041] 5. The hydrate and seawater in the slurry storage tank are mixed by adjusting the volume ratio of liquid to solid, and agitators are used for stirring, thereby fully improving the efficiency of pipeline transportation of hydrate slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1This is a flow chart of a carbon dioxide hydrate generation and ocean storage system of LNG cold energy according to the present invention.

[0043] Figure 2 This is a schematic diagram of a carbon dioxide hydrate generation and ocean storage system for LNG cold energy according to the present invention.

[0044] Figure 2 In: 1LNG storage tank, 2 first pressure sensor, 3 first temperature sensor, 4LNG pump, 5 second pressure sensor, 6 first regulating valve, 7 second temperature sensor, 8 first one-way stop valve, 9 first flow meter, 10 second regulating valve, 11 gasification processing equipment, 12 liquid ammonia storage tank, 13 third regulating valve, 14 third pressure sensor, 15 third temperature sensor, 16 liquid ammonia pump, 17 second one-way stop valve, 18 fourth pressure sensor, 19 fourth temperature sensor, 20 second flow meter, 21 fourth regulating valve, 22 condenser, 23 third flow meter, 2 4 fifth pressure sensor, 25 fifth temperature sensor, 26 third one-way stop valve, 27 first centrifugal compressor, 28 sixth pressure sensor, 29 sixth temperature sensor, 30 fifth regulating valve, 31 sixth regulating valve, 32 seventh regulating valve, 33 ammonia storage tank, 34 computer data acquisition device, 35 fifteenth temperature sensor, 36 first vaporizer, 37 low temperature precooling water tank, 38 eighth regulating valve, 39 seventh pressure sensor, 40 seventh temperature sensor, 41 second centrifugal compressor, 42 fourth one-way stop valve, 43 eighth pressure sensor, 44 eighth temperature sensor, 45 ninth regulating valve, 46 ninth pressure sensor, 47 ninth temperature sensor, 48 booster pump, 49 fifth one-way stop valve, 50 tenth pressure sensor, 51 tenth temperature sensor, 52 fourth flow meter, 53 tenth regulating valve, 54 fifth flow meter, 55 eleventh regulating valve, 56 sixth flow meter, 57 twelfth regulating valve, 58 seventh flow meter, 59 thirteenth regulating valve, 60 eleventh pressure sensor, 61 eleventh temperature sensor, 62 second vaporizer, 63 first high-pressure reactor, 64 first agitator, 65 twelfth pressure sensor , 66 the twelfth temperature sensor, 67 the second high-pressure reactor, 68 the second agitator, 69 the fourteenth regulating valve, 70 the three-phase separator, 71 the fifteenth regulating valve, 72 the sixteenth regulating valve, 73 the insulation layer, 74 the seventeenth regulating valve, 75 the eighteenth regulating valve, 76 the slurry storage and distribution tank, 77 the third agitator, 78 the nineteenth regulating valve, 79 the thirteenth pressure sensor, 80 the thirteenth temperature sensor, 81 the mixed transport pump, 82 the fourteenth pressure sensor, 83 the fourteenth temperature sensor, 84 the sixth one-way stop valve, 85 the eighth flow meter, 86 the hydrate slurry transportation pipeline. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the accompanying drawings. The described embodiments are only examples of some aspects of the present invention, not all implementation methods.

[0046] The present invention is a system and method for generating and storing carbon dioxide hydrates using LNG cold energy in the ocean. Figure 2 As shown, it includes LNG gasification system, cold energy continuous supply system, precooling system, pressurization system, hydrate generation system and hydrate pipeline transportation system.

