Gas processing system and ship comprising the same

Abstract

The present invention relates to a gas processing system and a ship including the gas processing system, wherein the gas processing system is a system for processing liquefied gas as heavy hydrocarbon or ammonia, which includes: a fuel tank for storing liquefied gas as fuel to be supplied to a propulsion engine of the ship; a liquefied gas supply line for supplying the liquefied gas in the fuel tank to the propulsion engine in a liquid state and provided with a high-pressure pump; a reliquefaction device for liquefying boil-off gas generated in a liquid tank for storing liquefied gas; and a liquefied gas recovery line for recovering the liquefied gas discharged from the propulsion engine to the upstream of the high-pressure pump, and the reliquefaction device for conveying the liquefied boil-off gas to the fuel tank for supplying it to the propulsion engine through the high-pressure pump.

Description

Technical Field

[0001] The invention relates to a gas processing system and a ship comprising the gas processing system. Background Art

[0002] Generally, liquefied petroleum gas (LPG) is obtained by liquefying the low-boiling hydrocarbons such as propane and butane in petroleum under pressure at room temperature. This liquefied petroleum gas is widely used as a fuel for homes, businesses, industries, and automobiles by filling small and light pressure containers (steel cylinders).

[0003] Liquefied petroleum gas is extracted in a gaseous state at the production site, liquefied and stored by liquefied petroleum gas processing equipment, and then transported to land by liquefied petroleum gas tankers while maintaining its liquid state. It is then supplied to the demand side in various forms such as gas.

[0004] The boiling point of this liquefied petroleum gas is about -50°C, so the liquefied petroleum gas tanker used to transport liquefied petroleum gas needs to maintain a temperature lower than this temperature. Therefore, the storage tanks for storing liquefied petroleum gas use low-temperature steel (Low Temperature Carbon Steel and Nickel Steel) that are resistant to low temperatures, and the liquefied petroleum gas tanker is also equipped with reliquefaction equipment.

[0005] Conventionally, such LPG carriers use diesel to drive engines to generate propulsion. However, when diesel is burned in the ship's propulsion engine, harmful components such as nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO2) are produced, which are then discharged into the atmosphere, causing environmental pollution.

[0006] Therefore, in recent years, the development of engines driven by liquefied petroleum gas and the development of various systems for supplying liquefied petroleum gas to engines have been progressing in order to significantly reduce the pollution level of exhaust gas compared to the case of using diesel. Summary of the invention

[0007] Problems to be solved by the invention

[0008] The present invention is proposed to solve the problems of the prior art as described above. The object of the present invention is to provide a gas processing system capable of generating propulsion force by using liquefied petroleum gas or ammonia and a ship including the gas processing system.

[0009] Technical solutions to the problem

[0010] A gas processing system according to one aspect of the present invention is a system for processing liquefied gas such as heavy hydrocarbons or ammonia, comprising: a fuel tank storing liquefied gas as fuel to be supplied to a propulsion engine of a ship; a liquefied gas supply line supplying the liquefied gas in the fuel tank to the propulsion engine in a liquid state and provided with a high-pressure pump; a reliquefaction device liquefying boil-off gas generated in a liquid tank storing the liquefied gas; and a liquefied gas recovery line recovering the liquid liquefied gas discharged from the propulsion engine upstream of the high-pressure pump, the reliquefaction device conveying the liquefied boil-off gas to the fuel tank to be supplied to the propulsion engine through the high-pressure pump.

[0011] Specifically, the liquefied gas recovery line may be provided with a pressure reducing valve for reducing the pressure of excess liquid liquefied gas discharged from the propulsion engine and mixed with lubricating oil. The liquefied gas recovery line transports the excess liquid liquefied gas mixed with the lubricating oil used in the propulsion engine when passing through the interior of the propulsion engine to the liquefied gas supply line upstream of the high-pressure pump so that it can flow back into the propulsion engine.

[0012] Specifically, the liquefied gas recovery line may be provided with a cooler that cools the liquefied gas decompressed by the decompression valve and flows the liquefied gas into the high-pressure pump in a liquid state.

[0013] Specifically, the reliquefaction device may include: a compressor, which performs multi-stage compression on the boil-off gas discharged from the liquid tank; a condenser, which uses a refrigerant to cool the compressed boil-off gas to liquefy it; and an intercooler, which allows a part of the boil-off gas liquefied in the condenser to exchange heat with the rest, and transports the boil-off gas generated by the heat exchange to the compressor.

[0014] Specifically, the reliquefaction device may also include a gas-liquid separator for separating the evaporated gas liquefied in the condenser into gas and liquid. The reliquefaction device can operate in at least one of a reliquefaction mode and a fuel supply mode. In the reliquefaction mode, the liquid phase separated in the gas-liquid separator is transported to the liquid tank via the intercooler. In the fuel supply mode, the liquid phase separated in the gas-liquid separator is transported to the fuel tank to be supplied to the propulsion engine.

[0015] Specifically, the reliquefaction device may include: a compressor for performing multi-stage compression on the boil-off gas discharged from the liquid tank; a condenser for cooling the compressed boil-off gas to liquefy it; and a boil-off gas heat exchanger for performing heat exchange between the boil-off gas transported from the liquid tank to the compressor and the boil-off gas liquefied in the condenser.

[0016] Specifically, the reliquefaction device may also include a gas-liquid separator for separating gas and liquid from the evaporated gas liquefied in the condenser. The reliquefaction device may operate in at least one of a reliquefaction mode and a fuel supply mode. In the reliquefaction mode, the liquid phase separated in the gas-liquid separator is transported to the liquid tank via the evaporated gas heat exchanger. In the fuel supply mode, the liquid phase separated in the gas-liquid separator is transported to the fuel tank to be supplied to the propulsion engine.

[0017] According to another aspect of the present invention, a gas processing system is a system for processing liquefied gas such as heavy hydrocarbons or ammonia, which includes: a liquefied gas supply line, which supplies the liquefied gas stored in a liquid tank to the propulsion engine in a liquid state, and is provided with a high-pressure pump; a reliquefaction device, which liquefies the evaporated gas generated in the liquid tank and transports it to the high-pressure pump; and a liquefied gas recovery line, which recovers the liquid liquefied gas discharged from the propulsion engine to the upstream of the high-pressure pump, the reliquefaction device including: a condenser, which cools the evaporated gas with a refrigerant to liquefy it; and a buffer, which temporarily stores the evaporated gas liquefied in the condenser, the reliquefaction device having a bypass line for bypassing at least a portion of the evaporated gas to the buffer to supply it to the buffer, so as to cope with the pressure of the evaporated gas transported from the buffer to the high-pressure pump changing according to the temperature of the refrigerant.

[0018] Specifically, the liquefied gas recovery line may be provided with a pressure reducing valve for reducing the pressure of excess liquid liquefied gas discharged from the propulsion engine and mixed with lubricating oil. The liquefied gas recovery line transports the excess liquid liquefied gas mixed with the lubricating oil used in the propulsion engine when passing through the interior of the propulsion engine to the liquefied gas supply line upstream of the high-pressure pump so that it can flow back into the propulsion engine.

[0019] Specifically, the liquefied gas recovery line may be provided with a cooler that cools the liquefied gas decompressed by the decompression valve and flows the liquefied gas into the high-pressure pump in a liquid state.

[0020] Specifically, the buffer may be a gas-liquid separator for performing gas-liquid separation on the boil-off gas liquefied in the condenser.

[0021] Specifically, the reliquefaction device may transfer the liquefied boil-off gas to the liquefied gas supply line between the liquid tank and the high-pressure pump.

[0022] Specifically, the reliquefaction device may include: a compressor for performing multi-stage compression on the boil-off gas discharged from the liquid tank; and an intercooler for exchanging heat between a portion of the boil-off gas liquefied in the condenser and the rest, and delivering the boil-off gas generated by the heat exchange to the compressor.

[0023] Specifically, the reliquefaction device can operate in at least one of a reliquefaction mode and a fuel supply mode. In the reliquefaction mode, the liquid phase separated in the gas-liquid separator is transported to the liquid tank via the intercooler. In the fuel supply mode, the liquid phase separated in the gas-liquid separator is transported to the liquefied gas supply line upstream of the high-pressure pump to be supplied to the propulsion engine.

[0024] The ship of the present invention is a liquefied gas tanker having the gas processing system.

[0025] Effects of the Invention

[0026] The gas processing system and the ship including the gas processing system according to the present invention can get rid of the existing system which only uses diesel and use liquefied petroleum gas or ammonia as propulsion fuel to reduce environmental pollution and improve energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1 is a conceptual diagram of a gas processing system according to a first embodiment of the present invention.

[0028] Figure 2 4 is a conceptual diagram of a gas processing system according to a second embodiment of the present invention.

[0029] Figure 3 4 is a conceptual diagram of a gas processing system according to a third embodiment of the present invention.

