Liquid cargo system of low-pressure storage and transportation liquid carbon dioxide ship and transfer method

Abstract

The invention relates to a liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship and a transfer method. The liquid cargo system comprises a low-pressure storage tank, a conveying pump, an external conveying system, a self-evaporation pressure maintaining system, an injection system, a volatile gas conveying and processing system, a liquid-phase collecting pipe, a high-pressure collecting pipe, a gas-phase collecting pipe, a gas collecting pipe, a liquid cabin inlet pipe and a liquid cabin outlet pipe. Wherein the output system is used for conveying liquid carbon dioxide to storage shore stations with different storage pressures; the self-evaporation pressure maintaining system is used for controlling the pressure in the low-pressure storage tank; the injection system is used for injecting liquid carbon dioxide of the storage shore station into the low-pressure storage tank; the volatile gas conveying and processing system is used for conveying and processing volatile gas in the process of outwards conveying or injecting carbon dioxide. Through the multi-process design, the self-evaporation pressure maintaining system and the excessive gaseous carbon dioxide liquefaction back-to-cabin process, low-pressure storage and transportation are effectively compatible with medium and high-pressure storage shore stations, and the compatibility of the ship and the operation flexibility of the ship are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ship engineering equipment, and in particular relates to a liquid cargo system and a transfer method of a low-pressure liquid carbon dioxide storage and transportation ship. Background Art

[0002] As climate and environmental issues become increasingly prominent worldwide, countries are gradually increasing their efforts and measures to address global warming, and various plans to reduce carbon dioxide emissions have emerged. Among them, carbon dioxide capture and storage is an important and effective measure. How to transport the captured carbon dioxide to the storage site is an important part of determining the success or failure of carbon capture and storage projects.

[0003] The volume of liquefied carbon dioxide is about 1 / 600 of the volume of the same amount of gaseous carbon dioxide. Therefore, using ships to transport liquid carbon dioxide is the most efficient and economical way to transport captured carbon dioxide over long distances. According to research data from the Global CCS Institute, the carbon capture and storage market is expected to grow at a rate of more than 30% per year, and the global carbon capture volume will reach 7.6 billion tons by 2050, which also means that the demand for liquid carbon dioxide transportation will increase accordingly.

[0004] Low-pressure storage technology is one of the main technical development directions for future liquid carbon dioxide transport ships, that is, liquid carbon dioxide is stored in cargo holds at a temperature of -50°C and a pressure of 8 barg for transportation. Due to the special physical properties of the triple point of carbon dioxide, the currently designed low-pressure liquid carbon dioxide transport ships can only load and unload cargo between storage shore stations or ships with the same or similar design pressure, and are not compatible with storage shore stations with medium or high pressure storage. Summary of the invention

[0005] In order to solve the problem that the current low-pressure storage and transportation ships for liquid carbon dioxide are not compatible with medium-pressure storage shore stations or high-pressure storage shore stations, the present invention provides a liquid cargo system and a transfer method for a low-pressure storage and transportation ship for liquid carbon dioxide. Through a multi-process design, as well as the provision of a self-evaporation pressure maintenance system and a process for liquefying excess gaseous carbon dioxide back to the tank, low-pressure storage and transportation can be effectively compatible with medium-pressure storage shore stations or high-pressure storage shore stations, thereby improving the compatibility of ships and the flexibility of ship operations.

[0006] In order to achieve the above invention purpose, the technical solution provided by the present invention is as follows:

[0007] A liquid cargo system for a low-pressure storage and transportation ship of liquid carbon dioxide, the system comprising: a low-pressure storage tank, a delivery pump, an external delivery system, a self-evaporation pressure-maintaining system, an injection system, a volatile gas delivery and treatment system, a liquid phase header, a high-pressure header, a gas phase header, a gas header, a liquid inlet pipe and a liquid outlet pipe; wherein:

[0008] Low-pressure storage tanks are used to store liquid carbon dioxide at low pressure;

[0009] The delivery pump is connected to the liquid outflow pipe and is used to deliver the liquid carbon dioxide in the low-pressure storage tank to the outside;

[0010] The external transmission system includes at least one of a low-pressure external transmission system, a medium-pressure external transmission system and a high-pressure external transmission system, and its input end is connected to the liquid outflow pipe, and is used to transport liquid carbon dioxide to storage shore stations with different storage pressures (including low-pressure storage shore stations, medium-pressure storage shore stations and high-pressure storage shore stations);

[0011] The input end of the self-evaporation pressure-maintaining system is connected to the liquid outflow pipe, and the output end is connected to the gas collecting pipe, so as to control the pressure in the low-pressure storage tank when the liquid carbon dioxide is transported out;

[0012] The input end of the injection system is connected to the liquid phase header, and the output end is connected to the liquid inlet pipe, so as to inject the liquid carbon dioxide in the storage shore station into the low-pressure storage tank; the injection system includes at least one of a low-pressure injection system and a medium / high-pressure injection system;

[0013] The volatile gas delivery and treatment system, whose output ends are respectively connected to the liquid inlet pipe and the gas collecting pipe, is used to deliver and treat the volatile gas and balance the system pressure during the process of transporting or injecting carbon dioxide;

[0014] The liquid phase header is connected to a storage shore station for receiving or outputting liquid carbon dioxide;

[0015] The gas phase header is used to receive or output gaseous carbon dioxide;

[0016] The storage shore station includes at least one of a low-pressure storage shore station, a medium-pressure storage shore station and a high-pressure storage shore station.

[0017] As an optional implementation, the low-pressure external transmission system, the medium-pressure external transmission system and the high-pressure external transmission system are arranged in parallel, and the output ends of the low-pressure external transmission system and the medium-pressure external transmission system are respectively connected to the liquid phase header; the output end of the high-pressure external transmission system is connected to the high-pressure header.

[0018] As an optional embodiment, the medium / high pressure injection system and the low pressure injection system are installed in parallel in the injection system.

[0019] In the present invention, the low-pressure injection system and the medium / high-pressure injection system inject liquid carbon dioxide into the low-pressure storage tank, and are all connected to the liquid phase header. The high-pressure header is only used to transport liquid carbon dioxide from the low-pressure storage tank on board to the high-pressure storage shore station.

[0020] As an optional embodiment, the liquid phase manifold is connected to a storage shore station (e.g., a low pressure storage shore station, a medium pressure storage shore station, or a high pressure storage shore station) via a connecting loading / unloading facility (e.g., a liquid phase interface of a loading and unloading arm or a loading and unloading hose).

[0021] As an optional embodiment, the gas phase manifold is connected to a gas transportation facility, such as a loading and unloading arm or a loading and unloading hose gas phase interface, and is connected to a storage shore station (for example, a low-pressure storage shore station, a medium-pressure storage shore station, and a high-pressure storage shore station) through the gas transportation facility.

[0022] As an optional embodiment, the input end of the liquid inlet pipe is connected to the injection system (for example, respectively connected to the medium / high pressure injection system and the low pressure injection system), and the opening of the output end is arranged in the low pressure storage tank.

[0023] As an optional implementation, the input end of the liquid inlet pipe is also connected to the liquefied return pipe of the volatile gas transportation and treatment system.

[0024] As an optional implementation, the opening for communicating the gas collecting pipe with the low-pressure storage tank is arranged at the top of the low-pressure storage tank.

[0025] As an optional implementation, the output end of the volatile gas delivery and treatment system is connected to the liquid inlet pipe and the gas collecting pipe respectively.

[0026] As an optional embodiment, the low-pressure storage tank adopts a C-type storage tank (defined by IMO). The material of the low-pressure storage tank meets the pressure and temperature requirements for low-pressure storage of liquid carbon dioxide, and is coated with insulation material. Optionally, the insulation material has a low thermal conductivity, including polyurethane or polystyrene. Optionally, the insulation material is installed on the outside of the storage tank using a prefabricated insulation module or on-site spray foaming method.

[0027] As an optional implementation, in the liquid cargo system, there may be multiple low-pressure storage tanks.

[0028] As an optional implementation, the delivery pump is installed inside the low-pressure storage tank, and its outlet is connected to the liquid outflow pipe; optionally, the delivery pump includes a deep well pump or a submersible pump.

[0029] In the present invention, one end of the liquid outflow pipe is connected to the outlet of the delivery pump, and the other end is connected to a plurality of external delivery system pipes and self-evaporation pressure-maintaining pipes arranged in parallel.

[0030] As an optional embodiment, the low-pressure external transmission system includes a second isolation valve, a low-pressure pressure regulating unit, a low-pressure temperature control unit and a second one-way valve; the second isolation valve is arranged on the low-pressure external transmission pipeline of the low-pressure external transmission system, and is used to control the opening and closing of the low-pressure external transmission pipeline; the low-pressure pressure regulating unit is used to control the pressure of the externally transmitted liquid carbon dioxide in the low-pressure external transmission system; the low-pressure temperature control unit is used to control the temperature of the externally transmitted liquid carbon dioxide in the low-pressure external transmission system, and the second one-way valve serves to prevent liquid reflux.

[0031] Furthermore, the outlet of the low-pressure external transmission system (through the second one-way valve) is connected to the liquid phase manifold.

[0032] Optionally, the low-pressure pressure regulating unit includes a pressure regulating valve, a controller and a second pressure sensor, wherein the second pressure sensor is installed downstream of the pressure regulating valve, and is used to monitor the pressure of the fluid (i.e., liquid carbon dioxide) in the low-pressure external transmission pipeline, and transmit the measured value to the controller; the controller receives the pressure setting value and compares it with the actual measured pressure value, and then controls the pressure regulating valve so that the pressure of the fluid flowing through the pressure regulating valve tends to the pressure setting value.

[0033] Optionally, the low-pressure temperature control unit includes a low-pressure heat exchanger, a heat exchange medium source, a temperature control three-way valve and a low-pressure temperature sensor. The temperature control three-way valve has a linear adjustment capability and is connected to the system through three interfaces "a", "b" and "c"; the low-pressure temperature sensor is used to monitor the temperature of the liquid carbon dioxide, and controls the flow of the liquid carbon dioxide flowing through the low-pressure heat exchanger by adjusting the opening of the temperature control three-way valve, that is, the flow ratio of "ab" and "cb", thereby controlling the temperature of the mixed liquid carbon dioxide to meet the design requirements; the low-pressure heat exchanger (or low-pressure heat exchanger) includes a plate heat exchanger or a shell and tube heat exchanger; the heat exchange medium source controls the temperature of the heat exchange medium through a secondary heat exchange cycle, and provides the low-pressure heat exchanger (i.e., low-pressure heat exchanger) with pre-cooled heat exchange medium; the heat exchange medium can be ethylene glycol water or other low-freezing point liquids.

[0034] Specifically, in the low-pressure temperature control unit, the pressure-regulated liquid carbon dioxide enters the low-pressure temperature control unit for diversion, a portion of the liquid carbon dioxide is connected to the temperature control three-way valve interface "a" through the low-pressure heat exchanger, and a portion of the liquid carbon dioxide is connected to the temperature control three-way valve interface "c" through the pipeline.

[0035] As an optional embodiment, the medium-pressure external transmission system includes a first isolation valve, a medium-pressure booster pump, a medium-pressure heating device and a first one-way valve; wherein the first isolation valve is arranged on the medium-pressure external transmission pipe of the medium-pressure external transmission system to control the opening and closing of the medium-pressure external transmission pipe; the medium-pressure booster pump is used to pressurize the liquid carbon dioxide from the delivery pump to increase the pressure of the liquid carbon dioxide to meet the pressure requirement of the medium-pressure storage shore station; optionally, the medium-pressure booster pump includes a centrifugal pump or a volumetric pump; the medium-pressure heating device is used to increase the temperature of the pressurized liquid carbon dioxide to meet the temperature requirement of the medium-pressure storage shore station; the outlet of the first one-way valve is connected to the liquid phase manifold to prevent the backflow of liquid (i.e., liquid carbon dioxide).

[0036] Optionally, the outlet of the medium-pressure export system is connected to the liquid phase header for exporting the medium-pressure liquid carbon dioxide to a medium-pressure storage shore station.

[0037] Furthermore, the medium-pressure heating device includes a medium-pressure heater, a first temperature control valve and a medium-pressure temperature sensor; wherein the medium-pressure temperature sensor is used to monitor the temperature of the pressurized liquid carbon dioxide and control the opening of the first temperature control valve; the first temperature control valve is used to adjust the amount of heat exchange medium entering the medium-pressure heater, thereby controlling the temperature of the liquid carbon dioxide passing through the medium-pressure heat exchanger.

[0038] Optionally, the first temperature control valve includes a pneumatic temperature control valve, an electric temperature control valve or a hydraulically driven temperature control valve, and the opening degree of the first temperature control valve is controlled by the medium-pressure temperature sensor.

[0039] Optionally, the medium pressure heater comprises a plate heater or a shell and tube heater.

[0040] Optionally, the heat exchange medium includes any one of sea water, fresh water, steam, hot oil and ethylene glycol water.

[0041] As an optional embodiment, the high-pressure export system includes a third isolation valve, a high-pressure booster pump and a high-pressure heating device; wherein the third isolation valve is arranged on the high-pressure export pipe of the high-pressure export system to control the opening and closing of the high-pressure export pipe; the high-pressure booster pump is used to increase the pressure of the liquid carbon dioxide from the delivery pump to meet the requirements of the high-pressure storage shore station for reception; optionally, the high-pressure booster pump includes a centrifugal pump or a volumetric pump; the high-pressure heating device is used to increase the temperature of the pressurized liquid carbon dioxide to meet the temperature requirements of the high-pressure storage shore station, and its outlet is connected to the high-pressure header.

[0042] In the present invention, the high-pressure header is used to transport the liquid carbon dioxide in the low-pressure storage tank on the liquid carbon dioxide ship to the high-pressure storage shore station.

[0043] Furthermore, the high-pressure temperature-raising device includes a high-pressure heater, a second temperature control valve, and a high-pressure temperature sensor; wherein, the high-pressure temperature sensor is installed at the outlet of the high-pressure heater for monitoring the temperature of the pressurized liquid carbon dioxide and controlling the opening degree of the second temperature control valve; the second temperature control valve is used for adjusting the amount of the heat exchange medium entering the high-pressure heater, thereby controlling the temperature of the liquid carbon dioxide passing through the high-pressure heat exchanger.

[0044] Optionally, the second temperature control valve includes a pneumatic temperature control valve, an electric temperature control valve, or a hydraulic-driven temperature control valve.

[0045] Optionally, the opening degree of the second temperature control valve is controlled by the high-pressure temperature sensor.

[0046] Optionally, the high-pressure heater includes a plate-type high-pressure heater or a shell-and-tube high-pressure heater.

[0047] Optionally, the heat exchange medium includes at least one of electric energy, steam, hot oil, and ethylene glycol water.

[0048] As an alternative embodiment, the self-evaporation pressure-holding system includes a pressure control valve, an evaporation gasifier, and a first pressure sensor; wherein, the opening and closing of the pressure control valve are controlled by the first pressure sensor, and the first pressure sensor is installed at the top of the low-pressure storage tank for monitoring the pressure in the gas phase space at the top of the low-pressure storage tank; the evaporation gasifier is used for evaporating the liquid carbon dioxide into gaseous carbon dioxide and returning it to the low-pressure storage tank through a gas collecting pipe.

[0049] Optionally, the evaporation gasifier includes one of a plate-type evaporation gasifier and a shell-and-tube evaporation gasifier, and its heat source includes electric energy, steam, or hot oil.

