Liquid cargo lightering system and transferring method for medium-pressure storage and transportation liquid carbon dioxide ship

Abstract

The invention provides a liquid cargo lightering system for a medium-pressure storage and transportation liquid carbon dioxide ship and a transferring method. The liquid cargo lightering system comprises a medium-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 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 medium-pressure storage tank; the injection system is used for injecting liquid carbon dioxide of different storage pressure shore stations into the medium-pressure storage tank; the volatile gas conveying and processing system is used for conveying and processing volatile gas and controlling the pressure in the medium-pressure storage tank in the process of outwards conveying or injecting the carbon dioxide. The medium-pressure liquid carbon dioxide storage and transportation ship can be effectively compatible with high / low-pressure storage shore stations, and the compatibility and operation flexibility of the ship are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of marine engineering equipment technology, and more specifically, to a liquid cargo transshipment system and method for medium-pressure storage and transportation of liquid carbon dioxide. Background Technology

[0002] As climate and environmental issues become increasingly prominent worldwide, countries are gradually increasing their efforts and measures to address global warming, resulting in a variety of carbon dioxide emission reduction schemes. Among these, carbon dioxide capture and storage (CCS) is an important and effective measure. How to transport the captured carbon dioxide over long distances is a crucial factor in determining the success or failure of CCS projects.

[0003] The volume of liquefied carbon dioxide is approximately 1 / 600th that of the same amount of gaseous carbon dioxide. Therefore, using ships to transport liquefied carbon dioxide is the most efficient and economical method for long-distance transport of captured carbon dioxide. According to research data from the Global CCS Institute, the carbon capture and storage market is projected to grow at a rate of over 30% annually, reaching 7.6 billion tons of global carbon capture by 2050. This also means that the demand for the transportation of liquefied carbon dioxide will increase accordingly.

[0004] Medium-pressure storage technology is the mainstream development direction for liquid carbon dioxide (LCC) carriers. This involves storing liquid carbon dioxide in medium-pressure tanks at approximately -25°C and 17 barg for transport. The advantage of this technology is that the temperature and pressure of the liquid carbon dioxide during storage and transportation remain far from its triple point (the triple point of pure carbon dioxide is: pressure 5.12 bar; temperature -56.6°C), reducing the likelihood of dry ice formation and improving operational safety. The 7,500 cubic meter LCC carrier delivered by Chinese shipyards in 2024 is based on medium-pressure storage technology. Currently, the cargo system design of medium-pressure LCC carriers only allows cargo loading and unloading between storage shore stations or ships with similar or identical carbon dioxide storage pressures and temperatures. It cannot effectively accommodate storage shore stations with low or high pressure storage. Summary of the Invention

[0005] (a) Technical problems to be solved The technical problem this invention aims to solve is that the current design of the liquid cargo system for medium-pressure liquid carbon dioxide transport ships only allows cargo loading and unloading between storage shore stations or ships with the same or similar carbon dioxide storage pressure and temperature, and cannot effectively accommodate storage shore stations with low or high pressure storage.

[0006] (II) Technical Solution To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a liquid cargo barge transport system for a medium-pressure storage and transportation vessel carrying liquid carbon dioxide, comprising a medium-pressure storage tank, a transfer pump, an external transport system, a self-evaporating pressure-maintaining system, an injection system, a volatile gas transport and processing system, a liquid phase manifold, a gas phase manifold, a gas collection pipe, a liquid inlet pipe, and a liquid outlet pipe; wherein, the medium-pressure storage tank is used for medium-pressure storage of liquid carbon dioxide; the transfer pump is connected to the liquid outlet pipe for transporting the liquid carbon dioxide from the medium-pressure storage tank to the outside; the external transport system includes at least one of a low-pressure external transport system, a medium-pressure external transport system, and a high-pressure external transport system, the input end of which is connected to the liquid outlet pipe for transporting liquid carbon dioxide to storage shore stations with different storage pressures; the input end of the self-evaporating pressure-maintaining system is connected to the liquid outlet pipe. The system comprises a pipe connection, with its output end connected to the gas collection pipe, used to control the pressure inside the medium-pressure storage tank during the external transmission of liquid carbon dioxide; the injection system has its input end connected to the liquid phase manifold and its output end connected to the liquid inlet pipe, used to inject liquid carbon dioxide from shore stations with different storage pressures into the medium-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 transport and processing system is connected to the liquid inlet pipe and the gas collection pipe respectively; the liquid phase manifold is connected to the storage shore station for receiving or outputting liquid carbon dioxide; the gas phase manifold is used for receiving or outputting 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.

[0007] Furthermore, the low-pressure export system, the medium-pressure export system, and the high-pressure export system are arranged in parallel, and the output ends of the low-pressure export system, the medium-pressure export system, and the high-pressure export system are respectively connected to the liquid phase manifold; Furthermore, the medium / high pressure injection system and the low pressure injection system are installed in parallel within the injection system; Furthermore, the liquid phase manifold is connected to the storage shore station via a loading / unloading facility; the gas phase manifold is connected to a gas delivery facility and is also connected to the storage shore station via the gas delivery facility. Furthermore, 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 located inside the medium-pressure storage tank; the input end of the liquid inlet pipe is also connected to the liquefaction return pipe of the volatile gas conveying and processing system. Furthermore, the opening connecting the gas collecting pipe to the medium-pressure storage tank is located at the top of the medium-pressure storage tank; Furthermore, the medium-pressure storage tank adopts a C-type storage compartment, and the number of the medium-pressure storage tank is greater than or equal to one; Furthermore, the transfer pump is installed inside the medium-pressure storage tank, and its outlet is connected to the liquid outlet pipe.

[0008] Furthermore, the low-pressure export system includes a second isolation valve, a pressure reducing valve, a second pressure sensor, a low-pressure desuperheating device, and a second check valve; wherein, the second isolation valve, pressure reducing valve, second pressure sensor, low-pressure desuperheating device, and second check valve are installed on the low-pressure export pipeline of the low-pressure export system; the second isolation valve is used to control the opening and closing of the low-pressure export pipeline; the pressure reducing valve is used to reduce the pressure of the exported liquid carbon dioxide in the low-pressure export system to a pressure acceptable to the low-pressure storage shore station; the second pressure sensor is used to control the pressure reduction value through the pressure reducing valve, and its set value can be adjusted according to the actual input pressure required by the low-pressure storage shore station; the low-pressure desuperheating device is used to reduce the temperature of the depressurized liquid carbon dioxide to a temperature acceptable to the low-pressure storage shore station; the outlet of the second check valve is connected to the liquid phase manifold to prevent liquid backflow; the medium-pressure export system includes a first isolation valve, a first pressure regulating valve, and a first check valve. The system comprises a first isolation valve, a first pressure regulating valve, and a first check valve, all mounted on the medium-pressure export pipe of the medium-pressure export system. The first isolation valve controls the opening and closing of the medium-pressure export pipe. The first pressure regulating valve controls the pressure of the exported liquid carbon dioxide in the medium-pressure export system. The outlet of the first check valve is connected to the liquid phase manifold to prevent liquid backflow. The high-pressure export system includes a third isolation valve, a high-pressure booster pump, a high-pressure heating device, and a third check valve. The third isolation valve controls the opening and closing of the high-pressure export pipe. The high-pressure booster pump increases the pressure of the liquid carbon dioxide from the delivery pump. The high-pressure heating device increases the temperature of the pressurized liquid carbon dioxide. The outlet of the third check valve is connected to the liquid phase manifold to prevent liquid backflow. Furthermore, the low-pressure cooling device includes a low-pressure heat exchanger, a first refrigerant unit, and a low-pressure temperature sensor. The low-pressure heat exchanger, including a plate heat exchanger or a shell-and-tube heat exchanger, is used to exchange heat between the depressurized liquid carbon dioxide and the refrigerant provided by the first refrigerant unit, thereby reducing the temperature of the depressurized liquid carbon dioxide. The low-pressure temperature sensor is installed in the downstream pipeline of the low-pressure heat exchanger to monitor the temperature of the liquid carbon dioxide in the low-pressure export pipeline. The first refrigerant unit provides refrigerant to the low-pressure heat exchanger; the refrigerant is propane or propylene. Furthermore, the high-pressure heating device includes a high-pressure heater, a first 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 liquid carbon dioxide after pressurization and to control the opening of the first temperature control valve; the first temperature control valve is used to regulate 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.

[0009] Furthermore, the first temperature control valve includes a pneumatic temperature control valve, an electric temperature control valve, or a hydraulic temperature control valve, and the opening degree of the first temperature control valve is controlled by the medium-pressure temperature sensor; the high-pressure heater is a plate heater or a shell-and-tube heater; the heat exchange medium includes any one of seawater, fresh water, steam, hot oil, and ethylene glycol water.

[0010] Furthermore, the input ends of the medium / high pressure injection system and the low pressure injection system are connected to the liquid phase manifold via a first remote-controlled three-way valve, and the output ends are connected to the liquid inlet pipe. The first remote-controlled three-way valve has a first interface, a second interface, and a third interface. The first interface is connected to the liquid phase manifold; the second interface is connected to the medium / high pressure injection system; and the third interface is connected to the low pressure injection system. The low pressure injection system includes a medium-pressure booster pump and a medium-pressure heating device. The inlet of the medium-pressure booster pump is connected to the third interface of the first remote-controlled three-way valve, and the output end is connected to the medium-pressure heating device, used to boost the low pressure from the low-pressure storage shore station. The system includes a medium-pressure heating device to increase the temperature of the pressurized liquid carbon dioxide, ensuring that the pressure and temperature of the liquid carbon dioxide from the low-pressure storage shore station meet the storage requirements of the medium-pressure storage tank. The medium / high-pressure injection system includes a second pressure regulating valve and a medium-pressure cooling device. The input end of the medium / high-pressure injection system is connected to the second port of a first remote-controlled three-way valve, and the output end is connected to the liquid inlet pipe. The second pressure regulating valve is used to regulate the pressure of the liquid carbon dioxide injected into the medium / high-pressure injection system to meet the storage requirements of the medium-pressure storage tank. The medium-pressure cooling device is used to control the temperature of the input liquid carbon dioxide after pressure regulation.

[0011] Furthermore, the medium-pressure heating device includes a medium-pressure heater, a second temperature control valve, and a first medium-pressure temperature sensor; wherein, the first medium-pressure temperature sensor is installed at the outlet of the medium-pressure heater to monitor the temperature of the liquid carbon dioxide after pressurization and control the opening of the second temperature control valve; the second temperature control valve is used to regulate 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; the heat exchange medium is ethylene glycol water or other low-pour-point liquid; Furthermore, the medium-pressure desuperheating device includes a medium-pressure heat exchanger, a second refrigerant unit, a temperature-controlled three-way valve, and a second medium-pressure temperature sensor. The temperature-controlled three-way valve has linear adjustment capability; the second medium-pressure temperature sensor monitors the temperature of liquid carbon dioxide and controls the flow rate of liquid carbon dioxide through the medium-pressure heat exchanger by adjusting the opening of the temperature-controlled three-way valve, thereby controlling the temperature of the mixed liquid carbon dioxide to meet design requirements; the second refrigerant unit controls the temperature of the heat exchange medium through a secondary heat exchange cycle, providing pre-cooled refrigerant to the medium-pressure heat exchanger; the refrigerant is propane or propylene.

[0012] Furthermore, the self-evaporating pressure-maintaining system includes 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 medium-pressure storage tank to monitor the pressure of the gas phase space at the top of the medium-pressure storage tank; the evaporator is used to evaporate liquid carbon dioxide into gaseous carbon dioxide and return it to the medium-pressure storage tank through a gas collection pipe; the volatile gas transportation and processing system includes a second remote-controlled three-way valve, a gas compressor, a liquefaction device, a third pressure regulating valve, a fourth pressure regulating valve, as well as a liquefaction return pipe, a gas return to shore pipe, and a gas return pipeline; wherein the second remote-controlled three-way valve is used to control the flow direction of the volatile gas and has a fourth interface, a fifth interface, and a sixth interface, wherein the fourth interface is connected to the gas phase collection pipe; the fifth interface is connected to the liquefaction return pipe; and the sixth interface is connected to the outlet of the gas compressor; the third pressure regulating valve is used to control the pressure of gaseous carbon dioxide returning from the medium-pressure storage tank to the shore station; and the fourth pressure regulating valve is used to control the pressure of gaseous carbon dioxide returning from the shore station to the medium-pressure storage tank.

