Vessels containing gas processing systems

Abstract

The present invention relates to a ship, and the ship includes a liquefied gas storage tank for storing liquefied gas, a main compressor for compressing evaporated gas generated in the liquefied gas storage tank and supplying it to a demand destination, a first heat exchanger for recovering cold energy from the evaporated gas supplied from the liquefied gas storage tank to the main compressor, a second heat exchanger for cooling the evaporated gas circulated from the main compressor to the liquefied gas storage tank, and a first liquefied gas supply unit for supplying liquefied gas to the evaporated gas upstream of the main compressor.

Description

[Technical Field]

[0001] The present invention relates to a vessel including a gas processing system. [Background technology]

[0002] A ship is a means of transportation that sails across the ocean carrying large amounts of minerals, crude oil, natural gas, or thousands of containers.It is made of steel and moves by thrust generated by the rotation of a propeller while floating above the waterline due to buoyancy.

[0003] Such vessels generate thrust by driving engines, which typically use gasoline or diesel to move pistons, causing the reciprocating motion of the pistons to rotate a crankshaft, which in turn rotates a shaft connected to the crankshaft and drives a propeller.

[0004] However, when heavy oil such as HFO or MFO is used as a propellant fuel, environmental pollution due to various harmful substances contained in exhaust gas is serious, and regulations on the use of heavy oil as fuel oil are being strengthened, and the costs of complying with such regulations are gradually increasing.

[0005] As a result, technology is being developed to use liquefied gases such as liquefied natural gas and liquefied petroleum gas as ship fuel instead of gasoline or diesel.

[0006] Such liquefied gases are stored in liquid phase in liquefied gas storage tanks, and the volume of liquefied natural gas is reduced to 1 / 600 of its original volume, while the volume of liquefied petroleum gas is reduced to 1 / 260 of its original volume for propane and 1 / 230 of its original volume for butane, resulting in high storage efficiency.

[0007] However, because such liquefied gas is stored at extremely low temperatures below -50 degrees, there are problems such as the generation of evaporated gas due to external heat penetration. Therefore, research and development is being continuously conducted on technologies to stably store and process liquefied gas. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been created to solve the problems of the prior art as described above, and an object of the present invention is to prevent the concentration of load on the refrigerant heat exchanger by cooling the refrigerant using the evaporated gas in consideration of the temperature of the evaporated gas supplied to the main compressor during the process of supplying evaporated gas from a liquefied gas propelled ship to a consumer.

[0009] The objects of the present invention are not limited to those mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0010] A ship according to one aspect of the present invention includes a liquefied gas storage tank for storing liquefied gas, a main compressor for compressing evaporated gas generated in the liquefied gas storage tank and supplying it to a demand destination, a first heat exchanger for recovering cold energy from the evaporated gas supplied from the liquefied gas storage tank to the main compressor, a second heat exchanger for cooling the evaporated gas circulated from the main compressor to the liquefied gas storage tank, and a first liquefied gas supply unit for supplying liquefied gas to the evaporated gas upstream of the main compressor.

[0011] Specifically, the system may further include a second liquefied gas supply unit that supplies liquefied gas to the evaporative gas downstream of the main compressor, and whether or not to operate a pump provided in the liquefied gas storage tank may be determined depending on whether or not the temperature of the evaporative gas supplied upstream of the main compressor is higher than a preset temperature.

[0012] Specifically, the preset temperature can be determined to be between -70°C and -50°C.

[0013] Specifically, a ship according to one aspect of the present invention can operate the pump to supply liquefied gas to the first liquefied gas supply unit when the temperature of the evaporated gas supplied to the upstream stage of the main compressor is higher than a preset temperature.

[0014] Specifically, a portion of the liquefied gas supplied to the first liquefied gas supply unit may be supplied to the second liquefied gas supply unit.

[0015] Specifically, in a ship according to one aspect of the present invention, when the temperature of the evaporated gas supplied to the upstream stage of the main compressor is below a predetermined temperature, the pump is not operated and a portion of the liquefied gas circulating from the second heat exchanger to the liquefied gas storage tank is supplied to the first liquefied gas supply unit.

[0016] Specifically, the first heat exchanger may perform heat exchange between the evaporated gas transferred from the liquefied gas storage tank to the main compressor and the refrigerant discharged from the refrigerant compressor. [Effects of the Invention]

[0017] The ship according to the present invention can supply evaporated gas to a demand destination at an appropriate temperature, and can prevent excessive load from being placed on a specific heat exchanger or a specific compressor.