[0050] Optionally, the pressure control valve includes a pneumatic pressure control valve, an electric pressure control valve, or a hydraulic-driven pressure control valve.

[0051] As an alternative embodiment, the input ends of the medium / high-pressure injection system and the low-pressure injection system are connected to the liquid phase header through a first remote control three-way valve, and the output ends are connected to the liquid inlet pipe for injecting liquid carbon dioxide in storage shore stations with different storage pressures into the low-pressure storage tank; wherein, the first remote control three-way valve has three interfaces, namely "1", "2", and "3", wherein interface "1" is connected to the liquid phase header; interface "2" is connected to the low-pressure injection system; and interface "3" is connected to the medium / high-pressure injection system.

[0052] The present invention selects different injection systems according to the pressure of the liquid carbon dioxide input from the storage shore station. Among them, the input end to which both the medium-pressure injection system and the high-pressure injection system can be connected is connected to the interface "3" of the first remote control three-way valve, and is transported to the low-pressure storage tank after pressure reduction and temperature reduction. Therefore, the medium-pressure injection system and the high-pressure injection are combined, which is abbreviated as the medium / high-pressure injection system. For example, when the medium-pressure injection system is selected, the medium-pressure carbon dioxide injected is depressurized from about 15 bar to slightly higher than the pressure of the low-pressure storage tank, and the temperature is reduced from -33°C to -53°C; when the high-pressure injection system is selected, the high-pressure carbon dioxide injected is depressurized from about 45 bar to slightly higher than the pressure of the low-pressure storage tank, and the temperature is reduced from room temperature to -53°C.

[0053] As an optional embodiment, the low-pressure injection system includes a first pressure regulating valve; the input end of the first pressure regulating valve is connected to the interface "2" of the first remote control three-way valve, and the output end is connected to the liquid inlet pipe, which is used to control the pressure of the liquid carbon dioxide injected into the low-pressure injection system within a set range; optionally, the first pressure regulating valve includes a diaphragm pressure regulating valve, a spring piston pressure regulating valve or a bellows pressure regulating valve.

[0054] As an optional embodiment, the medium / high pressure injection system includes a pressure reducing valve, a cooling heat exchanger and a refrigeration unit; the input end of the medium / high pressure injection system is connected to the interface "3" of the first remote control three-way valve, and the output end is connected to the liquid inlet pipe; the pressure reducing valve is used to reduce the pressure of liquid carbon dioxide injected into the medium-pressure or high-pressure injection system.

[0055] Optionally, the pressure reducing valve comprises a spring type or a piston type.

[0056] Optionally, the desuperheating heat exchanger includes a plate type desuperheating heat exchanger, a shell and tube type desuperheating heat exchanger or a printed circuit board type desuperheating heat exchanger.

[0057] In the medium / high pressure injection system, the liquid carbon dioxide passes through a temperature reducing heat exchanger to exchange heat with a refrigerant from a refrigeration unit, thereby further cooling the decompressed liquid carbon dioxide so that its temperature meets the storage requirements of a low-pressure storage tank; the refrigeration unit is used to provide a refrigerant for the temperature reducing heat exchanger, and optionally, the refrigerant includes propane or propylene.

[0058] As an optional embodiment, the volatile gas transportation and treatment system includes a second remote control three-way valve, a gas compressor, a liquefaction device, a second pressure regulating valve, and a liquefied return pipe and a gas return pipe; wherein, the second remote control three-way valve is used to control the flow direction of the volatile gas, and has three interfaces "x", "y" and "z", wherein the interface "x" is connected to the gas phase manifold; the interface "y" is respectively connected to the liquefied return pipe and the gas return pipe; and the interface "z" is connected to the outlet of the gas compressor.

[0059] In the present invention, the connection mode in the second remote-controlled three-way valve is selected according to the transfer operation requirements.

[0060] Furthermore, the air inlet side of the gas compressor is connected to the gas collecting pipe through the fifth isolation valve, and the outlet is connected to the interface "z" of the second remote control three-way valve; the volatile gas compressed by the gas compressor can be returned to the receiving device of the storage shore station through the second remote control three-way valve "z"→"x" through the gas phase collecting pipe, or connected to the liquefaction return tank pipe through the second remote control three-way valve "z"→"y", and returned to the low-pressure storage tank after being liquefied by the liquefaction device;

[0061] Optionally, the gas compressor includes a screw-type gas compressor or a piston-type gas compressor.

[0062] Optionally, the inlet and outlet of the gas compressor are also provided with a bypass pipe and a seventh isolation valve for bypassing the gas compressor to achieve natural flow of gaseous carbon dioxide.

[0063] Furthermore, a sixth isolation valve is provided on the liquefied return tank pipe; a liquefaction device is installed downstream of the sixth isolation valve; the liquefaction device includes a liquefaction heat exchanger and a refrigeration unit; wherein the liquefaction heat exchanger is used to cool and liquefy the compressed gaseous carbon dioxide; and the refrigeration unit is used to provide refrigerant for the liquefaction heat exchanger.

[0064] Optionally, the liquefaction heat exchanger includes a plate-type liquefaction heat exchanger, a shell and tube-type liquefaction heat exchanger, or a printed circuit board-type liquefaction heat exchanger.

[0065] Optionally, the refrigerant includes propane or propylene.

[0066] In the present invention, in the volatile gas transportation and treatment system, the volatile gas compressed by the gas compressor is connected to the liquefaction return tank pipe through the second remote control three-way valve "z"→"y". In the liquefaction device, the compressed gaseous carbon dioxide is cooled and liquefied by the liquefaction heat exchanger, and the liquefied carbon dioxide returns to the low-pressure storage tank through the liquid inlet tank pipe.

[0067] Furthermore, the gas return pipe is provided with an eighth isolation valve and a second pressure regulating valve, wherein the second pressure regulating valve regulates the pressure of the gaseous carbon dioxide from the storage shore station so that the pressure meets the requirement of returning to the low-pressure storage tank.

[0068] Optionally, the second pressure regulating valve includes a diaphragm pressure regulating valve, a spring piston pressure regulating valve or a bellows pressure regulating valve.

[0069] In a second aspect, the present invention further provides a method for transferring a low-pressure liquid carbon dioxide storage and transportation ship, using the liquid cargo system of the low-pressure liquid carbon dioxide storage and transportation ship to transfer, and the transfer method comprises the following steps:

[0070] (1) The process of transferring liquid carbon dioxide to a storage station includes the following steps:

[0071] (11) Connect the liquid phase header / high-pressure header (i.e., liquid phase header or high-pressure header) and the gas phase header to the unloading facilities and gas transmission facilities of the storage shore station, respectively, select an external transmission system that matches the storage pressure of the storage shore station, and connect the external transmission system to the liquid outflow pipe;

[0072] (12) The liquid carbon dioxide in the low-pressure storage tank is output through a delivery pump and transported to a storage shore station through an external transmission system;

[0073] (2) Injecting liquid carbon dioxide into a low-pressure storage tank from a storage shore station includes the following steps:

[0074] (21) connecting the liquid phase header and the gas phase header to the loading facilities and gas delivery facilities of the storage shore station respectively, and selecting the flow path of the remote control three-way valve according to the storage pressure of the storage shore station;

[0075] (22) allowing liquid carbon dioxide from the storage shore station to flow through the liquid phase header and the remote control three-way valve in sequence into the injection system, adjusting the pressure and temperature of the carbon dioxide injected into the system, and then injecting it into the low-pressure storage tank;

[0076] (3) The volatile gas transport and treatment includes at least one of the following steps:

[0077] (31) In the process of transporting liquid carbon dioxide from a low-pressure storage tank to a storage shore station, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the gas collecting pipe is connected to the gas phase space of the storage shore station through the gas collecting pipe, and the gaseous carbon dioxide in the storage shore station is transported to the low-pressure storage tank through the gas collecting pipe under the action of the pressure difference, that is, gas return; the pressure difference is formed by the pressure difference between the storage tank of the storage shore station and the low-pressure storage tank, or by using the compressor of the storage shore station to pressurize the returned gaseous carbon dioxide (hereinafter referred to as: return gas);

[0078] (32) In the process of injecting liquid carbon dioxide from the storage shore station into the low-pressure storage tank, in order to avoid the pressure of the low-pressure storage tank being higher than the design pressure of the low-pressure storage tank, it is necessary to return a portion of the excess gaseous carbon dioxide in the low-pressure storage tank to the shore station through the gas phase header; specifically, the gaseous carbon dioxide in the low-pressure storage tank is returned to the storage shore station through the gas phase header under the action of the pressure difference, that is, the gas returns to the shore; the pressure difference is formed by the pressure difference between the low-pressure storage tank and the storage tank of the storage shore station, or by using the gas compressor on the ship to pressurize the gaseous carbon dioxide (referred to as: return shore gas) delivered to the storage shore station;

[0079] (33) In step (32), if the storage shore station does not receive the returned gaseous carbon dioxide, the excess gaseous carbon dioxide in the low-pressure storage tank is extracted and pressurized by a gas compressor, and the gaseous carbon dioxide pressurized by the gas compressor enters a liquefaction device to be converted into liquid carbon dioxide, and then injected into the low-pressure storage tank;

[0080] (34) During the process of transferring liquid carbon dioxide from the low-pressure storage tank to the storage shore station, if the pressure of the low-pressure storage tank increases, in order to prevent the pressure of the low-pressure storage tank from being higher than the design pressure of the low-pressure storage tank, the operation of step (32) is adopted; that is, the gaseous carbon dioxide in the low-pressure storage tank is returned to the storage shore station through the gas phase header under the action of the pressure difference;

[0081] (35) During the process of injecting liquid carbon dioxide from the storage shore station into the low-pressure storage tank, if the pressure of the low-pressure storage tank drops, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the operation of step (31) is adopted; that is, the gas collecting pipe is connected to the gas phase space of the storage shore station through the gas phase collecting pipe, and the gaseous carbon dioxide from the storage shore station is transported to the low-pressure storage tank through the gas collecting pipe under the action of the pressure difference, that is, gas return;

[0082] (4) Self-evaporation pressure-maintaining treatment, comprising the following steps:

[0083] When the pressure of the gas phase space in the low-pressure storage tank drops to the low-pressure setting value, the pressure control valve is opened to connect the self-evaporation pressure maintaining system with the liquid outflow pipe, and part of the externally transported liquid carbon dioxide enters the self-evaporation pressure maintaining pipe, is gasified by the evaporator gasifier, and is returned to the low-pressure storage tank through the gas collecting pipe; when the pressure of the gas phase space in the low-pressure storage tank rises to the high-pressure setting value, the pressure control valve is closed, and the self-evaporation pressure maintaining process ends.

[0084] In the present invention, in the step (3), the pressure of the low-pressure storage tank is prevented from being lower than the triple point pressure of carbon dioxide or exceeding the maximum working pressure (pressure setting value) designed for the low-pressure storage tank, which should be considered when transporting carbon dioxide and injecting carbon dioxide. When transporting carbon dioxide, the pressure drop of the low-pressure storage tank is a frequent phenomenon, while the pressure increase is an occasional phenomenon; when injecting carbon dioxide, the pressure increase of the low-pressure storage tank is a frequent phenomenon, while the pressure drop is an occasional phenomenon.

[0085] As an optional implementation, in step (1), the liquid carbon dioxide is transported to the low-pressure storage shore station, comprising the following steps:

[0086] (11) Connecting the liquid phase header and the gas phase header to the unloading facilities and gas transmission facilities of the low-pressure storage shore station respectively, closing the first isolation valve and the third isolation valve, disconnecting the medium-pressure external transmission system and the high-pressure external transmission system; opening the second isolation valve to connect the low-pressure external transmission system to the liquid outflow pipe;

[0087] (12) Start the delivery pump to output the liquid carbon dioxide in the low-pressure storage tank through the delivery pump and enter the low-pressure export pipe of the low-pressure export system through the liquid outlet pipe; then adjust the pressure and temperature of the liquid carbon dioxide through the low-pressure pressure regulating unit and the low-pressure temperature control unit of the low-pressure export system in turn; the pressure-regulated and temperature-controlled liquid carbon dioxide enters the liquid phase header through the second one-way valve, and finally the liquid carbon dioxide is delivered to the low-pressure storage shore station through the unloading facilities connected to the liquid phase header.

[0088] As an optional implementation, in step (1), the liquid carbon dioxide is transported to the medium-pressure storage shore station, comprising the following steps:

[0089] (11) Connect the liquid phase header and the gas phase header to the unloading facilities and gas transmission facilities of the medium-pressure storage shore station respectively, close the second isolation valve and the third isolation valve, disconnect the low-pressure external transmission system and the high-pressure external transmission system; open the first isolation valve to connect the medium-pressure external transmission system to the liquid outflow pipe;

[0090] (12) Start the transfer pump to discharge the liquid carbon dioxide in the low-pressure storage tank through the transfer pump and enter the medium-pressure external transmission pipe of the medium-pressure external transmission system through the liquid outlet pipe; then the liquid carbon dioxide is pressurized by the medium-pressure booster pump of the medium-pressure external transmission system, and the pressurized liquid carbon dioxide is then heated by the medium-pressure heating device, so that the pressure and temperature of the liquid carbon dioxide meet the receiving requirements of the medium-pressure storage shore station; then, the pressurized and heated liquid carbon dioxide enters the liquid phase header through the first one-way valve, and finally the liquid carbon dioxide is transported to the medium-pressure storage shore station through the unloading facilities connected to the liquid phase header.

[0091] As an optional embodiment, in step (1), the liquid carbon dioxide is transported to the high-pressure storage shore station, comprising the following steps:

[0092] (11) Connect the high-pressure header and the gas phase header to the unloading facilities and gas transmission facilities of the high-pressure storage shore station respectively, close the first isolation valve and the second isolation valve, disconnect the low-pressure external transmission system and the medium-pressure external transmission system; open the third isolation valve to connect the high-pressure external transmission system to the liquid outflow pipe;

[0093] (12) Start the delivery pump to output the liquid carbon dioxide in the low-pressure storage tank through the delivery pump and enter the high-pressure export pipe of the high-pressure export system through the liquid outlet pipe; then, the liquid carbon dioxide entering the high-pressure export pipe is pressurized by the high-pressure booster pump, and the pressurized liquid carbon dioxide is then heated by the high-pressure heating device, so that the pressure and temperature of the liquid carbon dioxide meet the receiving requirements of the high-pressure storage shore station; the pressurized and heated liquid carbon dioxide is transported to the high-pressure storage shore station through the high-pressure collecting pipe.

[0094] As an optional embodiment, in step (2), injecting liquid carbon dioxide into the low-pressure storage tank from the low-pressure storage shore station comprises the following steps:

[0095] (21) Connect the liquid phase header and the gas phase header to the loading facilities and gas delivery facilities of the storage shore station respectively, and set the flow path of the first remote control three-way valve to "1"→"2";

[0096] (22) The low-pressure liquid carbon dioxide from the low-pressure storage shore station flows through the liquid phase manifold and the first remote control three-way valve ("1"→"2") in sequence, and then the pressure of the liquid carbon dioxide is adjusted by the first pressure regulating valve, and finally injected into the low-pressure storage tank through the liquid inlet pipe.

[0097] As an optional embodiment, in step (22), the pressure of the liquid carbon dioxide after pressure regulation by the first pressure regulating valve is higher (for example, slightly higher) than the pressure of the low-pressure storage tank and can overcome the back pressure of being injected into the low-pressure storage tank.

