Gas treatment system and vessel including the same

Abstract

To provide a gas treatment system for generating propulsion force by using liquefied petroleum gas and ammonia, and a vessel including the same.SOLUTION: A system for processing liquefied gas which is heavy hydrocarbon or ammonia includes: a liquefied gas supply line L20 for supplying liquefied gas stored in a cargo tank 10 to a propulsion engine E through a high pressure pump 22; and a reliquefying device transmitting evaporation gas generated in the cargo tank 10 to the high pressure pump 22 by liquefying. The reliquefying device includes: a condenser 32 for liquefying the evaporation gas by cooling with a coolant; and a buffer for temporarily storing the evaporation gas liquefied by the condenser 32. The reliquefying device has a bypass line L14 in which at least a part of the evaporation gas is supplied to the buffer by bypassing the condenser 32, in preparation for pressure fluctuation of the evaporation gas transmitted from the buffer to the high pressure pump 22 according to a temperature of the coolant.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a gas treatment system and a ship including the same.

Background Art

[0002] Generally, liquefied petroleum gas, i.e., LPG (Liquefied petroleum gas), is mainly composed of hydrocarbons with low boiling points such as propane and butane among the components of petroleum, and is obtained by pressurizing the gas at normal temperature to liquefy it. Such liquefied petroleum gas is filled into small and light pressure vessels (cylinders) and widely used as fuel for household, business, industrial, automotive, etc.

[0003] Liquefied petroleum gas is extracted in a gaseous state at the production site, liquefied and stored through liquefied petroleum gas treatment facilities, and then transported to land while maintaining the liquid phase by a liquefied petroleum gas carrier, and then supplied to the demand side in various forms such as gas.

[0004] The boiling point of such liquefied petroleum gas is around about -50°C, and a liquefied petroleum gas carrier for transporting liquefied petroleum gas must maintain a lower temperature than this. Therefore, low-temperature steel (Low Temperature Carbon Steel and Nickel Steel) resistant to low temperatures is used for the storage tank for storing liquefied petroleum gas, and a reliquefaction facility is also provided for the liquefied petroleum gas carrier.

[0005] Conventionally, such a liquefied petroleum gas carrier has generated propulsion force by operating an engine using diesel oil. However, in the process of burning diesel oil in a ship propulsion engine, harmful components such as nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO2) are generated, and the problem of environmental pollution is caused by the release of these harmful components into the atmosphere.

[0006] Therefore, recently, in order to significantly reduce the exhaust pollution level compared to the case of using diesel oil, the development of engines that operate using liquefied petroleum gas and the development of various systems for supplying liquefied petroleum gas to engines have been continuously carried out.

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[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, and includes 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 in the fuel tank to the propulsion engine in a liquid phase and provided with a high-pressure pump, a reliquefaction device for liquefying the evaporated gas generated in a cargo tank for storing the liquefied gas, and a liquefied gas recovery line for recovering the liquid-phase liquefied gas discharged from the propulsion engine to the upstream of the high-pressure pump. The reliquefaction device transmits the liquefied evaporated gas to the fuel tank so as to be supplied to the propulsion engine by the high-pressure pump.

[0009] Specifically, the liquefied gas recovery line is provided with a pressure reducing valve for reducing the pressure of the surplus liquid-phase liquefied gas discharged from the propulsion engine and mixed with lubricating oil, and the surplus liquid-phase liquefied gas mixed with the lubricating oil used in the propulsion engine through the inside of the propulsion engine can be transmitted to the liquefied gas supply line upstream of the high-pressure pump so as to reflow 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 so as to flow into the high-pressure pump in a liquid phase.

[0011] Specifically, the reliquefaction device may include a compressor that multistage compresses the evaporation gas discharged from the cargo tank, a condenser that cools and liquefies the compressed evaporation gas with a refrigerant, and an intercooler that mutually heat-exchanges a part of the evaporation gas liquefied by the condenser and the remainder and transmits the evaporation gas generated by the heat exchange to the compressor.

[0012] Specifically, the reliquefaction device may further include a gas-liquid separator that gas-liquid separates the evaporation gas liquefied by the condenser, and can operate in at least any one of a reliquefaction mode in which the liquid phase separated by the gas-liquid separator is transmitted to the cargo tank via the intercooler and a fuel supply mode in which the liquid phase separated by the gas-liquid separator is transmitted to the fuel tank so as to be supplied to the propulsion engine.

[0013] Specifically, the reliquefaction device may include a compressor that multistage compresses the evaporation gas discharged from the cargo tank, a condenser that cools and liquefies the compressed evaporation gas, an evaporation gas heat exchanger that heat-exchanges the evaporation gas transmitted from the cargo tank to the compressor and the evaporation gas liquefied by the condenser.

[0014] Specifically, the reliquefaction device may further include a gas-liquid separator that gas-liquid separates the evaporation gas liquefied by the condenser, and can operate in at least any one of a reliquefaction mode in which the liquid phase separated by the gas-liquid separator is transmitted to the cargo tank via the evaporation gas heat exchanger and a fuel supply mode in which the liquid phase separated by the gas-liquid separator is transmitted to the fuel tank so as to be supplied to the propulsion engine.

[0015] A gas treatment system according to another aspect of the present invention is a system for treating liquefied gas which is a hydrocarbon or ammonia, the system supplying the liquefied gas stored in a cargo tank to the propulsion engine in a liquid phase through a liquefied gas supply line provided with a high-pressure pump, a reliquefaction device for liquefying the evaporation gas generated in the cargo tank and transmitting it to the high-pressure pump, and a liquefied gas recovery line for recovering the liquid-phase liquefied gas discharged from the propulsion engine upstream of the high-pressure pump. The reliquefaction device includes a condenser for cooling and liquefying the evaporation gas with a refrigerant, and a buffer for temporarily storing the evaporation gas liquefied in the condenser. A bypass line is provided so that at least a part of the evaporation gas bypasses the condenser and is supplied to the buffer in preparation for pressure fluctuations of the evaporation gas transmitted from the buffer to the high-pressure pump according to the temperature of the refrigerant.

[0016] Specifically, the liquefied gas recovery line is provided with a pressure reducing valve for reducing the pressure of the surplus liquid-phase liquefied gas discharged from the propulsion engine and mixed with lubricating oil, and the surplus liquid-phase liquefied gas mixed with the lubricating oil used in the propulsion engine through the inside of the propulsion engine can be transmitted to the liquefied gas supply line upstream of the high-pressure pump and re-introduced into the propulsion engine.

[0017] Specifically, the liquefied gas recovery line may be provided with a cooler for cooling the liquefied gas decompressed by the pressure reducing valve and flowing it into the high-pressure pump in a liquid phase.

[0018] Specifically, the buffer may be a gas-liquid separator for gas-liquid separating the evaporation gas liquefied in the condenser.

[0019] Specifically, the reliquefaction device can transmit the liquefied evaporation gas to the liquefied gas supply line between the cargo tank and the high-pressure pump.

[0020] Specifically, the re-liquefaction device may include a compressor that multi-stage compresses the evaporation gas discharged from the cargo tank, and an intercooler that mutually heat-exchanges a part of the evaporation gas liquefied in the condenser and the remainder, and transmits the evaporation gas generated by the heat exchange to the compressor.

[0021] Specifically, the re-liquefaction device can operate in at least any one of a re-liquefaction mode in which the liquid phase separated by the gas-liquid separator is transmitted to the cargo tank via the intercooler and a fuel supply mode in which the liquid phase separated by the gas-liquid separator is transmitted to the liquefied gas supply line upstream of the high-pressure pump and supplied to the propulsion engine.

[0022] The ship according to the present invention is a liquefied gas carrier having the gas treatment system.

Effect of the Invention

[0023] The gas treatment system according to the present invention and the ship including the same can move away from a conventional system that uses only diesel oil, enable the use of liquefied petroleum gas or ammonia as a propulsion fuel, reduce environmental pollution, and improve energy efficiency.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0025] The object, specific advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments related to the accompanying drawings. It should be noted that when assigning reference numerals to the components of each drawing in this specification, the same components should be assigned the same numbers as much as possible even if they are shown in other drawings. In the description of the present invention, when it is determined that the specific description of related known technologies makes the gist of the present invention unnecessarily unclear, the detailed description thereof will be omitted.

