Subcooling system

Abstract

A subcooling system according to the present invention is for a vessel for carrying liquefied gas, and includes: a cargo tank for storing liquefied gas; a subcooling tank for storing a boil-off gas (BOG), which is generated in the cargo tank, through a BOG supply line; a subcooling unit for subcooling the liquefied gas in the subcooling tank; and a subcooling circulation line through which the liquefied gas in the subcooling tank is introduced back into the subcooling tank after being subcooled through the subcooling unit.

Description

Supercooling system

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0132947 filed September 30, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a supercooling system, and more specifically, to a supercooling system capable of preventing clogging.

[0005] Since liquefying gas reduces its volume, it is stored or transported in a liquefied state to increase storage and transportation efficiency. Gas in this liquefied state is called liquefied gas. The term liquefied gas can be used to encompass all gaseous fuels generally stored in a liquid state, such as liquefied natural gas, liquefied ethane, liquefied ethylene, liquefied petroleum gas, liquefied propane, liquefied butane, liquefied hydrogen, liquefied nitrogen, and ammonia.

[0006] Although storage tanks with excellent insulation performance are used to maintain cryogenic temperatures for liquefied gas, it is impossible to completely block the inflow of heat from the outside, causing the liquefied gas inside the tank to vaporize and generate Boil-Off Gas (BOG). When BOG occurs, the pressure inside the storage tank increases, creating a risk of explosion, and economic losses result because the transportable volume decreases proportionally to the amount of gas that vaporizes.

[0007] As a solution to the problems caused by BOG, there is a method of supercooling the liquefied gas. Such a supercooling system utilizes a supercooling cycle that supercools the liquefied gas through the circulation of a refrigerant.

[0008] However, during the heat exchange process of the supercooling cycle, the temperature may drop excessively, and if the liquefied gas stored in the cargo tank is directly supercooled, the heavy hydrocarbons contained in the liquefied gas freeze, causing clogging and blocking of pipes, which leads to the failure of related equipment.

[0009] The present invention aims to solve the problems of the prior art as described above and to provide a supercooling system that prevents clogging from occurring during the supercooling process.

[0010] A supercooling system according to one embodiment of the present invention is a supercooling system for a ship carrying liquefied gas, comprising: a cargo tank for storing liquefied gas; a supercooling tank for storing BOG generated in the cargo tank through a BOG supply line; a subcooling unit for supercooling the liquefied gas in the supercooling tank; and a supercooling circulation line through which the liquefied gas in the supercooling tank is supercooled through the subcooling unit and then flows back into the supercooling tank.

[0011] In one example, the above supercooling circulation line may include a liquefied gas recovery line that branches off from a first line connecting the subcooling tank to the subcooling unit and connects to the cargo tank.

[0012] In one example, it may include a filter unit provided in the supercooling circulation line.

[0013] In one example, the filter unit may be provided in a filter line that bypasses a first line connecting the subcooling tank to the subcooling unit among the supercooling circulation lines.

[0014] In one example, the supercooled tank may contain pure LNG without heavy hydrocarbon components.

[0015] The supercooling system according to the present invention can fundamentally remove heavy hydrocarbons that cause clogging from the supercooling system, thereby preventing clogging.

[0016] In the supercooling system according to the present invention, when supercooling proceeds in the supercooling tank and the pressure decreases due to the re-liquefaction of BOG, the BOG in the cargo tank moves to the supercooling tank due to the pressure difference, thereby reducing the pressure inside the cargo tank.

[0017] The supercooling system according to the present invention does not require a pump for the supercooling cycle to be provided in a plurality of cargo tanks.

[0018] FIG. 1 is a drawing illustrating a supercooling system according to the present invention.

[0019] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments of the present invention, if it is determined that a detailed description of related known components or functions would hinder understanding of the embodiments of the present invention, such detailed description is omitted.