[0098] As an optional embodiment, in step (2), the liquid carbon dioxide is injected into the low-pressure storage tank from the medium-pressure storage shore station or the high-pressure storage shore station, comprising the following steps:

[0099] (21) connecting the liquid phase header and the gas phase header to the loading facilities and gas transmission facilities of the medium pressure storage shore station or the high pressure storage shore station respectively, and setting the flow path of the first remote control three-way valve to "1"→"3";

[0100] (22) The low-pressure liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station is allowed to flow through the liquid phase manifold and the first remote-controlled three-way valve ("1"→"3") in sequence, and the injected liquid carbon dioxide is depressurized by the pressure reducing valve, and then the depressurized liquid carbon dioxide is cooled (i.e., further cooled) by the desuperheating heat exchanger so that the liquid carbon dioxide meets the storage requirements of the low-pressure storage tank; finally, the depressurized and cooled liquid carbon dioxide is injected into the low-pressure storage tank through the liquid inlet pipe.

[0101] As an optional embodiment, in step (22), the pressure of the liquid carbon dioxide after being decompressed by the pressure reducing valve is higher (for example, slightly higher) than the pressure of the low-pressure storage tank and can overcome the back pressure of being injected into the low-pressure storage tank.

[0102] In the present invention, during the process of outputting liquid carbon dioxide from a low-pressure storage tank, the liquid level in the low-pressure storage tank changes continuously, the gas phase space is expanded, and the pressure of the gas phase space changes accordingly. Based on safety considerations, the pressure in the low-pressure storage tank should always be higher than the triple point pressure of carbon dioxide, otherwise the liquid carbon dioxide will be converted into a gaseous or solid state. Therefore, when transporting liquid carbon dioxide to a low-pressure shore station, the gas phase space of the low-pressure storage tank should be connected to the gas phase space of the shore station tank through a gas collecting pipe and a gas phase collecting pipe, and the carbon dioxide gas flows in or out under the action of the pressure difference.

[0103] In order to prevent the pressure in the low-pressure storage tank from being lower than the pressure value of the triple point of carbon dioxide, it is necessary to transport and process the gaseous carbon dioxide in the low-pressure storage tank. Similarly, in the process of injecting liquid carbon dioxide into the low-pressure storage tank, the liquid level in the low-pressure storage tank is constantly changing, the gas phase space is compressed, and the pressure of the gas phase space changes accordingly. In order to prevent the pressure in the low-pressure storage tank from exceeding the design pressure value of the low-pressure storage tank, it is necessary to transport and process the gaseous carbon dioxide in the low-pressure storage tank. In view of the difference between the output and injection processes of liquid carbon dioxide, the present invention adopts different volatile gas transportation and processing methods.

[0104] For example, in the process of transporting liquid carbon dioxide to a low-pressure storage shore station, a medium-pressure storage shore station, or a high-pressure storage shore station, as the liquid carbon dioxide is transported out, the liquid level in the low-pressure storage tank continues to drop, the volume of the gas phase space increases, and the pressure drops accordingly. In order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide during the transport to the storage shore station, resulting in the formation of dry ice or gasification, a certain amount of gaseous carbon dioxide needs to be input from the outside, that is, gas return.

[0105] As an optional embodiment, in the step (31), in the process of exporting liquid carbon dioxide to the low-pressure storage shore station (i.e., in the low-pressure export process), in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the gas return includes the following steps:

[0106] Set the flow direction of the second remote-controlled three-way valve to "x"→"z", open the fifth isolation valve and the seventh isolation valve, and the gaseous carbon dioxide from the low-pressure storage shore station, under the action of the pressure difference, flows through the gas phase collecting pipe, the second remote-controlled three-way valve, the seventh isolation valve and the fifth isolation valve in sequence, and is transported to the gas phase space of the low-pressure storage tank through the gas collecting pipe.

[0107] As an optional embodiment, in the step (31), during the process of transporting liquid carbon dioxide to the low-pressure storage shore station, the pressure in the low-pressure storage tank is maintained unchanged or changes in a controllable manner.

[0108] As an optional embodiment, in the process of transferring liquid carbon dioxide from the low-pressure storage tank to the medium-pressure storage shore station or the high-pressure storage shore station in step (31), in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the storage shore station needs to replenish the low-pressure storage tank with CO2. 2 At this time, the pressure of the medium-pressure storage shore station or the high-pressure storage shore station exceeds the low-pressure storage pressure; gas return includes the following steps:

[0109] The flow path of the second remote-controlled three-way valve is set to "x"→"y", the sixth isolation valve is closed, and the eighth isolation valve is opened. Under the action of the pressure difference, the gaseous carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station flows through the gas phase header, the second remote-controlled three-way valve ("x"→"y"), the eighth isolation valve and the second pressure regulating valve in sequence. The gaseous carbon dioxide after being decompressed by the second pressure regulating valve is input into the gas phase space of the low-pressure storage tank through the gas header.

[0110] In the present invention, after the gaseous carbon dioxide is decompressed by the second pressure regulating valve, the pressure drops to the allowable pressure of the low-pressure storage tank.

[0111] As an optional embodiment, in the step (31), during the process of transporting liquid carbon dioxide to the medium-pressure storage shore station or the high-pressure storage shore station, the pressure in the low-pressure storage tank is maintained unchanged or changes in a controllable manner.

[0112] As an optional embodiment, in the step (32), in the process of injecting liquid carbon dioxide from the low-pressure storage shore station into the low-pressure storage tank, in order to prevent the pressure of the low-pressure storage tank from being higher than the design pressure of the low-pressure storage tank, the gas return to shore includes the following steps:

[0113] The flow path of the second remote-controlled three-way valve is set to "z"→"x", and the fifth isolation valve and the seventh isolation valve are opened. Under the action of the pressure difference, the excess gaseous carbon dioxide from the low-pressure storage tank flows through the gas phase header, the fifth isolation valve and the seventh isolation valve in sequence, and the second remote-controlled three-way valve ("z"→"x") is transported to the storage shore station through the gas phase header.

[0114] In the present invention, in the step (32), during the process of injecting liquid carbon dioxide from the low-pressure storage shore station into the low-pressure storage tank, the pressure in the low-pressure storage tank is maintained unchanged or changes in a controllable manner.

[0115] As an optional embodiment, in the step (33), during the process of injecting liquid carbon dioxide from the low-pressure storage shore station into the low-pressure storage tank, if the low-pressure storage shore station does not receive the returned gaseous carbon dioxide, the second remote control three-way valve is set to "z"→"y", the fifth isolation valve and the sixth isolation valve are opened, and the eighth isolation valve is closed at the same time; when the first pressure sensor detects that the pressure in the low-pressure storage tank rises to a set value (the set value can be adjusted according to operational needs, and can be the low-pressure storage tank design pressure minus 1 barg), an alarm signal is issued; (the operator) starts the gas compressor, and the excess gaseous carbon dioxide in the low-pressure storage tank is extracted and pressurized (or pressurized) by the gas compressor through the gas collecting pipe. After being pressurized by the gas compressor, the gaseous carbon dioxide enters the liquefaction device through the second remote control three-way valve ("z"→"y") and the sixth isolation valve. The pressurized gaseous carbon dioxide completes heat exchange with the refrigerant from the refrigeration unit in the liquefaction heat exchanger of the liquefaction device, is converted into liquid carbon dioxide, and then is injected into the low-pressure storage tank through the liquid inlet pipe.

[0116] In the present invention, during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the low-pressure storage tank, since the storage pressure of the medium-pressure storage shore station or the high-pressure storage shore station is much higher than the pressure in the low-pressure storage tank, natural gas return cannot be achieved through the pressure difference. In this case, after the excess gaseous carbon dioxide in the low-pressure storage tank is extracted and increased by the gas compressor, the excess gaseous carbon dioxide in the low-pressure storage tank is returned to the medium-pressure storage shore station or the high-pressure storage shore station under the action of the pressure difference.

[0117] As an optional implementation, in the step (32), during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the low-pressure storage tank, when the pressure of the low-pressure storage tank is higher than the pressure setting value of the low-pressure storage tank, the second remote control three-way valve is set to "z"→"x", the fifth isolation valve is opened, and the seventh isolation valve is closed; when the pressure of the low-pressure storage tank monitored by the first pressure sensor reaches the pressure setting value (the setting value can be adjusted according to operational needs, and can be the low-pressure storage tank design pressure minus 1 barg), the gas compressor is started to Excess gaseous carbon dioxide in the low-pressure storage tank is extracted (through the gas collecting pipe) and pressurized, so that the pressure of the gaseous carbon dioxide after being pressurized by the gas compressor is higher than (such as slightly higher than) the storage pressure of the medium-pressure storage shore station or the high-pressure storage shore station, and then returned to the medium-pressure storage shore station or the high-pressure storage shore station through the gas phase collecting pipe via the second remote control three-way valve ("z"→"x"); optionally, the gas compressor adopts variable frequency control or multi-stage compressor inter-stage parallel operation to comprehensively adjust the compressor outlet pressure, that is, the pressure rise value of the gaseous carbon dioxide after passing through the gas compressor.

[0118] In the present invention, in the step (32), during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the low-pressure storage tank, the pressure in the low-pressure storage tank is maintained unchanged or changes in a controllable manner.

[0119] As an optional implementation, in the step (33), during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the low-pressure storage tank, when the pressure of the low-pressure storage tank is higher than the pressure setting value of the low-pressure storage tank, if the medium-pressure storage shore station or the high-pressure storage shore station does not receive the returned gaseous carbon dioxide, the excess gaseous carbon dioxide in the low-pressure storage tank is liquefied by the liquefaction device and then returned to the low-pressure storage tank in step (32). Specifically, the excess gaseous carbon dioxide in the low-pressure storage tank is extracted and pressurized by a gas compressor, and the gaseous carbon dioxide pressurized by the gas compressor enters the liquefaction device and is converted into liquid carbon dioxide, which is then injected into the low-pressure storage tank.

[0120] As an optional implementation, in the step (31), during the process of transporting liquid carbon dioxide from the low-pressure storage tank to the storage shore station, if the storage shore station cannot provide the gas return in the step (31), self-evaporation pressure maintenance treatment is required, that is, the self-evaporation pressure maintenance system is required to control the pressure in the low-pressure storage tank to avoid the pressure being lower than the triple point pressure of carbon dioxide.

[0121] Specifically, in step (4), the pressure of the gas phase space in the low-pressure storage tank is monitored in real time by a first pressure sensor. When the pressure drops to the low-pressure setting value, the first pressure sensor sends a signal to open the pressure control valve, so that the self-evaporation pressure-maintaining system is connected to the liquid outflow pipe. At this time, part of the externally transmitted liquid carbon dioxide enters the self-evaporation pressure-maintaining pipe. This part of the liquid carbon dioxide is gasified by the evaporator and then returned to the low-pressure storage tank by the gas collecting pipe. As the gaseous carbon dioxide continues to enter, the pressure in the low-pressure storage tank gradually increases. When the pressure rises to the high-pressure setting value, the first pressure sensor sends a signal again to close the pressure control valve, and the self-evaporation pressure-maintaining process ends.

[0122] As an optional implementation, the transfer method of a low-pressure liquid carbon dioxide storage and transportation ship is also applicable to transfer operations between carbon dioxide ships with different storage pressures.

[0123] In the present invention, the above technical features can be freely combined to form a new technical solution without conflicting with each other.

[0124] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0125] (1) The transfer method of the low-pressure liquid carbon dioxide storage and transportation ship provided by the present invention has a multi-process design, and the operator can reasonably select different operation processes according to the storage conditions of the matching storage shore station, effectively compatible with the medium-pressure storage shore station or the high-pressure storage shore station, and greatly improve the compatibility of the ship;

[0126] (2) The liquefaction system and transfer method of the low-pressure liquid carbon dioxide storage and transportation ship provided by the present invention, by setting a self-evaporation pressure maintenance system and a process for liquefying excess gaseous carbon dioxide back into the tank, enhances the ability of the ship to control the tank pressure during loading and unloading, reduces the dependence of ship operations on storage shore facilities, and further improves the flexibility of ship operations;

[0127] (3) The transfer method of the low-pressure liquid carbon dioxide storage and transportation ship provided by the present invention adopts a targeted design of the operation process, and the relevant setting parameters can be adjusted according to the actual situation of the docking storage station, which effectively reduces the ship's operating energy consumption and improves the ship's economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0128] Figure 1 A schematic diagram showing the division of a liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship according to the present invention;

[0129] Figure 2 A schematic diagram showing the composition of a liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship according to the present invention;

[0130] Figure 3A diagram showing the composition of a medium-pressure temperature-raising device in a liquid cargo system of a low-pressure ship storing and transporting liquid carbon dioxide according to the present invention;

[0131] Figure 4 A diagram showing the composition of a low-pressure pressure regulating unit in a liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship according to the present invention;

[0132] Figure 5 A diagram showing the composition of a low-pressure temperature control unit in a liquid cargo system of a low-pressure ship storing and transporting liquid carbon dioxide according to the present invention;

[0133] Figure 6 A diagram showing the composition of a high-pressure temperature-raising device in a liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship according to the present invention;

[0134] Figure 7 A diagram showing the composition of a liquefaction device in a liquid cargo system of a low-pressure ship for storing and transporting liquid carbon dioxide according to the present invention;

[0135] Figure 8 Represents the three-phase diagram of carbon dioxide.

