Liquefied gas loading system and method for liquefied gas carrier

Abstract

A liquefied gas loading system for a liquefied gas carrier and a liquefied gas loading method using the same are disclosed, comprising: a plurality of cargo tanks; a loading line for supplying liquefied gas from a terminal to a cargo tank; a vapor line for discharging evaporated gas generated in a cargo tank; a heat exchanger for receiving and heat-exchanging evaporated gas generated in one of the plurality of cargo tanks and inert gas discharged from another of the plurality of cargo tanks; an evaporated gas supply line connected between the vapor line and the heat exchanger for delivering evaporated gas to the heat exchanger; an evaporated gas discharge line connected between the heat exchanger and the vapor line for discharging evaporated gas heat-exchanged in the heat exchanger from the heat exchanger; an inert gas supply line connected between the loading line and the heat exchanger for delivering inert gas to the heat exchanger; and an inert gas discharge line connected between the heat exchanger and the loading line for discharging inert gas heat-exchanged in the heat exchanger from the heat exchanger.

Description

Technology Field

[0001] The present invention relates to a liquefied gas loading system and method for a liquefied gas carrier, and more specifically, to a liquefied gas loading system and method for a liquefied gas carrier that can optimally utilize the cold energy of the liquefied gas when loading liquefied gas into the liquefied gas carrier. Background Technology

[0002] A vessel transporting liquefied gas, including liquefied natural gas (hereinafter referred to as 'LNG'), is equipped with a storage tank (commonly referred to as a 'cargo tank') to store the liquefied gas and its boil-off gas (hereinafter referred to as 'BOG').

[0003] In these cargo tanks, a gas treatment process is performed before loading liquefied gas. The gas treatment process may include an inerting process that supplies inert gas into the cargo tank, a gasssing up process that supplies heated liquefied gas into the cargo tank to replace the inert gas, and a cool-down process to lower the internal temperature of the cargo tank to a certain level.

[0004] Inerting is the process of injecting an inert gas, such as nitrogen, into the cargo hold. This can be seen as a process designed to prevent the possibility of explosion by removing air pockets from the cargo hold. The inert gas used for inerting can be generated from an Inert Gas Generator (IGG) equipped on the ship, and consists of approximately 85% nitrogen and about 14% carbon dioxide as impurities.

[0005] The gasssing-up process is a task of replacing the inert gas filled during the inerting process with the vaporized liquefied gas by vaporizing the liquefied gas supplied from the terminal and injecting it into the cargo tank. For example, in the case of an LNG carrier, the inert gas is replaced by injecting the vaporized gas, or natural gas, generated by heating the LNG to approximately 20 to 40°C into the cargo tank, and this process can be continued until the natural gas content reaches 97 to 98% or more.

[0006] The cool-down process is a task to pre-cool the cargo tank and the liquefied gas loading line. The cool-down operation can be performed by spraying the liquefied gas supplied from the terminal through a spray nozzle provided at the top of the cargo tank.

[0007] The loading operation of loading liquefied gas into the cargo tank can be performed stably only by sequentially going through the aforementioned inerting process, gasing-up process, and cool-down process.

[0008] Meanwhile, a large amount of evaporative gas is generated during the process of loading liquefied gas into the cargo tank, and it is necessary to treat this gas to prevent the pressure in the cargo tank from rising excessively due to the evaporative gas.

[0009] Conventionally, it was common practice to return the evaporated gas generated during the loading of liquefied gas to the terminal or send it to a Gas Combustion Unit (GCU) for incineration, but this has the problem of not being able to utilize energy efficiently. The problem to be solved

[0010] The present invention aims to provide a liquefied gas loading system and method for a liquefied gas carrier that enables the optimized operation of the liquefied gas's cold energy by efficiently utilizing the evaporated gas generated during the loading of the liquefied gas without wasting it.

[0011] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0012] According to one aspect of the present invention, a liquefied gas loading system of a liquefied gas carrier may be disclosed, comprising: a plurality of cargo tanks; a loading line for supplying liquefied gas from a terminal to the cargo tanks; a vapor line for discharging evaporated gas generated in the cargo tanks; a heat exchanger for receiving and heat-exchanging evaporated gas generated in one of the plurality of cargo tanks and inert gas discharged from another of the plurality of cargo tanks; an evaporated gas supply line connected between the vapor line and the heat exchanger to deliver the evaporated gas to the heat exchanger; an evaporated gas discharge line connected between the heat exchanger and the vapor line to discharge the evaporated gas heat-exchanged in the heat exchanger from the heat exchanger; an inert gas supply line connected between the loading line and the heat exchanger to deliver the inert gas to the heat exchanger; and an inert gas discharge line connected between the heat exchanger and the loading line to discharge the inert gas heat-exchanged in the heat exchanger from the heat exchanger.

[0013] During the process of loading liquefied gas into any one of the above cargo tanks, the evaporated gas generated is supplied to the heat exchanger through the vapor line and the evaporated gas supply line, and the evaporated gas supplied to the heat exchanger is heated by heat exchange with the inert gas, and then supplied to any one of the other cargo tanks through the evaporated gas discharge line and the vapor line to be used for gas-up operations.