[0030] Figure 4 4 is a conceptual diagram of a gas processing system according to a fourth embodiment of the present invention.

[0031] Figure 5 is a conceptual diagram of a gas processing system according to a fifth embodiment of the present invention.

[0032] Figure 6 is a conceptual diagram of a gas processing system according to a sixth embodiment of the present invention.

[0033] Figure 7 is a conceptual diagram of a gas processing system according to a seventh embodiment of the present invention. DETAILED DESCRIPTION

[0034] The purpose, specific advantages and novel features of the present invention will become more apparent through the following detailed description and preferred embodiments in conjunction with the accompanying drawings. It should be noted that when assigning reference numerals to the constituent elements of the various drawings of this specification, the same reference numerals are used as much as possible for the same constituent elements even if they are shown on different drawings. In addition, when describing the present invention, if it is determined that the specific description of the relevant known technology may unnecessarily confuse the subject matter of the present invention, its detailed description will be omitted.

[0035] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. For reference, in this specification, the liquefied gas may be LPG (propane, butane, etc.) or ammonia, etc., which are heavy hydrocarbons, but is not limited thereto and may include all substances having a boiling point lower than room temperature and having a calorific value.

[0036] In addition, it should be noted that in this specification, liquefied gas / evaporated gas is not necessarily limited to liquid or gaseous due to the name.

[0037] The present invention includes a ship provided with a gas processing system described below. At this time, it should be noted that the ship is a concept including all gas tankers, merchant ships that transport non-gas cargo or people, FSRU (Floating Storage and Regasification Unit), FPSO (Floating Production Storage and Offloading), bunker vessels, offshore factories, etc., and an example thereof may be a liquefied gas tanker.

[0038] Although not shown in the drawings of the present invention, the pressure sensor PT, the temperature sensor TT, etc. can obviously be set at appropriate positions without restriction, and the measurement values ​​measured by each sensor can be used in various ways in the operation of the structure described below without restriction.

[0039] Figure 1 1 is a conceptual diagram of a gas processing system according to a first embodiment of the present invention.

[0040] Reference Figure 1 The gas processing system 1 according to the first embodiment of the present invention includes a gas storage unit, a fuel supply unit 20 , a reliquefaction unit 30 , and a fuel recovery unit 40 .

[0041] The gas storage unit is a structure for storing liquefied gas, and includes a liquid tank 10, a fuel tank 12, and the like.

[0042] The cargo tanks 10 are a plurality of cargo tanks installed in a ship that is a liquefied gas carrier. Of course, when the ship is a ship type other than a gas carrier, it may be a tank or container that is additionally installed in or outside the ship.

[0043] The liquid tank 10 is a tank for storing liquefied gas in a low temperature liquid state under atmospheric pressure, and a plurality of heat insulation structures can be added to its wall to prevent the gasification of the liquefied gas. In addition, the liquid tank 10 can be a film type tank or an independent type tank, and its form or specification is not limited.

[0044] A liquefied gas delivery line L21 may be provided from the liquid tank 10 to a fuel tank 12 described later, and the liquefied gas in the liquid tank 10 is delivered to the fuel tank 12 through the liquefied gas delivery line L21. The liquefied gas delivered to the fuel tank 12 is used as fuel for the propulsion engine E.

[0045] For reference, in this specification, the propulsion engine E can be interpreted as any structure that is not an engine, such as a turbine, a fuel cell, etc., as long as it is used to propel the ship, and can be interpreted as all structures that can directly or indirectly generate propulsion by consuming liquefied gas. In addition, in this specification, the propulsion engine E can be used as a term including all gas-demanding places such as engines for propulsion, engines for power generation, and gas combustion devices.

[0046] The liquid tank 10 may be provided with a transfer pump 11, and a liquefied gas delivery line L21 may be connected to the transfer pump 11. The transfer pump 11 may be provided inside the liquid tank 10, and may be provided as a submerged type immersed in the liquefied gas.

[0047] The transfer pump 11 may be provided in a part of the plurality of liquid tanks 10. The liquid tanks 10 are basically used for transporting cargoes, and each liquid tank 10 is provided with at least two cargo pumps (unloading pumps, stripping pumps, etc., not shown) for unloading cargoes, wherein at least one of the liquid tanks 10 may be provided with a transfer pump 11 in addition to the cargo pumps, so that the liquefied gas stored inside can be used as fuel for a propulsion engine E (ME-LGI) or the like.

[0048] As an example, when four liquid tanks 10 are arranged side by side along the length direction of the ship, the liquefied gas stored in the No. 4 liquid tank 10 close to the engine room accommodating the propulsion engine E can be transported to the fuel tank 12 and then used as fuel for the propulsion engine E. For this purpose, a transfer pump 11 can be provided only in the No. 4 liquid tank 10.

[0049] The liquefied gas stored in the liquid tank 10 is naturally evaporated by being soaked in external heat, thereby generating boil-off gas in the liquid tank 10. A boil-off gas discharge line L10 for discharging boil-off gas may be provided in the liquid tank 10. The boil-off gas discharged from the liquid tank 10 may be liquefied and returned or used as fuel for the propulsion engine E, which will be described in detail in the following section describing the reliquefaction unit 30.

[0050] The liquid tank 10 may be provided in a plurality to store at least two liquefied gases (propane, butane, propylene, etc.) of the liquefied gases having heavy hydrocarbons as main components, respectively. That is, the liquid tank 10 may include a first liquid tank 10 storing a first liquefied gas and a second liquid tank 10 storing a second liquefied gas. For example, the first liquid tank 10 may store propane, and the second liquid tank 10 may store butane, etc.

[0051] The evaporated gas in the liquid tank 10 is liquefied by the condenser 32 of the reliquefaction section 30 described later. When the liquefied evaporated gas is returned to the liquid tank 10, the condenser 32 may be provided with at least as many types as the types of liquefied gas stored in the liquid tank 10 (an additional spare one may be provided).

[0052] That is, when the liquid tank 10 stores two kinds of liquefied gases, it is preferable to provide at least three condensers 32. In addition, since the compressor 31 and the condenser 32 are provided as a set, a plurality of compressors 31 may be provided corresponding to the number of condensers 32.

[0053] However, in this embodiment, by transporting the evaporated gas liquefied by the condenser 32 to the fuel tank 12, etc. instead of returning it to the liquid tank 10, even if the liquid tank 10 is configured to store more than two types of liquefied gases, the number of settings (or the number of operations) of the condenser 32 can be reduced to less than the number of types of liquefied gases.

[0054] That is, the evaporated gas of the liquid tank 10 can be transported to the condenser 32 through the evaporated gas discharge line L10, and liquefied in the condenser 32 through refrigerant heat exchange. The liquefied evaporated gas can be transported to the high-pressure pump 22 described later via the fuel tank 12 without returning to the liquid tank 10 (fuel supply mode).

[0055] The fuel tank 12 stores liquefied gas as fuel to be supplied to the propulsion engine E. The fuel tank 12 may be an independent type (SPB type, MOSS type) that stores a large amount of liquefied gas at atmospheric pressure or a type that is the same as or different from the membrane type liquid tank 10, and may be an independent type (Type C, pressure vessel type) that stores liquefied gas at high pressure.

[0056] At this time, the fuel tank 12 can store the liquefied gas above the critical pressure (for example, about 18 bar), or store it below the critical pressure (for example, about 8 bar), and in order to prevent the liquefied gas from vaporizing, an insulating structure can be provided on at least one side inside or outside the wall.

[0057] The fuel tank 12 can be installed on the upper deck of the ship and is arranged to be supported on the upper deck by a saddle. The fuel tank 12 can be arranged at a position on the upper deck that does not interfere with the structure (manifold, etc.) for loading / unloading the liquefied gas of the liquid tank 10 and does not block the visibility when the ship is sailing. As an example, the fuel tank 12 can be arranged on the port side or starboard side of the bow side of the upper deck. In this case, the fuel tank 12 can be called a deck tank.

[0058] The fuel tank 12 may be configured to temporarily store liquefied gas between the liquid tank 10 and the propulsion engine E. Alternatively, the fuel tank 12 may be configured to condense evaporated gas generated in the liquid tank 10 using the liquefied gas stored therein.

[0059] That is, the fuel tank 12 can also be used as a recondenser 32, and uses the liquefied gas stored therein to receive and condense the boil-off gas generated in the liquid tank 10. For this purpose, an boil-off gas branch line (not shown) branching from the upstream of the condenser 32 toward the fuel tank 12 can be provided on the boil-off gas discharge line L10 extending from the liquid tank 10.

[0060] The liquefied gas delivery line L21 described above can be connected from the liquid tank 10 to the fuel tank 12, and the liquefied gas can be delivered to the fuel tank 12 by the transfer pump 11 immersed in the liquid tank 10. The liquefied gas stored in the fuel tank 12 can be managed to an appropriate level / pressure in consideration of the navigation status of the ship.