[0136] The marks in the figure are: 1- low-pressure storage tank, 2- delivery pump, 3- pressure control valve, 4- evaporator, 5- first pressure sensor, 6- first isolation valve, 7- medium-pressure booster pump, 8- medium-pressure heating device, 9- first check valve, 10- second isolation valve, 11- low-pressure pressure regulating unit, 12- low-pressure temperature control unit, 13- second check valve, 14- third isolation valve, 15- high-pressure booster pump, 16- high-pressure heating device, 17- pressure reducing valve, 1 8-Desuperheating heat exchanger, 19-Refrigeration unit, 20-First remote control three-way valve, 21-Second remote control three-way valve, 22-First pressure regulating valve, 23-Gas compressor, 24-Fifth isolation valve, 25-Sixth isolation valve, 26-Liquidation device, 27-Seventh isolation valve, 28-Second pressure regulating valve, 29-Eighth isolation valve; L1-Liquid outgoing pipe, L2-Liquid ingoing pipe, L3-Low-pressure external transmission pipe, Medium-pressure external transmission pipe L4, High-pressure external transmission pipe L5 , L6-liquefied tank return pipe, L7-gas return pipe, L8-bypass pipe, V1-self-evaporation pressure-maintaining pipe, V2-gas collecting pipe, C1-liquid phase collecting pipe, C2-gas phase collecting pipe, C3-high-pressure collecting pipe; I-low-pressure external transmission system, II-medium-pressure external transmission system, III-high-pressure external transmission system, IV-self-evaporation pressure-maintaining system, V-medium / high-pressure injection system, VI-low-pressure injection system, VII-volatile gas transportation and treatment system; 8-1-medium-pressure heater, 8-2-medium-pressure heater, 8-3-medium-pressure heater, 8-4-medium-pressure heater, 8-5-medium-pressure heater, 8-6-medium-pressure heater, 8-7-medium-pressure heater, 8-8-1-medium-pressure heater, 8-9-medium-pressure heater, 8-1 ... -2-first temperature control valve, 8-3-medium pressure temperature sensor; 11-1-pressure regulating valve, 11-2-controller, 11-3-second pressure sensor; 12-1-low pressure heat exchanger, 12-2-heat exchange medium source, 12-3-temperature control three-way valve, 12-4-low pressure temperature sensor; 16-1-high pressure heater, 16-2-second temperature control valve, 16-3-high pressure temperature sensor; 26-1-liquefaction heat exchanger; 26-2-refrigeration unit. DETAILED DESCRIPTION

[0137] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0138] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0139] Some embodiments of the present invention provide a liquid cargo system for a low-pressure storage and transportation vessel of liquid carbon dioxide, such as Figure 1 As shown, the liquid cargo system includes: a low-pressure storage tank 1, a delivery pump 2, an external transmission system (including a low-pressure external transmission system I, a medium-pressure external transmission system II, and a high-pressure external transmission system III), a self-evaporation pressure-maintaining system IV, an injection system (including a medium / high-pressure injection system V and a low-pressure injection system VI), and a volatile gas transmission and treatment system VII; Figure 2 As shown, the liquid cargo system also includes a liquid phase header C1, a high pressure header C3, a gas phase header C2, a gas header V2, a self-evaporation pressure-maintaining pipe V1, a liquid inlet pipe L2 and a liquid outlet pipe L1; wherein,

[0140] The low-pressure storage tank 1 is used for storing liquid carbon dioxide at low pressure;

[0141] The delivery pump 2 is connected to the liquid outflow pipe L1 and is used to deliver the liquid carbon dioxide in the low-pressure storage tank 1 to the outside;

[0142] The external transmission system comprises a low-pressure external transmission system I, a medium-pressure external transmission system II and a high-pressure external transmission system III arranged in parallel, and its input end is connected to the liquid outflow pipe L1, and is used to transport liquid carbon dioxide to storage shore stations with different storage pressures (including low-pressure storage shore stations, medium-pressure storage shore stations and high-pressure storage shore stations); wherein the output ends of the low-pressure external transmission system I and the medium-pressure external transmission system II are connected to the liquid phase header C1; the output end of the high-pressure external transmission system III is connected to the high-pressure header C3;

[0143] The input end of the self-evaporation pressure-maintaining system IV is connected to the liquid outflow pipe L1, and the output end is connected to the gas collecting pipe V2, so as to control the pressure in the low-pressure storage tank 1 when the liquid carbon dioxide is transported out;

[0144] The injection system is connected to the liquid phase manifold C1 through the first remote control three-way valve 20, and its output end is connected to the liquid inlet pipe L2, and is used to inject the liquid carbon dioxide in the storage shore station into the low-pressure storage tank 1; the storage shore station includes a low-pressure storage shore station, a medium-pressure storage shore station and a high-pressure storage shore station;

[0145] The volatile gas delivery and treatment system VII is used to deliver and treat the volatile gas and balance the system pressure during the process of transporting or injecting carbon dioxide; its output end is connected to the liquid inlet pipe L2 and the gas collecting pipe V2 respectively;

[0146] The liquid phase header C1 is connected to a low-pressure storage shore station or a medium-pressure storage shore station for receiving or outputting liquid carbon dioxide;

[0147] The gas phase header C2 is used to receive or output gaseous carbon dioxide.

[0148] In the present invention, the low-pressure external transmission system I, the medium-pressure external transmission system II, and the high-pressure external transmission system III are respectively connected to the liquid outflow pipe L1 and arranged in parallel. Therefore, according to the storage pressure of the liquid carbon dioxide receiving and storage shore station, one external transmission system is selected. For example, if the liquid carbon dioxide receiving and storage shore station is a low-pressure storage shore station, the low-pressure external transmission system I is selected to externally transmit the liquid carbon dioxide in the low-pressure storage tank 1 to the low-pressure storage shore station; if the liquid carbon dioxide receiving and storage shore station is a high-pressure storage shore station, the high-pressure external transmission system III is selected to externally transmit the liquid carbon dioxide in the low-pressure storage tank to the high-pressure storage shore station.

[0149] In some embodiments, the liquid phase header C1 is connected to a low-pressure storage shore station or a medium-pressure storage shore station by connecting loading / unloading facilities (such as a liquid phase interface of a loading / unloading arm or a loading / unloading hose).

[0150] In some embodiments, the high-pressure header C3 is connected to a high-pressure storage shore station via a connection to loading / unloading facilities (such as a liquid interface of a loading / unloading arm or a loading / unloading hose).

[0151] In some embodiments, the gas phase manifold C2 is connected to a gas delivery facility, such as a loading and unloading arm or a loading and unloading hose gas phase interface.

[0152] In some embodiments, the input end of the liquid inlet pipe L2 is respectively connected to the medium / high pressure injection system V and the low pressure injection system VI, and the opening of the output end is arranged in the low pressure storage tank 1.

[0153] In some embodiments, the input end of the liquid inlet pipe L2 is also connected to the liquefied return pipe L6 of the volatile gas transport and treatment system VII.

[0154] In some embodiments, the output end of the self-evaporation pressure maintaining system IV is connected to the gas collecting pipe V2; the opening of the gas collecting pipe V2 communicating with the low-pressure storage tank 1 is arranged at the top of the low-pressure storage tank 1.

[0155] In some embodiments, the output end of the volatile gas transport and treatment system VII is connected to the liquid inlet pipe L2 and the gas collecting pipe V2 respectively.

[0156] In some embodiments, the low-pressure storage tank 1 adopts a C-type storage tank defined by IMO. The material of the low-pressure storage tank meets the pressure and temperature requirements for low-pressure storage of liquid carbon dioxide, and is coated with insulation material. The insulation material has a low thermal conductivity, including polyurethane or polystyrene. The insulation material is installed on the outside of the low-pressure storage tank 1 by using a prefabricated insulation module or on-site spray foaming method.

[0157] In some embodiments, the transfer pump 2 is installed inside the low-pressure storage tank 1 and can be a deep-well pump or a submerged pump. Its outlet is connected to the liquid out-of-cabin pipe L1; one end of the liquid out-of-cabin pipe L1 is connected to the outlet of the transfer pump 2, and the other end is connected to multiple external transfer system pipes and the self-evaporation pressure-maintaining pipe V1.

[0158] In the present invention, the low-pressure external transfer system I, the medium-pressure external transfer system II, and the high-pressure external transfer system III are respectively connected to the liquid out-of-cabin pipe L1 and are arranged in parallel. One of them is selected according to the storage pressure of the liquid carbon dioxide receiving and storing shore station; for the self-evaporation pressure-maintaining system IV, one end is connected to the liquid out-of-cabin pipe L1, and the other end is connected to the gas collecting pipe V2; for the gas collecting pipe V2, one end opens at the top of the low-pressure storage tank 1, and the other end is also connected to the volatile gas transfer and treatment system VII.

[0159] In some embodiments, as Figure 2 shown, the low-pressure external transfer system I includes a second isolation valve 10, a low-pressure pressure-regulating unit 11, a low-pressure temperature-control unit 12, and a second one-way valve 13; the second isolation valve 10 is arranged on the low-pressure external transfer pipeline L3 of the low-pressure external transfer system I and is used to control the on and off of the low-pressure external transfer pipe L3; the low-pressure pressure-regulating unit 11 is used to control the pressure of the externally transferred liquid carbon dioxide in the low-pressure external transfer system I; the low-pressure temperature-control unit 12 is used to control the temperature of the externally transferred liquid carbon dioxide in the low-pressure external transfer system 1. The second one-way valve 13 plays a role in preventing liquid backflow, and its outlet is connected to the liquid-phase collecting pipe C1; the liquid-phase collecting pipe C1 is connected to loading and unloading facilities, such as the liquid-phase interfaces of loading and unloading arms or loading and unloading hoses.

[0160] In some embodiments, as Figure 4 shown, the low-pressure pressure-regulating unit 11 includes a pressure-regulating valve 11-1, a controller 11-2, and a second pressure sensor 11-3. The second pressure sensor 11-3 is installed downstream of the pressure-regulating valve 11-1 and is used to monitor the pressure of the fluid (i.e., liquid carbon dioxide) in the low-pressure external transfer pipe L3 and transmit the measured value to the controller 11-2; the controller 11-2 receives the pressure set value and compares it with the actual measured pressure value, and then controls the pressure-regulating valve 11-1 so that the pressure of the fluid flowing through the pressure-regulating valve 11-1 tends to the pressure set value. As Figure 5As shown, the low-pressure temperature control unit 12 includes a low-pressure heat exchanger 12-1, a heat exchange medium source 12-2, a temperature control three-way valve 12-3 and a low-pressure temperature sensor 12-4. The pressure-regulated liquid carbon dioxide enters the low-pressure temperature control unit 12 for diversion, a part of which passes through the low-pressure heat exchanger 12-1 and is connected to the interface "a" of the temperature control three-way valve 12-3, and the remaining part of the liquid carbon dioxide is connected to the interface "c" of the temperature control three-way valve 12-3 through a pipeline; the temperature control three-way valve 12-3 has linear adjustment capability and is connected to the system through the three interfaces "a", "b" and "c"; the low-pressure temperature sensor 12-4 is used to monitor the temperature of the liquid carbon dioxide, and by adjusting the opening of the temperature control three-way valve 12-3, that is, the flow ratio of "ab" and "cb", the amount flowing through the low-pressure heat exchanger 12-1 is controlled, thereby controlling the temperature of the mixed liquid carbon dioxide to meet the design requirements; the low-pressure heat exchanger can be a plate type or a shell and tube type; the heat exchange medium source 12-2 controls the temperature of the heat exchange medium through a secondary heat exchange cycle, and provides the low-pressure heat exchanger with pre-cooled heat exchange medium, and the heat exchange medium can be ethylene glycol water or other low-freezing point liquids.

[0161] In some embodiments, Figure 2 As shown, the medium-pressure external transmission system II includes a first isolating valve 6, a medium-pressure boosting pump 7, a medium-pressure heating device 8 and a first non-return valve 9; one end of the system is connected to the liquid outflow pipe L1 through a medium-pressure external transmission pipe L4, and a first isolating valve 6 is provided on the medium-pressure external transmission pipe L4 to control the on and off of the medium-pressure external transmission pipe L4; the medium-pressure boosting pump 7 can be a centrifugal pump or a volumetric pump, which is used to increase the pressure of the liquid carbon dioxide from the delivery pump 2 to meet the pressure requirement of the medium-pressure storage shore station; the medium-pressure heating device 8 is used to increase the temperature of the pressurized liquid carbon dioxide to meet the temperature requirement of the medium-pressure storage shore station; the outlet of the first non-return valve 9 is connected to the liquid phase manifold C1 to prevent liquid reflux.

[0162] In some embodiments, Figure 3 As shown, the medium-pressure heating device 8 includes: a medium-pressure heater 8-1, a first temperature control valve 8-2 and a medium-pressure temperature sensor 8-3; the medium-pressure temperature sensor 8-3 is used to monitor the temperature of the pressurized liquid carbon dioxide and control the opening of the first temperature control valve 8-2; the first temperature control valve 8-2 can be pneumatically, electrically or hydraulically driven, and its opening is controlled by the medium-pressure temperature sensor 8-3, which is used to adjust the amount of heat exchange medium entering the medium-pressure heater 8-1, thereby controlling the temperature of the liquid carbon dioxide passing through the medium-pressure heat exchanger; the medium-pressure heater 8-1 can be a plate type or a shell and tube type, and the heat exchange medium can be seawater, fresh water, steam, hot oil or ethylene glycol water.

[0163] In some embodiments, Figure 2As shown, the high-pressure external transmission system III includes: a third isolation valve 14, a high-pressure boosting pump 15 and a high-pressure heating device 16; one end of the high-pressure external transmission system III is connected to the liquid outflow pipe L1 through a high-pressure external transmission pipe L5, and a third isolation valve 14 is provided on the high-pressure external transmission pipe L5 to control the on and off of the high-pressure external transmission pipe L5; the high-pressure boosting pump 15 can be a centrifugal pump or a volumetric pump, which is used to increase the pressure of the liquid carbon dioxide from the delivery pump 2 to meet the requirements of the high-pressure storage shore station; the high-pressure heating device 16 is used to increase the temperature of the pressurized liquid carbon dioxide to meet the temperature requirements of the high-pressure storage shore station, and its outlet is connected to the high-pressure header C3.

[0164] In some embodiments, Figure 6 As shown, the high-pressure temperature increasing device 16 includes: a high-pressure heater 16-1, a second temperature control valve 16-2 and a high-pressure temperature sensor 16-3; the high-pressure temperature sensor 16-3 is installed at the outlet of the high-pressure heater 16-1, and is used to monitor the temperature of the pressurized liquid carbon dioxide and control the opening of the second temperature control valve 16-2; the second temperature control valve 16-2 can be pneumatically, electrically or hydraulically driven, and its opening is controlled by the high-pressure temperature sensor 16-3, and is used to adjust the amount of heat exchange medium entering the high-pressure heater 16-1, thereby controlling the temperature of the liquid carbon dioxide passing through the high-pressure heater 16-1; the high-pressure heater 16-1 can be a plate type or a shell and tube type, and the heat exchange medium can be electricity, steam, hot oil or ethylene glycol water.

[0165] In some embodiments, Figure 2 As shown, the self-evaporation pressure-maintaining system IV includes: a pressure control valve 3, an evaporator 4 and a first pressure sensor 5; one end of the pressure control valve 3 is connected to the liquid outflow pipe L1 through the self-evaporation pressure-maintaining pipe V1, and the other end is connected to the gas collecting pipe V2; the pressure control valve 3 can be pneumatically, electrically or hydraulically driven, and is controlled to open and close by the first pressure sensor 5, and the first pressure sensor 5 is installed on the top of the low-pressure storage tank 1 to monitor the pressure of the gas phase space at the top of the low-pressure storage tank 1; the evaporator 4 can be a plate type or a shell and tube type, and its heat source can be electricity, steam or hot oil, which is used to evaporate liquid carbon dioxide into gaseous carbon dioxide and return it to the low-pressure storage tank 1 through the gas collecting pipe V2.

[0166] In some embodiments, Figure 2As shown, the medium / high-pressure injection system V and the low-pressure injection system VI are installed in parallel. One end is connected to the first remotely controlled three-way valve 20, and the other end is connected to the liquid inlet pipe L2 of the tank; the first remotely controlled three-way valve 20 has three interfaces "1", "2", and "3", where the interface "1" is connected to the liquid phase header C1; the interface "2" is connected to the low-pressure injection system VI; the interface "3" is connected to the medium / high-pressure injection system V, and different injection systems can be selected according to the pressure of the liquid carbon dioxide input by the storage shore station; the liquid inlet pipe L2 of the tank, one end of which is connected to the medium / high-pressure injection system V, the low-pressure injection system VI, and the liquefied return pipe L6, and the other end opens in the low-pressure storage tank 1.

[0167] In some embodiments, such as Figure 2 As described, the low-pressure injection system VI includes: a first pressure regulating valve 22; one end of which is connected to the interface "2" of the first remotely controlled three-way valve 20, and the other end is connected to the liquid inlet pipe L2 of the tank; the first pressure regulating valve 22 can be a diaphragm type, a spring piston type or a bellows type, and controls the pressure of the injected liquid carbon dioxide within a set range.

