Gas treatment system and ship having the same

Abstract

The present invention relates to a gas treatment system and a ship including the same, wherein the system for treating liquefied gas, which is a heavy hydrocarbon or ammonia, comprises: a fuel tank for storing the liquefied gas as fuel to be supplied to a propulsion engine of the ship; a liquefied gas supply line for supplying the liquefied gas from the fuel tank in liquid form to the propulsion engine and having a high-pressure pump provided therein; a reliquefaction device for liquefying evaporated gas generated in a cargo tank for storing the liquefied gas and transferring it to the fuel tank; and a liquefied gas recovery line for recovering the liquid liquefied gas discharged from the propulsion engine upstream of the high-pressure pump, wherein the reliquefaction device comprises: a compressor for compressing the evaporated gas discharged from the cargo tank; a condenser for cooling and liquefying the compressed evaporated gas with a refrigerant; a buffer for temporarily storing the evaporated gas liquefied in the condenser; and an evaporated gas supply line for transferring the evaporated gas upstream of the buffer to the liquefied gas supply line between the fuel tank and the high-pressure pump.

Description

Technology Field

[0001] The present invention relates to a gas processing system and a vessel including the same. Background Technology

[0002] Generally, liquefied petroleum gas (LPG) is produced by pressurizing a gas at room temperature, with low-boiling point hydrocarbons such as propane and butane among the petroleum components as the main components. This liquefied petroleum gas is filled into small, lightweight pressure vessels (bombs) and widely used as fuel for household, commercial, industrial, and automotive use.

[0003] Liquefied petroleum gas is extracted in a gaseous state at the production site, liquefied and stored through liquefied petroleum gas processing facilities, and then transported overland by liquefied petroleum gas carriers while maintaining its liquid state, after which it is supplied to demand centers in various forms, such as gas.

[0004] Since the boiling point of liquefied petroleum gas is approximately -50°C, liquefied petroleum gas carriers must maintain a temperature lower than this. Therefore, storage tanks for liquefied petroleum gas utilize low-temperature steel (low-temperature carbon steel and nickel steel) that is resistant to low temperatures, and liquefied petroleum gas carriers are also equipped with reliquefaction facilities.

[0005] Conventionally, these liquefied petroleum gas carriers generated propulsion by operating engines using diesel fuel. However, the combustion of diesel fuel in ship propulsion engines produces harmful substances such as nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO2), and there is a problem of environmental pollution as these harmful substances are released into the atmosphere.

[0006] Therefore, in recent years, continuous development has been underway for engines operating on liquefied petroleum gas and for systems supplying liquefied petroleum gas to these engines, in order to significantly reduce exhaust pollution compared to the use of diesel fuel. The problem to be solved

[0007] The present invention was created to solve the problems of the prior art as described above, and the objective of the present invention is to provide a gas processing system capable of generating propulsion using liquefied petroleum gas or ammonia, and a ship including the same. means of solving the problem

[0008] A gas treatment system according to one aspect of the present invention is a system for treating liquefied gas, which is a heavy hydrocarbon or ammonia, comprising: a fuel tank for storing the liquefied gas as fuel to be supplied to a propulsion engine of a ship; a liquefied gas supply line for supplying the liquefied gas from the fuel tank in liquid form to the propulsion engine and having a high-pressure pump provided therein; a re-liquefaction device for liquefying evaporated gas generated in a cargo tank for storing the liquefied gas and transferring it to the fuel tank; and a liquefied gas recovery line for recovering the liquid liquefied gas discharged from the propulsion engine upstream of the high-pressure pump, wherein the re-liquefaction device comprises: a compressor for compressing the evaporated gas discharged from the cargo tank; a condenser for cooling and liquefying the compressed evaporated gas with a refrigerant; a buffer for temporarily storing the evaporated gas liquefied in the condenser; and an evaporated gas supply line for transferring the evaporated gas upstream of the buffer to the liquefied gas supply line between the fuel tank and the high-pressure pump.

[0009] Specifically, the liquefied gas recovery line is provided with a pressure reducing valve that reduces the pressure of the excess liquid liquefied gas mixed with lubricating oil discharged from the propulsion engine, and the excess liquid liquefied gas mixed with lubricating oil used in the propulsion engine as it passes through the interior of the propulsion engine can be transferred to the liquefied gas supply line upstream of the high-pressure pump so that it can be recirculated into the propulsion engine.

[0010] Specifically, the liquefied gas recovery line may be provided with a cooler that cools the liquefied gas depressurized by the pressure reducing valve and allows it to flow into the high-pressure pump in liquid form.

[0011] Specifically, the evaporative gas supply line can be configured to control the discharge pressure of the compressor by connecting the upstream of the high-pressure pump and the upstream of the buffer in response to internal pressure fluctuations of the buffer according to the temperature of the refrigerant.

[0012] Specifically, the buffer may be a gas-liquid separator that separates the evaporated gas liquefied in the condenser.

[0013] Specifically, the re-liquefaction device may include an intercooler that exchanges heat between a portion of the liquefied evaporated gas from the condenser and the remainder, and transfers the evaporated gas generated by the heat exchange to the compressor.

[0014] Specifically, the reliquefaction device may operate in at least one of a reliquefaction mode that transfers the liquid separated from the gas-liquid separator to the cargo tank via the intercooler, and a fuel supply mode that transfers the liquid separated from the gas-liquid separator to the fuel tank to be supplied to the propulsion engine.

[0015] A vessel according to one aspect of the present invention is a liquefied gas carrier having the gas processing system. Effects of the invention

[0016] The gas treatment system according to the present invention and the vessel including the same can reduce environmental pollution and increase energy efficiency by moving away from conventional systems that use only diesel fuel and enabling the use of liquefied petroleum gas or ammonia as a propulsion fuel. Brief explanation of the drawing

[0017] FIG. 1 is a conceptual diagram of a gas treatment system according to a first embodiment of the present invention. FIG. 2 is a conceptual diagram of a gas treatment system according to a second embodiment of the present invention. FIG. 3 is a conceptual diagram of a gas treatment system according to a third embodiment of the present invention. FIG. 4 is a conceptual diagram of a gas treatment system according to the fourth embodiment of the present invention. FIG. 5 is a conceptual diagram of a gas treatment system according to the fifth embodiment of the present invention. FIG. 6 is a conceptual diagram of a gas treatment system according to the sixth embodiment of the present invention. FIG. 7 is a conceptual diagram of a gas treatment system according to the seventh embodiment of the present invention. Specific details for implementing the invention

[0018] The objects, specific advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings. It should be noted that in assigning reference numerals to the components of each drawing in this specification, identical components are assigned the same number whenever possible, even if they are shown in different drawings. Furthermore, in describing the present invention, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the invention.

[0019] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. For reference, in this specification, the liquefied gas may be a heavy hydrocarbon such as LPG (propane, butane, etc.) or ammonia, but is not limited thereto and may encompass all substances having a boiling point lower than room temperature and a calorific value.

[0020] Additionally, it should be noted that in this specification, liquefied gas / evaporated gas is not necessarily limited to a liquid or gaseous state due to its name.

[0021] The present invention includes a vessel equipped with a gas processing system as described below. The vessel is a concept that includes gas carriers, merchant vessels carrying cargo or people other than gas, FSRUs, FPSOs, bunkering vessels, offshore plants, etc., but it should be noted that it may be a liquefied gas carrier as an example.

[0022] Although not illustrated in the drawings of the present invention, pressure sensors (PT), temperature sensors (TT), etc., may be provided at appropriate locations without limitation, and the measured values ​​from each sensor may be used in various ways without limitation in the operation of the configurations described below.

[0024] FIG. 1 is a conceptual diagram of a gas treatment system according to a first embodiment of the present invention.

[0025] Referring to FIG. 1, a gas treatment system (1) according to a first embodiment of the present invention includes a gas storage unit, a fuel supply unit (20), a re-liquefaction unit (30), and a fuel recovery unit (40).

[0027] The gas storage unit includes a cargo tank (10), a fuel tank (12), etc., as a configuration for storing liquefied gas.

[0028] The cargo tank (10) is a plurality of cargo tanks provided on board a ship that is a liquefied gas carrier. Of course, if the ship is of a type other than a gas carrier, it may be a tank or container that is separately added on board or outside.

[0029] The cargo tank (10) is a tank that stores liquefied gas in a low-temperature liquid state at atmospheric pressure, and various insulation structures may be added to the walls to prevent the liquefied gas from vaporizing. In addition, the cargo tank (10) may be a membrane-type tank or an independent tank, and its shape or specifications are not limited.

[0030] A liquefied gas transfer line (L21) may be provided from the cargo tank (10) to the fuel tank (12) to be described later, and the liquefied gas from the cargo tank (10) is transferred to the fuel tank (12) through the liquefied gas transfer line (L21). The liquefied gas transferred to the fuel tank (12) is used as fuel for the propulsion engine (E).

