Boil-off gas handling system

Abstract

Provided is a boil-off gas handling system comprising: a liquefied gas storage tank; a bunkering line connected from a manifold to the liquefied gas storage tank; a boil-off gas supply line for supplying boil-off gas generated from the liquefied gas storage tank to a fuel consumption site; and a first bypass line that branches from the boil-off gas supply line and is connected to the bunkering line, wherein the bunkering line is purged with the off-gas supplied via the first bypass line. During a bunkering process, the boil-off gas generated from the liquefied gas storage tank can be supplied to the bunkering line and utilized for purging the bunkering line to prevent the problem of possible freezing of an inert gas that can occur when the inert gas comes into contact with liquefied hydrogen.

Description

Evaporative Gas Treatment System

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0150219 filed on October 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] An embodiment of the present invention relates to an evaporative gas treatment system, and more specifically, to an evaporative gas treatment system used to purge a bunkering line of evaporative gas generated in a liquefied gas storage tank.

[0005] Liquefied gases such as hydrogen, ammonia, LNG (Liquefied Natural Gas), and LPG (Liquefied Petroleum Gas) are transported in a liquefied state after being forcibly liquefied by increasing the pressure or lowering the temperature, and stored in liquefied gas storage tanks.

[0006] Although liquefied gas is stored in a liquid state in insulated storage tanks, external heat is continuously transferred to the tank, causing the gas to naturally vaporize within the tank and generate Boil-Off Gas (BOG). Furthermore, while the liquefied gas storage tank is empty, the internal temperature remains higher than the temperature of the injected liquefied gas due to natural heat penetration from the outside. Consequently, when bunkering operations are performed to inject liquefied gas into the storage tank, the supplied gas vaporizes, generating a large amount of Boil-Off Gas. Therefore, conventionally, the generated Boil-Off Gas was simply released to the outside or burned, but this resulted in energy waste as the Boil-Off Gas could not be utilized.

[0007] In addition, when bunkering operations are carried out to inject liquefied gas into a liquefied gas storage tank, some liquefied gas remains in the bunkering line. Conventionally, when the liquefied gas is LNG, the remaining liquefied gas in the bunkering line is purged using nitrogen, an inert gas. However, when the liquefied gas is hydrogen, since the boiling point of nitrogen gas is -196°C, which is higher than the boiling point of liquefied hydrogen -253°C, problems such as the bunkering line becoming blocked or valves becoming stuck occur when nitrogen is used to purge the bunkering line.

[0008] Therefore, there is a need to solve the problem of nitrogen freezing in the bunkering line and to efficiently treat the evaporated gas generated in the liquefied gas storage tank.

[0009] The present invention supplies evaporated gas generated from a liquefied gas storage tank during the bunkering process to a bunkering line to purge the bunkering line, thereby preventing in advance the problem of freezing of the inert gas that may occur when the inert gas and the liquefied gas meet, and enabling efficient use of the evaporated gas.

[0010] The present invention may provide an evaporative gas treatment system comprising: a liquefied gas storage tank; a bunkering line connected to the liquefied gas storage tank from a manifold; an evaporative gas supply line that supplies evaporative gas generated from the liquefied gas storage tank to a fuel demand source; and a first bypass line that branches off from the evaporative gas supply line and is connected to the bunkering line, and purging the bunkering line with evaporative gas supplied through the first bypass line.

[0011] In one example, an evaporative gas treatment system may be provided, comprising: a preheater provided on the evaporative gas supply line for heating evaporative gas supplied from the liquefied gas storage tank; and a compressor provided downstream of the preheater on the evaporative gas supply line for compressing the evaporative gas heated in the preheater.

[0012] In one example, an evaporative gas treatment system including a first valve provided on the first bypass line may be provided.

[0013] In one example, an evaporative gas treatment system may be provided, comprising a second bypass line that branches off from the evaporative gas supply line upstream of the preheater and joins the evaporative gas supply line downstream of the compressor.

[0014] In one example, an evaporative gas treatment system including a second valve provided in the second bypass line may be provided.

[0015] In one example, an evaporative gas treatment system for storing liquid hydrogen in the above-mentioned liquid gas storage tank may be provided.

[0016] The evaporative gas treatment system according to an embodiment of the present invention can be used to purge the bunkering line by supplying evaporative gas generated from a liquefied gas storage tank to the bunkering line.

[0017] In particular, in the case of a liquefied hydrogen carrier, if the bunkering line is purged using hydrogen gas, which is a boil-off gas, the problem of freezing of the inert gas that may occur when the existing inert gas meets the liquefied hydrogen can be prevented in advance.

[0018] The effects of the present invention are not limited to those described above, and other unmentioned effects may be clearly understood from the mechanism below.