[0018] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the claims. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing a vessel according to a first embodiment of the present invention; [Figure 2] FIG. 1 shows a vessel according to a second embodiment of the present invention. [Figure 3] FIG. 10 shows a vessel according to a third embodiment of the present invention. [Figure 4] FIG. 10 shows a vessel according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, when a part is said to "include" or "have" a certain component, it means that it can further include other components, not excluding other components, unless otherwise specified.

[0021] In the following, liquefied gas can be used to encompass all gas fuels that are generally stored in a liquid state, such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), ethylene, ammonia, etc. For convenience, it can also be referred to as liquefied gas when it is not in a liquid state due to heating or pressurization. This can also be applied to evaporated gas. Furthermore, for convenience, LNG can be used to encompass not only natural gas (NG) in a liquid state, but also natural gas (NG) in a supercritical state, and evaporated gas can be used to encompass not only evaporated gas in a gaseous state but also liquefied evaporated gas.

[0022] In the following, high pressure (HP), low pressure (LP), high pressure, and low pressure are relative terms and do not indicate absolute values.

[0023] In the following, expressions such as "first" and "second" are intended to indicate that a specific configuration is provided in a plurality of times in the present invention, and each expression may refer to any one of the plurality of configurations. When an expression such as "first" or "second" is not added, the configuration may be a concept that encompasses all of the configurations to which the expression such as "first" or "second" is added.

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0025] FIG. 1 is a diagram showing a ship according to a first embodiment of the present invention.

[0026] Referring to FIG. 1, a ship 1 according to a first embodiment of the present invention may include a liquefied gas storage tank 10, a first heat exchanger 20, a second heat exchanger 30, a main compressor 40, and a demand destination 50.

[0027] The ship 1 may be at anchor or in operation, and when the ship 1 is at anchor, the power generation engine 51 operates, and when the ship 1 is in operation, the power generation engine 51 and the propulsion engine operate.

[0028] When the ship 1 is at anchor, the pressure required for the main compressor 40 may be 6 to 10 bar, and the inlet temperature of the main compressor 40 may be -50°C. When the ship 1 is sailing, the pressure required for the main compressor 40 may be approximately 13 bar, and the inlet temperature of the main compressor 40 may be -70°C. The liquefied gas storage tank 10 stores liquefied gas to be supplied to the demand destination 50. In this case, the liquefied gas storage tank 10 can store liquefied gas in a liquid state and may have the shape of a pressure tank. A plurality of liquefied gas storage tanks 10 may be provided, or a plurality of tanks may be arranged side by side.

[0029] Although the liquefied gas storage tank 10 has an insulated structure, when heat enters the liquefied gas storage tank 10 from the outside, the liquefied gas stored in the liquefied gas storage tank 10 becomes warm and some of it evaporates. This evaporated liquefied gas is stored in the space above the liquid surface of the liquid-phase liquefied gas stored in the liquefied gas storage tank 10 as boil-off gas (BOG).

[0030] The liquefied gas storage tank 10 may be provided with an evaporated gas supply line L1 at the top of the liquefied gas storage tank 10, which can extract evaporated gas stored in the upper space of the liquefied gas storage tank 10 to the outside of the liquefied gas storage tank 10. The evaporated gas may be delivered to a consumer 50 via the evaporated gas supply line L1.

[0031] When the evaporated gas is delivered to the consumer 50 through the evaporated gas supply line L1, the evaporated gas may pass through the main compressor 40. As the evaporated gas passes through the main compressor 40, its pressure increases, and the evaporated gas may reach a desired pressure state at the consumer 50.

[0032] The demand destination 50 may be a main propulsion device and a dual fuel (DF) engine. In this specification, when it is stated that liquefied gas is delivered to the demand destination 50, it may include the liquefied gas being delivered to a power generation engine 51 that generates electricity required on the ship or a gas combustion unit (GCU) 52 that burns evaporated gas.

[0033] The evaporation gas supply line L1 may be provided with a first heat exchanger 20. When the evaporation gas passes through the first heat exchanger 20, the refrigerant in the evaporation gas cold energy recovery line L31 may be cooled, and in this process, the evaporation gas delivered to the consumer 50 may be heated.