[0013] Furthermore, the gas compressor's inlet side is connected to the gas collection pipe via a sixth isolation valve, and the gas compressor's outlet is connected to the sixth port of the second remote-controlled three-way valve. The volatile gas compressed by the gas compressor can be output through the fourth port of the second remote-controlled three-way valve and returned to the receiving device of the storage shore station via the gas phase collection pipe, or connected to the liquefaction return pipe through the fifth port of the second remote-controlled three-way valve, and returned to the medium-pressure storage tank after liquefaction by the liquefaction device. Furthermore, a seventh isolation valve is provided on the liquefaction return pipe; a liquefaction device is installed downstream of the seventh 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 to the liquefaction heat exchanger; Furthermore, a third pressure regulating valve is provided on the gas return pipe. The third pressure regulating valve regulates the pressure of gaseous carbon dioxide from the medium-pressure storage tank. The gas inlet of the third pressure regulating valve is connected to the gas collecting pipe via a fourth isolation valve, and its gas outlet is connected to the gas phase collecting pipe via a fifth isolation valve. Furthermore, a fourth pressure regulating valve is installed on the gas return pipe. The fourth pressure regulating valve regulates the pressure of gaseous carbon dioxide from the shore station. The gas inlet of the fourth pressure regulating valve is connected to the gas phase manifold via the ninth isolation valve, and its gas outlet is connected to the gas collection pipe via the eighth isolation valve.

[0014] Secondly, the present invention also provides a transshipment method for a medium-pressure storage and transportation vessel carrying liquid carbon dioxide, wherein the transshipment is performed using a liquid cargo transshipment system for a medium-pressure storage and transportation vessel carrying liquid carbon dioxide according to any of the above technical solutions, and the transshipment method includes the following steps: S1. Transferring liquid carbon dioxide to the storage shore station, including the following steps: S11. Connect the liquid phase manifold and the gas phase manifold 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 outlet pipe. S12. The liquid carbon dioxide in the medium-pressure storage tank is output by a transfer pump and transported to the storage shore station through the external transmission system; S2. Injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank includes the following steps: S21. Connect the liquid phase manifold and the gas phase manifold to the loading facilities and gas conveying facilities of the storage shore station, respectively, and select the flow path of the first remote-controlled three-way valve according to the storage pressure of the storage shore station. S22. The liquid carbon dioxide from the storage shore station flows sequentially through the liquid phase manifold and the first remote-controlled three-way valve into the injection system. The pressure and temperature of the carbon dioxide in the injection system are adjusted, and then injected into the medium-pressure storage tank. S3. Volatile gas conveying and treatment, including at least one of the following steps: S31. During the process of transferring liquid carbon dioxide from the medium-pressure storage tank to the storage shore station, in order to avoid the pressure inside the medium-pressure storage tank from falling below the minimum design pressure of the tank, the gas collecting pipe is connected to the gas phase space of the storage shore station through the gas phase manifold. Under the action of pressure difference, the gaseous carbon dioxide of the storage shore station is transported to the medium-pressure storage tank through the gas manifold, that is, gas return. The pressure difference is formed by the pressure difference between the storage tank of the storage shore station and the medium-pressure storage tank, or by using the compressor of the storage shore station to pressurize the returned gaseous carbon dioxide. S32. During the process of injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank, in order to avoid the pressure of the medium-pressure storage tank from exceeding the design pressure of the medium-pressure storage tank, it is necessary to return a portion of the excess gaseous carbon dioxide in the medium-pressure storage tank to the shore station through the gas phase manifold. Specifically, the gaseous carbon dioxide in the medium-pressure storage tank is returned to the storage shore station through the gas phase manifold under the action of the pressure difference, that is, gas returns to shore. The pressure difference is formed by the pressure difference between the medium-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 delivered to the storage shore station. S33. In step S32, if the storage shore station does not receive the returned gaseous carbon dioxide, the excess gaseous carbon dioxide in the medium-pressure storage tank is extracted and pressurized by a gas compressor. 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 medium-pressure storage tank. S34. During the process of transferring liquid carbon dioxide from the medium-pressure storage tank to the storage shore station, if the pressure of the medium-pressure storage tank increases, in order to avoid the pressure of the medium-pressure storage tank from exceeding the design pressure of the medium-pressure storage tank, the operation in step S32 is adopted; that is, the gaseous carbon dioxide in the medium-pressure storage tank is returned to the storage shore station through the gas phase manifold under the action of pressure difference. S35. During the process of injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank, if the pressure of the medium-pressure storage tank drops, in order to avoid the pressure in the medium-pressure storage tank falling below the minimum design pressure of the tank, the operation in step S31 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 of the storage shore station is transported to the medium-pressure storage tank through the gas collecting pipe under the action of pressure difference, that is, gas return transport. S4. Self-evaporation and pressure holding treatment, including the following steps: When the pressure in the gas phase space inside the medium-pressure storage tank drops to the low-pressure set value, the pressure control valve is opened to connect the self-evaporation pressure-maintaining system with the liquid outlet pipe. Some of the exported liquid carbon dioxide enters the self-evaporation pressure-maintaining pipe, is vaporized by the evaporator, and is then returned to the medium-pressure storage tank through the gas collection pipe. When the pressure in the gas phase space inside the medium-pressure storage tank rises to the high-pressure set value, the pressure control valve is closed, and the self-evaporation pressure-maintaining process ends.

[0015] In this invention, step S3 aims to prevent the pressure of the medium-pressure storage tank from falling below its minimum design pressure or exceeding its maximum designed operating pressure (pressure setpoint). This consideration should be taken into account both when transferring and injecting carbon dioxide. Specifically, when transferring carbon dioxide, a pressure drop in the medium-pressure storage tank is a common occurrence, while a pressure increase is an occasional occurrence. Similarly, when injecting carbon dioxide, a pressure increase in the medium-pressure storage tank is a common occurrence, while a pressure decrease is an occasional occurrence.

[0016] As an optional implementation, step S1, transferring liquid carbon dioxide to the low-pressure storage shore station, includes the following steps: S11. Connect the liquid phase manifold and the gas phase manifold to the unloading facilities and gas transmission facilities of the low-pressure storage shore station, respectively; close the first isolation valve and the third isolation valve; disconnect the medium-pressure external transmission system and the high-pressure external transmission system; open the second isolation valve to connect the low-pressure external transmission system to the liquid outlet pipe. S12. Start the transfer pump to output the liquid carbon dioxide in the medium-pressure storage tank through the transfer pump and enter the low-pressure export pipe of the low-pressure export system through the liquid outlet pipe; then, the pressure and temperature of the liquid carbon dioxide are adjusted by the pressure reducing valve and the low-pressure desuperheating device of the low-pressure export system in sequence; the liquid carbon dioxide, after pressure adjustment and temperature control, enters the liquid phase manifold through the second one-way valve, and finally, the liquid carbon dioxide is transported to the low-pressure storage shore station through the unloading facility connected to the liquid phase manifold. As an optional implementation, step S1, transferring liquid carbon dioxide to the medium-pressure storage shore station, includes the following steps: S11. Connect the liquid phase manifold and the gas phase manifold 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 to 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 outlet pipe. S12. Start the transfer pump to output the liquid carbon dioxide in the medium-pressure storage tank through the transfer pump and enter the medium-pressure export pipe of the medium-pressure export system through the liquid outlet pipe; then, the pressure of the liquid carbon dioxide is regulated by the first pressure regulating valve. The pressure and temperature of the regulated liquid carbon dioxide meet the receiving requirements of the medium-pressure storage shore station; it enters the liquid phase manifold through the first one-way valve, and finally, the liquid carbon dioxide is transported to the medium-pressure storage shore station through the unloading facility connected to the liquid phase manifold.

[0017] As an optional implementation, step S1, transferring liquid carbon dioxide to the high-pressure storage shore station, includes the following steps: S11. Connect the liquid phase manifold and the gas phase manifold 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 to 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 outlet pipe. S12. Start the transfer pump to output the liquid carbon dioxide in the medium-pressure storage tank through the transfer 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 manifold.

[0018] As an optional implementation, step S12, injecting liquid carbon dioxide from the low-pressure storage shore station into the medium-pressure storage tank, includes the following steps: S21. Connect the liquid phase manifold and the gas phase manifold to the loading facilities and gas transmission facilities of the storage shore station respectively, and set the flow path of the remote control three-way valve to the first interface → the third interface. S22. Low-pressure liquid carbon dioxide from the low-pressure storage shore station flows sequentially through the liquid phase manifold and the remote-controlled three-way valve (first port → third port), and is then pressurized by a medium-pressure booster pump. The pressurized liquid carbon dioxide is then heated by a medium-pressure heating device, so that the pressure and temperature of the liquid carbon dioxide meet the receiving requirements of the medium-pressure storage tank. Finally, it is injected into the medium-pressure storage tank through the liquid inlet pipe.

[0019] As an optional implementation, in step S22, the pressure of the liquid carbon dioxide after being pressurized by the medium-pressure booster pump is higher than (for example, slightly higher than) the pressure of the medium-pressure storage tank, and can overcome the back pressure injected into the medium-pressure storage tank; the pressurized liquid carbon dioxide passes through the medium-pressure heating device, and the temperature meets the storage requirements of the medium-pressure storage tank.

[0020] As an optional implementation, step S2, injecting liquid carbon dioxide into the medium-pressure storage tank from a medium-pressure storage shore station or a high-pressure storage shore station, includes the following steps: S21. Connect the liquid phase manifold and the gas phase manifold to the loading facilities and gas transmission facilities of the medium-pressure storage shore station or the high-pressure storage shore station, respectively, and set the flow path of the remote control three-way valve to the first interface → the second interface. S22. Low-pressure liquid carbon dioxide from the medium-pressure or high-pressure storage shore station flows sequentially through the liquid phase manifold and the remote-controlled three-way valve (first port → second port). The pressure of the injected liquid carbon dioxide is regulated by the second pressure regulating valve, and then the liquid carbon dioxide after pressure reduction is further cooled by the medium-pressure de-cooling device, so that the pressure and temperature of the liquid carbon dioxide meet the storage requirements of the medium-pressure storage tank. Finally, the liquid carbon dioxide after pressure reduction and de-cooling is injected into the medium-pressure storage tank through the liquid inlet pipe.

[0021] As an optional implementation, in step S22, the pressure of the liquid carbon dioxide after being depressurized by the pressure reducing valve is higher than (for example, slightly higher than) the pressure of the medium-pressure storage tank, and can overcome the back pressure injected into the medium-pressure storage tank; the depressurized liquid carbon dioxide passes through the medium-pressure desuperheating device, and the temperature meets the storage requirements of the medium-pressure storage tank.

[0022] In this invention, during the process of outputting liquid carbon dioxide from the medium-pressure storage tank, the liquid level inside the tank continuously changes, the gas phase space expands, and the pressure in the gas phase space changes accordingly. For safety reasons, the pressure inside the medium-pressure storage tank should always be higher than the minimum design pressure of the tank; otherwise, the temperature of the liquid carbon dioxide inside the tank will drop below the minimum temperature that the tank material can withstand, endangering the safety of the tank. To prevent the pressure inside the medium-pressure storage tank from falling below the minimum design pressure, it is necessary to transport and process the gaseous carbon dioxide inside the tank.

[0023] Similarly, during the injection of liquid carbon dioxide into the medium-pressure storage tank, the liquid level inside the tank constantly changes, the gas phase space is compressed, and the pressure in the gas phase space changes accordingly. To prevent the pressure inside the medium-pressure storage tank from exceeding its design pressure, the gaseous carbon dioxide inside the tank needs to be transported and treated. This invention employs different methods for transporting and treating volatile gases to address the different output and injection processes of liquid carbon dioxide.

[0024] For example, during the process of transferring liquid carbon dioxide to a low-pressure, medium-pressure, or high-pressure storage shore station, the liquid level in the medium-pressure storage tank continuously decreases as the liquid carbon dioxide is transferred, the volume of the gas phase space increases, and the pressure decreases accordingly. To prevent the pressure in the medium-pressure storage tank from falling below the minimum design pressure of the tank during the transfer to the storage shore station, which would cause the temperature of the liquid carbon dioxide in the medium-pressure storage tank to fall below the design temperature of the tank material, a certain amount of gaseous carbon dioxide needs to be introduced from the outside; that is, gas backflow is required.

[0025] As an optional implementation, in step S31, during the process of transferring liquid carbon dioxide to the low-pressure storage shore station (i.e., during the low-pressure external transfer process), in order to avoid the pressure inside the medium-pressure storage tank falling below the minimum design pressure of the storage tank, the gas return transfer includes the following steps: Typically, the pressure of carbon dioxide gas in the low-pressure storage shore station tank is lower than the pressure in the medium-pressure storage tank on the ship, therefore, gas return cannot be achieved through pressure difference. If the low-pressure storage shore station has a carbon dioxide gas pressurization and return function, such as being equipped with a booster compressor, then by opening the eighth and ninth isolation valves and simultaneously closing other isolation valves in the volatile gas transport and treatment system, the carbon dioxide, after being pressurized by the shore station's carbon dioxide gas pressurization facility, flows sequentially through the gas phase manifold, the ninth isolation valve, the fourth pressure regulating valve, and the eighth isolation valve. The gaseous carbon dioxide, after being depressurized by the fourth pressure regulating valve, is input into the gas phase space of the medium-pressure storage tank through the gas collection pipe. If the low-pressure storage shore station does not have a carbon dioxide gas pressurization and return function, then the self-evaporating pressure-maintaining system needs to be used to control the pressure in the medium-pressure storage tank, as described in step S4.