[0019] FIG. 1 illustrates an evaporative gas treatment system according to an embodiment of the present invention.

[0020] FIG. 2 illustrates a bunkering line purging process using evaporated gas according to an embodiment of the present invention.

[0021] FIG. 3 illustrates the process of supplying evaporated gas to a low-pressure fuel demand source according to an embodiment of the present invention.

[0022] FIG. 4 illustrates the process of supplying evaporated gas to a high-pressure fuel demand source according to an embodiment of the present invention.

[0023] 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.

[0024] 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.

[0025]

[0026] Below, an evaporative gas treatment system (10) according to an embodiment of the present invention will be described.

[0027] FIG. 1 illustrates an evaporative gas treatment system (10) according to an embodiment of the present invention.

[0028] Referring to FIG. 1, an evaporative gas treatment system (10) according to an embodiment of the present invention may be provided, comprising: a liquefied gas storage tank (100); a bunkering line (L10) connected from a manifold (110) to the liquefied gas storage tank (100); an evaporative gas supply line (L20) that supplies evaporative gas generated from the liquefied gas storage tank (100) to a fuel demand place (300); and a first bypass line (L31) that branches off from the evaporative gas supply line (L20) and is connected to the bunkering line (L10); and a evaporative gas treatment system (10) that purges the bunkering line (L10) with evaporative gas supplied through the first bypass line (L31).

[0029] The liquefied gas storage tank (100) can store liquefied gas in a liquid state. The liquefied gas storage tank (100) may be provided as a C-Type tank of the pressure vessel type having a cylindrical structure with a circular cross-section. Although the embodiment of the present invention is intended for hydrogen liquefied gas, it is not limited thereto, and the liquefied gas storage tank (100) can contain liquefied gas in a cryogenic state, such as ammonia, liquefied natural gas (LNG), liquefied petroleum gas (LPG), etc.

[0030] The liquefied gas storage tank (100) can receive liquefied gas through the bunkering line (L10). Since the liquefied gas storage tank (100) is empty until liquefied gas is supplied, natural heat penetration from the outside may occur while the liquefied gas storage tank (100) is empty. Accordingly, when bunkering is performed from the manifold (110) to the liquefied gas storage tank (100), the internal temperature of the liquefied gas storage tank (100) is higher than the temperature of the liquefied gas (for example, if the liquefied gas is liquid hydrogen, the boiling point is -253°C), so the liquefied gas may vaporize as it is supplied to the liquefied gas storage tank (100), and a large amount of evaporated gas may be generated.

[0031] The liquefied gas supply process can be carried out through a drying process in which dry air is introduced into the liquefied gas storage tank (100) to remove internal moisture of the liquefied gas storage tank (100), an inerting process in which inert gas is injected to create a non-explosive environment in the liquefied gas storage tank (100), a gasssing up process in which heated liquefied gas is supplied into the liquefied gas storage tank (100) to replace the inert gas, a cool down process in which the internal temperature of the liquefied gas storage tank (100) is lowered to a certain level or lower, and a loading process in which liquefied gas is filled into the liquefied gas storage tank (100).

[0032] The bunkering line (L10) can be defined as a line connecting the manifold (110) and the liquefied gas storage tank (100). The bunkering line (L10) can supply liquefied gas to the liquefied gas storage tank (100) while carrying out the bunkering process from an external supplier, such as a bunkering vessel or a liquefied gas terminal.

[0033] The evaporative gas supply line (L20) is defined as a line connecting the liquefied gas storage tank (100) and the fuel demand source (300), and a preheater (210) and a compressor (220) may be provided on the evaporative gas supply line (L20).

[0034] The preheater (210) can heat the ultra-low temperature evaporated gas supplied from the liquefied gas storage tank (100) to a temperature at which it can be compressed by the compressor (220). In the case of a direct heating method, the preheater (210) can heat the evaporated gas through a separate steam supply line (not shown), and in the case of an indirect heating method, it can heat the evaporated gas by receiving an intermediate heat medium through an intermediate heat medium heat exchanger (not shown) and an intermediate heat medium circulation line (not shown) and exchanging heat with the evaporated gas. For example, when hydrogen liquefied gas is supplied to the liquefied gas storage tank (100), for example, hydrogen evaporated gas at about -250°C can be heated by the preheater (210) to a temperature at which it can be compressed by the compressor (220), for example, about -130°C.

[0035] A compressor (220) is provided downstream of a preheater (210) on an evaporative gas supply line (L20) and can compress the evaporative gas heated by the preheater (210). The compressor (220) can compress the evaporative gas to, for example, about 7 barg. Additionally, an additional compressor may be required to meet the pressure required by the fuel demand location (300).