[0014] The inert gas present in any other cargo tank is pushed out through the loading line by the evaporated gas supplied from the heat exchanger and then supplied to the heat exchanger through the inert gas supply line, and the inert gas supplied to the heat exchanger has its temperature lowered by heat exchange with the evaporated gas and then is supplied to another cargo tank among the plurality of cargo tanks through the inert gas discharge line and the loading line to be used for pre-cooling operations.

[0015] The above loading line includes a main loading line connected from the terminal into the interior of the liquefied gas carrier, and a plurality of branch loading lines branching from the main loading line and connected to each of the plurality of cargo tanks, and the vapor line may include a plurality of branch vapor lines provided for each of the plurality of cargo tanks, and a main vapor line into which the plurality of branch vapor lines are integrated.

[0016] A compressor for accelerating fluid flow may be installed on the above inert gas supply line.

[0017] The above liquefied gas is liquid hydrogen, and nitrogen gas may be used as the above inert gas.

[0018] A liquefied gas loading system of a liquefied gas carrier according to one aspect of the present invention further comprises: a control valve installed on the evaporated gas supply line upstream of the heat exchanger to control the amount of evaporated gas supplied to the heat exchanger; and a temperature sensor installed on the inert gas discharge line downstream of the heat exchanger, wherein the control valve can be controlled based on the temperature measured by the temperature sensor.

[0019] Meanwhile, according to another aspect of the present invention, a method for loading liquefied gas of a liquefied gas carrier having a plurality of cargo tanks may be provided, comprising: an inerting step of injecting an inert gas into the interior of the plurality of cargo tanks; a loading step of supplying liquefied gas from a terminal to one of the plurality of cargo tanks; and a gasing up step of supplying evaporated gas generated during the process of loading liquefied gas into one of the cargo tanks to another of the plurality of cargo tanks to replace the inert gas present inside the other of the cargo tanks, wherein the evaporated gas generated in one of the cargo tanks is heated by heat exchange with the inert gas discharged from the other of the cargo tanks and then supplied to the other of the cargo tanks.

[0020] A method for loading liquefied gas on a liquefied gas carrier according to another aspect of the present invention further comprises a pre-cooling step of supplying an inert gas discharged from any other cargo tank to any other cargo tank among the plurality of cargo tanks to lower the temperature inside any other cargo tank, and the inert gas discharged from any other cargo tank may be supplied to any other cargo tank after being cooled by heat exchange with evaporated gas generated in any one cargo tank.

[0021] The above loading step, the above gasing-up step, and the above pre-cooling step can be performed at least partially simultaneously. Effects of the invention

[0022] According to the liquefied gas loading system and method of the liquefied gas carrier of the present invention, by utilizing the cold energy of the evaporated gas generated during the loading of liquefied gas for gas-up and pre-cooling operations of other cargo holds, the wasted evaporated gas is minimized, energy optimization is possible by efficiently utilizing the cold energy of the liquefied gas, and the efficiency of the liquefied gas loading operation can be maximized.

[0023] The effects of the present invention are not limited to those described above, and other unmentioned effects will be clearly understood from the description below. Brief explanation of the drawing

[0024] FIG. 1 is a schematic diagram showing a liquefied gas loading system of a liquefied gas carrier according to the present invention. FIG. 2 is a diagram showing the fluid flow when loading liquefied gas into the first cargo tank in the liquefied gas loading system of a liquefied gas carrier according to the present invention. FIG. 3 is a diagram showing the fluid flow when loading liquefied gas into the second cargo tank in the liquefied gas loading system of a liquefied gas carrier according to the present invention. FIG. 4 is a diagram showing the fluid flow when loading liquefied gas into the third cargo tank in the liquefied gas loading system of a liquefied gas carrier according to the present invention. Specific details for implementing the invention

[0025] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are presented to sufficiently convey the concept of the present invention to those skilled in the art to which the present invention pertains. The present invention is not limited to the embodiments presented herein and may be embodied in other forms. In order to clarify the present invention, the drawings may omit the illustration of parts unrelated to the description and may slightly exaggerate the size of components to aid understanding.

[0026] FIG. 1 is a schematic diagram showing a liquefied gas loading system of a liquefied gas carrier according to the present invention. Referring to FIG. 1, a plurality of cargo tanks (10 to 40) may be provided in the liquefied gas carrier according to the present invention. In this embodiment, four cargo tanks (10, 20, 30, 40) are provided as a preferred example, but the present invention is not limited thereto. The cargo tanks (10 to 40) store liquefied gas while maintaining an insulating state and may be composed of membrane-type tanks or independent tanks.

[0027] In addition, the liquefied gas that the liquefied gas carrier according to the present invention transports may include various liquefied gases that can be stored in a liquefied state at low temperatures, such as liquefied ethane gas, liquefied ethylene gas, and liquefied carbon dioxide, in addition to LNG and liquefied petroleum gas (LPG).