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification, the liquefied gas is a hydrocarbon, and may be LPG (such as propane, butane) or ammonia, etc., but is not limited thereto, and can include any substance having a boiling point lower than normal temperature and a calorific value.

[0027] Also, the liquefied gas / vapor gas in this specification is not necessarily limited to the liquid phase or the gas phase by name.

[0028] The present invention includes a ship equipped with a gas treatment system described below. At this time, the ship is a concept including all of a gas carrier, a merchant ship carrying non-gas cargo or people, an FSRU, an FPSO, a bunkering vessel, an offshore plant, etc., and the liquefied gas carrier is just an example.

[0029] Although not shown in the drawings of the present invention, a pressure sensor (PT), a temperature sensor (TT), etc. may be provided at appropriate positions without limitation, and the measured values by each sensor may be used in various ways without limitation for the operation of the configuration described below.

[0030] FIG. 1 is a conceptual diagram of a gas treatment system according to the first embodiment of the present invention.

[0031] Referring to FIG. 1, a gas treatment system 1 according to a first embodiment of the present invention includes a gas storage section, a fuel supply section 20, a reliquefaction section 30, and a fuel recovery section 40.

[0032] The gas storage section is configured to store liquefied gas and includes a cargo tank 10, a fuel tank 12, and the like.

[0033] The cargo tank 10 is a plurality of cargo tanks provided inside a ship that is a liquefied gas carrier. When the ship is of a type other than a gas carrier, it may be a tank or container separately added inside or outside the ship.

[0034] The cargo tank 10 is a tank that stores liquefied gas in a low-temperature liquid phase at atmospheric pressure, and various heat insulation structures may be added to the wall to prevent vaporization of the liquefied gas. Further, the cargo tank 10 may be a membrane type tank or an independent type tank, and its form and specifications are not limited.

[0035] A liquefied gas transfer line L21 may be provided from the cargo tank 10 to the fuel tank 12 described later, and the liquefied gas in the cargo tank 10 is transferred to the fuel tank 12 via the liquefied gas transfer line L21. The liquefied gas transferred to the fuel tank 12 is used as fuel for the propulsion engine E.

[0036] Incidentally, the propulsion engine E in this specification may be any configuration for propelling a ship, and can be interpreted as any configuration that consumes liquefied gas such as a turbine or a fuel cell (which is not an engine) and directly or indirectly generates propulsion force. Note that the propulsion engine E in this specification can be used as a term including all gas demand destinations such as an engine for propulsion, an engine for power generation, and a gas combustion device.

[0037] A transfer pump 11 is 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, or may be provided in a submerged type immersed in the liquefied gas.

[0038] A plurality of transfer pumps 11 may be provided in a part of the plurality of cargo tanks 10. The cargo tank 10 is basically for the purpose of cargo transportation, and at least two cargo pumps (such as cargo handling pumps, stripping pumps, etc., not shown) for unloading the cargo are provided for each cargo tank 10. However, at least one of the cargo tanks 10 may be provided with an additional transfer pump 11 in addition to the cargo pump in order to use the liquefied gas stored inside as fuel for a propulsion engine E (ME-LGI) or the like.

[0039] For example, when four cargo tanks 10 are arranged side by side in the longitudinal direction of the ship, the liquefied gas stored in the fourth cargo tank 10 close to the engine room accommodating the propulsion engine E can be transmitted to the fuel tank 12 and then used as fuel for the propulsion engine E. Therefore, the transfer pump 11 may be provided only in the fourth cargo tank 10.

[0040] Since the liquefied gas stored in the cargo tank 10 evaporates naturally due to external heat penetration, evaporation gas is generated in the cargo tank 10. The cargo tank 10 may be provided with an evaporation gas discharge line L10 for discharging the evaporation gas. The evaporation gas discharged from the cargo tank 10 may be liquefied and returned, or may be used as fuel for the propulsion engine E. This will be described in detail in the part about the re-liquefaction unit 30 below.

[0041] The cargo tanks 10 may be provided in plurality for storing at least two types of liquefied gases among liquefied gases (such as propane, butane, propylene, etc.) mainly composed of heavy hydrocarbons. That is, the cargo tank 10 may include a first cargo tank 10 for storing a first type of liquefied gas and a second cargo tank 10 for storing a second type of liquefied gas. For example, the first cargo tank 10 may store propane, and the second cargo tank 10 may store butane, etc.

[0042] The evaporated gas of the cargo tank 10 is liquefied through the condenser 32 of the re-liquefying unit 30 described later. When configured such that the liquefied evaporated gas returns to the cargo tank 10, the condenser 32 may be provided in at least the same number as the types of liquefied gases stored in the cargo tank 10 (and backup ones may also be provided).

[0043] That is, when the cargo tank 10 stores two types of liquefied gases, it is preferable to provide at least three condensers 32. Also, since the compressors 31 are provided in sets corresponding to the condensers 32, a plurality of compressors 31 may also be provided according to the number of condensers 32.

[0044] However, in this embodiment, by enabling the evaporated gas liquefied by the condenser 32 to be transmitted to the fuel tank 12 etc. without returning to the cargo tank 10, even if the cargo tank 10 is provided to store two or more types of liquefied gases, the number of installed (or operating) condensers 32 can be reduced to be less than or equal to the number of types of liquefied gases.

[0045] That is, the evaporated gas of the cargo tank 10 can be transmitted to the condenser 32 through the evaporated gas discharge line L10 and liquefied by refrigerant heat exchange in the condenser 32, and the liquefied evaporated gas can be transmitted to the high-pressure pump 22 described later through the fuel tank 12 and does not need to return to the cargo tank 10 (fuel supply mode).

[0046] The fuel tank 12 stores liquefied gas as fuel to supply the propulsion engine E. The fuel tank 12 may be of the same or different type as the independent type (SPB type, MOSS type) or membrane type cargo tank 10 that stores a large amount of liquefied gas at atmospheric pressure, or may be an independent type (Type C, pressure vessel type) that stores liquefied gas at high pressure.

[0047] At this time, the fuel tank 12 can store the liquefied gas at or above the threshold pressure (for example, around 18 bar) or below the threshold pressure (for example, around 8 bar), and a heat insulation structure may be provided on at least one side inside or outside the wall to prevent vaporization of the liquefied gas.

[0048] The fuel tank 12 may be mounted on the upper deck of the ship and is provided to be supported on the upper deck by a saddle. The fuel tank 12 does not interfere with the configuration (such as a manifold) for loading / unloading the liquefied gas of the cargo tank 10 on the upper deck and can be arranged at a position that does not obstruct the visibility during the navigation of the ship. For example, the fuel tank 12 may be provided on the port or starboard side of the bow of the upper deck. In this case, the fuel tank 12 may be referred to as a deck tank.

[0049] 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 a function of condensing the evaporation gas generated in the cargo tank 10 by using the liquefied gas stored inside.

[0050] That is, the fuel tank 12 may be used as a re-condenser 32 that receives and condenses the transmission of the evaporation gas generated in the cargo tank 10 by using the liquefied gas stored inside. For this purpose, an evaporation gas branch line (not shown) that branches toward the fuel tank 12 upstream of the condenser 32 may be provided in the evaporation gas discharge line L10 extended from the cargo tank 10.

[0051] 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 from the cargo tank 10 to the fuel tank 12 by the 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 in consideration of the operating state of the ship and the like.

[0052] Conversely, it is also possible to return the liquefied gas from the fuel tank 12 to the cargo tank 10, but this can be limited to the case where the liquefied gas stored in the fuel tank 12 has the same composition as the liquefied gas stored in the cargo tank 10.

[0053] The liquefied gas stored in the fuel tank 12 can be transferred from the fuel tank 12 to the propulsion engine E via the low-pressure pump 21 of the fuel supply unit 20 described later. A liquefied gas supply line L20 may 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.

[0054] Of course, the liquefied gas supply line L20 may be provided so that the liquefied gas is supplied to the propulsion engine E by bypassing the fuel tank 12 from the cargo tank 10. In this case, the liquefied gas supply line L20 can transfer the liquefied gas in the cargo tank 10 and / or the fuel tank 12 to the propulsion engine E.