[0034] The refrigerant may be branched into an evaporative gas refrigeration recovery line L31 and a first refrigerant line L32 downstream of the refrigerant compressor 60, and a control unit (not shown) can adjust the amount of refrigerant supplied to the first heat exchanger 20 or the second heat exchanger 30 by adjusting the opening degree of the first control valve V1 provided in the evaporative gas refrigeration recovery line L31 and the second control valve V2 provided in the first refrigerant line L32.

[0035] Since a portion of the refrigerant discharged from the refrigerant compressor 60 is supplied to the first heat exchanger 20 via the evaporated gas cold energy recovery line L31, the flow rate of the refrigerant supplied to the second heat exchanger 30 is relatively reduced, thereby reducing the load required to cool the refrigerant in the second heat exchanger 30. That is, since the first heat exchanger 20 cools a portion of the refrigerant discharged from the refrigerant compressor 60, the flow rate of the refrigerant cooled in the second heat exchanger 30 is reduced, thereby reducing the load required to cool the refrigerant in the second heat exchanger 30.

[0036] The evaporative gas supply line L1 is provided with a line that allows the evaporative gas to bypass the first heat exchanger 20, and the evaporative gas can be controlled so that it bypasses the first heat exchanger 20 before the temperature of the evaporative gas reaches a certain level or higher upstream of the main compressor 40.

[0037] The evaporated gas supply line L1 is partially branched off at the downstream side of the main compressor 40, so that the evaporated gas can be circulated to the liquefied gas storage tank 10 via an evaporated gas circulation line L2.

[0038] The evaporated gas circulating to the liquefied gas storage tank 10 downstream of the main compressor 40 can pass through the second heat exchanger 30. The evaporated gas, whose temperature has increased after passing through the main compressor 40, exchanges heat with the refrigerant in the second heat exchanger 30, and is cooled and liquefied in the process.

[0039] The second heat exchanger 30 may include three or more heat exchange units. The second heat exchanger 30 may include a first evaporation gas heat exchange unit 31, a second evaporation gas heat exchange unit 32, and a refrigerant heat exchange unit 33. In this specification, the first evaporation gas heat exchange unit 31, the second evaporation gas heat exchange unit 32, and the refrigerant heat exchange unit 33 provided in the second heat exchanger 30 may refer to regions provided within a single device called the second heat exchanger 30 or flow paths provided in the second heat exchanger 30.

[0040] Specifically, the first evaporative gas heat exchange unit 31 and the second evaporative gas heat exchange unit 32 exchange heat between the refrigerant that has passed through the expander 70 and the evaporative gas circulating from the main compressor 40 to the liquefied gas storage tank 10, and the refrigerant heat exchange unit 33 can exchange heat between the refrigerant that has passed through the expander 70 and the refrigerant that has passed through the refrigerant compressor 60.

[0041] In this case, the refrigerant may be nitrogen, a mixed refrigerant, or the like, and the ship 1 may include various components such as a refrigerant supply unit 80, a boost pump 81, and an expansion tank 82 depending on the components of the refrigerant.

[0042] A gas treatment system provided in a ship 1 according to an embodiment of the present invention will be described with reference to Fig. 1. Referring to Fig. 1, the temperature of a refrigerant increases relatively as it passes through a refrigerant compressor 60. At this time, the refrigerant is transferred to a first heat exchanger 20 or a second heat exchanger 30. In the first heat exchanger 20, the refrigerant exchanges heat with evaporated gas discharged from a liquefied gas storage tank 10, and in the second heat exchanger 30, the refrigerant exchanges heat with refrigerant discharged from an expander 70.

[0043] That is, in the first heat exchanger 20, the evaporated gas discharged from the liquefied gas storage tank 10 and the refrigerant discharged from the refrigerant compressor 60 exchange heat with each other, thereby cooling the refrigerant discharged from the refrigerant compressor 60. Also, in the refrigerant heat exchange unit 33 in the second heat exchanger 30, the refrigerant that has passed through the expander 70 and the refrigerant that has passed through the refrigerant compressor 60 exchange heat with each other, thereby cooling the refrigerant that has passed through the refrigerant compressor 60.

[0044] The higher the temperature of the evaporative gas transmitted to the consumer 50 via the main compressor 40, the larger its volume becomes, and the larger the volume of the evaporative gas becomes, the greater the load on the main compressor 40. Therefore, in order to reduce the volume of the evaporative gas transmitted to the main compressor 40 and the load on the main compressor 40, it is preferable that the temperature of the evaporative gas passing through the main compressor 40 be below -50°C.