[0031] For reference, in this specification, the propulsion engine (E) is sufficient if it is a configuration for propelling a ship, and can be interpreted as any configuration capable of generating thrust directly or indirectly by consuming liquefied gas, such as turbines, fuel cells, etc., rather than engines. Additionally, in this specification, the propulsion engine (E) may be used as a term encompassing all gas consumption sources, such as engines for propulsion, engines for power generation, and gas combustion devices.

[0032] A transfer pump (11) may be assigned to the cargo tank (10), and a liquefied gas transfer line (L21) may be connected to the transfer pump (11). The transfer pump (11) may be provided inside the cargo tank (10) and may be provided as a submerged type submerged in liquefied gas.

[0033] A transfer pump (11) may be provided in some of the multiple cargo tanks (10). The cargo tanks (10) are basically intended for cargo transport, and at least two cargo pumps (unloading pumps, stripping pumps, etc., not shown) for unloading cargo are provided in each cargo tank (10). In order to use the liquefied gas stored inside at least one of the cargo tanks (10) as fuel for a propulsion engine (E) (ME-LGI), etc., a transfer pump (11) may be added in addition to the cargo pumps.

[0034] For example, when four cargo tanks (10) are arranged in parallel along the length of the ship, the liquefied gas stored in the 4th cargo tank (10) located near the engine room where the propulsion engine (E) is housed can be transferred to the fuel tank (12) and used as fuel for the propulsion engine (E), and for this purpose, a transfer pump (11) can be provided only in the 4th cargo tank (10).

[0035] Since the liquefied gas stored in the cargo tank (10) naturally evaporates due to external heat penetration, evaporated gas is generated in the cargo tank (10). An evaporated gas discharge line (L10) for discharging evaporated gas may be provided in the cargo tank (10). The evaporated gas discharged from the cargo tank (10) can be liquefied and returned or used as fuel for the propulsion engine (E), which will be explained in detail below in the section describing the re-liquefaction unit (30).

[0036] Cargo tanks (10) may be provided in multiple numbers to store at least two types of liquefied gases among liquefied gases (propane, butane, propylene, etc.) that have heavy hydrocarbons as their main component. That is, the cargo tanks (10) may include a first cargo tank (10) that stores a first type of liquefied gas and a second cargo tank (10) that stores a second type of liquefied gas, and for example, the first cargo tank (10) may store propane, and the second cargo tank (10) may store butane, etc.

[0037] The evaporated gas of the cargo tank (10) is liquefied through the condenser (32) of the re-liquefaction unit (30) described later. When configured so that the liquefied evaporated gas is returned to the cargo tank (10), the condenser (32) may be provided for at least as many types of liquefied gas stored in the cargo tank (10) (additionally, a backup may be provided).

[0038] That is, when the cargo tank (10) stores two types of liquefied gas, it is preferable to provide at least three condensers (32). In addition, since a compressor (31) is provided as a set corresponding to the condensers (32), the compressor (31) can also be provided in multiple numbers corresponding to the number of condensers (32).

[0039] However, in this embodiment, the evaporated gas liquefied by the condenser (32) can be transferred to a fuel tank (12) or the like without being returned to the cargo tank (10), so that even if the cargo tank (10) is configured to store two or more types of liquefied gas, the number of installed condensers (32) (or number of operating condensers) can be reduced to less than the number of types of liquefied gas.

[0040] That is, the evaporated gas of the cargo tank (10) is transferred to the condenser (32) through the evaporated gas discharge line (L10) and can be liquefied by refrigerant heat exchange in the condenser (32), and the liquefied evaporated gas is transferred to the high-pressure pump (22) described later through the fuel tank (12) and may not be returned to the cargo tank (10) (fuel supply mode).

[0042] The fuel tank (12) stores liquefied gas as fuel to be supplied to the propulsion engine (E). The fuel tank (12) may be of the same or different type as the cargo tank (10), which is a standalone type (SPB type, MOSS type) or membrane type that stores a large amount of liquefied gas at atmospheric pressure, and may be a standalone type (Type C, pressure vessel type) that stores liquefied gas at high pressure.

[0043] At this time, the fuel tank (12) can store liquefied gas at a critical pressure or higher (e.g., around 18 bar) or at a critical pressure or lower (e.g., around 8 bar), and an insulating structure can be provided on at least one side of the inside or outside of the wall to prevent vaporization of the liquefied gas.

[0044] The fuel tank (12) can be mounted on the upper deck of the vessel and is provided to be supported on the upper deck via a saddle. The fuel tank (12) can be positioned on the upper deck so as not to interfere with components (such as manifolds) for loading / unloading liquefied gas of the cargo tank (10) and so as not to obstruct the visibility during navigation of the vessel. For example, the fuel tank (12) can be provided on the upper deck on the port or starboard side of the bow. In this case, the fuel tank (12) may be referred to as a deck tank.

[0045] The fuel tank (12) may be configured to temporarily store liquefied gas between the cargo tank (10) and the propulsion engine (E), and the fuel tank (12) may also be configured to have the function of condensing the evaporated gas generated in the cargo tank (10) using the liquefied gas stored inside.

[0046] That is, the fuel tank (12) may be used as a recondenser (32) that receives and condenses the evaporated gas generated in the cargo tank (10) using the liquefied gas stored inside. To this end, an evaporated gas branch line (not shown) that branches off toward the fuel tank (12) from upstream of the condenser (32) may be provided in the evaporated gas discharge line (L10) extended from the cargo tank (10).

[0047] The liquefied gas transfer line (L21) described above is connected from the cargo tank (10) to the fuel tank (12), and the liquefied gas can be transferred to the fuel tank (12) by a transfer pump (11) immersed in the cargo tank (10). The liquefied gas stored in the fuel tank (12) can be managed at an appropriate level / pressure considering the operating conditions of the vessel, etc.

[0048] Conversely, it may be possible for liquefied gas to be returned from the fuel tank (12) to the cargo tank (10), but this may be limited to cases where the liquefied gas stored in the fuel tank (12) has the same composition as the liquefied gas stored in the cargo tank (10).

[0049] The liquefied gas stored in the fuel tank (12) can be transferred from the fuel tank (12) to the propulsion engine (E) through the low-pressure pump (21) of the fuel supply unit (20) to be described later. A liquefied gas supply line (L20) can be provided from the fuel tank (12) to the propulsion engine (E). That is, a liquefied gas transfer line (L21) is provided from the cargo tank (10) to the fuel tank (12), and a liquefied gas supply line (L20) is provided from the fuel tank (12) to the propulsion engine (E).

[0050] Of course, the liquefied gas supply line (L20) may be configured to supply liquefied gas from the cargo tank (10) to the propulsion engine (E) by bypassing the fuel tank (12), in which case the liquefied gas supply line (L20) can deliver the liquefied gas from the cargo tank (10) and / or the fuel tank (12) to the propulsion engine (E).

[0052] The fuel supply unit (20) supplies liquefied gas to the propulsion engine (E) to enable the propulsion engine (E) to operate. The fuel supply unit (20) includes a low-pressure pump (21), a high-pressure pump (22), a heat exchanger (23), etc., and a filter (not shown in the symbol) may be provided at an appropriate location.

[0053] The low-pressure pump (21) transfers the liquefied gas from the fuel tank (12) to the propulsion engine (E). The low-pressure pump (21) may be provided inside or outside the fuel tank (12) and may be provided on the liquefied gas supply line (L20) connecting the fuel tank (12) to the propulsion engine (E).

[0054] The low-pressure pump (21) can pressurize the liquefied gas to a pressure lower than the required pressure of the propulsion engine (E). Specifically, the low-pressure pump (21) can pressurize the liquefied gas to match the suction pressure (e.g., 20 bar) of the high-pressure pump (22) located downstream. That is, the low-pressure pump (21) increases the pressure of the liquefied gas by the difference between the internal pressure of the fuel tank (12) and the suction pressure of the high-pressure pump (22).

[0055] However, if the storage pressure of the fuel tank (12) corresponds to the suction pressure of the high-pressure pump (22), the low-pressure pump (21) may be omitted.

[0056] A liquefied gas return line (not shown) may be provided downstream of the low-pressure pump (21) in the liquefied gas supply line (L20). The liquefied gas return line can serve to recover excess liquefied gas to the fuel tank (12) when the flow rate delivered to the propulsion engine (E) through the low-pressure pump (21) exceeds the required flow rate of the propulsion engine (E).