[0047] The present invention is a system and method for generating and storing carbon dioxide hydrates using LNG cold energy in the ocean. Figure 2As shown, it includes: 1 LNG storage tank, 2 first pressure sensor, 3 first temperature sensor, 4 LNG pump, 5 second pressure sensor, 6 first regulating valve, 7 second temperature sensor, 8 first one-way stop valve, 9 first flow meter, 10 second regulating valve, 11 gasification processing equipment, 12 liquid ammonia storage tank, 13 third regulating valve, 14 third pressure sensor, 15 third temperature sensor, 16 liquid ammonia pump, 17 second one-way stop valve, 18 fourth pressure sensor, 19 fourth temperature sensor, 20 second flow meter, 21 fourth regulating valve, 22 condenser, 23 third flow meter, 24 fifth pressure sensor, 25 fifth temperature sensor, 26 third one-way stop valve, 27 first centrifugal compressor, 28 sixth pressure sensor, 29 sixth temperature sensor, 30 fifth regulating valve, 31 sixth regulating valve, 32 seventh regulating valve, 33 ammonia storage tank, 34 computer data acquisition device, 35 fifteenth temperature sensor, 36 first vaporizer, 37 low temperature precooling water tank, 38 eighth regulating valve, 39 seventh pressure sensor, 40 seventh temperature sensor, 41 second centrifugal compressor, 42 fourth one-way stop valve, 43 eighth pressure sensor, 44 eighth temperature sensor, 45 ninth regulating valve, 46 ninth pressure sensor, 47 ninth temperature sensor, 48 pressure pump, 49 fifth one-way stop valve, 50 tenth pressure sensor, 51 tenth temperature sensor, 52 fourth flow meter, 53 tenth regulating valve, 54 fifth flow meter, 55 eleventh regulating valve, 56 sixth flow meter, 57 twelfth regulating valve, 58 seventh flow meter, 59 thirteenth regulating valve, 60 eleventh pressure sensor, 61 eleventh temperature sensor, 62 second vaporizer, 63 first high pressure reactor, 64 first agitator, 65 twelfth pressure sensor device, 66 the twelfth temperature sensor, 67 the second high-pressure reactor, 68 the second agitator, 69 the fourteenth regulating valve, 70 the three-phase separator, 71 the fifteenth regulating valve, 72 the sixteenth regulating valve, 73 the insulation layer, 74 the seventeenth regulating valve, 75 the eighteenth regulating valve, 76 the slurry storage and distribution tank, 77 the third agitator, 78 the nineteenth regulating valve, 79 the thirteenth pressure sensor, 80 the thirteenth temperature sensor, 81 the mixed transport pump, 82 the fourteenth pressure sensor, 83 the fourteenth temperature sensor, 84 the sixth one-way stop valve, 85 the eighth flow meter, 86 the hydrate slurry transportation pipeline.

[0048] Embodiment 1:

[0049] In this embodiment, the LNG gasification system is used to obtain cold energy from LNG gasification and gasify LNG into natural gas before sending it to downstream users; it includes an LNG storage tank 1, an LNG pump 4, a condenser 22, and a gasification processing equipment 11; the output end of the LNG storage tank 1 is connected to the input end of the LNG pump 4, the output end of the LNG pump 4 is connected to the input end of the condenser 22, the output end of the condenser 22 is connected to the input end of the gasification processing equipment 11, and the output end of the gasification processing equipment 11 is connected to the downstream users; the LNG from the LNG storage tank 1 is pressurized and transported by the LNG pump 4, then releases the cold energy through the condenser 22, and finally is gasified into natural gas through the gasification processing equipment 11 and sent to downstream users.

[0050] In this embodiment, a first regulating valve 6 is arranged in front of the LNG pump 4, and a first one-way stop valve 8 is arranged behind the LNG pump 4, so as to adjust the LNG flow rate while ensuring that the LNG pump 4 can operate stably; a second regulating valve 10 is arranged in front of the gasification processing equipment 11, so as to adjust the amount of gas going to downstream users; a first pressure sensor 2 and a first temperature sensor 3 are arranged in front of the LNG pump 4, and a second pressure sensor 5, a second temperature sensor 7 and a first flow meter 9 are arranged behind the LNG pump 4. The pressure sensor is used to monitor the LNG pressure, the temperature sensor is used to monitor the LNG temperature, and the flow meter is used to measure the LNG flow rate.

[0051] In this embodiment, the data of all pressure sensors, temperature sensors, and flow meters are collected by a computer data acquisition device 34 for real-time monitoring of operating conditions.