[0168] In some embodiments, such as Figure 2 As shown, the medium / high-pressure injection system V includes a pressure reducing valve 17, a temperature reducing heat exchanger 18 and a refrigeration unit 26-2; one end of which is connected to the interface "3" of the first remotely controlled three-way valve 20, and the other end is connected to the liquid inlet pipe L2 of the tank; the pressure reducing valve 17 can be a spring type or a piston type, and is used to reduce the pressure of the medium-pressure or high-pressure injected liquid carbon dioxide. The temperature reducing heat exchanger 18 can be a plate type, a shell and tube type or a printed circuit board type; the liquid carbon dioxide passes through the temperature reducing heat exchanger 18 and exchanges heat with the refrigerant from the refrigeration unit 26-2, and can further cool the depressurized liquid carbon dioxide so that its temperature meets the storage requirements of the low-pressure storage tank 1; the refrigeration unit 26-2 provides refrigerant for the temperature reducing heat exchanger 18, and the refrigerant can be propane or propylene.

[0169] In some embodiments, such as Figure 2 As shown, the volatile gas transportation and treatment system VII includes a second remotely controlled three-way valve 21, a gas compressor 23, a liquefaction device 26, a second pressure regulating valve 28, and the liquefied return pipe L6 and the gas return pipe L7 that make up the system; the second remotely controlled three-way valve 21 is used to control the flow direction of the volatile gas and has three interfaces "x", "y", and "z", where the interface "x" is connected to the gas phase header C2; the interface "y" is respectively connected to the liquefied return pipe L6 and the gas return pipe L7; the interface "z" is connected to the outlet of the gas compressor 23; it can be selected according to the needs of the transfer (or barge) operation; the gas phase header C2 is connected to the gas transportation facility, such as the gas phase interface of the loading and unloading arm or the loading and unloading hose.

[0170] In some embodiments, such as Figure 2As shown, the gas compressor 23 can be a screw type or a piston type, and its air inlet side is connected to the gas collecting pipe V2 through the fifth isolating valve 24, and its outlet is connected to the interface "z" of the second remote control three-way valve 21. The volatile gas compressed by the gas compressor 23 can pass through the second remote control three-way valve 21 "z" → ​​"x" and return to the storage shore station receiving device through the gas phase collecting pipe C2, or connect to the liquefied return tank pipe L6 through the second remote control three-way valve 21 "z" → ​​"y", and return to the low-pressure storage tank 1 after liquefaction by the liquefaction device 26; the inlet and outlet of the gas compressor 23 are also provided with a bypass pipe L8 and a seventh isolating valve 27, which are used to bypass the gas compressor 23 to realize the natural flow of gaseous carbon dioxide.

[0171] In some embodiments, Figure 2 As shown, a sixth isolation valve 25 is provided on the liquefied return tank pipe L6; a liquefaction device 26 is installed downstream of the sixth isolation valve 25, and the liquefaction device 26 includes a liquefied heat exchanger 26-1 and a refrigeration unit 26-2 (such as Figure 7 As shown,); the liquefied heat exchanger 26-1 can be a plate type, a shell and tube type or a printed circuit board type, which can cool and liquefy the compressed gaseous carbon dioxide; the refrigeration unit 26-2 provides a refrigerant for the liquefied heat exchanger 26-1, and the refrigerant can be propane or propylene. The liquefied carbon dioxide returns to the low-pressure storage tank 1 through the liquid inlet pipe L2; the gas return pipe L7 is provided with an eighth isolation valve 29 and a second pressure regulating valve 28, and the second pressure regulating valve 28 can be a diaphragm type, a spring piston type or a bellows type, which adjusts the pressure of the gaseous carbon dioxide from the storage shore station so that the pressure meets the requirement of returning to the low-pressure storage tank 1.

[0172] Some embodiments of the present invention further provide a method for transferring a low-pressure liquid carbon dioxide storage and transportation ship, using the liquid cargo system of the low-pressure liquid carbon dioxide storage and transportation ship to transfer, and the transfer method comprises the following steps:

[0173] Step S1: transporting liquid carbon dioxide to the storage shore station, including the following steps:

[0174] Step S11: connect the liquid phase header / high-pressure header and the gas phase header to the unloading facilities and gas transmission facilities of the storage shore station respectively, select the storage shore station with the required storage pressure, and connect the external transmission system to the liquid outflow pipe;

[0175] Step S12: The liquid carbon dioxide in the low-pressure storage tank is outputted through a delivery pump and delivered to a storage shore station through an external delivery system;

[0176] Step S2: injecting liquid carbon dioxide into the low-pressure storage tank from the storage shore station, including the following steps:

[0177] Step S21: connecting the liquid phase header and the gas phase header to the loading facilities and gas delivery facilities of the storage shore station respectively, and selecting the flow path of the remote control three-way valve according to the storage pressure of the storage shore station;

[0178] Step S22: allowing the liquid carbon dioxide from the storage shore station to flow through the liquid phase header and the remote control three-way valve in sequence, enter the injection system, adjust the pressure and temperature of the carbon dioxide injected into the system, and then inject it into the low-pressure storage tank;

[0179] Step S3: volatile gas delivery and processing, including the following steps:

[0180] Step S31: In the process of transporting liquid carbon dioxide from the low-pressure storage tank to the storage shore station, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the gaseous carbon dioxide from the storage shore station is transported to the low-pressure storage tank (i.e., the gas phase space of the low-pressure storage tank) through the gas header under the action of the pressure difference, i.e., gas return;

[0181] Step S32: During the process of injecting liquid carbon dioxide from the storage shore station into the low-pressure storage tank, when the pressure of the low-pressure storage tank is higher than the pressure setting value of the low-pressure storage tank, the gaseous carbon dioxide in the low-pressure storage tank is transported back to the storage shore station through the gas phase header under the action of the pressure difference;

[0182] Step S33: In step S31 or step S32, if the storage shore station does not receive the returned gaseous carbon dioxide, the excess gaseous carbon dioxide in the low-pressure storage tank is extracted and pressurized by a gas compressor, and the gaseous carbon dioxide pressurized by the gas compressor enters a liquefaction device to be converted into liquid carbon dioxide, and then injected into the low-pressure storage tank;

[0183] Step S34: during the process of transferring liquid carbon dioxide from the low-pressure storage tank to the storage shore station, if the pressure of the low-pressure storage tank increases, in order to prevent the pressure of the low-pressure storage tank from being higher than the design pressure of the low-pressure storage tank, the operation of step 32 is adopted; that is, the gaseous carbon dioxide in the low-pressure storage tank is transferred back to the storage shore station through the gas phase header under the action of the pressure difference;

[0184] Step S35: During the process of injecting liquid carbon dioxide from the storage shore station into the low-pressure storage tank, if the pressure of the low-pressure storage tank drops, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the operation of step 31 is adopted; that is, the gas collecting pipe is connected with the gas phase space of the storage shore station through the gas phase collecting pipe, and the gaseous carbon dioxide of the storage shore station is transported to the low-pressure storage tank through the gas collecting pipe under the action of the pressure difference, that is, gas return;

[0185] Step S4: self-evaporation pressure-maintaining treatment, including the following steps:

[0186] When the pressure of the gas phase space in the low-pressure storage tank drops to the low-pressure setting value, the pressure control valve is opened to connect the self-evaporation pressure maintaining system with the liquid outflow pipe, and part of the externally transported liquid carbon dioxide enters the self-evaporation pressure maintaining pipe, is gasified by the evaporator gasifier, and is returned to the low-pressure storage tank through the gas collecting pipe; when the pressure of the gas phase space in the low-pressure storage tank rises to the high-pressure setting value, the pressure control valve is closed, and the self-evaporation pressure maintaining process ends.

[0187] In some embodiments, in step S1, liquid carbon dioxide is transported to a low-pressure storage shore station (referred to as method S1-1), and the specific steps are as follows:

[0188] Step S11, connect the liquid phase header C1 and the gas phase header C2 to the unloading facility and the gas transmission facility respectively, close the first isolation valve 6 and the third isolation valve 14, disconnect the medium-pressure external transmission system II and the high-pressure external transmission system III; open the second isolation valve 10, so that the low-pressure external transmission system I is connected to the liquid outflow pipe L1;

[0189] Step S12, start the delivery pump 2, the liquid carbon dioxide in the low-pressure storage tank 1 is output through the delivery pump 2, and enters the low-pressure external transmission pipe L3 through the liquid outlet pipe L1; the liquid carbon dioxide entering the low-pressure external transmission pipe L3 is adjusted in pressure and temperature through the low-pressure pressure regulating unit 11 and the low-pressure temperature control unit 12 in turn; the pressure-regulated and temperature-controlled liquid carbon dioxide passes through the second one-way valve 13 and enters the liquid phase header C1, and is transported outward through the unloading facilities connected to the liquid phase header C1, thereby completing the delivery of liquid carbon dioxide to the low-pressure storage shore station.

[0190] In some embodiments, in step S1, liquid carbon dioxide is transported to a medium pressure storage shore station (referred to as method S1-2), and the specific steps are as follows:

[0191] Step S11, connect the liquid phase header C1 and the gas phase header C2 to the unloading facility and the gas transmission facility respectively, close the second isolation valve 10 and the third isolation valve 14, disconnect the low-pressure external transmission system I and the high-pressure external transmission system III; open the first isolation valve 6, so that the medium-pressure external transmission system II is connected to the liquid outflow pipe L1;

[0192] Step S12, start the delivery pump 2, the liquid carbon dioxide in the low-pressure storage tank 1 is output through the delivery pump 2, and enters the medium-pressure external transmission pipe L4 through the liquid outlet pipe L1; the liquid carbon dioxide entering the medium-pressure external transmission pipe L4 is pressurized by the medium-pressure booster pump 7, and the pressurized liquid carbon dioxide passes through the medium-pressure heating device 8 to increase the temperature of the liquid carbon dioxide, so that the pressure and temperature of the liquid carbon dioxide meet the requirements of the medium-pressure storage shore station; the pressurized and heated liquid carbon dioxide passes through the first one-way valve 9 and enters the liquid phase header C1, and is transported outward through the unloading facilities connected to the liquid phase header C1, thereby completing the delivery of liquid carbon dioxide to the medium-pressure storage shore station.

[0193] In some embodiments, in step S1, liquid carbon dioxide is transported to a high-pressure storage shore station (referred to as method S1-3), and the specific steps are as follows:

[0194] Step S11, connect the high-pressure header C3 and the gas-phase header C2 to the unloading facility and the gas delivery facility respectively, close the first isolation valve 6 and the second isolation valve 10, disconnect the low-pressure external transmission system I and the medium-pressure external transmission system II; open the third isolation valve 14, so that the high-pressure external transmission system III is connected to the liquid outflow pipe L1;

[0195] Step S12, start the delivery pump 2, the liquid carbon dioxide in the low-pressure storage tank 1 is output through the delivery pump 2, and enters the high-pressure external transmission pipe L5 through the liquid outlet pipe L1; the liquid carbon dioxide entering the high-pressure external transmission pipe L5 is pressurized by the high-pressure booster pump 15, and the pressurized liquid carbon dioxide is then passed through the high-pressure heating device 16 to increase the temperature of the liquid carbon dioxide, so that the pressure and temperature of the liquid carbon dioxide meet the requirements of the high-pressure storage shore station; the pressurized and heated liquid carbon dioxide is transported outward through the high-pressure collecting pipe C3, and the liquid carbon dioxide is transported to the high-pressure storage shore station.

[0196] In some embodiments, in step S2, liquid carbon dioxide is injected from a low-pressure storage shore station (referred to as method S2-1), and the specific steps are as follows:

[0197] Step S21, connecting the liquid phase header C1 and the gas phase header C2 to the loading facilities and gas transportation facilities of the storage shore station respectively, and setting the flow path of the first remote control three-way valve 20 to "1"→"2";

[0198] Step S22: The low-pressure liquid carbon dioxide from the storage shore station flows through the liquid phase header C1 and the first remote control three-way valve 20 ("1"→"2") in sequence, and then is injected into the low-pressure storage tank 1 through the liquid inlet pipe L2 after the pressure is adjusted by the first pressure regulating valve 22. The pressure adjusted by the first pressure regulating valve 22 is slightly higher than the pressure in the low-pressure storage tank 1, and can overcome the back pressure of the injection into the low-pressure storage tank 1.

[0199] In some embodiments, in step S2, liquid carbon dioxide is injected from a medium-pressure storage shore station or a high-pressure storage shore station (referred to as: method S2--2), and the specific steps are as follows:

[0200] Step S21, connecting the liquid phase header C1 and the gas phase header C2 to the loading facilities and gas transportation facilities of the storage shore station respectively, and setting the flow path of the first remote control three-way valve 20 to "1"→"3";

[0201] Step S22, the medium-pressure or high-pressure liquid carbon dioxide from the storage shore station, under the action of the pressure difference, flows through the liquid phase header C1 and the first remote-controlled three-way valve 20 ("1"→"3") in sequence, and the pressure of the injected liquid carbon dioxide is reduced to a pressure slightly higher than the pressure in the low-pressure storage tank 1 through the pressure reducing valve 17, and is sufficient to overcome the back pressure of the injection into the low-pressure storage tank 1. The decompressed liquid carbon dioxide is further cooled by the desuperheating heat exchanger 18 so that its temperature meets the storage requirements of the low-pressure storage tank 1; the decompressed and cooled liquid carbon dioxide is injected into the low-pressure storage tank 1 through the liquid inlet pipe L2.

[0202] In the present invention, during the process of outputting or injecting liquid carbon dioxide into the low-pressure storage tank 1, the liquid level in the low-pressure storage tank 1 changes continuously, the gas phase space is compressed or expanded, and the pressure of the gas phase space changes accordingly. In order to prevent the pressure in the low-pressure storage tank 1 from being lower than the pressure of the triple point of carbon dioxide or exceeding the design pressure value of the low-pressure storage tank 1, it is necessary to transport and process the gaseous carbon dioxide in the low-pressure storage tank 1. Different processing steps are adopted for different processes.

[0203] In some embodiments, in step S3, the volatile gas delivery and processing includes the following steps:

[0204] Liquid carbon dioxide is transported to the low-pressure storage shore station (referred to as: method S3-1). As the liquid carbon dioxide is transported, the liquid level in the low-pressure storage tank 1 continues to drop, the volume of the gas phase space increases, and the pressure decreases accordingly. In order to prevent the pressure in the low-pressure storage tank 1 from being lower than the triple point pressure of carbon dioxide (5.2 barg, such as Figure 8 As shown), resulting in the formation of dry ice or vaporization, a certain amount of gaseous carbon dioxide needs to be input from the outside, that is, gas return. The operation of gas return includes: during the low-pressure external transmission operation, the flow direction of the second remote control three-way valve 21 is set to "x" → "z", and the fifth isolation valve 24 and the seventh isolation valve 27 are opened. At this time, the gaseous carbon dioxide from the low-pressure storage shore station, under the action of the pressure difference, flows through the gas phase manifold C2 connected to the gas transmission device, the second remote control three-way valve 21, the seventh isolation valve 27 and the fifth isolation valve 24 in sequence, and is returned to the gas phase space of the low-pressure storage tank 1 through the gas collecting pipe V2, ensuring that during the low-pressure external transmission process, the pressure in the low-pressure storage tank 1 remains unchanged or changes controllably.