[0057] Alternatively, the liquefied gas return line can be configured to increase the internal pressure of the fuel tank (12) by allowing the liquefied gas, which has been pressurized by the low-pressure pump (21) after being discharged from the fuel tank (12), to flow back into the fuel tank (12). Thus, the fuel tank (12) can maintain a high internal pressure to minimize the generation of evaporated gas within the fuel tank (12).

[0058] The high-pressure pump (22) pressurizes the liquefied gas in the fuel tank (12) to the required pressure of the propulsion engine (E) and delivers it to the propulsion engine (E). The pressure required by the propulsion engine (E) may be 20 to 50 bar, but may vary depending on the specifications of the propulsion engine (E).

[0059] A high-pressure pump (22) is provided on a liquefied gas supply line (L20) extending from a fuel tank (12) to a propulsion engine (E). The type of high-pressure pump (22) is not specifically limited, and multiple high-pressure pumps (22) may be provided in parallel to back up each other, as shown in the drawing.

[0060] The high-pressure pump (22) may be provided upstream of the heat exchanger (23) described later as shown in the drawing, or it may be provided downstream of the heat exchanger (23) as shown in the drawing. In the latter case, the high-pressure pump (22) can pressurize the liquefied gas, whose temperature has been controlled by the heat exchanger (23), to the pressure required by the propulsion engine (E).

[0061] In order to suppress the occurrence of cavitation during the pressurization process of the liquefied gas of the high-pressure pump (22), the liquefied gas may be introduced into the high-pressure pump (22) in a liquid state. If a heat exchanger (23) is provided upstream of the high-pressure pump (22), the heat exchanger (23) can control the temperature of the liquefied gas in consideration of the above.

[0062] The pressure of the liquefied gas sucked into the high-pressure pump (22) can correspond to the pressure of the liquefied gas discharged by the low-pressure pump (21). It can also correspond to the pressure of the liquefied gas recovered from the propulsion engine (E).

[0063] A filter (not shown) for filtering out impurities may be provided downstream of the high-pressure pump (22), and the filter may also be provided upstream of the low-pressure pump (21), as shown in the drawing.

[0064] Additionally, a fuel supply valve (not shown) may be provided downstream of the high-pressure pump (22) in the liquefied gas supply line (L20), and the fuel supply valve and the pressure reducing valve (not shown) provided in the liquefied gas recovery line (L30) may be formed into a single train and referred to as an FVT (fuel valve train).

[0065] A liquefied gas circulation line (L22) connected to a liquefied gas recovery line (L30) of a fuel recovery unit (40) to be described later may be provided in the liquefied gas supply line (L20) downstream of the high-pressure pump (22). The liquefied gas discharged from the high-pressure pump (22) is delivered to the liquefied gas recovery line (L30) along the liquefied gas circulation line (L22) and then circulated back to the high-pressure pump (22).

[0066] A minimum required flow rate is set for the high-pressure pump (22) for operational stability, etc. This is called the minimum flow, and it is desirable that liquefied gas satisfying the minimum required flow rate be introduced into the high-pressure pump (22) during operation.

[0067] However, there are cases where the consumption of the propulsion engine (E), etc., downstream of the high-pressure pump (22) does not satisfy the minimum required flow rate of the high-pressure pump (22). For example, this occurs when the propulsion engine (E) is operating at a low load or has stopped operating while the high-pressure pump (22) is in operation.

[0068] In this embodiment, in order to ensure stable operation of the high-pressure pump (22), even if the required flow rate of the propulsion engine (E) is less than the minimum required flow rate of the high-pressure pump (22), the liquefied gas can be circulated so that the liquefied gas is supplied to the high-pressure pump (22) at a rate greater than the minimum required flow rate.

[0069] That is, if the minimum required flow rate of the high-pressure pump (22) is 100 and the required flow rate of the propulsion engine (E) is 80, then 20 liquefied gas can be circulated from downstream of the high-pressure pump (22) through the liquefied gas circulation line (L22) and the liquefied gas recovery line (L30) to the high-pressure pump (22).

[0070] Therefore, when the required flow rate of the propulsion engine (E) is less than or equal to the minimum required flow rate of the high-pressure pump (22), the liquefied gas circulation line (L22) can circulate a flow rate greater than or equal to the minimum required flow rate of the high-pressure pump (22), excluding the required flow rate of the propulsion engine (E), to ensure the minimum required flow rate of the high-pressure pump (22).

[0071] A heat exchanger (23) is provided downstream of a low-pressure pump (21) to change the temperature of the liquefied gas. Since the heat exchanger (23) can raise or lower the temperature of the liquefied gas, it may be referred to as a fuel conditioner.

[0072] For example, during the initial operation of this embodiment, the flow rate of high-temperature liquefied gas recovered from the propulsion engine (E) is large, so the heat exchanger (23) can lower the temperature of the liquefied gas, and when stable operation begins, the heat exchanger (23) can raise the temperature of the liquefied gas.

[0073] The heat exchanger (23) may be provided downstream of the high-pressure pump (22) as shown in the drawing, or, unlike the drawing, the heat exchanger (23) may be provided upstream of the high-pressure pump (22). In the latter case, the heat exchanger (23) can control the temperature of the liquefied gas to below the boiling point of the liquefied gas so that the gaseous liquefied gas does not flow into the high-pressure pump (22).

[0074] The heat exchanger (23) can perform heat exchange with liquefied gas using various heat exchange media, and for example, the heat exchange media may be seawater, fresh water, glycol water, exhaust, etc., but is not limited thereto.

[0076] The re-liquefaction unit (30) liquefies the evaporated gas generated in the cargo tank (10). The re-liquefaction unit (30) can be configured as a module in which multiple components are arranged on a single skid to form a re-liquefaction device, and the re-liquefaction unit (30) may include multiple re-liquefaction devices. However, for convenience, only one re-liquefaction device is shown in the drawing.

[0077] This re-liquefaction device includes a compressor (31), a condenser (32), a gas-liquid separator (33), an intercooler (34), and an aftercooler (35). At this time, the compressor (31), the aftercooler (35), the condenser (32), and the gas-liquid separator (33) may be arranged in series sequentially on an evaporative gas discharge line (L10), and the intercooler (34) may be provided on an evaporative gas return line (L11) connecting the gas-liquid separator (33) to the cargo tank (10).

[0078] The compressor (31) compresses the evaporated gas discharged from the cargo tank (10). The compressor (31) can raise the boiling point of the evaporated gas through compression, thereby increasing the liquefaction efficiency in the condenser (32) described below.

[0079] The compressor (31) can be configured in multiple stages, and as shown in the drawing, it can be configured in three stages or provided in various other stages. Additionally, the compressor (31) can be configured in parallel on the evaporative gas discharge line (L10) so as to be able to back up each other.

[0080] The compressor (31) can transfer the compressed evaporated gas to a condenser (32) so that it can be liquefied, or to a fuel tank (12) filled with an appropriate amount of liquefied gas. In the former case, the evaporated gas liquefied in the condenser (32) is supplied to the fuel tank (12), and in the latter case, the high-pressure evaporated gas is directly injected into the fuel tank (12) and can be cooled and liquefied by the liquefied gas inside the fuel tank (12).

[0081] A drum (not shown) may be provided upstream of the compressor (31). The drum is configured as a gas-liquid separation unit for filtering out droplets from the evaporated gas discharged from the cargo tank (10), and the droplets may be arranged to be returned to the cargo tank (10).

[0082] The drum can protect the compressor (31) by preventing liquid droplets from entering the compressor (31), and the drum may be omitted depending on the type of compressor (31).

[0083] The condenser (32) liquefies the evaporated gas generated in the cargo tank (10). A refrigerant may be used for the liquefaction of the evaporated gas, and the refrigerant may be glycol water, nitrogen, or seawater, but in the following description, it is assumed that the refrigerant of the condenser (32) is seawater.

[0084] The condenser (32) may have a two-stream structure including an evaporative gas stream into which evaporative gas compressed in the compressor (31) flows, and a refrigerant stream into which a refrigerant flows to exchange heat with the evaporative gas.

[0085] The type of such condenser (32) is not limited to Shell & Tube, PCHE, etc., and a bath type in which the evaporated gas passes through a housing in which the refrigerant is stored to exchange heat is also possible.

[0086] As previously explained, the cargo tank (10) may be provided in multiple numbers to store at least two types of liquefied gas, and the condenser (32) may be provided to liquefy all different types of evaporated gas.

[0087] When multiple cargo tanks (10) are provided for storing different types of liquefied gas, multiple condensers (32) may be provided corresponding to the types of liquefied gas. Alternatively, as previously mentioned, this embodiment may reduce the number of installed (or operational) condensers (32) by ensuring that different types of evaporated gas are integrated and delivered to a single condenser (32).

[0088] This is because the reliquefaction device of the present embodiment is capable of operating (fuel supply mode) to transfer the liquefied evaporated gas to the fuel tank (12) rather than the cargo tank (10) so that it is consumed by the propulsion engine (E).