[0052] Embodiment 2:

[0053] In this embodiment, the cold energy continuous supply system is used to provide cold energy to carbon dioxide and seawater; the cold energy continuous supply system includes a liquid ammonia storage tank 12, a liquid ammonia pump 16, a first vaporizer 36, a second vaporizer 62, an ammonia storage tank 33, a condenser 22, and a first centrifugal compressor 27; the output end of the liquid ammonia storage tank 12 is connected to the input end of the liquid ammonia pump 16, the output end of the liquid ammonia pump 16 is connected to the input end of the first vaporizer 36, the output end of the first vaporizer 36 is connected to the input end of the second vaporizer 62, the output end of the second vaporizer 62 is connected to the input end of the ammonia storage tank 33, the output end of the ammonia storage tank 33 is connected to the input end of the first centrifugal compressor 27, the output end of the first centrifugal compressor 27 is connected to the input end of the condenser 22, and the output end of the condenser 22 is connected to the input end of the liquid ammonia storage tank 12, forming a complete circulation pipeline; the liquid ammonia is gasified in the first vaporizer 36 and the second vaporizer 62 to release the LNG cold and then transferred to the carbon dioxide and seawater.

[0054] In this embodiment, a second one-way stop valve 17 is provided after the liquid ammonia pump 16 to ensure the stable operation of the liquid ammonia pump 16; a third regulating valve 13 is provided before the liquid ammonia pump 16, and a sixth regulating valve 31 is provided between the first vaporizer 36 and the second vaporizer 62 to adjust the release of cold; a seventh regulating valve 32 is provided between the second vaporizer 62 and the ammonia storage tank 33 to adjust the intake amount of ammonia; a fifth regulating valve 30 is provided between the ammonia storage tank 33 and the condenser 22, and a third one-way stop valve 26 is provided after the first centrifugal compressor 27 to adjust the outlet amount of ammonia and ensure the stable operation of the first centrifugal compressor 27; a third one-way stop valve 26 is provided before the liquid ammonia pump 16 There are three pressure sensors 14 and a third temperature sensor 15, a fourth pressure sensor 18, a fourth temperature sensor 19 and a second flow meter 20 arranged behind the liquid ammonia pump 16, the pressure sensor is used to monitor the liquid ammonia pressure, the temperature sensor is used to monitor the liquid ammonia temperature, and the flow meter is used to measure the liquid ammonia flow rate; a sixth pressure sensor 28 and a sixth temperature sensor 29 are arranged in front of the first centrifugal compressor 27, a fifth pressure sensor 24, a fifth temperature sensor 25 and a third flow meter 23 are arranged behind the first centrifugal compressor 27, the pressure sensor is used to monitor the ammonia pressure, the temperature sensor is used to monitor the ammonia temperature, and the flow meter is used to measure the ammonia flow rate.

[0055] In this embodiment, the data of all pressure sensors, temperature sensors, and flow meters are collected by a computer data acquisition device 34 for real-time monitoring of operating conditions.

[0056] In this embodiment, when the LNG gasification system is working, cooling is provided to the condenser 22, and ammonia gas is condensed into liquid ammonia and stored in the liquid ammonia storage tank 12. At the same time, the gas-liquid circulation of liquid ammonia and ammonia gas provides cooling to the first gasifier 36 and the second gasifier 62. At this time, cooling can be provided by the circulation of liquid ammonia and ammonia gas, and cooling can be stored by liquefying ammonia gas into liquid ammonia. When the LNG gasification system stops working, cooling can be provided to the first gasifier 36 and the second gasifier 62 by the gas-liquid circulation of liquid ammonia and ammonia gas, thereby realizing the continuous provision of cooling required for the subsequent continuous preparation of hydrates.

[0057] Embodiment 3:

[0058] In this embodiment, the precooling system is used to precool carbon dioxide and seawater; it includes a low-temperature precooling water tank 37 and a first vaporizer 36. The first vaporizer 36 transfers LNG cooling capacity for precooling the low-temperature precooling water tank 37. The interior of the low-temperature precooling water tank 37 is a carbon dioxide pipeline and seawater. The carbon dioxide pipeline is connected to the low-temperature precooling water tank 37 to be fully precooled under the low-temperature environment inside the low-temperature precooling water tank 37, and the seawater pipeline is connected to inject seawater into the low-temperature precooling water tank 37 for precooling; the temperature of the low-temperature precooling water tank 37 is controlled at 4-6°C by controlling the first vaporizer 36, and 90% of the volume capacity of the low-temperature precooling water tank 37 is maintained at seawater.