[0028] However, the present invention is highly useful when a liquefied gas that is cooled to a temperature below a predetermined level and possesses sufficient cold energy is applied. As will be described later, since the present invention aims to utilize the cold energy of the liquefied gas through heat exchange with an inert gas used in the inerting operation of the cargo tank, it is intended to use a liquefied gas having a boiling point lower than the boiling point (-196°C) of nitrogen gas, which is mainly used as an inert gas. Therefore, the present invention proposes the application of liquid hydrogen as a preferred example of a liquefied gas for this purpose.

[0029] The boiling point of liquid hydrogen is approximately -253°C, and the temperature of the evaporated liquid hydrogen gas is also approximately -200°C; thus, it possesses sufficient cold energy, which can be utilized as a means to improve the energy efficiency of the liquid gas loading system.

[0030] That is, the liquefied gas carrier according to the present invention may be a liquefied hydrogen carrier, and nitrogen gas may be used as the inert gas used for the inerting operation of the cargo tanks (10-40) for storing liquefied hydrogen.

[0031] A loading system for a liquefied gas carrier according to the present invention comprises: a loading line provided for loading liquefied gas from a land terminal to a cargo tank (10-40); a vapor line for discharging boil-off gas (BOG) generated in the cargo tank (10-40); a heat exchanger (100) that receives and heat-exchanges boil-off gas generated in one of the plurality of cargo tanks (10-40) (a cargo tank where liquefied gas loading is performed) and inert gas discharged from another of the plurality of cargo tanks (10-40) (a cargo tank where gas-up operations are performed); a boil-off gas supply line (L31) connected from the vapor line to the heat exchanger (100) to transfer boil-off gas generated in one of the plurality of cargo tanks (10-40) to the heat exchanger (100); and a boil-off gas discharge line (L32) connected from the heat exchanger (100) to the vapor line to transfer boil-off gas that has been heat-exchanged in the heat exchanger (100) to the vapor line. It may be configured to include an inert gas supply line (L41) connected from a loading line to a heat exchanger (100) to transfer inert gas discharged from any one of a plurality of cargo tanks (10 to 40) to the heat exchanger (100), and an inert gas discharge line (L42) connected from the heat exchanger (100) to a loading line to transfer inert gas heat-exchanged in the heat exchanger (100) to the loading line.

[0032] The loading line may include a main loading line (L10) connected from a land terminal into the interior of the liquefied gas carrier according to the present invention, and first to fourth loading lines (L11 to L14) branched from the main loading line (L10) and connected to each cargo tank (10 to 40).

[0033] The vapor line may include first to fourth vapor lines (L21 to L24) provided for each cargo tank (10 to 40) and a main vapor line (L20) to which the first to fourth vapor lines (L21 to L24) are integrated. The first to fourth vapor lines (L21 to L24) may have inlets formed at the top of each cargo tank (10 to 40) to discharge evaporated gas generated inside each cargo tank (10 to 40).

[0034] The heat exchanger (100) receives and exchanges heat with evaporated gas generated from one of the plurality of cargo tanks (10 to 40) and inert gas discharged from another of the plurality of cargo tanks (10 to 40). Here, the cargo tank where the evaporated gas is generated is a cargo tank where liquefied gas loading is performed, and the evaporated gas from which inert gas is discharged may be a cargo tank where gas-up operations are performed.

[0035] Specifically, the heat exchanger (100) can receive evaporated gas generated in a cargo tank where liquefied gas loading is performed among a plurality of cargo tanks (10 to 40) through a vapor line and an evaporated gas supply line (L31), and on the other side, receive inert gas discharged from a cargo tank where gas-up work is performed among a plurality of cargo tanks through a loading line and an inert gas supply line (L41) to mutually exchange heat.

[0036] In this embodiment, the evaporative gas supply line (L31) can be connected to the heat exchanger (100) from a point between the first vapor line (L21) and the second vapor line (L22) on the main vapor line (L20).

[0037] In addition, in this embodiment, the inert gas supply line (L41) can be connected to the heat exchanger (100) from a point between the second loading line (L12) and the third loading line (L13) on the main loading line (L10).

[0038] The evaporated gas that has been heat-exchanged in the heat exchanger (100) can be supplied to another cargo tank through the evaporated gas discharge line (L32) and the vapor line. The evaporated gas, whose temperature has been slightly raised (heated) by heat exchange with the inert gas in the heat exchanger (100), can be supplied to another cargo tank and utilized to perform a 'gas-up operation'. In this way, in the present invention, the vapor line may not only serve the role of discharging the evaporated gas generated in the cargo tanks (10-40), but also serve the role of supplying the evaporated gas that has been heat-exchanged in the heat exchanger (100) to the cargo tanks (10-40).

[0039] In this embodiment, the evaporative gas discharge line (L32) can be connected from the heat exchanger (100) to a point between the third vapor line (L23) and the fourth vapor line (L24) on the main vapor line (L20).

[0040] Additionally, the inert gas that has been heat-exchanged in the heat exchanger (100) can be supplied to another cargo tank through the inert gas discharge line (L42) and the loading line. The inert gas, whose temperature has been lowered (cooled) by heat exchange with the evaporated gas in the heat exchanger (100), can be supplied to another cargo tank and utilized to perform a 'pre-cooling operation'. Thus, in the present invention, the loading line may not only serve the role of loading liquefied gas into the cargo tanks (10-40), but also serve the role of supplying the inert gas that has been heat-exchanged in the heat exchanger (100) to the cargo tanks (10-40).