[0089] Of course, if the liquefied evaporated gas from the condenser (32) is returned to the cargo tank (10) and no compositional contamination occurs within the cargo tank (10), the re-liquefaction device may operate in a re-liquefaction mode to deliver the liquefied evaporated gas to the cargo tank (10).

[0090] The gas-liquid separator (33) temporarily stores the evaporated gas liquefied in the condenser (32). The gas-liquid separator (33) may have a container shape or a partially expanded tube shape to function as a buffer.

[0091] The gas-liquid separator (33) can separate the liquefied evaporated gas into gaseous and liquid phases, and then transfer the liquid phase to a cargo tank (10) or a fuel tank (12). The gas-liquid separator (33) can transfer only the liquid phase to a cargo tank (10) and contain the gaseous phase internally, and can prevent the vaporization of the evaporated gas by maintaining a certain level of internal pressure.

[0092] As previously mentioned, the re-liquefaction device can operate in a fuel supply mode to transfer the liquefied evaporated gas to a fuel tank (12) rather than a cargo tank (10) in order to prevent mixing of the composition of the liquefied gas (or to supply the evaporated gas to the propulsion engine (E)). To this end, the gas-liquid separator (33) may be provided with an evaporated gas transfer line (L12) that transfers the liquid phase to the fuel tank (12).

[0093] Alternatively, in order for the re-liquefaction device to operate in a re-liquefaction mode, an evaporated gas return line (L11) may be provided from the gas-liquid separator (33) toward the cargo tank (10), and an intercooler (34) may be provided on the evaporated gas return line (L11).

[0094] Accordingly, the re-liquefaction device can operate in at least one of a re-liquefaction mode in which the liquid separated from the gas-liquid separator (33) is transferred to the cargo tank (10) via the intercooler (34), and / or a fuel supply mode in which the liquid separated from the gas-liquid separator (33) is transferred to the fuel tank (12) to be supplied to the propulsion engine (E).

[0095] That is, the reliquefaction device can also operate in a combined mode of reliquefaction mode and fuel supply mode. In the combined mode, a portion of the liquid phase separated from the gas-liquid separator (33) is transferred to the cargo tank (10) and the remainder is transferred to the fuel tank (12), and the flow rate of the liquid phase branched to the fuel tank (12) can be controlled according to the load of the propulsion engine (E).

[0096] The intercooler (34) exchanges heat between some of the liquefied evaporated gas and the rest of the condenser (32), and delivers the gaseous evaporated gas generated by heat exchange from the condenser (32) to the compressor (31).

[0097] An intercooler (34) is used to cool the evaporated gas at an intermediate stage of a compressor (31) composed of multiple stages. When the evaporated gas is compressed by the compressor (31), the temperature rises due to the heat of compression, which causes a problem of increased load on the compressor (31). Therefore, in this embodiment, an intercooler (34) can be used for intermediate cooling.

[0098] Specifically, the intercooler (34) is provided in the form of a container that stores a portion of the evaporated gas liquefied in the condenser (32), and the evaporated gas stored inside is used as a refrigerant to cool the remainder of the evaporated gas liquefied in the condenser (32) (the flow rate transferred to the cargo tank (10)).

[0099] To this end, the evaporative gas return line (L11) branches off upstream of the intercooler (34), one side delivers the evaporative gas into the intercooler (34), and the other side passes through the inside of the intercooler (34) to exchange heat with the evaporative gas stored in the intercooler (34) and is connected to the cargo tank (10).

[0100] That is, the intercooler (34) can sufficiently liquefy the evaporated gas delivered from the condenser (32) to the cargo tank (10) by exchanging heat with the evaporated gas received from the condenser (32) and stored inside.

[0101] At this time, to improve heat exchange efficiency, the portion of the evaporative gas return line (L11) passing through the inside of the intercooler (34) may be provided in the form of a coil, and to improve cooling efficiency, a pressure reducing valve (not shown in the symbol) may be provided in the portion of the evaporative gas return line (L11) that delivers the evaporative gas into the inside of the intercooler (34).

[0102] Additionally, the intercooler (34) delivers the gaseous phase of the evaporated gas stored inside to the intermediate stage of the compressor (31). The gaseous evaporated gas delivered from the intercooler (34) to the intermediate stage of the compressor (31) is in a cryogenic state adjacent to the boiling point. Therefore, the evaporated gas at the intermediate stage of the compressor (31) can be cooled by mixing with the gaseous evaporated gas delivered from the intercooler (34).

[0103] The intercooler (34) can be assigned to each intermediate stage of the multi-stage compressor (31). However, in this case, the evaporated gas is circulated by the intercooler (34), and the amount of evaporated gas transferred from the intercooler (34) to the intermediate stage of the compressor (31) may limit the amount of evaporated gas that can be introduced from the cargo tank (10) to the re-liquefaction device.

[0104] That is, the re-liquefaction device has a re-liquefaction capacity equal to the amount of evaporated gas delivered to the intermediate stage of the compressor (31) by the intercooler (34) relative to the allowable inflow of the first stage of the compressor (31). For example, when the allowable inflow of the first stage of the compressor (31) is 800, if 200 evaporated gas is circulated to the intermediate stage of the compressor (31) (between the first and second stages and between the second and third stages) by the intercooler (34), the amount of evaporated gas that the re-liquefaction device can receive from the cargo tank (10) is reduced to 400.

[0105] To improve this, the present embodiment may increase the capacity of the re-liquefaction device by allocating an intercooler (34) to only a part of the intermediate stage of the compressor (31) and providing an aftercooler (35) instead of an intercooler (34) to the remaining part of the intermediate stage of the compressor (31).

[0106] The intercooler (34) can be replaced with a separator. Similar to the gas-liquid separator (33) described earlier, the separator can separate the liquefied evaporated gas from the condenser (32) into liquid and gas phases, transferring the liquid phase to the cargo tank (10) and the gas phase to the intermediate stage of the compressor (31). In this case, since the separator simply separates the evaporated gas into liquid and does not implement heat exchange between the evaporated gases, the coil-shaped evaporated gas return line (L11) inside can be omitted.

[0107] The aftercooler (35) is provided in part of the intermediate stage of the compressor (31) and can cool the evaporated gas using a separate refrigerant. The aftercooler (35) can function as a pre-cooler from the perspective of the condenser (32).

[0108] The aftercooler (35) can use a refrigerant such as seawater, similar to the condenser (32), and can also use various other refrigerants. However, the aftercooler (35) can use a separate refrigerant supplied from the outside, rather than the liquefied gas stored in the cargo tank (10) or the evaporated gas discharged from the cargo tank (10).

[0109] To explain based on the drawing, in this embodiment, an intercooler (34) is connected between the first and second stages of the compressor (31) to circulate the vaporized gas, and an aftercooler (35) can be provided between the second and third stages of the compressor (31).

[0110] At this time, if the allowable inflow of the first stage of the compressor (31) is 800 and the circulation of the intercooler (34) is 200, then in this embodiment, the transfer of 600 evaporated gas from the cargo tank (10) to the re-liquefaction device is allowed.

[0111] That is, in this embodiment, compared to the case where the re-liquefaction device connects all intercoolers (34) to each intermediate stage of the compressor (31), at least one intercooler (34) can be replaced with an aftercooler (35) to increase the re-liquefaction capacity.

[0112] The re-liquefaction unit (30) of this embodiment can be operated in two modes. For example, the re-liquefaction unit (30) can be operated in a re-liquefaction mode in which evaporated gas liquefied in the condenser (32) is transferred to the cargo tank (10) via the intercooler (34), and in a fuel supply mode in which evaporated gas is transferred upstream or downstream of the condenser (32) to the propulsion engine (E).

[0113] Specifically, in the re-liquefaction mode, the multi-stage compressed evaporated gas is liquefied after passing through the condenser (32), then passes through the gas-liquid separator (33) and is delivered to the intercooler (34). At this time, the evaporated gas is branched upstream of the intercooler (34), and some of the evaporated gas can be filled into the intercooler (34), while the remaining evaporated gas passes through the intercooler (34) to exchange heat without mixing with the evaporated gas filled into the intercooler (34). The evaporated gas passing through the intercooler (34) can be cooled or supercooled to maintain a stable liquid state and then returned to the cargo tank (10).

[0114] On the other hand, the fuel supply mode can transfer multi-stage compressed evaporated gas upstream of the condenser (32) to the fuel tank (12), or transfer multi-stage compressed and condensed evaporated gas to the fuel tank (12) and then transfer it to the propulsion engine (E) by the high-pressure pump (22).