[0055] The fuel supply unit 20 supplies liquefied gas to the propulsion engine E to operate the propulsion engine E. 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 figure) may be provided at an appropriate position.

[0056] The low-pressure pump 21 transfers the liquefied gas in the fuel tank 12 to the propulsion engine E. The low-pressure pump 21 may be provided inside or outside the fuel tank 12, or may be provided on the liquefied gas supply line L20 connected from the fuel tank 12 to the propulsion engine E.

[0057] The low-pressure pump 21 may 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 in accordance with the suction pressure (e.g., 20 bar) of the high-pressure pump 22 arranged downstream. That is, the low-pressure pump 21 raises the pressure of the liquefied gas by the differential pressure between the internal pressure of the fuel tank 12 and the suction pressure of the high-pressure pump 22.

[0058] However, when 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.

[0059] A liquefied gas return line (not shown) may be provided downstream of the low-pressure pump 21 in the liquefied gas supply line L20. When the flow rate transmitted to the propulsion engine E via the low-pressure pump 21 exceeds the required flow rate of the propulsion engine E, the liquefied gas return line can serve to recover the excess liquefied gas to the fuel tank 12.

[0060] Alternatively, the liquefied gas return line can embody the function of raising the internal pressure of the fuel tank 12 by re-inflowing the liquefied gas pressurized by the low-pressure pump 21 into the fuel tank 12 after being discharged from the fuel tank 12. Therefore, the fuel tank 12 can keep the internal pressure high and minimize the generation of evaporation gas in the fuel tank 12.

[0061] The high-pressure pump 22 pressurizes the liquefied gas in the fuel tank 12 according to the required pressure of the propulsion engine E and transmits it to the propulsion engine E. The pressure required by the propulsion engine E can be 20 to 50 bar, but it can vary depending on the specifications of the propulsion engine E.

[0062] The high-pressure pump 22 is provided on the liquefied gas supply line L20 extending from the fuel tank 12 to the propulsion engine E. The type of the high-pressure pump 22 is not particularly limited, and a plurality of high-pressure pumps 22 may be provided in parallel so that they can back up each other as shown in the drawing.

[0063] The high-pressure pump 22 may be provided upstream of the heat exchanger 23 as described later in the drawings, or may be provided downstream of the heat exchanger 23 differently from the drawings. In the latter case, the high-pressure pump 22 can pressurize the liquefied gas whose temperature has been adjusted by the heat exchanger 23 to the pressure required by the propulsion engine E.

[0064] In order to suppress the occurrence of cavitation in the pressurization process of the liquefied gas in the high-pressure pump 22, the liquefied gas may flow into the high-pressure pump 22 in the liquid phase. When the 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 content.

[0065] 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.

[0066] A filter (not shown in the figure) for filtering impurities may be provided downstream of the high-pressure pump 22, but the filter may also be further provided upstream of the low-pressure pump 21 as shown in the drawings.

[0067] Also, a fuel supply valve (not shown) may be provided downstream of the high-pressure pump 22 in the liquefied gas supply line L20. At this time, the fuel supply valve and the pressure reducing valve (not shown) provided in the liquefied gas recovery line L30 may be configured in one train and may be referred to as FVT (fuel valve train).

[0068] A liquefied gas circulation line L22 connected to the liquefied gas recovery line L30 of the fuel recovery unit 40 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 transmitted along the liquefied gas circulation line L22 to the liquefied gas recovery line L30 and circulated to the high-pressure pump 22 again.

[0069] The high-pressure pump 22 has a minimum required flow rate set for reasons such as operational stability. This is referred to as the minimum flow, and during operation, it is preferable for liquefied gas satisfying the minimum required flow rate to flow into the high-pressure pump 22.

[0070] However, the consumption rate at the propulsion engine E downstream of the high-pressure pump 22 may not satisfy the minimum required flow rate of the high-pressure pump 22. For example, this case corresponds to when the propulsion engine E operates at a low load or stops during the operation of the high-pressure pump 22.

[0071] At this time, in this embodiment, for the stable operation of the high-pressure pump 22, even if the required flow rate of the propulsion engine E does not satisfy the minimum required flow rate of the high-pressure pump 22, in order to allow liquefied gas with a flow rate greater than or equal to the minimum required flow rate to flow into the high-pressure pump 22, the liquefied gas can be circulated.

[0072] 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, 20 of 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 back to the high-pressure pump 22.

[0073] Therefore, the liquefied gas circulation line L22 can ensure the minimum required flow rate of the high-pressure pump 22 by circulating a flow rate greater than or equal to the flow rate obtained by subtracting the required flow rate of the propulsion engine E from the minimum required flow rate of the high-pressure pump 22 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.

[0074] The heat exchanger 23 is provided downstream of the low-pressure pump 21 to change the temperature of the liquefied gas. Since the heat exchanger 23 can increase or decrease the temperature of the liquefied gas, it may also be referred to as a fuel conditioner.

[0075] For example, at the initial operation of this embodiment, since the flow rate of the high-temperature liquefied gas recovered from the propulsion engine E is large, the heat exchanger 23 can lower the temperature of the liquefied gas, and when entering stable operation, the heat exchanger 23 can increase the temperature of the liquefied gas.

[0076] The heat exchanger 23 may be provided downstream of the high-pressure pump 22 as shown in the drawing. However, different from 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 adjust the temperature of the liquefied gas below the boiling point of the liquefied gas so that the vapor-phase liquefied gas does not flow into the high-pressure pump 22.

[0077] The heat exchanger 23 can implement heat exchange with the liquefied gas using various heat exchange media. For example, the heat exchange media may be seawater, fresh water, glycol water, exhaust gas, etc., but is not limited thereto.

[0078] The reliquefaction unit 30 liquefies the evaporation gas generated in the cargo tank 10. The reliquefaction unit 30 may consist of modules in which a plurality of components are arranged on one skid to form a reliquefaction device, and the reliquefaction unit 30 may include a plurality of reliquefaction devices. However, for the sake of convenience, only one reliquefaction device is shown in the drawing.

[0079] Such a reliquefaction 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 in order on the evaporation gas discharge line L10, and the intercooler 34 may be provided on the evaporation gas return line L11 connected from the gas-liquid separator 33 to the cargo tank 10.

[0080] The compressor 31 compresses the evaporation gas discharged from the cargo tank 10. The compressor 31 can raise the boiling point of the evaporation gas by compression, thereby increasing the liquefaction efficiency in the condenser 32 described below.

[0081] The compressor 31 may be composed of multiple stages, may be composed of three stages as shown in the drawing, or may be provided in other various numbers of stages. Also, the compressor 31 may be provided in parallel on the evaporation gas discharge line L10 so as to be able to back up each other.

[0082] The compressor 31 can transfer the compressed evaporation gas to the condenser 32 so that it is liquefied, or to the fuel tank 12 filled with an appropriate amount of liquefied gas. In the former case, the evaporation gas liquefied by the condenser 32 is supplied to the fuel tank 12. In the latter case, the high-pressure evaporation gas can be directly injected into the fuel tank 12 and cooled and liquefied by the liquefied gas in the fuel tank 12.

[0083] A drum (not shown) may be provided upstream of the compressor 31. The drum is a gas-liquid separation structure for filtering droplets from the evaporation gas discharged from the cargo tank 10, and the droplets may be provided to return to the cargo tank 10.

[0084] The drum can protect the compressor 31 by preventing droplets from flowing into the compressor 31, and the drum can be omitted depending on the type of the compressor 31.

[0085] The condenser 32 liquefies the evaporation gas generated in the cargo tank 10. A refrigerant can be used for liquefying the evaporation gas, and the refrigerant may be glycol water, nitrogen, seawater, etc. In the following description of this specification, it will be assumed that the refrigerant of the condenser 32 is seawater for explanation.

[0086] The condenser 32 may have a two-stream structure including an evaporation gas stream into which the evaporation gas compressed by the compressor 31 flows and a refrigerant stream through which the refrigerant for heat exchange with the evaporation gas flows.