[0059] In this embodiment, the low-temperature pre-cooling water tank 37 is equipped with a fifteenth temperature sensor 35, which is used to monitor the temperature inside the low-temperature pre-cooling water tank 37. By monitoring the temperature changes, the release of cold energy from the first gasifier 36 is controlled to improve the utilization efficiency of cold energy; and the temperature data is collected through the computer data acquisition device 34.

[0060] In this embodiment, the volume of seawater inside the low-temperature precooling water tank 37 is controlled to be 90% of the volume of the low-temperature precooling water tank 37, so as to improve the utilization efficiency of the low-temperature precooling water tank 37 and ensure that there is sufficient precooled seawater and hydrate volume ratio during the subsequent hydrate pipeline transportation in the hydrate pipeline transportation system.

[0061] In this embodiment, before the carbon dioxide and seawater enter the first high-pressure reactor 63 and the second high-pressure reactor 67 to prepare hydrates, pre-cooling is first performed, which is beneficial to reducing the load of the two gasifiers, increasing the supercooling degree of the subsequent hydrate generation environment, shortening the induction period of hydrate growth, and increasing the hydrate generation rate.

[0062] Embodiment 4:

[0063] In this embodiment, the pressurizing system is used to pressurize and transport carbon dioxide and seawater; it includes a pressurizing pump 48, a second centrifugal compressor 41, a low-temperature precooling water tank 37, a first high-pressure reactor 63, and a second high-pressure reactor 67; the seawater output end at the bottom of the low-temperature precooling water tank 37 is connected to the input end of the pressurizing pump 48, and the pressurizing pump 48 has two output ends, the first output end of the pressurizing pump 48 is connected to the liquid phase input end of the first high-pressure reactor 63, and the second output end of the pressurizing pump 48 is connected to the liquid phase input end of the second high-pressure reactor 67; the carbon dioxide pipeline is precooled by the low-temperature precooling water tank 37 and connected to the input end of the second centrifugal compressor 41, and the second centrifugal compressor 41 has two output ends, the first output end of the second centrifugal compressor 41 is connected to the gas phase input end of the first high-pressure reactor 63, and the second output end of the second centrifugal compressor 41 is connected to the gas phase input end of the second high-pressure reactor 67; the carbon dioxide and seawater are pressurized and transported to the hydrate formation system through the pressurizing pump 48 and the second centrifugal compressor 41.

[0064] In this embodiment, a ninth regulating valve 45 is provided in front of the booster pump 48, and a fifth one-way stop valve 49 is provided behind the booster pump 48, so as to adjust the flow rate of seawater while ensuring that the booster pump 48 can operate stably; an eighth regulating valve 38 is provided in front of the second centrifugal compressor 41, and a fourth one-way stop valve 42 is provided behind the second centrifugal compressor 41, so as to adjust the flow rate of carbon dioxide while ensuring that the second centrifugal compressor 41 can operate stably; a seventh pressure sensor 39 and a seventh temperature sensor 40 are installed in front of the second centrifugal compressor 41, and an eighth pressure sensor 43, an eighth temperature sensor 44, a fifth flow meter 54 and a seventh flow meter 58 are installed behind the second centrifugal compressor 41. The pressure sensor is used to monitor the pressure of carbon dioxide, and the temperature sensor is used to monitor the pressure of carbon dioxide. The sensor is used to monitor the temperature of carbon dioxide, and the flowmeter is used to measure the flow of carbon dioxide; the ninth pressure sensor 46 and the ninth temperature sensor 47 are installed in front of the booster pump 48, and the tenth pressure sensor 50, the tenth temperature sensor 51, the fourth flowmeter 52 and the sixth flowmeter 56 are installed behind the booster pump 48. The pressure sensor is used to monitor the pressure of seawater, the temperature sensor is used to monitor the temperature of seawater, and the flowmeter is used to measure the flow of seawater; the tenth regulating valve 53 and the twelfth regulating valve 57 are set at the two output ends of the booster pump 48 to control the flow of seawater entering the next-level system; the eleventh regulating valve 55 and the thirteenth regulating valve 59 are set at the two output ends of the second centrifugal compressor 41 to control the flow of carbon dioxide entering the next-level system.

[0065] In this embodiment, the data of all pressure sensors, temperature sensors, and flow meters are collected by a computer data acquisition device 34 for real-time monitoring of operating conditions.