[0115] The fuel supply mode can be operated when it is not desirable to return the liquefied evaporated gas to the cargo tank (10), or when the load of the propulsion engine (E) is high and the liquefied gas stored in the fuel tank (12) alone cannot satisfy the required flow rate of the propulsion engine (E).

[0116] For example, when propane and butane are stored in a cargo tank (10), if a problem occurs in the re-liquefaction device processing butane and operation stops, butane can be liquefied using another re-liquefaction device processing propane. At this time, since there is a risk that propane remaining in the re-liquefaction device processing propane may be mixed into butane, a fuel supply mode may be implemented in which the liquefied butane is delivered to the fuel tank (12) instead of being delivered to the cargo tank (10).

[0117] In addition to this, in various situations where delivery to a fuel tank (12) or the like is preferable to delivery to a cargo tank (10), it is possible to operate in a fuel supply mode instead of a re-liquefaction mode. Furthermore, as mentioned above, it is also possible to operate in a combined mode that combines the re-liquefaction mode and the fuel supply mode.

[0119] The fuel recovery unit (40) recovers liquid liquefied gas discharged from the propulsion engine (E). The fuel recovery unit (40) can recover the liquid liquefied gas upstream of the high-pressure pump (22), and for this purpose, a liquefied gas recovery line (L30) is provided from the propulsion engine (E) to the liquefied gas supply line (L20) upstream of the high-pressure pump (22).

[0120] Unlike commercial engines (ME-GI, XDF, etc.) that receive and consume LNG in the gaseous state, the propulsion engine (E) (ME-LGI, etc.) in the present invention has a structure that receives and consumes LPG, etc. in the liquid state and discharges excess liquid fuel.

[0121] This is because, unlike in the case of gaseous fuel, fine control of the fuel supply amount is not easy in the case of liquid fuel, and as the propulsion engine (E) receives a sufficient amount of liquid fuel, excess fuel is generated.

[0122] However, the liquefied gas recovered from the propulsion engine (E) is not the liquefied gas before it was introduced into the propulsion engine (E), but is the liquefied gas that has passed through the interior of the propulsion engine (E), and is in a state having a temperature / pressure corresponding to the required pressure of the propulsion engine (E) (e.g., around 45 bar, 50 degrees or higher), and the lubricating oil used in the propulsion engine (E) may be mixed into the liquefied gas.

[0123] That is, since the excess liquefied gas recovered from the propulsion engine (E) contains lubricating oil, it is preferable not to transfer the recovered liquefied gas to the cargo tank (10) in order to prevent cargo contamination.

[0124] Accordingly, the liquefied gas recovery line (L30), which is connected to the propulsion engine (E) to recover excess liquefied gas, can transfer the excess liquefied gas returned from the propulsion engine (E) to a high-pressure pump (22) instead of a cargo tank (10) so that it can be recirculated to the propulsion engine (E).

[0125] That is, the liquefied gas recovery line (L30) passes through the interior of the propulsion engine (E) and transfers the excess liquid liquefied gas mixed with lubricating oil used in the propulsion engine (E) to the liquefied gas supply line (L20) upstream of the high-pressure pump (22) so that it is recirculated into the propulsion engine (E), thereby preventing the liquefied gas inside the cargo tank (10) from being contaminated by lubricating oil.

[0126] This fuel recovery unit (40) includes a pressure reducing valve and a cooler (41) provided in the liquefied gas recovery line (L30), and may also include a collection tank (42) and a knockout drum (43).

[0127] The pressure reducing valve reduces the pressure of excess liquid gas mixed with lubricating oil that is discharged from the propulsion engine (E). The pressure reducing valve may be a Joule-Thomson valve and may be configured to form a fuel supply train (FVT) together with the fuel supply valve.

[0128] This pressure reducing valve can reduce the pressure of the high-pressure (approximately 30 to 50 bar) liquefied gas recovered from the propulsion engine (E) to match the suction pressure of the high-pressure pump (22).

[0129] The cooler (41) cools the liquefied gas depressurized at the pressure reducing valve in the liquefied gas recovery line (L30) so that it flows into the high-pressure pump (22) in liquid form. The cooler (41) can utilize various refrigerants that are not limited and can cool the liquefied gas to below the boiling point of the depressurized liquefied gas. For example, the cooler (41) can use seawater as a refrigerant, and in this case, the heat exchanger (23) and the cooler (41) can be integrated and connected by a single refrigerant supply unit.

[0130] Cooling by the cooler (41) can be performed by taking into account the mixing with the liquefied gas delivered from the fuel tank (12) to the high-pressure pump (22), so the cooler (41) can also be controlled to cool the liquefied gas to a temperature slightly higher than the boiling point of the depressurized liquefied gas.

[0131] The liquid (or near-liquid) liquefied gas cooled by the cooler (41) is mixed upstream of the high-pressure pump (22) in the liquefied gas supply line (L20) through the liquefied gas recovery line (L30), and a mixer (not shown) may be provided at the point where the liquefied gas recovery line (L30) is connected to the liquefied gas supply line (L20).

[0132] The previously described liquefied gas circulation line (L22) can be branched from the liquefied gas supply line (L20) downstream of the high-pressure pump (22) and connected to the upstream of the cooler (41) via the liquefied gas recovery line (L30) so as to be connected between the propulsion engine (E) and the cooler (41) downstream of the high-pressure pump (22).

[0133] This is to suppress the fact that the temperature of the high-pressure pump (22) itself may rise unnecessarily if the heated liquefied gas is continuously circulated, as the liquefied gas is pumped and heated due to the operation of the high-pressure pump (22). That is, in this embodiment, by using a cooler (41), the degree of heat generation of the high-pressure pump (22) during the circulation of liquefied gas through the liquefied gas circulation line (L22) can be limited to within a preset value.

[0134] Therefore, the high-pressure pump (22) can continuously pump liquefied gas at a minimum required flow rate, and the excess liquefied gas recovered by the liquefied gas circulation line (L22) is circulated to the high-pressure pump (22) via the cooler (41), so that the high-pressure pump (22) can be prevented from overheating.

[0135] The collection tank (42) collects a portion of the liquefied gas returned from the propulsion engine (E). The collection tank (42) may be provided by branching off from the liquefied gas recovery line (L30) which is connected from the propulsion engine (E) to the liquefied gas supply line (L20) upstream of the high-pressure pump (22), and the liquefied gas collection line (L31) may be extended from the liquefied gas recovery line (L30) to the collection tank (42).

[0136] At this time, the liquefied gas collection line (L31) extends from between the pressure reducing valve and the cooler (41) in the liquefied gas recovery line (L30) and is connected to the collection tank (42), and can also join from the collection tank (42) to the liquefied gas recovery line (L30) upstream of the cooler (41). That is, the liquefied gas collection line (L31) can be provided partially in parallel with the liquefied gas recovery line (L30) and can be provided so that the collection tank (42) is provided.

[0137] The collection tank (42) separates the recovered liquefied gas into gas and liquid. Since cavitation problems may occur if gaseous liquefied gas is introduced into the high-pressure pump (22), the present invention allows the liquefied gas flowing along the liquefied gas recovery line (L30) to pass through the collection tank (42) as needed to be separated into gas and liquid, thereby blocking the inflow of gaseous liquefied gas into the high-pressure pump (22).

[0138] That is, the collection tank (42) collects the liquefied gas from the liquefied gas recovery line (L30) and delivers only the liquid liquefied gas to the high-pressure pump (22), thereby ensuring stable operation of the high-pressure pump (22).

[0139] The knockout drum (43) receives the liquefied gas recovered from the propulsion engine (E) from the collection tank (42) and can filter out impurities (such as lubricating oil) contained in the liquefied gas. A liquefied gas processing line (L32) can be connected from the collection tank (42) to the knockout drum (43), and the liquefied gas processing line (L32) can transfer liquid liquefied gas transferred from the collection tank (42) to the liquefied gas recovery line (L30) to the knockout drum (43), in addition to the gaseous liquefied gas separated from the collection tank (42).

[0140] The knockout drum (43) separates lubricating oil from the liquefied gas introduced into it. Specifically, the knockout drum (43) discharges the liquefied gas as a gaseous state and discharges the lubricating oil as a liquid state. That is, the knockout drum (43) implements a gas-liquid separation function similar to the collection tank (42).

[0141] However, the knockout drum (43) may use a heating element such as tracing to promote the vaporization of liquefied gas, and the tracing may be configured to use a medium such as steam or seawater as a heat source or to heat using electricity.

[0142] The knockout drum (43) heats the liquefied gas mixed with lubricating oil in the heating section, discharges the liquefied gas to a vent mast (not shown), and drains the lubricating oil from the bottom for disposal (recycling).

[0143] For reference, a vent mast (not shown) releases material that needs to be vented to the outside between the cargo tank (10) and the propulsion engine (E) into the atmosphere. The vent mast is provided on the deck of the ship and has a certain height so as to protect the crew on the deck.