[0036] The first bypass line (L31) can be branched from the evaporative gas supply line (L20) and connected to the bunkering line (L10). Specifically, the first bypass line (L31) can be branched from the evaporative gas supply line (L20) downstream of the compressor (220) and connected to the bunkering line (L10). Additionally, the first bypass line (L31) can be branched from the evaporative gas supply line (L20) between the compressor (220) and the fuel demand point (300) and connected to the bunkering line (L10). Thus, the evaporative gas compressed by the compressor (220) can be supplied to the bunkering line (L10) through the first bypass line (L31). The evaporative gas supplied through the first bypass line can be used to purge the bunkering line (L10).

[0037] The second bypass line (L32) can branch off from the evaporative gas supply line (L20) upstream of the preheater (210) and join the evaporative gas supply line (L20) downstream of the compressor (220). Evaporative gas generated from the liquefied gas storage tank (100) can be supplied to a fuel demand location (300) through the second bypass line (L32) without passing through the preheater (210) and the compressor (220). Evaporative gas passing through the second bypass line (L32) can be supplied to a fuel demand location (300) where low pressure is required.

[0038] The first valve (610) may be provided on the first bypass line (L31). The first valve (610) can control whether and how much evaporated gas compressed by the compressor (220) is supplied to the bunkering line (L10).

[0039] The second valve (620) may be provided on the second bypass line (L32). The second valve (620) can control whether and how much evaporated gas generated from the liquefied gas storage tank (100) is supplied to the fuel demand point (300) without passing through the preheater (210) and compressor (220).

[0040] A third valve (630) may be provided on the vaporized gas supply line (L60). The third valve (630) can control whether to supply the evaporated gas generated in the liquefied gas storage tank (100) to the liquefied gas supply line (L50) and the amount of supply.

[0041] A fourth valve (640) may be provided on the vent line (L40). The fourth valve (640) can control whether and how much gas generated from the vessel, such as evaporated gas generated from the liquefied gas storage tank (100), is supplied to the vent line (L40). The vent line (L40) can connect the evaporated gas supply line (L20) and the vent master (400). Specifically, the vent line (L40) may be branched from the evaporated gas supply line (L20) between the liquefied gas storage tank (100) and the preheater (210) and connected to the vent master (400). A portion of the evaporated gas generated from the liquefied gas storage tank (100) may flow into the vent line (L40) and be supplied to the vent master (400). The vent master (400) can discharge gases generated from other vessels, such as evaporated gas supplied to the vent line (L40), to the outside.

[0042] The liquefied gas supply line (L50) can be defined as a line connected from the liquefied gas storage tank (100) through the vaporizer (500) to the evaporated gas supply line (L20). Specifically, the liquefied gas supply line (L50) can be connected to the evaporated gas supply line (L20) upstream of the preheater (210).

[0043] A vaporizer (500) is provided in a liquefied gas supply line (L50) to vaporize liquefied gas and then supply the vaporized liquefied gas to an evaporated gas supply line (L20). In the case of a direct vaporization method, the vaporizer (500) can vaporize liquefied gas through a separate seawater supply line (not shown), and in the case of an indirect vaporization method, it can vaporize liquefied gas by receiving an intermediate heat medium through an intermediate heat medium heat exchanger (not shown) and an intermediate heat medium circulation line (not shown) and exchanging heat with the liquefied gas.

[0044] Referring to FIG. 2, the purging process of a bunkering line (L10) using evaporated gas according to the present invention is explained. In FIG. 2, the process of purging the bunkering line (L10) using evaporated gas generated from a liquefied gas storage tank (100) and returning to the liquefied gas storage tank (100) is indicated by a thick solid line.

[0045] During bunkering operations, the evaporated gas generated from the liquefied gas storage tank (100) can be supplied to the preheater (210) through the evaporated gas supply line (L20). The preheater (210) can heat the evaporated gas supplied from the liquefied gas storage tank (100) through the evaporated gas supply line (L20) to the supply conditions of the compressor (220). The compressor (220) can compress the evaporated gas heated by the preheater (210). The first valve (610) can be opened to allow the compressed hydrogen evaporated gas to be supplied to the first bypass line (L31). The second valve (620) can be closed to block the supply of the compressed hydrogen evaporated gas to the second bypass line (L32). The compressed hydrogen boil-off gas supplied through the first bypass line (L31) can purge the remaining liquefied cargo remaining in the bunkering line (L10) after the bunkering operation.