[0066] Embodiment 5:

[0067] The hydrate generation system is used for generating carbon dioxide hydrate; it comprises a low-temperature precooling water tank 37, a booster pump 48, a second centrifugal compressor 41, a first high-pressure reactor 63, a second high-pressure reactor 67, a first agitator 64, a second agitator 68, a second gasifier 62, and a three-phase separator 70; the two output ends of the booster pump 48 are respectively connected to the liquid phase input ends of the first high-pressure reactor 63 and the second high-pressure reactor 67, the two output ends of the second centrifugal compressor 41 are respectively connected to the gas phase input ends of the first high-pressure reactor 63 and the second high-pressure reactor 67; the first high-pressure reactor 63 The output end at the bottom of the second high-pressure reactor 67 is connected to the input end at the top of the three-phase separator 70; the gas phase output end at the top of the three-phase separator 70 is connected to the carbon dioxide pipeline at the output end of the low-temperature precooling water tank 37, and before the second centrifugal compressor 41, an insulation layer is laid outside the reinjection pipeline; the liquid phase output end at the top of the three-phase separator 70 is connected to the seawater outlet pipeline at the output end of the bottom of the low-temperature precooling water tank 37, and before the booster pump 48, an insulation layer is laid outside the reinjection pipeline; the solid phase output end at the bottom of the three-phase separator 70 is connected to the hydrate pipeline transportation system, and an insulation layer is laid outside the reinjection pipeline.

[0068] In this embodiment, carbon dioxide and seawater enter the first high-pressure reactor 63 and the second high-pressure reactor 67, and the pressure inside is maintained at 5 MPa. At the same time, the second gasifier 62 provides cold energy, and the temperature of the first high-pressure reactor 63 and the second high-pressure reactor 67 is controlled at 0.5-1.5° C., and the inside has a large degree of supercooling. The first stirrer 64 in the first high-pressure reactor 63 and the second stirrer 68 in the second high-pressure reactor 67 are continuously stirred, the induction time is significantly shortened, and hydrates are quickly generated; the hydrates, unreacted carbon dioxide, and unreacted seawater generated in the first high-pressure reactor 63 and the second high-pressure reactor 67 pass through the three-phase separator 70, and the three-phase separator 70 has an insulation layer 73 on the outside to prevent the loss of internal cold; the three-phase separator 70 separates the unreacted carbon dioxide, unreacted seawater and hydrates, and the carbon dioxide is transported back to the front of the second centrifugal compressor 41, and the seawater is transported back to the front of the booster pump 48; the separated hydrates are transported to the hydrate pipeline transportation system.

[0069] In this embodiment, the first high-pressure reactor 63 is equipped with an eleventh pressure sensor 60 and an eleventh temperature sensor 61, and the second high-pressure reactor 67 is equipped with a twelfth pressure sensor 65 and a twelfth temperature sensor 66; the pressure sensor is used to monitor the pressure of the reactor and control the pressure at 5Mpa; the temperature sensor is used to monitor the temperature of the reactor, and by adjusting the valve opening of the sixth regulating valve 31 and the seventh regulating valve 32, the release of the cold energy of the second vaporizer 62 is controlled, and the temperature is controlled at 0.5-1.5°C, thereby improving the utilization efficiency of the cold energy.

[0070] In this embodiment, the data of all pressure sensors and temperature sensors are collected by a computer data acquisition device 34 for real-time monitoring of operating conditions.

[0071] In this embodiment, hydrates are prepared by two reactors and continuous stirring; a three-phase separator 70 is used to separate unreacted carbon dioxide, unreacted seawater and hydrates; carbon dioxide is dissolved in the unreacted seawater, and this part of the seawater will subsequently generate a part of hydrates. At the same time, in order to improve the storage efficiency of carbon dioxide, the carbon dioxide and seawater are transported through pipelines to re-enter the reactor for hydrate preparation, and the generated hydrates are separated through the solid phase output end at the bottom of the three-phase separator 70 and enter the hydrate pipeline transportation system. In the hydrate preparation process, the carbon dioxide pipeline and the seawater pipeline form a cycle; at the same time, the LNG gasification system and the cold energy continuous supply system are used to provide continuous cold energy, thereby ultimately achieving the effect of continuous hydrate preparation.