[0026] As an optional implementation, during the process of transferring liquid carbon dioxide to the low-pressure storage shore station, the pressure inside the medium-pressure storage tank remains constant or changes in a controllable manner.

[0027] As an optional implementation, in step S31, during the process of transferring liquid carbon dioxide from the medium-pressure storage tank to the medium-pressure storage shore station or the high-pressure storage shore station, in order to avoid the pressure inside the medium-pressure storage tank falling below the minimum design pressure of the tank, it is necessary for the storage shore station to replenish CO2 to the medium-pressure storage tank. At this time, the pressure of the medium-pressure storage shore station or the high-pressure storage shore station exceeds the medium-pressure storage pressure; the gas return includes the following steps: With the eighth and ninth isolation valves opened and other isolation valves in the volatile gas transport and treatment system closed, gaseous carbon dioxide from the medium-pressure or high-pressure storage shore station flows sequentially through the gas phase manifold, the ninth isolation valve, the fourth pressure regulating valve, and the eighth isolation valve under the action of pressure difference. After being depressurized by the fourth pressure regulating valve, the gaseous carbon dioxide is input into the gas phase space of the medium-pressure storage tank through the gas collection pipe.

[0028] In this invention, after the gaseous carbon dioxide is depressurized by the fourth pressure regulating valve, the pressure drops to the allowable pressure of the medium-pressure storage tank.

[0029] As an optional implementation, during the process of transferring liquid carbon dioxide to a medium-pressure or high-pressure storage shore station, the pressure inside the medium-pressure storage tank remains constant or changes in a controllable manner.

[0030] As an optional implementation, in step S32, during the process of injecting liquid carbon dioxide from the low-pressure storage shore station to the medium-pressure storage tank, if the pressure of the medium-pressure storage tank is higher than the pressure set value of the medium-pressure storage tank, the gaseous carbon dioxide in the medium-pressure storage tank will be returned to the storage shore station through the gas phase manifold under the action of the pressure difference.

[0031] As an optional implementation, in step S32, during the process of injecting liquid carbon dioxide from the low-pressure storage shore station into the medium-pressure storage tank, if the pressure of the medium-pressure storage tank is higher than the pressure set value of the medium-pressure storage tank, the fourth isolation valve and the fifth isolation valve are opened, while other isolation valves in the volatile gas transportation and treatment system are closed. The excess gaseous carbon dioxide from the medium-pressure storage tank flows sequentially through the gas collecting pipe, the fourth isolation valve, the third pressure regulating valve, the fifth isolation valve, and the gas phase manifold under the action of the pressure difference. The gaseous carbon dioxide, after being depressurized by the third pressure regulating valve, is transported to the shore facility through the gas phase manifold.

[0032] As an optional implementation, in step S33, during the process of injecting liquid carbon dioxide from the low-pressure storage shore station to the medium-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 the sixth port → fifth port, the sixth isolation valve and the seventh isolation valve are opened, and other isolation valves of the volatile gas delivery and treatment system are closed at the same time; when the first pressure sensor detects that the pressure in the medium-pressure storage tank rises to the set value (this set value can be adjusted according to operational needs, and can be the design pressure of the medium-pressure storage tank minus 1 barg), an alarm signal is issued; (the operator) starts the gas compressor, and the excess gaseous carbon dioxide in the medium-pressure storage tank is extracted and pressurized (or pressurized) through the gas compressor by the gas collection pipe. After being pressurized by the gas compressor, the gaseous carbon dioxide enters the liquefaction device through the second remote control three-way valve (sixth port → fifth port) and the seventh 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, and is converted into liquid carbon dioxide, which is then injected into the medium-pressure storage tank through the liquid inlet pipe.

[0033] In this invention, during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station into the medium-pressure storage tank, since the storage pressure of the medium-pressure storage shore station is similar to the pressure inside the medium-pressure storage tank, a gas return route needs to be selected based on the actual situation. When the storage pressure of the medium-pressure storage shore station is lower than the pressure of the medium-pressure storage tank, natural gas return is achieved through the pressure difference, and excess gaseous carbon dioxide in the medium-pressure storage tank is returned to the medium-pressure storage shore station via the gas return pipeline. When the storage pressure of the medium-pressure storage shore station is higher than the pressure of the medium-pressure storage tank, natural gas return cannot be achieved using the pressure difference. In this case, excess gaseous carbon dioxide needs to be extracted from the medium-pressure storage tank using a gas compressor and increased, and then, under the action of the pressure difference, the excess gaseous carbon dioxide in the medium-pressure storage tank is returned to the medium-pressure storage shore station.

[0034] In this invention, during the process of injecting liquid carbon dioxide from a high-pressure storage shore station into a medium-pressure storage tank, the storage pressure at the high-pressure shore station is much higher than the pressure inside the medium-pressure storage tank, making natural gas return impossible due to the pressure difference. In this case, excess gaseous carbon dioxide is extracted from the medium-pressure storage tank using a gas compressor and then added to it. Under the action of the pressure difference, the excess gaseous carbon dioxide in the medium-pressure storage tank is then returned to the high-pressure storage shore station.

[0035] As an optional implementation, in step S32, during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the medium-pressure storage tank, if the pressure of the medium-pressure storage tank is higher than the pressure setting value of the medium-pressure storage tank, the second remote control three-way valve is set to the sixth port → fourth port, the sixth isolation valve is opened, and other isolation valves of the volatile gas conveying and processing system are closed; when the pressure of the medium-pressure storage tank monitored by the first pressure sensor reaches the pressure setting value (this setting value can be adjusted according to operational needs, and can be the design pressure of the medium-pressure storage tank minus 1 barg), the gas compressor is started to extract and pressurize the excess gaseous carbon dioxide in the medium-pressure storage tank (through the gas collecting pipe), so that the pressure of the gaseous carbon dioxide after being pressurized by the gas compressor is higher than (e.g., 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 second remote control three-way valve (sixth port → fourth port) and the gas phase manifold.

[0036] Preferably, the gas compressor adopts frequency conversion control and multi-stage parallel operation to comprehensively regulate the outlet pressure of the gas compressor, that is, the pressure rise value of gaseous carbon dioxide after passing through the gas compressor.

[0037] As an optional implementation, in step S33, during the process of injecting liquid carbon dioxide from the medium-pressure storage shore station or the high-pressure storage shore station into the medium-pressure storage tank, if the pressure of the medium-pressure storage tank is higher than the pressure set value of the medium-pressure storage tank, and if the medium-pressure storage shore station or the high-pressure storage shore station does not accept the returned gaseous carbon dioxide, step S32 is used to liquefy the excess gaseous carbon dioxide in the medium-pressure storage tank through a liquefaction device and then return it to the medium-pressure storage tank. Specifically, the excess gaseous carbon dioxide in the medium-pressure storage tank is extracted and pressurized by a gas compressor. The gaseous carbon dioxide pressurized by the gas compressor enters the liquefaction device and is converted into liquid carbon dioxide before being injected into the medium-pressure storage tank.

[0038] As an optional implementation, in step S31, during the process of transferring liquid carbon dioxide from the medium-pressure storage tank to the storage shore station, if the storage shore station cannot provide the gas reverse transfer in step S31, self-evaporation pressure holding treatment is required. That is, the self-evaporation pressure holding system is required to control the pressure inside the medium-pressure storage tank to avoid the pressure from falling below the minimum design pressure of the storage tank.

[0039] Specifically, in step S4, the pressure of the gas phase space inside the medium-pressure storage tank is monitored in real time using a first pressure sensor. When the pressure drops to the low-pressure set value, the first pressure sensor sends a signal to open the pressure control valve, connecting the self-evaporating pressure-maintaining system with the liquid outlet pipe. At this time, some of the externally supplied liquid carbon dioxide enters the self-evaporating pressure-maintaining pipe. This portion of liquid carbon dioxide is vaporized by the evaporator and then returned to the medium-pressure storage tank through the gas collection pipe. As gaseous carbon dioxide continues to enter, the pressure inside the medium-pressure storage tank gradually rises. When the pressure rises to the high-pressure set value, the first pressure sensor sends a signal again to close the pressure control valve, ending the self-evaporating pressure-maintaining process.

[0040] As an optional implementation, the transfer method for low-pressure storage and transportation of liquid carbon dioxide vessels is also applicable to transfer operations between carbon dioxide vessels with different storage pressures.

[0041] In this invention, the above-mentioned technical features can be freely combined to form new technical solutions, provided they do not conflict with each other.

[0042] (III) Beneficial Effects The above-described technical solution of the present invention has at least the following advantages: 1. The transshipment method for medium-pressure storage and transportation of liquid carbon dioxide provided by the present invention, through multi-process design, allows operators to reasonably select different operation processes according to the storage conditions of the matching storage shore station, effectively compatible with low-pressure or high-pressure storage shore stations, and greatly improves the compatibility of the vessel. 2. The liquefaction system and transfer method for medium-pressure storage and transportation of liquid carbon dioxide provided by the present invention enhances the ship's ability to control tank pressure during loading and unloading by setting up a self-evaporation pressure-maintaining system and a process for liquefying excess gaseous carbon dioxide back into the tank, reduces the ship's dependence on storage shore station facilities, and further improves the flexibility of ship operation. 3. The transshipment method for medium-pressure storage and transportation of liquid carbon dioxide provided by the present invention adopts a specially designed operation process, and the relevant setting parameters can be adjusted according to the actual situation of the docking storage shore station, which effectively reduces the energy consumption of ship operation and improves the ship's economy. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram illustrating the structural division of the liquid cargo barge transportation system for a medium-pressure storage and transportation vessel for liquid carbon dioxide provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the liquid cargo barge transportation system for a medium-pressure storage and transportation vessel for liquid carbon dioxide provided in an embodiment of the present invention; Figure 3 This diagram illustrates the structure of the low-pressure desuperheating device provided in an embodiment of the present invention. Figure 4 This diagram illustrates the structure of the high-pressure heating device provided in an embodiment of the present invention. Figure 5 This diagram illustrates the structure of the medium-pressure heating device provided in an embodiment of the present invention. Figure 6 This diagram illustrates the structure of the medium-pressure desuperheating device provided in an embodiment of the present invention. Figure 7 This diagram illustrates the structure of the liquefaction device provided in an embodiment of the present invention. The labels for the attached figures are as follows: 1. Medium-pressure storage tank; 2. Transfer pump; 3. Pressure control valve; 4. Evaporator / vaporizer; 5. First pressure sensor; 6. First isolation valve; 7. First pressure regulating valve; 8. First check valve; 9. Second isolation valve; 10. Pressure reducing valve; 11. Second pressure sensor; 12. Low-pressure desuperheating device; 13. Second check valve; 14. Third isolation valve; 15. High-pressure booster pump; 16. High-pressure heating device; 17. Medium-pressure booster pump; 18. Medium-pressure heating device; 19. First remote-controlled three-way valve; 20. Second pressure regulating valve; 21. Medium-pressure desuperheating device; 22. Second remote-controlled three-way valve; 23. Fourth isolation valve; 24. Third pressure regulating valve; 25. Fifth isolation valve; 26. Sixth isolation valve; 27. Gas compressor; 28. Seventh isolation valve; 29. ​​Liquefaction unit; 30. Eighth isolation valve; 31. Fourth pressure regulating valve; 32. Ninth isolation valve; 33. Third check valve; L1, Liquid Outlet Pipe; L2, Liquid Inlet Pipe; L3, Low-Pressure Export Pipe; L4, Medium-Pressure Export Pipe; L5, High-Pressure Export Pipe; L6, Liquefied Gas Return Pipe; L7, Gas Return Pipe; L8, Gas Return Pipe; V1, Self-Evaporating Pressure Holding Pipe; V2, Gas Collector Pipe; C1, Liquid Phase Collector Pipe; C2, Gas Phase Collector Pipe. I. Low-pressure export system; II. Medium-pressure export system; III. High-pressure export system; IV. Self-evaporating pressure-maintaining system; V. Medium / high-pressure injection system; VI. Low-pressure injection system; VII. Volatile gas transportation and treatment system. 12-1 Low-pressure heat exchanger; 12-2 First refrigerant unit; 12-3 Low-pressure temperature sensor; 16-1, High-pressure heater; 16-2, First temperature control valve; 16-3, High-pressure temperature sensor; 18-1, Medium-pressure heater; 18-2, Second temperature control valve; 18-3, First medium-pressure temperature sensor; 21-1, Medium-pressure heat exchanger; 21-2, Second refrigerant unit; 21-3, Temperature-controlled three-way valve; 21-4, Second medium-pressure temperature sensor; 29-1, Liquefaction heat exchanger; 29-2, Refrigeration unit. Detailed Implementation

[0045] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0046] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be located directly on or indirectly on the other component. When a component is referred to as "connected to" another component, it can be directly or indirectly connected to the other component.