[0020] In addition, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the embodiments of the present invention. These terms are intended merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by these terms. Where it is stated that a component is "connected," "combined," or "joined" to another component, it should be understood that the component may be directly connected or joined to the other component, but that another component may also be "connected," "combined," or "joined" between each component.

[0021] In this specification, the front-back, left-right, and up-down directions are referred to for convenience of explanation and may be directions orthogonal to one another. However, these directions are determined relatively, and the term "up-down direction" does not necessarily mean a vertical direction.

[0022]

[0023] FIG. 1 is a drawing illustrating a supercooling system (100) of a ship carrying liquefied gas according to the present invention. The supercooling system (100) of a ship (1) carrying liquefied gas includes: a cargo tank (20) for storing liquefied gas; a supercooling tank (30) for storing BOG generated in the cargo tank (20) through a BOG supply line (BL); a subcooling unit (40) for supercooling the liquefied gas in the supercooling tank (30); and a supercooling circulation line (SL) through which the liquefied gas in the supercooling tank (30) is supercooled through the subcooling unit (40) and then flows back into the supercooling tank (30).

[0024] In Figure 1, the dotted line is indicated as a BOG line representing the BOG flow, and the solid line is indicated as a liquefied gas line representing the liquefied gas flow.

[0025] The cargo tank (20) can store liquefied gas to be transported to the ship (1). Although the cargo tank (20) is depicted as having four units in FIG. 1, there is no limit to the number of cargo tanks (20). A cargo tank pump (22) for unloading liquefied gas may be provided within the cargo tank (20), but it is not a pump for the supercooling cycle. Each of the multiple cargo tanks (20) may be connected to a BOG supply line (BL). Additionally, as shown in FIG. 1, a fuel tank (10) of the ship (1) may be provided separately in addition to the cargo tank (20).

[0026] BOG generated in the cargo tank (20) can be supplied to and stored in the supercooling tank (30) through the BOG supply line (BL). BOG generated in the cargo tank (20) can be stored in the supercooling tank (30) and re-liquefied. The BOG supply line (BL) is defined as a line connecting the cargo tank (20) and the supercooling tank (30).

[0027] The subcooling tank (30) can store BOG generated in the cargo tank (20) through the BOG supply line (BL). The subcooling tank (30) is provided separately from the cargo tank (20), and the liquefied gas inside the subcooling tank (30) is subcooled by the subcooling unit (40).

[0028] Pure liquefied gas may be stored in the supercooling tank (30). In the present invention, pure liquefied gas refers to liquefied gas in a state free of heavy hydrocarbons that freeze during the supercooling process and cause problems with clogging. In the present invention, if the liquefied gas is LNG, the supercooling tank (30) may contain pure LNG without heavy hydrocarbon components.

[0029] Pure liquefied gas may be injected into the supercooling tank (30) in advance. In this case, pure liquefied gas filtered by a separate filter (not shown) may be supplied in advance to the supercooling tank (30). However, the present invention is not limited to cases where pure liquefied gas is supplied in advance. For example, only pure liquefied gas may remain during the supercooling cycle process by means of a filter unit (50) provided in the supercooling circulation line (SL).

[0030] The subcooling unit (40) can subcool the liquefied gas in the subcooling tank (30). In the present invention, the liquefied gas in the cargo tank (20) is not subcooled, but rather the liquefied gas in the subcooling tank (30), which is provided separately from the cargo tank (20), is subcooled. Therefore, there is an advantage that a pump for the subcooling cycle does not need to be provided in the multiple cargo tanks (20). In the present invention, the specific configuration of the subcooling unit (40) is not described separately, and the present invention is not limited by the configuration of the subcooling unit (40).

[0031] The subcooling circulation line (SL) is defined as a line through which liquefied gas in the subcooling tank (30) is subcooled through the subcooling unit (40) and then flows back into the subcooling tank (30). The subcooling circulation line (SL) may include a first line (SL1) connecting the subcooling tank (30) to the subcooling unit (40) and a second line (SL2) connecting the subcooling unit (40) to the subcooling tank (30).