[0205] In some embodiments, in step S3, the volatile gas delivery and processing includes the following steps:

[0206] When the liquid carbon dioxide is transported to the medium-pressure storage shore station or the high-pressure storage shore station (referred to as: method S3-2), in order to prevent the pressure in the low-pressure storage tank 1 from being lower than the triple point pressure of carbon dioxide during the transport process from the medium-pressure storage shore station or the high-pressure storage shore station, gas return is required. The operation of gas return includes: setting the flow path of the second remote control three-way valve 21 to "x"→"y", closing the sixth isolation valve 25, and opening the eighth isolation valve 29. At this time, the gaseous carbon dioxide from the medium-pressure storage shore station, under the action of the pressure difference, flows through the gas phase manifold C2 connected to the gas transmission facility, the second remote control three-way valve 21 ("x"→"y"), the eighth isolation valve 29 and the second pressure regulating valve 28 in sequence. After the gaseous carbon dioxide is decompressed by the second pressure regulating valve 28, the pressure drops to the allowable pressure of the low-pressure storage tank 1. The decompressed gaseous carbon dioxide is input into the gas phase space of the low-pressure storage tank 1 through the gas collecting pipe V2, ensuring that the pressure in the low-pressure storage tank 1 remains unchanged or changes controllably during the medium-pressure transport process.

[0207] In some embodiments, in step S3, the volatile gas delivery and processing includes the following steps:

[0208] In the process of injecting liquid carbon dioxide from the low-pressure storage shore station (recorded as: method S3-3), the second remote control three-way valve 21 can be set to "z"→"x", and the fifth isolation valve 24 and the seventh isolation valve 27 are opened. At this time, the gaseous carbon dioxide in the low-pressure storage tank 1 is transported back to the low-pressure storage shore station through the gas phase collecting pipe C2 through the fifth isolation valve 24 and the seventh isolation valve 27 on the bypass pipe L8 and the second remote control three-way valve 21 ("z"→"x") under the action of the pressure difference.

[0209] In some embodiments, in step S3, the volatile gas delivery and processing includes the following steps:

[0210] During the process of injecting liquid carbon dioxide from the low-pressure storage shore station, if the storage shore station does not receive the returned gaseous carbon dioxide (recorded as: method S3-4), the second remote control three-way valve 21 can be set to "z"→"y", the fifth isolation valve 24 and the sixth isolation valve 25 are opened, and the eighth isolation valve 29 is closed at the same time. When the first pressure sensor 5 detects that the pressure in the low-pressure storage tank 1 rises to the set value (the set value can be adjusted according to operational needs, which can be the design pressure of the low-pressure storage tank 1 minus 1 barg), an alarm signal is issued. At this time, the operator starts the gas compressor 23, and the excess gaseous carbon dioxide in the low-pressure storage tank 1 is extracted by the gas compressor 23 through the gas phase collecting pipe C2. The gaseous carbon dioxide pressurized by the gas compressor 23 enters the liquefaction device 26 through the second remote control three-way valve 21 ("z"→"y") and the sixth isolation valve 25. The pressurized gaseous carbon dioxide completes heat exchange with the refrigerant from the refrigeration unit 26-2 in the liquefied heat exchanger 26-1, and is converted into liquid carbon dioxide, which is then injected into the low-pressure storage tank 1 through the liquid inlet pipe L2.

[0211] In some embodiments, in step S3, the volatile gas delivery and processing includes the following steps:

[0212] In the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station (referred to as: method S3-5), since the storage pressure of the storage shore station is much higher than the pressure in the low-pressure storage tank 1, natural gas return cannot be achieved through the pressure difference. At this time, the second remote control three-way valve 21 can be set to "z" → ​​"x", the fifth isolation valve 24 is opened, and the seventh isolation valve 27 is closed. When the pressure of the low-pressure storage tank 1 monitored by the first pressure sensor 5 reaches the set value (the set value can be adjusted according to the operation needs, which can be the design pressure of the low-pressure storage tank 1 minus 1 barg), an alarm signal is issued. The operator starts the gas compressor 23, and the excess gaseous carbon dioxide in the low-pressure storage tank 1 is extracted by the gas compressor 23 through the gas collecting pipe V2, and is pressurized by the gas compressor 23 to a pressure slightly higher than the storage pressure of the storage shore station, and is returned to the medium-pressure storage shore station or the high-pressure storage shore station through the second remote-controlled three-way valve 21 ("z"→"x") and the gas collecting pipe C2 connected to the gas conveying device; the gas compressor 23 adopts frequency conversion control or multi-stage compressor inter-stage parallel operation to comprehensively adjust the outlet pressure of the gas compressor 23, that is, the pressure rise value of the gaseous carbon dioxide after passing through the gas compressor.

[0213] In some embodiments, in step S3, the volatile gas delivery and processing includes the following steps:

[0214] During the process of injecting liquid carbon dioxide from a medium-pressure storage shore station or a high-pressure storage shore station, if the storage shore station does not receive the returned gaseous carbon dioxide (recorded as: method S3-6), it is necessary to extract the excess gaseous carbon dioxide in the low-pressure storage tank 1, liquefy it, and then return it to the low-pressure storage tank 1. The specific operation process is the same as step 4 in the above-mentioned method VI of "during the process of injecting liquid carbon dioxide from a low-pressure storage shore station, if the storage shore station does not receive the returned gaseous carbon dioxide". That is, the excess gaseous carbon dioxide in the low-pressure storage tank is extracted and pressurized (or boosted) by a gas compressor, and the gaseous carbon dioxide pressurized by the gas compressor enters the liquefaction device to be converted into liquid carbon dioxide, and then injected into the low-pressure storage tank.

[0215] In some embodiments, in step S4, the self-evaporation pressure-maintaining process includes the following steps:

[0216] When the pressure of the gas phase space in the low-pressure storage tank drops to the low-pressure setting value, the pressure control valve 3 is opened to connect the self-evaporation pressure-maintaining system IV with the liquid outflow pipe L1, and part of the externally transported liquid carbon dioxide enters the self-evaporation pressure-maintaining pipe V1, and is gasified by the evaporator vaporizer 4 and then returned to the low-pressure storage tank 1 through the gas collecting pipe V2; when the pressure of the gas phase space in the low-pressure storage tank 1 rises to the high-pressure setting value, the pressure control valve 3 is closed, and the self-evaporation pressure-maintaining process ends.

[0217] In some embodiments, the self-evaporation pressure-maintaining process includes the following steps: In the step 3-1, during the process of transferring liquid carbon dioxide from the low-pressure storage tank to the storage shore station, if the storage shore station cannot provide the gas return in the step 3-1, the self-evaporation pressure-maintaining process is required, that is, the self-evaporation pressure-maintaining system IV is required to control the pressure in the low-pressure storage tank 1 to avoid the pressure being lower than the triple point pressure of carbon dioxide. Specific method: The first pressure sensor 5 is used to monitor the pressure of the gas phase space in the low-pressure storage tank 1 in real time. When the pressure drops to the low-pressure setting value, the first pressure sensor 5 sends a signal to open the pressure control valve 3, so that the self-evaporation pressure-maintaining system IV is connected to the liquid outflow pipe L1. At this time, part of the externally transferred liquid carbon dioxide enters the self-evaporation pressure-maintaining pipe V1, and this part of the liquid carbon dioxide is gasified by the evaporator gasifier 4 and then returned to the low-pressure storage tank 1 by the gas collecting pipe V2. With the continuous entry of gaseous carbon dioxide, the pressure in the low-pressure storage tank 1 gradually increases. When the pressure rises to the high-pressure setting value, the first pressure sensor 5 sends a signal again to close the pressure control valve 3, and the self-evaporation pressure-maintaining process ends.

[0218] Example 1

[0219] This embodiment takes the transfer method of the liquid cargo system of a 3,500 cubic meter low-pressure storage and transportation liquid carbon dioxide transport ship as an example to specifically illustrate the transfer method of the present invention.

[0220] The 3500 cubic meter low-pressure storage and transportation liquid carbon dioxide transport ship is equipped with a low-pressure storage tank 1 with a design pressure of 9.5 barg and a temperature of -55°C, which is used to store and transport liquid carbon dioxide (normal storage pressure is 8 barg and temperature is -52°C).

[0221] The parameters for storing liquid carbon dioxide at different pressure storage stations are as follows:

[0222] Low-pressure storage shore station, where liquid CO2 is stored at 8 barg and -53°C;

[0223] Medium pressure storage shore station, where liquid CO2 is stored at a pressure of 15 barg and a temperature of -33°C;

[0224] High-pressure storage shore station, where liquid carbon dioxide is stored at a pressure of 44 barg and a temperature of +30°C.

[0225] When a 3,000 cubic meter low-pressure liquid carbon dioxide transport ship is loading and unloading at a low-pressure storage terminal, the specific transfer method is as follows:

[0226] When unloading from a ship to a low-pressure storage shore station:

[0227] Connect the liquid phase header C1 and the gas phase header C2 to the storage shore station loading and unloading facilities and gas transportation facilities respectively;

[0228] According to the requirements of the above step S1, the states of relevant valve components are adjusted, and the delivery pump 2 is started to deliver the liquid carbon dioxide in the low-pressure storage tank 1 to the outside. The pressure of the liquid carbon dioxide entering the low-pressure external transmission pipe L3 is about 13 barg and the temperature is -50°C; the pressure is reduced to 2 bar higher than the storage pressure of the low-pressure storage shore station, that is, 10 barg, through the low-pressure pressure regulating unit 11. This pressure is used to overcome the pressure loss of the shore pipeline; the liquid carbon dioxide after pressure reduction passes through the low-pressure temperature control unit 12, and the outlet temperature is controlled to be 3°C lower than the saturation temperature of the liquid carbon dioxide at a pressure of 10 bar to offset the heat loss of the low-pressure storage shore station pipeline; the liquid carbon dioxide after pressure regulation and temperature control is delivered to the low-pressure storage shore station through the liquid phase header C1.

[0229] In this process, in order to balance the pressure drop caused by the drop in liquid level in the low-pressure storage tank 1 and prevent the pressure of the low-pressure storage tank 1 from being lower than the triple point pressure of carbon dioxide (5.2 barg, such as Figure 8 As shown), a part of the gaseous carbon dioxide needs to be supplemented by the low-pressure storage shore station through the gas phase manifold C2. The specific operation is as described in the above method S3-1. If the low-pressure storage shore station cannot provide the supplement of gaseous carbon dioxide, there is no need to connect the gas phase manifold C2. At this time, it is necessary to use the self-evaporation pressure maintenance system IV to control the pressure in the low-pressure storage tank 1. The specific operation is: during the unloading process, when the first pressure sensor 5 detects that the pressure of the low-pressure storage tank 1 drops to 6 barg, the pressure control valve 3 is opened, and part of the externally transmitted liquid carbon dioxide enters the evaporator gasifier 4 through the opened pressure control valve 3. The gasified carbon dioxide returns to the low-pressure storage tank 1 through the gas collection pipe V2, which plays a role in controlling the pressure in the low-pressure storage tank 1. When the pressure in the low-pressure storage tank 1 rises to 8 barg, the first pressure sensor 5 sends a signal to close the pressure control valve 3, and the self-evaporation pressure maintenance process ends.

[0230] When loading cargo from a low pressure storage shore station to a ship:

[0231] Connect the liquid phase header C1 and the gas phase header C2 to the low-pressure storage shore station loading and unloading facilities and gas transportation facilities respectively;

[0232] According to the requirements of the above method S2-1, the states of relevant valve components are adjusted. The liquid carbon dioxide from the low-pressure storage shore station is pressurized by the onshore facilities and then enters the ship's pipeline through the liquid phase header C1. At this time, the pressure of the liquid carbon dioxide is about 10 barg and the temperature is -50°C. The pressure is controlled by the first pressure control valve 3 to be about 0.5 bar higher than the pressure of the low-pressure storage tank 1 to overcome the pressure drop loss of the ship's pipeline, that is, 8.5 barg, and is injected into the low-pressure storage tank 1 through the liquid inlet pipe L2.

[0233] In this process, in order to control the pressure rise caused by the rise of the liquid level in the low-pressure storage tank 1 and prevent the pressure of the low-pressure storage tank 1 from being higher than the design pressure (9.5 barg) of the low-pressure storage tank 1, it is necessary to return a portion of the excess gaseous carbon dioxide in the low-pressure storage tank 1 to the storage shore station through the gas phase header C2, and the specific operation is as described in method S3-3. If the storage shore station does not receive the return of gaseous carbon dioxide, it is not necessary to connect the gas phase header C2, and the specific operation is as described in method S3-4.

[0234] When a 3,000 cubic meter low-pressure liquid carbon dioxide carrier is loading and unloading at a medium-pressure storage terminal, the specific transfer (or transfer) method is as follows:

[0235] When unloading from a ship to a medium pressure storage station:

[0236] Connect the liquid phase header C1 and the gas phase header C2 to the medium pressure storage shore station loading and unloading facilities and gas transmission facilities respectively;

[0237] According to the requirements of the above method S1-2, the states of the relevant valves are adjusted, and the delivery pump 2 is started to deliver the liquid carbon dioxide in the low-pressure storage tank 1 to the outside. The delivered liquid carbon dioxide is pressurized to 18 barg by the medium-pressure booster pump 7, which is 3 bar higher than the storage pressure of the medium-pressure storage shore station, and is used to overcome the pressure loss of the shore pipeline. The temperature of the pressurized liquid carbon dioxide is increased to -35°C, slightly lower than the storage temperature of the medium-pressure storage shore station -33°C, by the medium-pressure heating device 8, to offset the heat loss of the medium-pressure storage shore station pipeline; the pressurized and heated liquid carbon dioxide is delivered to the medium-pressure storage shore station through the liquid phase header C1.

[0238] During this process, in order to balance the pressure drop caused by the drop in liquid level in the low-pressure storage tank 1 and prevent the pressure of the low-pressure storage tank 1 from being lower than the triple point pressure of carbon dioxide (5.2 barg), it is necessary to supplement a portion of the gaseous carbon dioxide from the storage shore station through the gas phase header C2. The specific operation is as described in method S3-2. If the medium-pressure storage shore station cannot provide gaseous carbon dioxide supplementation, there is no need to connect the gas phase header C2. At this time, it is necessary to use the self-evaporation pressure maintenance system IV to control the pressure in the low-pressure storage tank 1. The specific operation is as described in step S4 above, which is the same as the self-evaporation pressure maintenance operation when transporting to the low-pressure storage shore station.

[0239] When loading cargo from a medium pressure storage shore station to a ship:

[0240] Connect the liquid phase header C1 and the gas phase header C2 to the medium pressure storage shore station loading and unloading facilities and gas transmission facilities respectively;

[0241] According to the requirements of the above method S2-2, the states of relevant valve components are adjusted. The liquid carbon dioxide from the medium-pressure storage shore station is pressurized by the onshore facilities and then enters the ship's pipeline through the liquid phase header C1. At this time, the pressure of the liquid carbon dioxide is about 20 barg and the temperature is -35°C. The pressure is controlled by the pressure reducing valve 17 to be about 0.5 bar higher than the pressure of the low-pressure storage tank 1 to overcome the pressure drop loss of the ship's pipeline, that is, 8.5 barg. The decompressed liquid carbon dioxide is further cooled to -53°C by the desuperheating heat exchanger 18 and injected into the low-pressure storage tank 1 through the liquid inlet pipe L2.