[0047] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate that the device or element must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or the number of technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. The specific implementation of this invention will be described in more detail below with reference to specific embodiments: like Figure 1 , Figure 2 and Figure 3 As shown, this embodiment of the invention provides a liquid cargo barge transport system for medium-pressure storage and transportation vessels carrying liquid carbon dioxide, such as... Figure 1 As shown, the liquid cargo transshipment system includes: a medium-pressure storage tank 1, a transfer pump 2, an external transport system (including a low-pressure external transport system I, a medium-pressure external transport system II, and a high-pressure external transport system III), a self-evaporating 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 transport and treatment system VII; as shown Figure 2 As shown, the liquid cargo system also includes a liquid phase manifold C1, a gas phase manifold C2, a gas collection pipe V2, a self-evaporating pressure-maintaining pipe V1, a liquid inlet pipe L2, and a liquid outlet pipe L1; wherein, Medium-pressure storage tank 1 is used for medium-pressure storage of liquid carbon dioxide; The transfer pump 2 is connected to the liquid outlet pipe L1 and is used to transfer the liquid carbon dioxide in the medium-pressure storage tank 1 to the outside. The external transmission system includes three parallel systems: a low-pressure external transmission system I, a medium-pressure external transmission system II, and a high-pressure external transmission system III. Their input ends are connected to the liquid outlet pipe L1, and they are used to transport liquid carbon dioxide to storage shore stations (including low-pressure, medium-pressure, and high-pressure storage shore stations) with different storage pressures. The output ends of the low-pressure external transmission system I, medium-pressure external transmission system II, and high-pressure external transmission system III are connected to the liquid phase manifold C1. The input end of the self-evaporating pressure-holding system IV is connected to the liquid outlet pipe L1, and the output end is connected to the gas collection pipe V2. It is used to control the pressure in the medium-pressure storage tank 1 when liquid carbon dioxide is exported. The injection system is connected to the liquid phase manifold C1 via the first remote-controlled three-way valve 19, and its output end is connected to the liquid inlet pipe L2, which is used to inject liquid carbon dioxide from the storage shore station into the medium-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; The volatile gas conveying and processing system VII is used to convey and process volatile gases and balance system pressure during the external delivery or injection of carbon dioxide; its output end is connected to the liquid inlet pipe L2 and the gas collection pipe V2 respectively. Liquid phase manifold C1 is used to receive or output liquid carbon dioxide; The gas phase manifold C2 is used to receive or output gaseous carbon dioxide.

[0049] In this invention, the low-pressure export system I, the medium-pressure export system II, and the high-pressure export system III are connected to the liquid outlet pipe and arranged in parallel. Therefore, the export system is selected based on the storage pressure of the liquid carbon dioxide receiving and storage shore station. For example, if the liquid carbon dioxide receiving and storage shore station is a low-pressure storage shore station, the low-pressure export system I is selected to export the liquid carbon dioxide from the medium-pressure storage tank 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 export system III is selected to export the liquid carbon dioxide from the medium-pressure storage tank to the high-pressure storage shore station.

[0050] In some embodiments, the liquid manifold C1 is connected to a low-pressure storage shore station, a medium-pressure storage shore station, or a high-pressure storage shore station via a liquid phase interface of a loading / unloading facility (such as a loading arm or a loading hose).

[0051] In some embodiments, the gas phase manifold C2 is connected to a gas delivery facility, such as a loading arm or loading hose gas phase interface.

[0052] In some embodiments, the input end of the liquid inlet pipe L2 is connected to the medium / high pressure injection system V and the low pressure injection system VI, respectively, and the opening of the output end is located inside the medium pressure storage tank 1.

[0053] In some embodiments, the input end of the liquid inlet pipe L2 is also connected to the liquefaction return pipe L6 of the volatile gas delivery and treatment system VII.

[0054] In some embodiments, the output of the self-evaporating pressure-holding system IV is connected to the gas collection pipe V2.

[0055] Optionally, the opening connecting the gas collecting pipe V2 to the medium-pressure storage tank 1 is located at the top of the medium-pressure storage tank 1.

[0056] In some embodiments, the output of the volatile gas delivery and treatment system VII is connected to the liquid inlet pipe L2 and the gas collection pipe V2, respectively.

[0057] In some embodiments, the medium-pressure storage tank 1 adopts a Type C storage compartment as defined by the IMO. The material of the medium-pressure storage tank meets the pressure and temperature requirements for medium-pressure storage of liquid carbon dioxide, and is covered with external insulation material; the insulation material has a low thermal conductivity, including polyurethane or polystyrene; the insulation material is installed on the outside of the medium-pressure storage tank 1 using prefabricated insulation modules or on-site spraying foaming methods.

[0058] In some embodiments, the delivery pump 2 is installed inside the medium-pressure storage tank 1 and can be a deep well pump or a submersible pump. Its outlet is connected to the liquid outlet pipe L1. One end of the liquid outlet pipe L1 is connected to the outlet of the delivery pump 2, and the other end is connected to multiple external delivery system pipes and a self-evaporating pressure-maintaining pipe V1.

[0059] In this invention, the low-pressure export system I, the medium-pressure export system II, and the high-pressure export system III are respectively connected to the liquid outlet pipe L1 and arranged in parallel. One of them is selected according to the storage pressure of the liquid carbon dioxide receiving and storage shore station. The self-evaporation pressure-maintaining system IV is connected to the liquid outlet pipe L1 at one end and to the gas collection pipe V2 at the other end. The gas collection pipe V2 has one end open at the top of the medium-pressure storage tank 1 and the other end is also connected to the volatile gas transportation and treatment system VII.

[0060] In some embodiments, such as Figure 2 As shown, the low-pressure export system I includes a second isolation valve 9, a pressure reducing valve 10, a second pressure sensor 11, a low-pressure desuperheating device 12, and a second check valve 13. The second isolation valve 9 is installed on the low-pressure export pipeline L3 of the low-pressure export system I and is used to control the opening and closing of the low-pressure export pipeline L3. The pressure reducing valve 10 is used to reduce the pressure of the liquid carbon dioxide exported from the low-pressure export system to a pressure acceptable to the low-pressure storage shore station. The second pressure sensor 11 is used to control the pressure reduction value through the pressure reducing valve 10, and its set value can be adjusted according to the actual pressure required by the low-pressure storage shore station. The low-pressure desuperheating device 12 is used to reduce the temperature of the liquid carbon dioxide after pressure reduction to a temperature acceptable to the low-pressure storage shore station. The second check valve 13 serves to prevent liquid backflow, and its outlet is connected to the liquid phase manifold C1. The liquid phase manifold C1 is connected to the loading and unloading facilities, such as the liquid phase interface of the loading and unloading arm or loading and unloading hose.

[0061] In some embodiments, such as Figure 4As shown, the low-pressure cooling device 12 includes a low-pressure heat exchanger 12-1, a first refrigerant unit 12-2, and a low-pressure temperature sensor 12-3. The low-pressure heat exchanger 12-1, including a plate heat exchanger or a shell-and-tube heat exchanger, is used to exchange heat between the depressurized liquid carbon dioxide and the refrigerant provided by the first refrigerant unit 12-2, thereby reducing the temperature of the depressurized liquid carbon dioxide. The low-pressure temperature sensor 12-3 is installed in the downstream pipeline of the low-pressure heat exchanger 12-1 to monitor the temperature of the fluid (i.e., liquid carbon dioxide) in the low-pressure export pipe L3. The first refrigerant unit 12-2 is used to supply heat to the low-pressure heat exchanger. The refrigerant 12-1 provides refrigerant, and the cooling energy provided by the refrigerant depends on the workload of the first refrigerant unit 12-2, which is controlled by the low-pressure temperature sensor 12-3. By comparing the measured value of the low-pressure temperature sensor 12-3 with the temperature setpoint, when the measured value is lower than the setpoint, the workload of the first refrigerant unit 12-2 is increased. At this time, the provided cooling energy increases, and the temperature of the depressurized liquid carbon dioxide further decreases after passing through the low-pressure heat exchanger 12-1. Conversely, decreasing the workload of the first refrigerant unit 12-2 reduces the cooling of the liquid carbon dioxide after passing through the low-pressure heat exchanger 12-1. The refrigerant can be propane or propylene. In some embodiments, such as Figure 2 As shown, the medium-pressure export system II includes a first isolation valve 6, a first pressure regulating valve 7, and a first check valve 8. The first isolation valve 6 is installed on the medium-pressure export pipe L4 of the medium-pressure export system II to control the opening and closing of the medium-pressure export pipe L4. The first pressure regulating valve 7 controls the pressure of the liquid carbon dioxide exported from the medium-pressure export system II. The outlet of the first check valve 8 is connected to the liquid phase manifold C1 to prevent liquid backflow. In some embodiments, such as Figure 2 As shown, the high-pressure export system III includes: a third isolation valve 14, a high-pressure booster pump 15, a high-pressure heating device 16, and a third check valve 33; the third isolation valve 14 is installed on the high-pressure export pipe L5 of the high-pressure export system III to control the opening and closing of the high-pressure export pipe L5; the high-pressure booster pump 15 is used to increase the pressure of the liquid carbon dioxide from the delivery pump; the high-pressure heating device 16 is used to increase the temperature of the pressurized liquid carbon dioxide; the outlet of the third check valve 33 is connected to the liquid phase manifold C1 to prevent liquid backflow.

[0062] In some embodiments, such as Figure 4As shown, the high-pressure heating device 16 includes: a high-pressure heater 16-1, a first 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 to monitor the temperature of the liquid carbon dioxide after pressurization and control the opening degree of the first temperature control valve 16-2; the first temperature control valve 16-2 can be pneumatically, electrically, or hydraulically driven, and its opening degree is controlled by the high-pressure temperature sensor 16-3 to regulate 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 heat exchanger 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 electrical energy, steam, hot oil, or ethylene glycol water.

[0063] In some embodiments, such as Figure 2 As shown, the self-evaporating pressure-maintaining system IV includes: a pressure control valve 3, an evaporator 4, and a first pressure sensor 5; one end of the evaporator is connected to the liquid outlet pipe L1 via a self-evaporating pressure-maintaining pipe V1, and the other end is connected to a 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, which is installed on the top of the medium-pressure storage tank 1 to monitor the pressure of the gas phase space at the top of the medium-pressure storage tank 1; the evaporator 4 can be plate type or shell-and-tube type, and its heat source can be electricity, steam, or hot oil, used to evaporate liquid carbon dioxide into gaseous carbon dioxide, which is then returned to the medium-pressure storage tank 1 via the gas collecting pipe V2.

[0064] In some embodiments, such as Figure 2 As 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 remote-controlled three-way valve 19, and the other end is connected to the liquid inlet pipe L2. The first remote-controlled three-way valve 19 has a first interface, a second interface, and a third interface. The first interface is connected to the liquid phase manifold C1. The third interface is connected to the low pressure injection system VI. The second interface is connected to the medium / high pressure injection system V. Different injection systems can be selected according to the liquid carbon dioxide pressure input from the storage shore station. The liquid inlet pipe L2 has one end 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 into the medium pressure storage tank 1.

[0065] In some embodiments, such as Figure 2The low-pressure injection system VI includes: a medium-pressure booster pump 17 and a medium-pressure heating device 18; the inlet of the medium-pressure booster pump 17 is connected to the third interface of the first remote-controlled three-way valve 19, and the output end is connected to the medium-pressure heating device 18, which is used to increase the pressure of the low-pressure liquid carbon dioxide from the low-pressure storage shore station; the medium-pressure heating device 18 is used to increase the temperature of the pressurized liquid carbon dioxide; so that the pressure and temperature of the liquid carbon dioxide from the low-pressure storage shore station meet the storage requirements of the medium-pressure storage tank; the output end of the low-pressure injection system VI is connected to the liquid inlet pipe L2 to control the pressure of the injected liquid carbon dioxide within a set range.

[0066] In some embodiments, such as Figure 5 As shown, the medium-pressure heating device 18 includes: a medium-pressure heater 18-1, a second temperature control valve 18-2, and a first medium-pressure temperature sensor 18-3; the first medium-pressure temperature sensor 18-3 is installed at the outlet of the medium-pressure heater 18-1 to monitor the temperature of the liquid carbon dioxide after pressurization and control the opening degree of the second temperature control valve 18-2; the second temperature control valve 18-2 is used to regulate the amount of heat exchange medium entering the medium-pressure heater 18-1, thereby controlling the temperature of the liquid carbon dioxide passing through the medium-pressure heat exchanger 18-1; the heat exchange medium can be ethylene glycol water or other low-pour-point liquids.

[0067] In some embodiments, such as Figure 2 As shown, the medium / high pressure injection system V includes: a second pressure regulating valve 20 and a medium pressure desuperheating device 21. The input end of the medium / high pressure injection system V is connected to the second interface of the first remote control three-way valve 19, and the output end is connected to the liquid inlet pipe L2. The second pressure regulating valve 20 is used to regulate the pressure of the liquid carbon dioxide injected into the medium / high pressure injection system V to meet the storage requirements of the medium pressure storage tank. The medium pressure desuperheating device 21 is used to control the temperature of the input liquid carbon dioxide after pressure regulation.