[0087] The type of such a condenser 32 is not limited to Shell&Tube, PCHE, etc., and a bath type in which the evaporation gas passes through the housing storing the refrigerant for heat exchange is also possible.

[0088] The cargo tank 10 may be provided in a plurality for storing at least two types of liquefied gases as described above, and the condenser 32 may be provided to liquefy all different types of evaporation gases.

[0089] When a plurality of cargo tanks 10 for storing different types of liquefied gas are provided, a plurality of condensers 32 may be provided corresponding to the types of liquefied gas. Alternatively, as described above, in this embodiment, by integrating and transmitting different types of evaporation gas to one condenser 32, the number of installed (or operating) condensers 32 can be reduced.

[0090] This is because the reliquefaction device of this embodiment can operate in a fuel supply mode of transmitting the liquefied evaporation gas to the fuel tank 12 rather than the cargo tank 10 and consuming it in the propulsion engine E.

[0091] Of course, if no compositional contamination occurs in the cargo tank 10 even when the evaporation gas liquefied by the condenser 32 returns to the cargo tank 10, the reliquefaction device can also operate in a reliquefaction mode of transmitting the liquefied evaporation gas to the cargo tank 10.

[0092] The gas-liquid separator 33 temporarily stores the evaporation gas liquefied by the condenser 32. The gas-liquid separator 33 may be in the form of a container or a form in which a pipe is partially expanded so as to have a buffer function.

[0093] After separating the liquefied evaporation gas into a gas phase and a liquid phase, the gas-liquid separator 33 can transmit the liquid phase to the cargo tank 10, the fuel tank 12, etc. The gas-liquid separator 33 can transmit only the liquid phase to the cargo tank 10, etc., and the gas phase can be accommodated inside, and the vaporization of the evaporation gas can be prevented by maintaining a certain level of internal pressure.

[0094] As described above, the reliquefaction device can operate in a fuel supply mode of transmitting the liquefied evaporation gas to the fuel tank 12 rather than the cargo tank 10 in order to prevent the composition mixing of the liquefied gas (or to supply the evaporation gas to the propulsion engine E). Therefore, an evaporation gas transmission line L12 through which the gas-liquid separator 33 transmits the liquid phase to the fuel tank 12 may be provided.

[0095] Alternatively, in order for the reliquefaction device to operate in the reliquefaction mode, a vapor 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 vapor return line L11.

[0096] Therefore, the reliquefaction device can operate in at least one of a reliquefaction mode in which the liquid phase separated by the gas-liquid separator 33 is transmitted to the cargo tank 10 via the intercooler 34, and / or a fuel supply mode in which the liquid phase separated by the gas-liquid separator 33 is transmitted to the fuel tank 12 and supplied to the propulsion engine E.

[0097] That is, the reliquefaction device can also operate in a mode in which the reliquefaction mode and the fuel supply mode are combined. In the case of the combined mode, a part of the liquid phase separated by the gas-liquid separator 33 is transmitted to the cargo tank 10, and the rest is transmitted to the fuel tank 12, and the flow rate at which the liquid phase is branched to the fuel tank 12 may be controlled according to the load of the propulsion engine E.

[0098] The intercooler 34 causes a part of the evaporated gas liquefied by the condenser 32 to exchange heat with the rest, and transmits the gaseous evaporated gas generated by the heat exchange among the evaporated gas flowing in from the condenser 32 to the compressor 31.

[0099] The intercooler 34 is used to cool the evaporated gas at an intermediate stage of the multi-stage compressor 31. When the evaporated gas is compressed by the compressor 31, its temperature rises due to the compression heat. In this case, there is a problem that the load of the compressor 31 increases. Therefore, in this embodiment, the intercooler 34 can be used for intermediate cooling.

[0100] Specifically, the intercooler 34 is provided in the form of a container that stores a part of the evaporated gas liquefied by the condenser 32, and the evaporated gas stored inside is used as a refrigerant to cool the rest of the evaporated gas liquefied by the condenser 32 (the flow rate transmitted to the cargo tank 10).

[0101] For this purpose, the evaporation gas return line L11 branches upstream of the intercooler 34. One side transmits the evaporation gas into the intercooler 34, and the other side is connected to the cargo tank 10 via the inside of the intercooler 34 to exchange heat with the evaporation gas stored in the intercooler 34.

[0102] That is, the intercooler 34 can sufficiently liquefy the evaporation gas transmitted from the condenser 32 to the cargo tank 10 by exchanging heat between the evaporation gas transmitted from the condenser 32 and stored inside and the evaporation gas transmitted to the cargo tank 10.

[0103] At this time, for improving the efficiency of heat exchange, the part passing through the inside of the intercooler 34 in the evaporation gas return line L11 may be provided in a coil shape. Also, for improving the cooling efficiency, a pressure reducing valve (not shown in the figure) may be provided in the part of the evaporation gas return line L11 that transmits the evaporation gas into the intercooler 34.

[0104] In addition, the intercooler 34 transmits the gas phase of the evaporation gas stored inside to the intermediate stage of the compressor 31. The gas phase evaporation gas transmitted from the intercooler 34 to the intermediate stage of the compressor 31 is in an extremely low temperature state close to the boiling point. Therefore, the evaporation gas at the intermediate stage of the compressor 31 can be cooled by being mixed with the gas phase evaporation gas transmitted from the intercooler 34.

[0105] The intercooler 34 may be respectively assigned to the intermediate stages of the multi-stage compressor 31. However, in this case, since the evaporation gas circulates through the intercooler 34, the amount of evaporation gas flowing from the cargo tank 10 into the reliquefaction device may be restricted depending on the amount of evaporation gas transmitted from the intercooler 34 to the intermediate stage of the compressor 31.

[0106] That is, the re-liquefaction device is designed to have a re-liquefaction capacity that excludes the amount of evaporated gas transmitted to the intermediate stage of the compressor 31 by the intercooler 34, compared to the inflow allowance of the first stage of the compressor 31. For example, if the inflow allowance of the first stage of the compressor 31 is 800, and 200 of evaporated gas circulates through the intermediate stages (between the first and second stages and between the second and third stages) of the compressor 31 by the intercooler 34 respectively, the amount of evaporated gas that the re-liquefaction device can finally receive from the cargo tank 10 will decrease to 400.

[0107] To improve this, in this embodiment, the intercooler 34 is assigned to only a part of the intermediate stage of the compressor 31, and an aftercooler 35 other than the intercooler 34 is provided for the remaining part of the intermediate stage of the compressor 31, so that the capacity of the re-liquefaction device can be increased.

[0108] The intercooler 34 may be replaced by a separator. Similar to the gas-liquid separator 33 described above, the separator can separate the evaporated gas liquefied by the condenser 32 into gas and liquid phases. The liquid phase can be transmitted to the cargo tank 10, and the gas phase can be transmitted to the intermediate stage of the compressor 31. In this case, since the separator only separates the evaporated gas into gas and liquid phases without performing heat exchange between the evaporated gases, the internal coiled evaporated gas return line L11 may be omitted.

[0109] The aftercooler 35 is provided in a part of the intermediate stage of the compressor 31 and can cool the evaporated gas using a separate refrigerant. From the perspective of the condenser 32, the aftercooler 35 can embody the function of a pre-cooler.

[0110] The aftercooler 35 can use a refrigerant such as seawater similar to the condenser 32, and various other refrigerants can also be utilized. 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.

[0111] Describing with reference to the drawings, in this embodiment, an intercooler 34 can be connected between the first stage and the second stage of the compressor 31 to circulate the vapor-phase evaporation gas, and an aftercooler 35 can be provided between the second stage and the third stage of the compressor 31.

[0112] At this time, if the inflow allowable capacity of the first stage of the compressor 31 is 800 and the circulation of the intercooler 34 is performed for 200 minutes, in this embodiment, the transmission of 600 evaporation gas amounts from the cargo tank 10 to the reliquefaction device is allowed.

[0113] That is, in this embodiment, compared with the case where the reliquefaction device connects all the intercoolers 34 to each of the intermediate stages of the compressor 31, at least one of the intercoolers 34 can be replaced with an aftercooler 35 to increase the reliquefaction capacity.