[0045] However, the refrigerant is cooled by repeatedly compressing and expanding, and the cold generated in this process is used to cool the evaporative gas. However, since this places a heavy load on the refrigerant cooling, it is necessary to pre-cool the refrigerant using the evaporative gas transmitted to the main compressor 40 in order to reduce the load on the refrigerant cooling.

[0046] Therefore, in the ship 1 according to one embodiment of the present invention, the refrigerant passing through the refrigerant compressor 60 is transferred to the first heat exchanger 20 within a range that maintains the temperature of the evaporative gas passing through the main compressor 40 below -50°C, thereby reducing the load on the main compressor 40 and making maximum use of the cold energy of the evaporative gas to cool the refrigerant.

[0047] As described above, the ship 1 according to one embodiment of the present invention supplies evaporated gas to the demand destination 50 of the ship via the main compressor 40 to meet the required pressure or temperature conditions of the demand destination 50 of the ship, while at the same time, in order to make maximum use of the cold energy of the evaporated gas to re-liquefy the evaporated gas, a line for transmitting the refrigerant to the first heat exchanger 20 and a line for transmitting the refrigerant to the second heat exchanger 30 are branched in the downstream of the refrigerant compressor 60.

[0048] The evaporation gas cold energy recovery line L31 and the first refrigerant line L32 are integrated in the expander line L4, and the refrigerants in the evaporation gas cold energy recovery line L31 and the first refrigerant line L32 are expanded and cooled in the expander 70.

[0049] The refrigerant discharged from the expander 70 is a relatively low-temperature refrigerant, and the line through which the refrigerant flows is branched off at a stage subsequent to the first evaporated gas heat exchange section 31 in the second heat exchanger 30. In the second evaporated gas heat exchange section 32, a portion of the refrigerant exchanges heat with the evaporated gas circulating from the stage subsequent to the main compressor 40 to the liquefied gas storage tank 10, and the remaining portion of the refrigerant can exchange heat with the refrigerant discharged from the refrigerant compressor 60 in the refrigerant heat exchange section 33.

[0050] The amount of refrigerant flowing from the first evaporative gas heat exchange section 31 to the second evaporative gas heat exchange section 32 and the amount of refrigerant flowing from the first evaporative gas heat exchange section 31 to the refrigerant heat exchange section 33 can be adjusted depending on the temperature of the evaporative gas circulating to the liquefied gas storage tank 10 downstream of the main compressor 40, or the temperature of the refrigerant discharged from the refrigerant heat exchange section 33.

[0051] The second evaporative gas heat exchanger 32 can primarily cool the evaporative gas circulating to the liquefied gas storage tank 10. The temperature of the refrigerant transferred from the rear of the first evaporative gas heat exchanger 31 to the second evaporative gas heat exchanger 32 can be lower than the temperature of the front of the expander 70. In the second evaporative gas heat exchanger 32, the refrigerant lowers the temperature of the evaporative gas circulating to the liquefied gas storage tank 10, thereby reducing the load on the first evaporative gas heat exchanger 31 to liquefy the evaporative gas.

[0052] The first evaporative gas heat exchanger 31 can secondarily cool the evaporative gas discharged from the second evaporative gas heat exchanger 32. Since the evaporative gas is primarily cooled in the second evaporative gas heat exchanger 32, the load on the first evaporative gas heat exchanger 31 for liquefying the evaporative gas can be reduced.

[0053] The refrigerant heat exchanger 33 can cool the refrigerant discharged from the refrigerant compressor 60 using the refrigerant discharged from the first evaporative gas heat exchanger 31. Because the second evaporative gas heat exchanger 32 partially cools the evaporative gas in the first evaporative gas heat exchanger 31, the temperature of the refrigerant passing through the first evaporative gas heat exchanger 31 can be relatively low compared to when the second evaporative gas heat exchanger 32 is not provided. Therefore, the temperature of the refrigerant transferred to the refrigerant heat exchanger 33 to cool the refrigerant discharged from the refrigerant compressor 60 can be lowered, thereby increasing the cooling efficiency of the refrigerant heat exchanger 33. Furthermore, the amount of refrigerant transferred to the refrigerant heat exchanger 33 can be reduced, thereby reducing the size of the refrigerant heat exchanger 33 and reducing the cost and space required for system configuration within the ship.