[0068] In some embodiments, such as Figure 6 As shown, the medium-pressure cooling device 21 includes: a medium-pressure heat exchanger 21-1, a second refrigerant unit 21-2, a temperature-controlled three-way valve 21-3, and a second medium-pressure temperature sensor 21-4. The temperature-controlled three-way valve 21-3 has linear adjustment capability and is connected to the system through three interfaces: "a", "b", and "c". The second medium-pressure temperature sensor 21-4 is used to monitor the temperature of liquid carbon dioxide and, by adjusting the opening of the temperature-controlled three-way valve 21-3, i.e., the flow ratio of "ac" and "bc", controls the flow rate of liquid carbon dioxide flowing through the medium-pressure heat exchanger 21-1, thereby controlling the temperature of the mixed liquid carbon dioxide to meet the design requirements. The medium-pressure heat exchanger 21-1 includes a plate heat exchanger or a shell-and-tube heat exchanger. The second refrigerant unit 21-2 controls the temperature of the heat exchange medium through a secondary heat exchange cycle, providing pre-cooled refrigerant to the medium-pressure heat exchanger 21-1. The refrigerant can be propane or propylene.

[0069] In some embodiments, such as Figure 2 As shown, the volatile gas transport and processing system VII includes a second remote-controlled three-way valve 22, a gas compressor 27, a liquefaction device 29, a third pressure regulating valve 24, a fourth pressure regulating valve 31, a liquefaction return pipe L2, a gas return to shore pipe L7, and a gas return pipeline L8. The second remote-controlled three-way valve 22 is used to control the flow direction of the volatile gas and has a fourth interface, a fifth interface, and a sixth interface. The fourth interface is connected to the gas phase manifold C2; the fifth interface is connected to the liquefaction return pipe L6; and the sixth interface is connected to the outlet of the gas compressor 27. The third pressure regulating valve 24 is used to control the pressure of gaseous carbon dioxide (i.e., return gas) returning from the medium-pressure storage tank 1 to the shore station. The fourth pressure regulating valve 31 is used to control the pressure of gaseous carbon dioxide (i.e., return gas) being transported from the shore station to the medium-pressure storage tank 1.

[0070] In some embodiments, such as Figure 2 As shown, the gas compressor 27 can be a screw type or a piston type. Its inlet side is connected to the gas collection pipe V2 through the sixth isolation valve 26, and its outlet is connected to the sixth port of the second remote control three-way valve 22. The volatile gas compressed by the gas compressor 27 can return to the storage shore station receiving device through the flow path of the second remote control three-way valve 22 (sixth port → fourth port) and the gas phase manifold C2, or it can be connected to the liquefaction return pipe L6 through the flow path of the second remote control three-way valve 22 (sixth port → fifth port), and returned to the medium-pressure storage tank 1 after liquefaction by the liquefaction device 29.

[0071] In some embodiments, such as Figure 2 As shown, a seventh isolation valve 28 is installed on the liquefaction return pipe L6; a liquefaction unit 29 is installed downstream of the seventh isolation valve 28. The liquefaction unit 29 includes a liquefaction heat exchanger 29-1 and a refrigeration unit 29-2 (e.g., Figure 7 (As shown); the liquefaction heat exchanger 29-1 can be plate type, shell and tube type or printed circuit board type, which can cool and liquefy compressed gaseous carbon dioxide; the refrigeration unit 29-2 provides refrigerant to the liquefaction heat exchanger 29-1, which can be propane or propylene, and the liquefied carbon dioxide returns to the medium-pressure storage tank 1 through the liquid inlet pipe L2. In some embodiments, such as Figure 2 As shown, the gas return pipe L7 is equipped with a fourth isolation valve 23, a third pressure regulating valve 24 and a fifth isolation valve 25. The third pressure regulating valve 24 can be a diaphragm type, a spring piston type or a bellows type, which regulates the pressure of gaseous carbon dioxide from the medium-pressure storage tank 1 so that the pressure meets the requirements for returning to the storage shore station.

[0072] In some embodiments, such as Figure 2As shown, the gas return pipe L8 is equipped with an eighth isolation valve 30, a fourth pressure regulating valve 31, and a ninth isolation valve 32. The fourth pressure regulating valve 31 can be a diaphragm type, a spring piston type, or a bellows type, which regulates the pressure of gaseous carbon dioxide from the storage shore station so that the pressure meets the requirements for returning to the medium-pressure storage tank 1.

[0073] Some embodiments of the present invention also provide a transshipment method for a medium-pressure storage and transportation vessel carrying liquid carbon dioxide, which employs the above-described liquid cargo transshipment system for medium-pressure storage and transportation vessels carrying liquid carbon dioxide. The transshipment method includes the following steps: Step S1: Transferring liquid carbon dioxide to the storage shore station, including the following steps: Step S11: Connect the liquid phase manifold C1 and the gas phase manifold C2 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 outlet pipe. Step S12: The liquid carbon dioxide in the medium-pressure storage tank 1 is output through the transfer pump 2 and transported to the storage shore station through the external transmission system; Step S2: Injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank 1, including the following steps: Step S21: Connect the liquid phase manifold and the gas phase manifold to the loading facilities and gas transmission facilities of the storage shore station, respectively, and select the flow path of the first remote-controlled three-way valve 19 according to the storage pressure of the storage shore station. Step S22: Liquid carbon dioxide from the storage shore station flows sequentially through the liquid phase manifold C1 and the first remote-controlled three-way valve 19 into the injection system. The pressure and temperature of the carbon dioxide in the injection system are adjusted, and then injected into the medium-pressure storage tank 1. Step S3: Volatile gas conveying and treatment, including the following steps: Step S31: During the process of transferring liquid carbon dioxide from medium-pressure storage tank 1 to the storage shore station, in order to avoid the pressure inside medium-pressure storage tank 1 from falling below the minimum design pressure of the tank, gaseous carbon dioxide from the storage shore station is transported to medium-pressure storage tank 1 (i.e., the gas phase space of medium-pressure storage tank 1) through gas manifold C2 under the action of pressure difference, i.e., gas return; the pressure difference can be generated by the pressure difference between the shore storage tank and medium-pressure storage tank 1, or by using the shore station compressor to pressurize the returned gas.

[0074] Step S32: During the process of injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank 1, when the pressure of the medium-pressure storage tank 1 is higher than the pressure set value of the medium-pressure storage tank 1, the gaseous carbon dioxide in the medium-pressure storage tank 1 is returned to the storage shore station through the gas phase manifold under the action of the pressure difference, that is, the gas returns to shore; the pressure difference can be generated by the pressure difference between the medium-pressure storage tank 1 and the storage tank on shore, or by using the gas compressor 27 on the ship to pressurize the gas returning to shore.

[0075] 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 medium-pressure storage tank 1 is extracted and pressurized by the gas compressor 27. The gaseous carbon dioxide pressurized by the gas compressor 27 enters the liquefaction device 29 and is converted into liquid carbon dioxide, which is then injected into the medium-pressure storage tank 1. Step S34: During the process of transferring liquid carbon dioxide from medium-pressure storage tank 1 to the storage shore station, if the pressure of the medium-pressure storage tank increases, in order to avoid the pressure of medium-pressure storage tank 1 from exceeding the design pressure of medium-pressure storage tank 1, the operation in step 32 is adopted; that is, the gaseous carbon dioxide in medium-pressure storage tank 1 is returned to the low-pressure storage shore station through gas phase manifold C2 under the action of pressure difference. Step S35: During the process of injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank 1, if the pressure of the medium-pressure storage tank drops, in order to avoid the pressure in the medium-pressure storage tank falling below the minimum design pressure of the tank, the operation in step 31 is adopted; that is, the gas collecting pipe V2 is connected to the gas phase space of the low-pressure storage shore station through the gas phase manifold C2, and the gaseous carbon dioxide of the storage shore station is transported to the medium-pressure storage tank 1 through the gas manifold C2 under the action of pressure difference.

[0076] Step S4: Self-evaporation and pressure holding treatment, including the following steps: When the pressure in the gas phase space inside the medium-pressure storage tank 1 drops to the low-pressure set value, the pressure control valve 3 is opened to connect the self-evaporation pressure-maintaining system IV with the liquid outlet pipe L1. Some of the exported liquid carbon dioxide enters the self-evaporation pressure-maintaining pipe V1, is vaporized by the evaporator vaporizer 4, and is then returned to the medium-pressure storage tank 1 through the gas collection pipe V2. When the pressure in the gas phase space inside the medium-pressure storage tank 1 rises to the high-pressure set value, the pressure control valve 3 is closed, and the self-evaporation pressure-maintaining process ends.

[0077] In some embodiments, in step S1, liquid carbon dioxide is transferred to the low-pressure storage shore station (denoted as: method S1-1), and the specific steps are as follows: Step S11: Connect the liquid phase manifold C1 and the gas phase manifold C2 to the unloading facility and the gas conveying 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 9 to connect the low-pressure external transmission system I to the liquid outlet pipe L1. Step S12: Start the transfer pump 2. The liquid carbon dioxide in the medium-pressure storage tank 1 is output by the transfer 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 passes through the pressure reducing valve 10 and the low-pressure desuperheating device 12 to adjust the pressure and temperature. The depressurized and cooled liquid carbon dioxide enters the liquid phase manifold C1 through the second one-way valve 13 and is transported outward through the unloading facility connected to the liquid phase manifold C1, thus completing the transfer of liquid carbon dioxide to the low-pressure storage shore station. In some embodiments, in step S1, liquid carbon dioxide is transferred to the medium-pressure storage shore station (denoted as: method S1-2), and the specific steps are as follows: Step S11: Connect the liquid phase manifold C1 and the gas phase manifold C2 to the unloading facility and the gas conveying facility respectively; close the second isolation valve 9 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 to connect the medium-pressure external transmission system II to the liquid outlet pipe L1. Step S12: Start the transfer pump 2. The liquid carbon dioxide in the medium-pressure storage tank 1 is output by the transfer 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 pressure regulated by the first pressure regulating valve 7. The pressure-regulated liquid carbon dioxide enters the liquid phase manifold C1 through the first check valve 8 and is transported outward through the unloading facility connected to the liquid phase manifold C1, thus completing the transfer of liquid carbon dioxide to the medium-pressure storage shore station.

[0078] In some embodiments, in step S1, liquid carbon dioxide is transferred to the high-pressure storage shore station (denoted as: method S1-3), and the specific steps are as follows: Step S11: Connect the liquid phase manifold C1 and the gas phase manifold C2 to the unloading facility and the gas conveying facility respectively; close the first isolation valve 6 and the second isolation valve 9; disconnect the low-pressure external transmission system I and the medium-pressure external transmission system II; open the third isolation valve 14 to connect the high-pressure external transmission system III to the liquid outlet pipe L1. Step S12: Start the transfer pump 2. The liquid carbon dioxide in the medium-pressure storage tank 1 is output by the transfer 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. The pressurized liquid carbon dioxide then passes 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 enters the liquid phase manifold C1 through the third one-way valve 33 and is transported outward through the unloading facility connected to the liquid phase manifold C1, thus completing the transfer of liquid carbon dioxide to the high-pressure storage shore station.

[0079] In some embodiments, in step S2, liquid carbon dioxide is injected from a low-pressure storage shore station (denoted as: method S2-1), and the specific steps are as follows: Step S21: Connect the liquid phase manifold C1 and the gas phase manifold C2 to the loading facilities and gas transmission facilities of the storage shore station, respectively, and set the flow path of the remote control three-way valve 19 to the first interface → the third interface. Step S22: Low-pressure liquid carbon dioxide from the storage shore station flows sequentially through the liquid phase manifold C1 and the remote-controlled three-way valve 19 (first port → third port), and then, after its pressure and temperature are adjusted by the medium-pressure booster pump 17 and the medium-pressure heating device 18, it is injected into the medium-pressure storage tank 1 through the liquid inlet pipe L2. The pressure of the liquid after being boosted by the medium-pressure booster pump is slightly higher than the pressure inside the medium-pressure storage tank 1, and it can overcome the back pressure injected into the medium-pressure storage tank 1. The liquid carbon dioxide after being heated by the medium-pressure heating device 18 meets the storage requirements of the medium-pressure storage tank 1.

[0080] 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 (denoted as: method S2-2), and the specific steps are as follows: Step S21: Connect the liquid phase manifold C1 and the gas phase manifold C2 to the loading facilities and gas transmission facilities of the storage shore station, respectively, and set the flow path of the remote control three-way valve 19 to the first interface → the second interface. Step S22: Medium-pressure or high-pressure liquid carbon dioxide from the storage shore station flows sequentially through the liquid phase manifold C1 and the remote-controlled three-way valve 19 (first interface → second interface) under the action of pressure difference. Through the second pressure regulating valve 20, the pressure of the injected liquid carbon dioxide is reduced to slightly higher than the pressure inside the medium-pressure storage tank 1, and is sufficient to overcome the back pressure injected into the medium-pressure storage tank 1. The medium-pressure de-cooling device 21 further cools the depressurized liquid carbon dioxide so that its temperature meets the storage requirements of the medium-pressure storage tank 1. The depressurized and de-cooled liquid carbon dioxide is injected into the medium-pressure storage tank 1 through the liquid inlet pipe L2.