[0144] The vent mast can be connected to the collection tank (42) or the knockout drum (43), as well as to the evaporative gas discharge line (L10), the liquefied gas supply line (L20), the fuel tank (12), etc. Through this, the vent mast protects the system by enabling external discharge during normal operation or emergency situations such as the shutdown of the propulsion engine (E).

[0145] In addition, the vent mast can discharge purging gas to the outside during purging of the evaporative gas discharge line (L10), liquefied gas supply line (L20), etc. At this time, the purging gas may be nitrogen gas or inert gas, etc.

[0147] In this way, the present embodiment can resolve the problem of the liquefied gas composition being contaminated when different types of liquefied gas are reliquefied and returned to the cargo tank (10), by reliquefiing the evaporated gas generated in the cargo tank (10) and then delivering it to the fuel tank (12) to be supplied to the propulsion engine (E), and can reduce the number of installed or operating condensers (32).

[0149] FIG. 2 is a conceptual diagram of a gas treatment system according to a second embodiment of the present invention.

[0150] The following description will focus on the differences between this embodiment and the preceding embodiment, and any parts omitted will be replaced by the preceding content. It should be noted that this applies to the embodiments described later as well.

[0151] Referring to FIG. 2, the gas treatment system (1) according to the second embodiment of the present invention allows the re-liquefaction unit (30) to liquefy the evaporated gas and deliver it to the high-pressure pump (22). Specifically, the re-liquefaction device can deliver the liquefied evaporated gas to the fuel tank (12) as in the previous embodiment, or deliver it to the liquefied gas supply line (L20) between the fuel tank (12) and the high-pressure pump (22).

[0152] To this end, in addition to the evaporative gas return line (L11) and the evaporative gas delivery line (L12) as lines for delivering the liquid phase separated from the gas-liquid separator (33), an evaporative gas supply line (L13) may be provided. One end of the evaporative gas supply line (L13) may extend from the gas-liquid separator (33) or the evaporative gas delivery line (L12), and the other end may be connected between the high-pressure pump (22) and the low-pressure pump (21) in the liquefied gas supply line (L20).

[0153] The point where the evaporated gas delivery line (L12) is connected to the liquefied gas supply line (L20) may be upstream of or the same point where the liquefied gas recovery line (L30) is connected to the liquefied gas supply line (L20). Accordingly, the high-pressure pump (22) can supply the liquefied gas supplied from the low-pressure pump (21), the excess liquefied gas recovered through the liquefied gas recovery line (L30), and the liquid evaporated gas delivered from the re-liquefaction device to the propulsion engine (E) by pressurizing them.

[0154] When the liquefied evaporated gas from the condenser (32) is supplied to the high-pressure pump (22) after being combined with the liquefied gas recovered from the liquefied gas recovery line (L30) by bypassing the fuel tank (12) through the evaporated gas supply line (L13), the inflow of gas into the high-pressure pump (22) can still be prevented.

[0155] Specifically, in this embodiment, the inlet pressure of the high-pressure pump (22) and the evaporated gas pressure downstream of the condenser (32) (which may be the internal pressure of the gas-liquid separator (33)) are controlled to be the same, so that the boiling point of the liquefied gas flowing in the liquefied gas supply line (L20) upstream of the high-pressure pump (22) and the boiling point of the evaporated gas flowing in the evaporated gas supply line (L13) are formed to be the same. That is, no separate pressurizing / compressing means is provided on the evaporated gas supply line (L13) between the gas-liquid separator (33) and the high-pressure pump (22).

[0156] However, the inflow pressure of the high-pressure pump (22) is the same as the pressure downstream of the pressure reducing valve on the liquefied gas recovery line (L30). That is, the boiling point of the liquid liquefied gas flowing in the liquefied gas recovery line (L30) is also the same as the boiling point of the evaporated gas on the evaporated gas supply line (L13).

[0157] At this time, the condenser (32) of the re-liquefaction device and the cooler (41) on the liquefied gas recovery line (L30) can use the same refrigerant. That is, the condenser (32) and the cooler (41) are supplied with a refrigerant having the same conditions (temperature), thereby enabling the cooling of the evaporated gas / liquid liquefied gas to approximately the same temperature.

[0158] Accordingly, in this embodiment, the cooler (41) of the fuel recovery unit (40) cools the liquid liquefied gas having a first pressure with the first refrigerant so as to prevent vaporization at the inlet end of the high-pressure pump (22), and the condenser (32) of the re-liquefaction unit (30) also cools the evaporated gas having a first pressure with the first refrigerant, so the cooler (41) and the condenser (32) can be controlled in conjunction with each other so as not to allow gas to flow into the high-pressure pump (22).

[0159] In other words, in this embodiment, even if the inflow pressure of the high-pressure pump (22) is low, the condenser (32) condenses the evaporated gas using the same refrigerant as the cooler (41) at the same pressure as the liquid liquefied gas recovered from the fuel recovery unit (40), so the operational stability of the high-pressure pump (22) can be guaranteed even if the re-liquefaction device bypasses the fuel tank (12) and directly delivers the evaporated gas to the high-pressure pump (22).

[0160] Accordingly, when the re-liquefaction device of the present embodiment is operated in fuel supply mode, in addition to delivering the liquid phase separated from the gas-liquid separator (33) to the fuel tank (12), it can be delivered to the liquefied gas supply line (L20) upstream of the high-pressure pump (22) to be supplied to the propulsion engine (E), and the flow control to the evaporated gas delivery line (L12) or the evaporated gas supply line (L13) can be controlled according to various variables such as the amount of evaporated gas discharged from the cargo tank (10), the load of the propulsion engine (E), and the internal pressure of the fuel tank (12).

[0162] In addition, the re-liquefaction device of the present embodiment includes a bypass line (L14). The bypass line (L14) allows at least a portion of the evaporated gas to bypass the condenser (32) and be supplied to the gas-liquid separator (33), and a bypass valve (36) for flow control may be provided in the bypass line (L14).

[0163] When the temperature of the refrigerant used by the condenser (32) is low, the evaporated gas may be subcooled by the refrigerant. If the subcooled liquid evaporated gas flows downstream of the condenser (32) into the gas-liquid separator (33), it may cause a drop in internal pressure of the gas-liquid separator (33).

[0164] That is, the refrigerant temperature in the condenser (32) can determine the degree of cooling of the evaporated gas, and this determines the internal pressure in the gas-liquid separator (33). The internal pressure of the gas-liquid separator (33) may be the pressure of the evaporated gas delivered to the high-pressure pump (22) through the evaporated gas supply line (L13). If the internal pressure of the gas-liquid separator (33) is low, the boiling point of the evaporated gas is lowered, and there is a concern about vaporization in the high-pressure pump (22).

[0165] Therefore, since the refrigerant temperature of the condenser (32) can lead to a vaporization problem at the inlet end of the high-pressure pump (22), this embodiment can implement control that increases the pressure of the gas-liquid separator (33) according to the refrigerant temperature.

[0166] To this end, the bypass line (L14) can be configured so that at least some of the evaporated gas bypasses the condenser (32) and is supplied to the gas-liquid separator (33) by opening the bypass valve (36) to account for pressure fluctuations of the evaporated gas transferred from the gas-liquid separator (33) to the high-pressure pump (22) according to the temperature of the refrigerant.

[0167] When high-temperature vaporized gas bypassing the condenser (32) flows into the gas-liquid separator (33), the internal pressure of the gas-liquid separator (33) increases, so the pressure of the liquid vaporized gas transferred from the gas-liquid separator (33) to the liquefied gas supply line (L20) through the vaporized gas supply line (L13) increases, and the boiling point increases.

[0168] Therefore, in this embodiment, by controlling whether to bypass the condenser (32) with the refrigerant temperature as a variable, the liquid evaporated gas transferred from the re-liquefaction device to the high-pressure pump (22) is prevented from re-vaporizing, thereby preventing cavitation in the high-pressure pump (22) in advance.

[0169] In addition, as the internal pressure of the gas-liquid separator (33) is controlled to correspond to the pressure of the liquid liquefied gas recovered from the liquefied gas recovery line (L30), as described above, the condenser (32) and the cooler (41) can operate using the same refrigerant, allowing only the liquid phase to be stably introduced into the inlet end of the high-pressure pump (22).

[0171] As such, if the temperature of the refrigerant used in the condenser (32) is low, there is a risk that the pressure of the liquid evaporated gas transferred from the re-liquefaction device to the high-pressure pump (22) will be low and vaporize and flow into the high-pressure pump (22). In this embodiment, the above problem can be effectively resolved by applying a control that bypasses the condenser (32) depending on the refrigerant temperature.