[0072] Embodiment 6:

[0073] The hydrate pipeline transportation system is used to transport carbon dioxide hydrate to the submarine reservoir; it includes a low-temperature precooling water tank 37, a three-phase separator 70, a slurry storage and distribution tank 76, a mixed transfer pump 81, and a hydrate slurry transportation pipeline 86; the solid phase output end at the bottom of the three-phase separator 70 is connected to the input end at the top of the slurry storage and distribution tank 76, the seawater output end at the bottom of the low-temperature precooling water tank 37 is connected to the input end at the bottom of the slurry storage and distribution tank 76, the output end at the bottom of the slurry storage and distribution tank 76 is connected to the input end of the mixed transfer pump 81, and the output end of the mixed transfer pump 81 is connected to the hydrate slurry transportation pipeline 86; the pipeline between the seawater outlet at the bottom of the low-temperature precooling water tank 37 and the inlet at the bottom of the slurry storage and distribution tank 76 and the pipelines before and after the mixed transfer pump 81 are all provided with an insulation layer.

[0074] In this embodiment, the seawater transported from the low-temperature pre-cooling water tank 37 and the hydrate separated by the three-phase separator 70 are mixed in a certain volume ratio in the slurry storage and distribution tank 76. After mixing, the hydrate slurry formed by the seawater and the hydrate is pressurized by the mixing pump 81 and then transported to the seabed reservoir via the hydrate slurry transport pipeline 86.

[0075] In this embodiment, the volume ratio of low-temperature seawater and hydrate in the slurry storage tank 76 is controlled, and the liquid-solid mixing ratio is determined according to the characteristics of the hydrate particles (size, shape, density), the characteristics of the seawater (viscosity, surface tension), the characteristics of the transportation pipeline (diameter, roughness, etc.) and the transportation pressure.

[0076] In the present embodiment, the hydrate slurry obtained by mixing hydrates and seawater is pressurized by the mixing pump 81 and transported to the seabed reservoir by the hydrate slurry transport pipeline 86 for hydrate sealing. At the same time, a thermal insulation layer is laid on the hydrate slurry transport pipeline 86 to prevent the loss of cold. When the temperature at a certain location on the seabed is detected to be 1°C, the hydrate slurry transport pipeline 86 is laid with an insulation layer above the location, and no insulation layer is laid below the location.

[0077] In this embodiment, an eighteenth regulating valve 75 and a nineteenth regulating valve 78 are arranged before and after the slurry storage and distribution tank 76, which are used to adjust the volume ratio of the hydrate and seawater mixture; a sixth one-way stop valve 84 is arranged after the mixed pump 81 to ensure the stable operation of the mixed pump 81; a thirteenth pressure sensor 79 and a thirteenth temperature sensor 80 are arranged before the mixed pump 81, and a fourteenth pressure sensor 82, a fourteenth temperature sensor 83 and an eighth flow meter 85 are arranged after the mixed pump 81; the pressure sensor is used to monitor the hydrate slurry pressure, the temperature sensor is used to monitor the hydrate slurry temperature, and the flow meter is used to measure the hydrate slurry flow.

[0078] In this embodiment, the data of all pressure sensors, temperature sensors, and flow meters are collected by a computer data acquisition device 34 for real-time monitoring of operating conditions.

[0079] In this embodiment, the volume ratio of hydrate and seawater is determined in the slurry storage and preparation tank 76, and the hydrate and seawater are fully mixed by the third agitator 77 in the slurry storage and preparation tank 76. The hydrate slurry formed by the seawater and hydrate after the ratio enters the mixing pump 81 for pressurization, and the hydrate slurry is transported through the hydrate slurry transportation pipeline 86, thereby improving the efficiency of the hydrate slurry pipeline transportation; by laying an insulation layer to keep the pipeline cold, the problem of hydrate decomposition causing carbon dioxide to escape can be prevented, thereby improving the efficiency of carbon dioxide storage.