[0114] Such a reliquefaction unit 30 of this embodiment can operate in two modes. For example, the reliquefaction unit 30 can operate in a reliquefaction mode in which the evaporation gas liquefied by the condenser 32 is transmitted to the cargo tank 10 via the intercooler 34, and a fuel supply mode in which the evaporation gas is transmitted to the propulsion engine E side upstream or downstream of the condenser 32.

[0115] Specifically, in the reliquefaction mode, the multi-stage compressed evaporation gas is liquefied through the condenser 32 and then transmitted to the intercooler 34 through the gas-liquid separator 33. At this time, the evaporation gas is branched upstream of the intercooler 34, a part of the evaporation gas is filled inside the intercooler 34, and the remaining evaporation gas passes through the inside of the intercooler 34 so as to only perform heat exchange without being mixed with the evaporation gas filled inside the intercooler 34. The evaporation gas passing through the intercooler 34 may be cooled or subcooled so as to stably maintain the liquid phase and then returned to the cargo tank 10.

[0116] On the one hand, in the fuel supply mode, the multi-stage compressed evaporated gas may be transmitted to the fuel tank 12 upstream of the condenser 32, or the multi-stage compressed and condensed evaporated gas may be transmitted to the fuel tank 12 and then transmitted to the propulsion engine E by the high-pressure pump 22.

[0117] Preferably, the fuel supply mode does not return the liquefied evaporated gas to the cargo tank 10, or it can operate when the load on the propulsion engine E is high and the liquefied gas stored in the fuel tank 12 alone cannot meet the required flow rate of the propulsion engine E.

[0118] For example, when propane and butane are stored in the cargo tank 10, if a problem occurs in the reliquefaction device for processing butane and its operation stops, another reliquefaction device for processing propane can be used to liquefy butane. At this time, since the propane remaining in the reliquefaction device for processing propane may be mixed into the butane, a fuel supply mode in which the liquefied butane is transmitted to the fuel tank 12 instead of being transmitted to the cargo tank 10 may be executed.

[0119] In addition, in various situations where it is more preferable to transmit to the fuel tank 12 rather than to the cargo tank 10, it can operate in the fuel supply mode instead of the reliquefaction mode. Also, as described above, it goes without saying that a combined mode of operation combining the reliquefaction mode and the fuel supply mode is also possible.

[0120] The fuel recovery unit 40 recovers the liquefied gas in the liquid phase discharged from the propulsion engine E. The fuel recovery unit 40 can recover the liquefied gas in the liquid phase upstream of the high-pressure pump 22. 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.

[0121] Different from commercial engines (such as ME-GI, XDF) that receive and consume LNG in the gas phase, the propulsion engine E (such as ME-LGI) in the present invention has a structure that receives and consumes LPG and the like in the liquid phase and discharges the surplus liquid-phase fuel.

[0122] This is because, unlike in the case of the gas phase, in the case of the liquid phase, it is not easy to finely control the fuel supply amount, so that an excess amount of fuel is generated when the propulsion engine E is supplied with a sufficient amount of liquid-phase fuel.

[0123] However, the liquefied gas recovered from the propulsion engine E is not the liquefied gas before flowing into the propulsion engine E, but the liquefied gas that has passed through the inside of the propulsion engine E, and while having a temperature / pressure corresponding to the required pressure of the propulsion engine E (for example, around 45 bar, 50 °C or higher), lubricating oil used in the propulsion engine E may be mixed into the liquefied gas.

[0124] That is, since the excess liquefied gas recovered from the propulsion engine E is mixed with lubricating oil, it is preferable not to transfer the recovered liquefied gas to the cargo tank 10 in order to prevent contamination of the cargo.

[0125] Therefore, the liquefied gas recovery line L30 connected to the propulsion engine E so as to recover the excess liquefied gas can transfer the excess liquefied gas returned from the propulsion engine E to the high-pressure pump 22 rather than the cargo tank 10 and re-introduce it into the propulsion engine E.

[0126] That is, the liquefied gas recovery line L30 can prevent the liquefied gas in the cargo tank 10 from being contaminated by lubricating oil by transferring the excess liquid-phase liquefied gas mixed with the lubricating oil used in the propulsion engine E through the inside of the propulsion engine E to the liquefied gas supply line L20 upstream of the high-pressure pump 22 and re-introducing it into the propulsion engine E.

[0127] Such a fuel recovery unit 40 includes a pressure reducing valve and a cooler 41 provided in the liquefied gas recovery line L30, and may further include a collection tank 42 and a knock-out drum 43.

[0128] The pressure reducing valve reduces the pressure of the surplus liquid-phase liquefied gas discharged from the propulsion engine E and mixed with lubricating oil. The pressure reducing valve may be a Joule-Thomson valve and may be provided to constitute a fuel supply train FVT together with the fuel supply valve.

[0129] Such a pressure reducing valve can reduce the pressure of the liquefied gas at a high pressure (around about 30 to 50 bar) recovered from the propulsion engine E and adjust it to the suction pressure of the high-pressure pump 22.

[0130] The cooler 41 cools the liquefied gas whose pressure has been reduced by the pressure reducing valve in the liquefied gas recovery line L30 so that it flows into the high-pressure pump 22 in the liquid phase. The cooler 41 can utilize various refrigerants without limitation and can cool the liquefied gas below the boiling point of the pressure-reduced liquefied gas. For example, the cooler 41 can use seawater as a refrigerant, and at this time, the heat exchanger 23 and the cooler 41 may be integrally connected by one refrigerant supply unit.

[0131] Since the cooling by the cooler 41 can be performed in consideration of the mixing with the liquefied gas transmitted from the fuel tank 12 to the high-pressure pump 22, the cooler 41 can also control to cool the liquefied gas to a temperature slightly higher than the boiling point of the pressure-reduced liquefied gas.

[0132] The liquefied gas in the liquid phase (or in a state close to the liquid phase) cooled by the cooler 41 is mixed upstream of the high-pressure pump 22 in the liquefied gas supply line L20 via 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.

[0133] The above-described liquefied gas circulation line L22 may be branched from the liquefied gas supply line L20 downstream of the high-pressure pump 22 and connected upstream of the cooler 41 in 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.

[0134] This is because when the liquefied gas is pumped and heated by the operation of the high-pressure pump 22, if the heated liquefied gas is continuously circulated, the temperature of the high-pressure pump 22 itself may become unnecessarily high, and this is to suppress that. That is, in this embodiment, by using the cooler 41, when the liquefied gas circulates through the liquefied gas circulation line L22, the degree of heat generation of the high-pressure pump 22 can be limited within a preset value.

[0135] Therefore, the high-pressure pump 22 can continuously pump the liquefied gas above the minimum required flow rate, and the surplus liquefied gas recovered by the liquefied gas circulation line L22 circulates to the high-pressure pump 22 via the cooler 41, so overheating of the high-pressure pump 22 can be prevented.

[0136] The collection tank 42 collects a part of the liquefied gas returning from the propulsion engine E. The collection tank 42 may be provided branched from the liquefied gas recovery line L30 connected from the propulsion engine E to the liquefied gas supply line L20 upstream of the high-pressure pump 22, or a liquefied gas collection line L31 may extend from the liquefied gas recovery line L30 to the collection tank 42.

[0137] At this time, the liquefied gas collection line L31 extends from between the pressure reducing valve of the liquefied gas recovery line L30 and the cooler 41 and is connected to the collection tank 42, and can further merge from the collection tank 42 into the liquefied gas recovery line L30 upstream of the cooler 41. That is, the liquefied gas collection line L31 is provided partially in parallel with the liquefied gas recovery line L30 and may be provided so that the collection tank 42 is provided.

[0138] The collection tank 42 separates the recovered liquefied gas into gas and liquid. Since cavitation problems may occur when the gaseous liquefied gas flows into the high-pressure pump 22, the present invention can separate the liquefied gas flowing along the liquefied gas recovery line L30 into gas and liquid via the collection tank 42 as needed, and block the inflow of the gaseous liquefied gas into the high-pressure pump 22.

[0139] That is, the collection tank 42 can ensure the stable operation of the high-pressure pump 22 by collecting the liquefied gas in the liquefied gas recovery line L30 and transmitting only the liquefied gas in the liquid phase to the high-pressure pump 22.