[0041] In this embodiment, the inert gas discharge line (L42) can be connected from the heat exchanger (100) to a point between the third loading line (L13) and the fourth loading line (L14) on the main loading line (L10).

[0042] Meanwhile, among the plurality of cargo tanks (10 to 40) above, the cargo tank where the gas-up operation is performed may be a cargo tank that receives heat-exchanged evaporated gas from the heat exchanger (100). The cargo tank where the gas-up operation is performed receives heat-exchanged evaporated gas from the heat exchanger (100), and the inert gas that was previously present inside the cargo tank is pushed out and discharged by the supply of evaporated gas and is delivered to the heat exchanger (100) side through the loading line and the inert gas supply line (L41).

[0043] Meanwhile, in this system, the fluid flow of the evaporated gas or inert gas can be formed by the force of the liquefied gas being loaded. However, since high pressure is generally not formed when the liquefied gas is loaded, the fluid flow may not be smooth or the speed of the process may be slow. Accordingly, the present invention may install a compressor (200) on the inert gas supply line (L41) for the purpose of accelerating the fluid process, and the inert gas discharged from the cargo tank (10~40) where the gas-up operation is performed can be delivered to the heat exchanger (100) with the flow accelerated by the compressor (200).

[0044] Hereinafter, the operation of the liquefied gas loading system of a liquefied gas carrier according to the present invention will be explained with reference to FIGS. 2 to 4.

[0045] A plurality of cargo tanks (10 to 40) provided in a liquefied gas carrier according to the present invention shall be named the first cargo tank (10), the second cargo tank (20), the third cargo tank (30), and the fourth cargo tank (40) according to the order in which liquefied gas is loaded. That is, the loading of liquefied gas is carried out sequentially starting from the first cargo tank (10).

[0046] Prior to loading liquefied gas into a plurality of cargo tanks (10 to 40) provided in the liquefied gas carrier according to the present invention, an inerting operation may be performed on all cargo tanks (10 to 40). Additionally, for the first cargo tank (10) to be loaded with liquefied gas first, a gas-up operation and a cool-down operation may be further performed. Therefore, immediately before the loading of liquefied gas into the first cargo tank (10), the first cargo tank (10) is mostly filled with vaporized liquefied gas, and the interiors of the remaining cargo tanks (20 to 40), excluding the first cargo tank (10), are filled with inert gas.

[0047] FIG. 2 illustrates the fluid flow when liquefied gas is loaded into the first cargo tank (10). Below, with reference to FIG. 2, we will examine the operation of the present system when liquefied gas is loaded into the first cargo tank (10).

[0048] Referring to FIG. 2, when the loading operation of liquefied gas into the first cargo tank (10) is initiated, liquefied gas is supplied from the land terminal to the first cargo tank (10) through the main loading line (L10) and the first loading line (L11).

[0049] At this time, a large amount of evaporated gas is generated during the process of loading liquefied gas into the first cargo tank (10). The evaporated gas generated in the first cargo tank (10) is transferred to the heat exchanger (100) through the evaporated gas supply line (L31) via the first vapor line (L21) and the main vapor line (L20).

[0050] The evaporated gas delivered to the heat exchanger (100) is heat-exchanged with the inert gas supplied through the inert gas supply line (L41) as described below, and then supplied to the second cargo tank (20) through the evaporated gas discharge line (L32), the main vapor line (L20), and the second vapor line (L22).

[0051] The vaporized gas supplied to the second cargo tank (20) through the second vapor line (L22) is heated by heat exchange with an inert gas and supplied to the upper part of the second cargo tank (20) to perform a gas-up operation.

[0052] The existing inert gas present in the second cargo tank (20) is pushed out through the second loading line (L12), which has an inlet formed at the bottom of the second cargo tank (20), by the heat-exchanged evaporated gas supplied to the top of the second cargo tank (20). The inert gas discharged through the second loading line (L12) is transferred to the heat exchanger (100) through the main loading line (L10) and the inert gas supply line (L41) and exchanges heat with the evaporated gas discharged from the first cargo tank (10) as described above.

[0053] The inert gas that has been heat-exchanged with the evaporated gas in the heat exchanger (100) can be supplied to the third cargo tank (30) in a cooled state. At this time, the cooled inert gas is supplied from the heat exchanger (100) to the lower part of the third cargo tank (30) through the inert gas discharge line (L42), the main loading line (L10), and the third loading line (L13). At this time, the evaporated gas of the liquefied gas (liquid hydrogen) supplied to the heat exchanger (100) has a temperature of approximately -200°C, so it can sufficiently cool the inert gas (nitrogen gas) to be suitable for use as a pre-cooling agent for the third cargo tank (30).