[0242] In this process, in order to control the pressure rise caused by the rise of the liquid level in the low-pressure storage tank 1 and avoid the pressure of the low-pressure storage tank 1 being higher than the design pressure (9.5 barg) of the low-pressure storage tank 1, it is necessary to return a portion of the excess gaseous carbon dioxide in the low-pressure storage tank 1 to the medium-pressure storage shore station through the gas phase header C2. The specific operation is as described in method S3-5. When the first pressure sensor 5 detects that the pressure of the low-pressure storage tank 1 rises to 9 barg, an alarm signal is triggered, and the operator starts the gas compressor 23 to pressurize the excess volatile gas in the low-pressure storage tank 1 to a storage pressure slightly higher than the medium-pressure storage shore station, that is, 16 bar, through the gas compressor 23. The pressurized gaseous carbon dioxide is returned to the medium-pressure storage shore station through the gas phase header C2. If the storage shore station does not receive the return of gaseous carbon dioxide, there is no need to connect the gas phase header C2. The specific operation is as described in method S3-6. The pressurized gaseous carbon dioxide is liquefied by the liquefaction device 26 and returned to the cabin.

[0243] When a 3,000 cubic meter low-pressure liquid carbon dioxide carrier is loading and unloading at a high-pressure storage terminal, the specific transfer method is as follows:

[0244] When unloading from a ship to a high pressure storage shore station:

[0245] Connect the high-pressure header C3 and the gas phase header C2 to the high-pressure storage shore station loading and unloading facilities and gas transmission facilities respectively;

[0246] According to the requirements of the above method S1-3, the states of the relevant valves are adjusted, and the delivery pump 2 is started to deliver the liquid carbon dioxide in the low-pressure storage tank 1 to the outside. The delivered liquid carbon dioxide is pressurized to 48 barg by the high-pressure booster pump 15, which is 3 bar higher than the storage pressure of the high-pressure storage shore station, and is used to overcome the pressure loss of the shore pipeline. The temperature of the pressurized liquid carbon dioxide is increased to +27°C by the high-pressure heating device 16, which is slightly lower than the storage temperature of the high-pressure storage shore station +30°C, to offset the heat loss of the storage shore station pipeline; the pressurized and heated liquid carbon dioxide is delivered to the high-pressure storage shore station through the high-pressure header C3.

[0247] During this process, in order to balance the pressure drop caused by the drop in liquid level in the low-pressure storage tank 1 and prevent the pressure of the low-pressure storage tank 1 from being lower than the triple point pressure of carbon dioxide (5.2 barg), it is necessary to supplement a portion of the gaseous carbon dioxide from the storage shore station through the gas phase header C2. The specific operation is as described in method S3-2. If the storage shore station cannot provide the supplement of gaseous carbon dioxide, there is no need to connect the gas phase header C2. At this time, it is necessary to use the self-evaporation pressure maintenance system IV to control the pressure in the low-pressure storage tank 1. The specific operation is as described in the above step S4, which is the same as the self-evaporation pressure maintenance operation when transporting to the low-pressure storage shore station.

[0248] When loading cargo from a high pressure storage shore station to a ship:

[0249] Connect the liquid phase header C1 and the gas phase header C2 to the storage shore station loading and unloading facilities and gas transportation facilities respectively;

[0250] According to the requirements of the above method S3-2, the state of the relevant valves is adjusted. The liquid carbon dioxide from the high-pressure storage shore station is pressurized by the shore facilities and enters the ship's pipeline through the liquid phase header C1. At this time, the pressure of the liquid carbon dioxide is about 46barg and the temperature is +32℃; the pressure is controlled by the pressure reducing valve 17 to be about 0.5bar higher than the pressure of the low-pressure storage tank 1, which is used to overcome the pressure drop loss of the ship's pipeline, that is, 8.5barg. Due to the pressure reduction effect, the temperature of the liquid carbon dioxide will also decrease accordingly, and the decompressed liquid carbon dioxide will be further cooled to -53℃ through the desuperheating heat exchanger 18, and injected into the low-pressure storage tank 1 through the liquid inlet pipe L2.

[0251] In this process, in order to control the pressure rise caused by the rise of the liquid level in the low-pressure storage tank 1 and prevent the pressure of the low-pressure storage tank 1 from being higher than the design pressure (9.5 barg) of the low-pressure storage tank 1, it is necessary to return a portion of the excess gaseous carbon dioxide in the low-pressure storage tank 1 to the storage shore station through the gas phase header C2, and the specific operation is as described in method S3-3. If the storage shore station does not receive the return of gaseous carbon dioxide, it is not necessary to connect the gas phase header C2, and the specific operation is as described in method S3-4.

[0252] In order to control the pressure rise in the low-pressure storage tank 1 caused by the rising liquid level and avoid the pressure in the low-pressure storage tank 1 being higher than the design pressure (9.5 barg) of the low-pressure storage tank 1, it is necessary to backfeed a part of the excessive gaseous carbon dioxide in the low-pressure storage tank 1 to the storage shore station through the gas header C2. The specific operation is as described in method S3-5. When the first pressure sensor 5 monitors that the pressure in the low-pressure storage tank 1 rises to 9 barg, an alarm signal is triggered, and the operator starts the gas compressor 23 to pressurize the excessive volatile gas in the low-pressure storage tank 1 to slightly higher than the storage pressure of the medium-pressure storage shore station, that is, 45 bar. The pressurized gaseous carbon dioxide is backfed to the medium-pressure storage shore station through the gas header C2. If the storage shore station does not receive the backfeed of gaseous carbon dioxide, there is no need to connect the gas header C2. The specific operation is as described in method S3-6. The pressurized gaseous carbon dioxide is liquefied by the liquefaction device 26 and then returned to the cabin.

[0253] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that; it is still possible to modify the specific implementation manners of the invention or make equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A liquid cargo system for a low-pressure storage and transportation vessel of liquid carbon dioxide, characterized in that: The liquid cargo system includes a low-pressure storage tank, a delivery pump, an external delivery system, a self-evaporation pressure-maintaining system, an injection system, a volatile gas delivery and treatment system, a liquid phase header, a high-pressure header, a gas phase header, a gas header, a liquid inlet pipe and a liquid outlet pipe; wherein, The low-pressure storage tank is used to store liquid carbon dioxide at low pressure; The delivery pump is connected to the liquid outflow pipe and is used to deliver the liquid carbon dioxide in the low-pressure storage tank to the outside; The external transmission system includes at least one of a low-pressure external transmission system, a medium-pressure external transmission system and a high-pressure external transmission system, and its input end is connected to the liquid outflow pipe, and is used to transport liquid carbon dioxide to storage shore stations with different storage pressures; The input end of the self-evaporation pressure-maintaining system is connected to the liquid outflow pipe, and the output end is connected to the gas collecting pipe, so as to control the pressure in the low-pressure storage tank when the liquid carbon dioxide is transported out; The input end of the injection system is connected to the liquid phase header, and the output end is connected to the liquid inlet pipe, so as to inject the liquid carbon dioxide in the storage shore station into the low-pressure storage tank; the injection system includes at least one of a low-pressure injection system and a medium / high-pressure injection system; The output end of the volatile gas delivery and treatment system is connected to the liquid inlet pipe and the gas collecting pipe respectively; The liquid phase header is connected to a storage shore station for receiving or outputting liquid carbon dioxide; The gas phase header is used to receive or output gaseous carbon dioxide; The storage shore station includes at least one of a low-pressure storage shore station, a medium-pressure storage shore station and a high-pressure storage shore station.

2. The liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship according to claim 1 is characterized in that: The low-pressure external transmission system, the medium-pressure external transmission system and the high-pressure external transmission system are arranged in parallel, and the output ends of the low-pressure external transmission system and the medium-pressure external transmission system are respectively connected to the liquid phase header; the output end of the high-pressure external transmission system is connected to the high-pressure header; or / and The medium / high pressure injection system and the low pressure injection system are installed in parallel in the injection system; or / and The liquid phase header is connected to the storage shore station by connecting the loading / unloading facilities; the gas phase header is connected to the gas transmission facilities and connected to the storage shore station through the gas transmission facilities; or / and The input end of the liquid inlet pipe is connected to the output end of the injection system, and the opening of the output end of the liquid inlet pipe is arranged in the low-pressure storage tank; the input end of the liquid inlet pipe is also connected to the liquefied return pipe of the volatile gas transportation and treatment system; or / and The opening of the gas collecting pipe communicating with the low-pressure storage tank is arranged at the top of the low-pressure storage tank; or / and The low-pressure storage tank adopts a C-type storage tank; in the liquid cargo system, the number of the low-pressure storage tank is at least one; or / and The delivery pump is installed inside the low-pressure storage tank, and the outlet of the delivery pump is connected to the liquid outflow pipe.

3. The liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship according to claim 1 or 2, characterized in that: The low-pressure external transmission system comprises a second isolation valve, a low-pressure pressure regulating unit, a low-pressure temperature control unit and a second one-way valve; wherein the second isolation valve is arranged on the low-pressure external transmission pipeline of the low-pressure external transmission system to control the on and off of the low-pressure external transmission pipeline; the low-pressure pressure regulating unit is used to control the pressure of the externally transmitted liquid carbon dioxide in the low-pressure external transmission system; the low-pressure temperature control unit is used to control the temperature of the externally transmitted liquid carbon dioxide in the low-pressure external transmission system, and the outlet of the second one-way valve is connected to the liquid phase manifold to prevent liquid reflux; or / and The medium-pressure external transmission system comprises a first isolation valve, a medium-pressure booster pump, a medium-pressure temperature increasing device and a first non-return valve; wherein the first isolation valve is arranged on the medium-pressure external transmission pipe of the medium-pressure external transmission system to control the opening and closing of the medium-pressure external transmission pipe; the medium-pressure booster pump is used to pressurize the liquid carbon dioxide from the delivery pump; the medium-pressure temperature increasing device is used to increase the temperature of the pressurized liquid carbon dioxide; the outlet of the first non-return valve is connected to the liquid phase header; or / and The high-pressure external transmission system includes a third isolation valve, a high-pressure booster pump and a high-pressure temperature increasing device; wherein the third isolation valve is arranged on the high-pressure external transmission pipe of the high-pressure external transmission system to control the opening and closing of the high-pressure external transmission pipe; the high-pressure booster pump is used to increase the pressure of the liquid carbon dioxide from the delivery pump; the high-pressure temperature increasing device is used to increase the temperature of the pressurized liquid carbon dioxide, and its outlet is connected to the high-pressure header; or / and The input ends of the medium / high pressure injection system and the low pressure injection system are connected to the liquid phase header through a first remote control three-way valve, and the output ends are connected to the liquid inlet pipe; wherein the first remote control three-way valve has three interfaces "1", "2" and "3", wherein interface "1" is connected to the liquid phase header; interface "2" is connected to the low pressure injection system; interface "3" is connected to the medium / high pressure injection system; or / and The low-pressure injection system comprises a first pressure regulating valve; the input end of the first pressure regulating valve is connected to the interface "2" of the first remote control three-way valve, and the output end is connected to the liquid inlet pipe, so as to control the pressure of the liquid carbon dioxide injected into the low-pressure injection system within a set range; optionally, the first pressure regulating valve comprises a diaphragm pressure regulating valve, a spring piston pressure regulating valve or a bellows pressure regulating valve; or / and The medium / high pressure injection system includes a pressure reducing valve, a temperature reducing heat exchanger and a refrigeration unit; the input end of the medium / high pressure injection system is connected to the interface "3" of the first remote control three-way valve, and the output end is connected to the liquid inlet pipe; the pressure reducing valve is used to reduce the pressure of the liquid carbon dioxide injected into the medium / high pressure injection system.

4. The liquid cargo system of a low-pressure liquid carbon dioxide storage and transportation ship according to claim 3 is characterized in that: In the low-pressure external transmission system, the low-pressure pressure regulating unit includes a pressure regulating valve, a controller and a second pressure sensor, wherein the second pressure sensor is installed downstream of the pressure regulating valve, and is used to monitor the fluid pressure in the low-pressure external transmission pipeline and transmit the measured value to the controller; the controller receives the pressure setting value and compares it with the actual measured pressure value, and then controls the pressure regulating valve so that the pressure of the fluid flowing through the pressure regulating valve tends to the pressure setting value; or / and In the low-pressure external transmission system, the low-pressure temperature control unit includes a low-pressure heat exchanger, a heat exchange medium source, a temperature control three-way valve and a low-pressure temperature sensor. The temperature control three-way valve has a linear adjustment capability and is connected to the system through three interfaces "a", "b" and "c"; the low-pressure temperature sensor is used to monitor the temperature of liquid carbon dioxide, and controls the flow of liquid carbon dioxide flowing through the low-pressure heat exchanger by adjusting the opening of the temperature control three-way valve, that is, the flow ratio of "ab" and "cb", thereby controlling the temperature of the mixed liquid carbon dioxide to meet the design requirements; the low-pressure heat exchanger includes a plate heat exchanger or a shell and tube heat exchanger; the heat exchange medium source controls the temperature of the heat exchange medium through a secondary heat exchange cycle to provide the low-pressure heat exchanger with a pre-cooled heat exchange medium; the heat exchange medium can be selected from ethylene glycol water or other low-freezing point liquids; or / and In the medium-pressure transmission system, the medium-pressure booster pump comprises a centrifugal pump or a positive displacement pump; or / and In the medium-pressure external transmission system, the medium-pressure temperature increasing device includes a medium-pressure heater, a first temperature control valve and a medium-pressure temperature sensor; wherein the medium-pressure temperature sensor is used to monitor the temperature of the pressurized liquid carbon dioxide and control the opening of the first temperature control valve; the first temperature control valve is used to adjust the amount of heat exchange medium entering the medium-pressure heater, thereby controlling the temperature of the liquid carbon dioxide passing through the medium-pressure heat exchanger; or / and In the high-pressure external transmission system, the high-pressure temperature increasing device includes a high-pressure heater, a second temperature control valve and a high-pressure temperature sensor; wherein the high-pressure temperature sensor is installed at the outlet of the high-pressure heater to monitor the temperature of the pressurized liquid carbon dioxide and control the opening of the second temperature control valve; the second temperature control valve is used to adjust the amount of heat exchange medium entering the high-pressure heater, thereby controlling the temperature of the liquid carbon dioxide passing through the high-pressure heat exchanger; or / and In the high-pressure transmission system, the high-pressure booster pump includes a centrifugal pump or a positive displacement pump; or / and In the medium / high pressure injection system, the pressure reducing valve comprises a spring type or a piston type; or / and In the medium / high pressure injection system, the desuperheating heat exchanger includes a plate-type desuperheating heat exchanger, a shell and tube-type desuperheating heat exchanger or a printed circuit board-type desuperheating heat exchanger.

5. The liquid cargo system for a low-pressure storage and transportation vessel of liquid carbon dioxide according to claim 4, characterized in that: In the medium-pressure external transmission system, the first temperature control valve of the medium-pressure temperature increasing device includes a pneumatic temperature control valve, an electric temperature control valve or a hydraulically driven temperature control valve, and its opening is controlled by the medium-pressure temperature sensor; or In the medium-pressure external transmission system, the medium-pressure heater of the medium-pressure temperature increasing device includes a plate heater or a shell and tube heater; or In the medium-pressure external transmission system, the heat exchange medium includes any one of seawater, fresh water, steam, hot oil and ethylene glycol water.