[0081] In this invention, during the process of outputting or injecting liquid carbon dioxide into the medium-pressure storage tank 1, the liquid level inside the medium-pressure storage tank 1 continuously changes, the gas phase space is compressed or expanded, and the pressure in the gas phase space changes accordingly. To prevent the pressure inside the medium-pressure storage tank 1 from falling below or exceeding the minimum design pressure of the tank, it is necessary to transport and process the gaseous carbon dioxide inside the medium-pressure storage tank 1. Different processing steps are adopted for different processes.

[0082] In some embodiments, step S3, the volatile gas conveying and treatment includes the following steps: Liquid carbon dioxide is transferred to the low-pressure storage shore station (referred to as: Method S3-1). As the liquid carbon dioxide is transferred out, the liquid level in the medium-pressure storage tank 1 continuously decreases, the volume of the gas phase space increases, and the pressure decreases accordingly. To prevent the pressure in the medium-pressure storage tank 1 from falling below the minimum design pressure of the tank, which would cause the temperature of the liquid carbon dioxide in the medium-pressure storage tank at that pressure to fall below the minimum design temperature of the tank material (for example, the saturation temperature of liquid carbon dioxide corresponding to 13 barg is -33℃), a certain amount of gaseous carbon dioxide needs to be introduced from the outside, i.e., gas return. The gas return operation includes: usually, the pressure of gaseous carbon dioxide in the storage tank of the low-pressure storage shore station is lower than the pressure in the medium-pressure storage tank on the ship; therefore, gas return cannot be achieved through pressure difference. If the low-pressure storage shore station has a carbon dioxide gas pressurization and return function, such as being equipped with a pressurization compressor, then the eighth isolation valve 30 and the ninth isolation valve 32 are opened, while other isolation valves in the volatile gas transport and treatment system VII are closed. The gaseous carbon dioxide, after being pressurized by the shore station's carbon dioxide gas pressurization facility, flows sequentially through the gas phase manifold C2, the ninth isolation valve 32, the fourth pressure regulating valve 31, and the eighth isolation valve 30. After being depressurized by the fourth pressure regulating valve 31, the gaseous carbon dioxide is input into the gas phase space of the medium-pressure storage tank 1 through the gas collection pipe V2. If the low-pressure storage shore station does not have a carbon dioxide gas pressurization and return function, then the self-evaporating pressure holding system IV needs to be used to control the pressure in the medium-pressure storage tank 1. The specific operation is as described in step S4.

[0083] In some embodiments, step S3, the volatile gas conveying and treatment includes the following steps: Liquid carbon dioxide is transferred to a medium-pressure or high-pressure storage shore station (referred to as: Method S3-2). To prevent the pressure inside the medium-pressure storage tank 1 from falling below the minimum design pressure of the tank during the transfer process, gas backflow is required. The gas backflow operation includes: opening the eighth isolation valve 30 and the ninth isolation valve 32, while closing other isolation valves in the volatile gas transport and treatment system VII. Under the action of the pressure difference, the gaseous carbon dioxide from the medium-pressure or high-pressure storage shore station flows sequentially through the gas phase manifold C2, the ninth isolation valve 32, the fourth pressure regulating valve 31, and the eighth isolation valve 30. After being depressurized by the fourth pressure regulating valve 31, the gaseous carbon dioxide is input into the gas phase space of the medium-pressure storage tank 1 through the gas collecting pipe V2.

[0084] In some embodiments, step S3, the volatile gas conveying and treatment includes the following steps: In the process of injecting liquid carbon dioxide from a low-pressure storage shore station or a medium-pressure storage shore station (referred to as: method S3-3), in order to prevent the pressure in the medium-pressure storage tank 1 from exceeding the design pressure of the medium-pressure storage tank 1, gas return to shore is required. The gas return to shore operation includes: opening the fourth isolation valve 23 and the fifth isolation valve 25, and simultaneously closing other isolation valves in the volatile gas transport and treatment system VII. The excess gaseous carbon dioxide from the medium-pressure storage tank 1 flows sequentially through the gas collection pipe V2, the fourth isolation valve 23, the third pressure regulating valve 24 and the fifth isolation valve 25, and the gas phase manifold C2 under the action of pressure difference. The gaseous carbon dioxide after being depressurized by the third pressure regulating valve 24 is transported to the shore facility through the gas phase manifold C2.

[0085] In some embodiments, step S3, the volatile gas conveying and treatment includes the following steps: During the process of injecting liquid carbon dioxide from the high-pressure storage shore station (referred to as: method S3-4), since the storage pressure of the storage shore station is much higher than the pressure in the medium-pressure storage tank 1, natural gas return cannot be achieved through pressure difference. At this time, the second remote control three-way valve 22 can be set to the sixth port → fourth port, the fifth isolation valve 24 can be opened, and the seventh isolation valve 27 can be closed. When the pressure of the medium-pressure storage tank 1 monitored by the first pressure sensor 5 reaches the set value (this set value can be adjusted according to operational needs, and can be the design pressure of the medium-pressure storage tank 1 minus 1 barg), an alarm signal is issued. The operator starts the gas compressor 27, and the excess gaseous carbon dioxide in the medium-pressure storage tank 1 is extracted by the gas compressor 27 through the gas phase manifold C2, pressurized by the gas compressor 27 to slightly higher than the storage pressure of the storage shore station, and then returned to the medium-pressure storage shore station or the high-pressure storage shore station through the second remote control three-way valve 22 (sixth port → fourth port) and the gas phase manifold C2 connected to the gas delivery device.

[0086] In some embodiments, step S3, the volatile gas conveying and treatment includes the following steps: During the injection of liquid carbon dioxide from the storage shore station, if the storage shore station does not receive the returned gaseous carbon dioxide (referred to as: method S3-5), the second remote control three-way valve 22 can be set to the sixth port → fifth port, and the sixth isolation valve 26 and the seventh isolation valve 28 can be opened. When the first pressure sensor 5 detects that the pressure in the medium-pressure storage tank 1 rises to the set value (this set value can be adjusted according to operational needs, and can be the design pressure of the medium-pressure storage tank 1 minus 1 barg), an alarm signal is issued. At this time, the operator starts the gas compressor 27. Excess gaseous carbon dioxide in the medium-pressure storage tank 1 is extracted by the gas compressor 27 through the gas collecting pipe V2. After being pressurized by the gas compressor 27, the gaseous carbon dioxide enters the liquefaction unit 29 through the second remote control three-way valve 22 (sixth port → fifth port) and the seventh isolation valve 28. The pressurized gaseous carbon dioxide completes heat exchange with the refrigerant from the refrigeration unit 29-2 in the liquefaction heat exchanger 29-1, and is converted into liquid carbon dioxide, which is then injected into the medium-pressure storage tank 1 through the liquid inlet pipe L2.

[0087] In some embodiments, step S4, the self-evaporation pressure holding process, includes the following steps: When the pressure in the gas phase space inside the medium-pressure storage tank 1 drops to the low-pressure set value, the pressure control valve 3 is opened to connect the self-evaporation pressure-maintaining system IV with the liquid outlet pipe L1. Some of the exported liquid carbon dioxide enters the self-evaporation pressure-maintaining pipe V1, is vaporized by the evaporator vaporizer 4, and is then returned to the medium-pressure storage tank 1 through the gas collection pipe V2. When the pressure in the gas phase space inside the medium-pressure storage tank 1 rises to the high-pressure set value, the pressure control valve 3 is closed, and the self-evaporation pressure-maintaining process ends.

[0088] In some embodiments, the self-evaporation pressure holding process includes the following steps: In steps S3-1 and S3-2, during the process of transferring liquid carbon dioxide from the medium-pressure storage tank to the storage shore station, if the storage shore station cannot provide the gas backflow in steps S3-1 and S3-2, or the pressure of the backflow gaseous carbon dioxide provided by the storage shore station is too low to overcome pipeline resistance and back pressure, self-evaporation pressure holding is required. That is, the self-evaporation pressure holding system IV is needed to control the pressure inside the medium-pressure storage tank 1 to prevent the pressure from falling below the triple point pressure of carbon dioxide. Specifically, the first pressure sensor 5 monitors the pressure of the gas phase space inside the medium-pressure storage tank 1 in real time. When the pressure drops to the low-pressure set value, the first pressure sensor 5 sends a signal to open the pressure control valve 3, connecting the self-evaporation pressure holding system IV with the liquid outlet pipe L1. At this time, part of the outflowing liquid carbon dioxide enters the self-evaporation pressure holding pipe V1. This part of the liquid carbon dioxide is vaporized by the evaporator 4 and then returned to the medium-pressure storage tank 1 through the gas collecting pipe V2. As gaseous carbon dioxide continues to enter, the pressure inside the medium-pressure storage tank 1 gradually rises. When the pressure rises to the high-pressure set value, the first pressure sensor 5 sends a signal again to close the pressure control valve 3, and the self-evaporation pressure holding process ends.

[0089] Example 1 This embodiment uses the transshipment method of the liquid cargo transshipment system of a 3500 cubic meter medium-pressure liquid carbon dioxide transport ship as an example to specifically illustrate the transshipment method of the present invention.

[0090] The 3,500 cubic meter low-pressure liquid carbon dioxide transport vessel is equipped with a medium-pressure storage tank 1 with a design pressure of 19 barg and a temperature of -33°C, for storing and transporting liquid carbon dioxide (normal storage pressure is 18 barg and temperature is -23°C).

[0091] The parameters for storing liquid carbon dioxide at shore stations under different pressures are as follows: The low-pressure storage shore station stores liquid carbon dioxide at a pressure of 8 barg and a temperature of -53°C. The medium-pressure shore storage station stores liquid carbon dioxide at a pressure of 15 barg and a temperature of -33°C. The high-pressure storage shore station stores liquid carbon dioxide at a pressure of 45 barg and a temperature of +30°C.

[0092] When a 3,000 cubic meter low-pressure liquid carbon dioxide carrier is loading and unloading cargo at a low-pressure storage shore station, the specific transshipment method is as follows: When unloading cargo from the ship to the low-pressure storage shore station: Connect the liquid phase manifold C1 and the gas phase manifold C2 to the storage shore station loading and unloading facilities and the gas transmission facilities, respectively; Adjust the relevant valve status according to the requirements of step S1 above, start the transfer pump 2, and transfer the liquid carbon dioxide in the medium-pressure storage tank 1 to the outside. The liquid carbon dioxide entering the low-pressure external transmission pipe L3 has a pressure of about 20 bar g and a temperature of -19.5℃. The pressure is reduced to 2 bar higher than the storage pressure of the low-pressure storage shore station, i.e., 10 bar g, through the pressure reducing valve 10. This pressure is used to overcome the pressure loss of the shore pipeline. After the pressure is reduced, the liquid carbon dioxide passes through the low-pressure desuperheating device 12, and the outlet temperature is controlled to be 3℃ lower than the saturation temperature of liquid carbon dioxide at 8 bar pressure, so as to offset the heat loss of the low-pressure storage shore station pipeline. After pressure adjustment and temperature control, the liquid carbon dioxide is transported to the low-pressure storage shore station through the liquid phase manifold C1.

[0093] During this process, in order to balance the pressure drop caused by the decrease in liquid level in medium-pressure storage tank 1 and to prevent the pressure in medium-pressure storage tank 1 from falling below the minimum design pressure of the tank (13 barg, at which the saturation temperature of liquid carbon dioxide is -32.7℃, higher than the minimum design temperature of medium-pressure storage tank 1 -33℃), it is necessary to supplement some gaseous carbon dioxide. The specific operation is as described in method S3-1 above. If the low-pressure storage shore station cannot provide gaseous carbon dioxide supplementation or the pressure of the gaseous carbon dioxide provided is too low, then it is not necessary to connect the gas phase manifold C2. At this point, the self-evaporating pressure-holding system IV is needed to control the pressure inside the medium-pressure storage tank 1. The specific operation is as follows: During the unloading process, when the first pressure sensor 5 detects that the pressure in the medium-pressure storage tank 1 drops to 13.5 barg (minimum design pressure + 0.5 bar), the pressure control valve 3 is opened. Some of the exported liquid carbon dioxide enters the evaporator vaporizer 4 through the opened pressure control valve 3. The vaporized carbon dioxide returns to the medium-pressure storage tank 1 through the gas collection pipe V2, which plays the role of controlling the pressure inside the medium-pressure storage tank 1. When the pressure inside the medium-pressure storage tank 1 rises to 18 barg (1 bar lower than the maximum design pressure), the first pressure sensor 5 sends a signal to close the pressure control valve 3, and the self-evaporating pressure-holding process ends.