[0054] In this way, liquefied gas is supplied to the first cargo tank (10) through the main loading line (L10) and the first loading line (L11); evaporated gas is supplied from the first cargo tank (10) to the heat exchanger (100) through the first vapor line (L21), the main vapor line (L20), and the evaporated gas supply line (L31); evaporated gas is transferred from the heat exchanger (100) to the second cargo tank (20) through the evaporated gas discharge line (L32), the main vapor line (L20), and the second vapor line (L22); inert gas is supplied from the second cargo tank (20) to the heat exchanger (100) through the second loading line (L12), the main loading line (L10), and the inert gas supply line (41); and from the heat exchanger (100) to the inert gas discharge line (L42), the main loading line (L10), and the third In order to form a transfer flow of inert gas to the third cargo tank (30) through the loading line (L13), valves not shown installed on the main loading line (L10) and the main vapor line (L20) can be controlled.

[0055] Meanwhile, in the very early stages when the evaporated gas generated in the first cargo tank (10) is supplied to the second cargo tank (20) through the heat exchanger (100), there may not be a heat exchange medium present. However, as the evaporated gas generated in the first cargo tank (10) is supplied to the second cargo tank (20), when the inert gas pushed out and discharged from the second cargo tank (20) reaches the heat exchanger (100), heat exchange occurs between the evaporated gas delivered from the first cargo tank (10) and the inert gas delivered from the second cargo tank (20).

[0056] Until the loading of the first cargo tank (10) is completed, the evaporated gas generated in the first cargo tank (10) can be supplied to the second cargo tank (20) through the heat exchanger (100) and used for the gas-up operation. If the amount of evaporated gas generated in the first cargo tank (10) is insufficient to achieve the gas-up operation of the second cargo tank (20) until the loading of the first cargo tank (10) is completed, the gas-up operation can be completed by additionally supplying the insufficient amount of heated liquefied gas from the land terminal to the second cargo tank (20) through the main loading line (L10) after the loading of the first cargo tank (10) is completed.

[0057] The pre-cooling operation for the third cargo tank (30) is sufficient to be performed only until the gas-up operation of the second cargo tank (20) is completed, and there is no need to perform it additionally thereafter to satisfy any criteria.

[0058] It should be noted here that the pre-cooling operation for the third cargo tank (30) should be distinguished from the cool-down operation. While the cool-down operation is performed by spraying the same liquefied gas (in this invention, liquefied hydrogen) as the liquefied gas to be loaded onto the top of the cargo tank, the pre-cooling operation in this invention is intended to lower the temperature of the cargo tank once more in advance by using an inert gas that has been cooled by heat exchange with the evaporated gas of the liquefied gas.

[0059] In other words, the pre-cooling operation using cooled inert gas in the present invention can be seen as a preliminary operation that lowers the temperature of the cargo tank in advance before performing the cool-down operation, thereby increasing the efficiency of the subsequent cool-down operation and saving energy consumed in the cool-down operation.

[0060] Therefore, after the pre-cooling operation for the third cargo tank (30), a gas-up operation to remove evaporated gas and a cool-down operation to lower the temperature of the cargo tank must be performed again. As described later, the gas-up operation for the third cargo tank (30) can be performed using the evaporated gas generated from the second cargo tank (20) during the process of loading liquefied gas into the second cargo tank (20).

[0061] As described above, the evaporated gas generated during the process of loading liquefied gas into the first cargo tank (10) can be transferred to the second cargo tank (20) through the heat exchanger (100) and used for gas-up, and the inert gas discharged from the second cargo tank (20) can be transferred to the third cargo tank (30) through the heat exchanger (100) and used for pre-cooling.

[0062] The liquefied gas loading of the first cargo tank (10), the gas-up operation of the second cargo tank (20), and the pre-cooling operation of the third cargo tank (30) can be performed at least partially simultaneously.

[0063] When the liquefied gas loading of the first cargo tank (10) is completed and the gas-up operation of the second cargo tank (20) is also completed, a cool-down operation is first performed to cool the inside of the second cargo tank (20) to a predetermined temperature by injecting liquefied gas into the inside of the second cargo tank (20), and then the liquefied gas loading for the second cargo tank (20) is performed.

[0064] FIG. 3 illustrates the fluid flow when liquefied gas is loaded into the second cargo tank (20). Below, with reference to FIG. 3, we will examine the operation of the present system when liquefied gas is loaded into the second cargo tank (20).

[0065] Referring to FIG. 3, when liquefied gas loading into the second cargo tank (20) begins, liquefied gas is supplied from the land terminal to the second cargo tank (20) through the main loading line (L10) and the second loading line (L12).

[0066] At this time, a large amount of evaporative gas is generated during the process of loading liquefied gas into the second cargo tank (20). The evaporative gas generated in the second cargo tank (20) is transferred to the heat exchanger (100) through the second vapor line (22) and the main vapor line (L20) and the evaporative gas supply line (L31).

[0067] The evaporated gas delivered to the heat exchanger (100) is heat-exchanged with the inert gas supplied through the inert gas supply line (L41) as described below, and then supplied to the third cargo tank (30) through the evaporated gas discharge line (L32), the main vapor line (L20), and the third vapor line (L23).

[0068] The vaporized gas supplied to the third cargo tank (30) through the third vapor line (L23) is heated by heat exchange with an inert gas and supplied to the upper part of the third cargo tank (30) to perform a gas-up operation.