[0054] That is, since the evaporative gas is primarily cooled in the second evaporative gas heat exchanger 32 and then secondarily cooled in the first evaporative gas heat exchanger 31, when the evaporative gas is cooled in the first evaporative gas heat exchanger 31, the temperature drop of the refrigerant in the first evaporative gas heat exchanger 31 can be reduced compared to when the second evaporative gas heat exchanger 32 is not provided. As a result, when the refrigerant discharged from the first evaporative gas heat exchanger 31 is used to cool the refrigerant discharged from the refrigerant compressor 60 in the refrigerant heat exchanger 33, the refrigerant cooling efficiency is improved and the size of the refrigerant heat exchanger 33 can be reduced.

[0055] In order to adjust the temperature of the evaporated gas injected into the main compressor 40, liquefied gas can be supplied to the first liquefied gas supply unit S1 or the second liquefied gas supply unit S2, and details regarding this will be described below with reference to Figure 2.

[0056] In this specification, it has been explained that the gas treatment system is operated based on the standard temperature of the evaporative gas passing through the main compressor 40 being -50°C. However, the standard temperature of the evaporative gas passing through the main compressor 40 is set to -50°C when the power generation engine 51 of the ship 1 is operating and the propulsion engine is not operating, so the pressure required for the main compressor 40 is low and the inlet temperature of the main compressor 40 is high. When the propulsion engine is operating and the pressure required for the main compressor 40 becomes relatively high, the standard temperature of the evaporative gas passing through the main compressor 40 can be even lower, to -70°C.

[0057] As described above, the standard temperature of the evaporative gas passing through the main compressor 40 may vary depending on whether the ship 1 is sailing or not, and the standard temperature of the evaporative gas may be determined to be about -70°C to -50°C.

[0058] FIG. 2 shows a vessel according to a second embodiment of the present invention.

[0059] The following description of the configuration common to the parts described in FIG. 1 can be omitted.

[0060] 2, a ship 1 according to an embodiment of the present invention may include a liquefied gas storage tank 10, a first heat exchanger 20, a second heat exchanger 30, a main compressor 40, and a demand destination 50. The first heat exchanger 20 may perform heat exchange between the evaporated gas in the evaporated gas supply line L1 and the refrigerant in the evaporated gas cold energy recovery line L31. The second heat exchanger 30 may perform heat exchange between the refrigerant in the expander line L4 and the refrigerant in the first refrigerant line L32, and may perform heat exchange between the refrigerant in the expander line L4 and the liquefied gas or evaporated gas in the evaporated gas circulation line L2.

[0061] The first heat exchanger 20 can recover the cold energy of the evaporated gas in the liquefied gas storage tank 10. The refrigerant that passes through the first heat exchanger 20 along the evaporated gas cold energy recovery line L31 is pre-cooled and further cooled while passing through the expander 70.

[0062] The refrigerant that has passed through the expander 70 is supplied to the second heat exchanger 30, and the refrigerant that has passed through the expander 70 can cool the refrigerant in the first refrigerant line L32 and the liquefied gas or evaporated gas in the evaporated gas circulation line L2.

[0063] The liquefied gas or evaporated gas circulating along the evaporated gas circulation line L2 can be completely re-liquefied in the second heat exchanger 30.

[0064] 1, the higher the temperature of the evaporated gas transmitted to the demand destination 50 via the main compressor 40, the larger its volume becomes, and as the volume of the evaporated gas increases, the load on the main compressor 40 increases. Also, the higher the temperature of the evaporated gas passing through the main compressor 40, the less cold energy is recovered in the first heat exchanger 20, and the lower the efficiency of re-liquefaction of the evaporated gas in the second heat exchanger 30. Therefore, in order to reduce the load on the main compressor 40 and increase the re-liquefaction efficiency, it is preferable that the temperature of the evaporated gas passing through the main compressor 40 be below -50°C.

[0065] When the temperature of the evaporated gas passing through the main compressor 40 is -50°C or higher, the liquefied gas in the liquefied gas storage tank 10 can be supplied to the first liquefied gas supply unit S1 using a pump provided in the liquefied gas storage tank 10. When low-temperature liquefied gas is supplied to the first liquefied gas supply unit S1, the evaporated gas in the evaporated gas supply line L1 can be cooled.