[0094] When loading cargo from a low-pressure storage shore station to a ship: The liquid phase manifold C1 and the gas phase manifold C2 are respectively connected to the loading and unloading facilities and the gas transmission facilities of the low-pressure storage shore station; Adjust the relevant valve status according to the requirements of method S2-1 above. After being pressurized by the shore facilities, the liquid carbon dioxide from the low-pressure storage shore station enters the ship's pipeline through the liquid phase manifold C1. At this time, the pressure of the liquid carbon dioxide is about 10 barg and the temperature is -39℃. It is then pressurized again by the medium-pressure booster pump 17 to about 1 bar higher than the pressure of the medium-pressure storage tank 1, in order to overcome the pressure drop loss of the ship's pipeline, i.e., 18.5 barg. The pressurized liquid carbon dioxide passes through the medium-pressure heating device 18, which raises the temperature to about -22℃, and is injected into the medium-pressure storage tank 1 through the liquid inlet pipe L2.

[0095] During this process, in order to control the pressure rise in medium-pressure storage tank 1 due to the increase in liquid level and to prevent the pressure in medium-pressure storage tank 1 from exceeding its design pressure (19 barg), a portion of the excess gaseous carbon dioxide in medium-pressure storage tank 1 needs to be returned to the storage shore station through the gas phase manifold C2, as described in method S3-3. If the storage shore station does not receive the return of gaseous carbon dioxide, there is no need to connect the gas phase manifold C2, as described in method S3-5.

[0096] When a 3,000 cubic meter low-pressure liquid carbon dioxide carrier is loading and unloading cargo at a medium-pressure storage shore station, the specific transshipment method is as follows: When unloading cargo from the ship to the medium-pressure storage shore station: The liquid phase manifold C1 and the gas phase manifold C2 are respectively connected to the loading and unloading facilities and the gas transmission facilities of the medium-pressure storage shore station; Adjust the relevant valve status according to the requirements of method S1-2 above, start the transfer pump 2, and transfer the liquid carbon dioxide in the medium-pressure storage tank 1 to the outside. The transferred liquid carbon dioxide is pressurized to about 21 barg by the transfer pump 2. The pressure after adjustment by the first pressure regulating valve 7 (18 barg) is 3 bar higher than the storage pressure of the medium-pressure storage shore station, which is used to overcome the pressure loss of the shore pipeline. The pressure-regulated liquid carbon dioxide is transported to the medium-pressure storage shore station through the liquid phase manifold C1.

[0097] During this process, to balance the pressure drop in medium-pressure storage tank 1 caused by the decrease in liquid level and to prevent the pressure in medium-pressure storage tank 1 from falling below the minimum design pressure (13 barg), a portion of gaseous carbon dioxide needs to be replenished from the storage shore station via the gas phase manifold C2, as described in method S3-2. If the medium-pressure storage shore station cannot provide gaseous carbon dioxide replenishment, then there is no need to connect the gas phase manifold C2. In this case, the self-evaporating pressure-holding system IV needs to be used to control the pressure in medium-pressure storage tank 1, as described in step S4 above, which is the same as the self-evaporating pressure-holding operation when supplying to the low-pressure storage shore station.

[0098] When loading cargo from a medium-pressure storage shore station to a ship: The liquid phase manifold C1 and the gas phase manifold C2 are respectively connected to the loading and unloading facilities and the gas transmission facilities of the medium-pressure storage shore station; Adjust the relevant valve status according to the requirements in method S2-2 above. After being pressurized by the shore facilities, the liquid carbon dioxide from the medium-pressure storage shore station enters the ship's pipeline through the liquid phase manifold C1. At this time, the pressure of the liquid carbon dioxide is about 20 barg and the temperature is -22℃. The pressure is controlled by the second pressure regulating valve 20 to be about 0.5 bar higher than the pressure of the medium-pressure storage tank 1 to overcome the pressure drop loss of the ship's pipeline. The liquid carbon dioxide after depressurization is further cooled to -30℃ by the medium-pressure desuperheating device 21 and injected into the medium-pressure storage tank 1 through the liquid inlet pipe L2.

[0099] During this process, in order to control the pressure rise in the medium-pressure storage tank 1 due to the increase in liquid level and to prevent the pressure in the medium-pressure storage tank 1 from exceeding its design pressure (19 barg), a portion of the excess gaseous carbon dioxide in the medium-pressure storage tank 1 needs to be returned to the medium-pressure storage shore station through the gas phase manifold C2, as described in method S3-3. If the storage shore station does not receive the return of gaseous carbon dioxide, there is no need to connect the gas phase manifold C2, as described in method S3-5, where the pressurized gaseous carbon dioxide is liquefied through the liquefaction device 29 and returned to the tank.

[0100] When a 3,000 cubic meter low-pressure liquid carbon dioxide carrier is loading and unloading cargo at a high-pressure storage shore station, the specific transfer method is as follows: When unloading cargo from the ship to the high-pressure storage shore station: The liquid phase manifold C1 and the gas phase manifold C2 are respectively connected to the loading and unloading facilities and the gas transmission facilities of the high-pressure storage shore station; Adjust the relevant valve status according to the requirements of method S1-3 above, start the transfer pump 2, and transfer the liquid carbon dioxide in the medium-pressure storage tank 1 to the outside. The transferred liquid carbon dioxide is pressurized to about 48 barg by the high-pressure booster pump 15, which is about 3 bar higher than the storage pressure of the high-pressure storage shore station, in order to overcome the pressure loss of the shore pipeline. The temperature of the pressurized liquid carbon dioxide is raised to +27°C by the high-pressure heating device 16, which is slightly lower than the storage temperature of +30°C of the high-pressure storage shore station, in order to offset the heat loss of the storage shore station pipeline; the pressurized and heated liquid carbon dioxide is transported to the high-pressure storage shore station through the high-pressure manifold C3.

[0101] During this process, to balance the pressure drop in medium-pressure storage tank 1 caused by the decrease in liquid level and to prevent the pressure in medium-pressure storage tank 1 from falling below the minimum design pressure (13 barg), a portion of gaseous carbon dioxide needs to be replenished from the storage shore station via the gas phase manifold C2, as described in method S3-2. If the storage shore station cannot provide gaseous carbon dioxide replenishment, then it is not necessary to connect the gas phase manifold C2. In this case, the self-evaporating pressure-maintaining system IV needs to be used to control the pressure in medium-pressure storage tank 1, as described in step S4 above.

[0102] When loading cargo from a high-pressure storage shore station to a ship: Connect the liquid phase manifold C1 and the gas phase manifold C2 to the storage shore station loading and unloading facilities and the gas transmission facilities, respectively; Adjust the relevant valve status according to the requirements in method S2-2 above. Liquid carbon dioxide from the high-pressure storage shore station enters the ship's pipeline through the liquid phase manifold C1. At this time, the pressure of the liquid carbon dioxide is about 43 barg and the temperature is +30℃. The pressure is adjusted by the second pressure regulating valve 20 to control the pressure to be about 0.5 bar higher than the pressure of the intermediate-pressure storage tank 1, in order to overcome the pressure drop loss of the ship's pipeline. The liquid carbon dioxide after depressurization is further cooled to about -30℃ by the intermediate-pressure desuperheating device 21 and injected into the intermediate-pressure storage tank 1 through the liquid inlet pipe L2.

[0103] During this process, in order to control the pressure rise in medium-pressure storage tank 1 due to the increase in liquid level and to prevent the pressure in medium-pressure storage tank 1 from exceeding its design pressure (19 barg), a portion of the excess gaseous carbon dioxide in medium-pressure storage tank 1 needs to be returned to the storage shore station through the gas phase manifold C2, as described in method S3-4. If the storage shore station does not receive the return of gaseous carbon dioxide, there is no need to connect the gas phase manifold C2, as described in method S3-5.

[0104] To control the pressure rise in intermediate-pressure storage tank 1 caused by the increase in liquid level and to prevent the pressure in intermediate-pressure storage tank 1 from exceeding its design pressure (19 barg), a portion of the excess gaseous carbon dioxide in intermediate-pressure storage tank 1 needs to be returned to the storage shore station via gas phase manifold C2. The specific operation is as follows: When the first pressure sensor 5 detects that the pressure in intermediate-pressure storage tank 1 has risen to 18 barg, an alarm signal is triggered. The operator starts gas compressor 27 to pressurize the excess volatile gas in intermediate-pressure storage tank 1 to a level slightly higher than the storage pressure of the intermediate-pressure storage shore station, approximately 45 bar. The pressurized gaseous carbon dioxide is then returned to the intermediate-pressure storage shore station via gas phase manifold C2. If the storage shore station does not receive the return of gaseous carbon dioxide, there is no need to connect gas phase manifold C2. The specific operation is as follows: The pressurized gaseous carbon dioxide is liquefied via liquefaction device 29 and then returned to the tank.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A liquid cargo transfer system for a medium pressure bulk liquid carbon dioxide carrier, characterized in that, The system comprises a medium-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 gas-phase header, a gas header, a liquid inlet pipe and a liquid outlet pipe, wherein The medium-pressure storage tank is used for storing liquid carbon dioxide at a medium pressure; The delivery pump is connected with the liquid outlet pipe and used for delivering the liquid carbon dioxide in the medium-pressure storage tank to the outside; The external delivery system comprises at least one of a low-pressure external delivery system, a medium-pressure external delivery system and a high-pressure external delivery system, and the input end of the external delivery system is connected with the liquid outlet pipe and used for delivering the liquid carbon dioxide to storage stations at different storage pressures; The input end of the self-evaporation pressure maintaining system is connected with the liquid outlet pipe, and the output end of the self-evaporation pressure maintaining system is connected with the gas header, and the self-evaporation pressure maintaining system is used for controlling the pressure in the medium-pressure storage tank when the liquid carbon dioxide is delivered to the outside; The input end of the injection system is connected with the liquid-phase header, and the output end of the injection system is connected with the liquid inlet pipe, and the injection system is used for injecting the liquid carbon dioxide in the storage stations at different storage pressures into the medium-pressure storage tank; the injection system comprises 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 with the liquid inlet pipe and the gas header, respectively; The liquid-phase header is connected with the storage stations and used for receiving or outputting the liquid carbon dioxide; The gas-phase header is used for receiving or outputting the gaseous carbon dioxide; The storage stations comprise at least one of a low-pressure storage station, a medium-pressure storage station and a high-pressure storage station.

2. A liquid cargo transfer system for a ship for the storage and transport of liquid carbon dioxide under medium pressure as claimed in claim 1, characterized in that The low-pressure external delivery system, the medium-pressure external delivery system and the high-pressure external delivery system are arranged side by side, and the output ends of the low-pressure external delivery system, the medium-pressure external delivery system and the high-pressure external delivery system are connected with the liquid-phase header, respectively; Or / and the medium / high-pressure injection system and the low-pressure injection system are connected in parallel in the injection system; Or / and the liquid-phase header is connected with the storage stations through a connecting loading / unloading facility; The gas-phase header is connected with a gas delivery facility and connected with the storage stations through the gas delivery facility; Or / and the input end of the liquid inlet pipe is connected with the output end of the injection system, and the opening of the output end of the liquid inlet pipe is arranged in the medium-pressure storage tank; the input end of the liquid inlet pipe is also connected with a liquefied back-to-tank pipe of the volatile gas delivery and treatment system; Or / and the opening of the gas header connected with the medium-pressure storage tank is arranged at the top of the medium-pressure storage tank; Or / and the medium-pressure storage tank adopts a C-shaped storage tank, and the number of the medium-pressure storage tanks is greater than or equal to one; Or / and the delivery pump is installed in the medium-pressure storage tank, and the outlet of the delivery pump is connected with the liquid outlet pipe.

3. A liquid cargo transfer system for a ship for the storage and transport of liquid carbon dioxide under medium pressure as claimed in claim 1, characterized in that The low-pressure delivery system comprises a second isolation valve, a pressure reducing valve, a second pressure sensor, a low-pressure temperature reducing device and a second check valve; wherein the second isolation valve, the pressure reducing valve, the second pressure sensor, the low-pressure temperature reducing device and the second check valve are arranged on a low-pressure delivery pipeline of the low-pressure delivery system, the second isolation valve is used to control the opening and closing of the low-pressure delivery pipeline; the pressure reducing valve is used to reduce the pressure of the liquid carbon dioxide in the low-pressure delivery system to an acceptable pressure of a low-pressure storage station; the second pressure sensor is used to control the pressure reduction value of the pressure reducing valve, and the set value can be adjusted according to the actual input pressure required by the low-pressure storage station; the low-pressure temperature reducing device is used to reduce the temperature of the liquid carbon dioxide after pressure reduction to an acceptable temperature of the low-pressure storage station, and the outlet of the second check valve is connected with a liquid-phase collecting pipe to prevent liquid backflow. The medium-pressure delivery system comprises a first isolation valve, a first pressure regulating valve and a first check valve; wherein the first isolation valve, the first pressure regulating valve and the first check valve are arranged on a medium-pressure delivery pipeline of the medium-pressure delivery system, the first isolation valve is used to control the opening and closing of the medium-pressure delivery pipeline; the first pressure regulating valve is used to control the pressure of the liquid carbon dioxide in the medium-pressure delivery system; and the outlet of the first check valve is connected with the liquid-phase collecting pipe to prevent liquid backflow. The high-pressure delivery system comprises a third isolation valve, a high-pressure booster pump, a high-pressure temperature increasing device and a third check valve; wherein the third isolation valve, the high-pressure booster pump, the high-pressure temperature increasing device and the third check valve are arranged on a high-pressure delivery pipeline of the high-pressure delivery system, the third isolation valve is used to control the opening and closing of the high-pressure delivery pipeline; 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 liquid carbon dioxide after pressure increase; and the outlet of the third check valve is connected with the liquid-phase collecting pipe to prevent liquid backflow.