[0140] The knock-out drum 43 can collect the liquefied gas recovered from the propulsion engine E and receive transmission from the collection tank 42, and filter the impurities (such as lubricating oil) contained in the liquefied gas. A liquefied gas treatment line L32 may be connected from the collection tank 42 to the knock-out drum 43. In addition to the liquefied gas in the gas phase separated by the collection tank 42, the liquefied gas treatment line L32 can transmit the liquefied gas in the liquid phase transmitted from the collection tank 42 to the liquefied gas recovery line L30 to the knock-out drum 43.

[0141] The knock-out drum 43 separates the lubricating oil from the liquefied gas flowing into it. Specifically, the knock-out drum 43 discharges the liquefied gas in the gas phase and discharges the lubricating oil in the liquid phase. That is, the knock-out drum 43 implements a gas-liquid separation function similar to that of the collection tank 42.

[0142] However, in order to promote the vaporization of the liquefied gas, the knock-out drum 43 may use a heating part such as tracing. Tracing may use a medium such as steam or seawater as a heat source, or may be configured to heat using electricity.

[0143] The knock-out drum 43 heats the liquefied gas mixed with lubricating oil in the heating part, discharges the liquefied gas to a vent mast (not shown), etc., and the lubricating oil can be drained at the lower part and processed (recycled).

[0144] Incidentally, the vent mast (not shown) discharges the substances to be vented externally 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 it can protect the crew on the deck.

[0145] Needless to say, the vent mast may be connected from the collection tank 42 or the knockout drum 43, and can also be connected to the evaporation gas discharge line L10, the liquefied gas supply line L20, the fuel tank 12, etc. Thereby, the vent mast realizes external discharge in normal operation or in an emergency such as the shutdown of the propulsion engine E to protect the system.

[0146] Also, the vent mast can discharge purge gas to the outside during purging of the evaporation gas discharge line L10, the liquefied gas supply line L20, etc. At this time, the purge gas may be nitrogen gas or inert gas, etc.

[0147] In this way, in this embodiment, after the evaporation gas generated in the cargo tank 10 is re-liquefied, it is transmitted to the fuel tank 12 and supplied to the propulsion engine E, so that different types of liquefied gas are re-liquefied and then returned to the cargo tank 10. The problem of contamination of the composition of the liquefied gas can be solved, and the number of installed condensers 32 and the number of operating units can be reduced.

[0148] FIG. 2 is a conceptual diagram of a gas treatment system according to a second embodiment of the present invention.

[0149] Hereinafter, the differences between this embodiment and the above-described embodiment will be mainly described, and the parts where the description is omitted will be replaced with the above-described content. This is the same in the embodiments described later.

[0150] Referring to FIG. 2, in the gas treatment system 1 according to the second embodiment of the present invention, the re-liquefaction unit 30 liquefies the evaporation gas and transmits it to the high-pressure pump 22. Specifically, the re-liquefaction device can transmit the liquefied evaporation gas to the fuel tank 12 in the same manner as in the above-described embodiment, or transmit it to the liquefied gas supply line L20 between the fuel tank 12 and the high-pressure pump 22.

[0151] Therefore, in addition to the evaporation gas return line L11 and the evaporation gas transfer line L12 as the lines for transferring the liquid phase separated by the gas-liquid separator 33, an evaporation gas supply line L13 may be provided. One end of the evaporation gas supply line L13 may extend from the gas-liquid separator 33 or the evaporation gas transfer line L12, and the other end may be connected between the high-pressure pump 22 and the low-pressure pump 21 of the liquefied gas supply line L20.

[0152] The point where the evaporation gas transfer line L12 is connected to the liquefied gas supply line L20 may be upstream or at the same point as the point where the liquefied gas recovery line L30 is connected to the liquefied gas supply line L20. Therefore, in addition to the liquefied gas supplied from the low-pressure pump 21 and the surplus liquefied gas recovered via the liquefied gas recovery line L30, the high-pressure pump 22 can pressurize the evaporation gas of the liquid phase transmitted from the reliquefaction device and supply it to the propulsion engine E.

[0153] When the evaporation gas liquefied by the condenser 32 bypasses the fuel tank 12 via the evaporation gas supply line L13 and merges with the liquefied gas recovered by the liquefied gas recovery line L30 and then is supplied to the high-pressure pump 22, the high-pressure pump 22 can still prevent the inflow of gas.

[0154] Specifically, in this embodiment, the inflow pressure of the high-pressure pump 22 and the evaporation 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, and the boiling points of the liquefied gas flowing through the liquefied gas supply line L20 upstream of the high-pressure pump 22 and the evaporation gas flowing through the evaporation gas supply line L13 can be controlled to be the same. That is, no separate pressurization / compression means is provided on the evaporation gas supply line L13 between the gas-liquid separator 33 and the high-pressure pump 22.

[0155] 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 liquefied gas in the liquid phase flowing through the liquefied gas recovery line L30 is also equal to the boiling point of the evaporation gas on the evaporation gas supply line L13.

[0156] At this time, the condenser 32 of the reliquefaction device and the cooler 41 on the liquefied gas recovery line L30 may use the same refrigerant. That is, the same refrigerant having the same conditions (temperature) is supplied to the condenser 32 and the cooler 41, and the evaporation gas / liquid-phase liquefied gas is cooled to substantially the same temperature.

[0157] Therefore, in this embodiment, in order for the cooler 41 of the fuel recovery unit 40 to prevent vaporization at the inflow end of the high-pressure pump 22, the liquefied gas in the liquid phase having the first pressure is cooled by the first refrigerant, and the condenser 32 of the reliquefaction unit 30 also cools the evaporation gas having the first pressure with the first refrigerant. Therefore, the cooler 41 and the condenser 32 may be controlled in mutual cooperation so that gas does not flow into the high-pressure pump 22.

[0158] That is, in this embodiment, even if the inflow pressure of the high-pressure pump 22 is low, since the condenser 32 uses the same refrigerant as the cooler 41 based on the same pressure as the liquefied gas in the liquid phase recovered in the fuel recovery unit 40 to condense the evaporation gas, the reliquefaction device can bypass the fuel tank 12 and directly transmit the evaporation gas to the high-pressure pump 22 to ensure the operating stability of the high-pressure pump 22.

[0159] Therefore, when the reliquefaction device of this embodiment operates in the fuel supply mode, in addition to transmitting the liquid phase separated by the gas-liquid separator 33 to the fuel tank 12, it can be transmitted to the liquefied gas supply line L20 upstream of the high-pressure pump 22 and supplied to the propulsion engine E. The flow control to the evaporation gas transmission line L12 or the evaporation gas supply line L13 may be controlled according to various variables such as the amount of evaporation gas discharged from the cargo tank 10, the load of the propulsion engine E, and the internal pressure of the fuel tank 12.

[0160] In addition, the reliquefaction device of this embodiment includes a bypass line L14. The bypass line L14 allows at least a part of the evaporation gas to bypass the condenser 32 and be supplied to the gas-liquid separator 33, and a bypass valve 36 for flow adjustment may be provided in the bypass line L14.

[0161] When the temperature of the refrigerant used by the condenser 32 is low, the evaporated gas may be subcooled by the refrigerant. When the subcooled evaporated gas in the liquid phase flows into the gas-liquid separator 33 downstream of the condenser 32, it may cause a drop in the internal pressure of the gas-liquid separator 33.

[0162] That is, the refrigerant temperature in the condenser 32 can determine the degree of cooling of the evaporated gas, which determines the internal pressure in the gas-liquid separator 33. The internal pressure of the gas-liquid separator 33 can be the pressure of the evaporated gas transmitted to the high-pressure pump 22 via 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 will be low, and there is a risk of vaporization in the high-pressure pump 22.

[0163] Therefore, the refrigerant temperature in the condenser 32 may lead to a vaporization problem at the inlet end of the high-pressure pump 22. In this embodiment, control can be implemented to increase the pressure of the gas-liquid separator 33 according to the refrigerant temperature.