[0173] FIG. 3 is a conceptual diagram of a gas treatment system according to a third embodiment of the present invention.

[0174] Referring to FIG. 3, the gas treatment system (1) according to the third embodiment of the present invention may omit the fuel tank (12) compared to the preceding second embodiment, and the liquefied gas delivery line (L21) or the evaporated gas delivery line (L12), etc. may also be omitted.

[0175] In this case, a liquefied gas supply line (L20) can be directly connected from the cargo tank (10) to the propulsion engine (E), and a low-pressure pump (21), a high-pressure pump (22), a heat exchanger (23), etc. can be provided on the liquefied gas supply line (L20).

[0176] The low-pressure pump (21) can be positioned downstream of the transfer pump (11) in the liquefied gas supply line (L20) as shown in the drawing, but the low-pressure pump (21) can be omitted if the discharge pressure of the transfer pump (11) is configured to correspond to the inflow pressure of the high-pressure pump (22).

[0177] In addition, in this embodiment, the reliquefaction device can transfer the liquefied evaporated gas to the liquefied gas supply line (L20) between the cargo tank (10) and the high-pressure pump (22). At this time, in the fuel supply mode, the reliquefaction device can transfer the liquid phase separated from the gas-liquid separator (33) to the liquefied gas supply line (L20) upstream of the high-pressure pump (22) so that it is supplied to the propulsion engine (E).

[0178] In addition, the re-liquefaction device, as in the previous embodiment, liquefies the evaporated gas and delivers it to the high-pressure pump (22), but depending on the temperature of the refrigerant, a portion of the evaporated gas may bypass the condenser (32), pass through the gas-liquid separator (33), and be delivered to the liquefied gas supply line (L20) upstream of the high-pressure pump (22).

[0180] FIG. 4 is a conceptual diagram of a gas treatment system according to the fourth embodiment of the present invention.

[0181] Referring to FIG. 4, the gas treatment system (1) according to the fourth embodiment of the present invention omits the evaporative gas supply line (L13) compared to the preceding second embodiment, and the recovery point of the liquefied gas is set to the fuel tank (12).

[0182] In this embodiment, the reliquefaction device can transfer the liquefied evaporated gas to the fuel tank (12). This can be accomplished by the evaporated gas transfer line (L12) as previously mentioned. That is, the reliquefaction device can transfer the liquid phase separated from the gas-liquid separator (33) in the fuel supply mode to the fuel tank (12) so that it can be supplied to the propulsion engine (E).

[0183] However, in this embodiment, the liquefied gas recovery line (L30) of the fuel recovery unit (40) may be extended from the propulsion engine (E) and connected to the inside of the fuel tank (12). Thus, the liquefied gas recovery line (L30) can deliver the excess liquid liquefied gas mixed with lubricating oil used in the propulsion engine (E) to the fuel tank (12). At this time, the liquid liquefied gas introduced into the fuel tank (12) can be reintroduced to the propulsion engine (E) through the low-pressure pump (21) and the high-pressure pump (22).

[0184] The fuel tank (12) of this embodiment is configured so that excess liquefied gas is directly recovered inside, and the internal pressure may be set higher than that of the preceding second embodiment. That is, the internal pressure of the fuel tank (12) can be adjusted to a pressure at which the recovered liquefied gas does not vaporize, and in this case, if the internal pressure of the fuel tank (12) corresponds to the inflow pressure of the high-pressure pump (22), the low-pressure pump (21) may be omitted.

[0185] As in the second and third embodiments, this embodiment can also control the flow of liquid evaporated gas according to the temperature of the refrigerant used in the condenser (32). Specifically, in this embodiment, the re-liquefaction device can ensure that at least some of the evaporated gas bypasses the condenser (32) and is supplied to the fuel tank (12) in preparation for pressure fluctuations of the evaporated gas delivered to the fuel tank (12) according to the temperature of the refrigerant.

[0186] In this embodiment, liquid evaporated gas is transferred to a high-pressure pump (22) via a fuel tank (12), and a low-pressure pump (21) may be provided between the fuel tank (12) and the high-pressure pump (22). Accordingly, the refrigerant temperature of the condenser (32) affects the internal pressure of the fuel tank (12), which can affect the inflow pressure of the low-pressure pump (21), and this can indirectly affect the inflow pressure of the high-pressure pump (22). Of course, if the low-pressure pump (21) is omitted, the internal pressure of the fuel tank (12) can directly affect the inflow pressure of the high-pressure pump (22).

[0187] Accordingly, the re-liquefaction device of the present embodiment can be configured so that some of the evaporated gas bypasses the condenser (32) and passes through the gas-liquid separator (33) to supply it to the fuel tank (12) in order to account for pressure fluctuations of the evaporated gas transferred from the gas-liquid separator (33) to the fuel tank (12) according to the refrigerant temperature. That is, the present embodiment can simultaneously control the internal pressure of the gas-liquid separator (33) and the internal pressure of the fuel tank (12) by controlling the bypass of the evaporated gas.

[0188] Alternatively, in the case of this embodiment, the liquid vaporized gas liquefied in the condenser (32) is transferred to the high-pressure pump (22) via the fuel tank (12), so the fuel tank (12) can perform a gas-liquid separation function, and thus the gas-liquid separator (33) may be omitted from the re-liquefaction device.

[0190] FIG. 5 is a conceptual diagram of a gas treatment system according to the fifth embodiment of the present invention.

[0191] Referring to FIG. 5, the gas treatment system (1) according to the fifth embodiment of the present invention may have a different connection point of the evaporated gas supply line (L13) compared to the second embodiment.

[0192] The evaporative gas supply line (L13) of this embodiment can transfer evaporative gas upstream of the gas-liquid separator (33) to the liquefied gas supply line (L20) between the fuel tank (12) and the high-pressure pump (22). That is, one end of the evaporative gas supply line (L13) is connected between the condenser (32) and the gas-liquid separator (33) in the re-liquefaction device, and the other end can be connected upstream of the high-pressure pump (22) in the liquefied gas supply line (L20).

[0193] This evaporative gas supply line (L13) is provided to prepare for internal pressure fluctuations in the gas-liquid separator (33) depending on the temperature of the refrigerant. Specifically, the evaporative gas supply line (L13) can directly connect the upstream of the high-pressure pump (22) and the upstream of the gas-liquid separator (33) to prevent insufficient pressure when the evaporative gas is supercooled in the condenser (32) and flows into the high-pressure pump (22) via the gas-liquid separator (33) when the temperature of the refrigerant is lower than a reference value.

[0194] In this case, the compressor (31) of the re-liquefaction device is in a situation where the condenser (32) and the high-pressure pump (22) are arranged in sequence downstream along the flow of the evaporated gas, so the pressure at the inlet end of the high-pressure pump (22) matches the pressure at the discharge end of the compressor (31). Therefore, the compressor (31) receives the inlet pressure of the high-pressure pump (22) (the pressure of the liquid liquefied gas recovered through the liquefied gas recovery line (L30)) as resistance, and its operation is controlled, so that the discharge pressure of the compressor (31) can be adjusted upward.

[0195] That is, in this embodiment, when the temperature of the refrigerant used in the condenser (32) is too low, the downstream side of the condenser (32) and the upstream side of the high-pressure pump (22) are directly connected to the evaporative gas supply line (L13), so that the discharge end of the compressor (31) is resisted by the inflow pressure of the high-pressure pump (22), and the discharge pressure of the compressor (31) is controlled to correspond to the inflow pressure of the high-pressure pump (22).

[0196] Therefore, in this embodiment, instead of bypassing heat exchange with the low-temperature refrigerant, the gas-liquid separator (33) is bypassed to connect the downstream of the condenser (32) and the upstream of the high-pressure pump (22) so that they have the same pressure, so that the discharge pressure of the compressor (31) is matched to the inflow pressure of the high-pressure pump (22).

[0198] In this way, the present embodiment is designed to prevent the pressure of the liquid vaporized gas from becoming inappropriate when the temperature of the refrigerant used in the condenser (32) is too low. This is achieved by connecting the downstream of the compressor (31) to the upstream of the high-pressure pump (22), thereby ensuring that the discharge pressure of the compressor (31) matches the inflow pressure of the high-pressure pump (22), thereby effectively preventing vaporization in the high-pressure pump (22).

[0200] FIG. 6 is a conceptual diagram of a gas treatment system according to the sixth embodiment of the present invention.

[0201] Referring to FIG. 6, the gas treatment system (1) according to the 6th embodiment of the present invention may omit the fuel tank (12) compared to the 5th embodiment, and the liquefied gas delivery line (L21) or the evaporated gas delivery line (L12), etc. may also be omitted.