[0061] Conversely, the liquefied gas may also be returned from the fuel tank 12 to the liquid tank 10 , but this may be limited to a case where the composition of the liquefied gas stored in the fuel tank 12 is the same as that of the liquefied gas stored in the liquid tank 10 .

[0062] The liquefied gas stored in the fuel tank 12 can be transported from the fuel tank 12 to the propulsion engine E by the low-pressure pump 21 of the fuel supply unit 20 described later. A liquefied gas supply line L20 is provided from the fuel tank 12 to the propulsion engine E. That is, a liquefied gas delivery line L21 is provided from the liquid 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.

[0063] Of course, the liquefied gas supply line L20 can also be set to bypass the fuel tank 12 from the liquid tank 10 to supply liquefied gas to the propulsion engine E. In this case, the liquefied gas supply line L20 can transport the liquefied gas from the liquid tank 10 and / or the fuel tank 12 to the propulsion engine E.

[0064] The fuel supply unit 20 supplies liquefied gas to the propulsion engine E to operate the propulsion engine E. The fuel supply unit 20 may include a low-pressure pump 21, a high-pressure pump 22, a heat exchanger 23, etc., and may also be provided with a filter (not shown) at an appropriate position.

[0065] The low-pressure pump 21 delivers the liquefied gas of 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 a liquefied gas supply line L20 connected from the fuel tank 12 to the propulsion engine E.

[0066] The low-pressure pump 21 can pressurize the liquefied gas to a pressure lower than the pressure required by the propulsion engine E. Specifically, the low-pressure pump 21 can pressurize the liquefied gas according to the suction pressure (e.g., 20 bar) of the high-pressure pump 22 arranged downstream. That is, the low-pressure pump 21 increases the pressure of the liquefied gas by the pressure difference between the internal pressure of the fuel tank 12 and the suction pressure of the high-pressure pump 22.

[0067] 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.

[0068] A liquefied gas return line (not shown) may be provided downstream of the low-pressure pump 21 of the liquefied gas supply line L20. The liquefied gas return line may be used to recover excess liquefied gas to the fuel tank 12 when the flow rate delivered to the propulsion engine E by the low-pressure pump 21 exceeds the required flow rate of the propulsion engine E.

[0069] Alternatively, the liquefied gas return line can allow the liquefied gas, which is pressurized by the low-pressure pump 21 and then discharged from the fuel tank 12, to flow back into the fuel tank 12, thereby realizing the function of increasing the internal pressure of the fuel tank 12. Therefore, the fuel tank 12 can minimize the generation of boil-off gas in the fuel tank 12 by maintaining a high internal pressure.

[0070] 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 delivers it to the propulsion engine E. The required pressure of the propulsion engine E may be 20 to 50 bar, but may vary depending on the specifications of the propulsion engine E.

[0071] 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 as shown in the figure, a plurality of high-pressure pumps 22 may be provided in parallel to be able to back up each other.

[0072] The high-pressure pump 22 can be arranged upstream of the heat exchanger 23 described later as shown in the figure, or it can be arranged downstream of the heat exchanger 23 differently from the figure. In the latter case, the high-pressure pump 22 can pressurize the liquefied gas whose temperature is adjusted by the heat exchanger 23 to the pressure required by the propulsion engine E.

[0073] To suppress cavitation during pressurization of the liquefied gas by the high pressure pump 22, the liquefied gas may flow in a liquid state into the high pressure pump 22. When the heat exchanger 23 is disposed upstream of the high pressure pump 22, the heat exchanger 23 may control the temperature of the liquefied gas in consideration of the above.

[0074] The pressure of the liquefied gas sucked into the high-pressure pump 22 may correspond to the pressure of the liquefied gas discharged from the low-pressure pump 21. Alternatively, the pressure of the liquefied gas recovered from the propulsion engine E may correspond to the pressure of the liquefied gas.

[0075] A filter (not shown) for filtering out impurities may be provided downstream of the high-pressure pump 22. As shown in the figure, the filter may also be additionally provided upstream of the low-pressure pump 21.

[0076] In addition, a fuel supply valve (not shown) can be arranged downstream of the high-pressure pump 22 of the liquefied gas supply line L20. In this case, the fuel supply valve and the pressure reducing valve (not shown) arranged on the liquefied gas recovery line L30 can be formed into a group and called FVT (fuel valve train).

[0077] A liquefied gas circulation line L22 connected to a liquefied gas recovery line L30 of a 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 transported to the liquefied gas recovery line L30 along the liquefied gas circulation line L22 and circulated to the high-pressure pump 22 again.

[0078] For the sake of operational stability, etc., a minimum required flow rate is set for the high-pressure pump 22. This is called a minimum flow rate, and during operation, it is preferred that liquefied gas that satisfies the minimum required flow rate flows into the high-pressure pump 22.

[0079] However, there are cases where the consumption of the propulsion engine E downstream of the high-pressure pump 22 does not meet the minimum required flow rate of the high-pressure pump 22. As an example, this is the case where the propulsion engine E is operating at a low load or is stopped while the high-pressure pump 22 is operating.

[0080] At this time, in this embodiment, in order to make the high-pressure pump 22 work stably, even if the required flow rate of the propulsion engine E does not reach the minimum required flow rate of the high-pressure pump 22, in order to allow liquefied gas exceeding the minimum required flow rate to flow into the high-pressure pump 22, the liquefied gas can be circulated.

[0081] 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 liquefied gas can be circulated to the high-pressure pump 22 from the downstream of the high-pressure pump 22 via the liquefied gas circulation line L22 and the liquefied gas recovery line L30.

[0082] Therefore, when the required flow rate of the propulsion engine E is lower than the minimum required flow rate of the high-pressure pump 22, the liquefied gas circulation line L22 can ensure the minimum required flow rate of the high-pressure pump 22 by circulating the minimum required flow rate of the high-pressure pump 22 minus the required flow rate of the propulsion engine E.

[0083] The heat exchanger 23 is disposed downstream of the low-pressure pump 21 and changes the temperature of the liquefied gas. The heat exchanger 23 can increase or decrease the temperature of the liquefied gas, and thus may also be referred to as a fuel conditioner.

[0084] As an example, during the initial operation of this embodiment, since the flow rate of high-temperature liquefied gas recovered from the propulsion engine E is large, the heat exchanger 23 can lower the temperature of the liquefied gas. When entering stable operation, the heat exchanger 23 can increase the temperature of the liquefied gas.

[0085] As shown in the figure, the heat exchanger 23 can be arranged downstream of the high-pressure pump 22, but different from the figure, the heat exchanger 23 can also be arranged upstream of the high-pressure pump 22. In the latter case, the heat exchanger 23 can adjust the temperature of the liquefied gas to below the boiling point of the liquefied gas to prevent the gaseous liquefied gas from flowing into the high-pressure pump 22.

[0086] The heat exchanger 23 can utilize a variety of heat exchange media to achieve heat exchange with the liquefied gas. As an example, the heat exchange medium can be seawater, clean water, ethylene glycol water, exhaust gas, etc., but is not limited thereto.

[0087] The reliquefaction unit 30 liquefies the boil-off gas generated in the liquid tank 10. The reliquefaction unit 30 may be formed by arranging various modules on one slide rail to form a reliquefaction device, and the reliquefaction unit 30 may include a plurality of reliquefaction devices. However, for convenience, only one reliquefaction device is shown in the drawings.

[0088] This reliquefaction device includes a compressor 31, a condenser 32, a gas-liquid separator 33, an intermediate cooler 34, and an aftercooler 35. At this time, the compressor 31, the aftercooler 35, the condenser 32, and the gas-liquid separator 33 can be sequentially arranged in series on the boil-off gas discharge line L10, and the intermediate cooler 34 can be arranged on the boil-off gas return line L11 connected from the gas-liquid separator 33 to the liquid tank 10.

[0089] The compressor 31 compresses the boil-off gas discharged from the liquid tank 10. The compressor 31 can increase the boiling point of the boil-off gas by compression, thereby being able to improve the liquefaction efficiency in the condenser 32 to be described below.

[0090] The compressor 31 may be configured in multiple stages, such as three stages as shown in the figure, or may be configured in multiple stages other than these. In addition, the compressor 31 may be provided in parallel on the evaporation gas discharge line L10 so as to be able to provide backup for each other.

[0091] The compressor 31 may deliver the compressed boil-off gas to the condenser 32 so that it can be liquefied, or may deliver it to the fuel tank 12 filled with an appropriate amount of liquefied gas. In the former case, the boil-off gas liquefied in the condenser 32 is supplied to the fuel tank 12, and in the latter case, the high-pressure boil-off gas may be directly injected into the fuel tank 12 and cooled by the liquefied gas in the fuel tank 12 to be liquefied.

[0092] A drum (not shown) may be provided upstream of the compressor 31 . The drum is a gas-liquid separation structure for filtering liquid droplets in the boil-off gas discharged from the liquid tank 10 , and the liquid droplets may be provided to return to the liquid tank 10 .