[0080] The above contents are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A carbon dioxide hydrate generation and marine storage system using LNG cold energy, characterized in that: Including LNG gasification system, cold energy continuous supply system, pre-cooling system, pressurization system, hydrate generation system, hydrate pipeline transportation system; The LNG gasification system is characterized by comprising an LNG storage tank 1, an LNG pump 4, a condenser 22, and a gasification processing device 11; the output end of the LNG storage tank 1 is connected to the input end of the LNG pump 4, the output end of the LNG pump 4 is connected to the input end of the condenser 22, the output end of the condenser 22 is connected to the input end of the gasification processing device 11, and the output end of the gasification processing device 11 is connected to a downstream user; The cold energy continuous supply system is characterized in that it includes a liquid ammonia storage tank 12, a liquid ammonia pump 16, a first vaporizer 36, a second vaporizer 62, an ammonia storage tank 33, a condenser 22, and a first centrifugal compressor 27; the output end of the liquid ammonia storage tank 12 is connected to the input end of the liquid ammonia pump 16, the output end of the liquid ammonia pump 16 is connected to the input end of the first vaporizer 36, the output end of the first vaporizer 36 is connected to the input end of the second vaporizer 62, the output end of the second vaporizer 62 is connected to the input end of the ammonia storage tank 33, the output end of the ammonia storage tank 33 is connected to the input end of the first centrifugal compressor 27, the output end of the first centrifugal compressor 27 is connected to the input end of the condenser 22, and the output end of the condenser 22 is connected to the input end of the liquid ammonia storage tank 12, so as to form a complete circulation pipeline; The precooling system is characterized by comprising a low-temperature precooling water tank 37 and a first vaporizer 36; a carbon dioxide pipeline is connected to the low-temperature precooling water tank 37, and a seawater pipeline is connected to inject seawater into the low-temperature precooling water tank 37; the seawater in the low-temperature precooling water tank 37 has two output ends, namely a bottom seawater output end and a bottom seawater output end, the bottom seawater output end is connected to the pressurization system, and the bottom seawater output end is connected to the hydrate pipeline transportation system; The pressurizing system is characterized in that it includes a pressurizing pump 48, a second centrifugal compressor 41, a low-temperature precooling water tank 37, a first high-pressure reactor 63, and a second high-pressure reactor 67; the seawater output end at the bottom of the low-temperature precooling water tank 37 is connected to the input end of the pressurizing pump 48, and the pressurizing pump 48 has two output ends, the first output end of the pressurizing pump 48 is connected to the liquid phase input end of the first high-pressure reactor 63, and the second output end of the pressurizing pump 48 is connected to the liquid phase input end of the second high-pressure reactor 67; the carbon dioxide pipeline is connected to the input end of the second centrifugal compressor 41 after passing through the low-temperature precooling water tank 37, and the second centrifugal compressor 41 has two output ends, the first output end of the second centrifugal compressor 41 is connected to the gas phase input end of the first high-pressure reactor 63, and the second output end of the second centrifugal compressor 41 is connected to the gas phase input end of the second high-pressure reactor 67; The hydrate generation system is characterized by comprising a low-temperature precooling water tank 37, a booster pump 48, a second centrifugal compressor 41, a first high-pressure reactor 63, a second high-pressure reactor 67, a first agitator 64, a second agitator 68, a second gasifier 62, and a three-phase separator 70; the gas phase input end of the first high-pressure reactor 63 is the carbon dioxide output by the second centrifugal compressor 41, and the liquid phase input end is the seawater output by the booster pump 48; the gas phase input end of the second high-pressure reactor 67 is the carbon dioxide output by the second centrifugal compressor 41, and the liquid phase input end is the seawater output by the booster pump 48; the first high-pressure reactor 63 has a first agitator 64, and the second high-pressure reactor 67 has a second gasifier 62 and a three-phase separator 70; Two stirrers 68; the output ends of the first high-pressure reactor 63 and the second high-pressure reactor 67 are connected to the input end of the top of the three-phase separator 70, and the three-phase separator 70 is provided with an insulation layer 73; the gas phase output end at the top of the three-phase separator 70 is connected to the carbon dioxide pipeline at the output end of the low-temperature precooling water tank 37, and before the second centrifugal compressor 41, the pipeline is provided with an insulation layer; the liquid phase output end at the top of the three-phase separator 70 is connected to the seawater outlet pipeline at the output end of the bottom of the low-temperature precooling water tank 37, and before the booster pump 48, the pipeline is provided with an insulation layer; the solid phase output end at the bottom of the three-phase separator 70 is connected to the hydrate pipeline transportation system, and the pipeline is provided with an insulation layer; The hydrate pipeline transportation system is characterized by comprising a low-temperature precooling water tank 37, a three-phase separator 70, a slurry storage and distribution tank 76, a mixed flow pump 81, and a hydrate slurry transportation pipeline 86; the solid phase output end at the bottom of the three-phase separator 70 is connected to the input end at the top of the slurry storage and distribution tank 76, the seawater output end at the bottom of the low-temperature precooling water tank 37 is connected to the input end at the bottom of the slurry storage and distribution tank 76, the output end of the slurry storage and distribution tank 76 is connected to the input end of the mixed flow pump 81, and the output end of the mixed flow pump 81 is connected to the hydrate slurry transportation pipeline 86; the pipeline between the seawater outlet at the bottom of the low-temperature precooling water tank 37 and the inlet at the bottom of the slurry storage and distribution tank 76 and the pipelines connected before and after the mixed flow pump 81 are all laid with a thermal insulation layer, and the hydrate slurry transportation pipeline 86 is laid with a thermal insulation layer above the position where the seabed temperature is 1°C, and is not laid with a thermal insulation layer below the position of 1°C.