[0069] The existing inert gas present in the third cargo tank (30) is pushed out through the third loading line (L13), which has an inlet formed at the bottom of the third cargo tank (30), by the heat-exchanged evaporated gas supplied to the top of the third cargo tank (30). The inert gas discharged through the third loading line (L13) is transferred to the heat exchanger (100) through the main loading line (L10) and the inert gas supply line (L41) and exchanges heat with the evaporated gas discharged from the second cargo tank (20) as described above.

[0070] The inert gas that has been heat-exchanged with the evaporated gas in the heat exchanger (100) can be supplied to the fourth cargo tank (40) in a cooled state. At this time, the cooled inert gas is supplied from the heat exchanger (100) to the lower part of the fourth cargo tank (40) through the inert gas discharge line (L42), the main loading line (L10), and the fourth loading line (L14). At this time, the evaporated gas of the liquefied gas (liquid hydrogen) supplied to the heat exchanger (100) has a temperature of approximately -200°C, so it can sufficiently cool the inert gas (nitrogen gas) to be suitable for use as a pre-cooling agent for the fourth cargo tank (40).

[0071] In this way, the supply of liquefied gas to the second cargo tank (20) through the main loading line (L10) and the second loading line (L12), the supply of evaporated gas from the second cargo tank (20) to the heat exchanger (100) through the second vapor line (L22), the main vapor line (L20), and the evaporated gas supply line (L31), the transfer of evaporated gas from the heat exchanger (100) to the third cargo tank (30) through the evaporated gas discharge line (L32), the main vapor line (L20), and the third vapor line (L23), the supply of inert gas from the third cargo tank (30) to the heat exchanger (100) through the third loading line (L13), the main loading line (L10), and the inert gas supply line (41), the transfer of inert gas from the heat exchanger (100) to the inert gas discharge line (L42), the main loading line (L10), and the fourth In order to form a transfer flow of inert gas to the fourth cargo tank (40) through the loading line (L14), valves not shown installed on the main loading line (L10) and the main vapor line (L20) can be controlled.

[0072] Until the loading of the second cargo tank (20) is completed, the evaporated gas generated in the second cargo tank (20) can be supplied to the third cargo tank (30) through the heat exchanger (100) and used for the gas-up operation. If the amount of evaporated gas generated in the second cargo tank (20) is insufficient to achieve the gas-up operation of the third cargo tank (30) until the loading of the second cargo tank (20) is completed, the gas-up operation can be completed by additionally supplying the insufficient amount of heated liquefied gas from the land terminal to the third cargo tank (30) through the main loading line (L10) after the loading of the second cargo tank (20) is completed.

[0073] The pre-cooling operation for the fourth cargo tank (40) is sufficient to be performed only until the gas-up operation for the third cargo tank (30) is completed, and there is no need to perform it additionally thereafter to satisfy any criteria. This is because the pre-cooling operation for the fourth cargo tank (40) is merely of a preliminary nature for the cool-down operation to be performed later.

[0074] Therefore, after the pre-cooling operation for the fourth cargo tank (40), a gas-up operation to remove evaporated gas and a cool-down operation to lower the temperature of the cargo tank must be performed again. As described later, the gas-up operation for the fourth cargo tank (40) can be performed using the evaporated gas generated from the third cargo tank (30) during the process of loading liquefied gas into the third cargo tank (30).

[0075] As described above, the evaporated gas generated during the process of loading liquefied gas into the second cargo tank (20) can be transferred to the third cargo tank (30) through the heat exchanger (100) and used for gas-up, and the inert gas discharged from the third cargo tank (30) can be transferred to the fourth cargo tank (40) through the heat exchanger (100) and used for pre-cooling.

[0076] The liquefied gas loading of the second cargo tank (20), the gas-up operation of the third cargo tank (30), and the pre-cooling operation of the fourth cargo tank (40) can be performed at least partially simultaneously.

[0077] When the liquefied gas loading of the second cargo tank (20) is completed and the gas-up operation of the third cargo tank (30) is also completed, a cool-down operation is first performed to cool the inside of the cargo tank to a predetermined temperature by injecting liquefied gas into the inside of the third cargo tank (30), and then the liquefied gas loading for the third cargo tank (30) is performed.

[0078] FIG. 4 illustrates the fluid flow when liquefied gas is loaded into the third cargo tank (30). Below, with reference to FIG. 4, we will examine the operation of the present system when liquefied gas is loaded into the third cargo tank (30).

[0079] Referring to FIG. 4, when liquefied gas loading into the third cargo tank (30) begins, liquefied gas is supplied from the land terminal to the third cargo tank (30) through the main loading line (L10) and the third loading line (L13).

[0080] At this time, a large amount of evaporative gas is generated during the process of loading liquefied gas into the third cargo tank (30). The evaporative gas generated in the third cargo tank (30) is transferred to the heat exchanger (100) through the evaporative gas supply line (L31) via the third vapor line (23) and the main vapor line (L20).

[0081] The evaporated gas delivered to the heat exchanger (100) is heat-exchanged with the inert gas supplied through the inert gas supply line (L41) as described below, and then supplied to the fourth cargo tank (40) through the evaporated gas discharge line (L32), the main vapor line (L20), and the fourth vapor line (L24).