[0093] The drum may protect the compressor 31 by preventing liquid droplets from flowing into the compressor 31 , and may be omitted depending on the type of the compressor 31 .

[0094] The condenser 32 liquefies the boil-off gas generated in the liquid tank 10. The boil-off gas can be liquefied using a refrigerant, which may be glycol water, nitrogen, or seawater. However, in the following description, it is assumed that the refrigerant of the condenser 32 is seawater.

[0095] The condenser 32 may have a dual-stream structure including a boil-off gas flow into which boil-off gas compressed by the compressor 31 flows, and a refrigerant flow into which a refrigerant for heat exchange with the boil-off gas flows.

[0096] The type of the condenser 32 is not limited to Shell & Tube, PCHE, etc., and may be a bath type in which boil-off gas passes through a shell storing refrigerant for heat exchange.

[0097] As mentioned above, the liquid tank 10 may be provided in plural to store at least two liquefied gases respectively, and the condenser 32 may be provided to liquefy all boil-off gases of different types.

[0098] In the case where a plurality of liquid tanks 10 storing different types of liquefied gases are provided, a plurality of condensers 32 may be provided corresponding to the types of liquefied gases. Alternatively, as described above, in this embodiment, the number of condensers 32 to be provided (or the number of condensers to be operated) may be reduced by uniformly delivering different types of boil-off gases to one condenser 32.

[0099] This is because the reliquefaction apparatus of this embodiment can be operated to deliver the liquefied boil-off gas to the fuel tank 12 instead of the liquid tank 10 for consumption by the propulsion engine E (fuel supply mode).

[0100] Of course, even if the boil-off gas liquefied in the condenser 32 is returned to the liquid tank 10 , if component contamination does not occur in the liquid tank 10 , the reliquefaction device may operate in the reliquefaction mode for transferring the liquefied boil-off gas to the liquid tank 10 .

[0101] The gas-liquid separator 33 temporarily stores the boil-off gas liquefied in the condenser 32. The gas-liquid separator 33 may have a container shape or a partially expanded pipe shape, etc., so as to have a buffer function.

[0102] The gas-liquid separator 33 separates the liquefied boil-off gas into a gas phase and a liquid phase, and then the liquid phase can be transported to the liquid tank 10 or the fuel tank 12, etc. The gas-liquid separator 33 can transport only the liquid phase to the liquid tank 10, etc., and contain the gas phase therein, and by maintaining a predetermined level of internal pressure, it is possible to prevent the boil-off gas from being vaporized.

[0103] As described above, in order to prevent mixing of the components of the liquefied gas (or in order to supply the evaporated gas to the propulsion engine E), the reliquefaction device can be operated in a fuel supply mode in which the liquefied evaporated gas is delivered to the fuel tank 12 instead of the liquid tank 10. To this end, the gas-liquid separator 33 can be provided with an evaporated gas delivery line L12 for delivering the liquid phase to the fuel tank 12.

[0104] Alternatively, in order to operate the reliquefaction device in the reliquefaction mode, a boil-off gas return line L11 may be provided from the gas-liquid separator 33 to the liquid tank 10 , and an intercooler 34 may be provided on the boil-off gas return line L11 .

[0105] Therefore, the reliquefaction device can operate in at least one of a reliquefaction mode in which the liquid phase separated in the gas-liquid separator 33 is transported to the liquid tank 10 via the intercooler 34, and / or a fuel supply mode in which the liquid phase separated in the gas-liquid separator 33 is transported to the fuel tank 12 to be supplied to the propulsion engine E.

[0106] That is, the reliquefaction device can also be operated in a mode combining the reliquefaction mode and the fuel supply mode. In the case of the combined mode, part of the liquid phase separated in the gas-liquid separator 33 is sent to the liquid tank 10, and the rest is sent 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.

[0107] The intercooler 34 exchanges heat between a portion of the boil-off gas liquefied in the condenser 32 and the rest, and sends gas-phase boil-off gas generated by the heat exchange among the boil-off gas flowing in from the condenser 32 to the compressor 31 .

[0108] The intercooler 34 is used to cool the boil-off gas in the middle stage of the compressor 31 composed of multiple stages. When the boil-off gas is compressed by the compressor 31, the temperature rises due to the compression heat. In this case, there is a problem of increasing the load of the compressor 31. Therefore, in this embodiment, the intercooler 34 can be used for intermediate cooling.

[0109] Specifically, the intercooler 34 is configured in the form of a container that stores a portion of the boil-off gas liquefied in the condenser 32 , and uses the boil-off gas stored therein as a refrigerant for cooling the rest of the boil-off gas liquefied in the condenser 32 (the flow rate delivered to the liquid tank 10 ).

[0110] To this end, the evaporated gas return line L11 branches from the upstream of the intercooler 34, wherein one side transports the evaporated gas into the intercooler 34, and the other side passes through the interior of the intercooler 34 for heat exchange with the evaporated gas stored in the intercooler 34, and then is connected to the liquid tank 10.

[0111] That is, the intercooler 34 can fully liquefy the boil-off gas delivered to the tank 10 by exchanging heat between the boil-off gas delivered to the tank 10 from the condenser 32 and the boil-off gas received from the condenser 32 and stored therein.

[0112] At this time, in order to improve the heat exchange efficiency, the part from the evaporative gas return line L11 passing through the interior of the intercooler 34 can be set to a coiled form. In addition, in order to improve the cooling efficiency, a pressure reducing valve (not shown) can be provided in the part that transports the evaporative gas from the evaporative gas return line L11 to the interior of the intercooler 34.

[0113] In addition, the intercooler 34 delivers the gas phase of the boil-off gas stored therein to the intermediate stage of the compressor 31. The boil-off gas in the gas phase delivered 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 boil-off gas at the intermediate stage of the compressor 31 can be mixed with the gas phase boil-off gas delivered from the intercooler 34 and cooled.

[0114] An intercooler 34 may be provided at each intermediate stage of the multi-stage compressor 31. However, in this case, the boil-off gas circulates through the intercooler 34, and the amount of boil-off gas that can flow from the liquid tank 10 to the reliquefaction device may be limited due to the amount of boil-off gas delivered from the intercooler 34 to the intermediate stage of the compressor 31.

[0115] That is, the reliquefaction device has a reliquefaction capacity equal to the allowable inflow of the first stage of the compressor 31 minus the amount of boil-off gas delivered to the intermediate stage of the compressor 31 by the intercooler 34. As an example, when the allowable inflow of the first stage of the compressor 31 is 800, if 200 of boil-off gas is circulated to the intermediate stages (between the first stage and the second stage and between the second stage and the third stage) of the compressor 31 through the intercooler 34, the amount of boil-off gas that the reliquefaction device can finally receive from the liquid tank 10 is reduced to 400.

[0116] To improve this, in the present embodiment, the intercooler 34 is disposed only in a portion of the intermediate stage of the compressor 31, and an aftercooler 35 is provided in the remaining portion of the intermediate stage of the compressor 31 instead of the intercooler 34, thereby increasing the capacity of the reliquefaction device.

[0117] The intercooler 34 may be replaced by a separator. Similar to the gas-liquid separator 33 described above, the separator can separate the boil-off gas liquefied in the condenser 32 into gas and liquid, thereby delivering the liquid phase to the liquid tank 10 and the gas phase to the intermediate stage of the compressor 31. In this case, the separator only separates the boil-off gas into gas and liquid, and does not realize heat exchange between the boil-off gases, so the coiled boil-off gas return line L11 can be omitted therein.

[0118] The aftercooler 35 may be provided at a portion in the middle stage of the compressor 31 and may cool the boil-off gas using an additional refrigerant. From the viewpoint of the condenser 32, the aftercooler 35 may implement the function of a precooler.

[0119] The aftercooler 35 can use a refrigerant such as seawater similar to the condenser 32 , or can use a variety of refrigerants. However, the aftercooler 35 can use an additional refrigerant supplied from the outside instead of the liquefied gas stored in the liquid tank 10 or the boil-off gas discharged from the liquid tank 10 .

[0120] Referring to the drawings, in this embodiment, the gas-phase boil-off gas is circulated by connecting an intercooler 34 between the first and second stages of the compressor 31 , and an aftercooler 35 may be provided between the second and third stages of the compressor 31 .

[0121] At this time, if the allowable inflow rate of the first stage of the compressor 31 is 800 and the circulation rate of the intercooler 34 is 200, in this embodiment, an allowable boil-off gas amount of 600 is delivered from the liquid tank 10 to the reliquefaction device.

[0122] That is, compared with a case where all intermediate stages of the compressor 31 of the reliquefaction device are respectively connected to the intercooler 34 , in this embodiment, at least one intercooler 34 is replaced with the aftercooler 35 , thereby increasing the reliquefaction capacity.