[0202] In this case, a liquefied gas supply line (L20) can be directly connected from the cargo tank (10) to the propulsion engine (E), and a low-pressure pump (21), a high-pressure pump (22), a heat exchanger (23), etc., can be provided on the liquefied gas supply line (L20). As mentioned in the third embodiment, the low-pressure pump (21) may be omitted.

[0203] In this embodiment, the reliquefaction device can transfer the liquefied evaporated gas to the liquefied gas supply line (L20) between the cargo tank (10) and the high-pressure pump (22). At this time, in the fuel supply mode, the reliquefaction device can transfer the liquid phase separated from the gas-liquid separator (33) to the liquefied gas supply line (L20) upstream of the high-pressure pump (22) so that it is supplied to the propulsion engine (E).

[0204] In addition, the re-liquefaction device liquefies the evaporated gas and delivers it to the high-pressure pump (22), just as in the previous embodiment, and connects the downstream of the condenser (32) and the upstream of the high-pressure pump (22) according to the temperature of the refrigerant, so that the discharge pressure of the compressor (31) can be matched to the inflow pressure of the high-pressure pump (22).

[0206] FIG. 7 is a conceptual diagram of a gas treatment system according to the seventh embodiment of the present invention.

[0207] Referring to FIG. 7, the gas treatment system (1) according to the seventh embodiment of the present invention has a change in the detailed configuration of the re-liquefaction device compared to the preceding embodiments, and other configurations may include at least one of the configurations of the preceding embodiments.

[0208] The re-liquefaction device of the present embodiment includes a compressor (31), a condenser (32), a gas-liquid separator (33), an aftercooler (35), and an evaporative gas heat exchanger (37). Since the compressor (31), the condenser (32), and the gas-liquid separator (33) are as described above, a detailed description is omitted.

[0209] The evaporative gas heat exchanger (37) exchanges heat between the evaporative gas transferred from the cargo tank (10) to the compressor (31) and the evaporative gas liquefied in the condenser (32). Specifically, the evaporative gas heat exchanger (37) may have a two-stream structure having a stream of evaporative gas transferred from the cargo tank (10) to the compressor (31) and a stream of evaporative gas transferred from the gas-liquid separator (33) to the cargo tank (10).

[0210] For example, the evaporative gas heat exchanger (37) may be provided on the evaporative gas return line (L11) to have one stream parallel to the evaporative gas discharge line (L10) and another stream parallel to the evaporative gas return line (L11), and may be provided to replace the intercooler (34) described above. Of course, the evaporative gas heat exchanger (37) may be added to the preceding embodiment having the intercooler (34).

[0211] Since the evaporated gas liquefied in the condenser (32) is compressed in the compressor (31), its temperature may be higher than the boiling point at atmospheric pressure, even though it is in a liquid state. On the other hand, the evaporated gas discharged from the cargo tank (10) may have a pressure at the level of atmospheric pressure and a temperature close to the boiling point.

[0212] Accordingly, the evaporative gas heat exchanger (37) can cool the evaporative gas transferred from the gas-liquid separator (33) by exchanging heat with the low-temperature evaporative gas discharged from the cargo tank (10). At this time, the pressure of the evaporative gas, which is the object of cooling, and the evaporative gas, which is the subject of cooling, may be different from each other in the evaporative gas heat exchanger (37), and the pressure difference may be formed by the differential pressure between the internal pressure in the cargo tank (10) and the internal pressure of the gas-liquid separator (33).

[0213] A pressure reducing valve (not shown) is provided at at least one point upstream or downstream of the evaporative gas heat exchanger (37) on the evaporative gas return line (L11) to reduce the pressure of the evaporative gas compressed by the compressor (31) and enable additional cooling.

[0214] A reliquefaction device including such an evaporative gas heat exchanger (37) can be operated in a fuel supply mode or a reliquefaction mode as described in the preceding first embodiment. That is, the reliquefaction device can be operated in a reliquefaction mode in which the liquid separated from the gas-liquid separator (33) is transferred to the cargo tank (10) via the evaporative gas heat exchanger (37) provided in the evaporative gas return line (L11), and / or in a fuel supply mode in which the liquid separated from the gas-liquid separator (33) is transferred to the fuel tank (12) through the evaporative gas transfer line (L12) to be supplied to the propulsion engine (E).

[0216] In this way, the present embodiment can simplify the structure of the re-liquefaction device by using an evaporative gas heat exchanger (37) instead of an intercooler (34), and since the circulation of evaporative gas through the intercooler (34) is omitted, the re-liquefaction capacity of the re-liquefaction device can be increased.

[0218] In addition to the embodiments described above, the present invention may include additional embodiments such as a combination of at least one embodiment and the prior art, and a combination of at least two or more embodiments.

[0219] 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 apparent that modifications or improvements can be made by those skilled in the art within the technical scope of the invention.

[0220] 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. Explanation of the symbols

[0221] 1: Gas processing system 10: Cargo tank 11: Transfer pump 12: Fuel tank 20: Fuel supply unit 21: Low-pressure pump 22: High-pressure pump 23: Heat exchanger 30: Re-liquefaction unit 31: Compressor 32: Condenser 33: Gas-liquid separator 34: Intercooler 35: Aftercooler 36: Bypass valve 37: Evaporative gas heat exchanger 40: Fuel recovery unit 41: Cooler 42: Collection Tank 43: Knockout Drum L10: Evaporative Gas Discharge Line L11: Evaporative Gas Return Line L12: Evaporative Gas Transfer Line L13: Evaporative Gas Supply Line L14: Bypass line L20: Liquefied gas supply line L21: Liquefied gas delivery line L22: Liquefied gas circulation line L30: Liquefied gas recovery line L31: Liquefied gas collection line L32: Liquefied gas processing line E: Propulsion engine

Claims

Claim 1 A system for processing liquefied gas, which is a heavy hydrocarbon or ammonia, comprising: a fuel tank for storing the liquefied gas as fuel to be supplied to a propulsion engine of a ship; a liquefied gas supply line for supplying the liquefied gas from the fuel tank in liquid form to the propulsion engine and being equipped with a high-pressure pump; a re-liquefaction device for liquefying the evaporated gas generated in a cargo tank for storing the liquefied gas and transferring it to the fuel tank; a liquefied gas recovery line for recovering the liquid liquefied gas discharged from the propulsion engine upstream of the high-pressure pump; and a fuel recovery unit for recovering the liquid liquefied gas discharged from the propulsion engine, wherein the re-liquefaction device comprises: a compressor for compressing the evaporated gas discharged from the cargo tank; a condenser for cooling and liquefying the compressed evaporated gas with a refrigerant; and a buffer for temporarily storing the evaporated gas liquefied in the condenser. A gas treatment system comprising: a vapor gas supply line that delivers vaporized gas upstream of the buffer to the liquefied gas supply line between the fuel tank and the high-pressure pump; further comprising a liquefied gas collection line branched from the liquefied gas recovery line connected to the liquefied gas supply line upstream of the high-pressure pump from the propulsion engine; and the fuel recovery unit comprising a collection tank connected to the liquefied gas collection line. Claim 2 A gas treatment system according to claim 1, wherein the liquefied gas recovery line is provided with a pressure reducing valve for reducing the pressure of excess liquid liquefied gas mixed with lubricating oil discharged from the propulsion engine, and the excess liquid liquefied gas mixed with lubricating oil used in the propulsion engine is transferred to the liquefied gas supply line upstream of the high-pressure pump while passing through the interior of the propulsion engine so as to be recirculated into the propulsion engine. Claim 3 In claim 2, the liquefied gas recovery line is a gas treatment system provided with a cooler that cools the liquefied gas depressurized by the pressure reducing valve and allows it to flow into the high-pressure pump in a liquid state. Claim 4 A gas treatment system according to claim 1, wherein the evaporative gas supply line connects the upstream of the high-pressure pump and the upstream of the buffer to regulate the discharge pressure of the compressor in preparation for internal pressure fluctuations of the buffer according to the temperature of the refrigerant. Claim 5 In claim 1, the buffer is a gas-liquid separator that separates liquefied evaporated gas from the condenser, in a gas treatment system. Claim 6 In claim 5, the re-liquefaction device comprises an intercooler that exchanges heat between a portion of the evaporated gas liquefied in the condenser and the remainder, and delivers the evaporated gas generated by the heat exchange to the compressor, in a gas treatment system. Claim 7 In claim 6, the reliquefaction device is a gas processing system that operates in at least one of a reliquefaction mode in which the liquid separated from the gas-liquid separator is transferred to the cargo tank via the intercooler, and a fuel supply mode in which the liquid separated from the gas-liquid separator is transferred to the fuel tank to be supplied to the propulsion engine. Claim 8 A vessel characterized as being a liquefied gas carrier having the gas processing system of any one of claims 1 to 7.

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