2. A method for generating carbon dioxide hydrate using LNG cold energy and storing it in the ocean, characterized in that: The method is implemented by using a carbon dioxide hydrate generation and marine storage system using LNG cold energy as described in claim 1, comprising the following steps: S1: LNG releases cold energy through the condenser 22, and then passes through the gasification processing equipment 11 to become natural gas and is transported to downstream users; S2: The liquid ammonia in the liquid ammonia storage tank 12 is gasified into ammonia gas through the first gasifier 36 and the second gasifier 62 and releases cold energy, which is used for carbon dioxide and seawater; the ammonia gas is stored in the ammonia storage tank 33, and the ammonia gas in the ammonia storage tank 33 is pressurized by the first centrifugal compressor 27, and then absorbed by the condenser 22. LNG cold energy is condensed into liquid ammonia and stored in the liquid ammonia storage tank 12; S3: Connect the carbon dioxide pipeline to the low-temperature precooling water tank 37, and the seawater is transported to the low-temperature precooling water tank 37 through the pipeline. The first vaporizer 36 provides the cooling capacity required by the low-temperature precooling water tank 37. Connect the carbon dioxide pipeline to the low-temperature precooling water tank 37 for precooling. The seawater is precooled in the low-temperature precooling water tank 37. The internal temperature of the low-temperature precooling water tank 37 is controlled at 4-6°C, and 90% of the volume capacity of the seawater in the low-temperature precooling water tank 37 is maintained. After precooling, it is transported to the pressurization system; S4: the pressure pump 48 pressurizes and delivers the seawater from the low-temperature pre-cooling water tank 37, and the second centrifugal compressor 41 pressurizes and delivers the carbon dioxide that has passed through the low-temperature pre-cooling water tank 37, and delivers the carbon dioxide and seawater to the hydrate generation system; S5: Carbon dioxide and seawater enter the first high-pressure reactor 63 and the second high-pressure reactor 67, and the internal pressure of the two reactors is maintained at 5 MPa. The second gasifier 62 provides the cooling capacity required by the two reactors, and the temperature of the first high-pressure reactor 63 and the second high-pressure reactor 67 is controlled at 0.5-1.5°C. The first stirrer 64 and the second stirrer 68 are used for continuous stirring. The carbon dioxide hydrate, unreacted carbon dioxide and unreacted seawater at the output ends of the first high-pressure reactor 63 and the second high-pressure reactor 67 enter the three-phase separator 70 for separation. The unreacted carbon dioxide and unreacted seawater are re-injected into the two reactors through the pipeline, and the generated carbon dioxide hydrate is transported to the hydrate pipeline transportation system; S6: The slurry storage and distribution tank 76 receives the seawater from the low-temperature pre-cooling water tank 37 and the carbon dioxide hydrate from the solid phase output end at the bottom of the three-phase separator 70. The hydrate slurry formed after mixing is pressurized by the mixing pump 81 and transported to the seabed reservoir via the hydrate slurry transportation pipeline 86.

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