[0123] The reliquefaction unit 30 of the present embodiment as described above can operate in two modes. For example, the reliquefaction unit 30 can operate in a reliquefaction mode in which the boil-off gas liquefied in the condenser 32 is delivered to the liquid tank 10 via the intercooler 34, and in a fuel supply mode in which the boil-off gas is delivered from the upstream or downstream of the condenser 32 to the propulsion engine E side.

[0124] Specifically, in the reliquefaction mode, the boil-off gas compressed in multiple stages is liquefied through the condenser 32 and then transported to the intercooler 34 through the gas-liquid separator 33. At this time, the boil-off gas is branched from the upstream of the intercooler 34, a part of the boil-off gas can be filled into the inside of the intercooler 34, and the rest of the boil-off gas will pass through the inside of the intercooler 34 to perform heat exchange only without mixing with the boil-off gas filled in the inside of the intercooler 34. The boil-off gas passing through the intercooler 34 can be cooled or supercooled to stably maintain a liquid state, and then can be returned to the liquid tank 10.

[0125] In contrast, in the fuel supply mode, the boil-off gas compressed in multiple stages may be delivered from upstream of the condenser 32 to the fuel tank 12 , or the boil-off gas compressed in multiple stages and condensed may be delivered to the fuel tank 12 and then delivered to the propulsion engine E through the high-pressure pump 22 .

[0126] The fuel supply mode can operate when the liquefied evaporated gas is not suitable to return to the liquid 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 meet the required flow rate of the propulsion engine E.

[0127] For example, when propane and butane are stored in the liquid tank 10, if a problem occurs in the reliquefaction device for processing butane and the device stops operating, butane can be liquefied using another reliquefaction device for processing propane. At this time, the propane remaining in the reliquefaction device for processing propane may be mixed with butane, so a fuel supply mode in which the liquefied butane is delivered to the fuel tank 12 instead of the liquid tank 10 can be performed.

[0128] In addition, in various cases where delivery to the fuel tank 12 is more preferred than delivery to the liquid tank 10, the operation may be performed in the fuel supply mode instead of the reliquefaction mode. In addition, as described above, the operation may be performed in a combination mode of the reliquefaction mode and the fuel supply mode.

[0129] The fuel recovery unit 40 recovers the liquefied gas discharged from the propulsion engine E. The fuel recovery unit 40 can recover the liquefied gas to the upstream of the high-pressure pump 22. For this purpose, the liquefied gas supply line L20 from the propulsion engine E to the upstream of the high-pressure pump 22 is provided with a liquefied gas recovery line L30.

[0130] Unlike commercial engines (ME-GI, XDF, etc.) that receive and consume gaseous LNG, the propulsion engine E (ME-LGI, etc.) in the present invention has a structure that receives and consumes liquid LPG, etc. and discharges excess liquid fuel.

[0131] This is because, unlike in the case of gaseous state, in the case of liquid state, it is not easy to finely control the fuel supply amount, so excess fuel is generated as the propulsion engine E receives a sufficient amount of liquid fuel.

[0132] However, the liquefied gas recovered from the propulsion engine E is the liquefied gas that passes through the interior of the propulsion engine E rather than the liquefied gas before flowing into the propulsion engine E. While having a temperature / pressure state corresponding to the required pressure of the propulsion engine E (for example, around 45 bar, above 50 degrees Celsius), the lubricating oil used in the propulsion engine E may be mixed into the interior of the liquefied gas.

[0133] That is, the excess liquefied gas recovered from the propulsion engine E is mixed with lubricating oil, and therefore it is preferable not to transfer the recovered liquefied gas to the liquid tank 10 to prevent cargo contamination.

[0134] Therefore, the liquefied gas recovery line L30 connected to the propulsion engine E for recovering excess liquefied gas can transport the excess liquefied gas returned from the propulsion engine E to the high-pressure pump 22 instead of the liquid tank 10, so that it can flow back into the propulsion engine E.

[0135] That is, the liquefied gas recovery line L30 transports excess liquid liquefied gas that is mixed with the lubricating oil used in the propulsion engine E when passing through the interior of the propulsion engine E to the liquefied gas supply line L20 upstream of the high-pressure pump 22, so that it can flow back into the propulsion engine E, thereby preventing the liquefied gas in the liquid tank 10 from being contaminated by the lubricating oil.

[0136] Such a fuel recovery unit 40 may include a pressure reducing valve provided in the liquefied gas recovery line L30 , a cooler 41 , and may further include a collection tank 42 and a separation drum 43 .

[0137] The pressure reducing valve reduces the pressure of the excess liquid liquefied gas mixed with the lubricating oil exhausted from the propulsion engine E. The pressure reducing valve may be a Joule-Thompson valve, and may be arranged to constitute a fuel supply train (FVT) together with the fuel supply valve.

[0138] This pressure reducing valve can reduce the pressure of the high-pressure (about 30 to 50 bar) liquefied gas recovered from the propulsion engine E to correspond to the suction pressure of the high-pressure pump 22.

[0139] The cooler 41 cools the liquefied gas decompressed by the pressure reducing valve in the liquefied gas recovery line L30 so that it flows into the high-pressure pump 22 in a liquid state. The cooler 41 can use a variety of refrigerants without limitation, and can cool the liquefied gas to below the boiling point of the decompressed liquefied gas. As an example, the cooler 41 can use seawater as a refrigerant, in which case the heat exchanger 23 and the cooler 41 can be connected integrally through a refrigerant supply unit.

[0140] The cooling of the cooler 41 may be performed by mixing with the liquefied gas sent from the fuel tank 12 to the high-pressure pump 22, so the cooler 41 may be controlled to cool the liquefied gas to a temperature slightly higher than the boiling point of the decompressed liquefied gas.

[0141] The liquid (or close to liquid) liquefied gas cooled by the cooler 41 can be mixed into the upstream of the high-pressure pump 22 from the liquefied gas supply line L20 through the liquefied gas recovery line L30, and a mixer (not shown) can be provided at the connection point between the liquefied gas recovery line L30 and the liquefied gas supply line L20.

[0142] The liquefied gas circulation line L22 described above 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 of the liquefied gas recovery line L30 so as to be connected between the propulsion engine E downstream of the high-pressure pump 22 and the cooler 41.

[0143] This is because the liquefied gas is pumped and heated by the operation of the high-pressure pump 22. If the heated liquefied gas continues to circulate, the temperature of the high-pressure pump 22 itself may increase unnecessarily. Therefore, in order to suppress this situation, the present embodiment can use the cooler 41 to limit the degree of heat generated by the high-pressure pump 22 when the liquefied gas circulates through the liquefied gas circulation line L22 to within a preset value.

[0144] Therefore, the high-pressure pump 22 can continuously pump liquefied gas at a flow rate exceeding the minimum required flow rate, and the excess liquefied gas recovered through the liquefied gas circulation line L22 circulates to the high-pressure pump 22 via the cooler 41, thereby preventing the high-pressure pump 22 from overheating.

[0145] The collection tank 42 collects a portion of the liquefied gas returned from the propulsion engine E. The collection tank 42 may be provided to branch from a liquefied gas recovery line L30 connected to a liquefied gas supply line L20 upstream of the high-pressure pump 22 from the propulsion engine E, and a liquefied gas collection line L31 may extend from the liquefied gas recovery line L30 to the collection tank 42.

[0146] At this time, the liquefied gas collection line L31 may extend from between the pressure reducing valve of the liquefied gas recovery line L30 and the cooler 41 and be connected to the collection tank 42, and further, may be joined 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 may be partially provided in parallel with the liquefied gas recovery line L30, and may be provided with the collection tank 42.

[0147] The collecting tank 42 performs gas-liquid separation on the recovered liquefied gas. When the gaseous liquefied gas flows into the high-pressure pump 22, cavitation problems may occur. Therefore, in the present invention, the liquefied gas flowing along the liquefied gas recovery line L30 can be separated from the gas and liquid while passing through the collecting tank 42 as needed, thereby preventing the gaseous liquefied gas from flowing into the high-pressure pump 22.

[0148] That is, the collection tank 42 can collect the liquefied gas in the liquefied gas recovery line L30 and deliver only the liquefied gas in liquid form to the high-pressure pump 22 , thereby ensuring that the high-pressure pump 22 operates stably.

[0149] The separation drum 43 can receive the liquefied gas recovered from the propulsion engine E from the collection tank 42 and filter the impurities (lubricating oil, etc.) contained in the liquefied gas. A liquefied gas processing line L32 can be connected from the collection tank 42 to the separation drum 43. In addition to the gaseous liquefied gas separated from the collection tank 42, the liquefied gas processing line L32 can also transport the liquid liquefied gas transported from the collection tank 42 to the liquefied gas recovery line L30 to the separation drum 43.

[0150] The separation drum 43 separates the lubricating oil from the liquefied gas flowing into the inside thereof. Specifically, the separation drum 43 discharges the liquefied gas in a gaseous state and discharges the lubricating oil in a liquid state. That is, the separation drum 43 realizes a gas-liquid separation function similar to the collection tank 42.