[0164] For this purpose, the bypass line L14 can be provided to cope with the pressure fluctuation of the evaporated gas transmitted from the gas-liquid separator 33 to the high-pressure pump 22 according to the temperature of the refrigerant. By opening the bypass valve 36, at least a part of the evaporated gas can bypass the condenser 32 and be supplied to the gas-liquid separator 33.

[0165] When the high-temperature vapor-phase evaporated gas that bypasses the condenser 32 flows into the gas-liquid separator 33, the internal pressure of the gas-liquid separator 33 increases. Therefore, the pressure of the evaporated gas in the liquid phase transmitted from the gas-liquid separator 33 to the liquefied gas supply line L20 via the evaporated gas supply line L13 increases, and the boiling point becomes higher.

[0166] Therefore, in this embodiment, by controlling the bypass of the condenser 32 with the refrigerant temperature as a variable, it is possible to prevent the evaporated gas in the liquid phase transmitted from the reliquefaction device to the high-pressure pump 22 from vaporizing again, thereby preventing the cavitation phenomenon in the high-pressure pump 22.

[0167] Further, by controlling the internal pressure of the gas-liquid separator 33 to correspond to the pressure of the liquid-phase liquefied gas recovered in the liquefied gas recovery line L30, it is possible to ensure that only the liquid phase stably flows into the inlet end of the high-pressure pump 22 while the condenser 32 and the cooler 41 operate using the same refrigerant as described above.

[0168] In this way, if the temperature of the refrigerant used in the condenser 32 is low, the pressure of the evaporated gas in the liquid phase transmitted from the reliquefaction device to the high-pressure pump 22 is low, so there is a risk of vaporization and inflow into the high-pressure pump 22. However, in this embodiment, control is applied such that some of the evaporated gas bypasses the condenser 32 according to the temperature of the refrigerant, and the above problems can be effectively solved.

[0169] FIG. 3 is a conceptual diagram of a gas treatment system according to a third embodiment of the present invention.

[0170] Referring to FIG. 3, in the gas treatment system 1 according to the third embodiment of the present invention, the fuel tank 12 may be omitted compared to the above-described second embodiment, and the liquefied gas transmission line L21, the evaporated gas transmission line L12, etc. may also be omitted.

[0171] In this case, the liquefied gas supply line L20 may 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. may be provided on the liquefied gas supply line L20.

[0172] The low-pressure pump 21 may be arranged 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 provided to correspond to the inlet pressure of the high-pressure pump 22.

[0173] Also, in this embodiment, the reliquefaction device can transmit the liquefied evaporation 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 transmit the liquid phase separated by the gas-liquid separator 33 to the liquefied gas supply line L20 upstream of the high-pressure pump 22 so as to be supplied to the propulsion engine E.

[0174] Note that the reliquefaction device liquefies the evaporation gas and transmits it to the high-pressure pump 22 as in the above-described embodiment. However, depending on the temperature of the refrigerant, a part of the evaporation gas can bypass the condenser 32 and be transmitted to the liquefied gas supply line L20 upstream of the high-pressure pump 22 via the gas-liquid separator 33.

[0175] FIG. 4 is a conceptual diagram of a gas treatment system according to a fourth embodiment of the present invention.

[0176] Referring to FIG. 4, in the gas treatment system 1 according to the fourth embodiment of the present invention, the evaporation gas supply line L13 is omitted as compared with the above-described second embodiment, and the liquefied gas recovery point is set to the fuel tank 12.

[0177] The reliquefaction device in this embodiment can transmit the liquefied evaporation gas to the fuel tank 12. This can be done by the evaporation gas transmission line L12 as described above. That is, in the fuel supply mode, the reliquefaction device can transmit the liquid phase separated by the gas-liquid separator 33 to the fuel tank 12 so as to be supplied to the propulsion engine E.

[0178] However, in this embodiment, the liquefied gas recovery line L30 of the fuel recovery unit 40 may extend from the propulsion engine E and be connected to the inside of the fuel tank 12. Therefore, the liquefied gas recovery line L30 can transmit the surplus liquefied gas of the liquid phase mixed with the lubricating oil used in the propulsion engine E to the fuel tank 12. At this time, the liquefied gas of the liquid phase flowing into the fuel tank 12 can flow back into the propulsion engine E via the low-pressure pump 21 and the high-pressure pump 22.

[0179] The fuel tank 12 of this embodiment is configured such that surplus liquefied gas can be directly recovered inside, and the internal pressure may be set higher compared to the above-described second embodiment. That is, the internal pressure of the fuel tank 12 may be adjusted to a pressure at which the recovered liquefied gas does not vaporize. 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.

[0180] Similar to the second and third embodiments, in this embodiment as well, the flow of the vaporized gas in the liquid phase can be controlled according to the temperature of the refrigerant used in the condenser 32. Specifically, the reliquefaction device in this embodiment can be configured such that at least a part of the vaporized gas bypasses the condenser 32 and is supplied to the fuel tank 12 in preparation for pressure fluctuations of the vaporized gas transmitted to the fuel tank 12 according to the temperature of the refrigerant.

[0181] In this embodiment, the vaporized gas in the liquid phase may be transmitted to the high-pressure pump 22 via the fuel tank 12, and a low-pressure pump 21 may be provided between the fuel tank 12 and the high-pressure pump 22. Therefore, 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.

[0182] Therefore, the reliquefaction device of this embodiment can be configured such that a part of the vaporized gas bypasses the condenser 32 and is supplied to the fuel tank 12 via the gas-liquid separator 33 in preparation for pressure fluctuations of the vaporized gas transmitted from the gas-liquid separator 33 to the fuel tank 12 according to the temperature of the refrigerant. That is, in this embodiment, by adjusting the bypass of the vaporized gas, the internal pressure of the gas-liquid separator 33 and the internal pressure of the fuel tank 12 can be adjusted at once.

[0183] Alternatively, in the case of this embodiment, since the vaporized gas in the liquid phase liquefied by the condenser 32 is transmitted to the high-pressure pump 22 via the fuel tank 12, the fuel tank 12 can embody a gas-liquid separation function, and the gas-liquid separator 33 may be omitted in the reliquefaction device.

[0184] Figure 5 is a conceptual diagram of a gas treatment system according to a fifth embodiment of the present invention.

[0185] Referring to Figure 5, the gas treatment system 1 according to the fifth embodiment of the present invention may be provided such that the connection point of the evaporation gas supply line L13 is different compared to the second embodiment.

[0186] The evaporation gas supply line L13 of this embodiment can transmit the evaporation 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 evaporation gas supply line L13 may be connected between the condenser 32 and the gas-liquid separator 33 of the re-liquefaction device, and the other end may be connected upstream of the high-pressure pump 22 of the liquefied gas supply line L20.

[0187] Such an evaporation gas supply line L13 is provided to prepare for internal pressure fluctuations of the gas-liquid separator 33 according to the temperature of the refrigerant. Specifically, when the temperature of the refrigerant is low, lower than the reference value, the evaporation gas supply line L13 can directly communicate the upstream of the high-pressure pump 22 and the upstream of the gas-liquid separator 33 in order to prevent the pressure from becoming insufficient when the evaporation gas is supercooled in the condenser 32 and flows into the high-pressure pump 22 through the gas-liquid separator 33.

[0188] In this case, since 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 order downstream along the flow of the evaporation gas, the pressure at the inlet end of the high-pressure pump 22 is matched to the pressure at the discharge end of the compressor 31. Therefore, the compressor 31 operates while receiving the inlet pressure of the high-pressure pump 22 (the pressure of the liquid-phase liquefied gas recovered through the liquefied gas recovery line L30) as resistance, and the discharge pressure of the compressor 31 can be adjusted upward.

[0189] That is, in this embodiment, when the temperature of the refrigerant used in the condenser 32 is too low, the downstream of the condenser 32 and the upstream of the high-pressure pump 22 are directly connected by the evaporation 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.

[0190] Therefore, in this embodiment, instead of bypassing the heat exchange with the low-temperature refrigerant, the gas-liquid separator 33 is bypassed and the downstream of the condenser 32 and the upstream of the high-pressure pump 22 are communicated so as to have the same pressure, whereby the discharge pressure of the compressor 31 can be adjusted to the inflow pressure of the high-pressure pump 22.