[0082] The vaporized gas supplied to the fourth cargo tank (40) through the fourth vapor line (L24) is heated by heat exchange with an inert gas and supplied to the upper part of the fourth cargo tank (40) to perform a gas-up operation.

[0083] The existing inert gas present in the fourth cargo tank (40) is pushed out by the heat-exchanged evaporated gas supplied to the upper part of the fourth cargo tank (40) through the fourth loading line (L14), which has an inlet formed at the lower part of the fourth cargo tank (40).

[0084] The inert gas discharged through the fourth loading line (L14) must be transferred from the main loading line (L10) to the heat exchanger (100), but there may be an overlap with the main loading line (L10) where liquefied gas is being loaded. Therefore, the system may additionally provide a backup inert gas supply line (L41') connected from the main loading line (L10) to the heat exchanger (100) between the third loading line (L13) and the fourth loading line (L14). In this case, the inert gas discharged through the fourth loading line (L14) can be transferred to the heat exchanger (100) through the backup inert gas supply line (L41'). Although not illustrated, a compressor may be installed on the backup inert gas supply line (41') as well as on the inert gas supply line (41).

[0085] The inert gas delivered to the heat exchanger (100) through the backup inert gas supply line (L41') exchanges heat with the evaporated gas discharged from the third cargo tank (30) as described above.

[0086] Meanwhile, in this embodiment, since there is no cargo tank following the fourth cargo tank (40), the inert gas discharged from the fourth cargo tank (40) can be released into the atmosphere.

[0087] In this way, to form a flow of liquefied gas supplied to a third cargo tank (30) through a main loading line (L10) and a third loading line (L13), a flow of evaporated gas supplied from the third cargo tank (30) to a heat exchanger (100) through a third vapor line (L23), a main vapor line (L20), and an evaporated gas supply line (L31), a flow of evaporated gas transferred from the heat exchanger (100) to a fourth cargo tank (40) through an evaporated gas discharge line (L32), a main vapor line (L20), and a fourth vapor line (L24), a flow of inert gas supplied from the fourth cargo tank (40) to a heat exchanger (100) through a fourth loading line (L14), a main loading line (L10), and a backup inert gas supply line (41'), and a flow of inert gas discharged from the heat exchanger (100) through an inert gas discharge line (L42), a main Unillustrated valves installed on the loading line (L10), the main vapor line (L20), and the inert gas discharge line (42) can be controlled.

[0088] Until the loading of the third cargo tank (30) is completed, the evaporated gas generated in the third cargo tank (30) can be supplied to the fourth cargo tank (40) through the heat exchanger (100) and used for the gas-up operation. If the amount of evaporated gas generated in the third cargo tank (30) is insufficient to achieve the gas-up operation of the fourth cargo tank (40) until the loading of the third cargo tank (30) is completed, the gas-up operation can be completed by additionally supplying the insufficient amount of heated liquefied gas from the land terminal to the fourth cargo tank (40) through the main loading line (L10) after the loading of the third cargo tank (30) is completed.

[0089] As described above, the evaporated gas generated during the process of loading liquefied gas into the third cargo tank (30) can be transferred to the fourth cargo tank (40) through the heat exchanger (100) and used for gas supply operations.

[0090] The liquefied gas loading of the third cargo tank (30) and the gas-up operation of the fourth cargo tank (40) can be performed at least partially simultaneously.

[0091] When the liquefied gas loading of the third cargo tank (30) is completed and the gas-up operation of the fourth cargo tank (40) is completed, a cool-down operation is performed in which liquefied gas is injected into the interior of the fourth cargo tank (40) to cool the interior of the cargo tank to a predetermined temperature, and then the liquefied gas loading for the fourth cargo tank (40) is performed so that the loading of liquefied gas for all cargo tanks can be completed.

[0092] Meanwhile, when the liquefied gas carrier according to the present invention is intended for transporting liquefied hydrogen and uses nitrogen gas as an inert gas, the temperature of the hydrogen gas (evaporated gas of liquefied hydrogen) supplied to the heat exchanger (100) is approximately -200°C or lower. However, since the nitrogen gas that exchanges heat with it has a boiling point of -195.8°C, there is a concern that the nitrogen gas may liquefy at the downstream end of the heat exchanger (100). If the liquefied nitrogen flows into the cargo tank, it may cause damage to the tank wall and degrade the quality of the liquefied hydrogen loaded thereafter.

[0093] In order to prevent the problem of nitrogen gas being liquefied at the downstream end of the heat exchanger (100) as described above, the present invention may configure a system to control the amount of hydrogen gas supplied to the heat exchanger (100) based on the temperature at the downstream end of the heat exchanger (100).

[0094] More specifically, the control valve (CV) installed on the evaporative gas supply line (L31) upstream of the heat exchanger (100) can perform PID control to maintain the temperature of the nitrogen gas measured by the temperature sensor (TS) installed on the inert gas discharge line (L42) downstream of the heat exchanger (100) at -190℃ or higher.