[0151] However, the separation drum 43 may use a heating unit such as tracing to promote the gasification of the liquefied gas. The tracing may be a configuration using a medium such as steam or seawater as a heat source or utilizing electrical heating.

[0152] The separation drum 43 can heat the liquefied gas mixed with the lubricating oil by a heating unit, discharge the liquefied gas through a vent mast (not shown) or the like, and discharge the lubricating oil from the bottom for treatment (reuse).

[0153] For reference, a ventilation mast (not shown) discharges to the atmosphere substances that need to be discharged to the outside from between the liquid tank 10 and the propulsion engine E. The ventilation mast is provided on the deck of the ship and has a predetermined height so as to protect the crew on the deck.

[0154] The ventilation mast may be connected from the collection tank 42 or the separation drum 43, and may also be connected to the boil-off gas exhaust line L10, the liquefied gas supply line L20, the fuel tank 12, etc. Thus, the ventilation mast protects the system by achieving external discharge in normal operation or in an emergency such as termination of operation of the propulsion engine E.

[0155] In addition, the ventilation mast can discharge the purge gas to the outside when the boil-off gas exhaust line L10, the liquefied gas supply line L20, etc. are purged. At this time, the purge gas can be nitrogen or an inert gas.

[0156] As described above, in the present embodiment, the evaporated gas generated in the liquid tank 10 is reliquefied and then transported to the fuel tank 12 to be supplied to the propulsion engine E. This can solve the problem that the liquefied gas components may be contaminated when different types of liquefied gases are returned to the liquid tank 10 after reliquefaction, and can reduce the number of settings or the number of operations of the condenser 32.

[0157] Figure 2 4 is a conceptual diagram of a gas processing system according to a second embodiment of the present invention.

[0158] Hereinafter, the present embodiment will be mainly described with the differences between the present embodiment and the above-mentioned embodiment, and the omitted parts will be replaced with the above-mentioned contents. It should be noted that the same is true for the following embodiments.

[0159] Reference Figure 2 In the gas processing system 1 of the second embodiment of the present invention, the reliquefaction unit 30 liquefies the boil-off gas and delivers it to the high-pressure pump 22. Specifically, the reliquefaction device can deliver the liquefied boil-off gas to the fuel tank 12, or can deliver it to the liquefied gas supply line L20 between the fuel tank 12 and the high-pressure pump 22, as in the previous embodiment.

[0160] For this purpose, as a line for conveying the liquid phase separated in the gas-liquid separator 33, in addition to the boil-off gas return line L11 and the boil-off gas delivery line L12, a boil-off gas supply line L13 may be provided. One end of the boil-off gas supply line L13 may extend from the gas-liquid separator 33 or the boil-off gas delivery 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.

[0161] The point where the boil-off gas delivery line L12 is connected to the liquefied gas supply line L20 may be upstream of or 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 excess liquefied gas recovered through the liquefied gas recovery line L30, the high-pressure pump 22 may pressurize the liquid boil-off gas delivered by the reliquefaction device and supply it to the propulsion engine E.

[0162] When the boil-off gas liquefied by the condenser 32 bypasses the fuel tank 12 and merges with the liquefied gas recovered from the liquefied gas recovery line L30 through the boil-off gas supply line L13 and is then supplied to the high-pressure pump 22 , the high-pressure pump 22 can still prevent the inflow of gas.

[0163] Specifically, in this embodiment, the inflow pressure of the high-pressure pump 22 and the boil-off gas pressure (which may be the internal pressure of the gas-liquid separator 33) downstream of the condenser 32 are controlled to be the same, so that the boiling point of the liquefied gas flowing on the liquefied gas supply line L20 upstream of the high-pressure pump 22 and the boiling point of the boil-off gas flowing on the boil-off gas supply line L13 can be controlled to be the same. That is, no additional pressurizing / compressing device is provided on the boil-off gas supply line L13 between the gas-liquid separator 33 and the high-pressure pump 22.

[0164] 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 on the liquefied gas recovery line L30 is also the same as the boiling point of the boil-off gas on the boil-off gas supply line L13.

[0165] At this time, the condenser 32 of the reliquefaction 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 refrigerant having the same condition (temperature), so that the boil-off gas / liquid liquefied gas is cooled to approximately the same temperature.

[0166] Therefore, in this embodiment, the cooler 41 of the fuel recovery section 40 cools the liquid liquefied gas having a first pressure with the first refrigerant to prevent vaporization at the inflow end of the high-pressure pump 22, and the condenser 32 of the reliquefaction section 30 will also cool the evaporated gas having a first pressure with the first refrigerant, so that the cooler 41 and the condenser 32 can be controlled in conjunction with each other to prevent the gas from flowing into the high-pressure pump 22.

[0167] That is, in this embodiment, even if the inflow pressure of the high-pressure pump 22 is low, the condenser 32 uses the same refrigerant as the cooler 41 to condense the evaporated gas at the same pressure as the liquid liquefied gas recovered from the fuel recovery section 40. Therefore, even if the reliquefaction device bypasses the fuel tank 12 and directly delivers the evaporated gas to the high-pressure pump 22, the operating stability of the high-pressure pump 22 can be ensured.

[0168] Therefore, when the reliquefaction device of this embodiment operates in the fuel supply mode, in addition to transporting the liquid phase separated in the gas-liquid separator 33 to the fuel tank 12, it can also be transported 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 evaporated gas delivery line L12 or the evaporated gas supply line L13 can be controlled according to multiple variables such as the amount of evaporated gas discharged from the liquid tank 10, the load of the propulsion engine E, the internal pressure of the fuel tank 12, etc.

[0169] In addition, the reliquefaction apparatus of this embodiment includes a bypass line L14. The bypass line L14 allows at least a portion of the boil-off gas to bypass the condenser 32 and be supplied to the gas-liquid separator 33. The bypass line L14 may be provided with a bypass valve 36 for adjusting the flow.

[0170] When the temperature of the refrigerant used in the condenser 32 is low, the boil-off gas may be overcooled by the refrigerant. When the overcooled liquid boil-off gas flows into the gas-liquid separator 33 downstream of the condenser 32, the internal pressure of the gas-liquid separator 33 may drop.

[0171] That is, the temperature of the refrigerant in the condenser 32 may determine the degree of cooling of the boil-off gas, which will determine the internal pressure in the gas-liquid separator 33. The internal pressure of the gas-liquid separator 33 may be the pressure of the boil-off gas delivered to the high-pressure pump 22 through the boil-off gas supply line L13, and if the internal pressure of the gas-liquid separator 33 is low, the boiling point of the boil-off gas may be lowered and vaporized in the high-pressure pump 22.

[0172] Therefore, the temperature of the refrigerant in the condenser 32 may cause a gasification problem at the inlet end of the high-pressure pump 22. Therefore, in this embodiment, it is possible to control the pressure of the gas-liquid separator 33 to increase according to the refrigerant temperature.

[0173] To this end, the bypass line L14 can allow at least a portion of the evaporated gas to bypass the condenser 32 and be supplied to the gas-liquid separator 33 by opening the bypass valve 36 to cope with the pressure fluctuation of the evaporated gas delivered from the gas-liquid separator 33 to the high-pressure pump 22 according to the temperature of the refrigerant.

[0174] If the high-temperature gaseous evaporation gas bypassing the condenser 32 flows into the gas-liquid separator 33, the internal pressure of the gas-liquid separator 33 will increase, thereby increasing the pressure of the liquid evaporation gas transported from the gas-liquid separator 33 to the liquefied gas supply line L20 through the evaporation gas supply line L13 and increasing the boiling point.

[0175] Therefore, in this embodiment, by adjusting the control of whether to bypass the condenser 32 based on the refrigerant temperature as a variable, the liquid boil-off gas transported from the reliquefaction device to the high-pressure pump 22 is prevented from being re-gasified, thereby preventing cavitation in the high-pressure pump 22 in advance.

[0176] In addition, since 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, when the condenser 32 and the cooler 41 are operated using the same refrigerant, only the liquid phase can flow stably into the inlet end of the high-pressure pump 22.

[0177] As described above, if the temperature of the refrigerant used in the condenser 32 is low temperature, the liquid evaporated gas transported from the reliquefaction device to the high-pressure pump 22 may be vaporized and flow into the high-pressure pump 22 due to its low pressure. However, the present embodiment can effectively solve the above-mentioned problem by applying control that allows a portion of the evaporated gas to bypass the condenser 32 according to the temperature of the refrigerant.

[0178] Figure 3 4 is a conceptual diagram of a gas processing system according to a third embodiment of the present invention.

[0179] Reference Figure 3 In the gas processing system 1 of the third embodiment of the present invention, compared with the aforementioned second embodiment, the fuel tank 12 can be omitted, and the liquefied gas transmission line L21 or the boil-off gas transmission line L12 and the like can also be omitted.

[0180] In this case, the liquefied gas supply line L20 may be directly connected from the liquid 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.