6. The liquid cargo system for a low-pressure storage and transportation vessel of liquid carbon dioxide according to claim 1, characterized in that: The self-evaporation pressure-maintaining system comprises a pressure control valve, an evaporator and a first pressure sensor; wherein the opening and closing of the pressure control valve is controlled by the first pressure sensor; the first pressure sensor is installed at the top of the low-pressure storage tank and is used to monitor the pressure of the gas phase space at the top of the low-pressure storage tank; the evaporator is used to evaporate liquid carbon dioxide into gaseous carbon dioxide and return it to the low-pressure storage tank through the gas collecting pipe; or / and The volatile gas transportation and processing system includes a second remote control three-way valve, a gas compressor, a liquefaction device, a second pressure regulating valve, a liquefied tank return pipe and a gas return pipe; wherein, the second remote control three-way valve is used to control the flow direction of the volatile gas, and has three interfaces "x", "y" and "z", wherein the interface "x" is connected to the gas phase manifold; the interface "y" is respectively connected to the liquefied tank return pipe and the gas return pipe; and the interface "z" is connected to the outlet of the gas compressor.

7. The liquid cargo system for a low-pressure storage and transportation vessel of liquid carbon dioxide according to claim 6, characterized in that: In the self-evaporation pressure-maintaining system, the evaporator gasifier includes one of a plate-type evaporator gasifier and a shell-and-tube-type evaporator gasifier, and its heat source includes electric energy, steam or hot oil; In the self-evaporation pressure-maintaining system, the pressure control valve includes a pneumatic pressure control valve, an electric pressure control valve or a hydraulic pressure control valve; or / and In the volatile gas transportation and treatment system, the air inlet side of the gas compressor is connected to the gas collecting pipe through the fifth isolation valve, and its outlet is connected to the interface "z" of the second remote control three-way valve; the volatile gas compressed by the gas compressor can be returned to the receiving device of the storage shore station through the second remote control three-way valve "z"→"x" through the gas phase collecting pipe, or connected to the liquefaction return pipe through the second remote control three-way valve "z"→"y", and returned to the low-pressure storage tank after liquefaction by the liquefaction device; or / and In the volatile gas delivery and treatment system, the inlet and outlet of the gas compressor are further provided with a bypass pipe and a seventh isolation valve for bypassing the gas compressor to achieve the natural flow of gaseous carbon dioxide; or / and In the volatile gas delivery and treatment system, a sixth isolation valve is provided on the liquefied return tank pipe; a liquefaction device is installed downstream of the sixth isolation valve; the liquefaction device includes a liquefaction heat exchanger and a refrigeration unit; wherein the liquefaction heat exchanger is used to cool and liquefy the compressed gaseous carbon dioxide; the refrigeration unit is used to provide refrigerant for the liquefaction heat exchanger; or / and In the volatile gas transportation and treatment system, an eighth isolation valve and a second pressure regulating valve are provided on the gas return pipe; wherein the second pressure regulating valve regulates the pressure of the gaseous carbon dioxide from the storage shore station.

8. A method for transferring a low-pressure liquid carbon dioxide storage and transportation ship, characterized in that: The liquid cargo system of the low-pressure liquid carbon dioxide storage and transportation ship according to any one of claims 1 to 7 is used for transfer, and the transfer method comprises the following steps: (1) The process of transferring liquid carbon dioxide to a storage station includes the following steps: (11) Connect the liquid phase header / high-pressure header and the gas phase header to the unloading facilities and gas transmission facilities of the storage shore station respectively, select an external transmission system that matches the storage pressure of the storage shore station, and connect the external transmission system to the liquid outflow pipe; (12) The liquid carbon dioxide in the low-pressure storage tank is output through a delivery pump and transported to a storage shore station through an external transmission system; (2) Injecting liquid carbon dioxide into a low-pressure storage tank from a storage shore station includes the following steps: (21) connecting the liquid phase header and the gas phase header to the loading facilities and gas delivery facilities of the storage shore station respectively, and selecting the flow path of the remote control three-way valve according to the storage pressure of the storage shore station; (22) allowing liquid carbon dioxide from the storage shore station to flow through the liquid phase header and the remote control three-way valve in sequence, enter the injection system, adjust the pressure and temperature of the carbon dioxide in the injection system, and then inject it into the low-pressure storage tank; (3) The volatile gas transport and treatment includes at least one of the following steps: (31) In the process of transporting liquid carbon dioxide from a low-pressure storage tank to a storage shore station, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the gas collecting pipe is connected to the gas phase space of the storage shore station through the gas collecting pipe, and the gaseous carbon dioxide in the storage shore station is transported to the low-pressure storage tank through the gas collecting pipe under the action of the pressure difference, that is, gas return; the pressure difference is formed by the pressure difference between the storage tank of the storage shore station and the low-pressure storage tank, or by using the compressor of the storage shore station to pressurize the returned gaseous carbon dioxide (hereinafter referred to as: return gas); (32) In the process of injecting liquid carbon dioxide from the storage shore station into the low-pressure storage tank, in order to avoid the pressure of the low-pressure storage tank being higher than the design pressure of the low-pressure storage tank, it is necessary to return a portion of the excess gaseous carbon dioxide in the low-pressure storage tank to the shore station through the gas phase header; specifically, the gaseous carbon dioxide in the low-pressure storage tank is returned to the storage shore station through the gas phase header under the action of the pressure difference, that is, the gas returns to the shore; the pressure difference is formed by the pressure difference between the low-pressure storage tank and the storage tank of the storage shore station, or by using the gas compressor on the ship to pressurize the gaseous carbon dioxide (referred to as: return shore gas) delivered to the storage shore station; (33) In step (32), if the storage shore station does not receive the returned gaseous carbon dioxide, the excess gaseous carbon dioxide in the low-pressure storage tank is extracted and pressurized by a gas compressor, and the gaseous carbon dioxide pressurized by the gas compressor enters a liquefaction device to be converted into liquid carbon dioxide, and then injected into the low-pressure storage tank; (34) During the process of transferring liquid carbon dioxide from the low-pressure storage tank to the storage shore station, if the pressure of the low-pressure storage tank increases, in order to prevent the pressure of the low-pressure storage tank from being higher than the design pressure of the low-pressure storage tank, the operation of step (32) is adopted; that is, the gaseous carbon dioxide in the low-pressure storage tank is returned to the storage shore station through the gas phase header under the action of the pressure difference; (35) During the process of injecting liquid carbon dioxide from the storage shore station into the low-pressure storage tank, if the pressure of the low-pressure storage tank drops, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the operation of step (31) is adopted; that is, the gas collecting pipe is connected to the gas phase space of the storage shore station through the gas phase collecting pipe, and the gaseous carbon dioxide from the storage shore station is transported to the low-pressure storage tank through the gas collecting pipe under the action of the pressure difference, that is, gas return; (4) Self-evaporation pressure-maintaining treatment, comprising the following steps: When the pressure of the gas phase space in the low-pressure storage tank drops to the low-pressure setting value, the pressure control valve is opened to connect the self-evaporation pressure maintaining system with the liquid outflow pipe, and part of the externally transported liquid carbon dioxide enters the self-evaporation pressure maintaining pipe, is gasified by the evaporator gasifier, and is returned to the low-pressure storage tank through the gas collecting pipe; when the pressure of the gas phase space in the low-pressure storage tank rises to the high-pressure setting value, the pressure control valve is closed, and the self-evaporation pressure maintaining process ends.

9. The method for transferring a low-pressure liquid carbon dioxide storage and transportation ship according to claim 8, characterized in that: The transfer method comprises at least one of the following steps: (i) In step (1), the liquid carbon dioxide is transported to the low-pressure storage shore station, comprising the following steps: (11) Connecting the liquid phase header and the gas phase header to the unloading facilities and gas transmission facilities of the low-pressure storage shore station respectively, closing the first isolation valve and the third isolation valve, disconnecting the medium-pressure external transmission system and the high-pressure external transmission system; opening the second isolation valve to connect the low-pressure external transmission system to the liquid outflow pipe; (12) starting the delivery pump, outputting the liquid carbon dioxide in the low-pressure storage tank through the delivery pump, and entering the low-pressure export pipe of the low-pressure export system through the liquid outlet pipe; then adjusting the pressure and temperature of the liquid carbon dioxide through the low-pressure pressure regulating unit and the low-pressure temperature control unit of the low-pressure export system in turn; the pressure-regulated and temperature-controlled liquid carbon dioxide enters the liquid phase header through the second one-way valve, and finally transports the liquid carbon dioxide to the low-pressure storage shore station through the unloading facilities connected to the liquid phase header; (ii) In step (1), the liquid carbon dioxide is transported to the medium pressure storage station outside, comprising the following steps: (11) Connect the liquid phase header and the gas phase header to the unloading facilities and gas transmission facilities of the medium-pressure storage shore station respectively, close the second isolation valve and the third isolation valve, disconnect the low-pressure external transmission system and the high-pressure external transmission system; open the first isolation valve to connect the medium-pressure external transmission system to the liquid outflow pipe; (12) starting the delivery pump, and delivering the liquid carbon dioxide in the low-pressure storage tank through the delivery pump, and entering the medium-pressure export pipe of the medium-pressure export system through the liquid outlet pipe; then the liquid carbon dioxide is pressurized by the medium-pressure booster pump of the medium-pressure export system, and the pressurized liquid carbon dioxide is then heated by the medium-pressure heating device, so that the pressure and temperature of the liquid carbon dioxide meet the receiving requirements of the medium-pressure storage shore station; then, the pressurized and heated liquid carbon dioxide enters the liquid phase header through the first one-way valve, and finally the liquid carbon dioxide is delivered to the medium-pressure storage shore station through the unloading facilities connected to the liquid phase header; (iii) In step (1), the liquid carbon dioxide is transported to the high-pressure storage shore station, comprising the following steps: (11) Connect the high-pressure header and the gas phase header to the unloading facilities and gas transmission facilities of the high-pressure storage shore station respectively, close the first isolation valve and the second isolation valve, disconnect the low-pressure external transmission system and the medium-pressure external transmission system; open the third isolation valve to connect the high-pressure external transmission system to the liquid outflow pipe; (12) starting the delivery pump to deliver the liquid carbon dioxide in the low-pressure storage tank through the delivery pump and enter the high-pressure export pipe of the high-pressure export system through the liquid outlet pipe; then, the liquid carbon dioxide entering the high-pressure export pipe is pressurized by the high-pressure booster pump, and the pressurized liquid carbon dioxide is then heated by the high-pressure heating device, so that the pressure and temperature of the liquid carbon dioxide meet the receiving requirements of the high-pressure storage shore station; the pressurized and heated liquid carbon dioxide is delivered to the high-pressure storage shore station through the high-pressure header; (iv) In step (2), the injection of liquid carbon dioxide into the low-pressure storage tank from the low-pressure storage shore station comprises the following steps: (21) Connect the liquid phase header and the gas phase header to the loading facilities and gas delivery facilities of the storage shore station respectively, and set the flow path of the first remote control three-way valve to "1"→"2"; (22) allowing the low-pressure liquid carbon dioxide from the low-pressure storage shore station to flow through the liquid phase header and the first remote control three-way valve ("1"→"2") in sequence, then regulating the pressure of the liquid carbon dioxide through the first pressure regulating valve, and finally injecting it into the low-pressure storage tank through the liquid inlet pipe; (v) In step (2), the liquid carbon dioxide is injected into the low-pressure storage tank from the medium-pressure storage shore station or the high-pressure storage shore station, comprising the following steps: (21) connecting the liquid phase header and the gas phase header to the loading facilities and gas transmission facilities of the medium pressure storage shore station or the high pressure storage shore station respectively, and setting the flow path of the first remote control three-way valve to "1"→"3"; (22) allowing the low-pressure liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station to flow through the liquid phase header and the first remote-controlled three-way valve ("1"→"3") in sequence, decompressing the injected liquid carbon dioxide through the pressure reducing valve, and then cooling the decompressed liquid carbon dioxide through the desuperheating heat exchanger so that the liquid carbon dioxide meets the storage requirements of the low-pressure storage tank; finally, the decompressed and cooled liquid carbon dioxide is injected into the low-pressure storage tank through the liquid inlet pipe; (vi) In the step (31), in the process of transporting liquid carbon dioxide to the low-pressure storage shore station, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the gas return includes the following steps: The flow direction of the second remote-controlled three-way valve is set to "x"→"z", and the fifth isolation valve and the seventh isolation valve are opened. Under the action of the pressure difference, the gaseous carbon dioxide from the low-pressure storage shore station flows through the gas phase header, the second remote-controlled three-way valve, the seventh isolation valve and the fifth isolation valve in sequence, and is transported to the gas phase space of the low-pressure storage tank through the gas header; (vii) In the step (31), in the process of transporting liquid carbon dioxide to the medium-pressure storage shore station or the high-pressure storage shore station, in order to prevent the pressure in the low-pressure storage tank from being lower than the triple point pressure of carbon dioxide, the gas return includes the following steps: The flow path of the second remote-controlled three-way valve is set to "x"→"y", the sixth isolation valve is closed, and the eighth isolation valve is opened; the gaseous carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station flows through the gas phase header, the second remote-controlled three-way valve ("x"→"y"), the eighth isolation valve and the second pressure regulating valve in sequence under the action of the pressure difference, and the gaseous carbon dioxide after being decompressed by the second pressure regulating valve is input into the gas phase space of the low-pressure storage tank through the gas header; (viii) In the step (32), during the process of injecting liquid carbon dioxide from the low-pressure storage shore station into the low-pressure storage tank, in order to prevent the pressure of the low-pressure storage tank from being higher than the design pressure of the low-pressure storage tank, the gas return to shore includes the following steps: The flow path of the second remote-controlled three-way valve is set to "z"→"x", and the fifth isolation valve and the seventh isolation valve are opened. The excess gaseous carbon dioxide from the low-pressure storage tank flows through the gas phase header, the fifth isolation valve and the seventh isolation valve in sequence under the action of the pressure difference, and the second remote-controlled three-way valve ("z"→"x") is transported to the storage shore station through the gas phase header; (ix) In the step (32), during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the low-pressure storage tank, in order to prevent the pressure of the low-pressure storage tank from being higher than the design pressure of the low-pressure storage tank, the gas return to shore includes the following steps: The flow path of the second remote-controlled three-way valve is set to "z"→"x", the fifth isolation valve is opened, the seventh isolation valve is closed, and the gas compressor is started to extract the excess gaseous carbon dioxide in the low-pressure storage tank, which flows through the gas collecting pipe, the fifth isolation valve, the gas compressor and the second remote-controlled three-way valve ("z"→"x") in sequence. The gaseous carbon dioxide pressurized by the gas compressor is transported to the storage shore station through the gas phase collecting pipe.

10. The method for transferring a low-pressure liquid carbon dioxide storage and transportation ship according to claim 9, characterized in that: In the step (22), the pressure of the liquid carbon dioxide after pressure regulation by the first pressure regulating valve is higher than the pressure of the low-pressure storage tank and can overcome the back pressure of the liquid carbon dioxide injected into the low-pressure storage tank; or In the step (22), the pressure of the liquid carbon dioxide after being decompressed by the pressure reducing valve is higher than the pressure of the low-pressure storage tank and can overcome the back pressure of being injected into the low-pressure storage tank; or In the step (31), during the process of transferring the liquid carbon dioxide to the low-pressure storage shore station, the pressure in the low-pressure storage tank is maintained constant or changes in a controllable manner; or In the step (31), during the process of transporting the liquid carbon dioxide to the medium-pressure storage shore station or the high-pressure storage shore station, the pressure in the low-pressure storage tank remains unchanged or changes in a controllable manner; or In the step (32), during the process of injecting liquid carbon dioxide from the low-pressure storage shore station into the low-pressure storage tank, the pressure in the low-pressure storage tank is maintained constant or changes in a controllable manner; or In the step (32), during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the low-pressure storage tank, the pressure in the low-pressure storage tank is maintained unchanged or changes in a controllable manner.

Images