[0095] According to the liquefied gas loading system and method of the liquefied gas carrier of the present invention as described above, by utilizing the cold energy of the evaporated gas generated during the loading of liquefied gas for gas-up and pre-cooling operations of other cargo holds, the wasted evaporated gas is minimized, energy optimization is possible by efficiently utilizing the cold energy of the liquefied gas, and the efficiency of the liquefied gas loading operation can be maximized. Explanation of the symbols

[0096] 10: Cargo Hold 1 20: Cargo Hold 2 30: Cargo Hold 3 40: Cargo Hold 4 100: Heat exchanger 200: Compressor L10: Main loading line L11: 1st loading line L12: 2nd loading line L13: 3rd loading line L14: 4th Loading Line L20: Main Vaporline L21: 1st Vaporline L22: 2nd Vaporline L23: 3rd Vaporline L24: The 4th Vaporline L31: Evaporative Gas Supply Line L32: Evaporative Gas Discharge Line L41: Inert gas supply line L42: Inert gas exhaust line CV: Control valve TS: Temperature sensor

Claims

Claim 1 A liquefied gas loading system for a liquefied gas carrier comprising: a plurality of cargo tanks; a loading line for supplying liquefied gas from a terminal to the cargo tanks; a vapor line for discharging evaporated gas generated in the cargo tanks; a heat exchanger for receiving and heat-exchanging evaporated gas generated in one of the plurality of cargo tanks and inert gas discharged from another of the plurality of cargo tanks; an evaporated gas supply line connected between the vapor line and the heat exchanger to deliver the evaporated gas to the heat exchanger; an evaporated gas discharge line connected between the heat exchanger and the vapor line to discharge the evaporated gas heat-exchanged in the heat exchanger from the heat exchanger; an inert gas supply line connected between the loading line and the heat exchanger to deliver the inert gas to the heat exchanger; and an inert gas discharge line connected between the heat exchanger and the loading line to discharge the inert gas heat-exchanged in the heat exchanger from the heat exchanger. Claim 2 A liquefied gas loading system for a liquefied gas carrier according to claim 1, wherein the evaporated gas generated during the process of loading liquefied gas into any one of the cargo tanks is supplied to the heat exchanger through the vapor line and the evaporated gas supply line, and the evaporated gas supplied to the heat exchanger is supplied to any one of the other cargo tanks through the evaporated gas discharge line and the vapor line after its temperature is raised by heat exchange with the inert gas, and is used for gas-up operations. Claim 3 A liquefied gas loading system for a liquefied gas carrier according to paragraph 2, wherein the inert gas present in any other cargo tank is discharged through the loading line by the evaporated gas supplied from the heat exchanger and then supplied to the heat exchanger through the inert gas supply line, and the inert gas supplied to the heat exchanger has its temperature lowered by heat exchange with the evaporated gas and then is supplied to another cargo tank among the plurality of cargo tanks through the inert gas discharge line and the loading line to be used for pre-cooling operations. Claim 4 A liquefied gas loading system for a liquefied gas carrier according to paragraph 3, wherein the loading line comprises a main loading line connected from the terminal into the interior of the liquefied gas carrier and a plurality of branch loading lines branched from the main loading line and connected to each of the plurality of cargo tanks, and the vapor line comprises a plurality of branch vapor lines provided for each of the plurality of cargo tanks and a main vapor line into which the plurality of branch vapor lines are integrated. Claim 5 A liquefied gas loading system for a liquefied gas carrier, wherein, in paragraph 3, a compressor for accelerating fluid flow is installed on the inert gas supply line. Claim 6 A liquefied gas loading system for a liquefied gas carrier, wherein, in paragraph 3, the liquefied gas is liquefied hydrogen and nitrogen gas is used as the inert gas. Claim 7 A liquefied gas loading system of a liquefied gas carrier according to claim 6, further comprising: a control valve installed on the evaporated gas supply line upstream of the heat exchanger to control the amount of evaporated gas supplied to the heat exchanger; and a temperature sensor installed on the inert gas discharge line downstream of the heat exchanger, wherein the control valve is controlled based on the temperature measured by the temperature sensor. Claim 8 A method for loading liquefied gas in a liquefied gas carrier having a plurality of cargo tanks, comprising: an inerting step of injecting inert gas into the interior of the plurality of cargo tanks; a loading step of supplying liquefied gas from a terminal to one of the plurality of cargo tanks; and a gasing up step of supplying evaporated gas generated during the process of loading liquefied gas into one of the cargo tanks to another of the plurality of cargo tanks to replace the inert gas present in the interior of the other cargo tank, wherein the evaporated gas generated in one of the cargo tanks is heated by heat exchange with the inert gas discharged from the other cargo tank and then supplied to the other cargo tank. Claim 9 A method for loading liquefied gas of a liquefied gas carrier according to claim 8, further comprising a pre-cooling step of supplying an inert gas discharged from any other cargo tank to any other cargo tank among the plurality of cargo tanks to lower the temperature inside any other cargo tank, wherein the inert gas discharged from any other cargo tank is cooled by heat exchange with evaporated gas generated in any one cargo tank and then supplied to any other cargo tank. Claim 10 A method for loading liquefied gas on a liquefied gas carrier according to claim 9, wherein the loading step, the gas-up step, and the pre-cooling step are performed at least partially simultaneously.

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