[0181] As shown in the figure, the low-pressure pump 21 may be arranged downstream of the transfer pump 11 in the liquefied gas supply line L20 , but the low-pressure pump 21 may be omitted if the discharge pressure of the transfer pump 11 is set to correspond to the inflow pressure of the high-pressure pump 22 .

[0182] In addition, in this embodiment, the reliquefaction device can deliver the liquefied boil-off gas to the liquefied gas supply line L20 between the liquid tank 10 and the high-pressure pump 22. At this time, the reliquefaction device can deliver the liquid phase separated by the gas-liquid separator 33 to the liquefied gas supply line L20 upstream of the high-pressure pump 22 in the fuel supply mode, so as to supply it to the propulsion engine E.

[0183] In addition, similar to the aforementioned embodiment, the reliquefaction device can liquefy the boil-off gas and deliver it to the high-pressure pump 22, and depending on the temperature of the refrigerant, a portion of the boil-off gas can bypass the condenser 32 and be delivered to the liquefied gas supply line L20 upstream of the high-pressure pump 22 through the gas-liquid separator 33.

[0184] Figure 4 4 is a conceptual diagram of a gas processing system according to a fourth embodiment of the present invention.

[0185] Reference Figure 4In the gas processing system 1 of the fourth embodiment of the present invention, compared with the aforementioned second embodiment, the boil-off gas supply line L13 is omitted, and the recovery point of the liquefied gas is set to the fuel tank 12 .

[0186] In this embodiment, the reliquefaction device can deliver the liquefied boil-off gas to the fuel tank 12. As described above, this can be achieved through the boil-off gas delivery line L12. That is, the reliquefaction device can deliver the liquid phase separated in the gas-liquid separator 33 to the fuel tank 12 in the fuel supply mode, so as to supply it to the propulsion engine E.

[0187] However, in the present 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 may transport the excess liquefied gas mixed in the lubricating oil used in the propulsion engine E to the fuel tank 12. At this time, the liquefied gas flowing into the fuel tank 12 may flow back into the propulsion engine E through the low-pressure pump 21 and the high-pressure pump 22.

[0188] The fuel tank 12 of this embodiment is a structure that directly recovers the excess liquefied gas into the interior thereof, and the internal pressure can be set higher than that of the aforementioned 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 gasify. 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 can be omitted.

[0189] Similar to the second and third embodiments, this embodiment can also control the flow of the liquid boil-off gas according to the temperature of the refrigerant used in the condenser 32. Specifically, in this embodiment, the reliquefaction device can allow at least a portion of the boil-off gas to bypass the condenser 32 and be supplied to the fuel tank 12 to cope with the pressure change of the boil-off gas delivered to the fuel tank 12 according to the temperature of the refrigerant.

[0190] In the present embodiment, the liquid boil-off gas is delivered 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 temperature of the refrigerant in the condenser 32 will affect the internal pressure of the fuel tank 12, which may affect the inflow pressure of the low-pressure pump 21, and this may 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 may directly affect the inflow pressure of the high-pressure pump 22.

[0191] Therefore, the reliquefaction device of this embodiment can make a part of the boil-off gas bypass the condenser 32 and supply it to the fuel tank 12 via the gas-liquid separator 33, so as to cope with the pressure fluctuation of the boil-off gas delivered from the gas-liquid separator 33 to the fuel tank 12 according to the temperature of the refrigerant. That is, in this embodiment, the internal pressure of the gas-liquid separator 33 and the internal pressure of the fuel tank 12 can be adjusted at one time by adjusting the bypass of the boil-off gas.

[0192] Alternatively, in the present embodiment, the liquid boil-off gas liquefied in the condenser 32 is delivered to the high-pressure pump 22 via the fuel tank 12 , so that the fuel tank 12 can realize the gas-liquid separation function, and the gas-liquid separator 33 can be omitted in the reliquefaction device.

[0193] Figure 5 is a conceptual diagram of a gas processing system according to a fifth embodiment of the present invention.

[0194] Reference Figure 5 In the gas processing system 1 of the fifth embodiment of the present invention, the connection point of the boil-off gas supply line L13 may be set differently compared to the second embodiment.

[0195] The boil-off gas supply line L13 of this embodiment can transport the boil-off 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 boil-off gas supply line L13 can be connected between the condenser 32 and the gas-liquid separator 33 of the reliquefaction device, and the other end can be connected to the upstream of the high-pressure pump 22 of the liquefied gas supply line L20.

[0196] This evaporation gas supply line L13 is provided to cope with the change of the internal pressure of the gas-liquid separator 33 according to the temperature of the refrigerant. Specifically, when the temperature of the refrigerant is low and lower than the reference value, the evaporation gas supply line L13 can directly connect the upstream of the high-pressure pump 22 with the upstream of the gas-liquid separator 33 to prevent the evaporation gas from being under-cooled when the condenser 32 flows into the high-pressure pump 22 through the gas-liquid separator 33.

[0197] In this case, the compressor 31 of the reliquefaction device is in a state where the condenser 32 and the high-pressure pump 22 are sequentially arranged downstream thereof according to the flow of boil-off gas, so that the pressure at the inflow end of the high-pressure pump 22 matches the pressure at the discharge end of the compressor 31. Therefore, the compressor 31 receives the inflow pressure of the high-pressure pump 22 (the pressure of the liquid liquefied gas recovered through the liquefied gas recovery line L30) as a resistance, and the operation is controlled, and the discharge pressure of the compressor 31 may be increased.

[0198] That is, in this embodiment, if the temperature of the refrigerant used in the condenser 32 is too low, the evaporative gas supply line L13 is used to directly connect the downstream of the condenser 32 and the upstream of the high-pressure pump 22, so that the discharge end of the compressor 31 is subjected to resistance due to the inflow pressure of the high-pressure pump 22, so as to control the discharge pressure of the compressor 31 to correspond to the inflow pressure of the high-pressure pump 22.

[0199] 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 connected to have the same pressure, so that the discharge pressure of the compressor 31 can correspond to the inflow pressure of the high-pressure pump 22.

[0200] As described above, in this embodiment, in order to cope with the situation where the pressure of the liquid evaporating gas becomes inappropriate due to the excessively low temperature of the refrigerant used in the condenser 32, the downstream of the compressor 31 is connected to the upstream of the high-pressure pump 22, so that the vaporization in the high-pressure pump 22 can be effectively prevented by making the discharge pressure of the compressor 31 correspond to the inflow pressure of the high-pressure pump 22.

[0201] Figure 6 is a conceptual diagram of a gas processing system according to a sixth embodiment of the present invention.

[0202] Reference Figure 6 In the gas processing system 1 of the sixth embodiment of the present invention, compared with the fifth embodiment, the fuel tank 12 can be omitted, and the liquefied gas transmission line L21 or the boil-off gas transmission line L12 can also be omitted.

[0203] In this case, the liquefied gas supply line L20 can be directly connected from the liquid 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. At this time, as described in the third embodiment above, the low-pressure pump 21 can be omitted.

[0204] In this embodiment, the reliquefaction device can deliver the liquefied boil-off gas to the liquefied gas supply line L20 between the liquid tank 10 and the high-pressure pump 22. At this time, the reliquefaction device can deliver the liquid phase separated by the gas-liquid separator 33 to the liquefied gas supply line L20 upstream of the high-pressure pump 22 in the fuel supply mode, so as to supply it to the propulsion engine E.

[0205] In addition, similar to the aforementioned embodiment, the reliquefaction device liquefies the evaporated gas and delivers it to the high-pressure pump 22, and connects the downstream of the condenser 32 with the upstream of the high-pressure pump 22 according to the temperature of the refrigerant, thereby making the discharge pressure of the compressor 31 correspond to the inflow pressure of the high-pressure pump 22.

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

[0207] Reference Figure 7 In the gas processing system 1 according to the seventh embodiment of the present invention, the detailed configuration of the reliquefaction device is different from that of the previous embodiments, and the configuration other than that may include at least any one of the configurations of the previous embodiments.

[0208] The reliquefaction device of this embodiment includes a compressor 31, a condenser 32, a gas-liquid separator 33, an aftercooler 35, and a boil-off gas heat exchanger 37. The compressor 31, the condenser 32, and the gas-liquid separator 33 are as described above, and thus detailed description thereof will be omitted.

[0209] The boil-off gas heat exchanger 37 exchanges heat between the boil-off gas delivered from the liquid tank 10 to the compressor 31 and the boil-off gas liquefied in the condenser 32. Specifically, the boil-off gas heat exchanger 37 may be a dual-stream structure having a stream of the boil-off gas delivered from the liquid tank 10 to the compressor 31 and a stream of the boil-off gas delivered from the gas-liquid separator 33 to the liquid tank 10.

[0210] As an example, the boil-off gas heat exchanger 37 may be provided on the boil-off gas return line L11 in a manner having one flow parallel to the boil-off gas discharge line L10 and another flow parallel to the boil-off gas return line L11, and may be provided to replace the above-described intercooler 34. Of course, the boil-off gas heat exchanger 37 may be added to the above-described embodiment having the intercooler 34.