4. A liquid cargo transfer system for a ship for the storage and transport of liquid carbon dioxide under medium pressure as claimed in claim 3, characterized in that The low-pressure temperature reducing device comprises a low-pressure heat exchanger, a first refrigerant unit and a low-pressure temperature sensor; wherein the low-pressure heat exchanger comprises a plate heat exchanger or a shell-and-tube heat exchanger, is used to exchange heat between the liquid carbon dioxide after pressure reduction and the refrigerant provided by the first refrigerant unit, so as to reduce the temperature of the liquid carbon dioxide after pressure reduction; the low-pressure temperature sensor is installed on a downstream pipeline of the low-pressure heat exchanger, and is used to monitor the temperature of the liquid carbon dioxide in the low-pressure delivery pipeline; the first refrigerant unit is used to provide refrigerant for the low-pressure heat exchanger; and the refrigerant is propane or propylene; Or / and the high-pressure temperature increasing device comprises a high-pressure heater, a first 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, is used to monitor the temperature of the liquid carbon dioxide after pressure increase, and controls the opening degree of the first temperature control valve; and the first temperature control valve is used to adjust the amount of heat exchange medium entering the high-pressure heater, so as to control the temperature of the liquid carbon dioxide passing through the high-pressure heat exchanger.

5. A liquid cargo transfer system for a ship for the storage and transport of liquid carbon dioxide under medium pressure according to claim 4, characterized in that The first temperature control valve comprises a pneumatic temperature control valve, an electric temperature control valve or a hydraulic temperature control valve, and the opening degree of the first temperature control valve is controlled by the medium pressure temperature sensor; the high pressure heater is a plate heater or a shell and tube heater; and the heat exchange medium comprises any one of seawater, freshwater, steam, hot oil and glycol water.

6. The liquid cargo transfer system for a ship for the storage and transport of medium pressure liquid carbon dioxide as defined in claim 1, wherein, The input end of the medium / high pressure injection system and the low pressure injection system is connected with the liquid phase header through a first remote control three-way valve, and the output end is connected with a liquid tank inlet pipe; wherein the first remote control three-way valve has a first interface, a second interface and a third interface, wherein the first interface is connected with the liquid phase header; the second interface is connected with the medium / high pressure injection system; and the third interface is connected with the low pressure injection system. The low pressure injection system comprises a medium pressure booster pump and a medium pressure temperature increasing device; the input end of the medium pressure booster pump is connected with the third interface of the first remote control three-way valve, and the output end is connected with the medium pressure temperature increasing device, which is used to increase the pressure of the low pressure liquid carbon dioxide from the low pressure storage shore station; and the medium pressure temperature increasing device is used to increase the temperature of the liquid carbon dioxide after being boosted in pressure. The medium / high pressure injection system comprises a second pressure regulating valve and a medium pressure temperature decreasing device; the input end of the medium / high pressure injection system is connected with the second interface of the first remote control three-way valve, and the output end is connected with the liquid tank inlet pipe; the second pressure regulating valve is used to regulate the pressure of the liquid carbon dioxide injected into the medium / high pressure injection system to meet the storage requirements of the medium pressure storage tank; and the medium pressure temperature decreasing device is used to control the temperature of the input liquid carbon dioxide after being regulated in pressure.

7. A liquid cargo transfer system for a ship for the storage and transport of liquid carbon dioxide under medium pressure as claimed in claim 6, characterized in that The medium pressure temperature increasing device comprises a medium pressure heater, a second temperature control valve and a first medium pressure temperature sensor; wherein the first medium pressure temperature sensor is installed at the outlet of the medium pressure heater, which is used to monitor the temperature of the liquid carbon dioxide after being boosted in pressure and control the opening degree of the second temperature control valve; the second temperature control valve is used to regulate the amount of heat exchange medium entering the medium pressure heater, so as to control the temperature of the liquid carbon dioxide passing through the medium pressure heat exchanger; and the heat exchange medium is glycol water or other low freezing point liquid. Or / and the medium pressure temperature decreasing device comprises a medium pressure heat exchanger, a second refrigerant unit, a temperature control three-way valve and a second medium pressure temperature sensor; wherein the temperature control three-way valve has a linear regulating capacity; the second medium pressure temperature sensor is used to monitor the temperature of the liquid carbon dioxide and control the flow of the liquid carbon dioxide passing through the medium pressure heat exchanger by adjusting the opening degree of the temperature control three-way valve, so as to control the temperature of the mixed liquid carbon dioxide to meet the design requirements; the second refrigerant unit controls the temperature of the heat exchange medium through a secondary heat exchange cycle to provide pre-cooled refrigerant for the medium pressure heat exchanger; and the refrigerant is propane or propylene.

8. A liquid cargo transfer system for a ship for the storage and transport of liquid carbon dioxide under medium pressure as claimed in claim 1, characterized in that, The self-evaporation pressure maintaining system comprises a pressure control valve, an evaporation vaporizer 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 on the top of the medium-pressure storage tank and used for monitoring the pressure of the gas phase space on the top of the medium-pressure storage tank; the evaporation vaporizer is used for evaporating liquid carbon dioxide into gaseous carbon dioxide and returning the gaseous carbon dioxide to the medium-pressure storage tank through a gas collecting pipe; The volatile gas delivery and processing system comprises a second remote control three-way valve, a gas compressor, a liquefaction device, a third pressure regulating valve, a fourth pressure regulating valve, a liquefied back cabin pipe, a gas return shore pipe and a gas return pipe; wherein the second remote control three-way valve is used for controlling the flow direction of the volatile gas and has a fourth interface, a fifth interface and a sixth interface, wherein the fourth interface is connected with the gas collecting pipe; the fifth interface is connected with the liquefied back cabin pipe; the sixth interface is connected with the outlet of the gas compressor; the third pressure regulating valve is used for controlling the pressure of the gaseous carbon dioxide returned from the medium-pressure storage tank to the shore station; the fourth pressure regulating valve is used for controlling the pressure of the gaseous carbon dioxide returned from the shore station to the medium-pressure storage tank.

9. A liquid cargo transfer system for a ship for the storage and transport of liquid carbon dioxide under medium pressure as claimed in claim 8, characterized in that The gas inlet side of the gas compressor is connected with the gas collecting pipe through a sixth isolation valve, and the outlet of the gas compressor is connected with the sixth interface of the second remote control three-way valve; The volatile gas compressed by the gas compressor can be output through the fourth interface of the second remote control three-way valve to return to the receiving device of the storage shore station through the gas collecting pipe, or can be connected with the liquefied back cabin pipe through the fifth interface of the second remote control three-way valve, and then returned to the medium-pressure storage tank after being liquefied by the liquefaction device; Or / and the liquefied back cabin pipe is provided with a seventh isolation valve; a liquefaction device is installed downstream of the seventh isolation valve; the liquefaction device comprises a liquefaction heat exchanger and a refrigeration unit; wherein the liquefaction heat exchanger is used for cooling and liquefying the compressed gaseous carbon dioxide; and the refrigeration unit is used for providing refrigerant for the liquefaction heat exchanger; Or / and the gas return shore pipe is provided with a third pressure regulating valve, which adjusts the pressure of the gaseous carbon dioxide from the medium-pressure storage tank; the gas inlet of the third pressure regulating valve is connected with the gas collecting pipe through a fourth isolation valve, and the gas outlet is connected with the gas collecting pipe through a fifth isolation valve; Or / and the gas return pipe is provided with a fourth pressure regulating valve, which adjusts the pressure of the gaseous carbon dioxide from the shore station; the gas inlet of the fourth pressure regulating valve is connected with the gas collecting pipe through a ninth isolation valve, and the gas outlet is connected with the gas collecting pipe through an eighth isolation valve.

10. A transfer method for a medium-pressure storage and transport liquid carbon dioxide ship, characterized by, The method for transferring the liquid cargo of the medium-pressure storage and transportation liquid carbon dioxide ship by using the liquid cargo transfer system according to any one of claims 1-9 comprises the following steps: S1, outputting liquid carbon dioxide to the storage shore station, comprising the following steps: S11, connecting the liquid phase collecting pipe and the gas phase collecting pipe with the unloading facilities and the gas delivery facilities of the storage shore station respectively, selecting an output system matched with the storage pressure of the storage shore station, and connecting the output system with the liquid cabin discharge pipe; S12, outputting the liquid carbon dioxide in the medium-pressure storage tank through a delivery pump and delivering the liquid carbon dioxide to the storage shore station through the output system; S2, injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank, comprising the following steps: S21, connecting the liquid-phase header and the gas-phase header to the loading facility and the gas delivery facility of the storage shore station respectively, and selecting the flow path of the first remote control three-way valve according to the storage pressure of the storage shore station; S22, making the liquid carbon dioxide from the storage shore station flow through the liquid-phase header and the first remote control three-way valve in sequence, entering the injection system, adjusting the pressure and temperature of the carbon dioxide in the injection system, and then injecting the medium-pressure storage tank; S3, volatile gas delivery and treatment, comprising at least one of the following steps: S31, in the process of delivering liquid carbon dioxide from the medium-pressure storage tank to the storage shore station, to avoid the pressure in the medium-pressure storage tank being lower than the minimum design pressure of the storage tank, connecting the gas collection pipe to the gas-phase space of the storage shore station through the gas-phase header, and delivering the gaseous carbon dioxide of the storage shore station to the medium-pressure storage tank through the gas collection pipe under the action of the pressure difference, i.e., gas back feeding, the pressure difference being formed by the pressure difference between the storage tank of the storage shore station and the medium-pressure storage tank, or being formed by using the compressor of the storage shore station to pressurize the back-fed gaseous carbon dioxide; S32, in the process of injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank, to avoid the pressure in the medium-pressure storage tank being higher than the design pressure of the medium-pressure storage tank, a part of the excess gaseous carbon dioxide in the medium-pressure storage tank needs to be back-fed to the storage shore station through the gas-phase header; specifically, the gaseous carbon dioxide in the medium-pressure storage tank is back-fed to the storage shore station through the gas-phase header under the action of the pressure difference, i.e., gas back to shore, the pressure difference being formed by the pressure difference between the medium-pressure storage tank and the storage tank of the storage shore station, or being formed by using the gas compressor on the ship to pressurize the gaseous carbon dioxide delivered to the storage shore station; S33, in step S32, if the storage shore station does not receive the back-fed gaseous carbon dioxide, the excess gaseous carbon dioxide in the medium-pressure storage tank is extracted and pressurized by the gas compressor, the gaseous carbon dioxide pressurized by the gas compressor is converted into liquid carbon dioxide in the liquefaction device, and then injected into the medium-pressure storage tank; S34, in the process of delivering liquid carbon dioxide from the medium-pressure storage tank to the storage shore station, if the pressure in the medium-pressure storage tank rises, to avoid the pressure in the medium-pressure storage tank being higher than the design pressure of the medium-pressure storage tank, the operation of step S32 is adopted; i.e., the gaseous carbon dioxide in the medium-pressure storage tank is back-fed to the storage shore station through the gas-phase header under the action of the pressure difference; S35, in the process of injecting liquid carbon dioxide from the storage shore station into the medium-pressure storage tank, if the pressure in the medium-pressure storage tank decreases, to avoid the pressure in the medium-pressure storage tank being lower than the minimum design pressure of the storage tank, the operation of step S31 is adopted; i.e., connecting the gas collection pipe to the gas-phase space of the storage shore station through the gas-phase header, and delivering the gaseous carbon dioxide of the storage shore station to the medium-pressure storage tank through the gas collection pipe under the action of the pressure difference, i.e., gas back feeding; S4, self-evaporation pressure maintenance treatment, comprising the following steps: When the pressure of the gas phase space in the medium-pressure storage tank drops to a low-pressure set value, the pressure control valve is opened, the self-evaporation pressure maintaining system is communicated with the liquid out-of-cabin pipe, and part of the exported liquid carbon dioxide enters the self-evaporation pressure maintaining pipe, is gasified through the evaporation gasifier, and is returned to the medium-pressure storage tank through the gas collecting pipe; when the pressure of the gas phase space in the medium-pressure storage tank rises to a high-pressure set value, the pressure control valve is closed, and the self-evaporation pressure maintaining process ends.

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