[0191] Thus, in this embodiment, in order to prepare for the case where the temperature of the refrigerant used in the condenser 32 is too low and the pressure of the vaporized gas in the liquid phase becomes inappropriate, the downstream of the compressor 31 and the upstream of the high-pressure pump 22 are communicated to adjust the discharge pressure of the compressor 31 to the inflow pressure of the high-pressure pump 22, thereby effectively preventing vaporization in the high-pressure pump 22.

[0192] FIG. 6 is a conceptual diagram of a gas treatment system according to a sixth embodiment of the present invention.

[0193] Referring to FIG. 6, the gas treatment system 1 according to the sixth embodiment of the present invention can omit the fuel tank 12 as compared with the fifth embodiment, and the liquefied gas transfer line L21, the evaporation gas transfer line L12, etc. may be omitted.

[0194] In this case, the liquefied gas supply line L20 may 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. may be provided on the liquefied gas supply line L20. At this time, the fact that the low-pressure pump 21 can be omitted is as described in the above-described third embodiment.

[0195] The re-liquefaction device in this embodiment can transmit the liquefied evaporation 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 re-liquefaction device can transmit the liquid phase separated by the gas-liquid separator 33 to the liquefied gas supply line L20 upstream of the high-pressure pump 22 so as to be supplied to the propulsion engine E.

[0196] Also, similar to the above-described embodiment, the re-liquefaction device liquefies the evaporation gas and transmits it to the high-pressure pump 22. By communicating the downstream of the condenser 32 and the upstream of the high-pressure pump 22 according to the temperature of the refrigerant, the discharge pressure of the compressor 31 can be adjusted to match the inflow pressure of the high-pressure pump 22.

[0197] FIG. 7 is a conceptual diagram of a gas treatment system according to a seventh embodiment of the present invention.

[0198] 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 as compared with the above-described embodiment, and other configurations may include at least any one of the configurations of the above-described embodiments.

[0199] The re-liquefaction device of this embodiment includes a compressor 31, a condenser 32, a gas-liquid separator 33, an aftercooler 35, and an evaporation gas heat exchanger 37. The compressor 31, the condenser 32, and the gas-liquid separator 33 are as described above, and detailed descriptions thereof are omitted.

[0200] The evaporation gas heat exchanger 37 exchanges heat between the evaporation gas transmitted from the cargo tank 10 to the compressor 31 and the evaporation gas liquefied by the condenser 32. Specifically, the evaporation gas heat exchanger 37 may have a two-stream structure having a stream through which the evaporation gas transmitted from the cargo tank 10 to the compressor 31 flows and a stream through which the evaporation gas transmitted from the gas-liquid separator 33 to the cargo tank 10 flows.

[0201] For example, the evaporation gas heat exchanger 37 may be provided on the evaporation gas return line L11 so as to have one stream alongside the evaporation gas discharge line L10 and another stream alongside the evaporation gas return line L11, and may be provided so as to replace the above-described intercooler 34. Needless to say, the evaporation gas heat exchanger 37 may be added to the above-described embodiment having the intercooler 34.

[0202] Since the evaporation gas liquefied by the condenser 32 is in a compressed state by the compressor 31, although it is in a liquid phase, the temperature may be higher than the boiling point at atmospheric pressure. On the other hand, the evaporation gas discharged from the cargo tank 10 can have a pressure at the atmospheric pressure level and a temperature close to the boiling point.

[0203] Therefore, the evaporation gas heat exchanger 37 can cool the evaporation gas transmitted from the gas-liquid separator 33 by heat-exchanging it with the low-temperature evaporation gas discharged from the cargo tank 10. At this time, although the pressures of the evaporation gas that is the object to be cooled and the evaporation gas that is the cooling medium in the evaporation gas heat exchanger 37 may be different from each other, the pressure difference can 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.

[0204] A pressure reducing valve (not shown) is provided at at least one point upstream or downstream of the evaporation gas heat exchanger 37 on the evaporation gas return line L11, and the evaporation gas compressed by the compressor 31 can be decompressed to realize additional cooling.

[0205] The reliquefaction device including such an evaporation gas heat exchanger 37 can operate in the fuel supply mode or the reliquefaction mode as described in the first embodiment above. That is, the reliquefaction device operates in the reliquefaction mode of transmitting the liquid phase separated by the gas-liquid separator 33 to the cargo tank 10 via the evaporation gas heat exchanger 37 provided on the evaporation gas return line L11, and / or operates in the fuel supply mode of transmitting the liquid phase separated by the gas-liquid separator 33 to the fuel tank 12 via the evaporation gas transmission line L12 so as to be supplied to the propulsion engine E.

[0206] In this way, in this embodiment, by using the evaporative gas heat exchanger 37 instead of the intercooler 34, the structure of the re-liquefaction device can be simplified, and since the circulation of the evaporative gas through the intercooler 34 is omitted, the re-liquefaction capacity of the re-liquefaction device can be increased.

[0207] In addition to the above-described embodiments, the present invention can include, as further embodiments, combinations of at least any one of the embodiments and the prior art, and combinations of at least two or more of the embodiments.

[0208] As described above, the present invention has been described in detail through specific embodiments, but this is for specifically describing the present invention, and the present invention is not limited thereto. It is obvious that those with ordinary knowledge in the art can make modifications and improvements within the technical idea of the present invention.

[0209] All simple modifications and changes of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

Claims

1. 1. A system for processing a liquefied gas, the liquefied gas being a heavy hydrocarbon or ammonia, comprising: a liquefied gas supply line that supplies the liquefied gas stored in the cargo tank to the propulsion engine in a liquid phase and is provided with a high-pressure pump; a re-liquefaction device for liquefying evaporated gas generated in the cargo tank and transmitting the liquefied gas to the high-pressure pump; a liquefied gas recovery line that recovers the liquid-phase liquefied gas discharged from the propulsion engine upstream of the high-pressure pump, The reliquefaction device is A condenser that liquefies the evaporated gas by cooling it with a refrigerant; a buffer for temporarily storing the evaporated gas liquefied by the condenser; A gas processing system comprising: a bypass line for allowing at least a portion of the evaporated gas to be supplied to the buffer by bypassing the condenser in preparation for pressure fluctuations of the evaporated gas transmitted from the buffer to the high-pressure pump in response to the temperature of the refrigerant.

2. The above liquefied gas recovery line is 2. The gas treatment system according to claim 1, further comprising a pressure reducing valve for reducing the pressure of the surplus liquid-phase liquefied gas discharged from the propulsion engine and mixed with lubricating oil, and the surplus liquid-phase liquefied gas mixed with the lubricating oil used in the propulsion engine is transferred through the inside of the propulsion engine to the liquefied gas supply line upstream of the high-pressure pump so as to be re-flowed into the propulsion engine.

3. The above liquefied gas recovery line is 3. The gas processing system according to claim 2, further comprising a cooler for cooling the liquefied gas depressurized by the pressure reducing valve so that the liquefied gas flows into the high-pressure pump in a liquid phase.

4. The above buffer is 2. The gas processing system according to claim 1, further comprising a gas-liquid separator for separating the evaporated gas liquefied by the condenser into gas and liquid.

5. The reliquefaction device is 5. The gas processing system of claim 4, further comprising: transmitting liquefied vapor to said liquefied gas supply line between said cargo tank and said high pressure pump.

6. The reliquefaction device is a compressor that compresses the evaporated gas discharged from the cargo tank in multiple stages; 6. The gas processing system according to claim 5, further comprising an intercooler for mutually exchanging heat between a portion of the evaporated gas liquefied in the condenser and the remainder, and for transferring the evaporated gas generated by the heat exchange to the compressor.

7. The reliquefaction device is 7. The gas processing system according to claim 6, wherein the gas processing system operates in at least one of a re-liquefaction mode in which the liquid phase separated in the gas-liquid separator is transferred to the cargo tank via the intercooler, and a fuel supply mode in which the liquid phase separated in the gas-liquid separator is transferred to the liquefied gas supply line upstream of the high-pressure pump to be supplied to the propulsion engine.

8. A ship, characterized in that it is a liquefied gas carrier, comprising the gas treatment system according to any one of claims 1 to 7.

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