[0211] The boil-off gas liquefied in the condenser 32 is compressed by the compressor 31, so although it is in a liquid state, its temperature may be higher than the boiling point at atmospheric pressure. On the contrary, the boil-off gas discharged from the liquid tank 10 may have a pressure at the atmospheric pressure level and a temperature close to the boiling point.

[0212] Therefore, the evaporation gas heat exchanger 37 can cool by exchanging heat between the evaporation gas delivered from the gas-liquid separator 33 and the low-temperature evaporation gas discharged from the liquid tank 10. At this time, the pressure of the evaporation gas as the cooling object and the evaporation gas as the cooling subject in the evaporation gas heat exchanger 37 can be different, and the pressure difference can form a pressure difference between the internal pressure in the liquid tank 10 and the internal pressure of the gas-liquid separator 33.

[0213] A pressure reducing valve (not shown) may be provided at at least one point upstream and downstream of the BOG heat exchanger 37 on the BOG return line L11 , which achieves additional cooling by reducing the pressure of the BOG compressed in the compressor 31 .

[0214] As described in the aforementioned first embodiment, the reliquefaction device including such a boil-off gas heat exchanger 37 can operate in a fuel supply mode or a reliquefaction mode. That is, the reliquefaction device can operate in a reliquefaction mode in which the liquid phase separated in the gas-liquid separator 33 is transferred to the liquid tank 10 via the boil-off gas heat exchanger 37 provided in the boil-off gas return line L11, and / or in a fuel supply mode in which the liquid phase separated in the gas-liquid separator 33 is transferred to the fuel tank 12 via the boil-off gas transfer line L12 and supplied to the propulsion engine E.

[0215] As described above, in this embodiment, the boil-off gas heat exchanger 37 is used instead of the intercooler 34, so that the structure of the reliquefaction device can be simplified, and the boil-off gas circulation through the intercooler 34 is omitted, so that the reliquefaction capacity of the reliquefaction device can be increased.

[0216] Of course, in addition to the embodiments described above, the present invention also includes embodiments that combine at least one of the above embodiments with embodiments of the prior art and embodiments that combine at least two of the above embodiments.

[0217] The present invention has been described in detail above through specific embodiments. However, this is for the purpose of specifically illustrating the present invention. The present invention is not limited thereto. It is obvious that a person skilled in the art can modify or improve the present invention within the technical concept of the present invention.

[0218] Simple deformation or modification of the present invention all belong to the scope of the present invention, and the specific protection scope of the present invention is clarified by the claims of the present invention.

Claims

1. A gas processing system, the gas processing system is a system for processing liquefied gas including heavy hydrocarbons or ammonia, in, include: a fuel tank storing liquefied gas as fuel to be supplied to the ship's propulsion engines; a liquefied gas supply line, which supplies the liquefied gas from the fuel tank to the propulsion engine in a liquid state and is provided with a high-pressure pump; a reliquefaction device for liquefying boil-off gas generated in two or more tanks storing liquefied gas; and a liquefied gas recovery line for recovering the liquid liquefied gas exhausted from the propulsion engine to the upstream of the high-pressure pump; The reliquefaction device delivers liquefied boil-off gas to the fuel tank to be supplied to the propulsion engine via the high-pressure pump; The gas processing system further comprises: a boil-off gas delivery line for delivering boil-off gas liquefied in the reliquefaction device to the fuel tank; and A boil-off gas supply line has one end extending from the reliquefaction device or the boil-off gas delivery line and the other end connected to the upstream of the high-pressure pump on the liquefied gas supply line.

2. The gas processing 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 discharged from the propulsion engine and mixed with lubricating oil. The liquefied gas recovery line transports the excess liquid liquefied gas mixed with the lubricating oil used in the propulsion engine when passing through the interior of the propulsion engine to the liquefied gas supply line upstream of the high-pressure pump so that it can flow back into the propulsion engine.

3. The gas treatment system according to claim 2, wherein: The liquefied gas recovery line is provided with a cooler that cools the liquefied gas decompressed by the decompression valve and flows the liquefied gas into the high-pressure pump in a liquid state.

4. The gas processing system according to claim 1, wherein: The reliquefaction device comprises: A compressor for performing multi-stage compression on the boil-off gas discharged from the liquid tank; a condenser that cools the compressed boil-off gas with a refrigerant to liquefy it; and The intercooler exchanges heat between a portion of the boil-off gas liquefied in the condenser and the rest of the gas, and delivers the boil-off gas generated by the heat exchange to the compressor.

5. The gas processing system according to claim 4, wherein: The reliquefaction device further includes a gas-liquid separator for performing gas-liquid separation on the boil-off gas liquefied in the condenser. The reliquefaction device operates in at least one of a reliquefaction mode and a fuel supply mode. In the reliquefaction mode, the liquid phase separated in the gas-liquid separator is transported to the liquid tank via the intercooler. In the fuel supply mode, the liquid phase separated in the gas-liquid separator is transported to the fuel tank to be supplied to the propulsion engine.

6. The gas processing system of claim 1, wherein: The reliquefaction device comprises: A compressor for performing multi-stage compression on the boil-off gas discharged from the liquid tank; a condenser to cool the compressed boil-off gas to liquefy it; and The boil-off gas heat exchanger exchanges heat between the boil-off gas sent from the liquid tank to the compressor and the boil-off gas liquefied in the condenser.

7. The gas processing system according to claim 6, wherein: The reliquefaction device further includes a gas-liquid separator for performing gas-liquid separation on the boil-off gas liquefied in the condenser. The reliquefaction device operates in at least one of a reliquefaction mode and a fuel supply mode. In the reliquefaction mode, the liquid phase separated in the gas-liquid separator is transported to the liquid tank via the evaporative gas heat exchanger. In the fuel supply mode, the liquid phase separated in the gas-liquid separator is transported to the fuel tank to be supplied to the propulsion engine.

8. A gas processing system, the gas processing system being a system for processing liquefied gas including heavy hydrocarbons or ammonia, in, include: a liquefied gas supply line, which supplies the liquefied gas stored in the liquid tank to the propulsion engine in a liquid state and is provided with a high-pressure pump; a reliquefaction device for liquefying the boil-off gas generated in the liquid tank and transferring the liquefied gas to the high-pressure pump; and a liquefied gas recovery line for recovering the liquid liquefied gas exhausted from the propulsion engine to the upstream of the high-pressure pump; The reliquefaction device comprises: a condenser for cooling the boil-off gas with a refrigerant to liquefy it; and a buffer for temporarily storing boil-off gas liquefied in the condenser; The reliquefaction device has a bypass line for supplying at least a portion of the boil-off gas to the buffer bypassing the condenser, so as to cope with the pressure of the boil-off gas delivered from the buffer to the high-pressure pump changing according to the temperature of the refrigerant; The gas processing system further includes a boil-off gas supply line that delivers boil-off gas liquefied in the reliquefaction device to an upstream portion of the high-pressure pump.

9. The gas processing system of claim 8, wherein: The liquefied gas recovery line is provided with a pressure reducing valve for reducing the pressure of excess liquid liquefied gas discharged from the propulsion engine and mixed with lubricating oil. The liquefied gas recovery line transports the excess liquid liquefied gas mixed with the lubricating oil used in the propulsion engine when passing through the interior of the propulsion engine to the liquefied gas supply line upstream of the high-pressure pump so that it can flow back into the propulsion engine.

10. The gas processing system of claim 9, wherein: The liquefied gas recovery line is provided with a cooler that cools the liquefied gas decompressed by the decompression valve and flows the liquefied gas into the high-pressure pump in a liquid state.

11. The gas processing system of claim 8, wherein: The buffer is a gas-liquid separator that separates the boil-off gas liquefied in the condenser into gas and liquid.

12. The gas processing system of claim 11, wherein: The reliquefaction device transfers the liquefied boil-off gas to the liquefied gas supply line between the liquid tank and the high-pressure pump.

13. The gas processing system of claim 12, wherein: The reliquefaction device comprises: A compressor for performing multi-stage compression on the boil-off gas discharged from the liquid tank; and The intercooler exchanges heat between a portion of the boil-off gas liquefied in the condenser and the rest of the gas, and delivers the boil-off gas generated by the heat exchange to the compressor.

14. The gas processing system of claim 13, wherein: The reliquefaction device operates in at least one of a reliquefaction mode and a fuel supply mode. In the reliquefaction mode, the liquid phase separated in the gas-liquid separator is transported to the liquid tank via the intercooler. In the fuel supply mode, the liquid phase separated in the gas-liquid separator is transported to the liquefied gas supply line upstream of the high-pressure pump to be supplied to the propulsion engine.

15. A ship, characterized in that: The ship is a liquefied gas tanker having the gas processing system according to any one of claims 1 to 14.

Images