[0032] The liquefied gas inside the subcooling tank (30) is pumped by a pump (32) for the subcooling tank and flows into the subcooling unit (40) along the first line (SL1) to be subcooled, and then flows into the subcooling tank (30) along the first line (SL1) to subcool the liquefied gas inside the subcooling tank (30). The subcooling tank (30) is equipped with a spray nozzle (34), and the subcooled liquefied gas is sprayed by the spray nozzle (34) to condense and re-liquefy the BOG present inside the subcooling tank (30). That is, the BOG inside the subcooling tank (30) can be re-liquefied through the process of subcooling the liquefied gas inside the subcooling tank (30).

[0033] According to the present invention, when subcooling proceeds in the subcooling tank (30) and the pressure is lowered due to the re-liquefaction of BOG, the BOG in the cargo tank (20) moves to the subcooling tank (30) due to the pressure difference, thereby naturally lowering the pressure of the cargo tank (20).

[0034] In addition, due to the supercooling according to the present invention, the BOG is re-liquefied in the supercooling tank (30), and since there are no heavy hydrocarbons in the BOG, clogging does not occur even if the liquefied gas of the re-liquefied BOG is supercooled. That is, the BOG is re-liquefied, and the re-liquefied BOG is supercooled to re-liquefy the BOG again, so that heavy hydrocarbons, which are the cause of clogging, do not exist in the supercooling tank (30). Therefore, according to the present invention, heavy hydrocarbons, which are the cause of clogging, are fundamentally removed from the supercooling system, thereby preventing clogging.

[0035]

[0036] A supercooling system (100) according to one embodiment of the present invention may include a liquefied gas recovery line (RL) that branches off from a first line (SL1) connecting a subcooling tank (30) to a subcooling unit (40) among the supercooling circulation lines (SL) and connects to a cargo tank (20). That is, BOG transferred to the supercooling tank (30) is re-liquefied and stored in the supercooling tank (30), and when the amount exceeds a certain amount, it can be recovered to the cargo tank (20) along the liquefied gas recovery line (RL). Although the liquefied gas recovery line (RL) is shown as being connected to the first cargo tank (20) in FIG. 1, the liquefied gas recovery line (RL) may be provided so as to be connected to each of the multiple cargo tanks (20).

[0037]

[0038] A supercooling system (100) according to one embodiment of the present invention may include a filter unit (50) provided in a supercooling circulation line (SL). Even if pure liquefied gas has been stored in a supercooling tank (30) in advance, impurities may be included due to external factors or the subcooling unit (40), so a filter unit (50) may be provided in the supercooling circulation line (SL) to prepare for such cases.

[0039] More specifically, the filter unit (50) may be provided in a filter line (FL) that bypasses the first line (SL1) connecting the subcooling tank (30) to the subcooling unit (40) in the subcooling circulation line (SL). Since the liquefied gas does not need to pass through the filter unit (50) every time, it can be controlled to pass through the filter line (FL) as needed.

[0040]

[0041] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

Claims

1. In a supercooling system of a vessel carrying liquefied gas, Cargo tank for storing liquefied gas; A supercooling tank that stores the BOG generated in the above cargo tank through a BOG supply line; A subcooling unit for subcooling the liquefied gas in the above-mentioned subcooling tank; and A supercooling system comprising a supercooling circulation line in which liquefied gas in the supercooling tank is supercooled through the subcooling unit and then flows back into the supercooling tank.

2. In Claim 1, A supercooling system comprising a liquefied gas recovery line that branches off from a first line connecting the subcooling tank to the subcooling unit among the supercooling circulation lines and connects to the cargo tank.

3. In Claim 1, A supercooling system comprising a filter unit provided in the above supercooling circulation line.

4. In Claim 1, A supercooling system comprising a filter unit provided in a filter line that bypasses a first line connecting the supercooling tank to the subcooling unit among the supercooling circulation lines.

5. In Claim 1, A supercooling system containing pure LNG without heavy hydrocarbon components in the above supercooling tank.

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