[0046] When liquid hydrogen is stored in a liquefied gas storage tank (100), the hydrogen vapor generated within the liquefied gas storage tank (100) can be supplied to a preheater (210) through a vapor supply line (L20). The preheater (210) can receive hydrogen vapor at, for example, about -250°C through the vapor supply line (L20) and heat the hydrogen vapor to, for example, about -130°C. The compressor (220) can compress the hydrogen vapor heated to, for example, about -130°C through the preheater (210) to, for example, about 7 barg. The compressed hydrogen vapor is supplied to a bunkering line (L10) through a first bypass line (L31) to purge liquid hydrogen or hydrogen gas present in the bunkering line (L10). When purging the bunkering line (L10) using conventional inert gas, since the boiling point of nitrogen (-196°C) is higher than the boiling point of hydrogen (-253°C), the problem of nitrogen freezing due to contact between nitrogen and liquid hydrogen may occur. However, when purging the bunkering line (L10) with gaseous hydrogen, which is a evaporated gas, nitrogen is not used, so the problem of freezing caused by contact between nitrogen and liquid hydrogen can be prevented in advance. In addition, by using the hydrogen evaporated gas generated during the bunkering operation to purge the bunkering line (L10), hydrogen can be used more efficiently.

[0047] Referring to FIG. 3, the process of supplying to a low-pressure fuel demand location (300) using evaporated gas according to the present invention is described. FIG. 3 shows the process of supplying evaporated gas to a low-pressure fuel demand location (300) using evaporated gas generated from a liquefied gas storage tank (100) as indicated by a thick solid line.

[0048] During bunkering operations, hydrogen vapor generated from the liquefied gas storage tank (100) can be supplied through the vaporized gas supply line (L20) to the second bypass line (L32) branched from the vaporized gas supply line (L20). Additionally, the first valve (610) can be closed to block the supply of vaporized gas to the first bypass line (L31). Additionally, the fourth valve (640) can be closed to block the supply of vaporized gas to the vent line (L40). The hydrogen vapor supplied through the second bypass line (L32) can be supplied to a fuel demand location (300) that requires low-pressure hydrogen.

[0049] Referring to FIG. 4, the process of supplying to a high-pressure fuel demand location (300) using evaporated gas according to the present invention is described. FIG. 4 shows the process of supplying evaporated gas to a high-pressure fuel demand location (300) using evaporated gas generated from a liquefied gas storage tank (100) as indicated by a thick solid line.

[0050] During bunkering operations, hydrogen vapor generated from the liquefied gas storage tank (100) can be supplied to the preheater (210) through the vaporized gas supply line (L20). Additionally, the third valve (630) can be closed to block the supply of vaporized gas to the liquefied gas supply line (L50). Additionally, the fourth valve (640) can be closed to block the supply of vaporized gas to the vent line (L40). The preheater (210) can receive the hydrogen vaporized gas through the vaporized gas supply line (L20) and heat the hydrogen vaporized gas. The compressor (220) can compress the hydrogen vaporized gas heated through the preheater (210) into high-pressure hydrogen, and the compressed hydrogen can be supplied to a fuel demand location (300) that requires high-pressure hydrogen.

[0051] The present invention is not limited to the embodiments described above, and may include a combination of the above embodiments or a combination of at least one of the above embodiments and known technology as another embodiment.

[0052] Although the present invention has been described in detail through specific embodiments, this is for the purpose of specifically explaining the invention, and the invention is not limited thereto. It will be obvious that modifications or variations are possible within the technical scope of the invention by those skilled in the art.

[0053] All simple variations or modifications of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims.

Claims

1. Liquefied gas storage tank; A bunkering line connecting the manifold to the above-mentioned liquefied gas storage tank; An evaporative gas supply line that supplies evaporative gas generated from the above-mentioned liquefied gas storage tank to a fuel demand source; and A first bypass line branching off from the above evaporative gas supply line and connected to the above bunkering line; comprising A vapor treatment system that purges the bunkering line with vapor supplied through the first bypass line.

2. In Claim 1, A preheater provided on the above-mentioned evaporative gas supply line for heating the evaporative gas supplied from the above-mentioned liquefied gas storage tank; and An evaporative gas treatment system comprising a compressor provided at the downstream end of the preheater on the above evaporative gas supply line, for compressing the evaporative gas heated in the preheater.

3. In Claim 1, An evaporative gas treatment system comprising a first valve provided on the first bypass line.

4. In Claim 2, An evaporative gas treatment system comprising a second bypass line that branches off from the evaporative gas supply line upstream of the preheater and joins the evaporative gas supply line downstream of the compressor.

5. In Claim 4, An evaporative gas treatment system including a second valve provided in the second bypass line.

6. In Claim 1, A boil-off gas treatment system for storing liquid hydrogen in the above-mentioned liquid gas storage tank.

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