[0066] However, liquefied gas storage tank 1 0 The liquefied gas is supplied to the first liquefied gas supply unit S1 from the 0 If the gas is simply circulated to the liquefied gas storage tank 1, 0Heat may be injected into the liquefied gas storage tank 10, reducing the efficiency of re-liquefaction of the evaporated gas. To prevent this, the liquefied gas in the liquefied gas storage tank 10 can be transferred to the second liquefied gas supply unit S2 along a second liquefied gas supply line L6 that branches off from the first liquefied gas supply line L5 and is connected to the second liquefied gas supply unit S2. By supplying liquefied gas to the second liquefied gas supply unit S2, the efficiency of re-liquefaction of the evaporated gas can be increased by approximately 7%.

[0067] At this time, the third control valve V3 can be opened to transmit liquefied gas to the second liquefied gas supply unit S2 depending on the temperature of the evaporated gas supplied to the main compressor 40. By supplying low-temperature liquefied gas to the second liquefied gas supply unit S2, the reliquefaction efficiency in the second heat exchanger 30 can be improved.

[0068] on the other hand , Me When the temperature of the evaporated gas passing through the in-compressor 40 is sufficiently low, it is necessary to supply liquefied gas to the first liquefied gas supply section S1 to lower the temperature of the evaporated gas, but even if a temperature change occurs in the evaporated gas, the amount of evaporated gas generated does not increase suddenly, and the re-liquefaction efficiency does not decrease suddenly.

[0069] rather , Me If the temperature of the evaporated gas passing through the in-compressor 40 is sufficiently low, when a pump is used in the process of supplying the liquefied gas in the liquefied gas storage tank 10, the heat injected into the liquefied gas storage tank 10 can reduce the re-liquefaction efficiency.

[0070] When the liquefied gas in the liquefied gas storage tank 10 is supplied to the first liquefied gas supply unit S1, a pump is operated, which causes problems such as wasting electricity used by the pump and increasing the amount of evaporated gas generated in the liquefied gas storage tank due to heat permeating along the piping through which the liquefied gas flows. If the process of stopping and starting the pump depending on the temperature of the evaporated gas is repeated frequently, electricity is wasted in the preparation process for pump operation, such as cooling down the piping, and the preparation process takes even more time.

[0071] In other words, when the temperature of the evaporated gas is sufficiently low, operating the pump provided in the liquefied gas storage tank 10 to supply liquefied gas to the first liquefied gas supply unit S1 to cool the evaporated gas reduces the reliquefaction efficiency and increases energy consumption during the reliquefaction process.

[0072] Nevertheless, since it is necessary to adjust the temperature of the evaporated gas transferred to the main compressor 40 in order to smoothly supply fuel to the demand destination 50 and reduce the load on the main compressor 40, the evaporated gas can be cooled by transferring the low-temperature liquefied gas that has passed through the second heat exchanger 30 to the first liquefied gas supply unit S1 along the liquefied gas branch line L7 without operating the pump. In this case, the re-liquefaction efficiency can be increased by about 9% compared to supplying liquefied gas by operating the pump.

[0073] In this way, whether or not the pump provided in the liquefied gas storage tank 10 is operated can be determined depending on the temperature of the evaporated gas supplied to the upstream stage of the main compressor 40 .

[0074] The temperature of the evaporated gas upstream of the main compressor 40, which determines whether the pump operates, is preferably -50°C. If the temperature of the evaporated gas is above -50°C, the pump must be operated to quickly cool the evaporated gas. In order to increase the re-liquefaction efficiency, a portion of the liquefied gas transmitted to the first liquefied gas supply unit S1 can be supplied to the second liquefied gas supply unit S2.

[0075] Meanwhile, when the temperature of the evaporated gas is below -50°C, the operation of the pump may be interrupted, and a portion of the low-temperature liquefied gas that has passed through the second heat exchanger 30 may be supplied to the first liquefied gas supply unit S1. In this way, the temperature of the evaporated gas may be adjusted by supplying the low-temperature liquefied gas supplied via the evaporated gas circulation line L2 to the first liquefied gas supply unit S1 without operating the pump provided in the liquefied gas storage tank 10. Here, the temperature of the evaporated gas at which the operation of the pump may be interrupted may be above -90°C and below -50°C.

[0076] When the temperature of the evaporated gas passing through the main compressor 40 is -50°C or higher, the pump operates, and at this time the third control valve V3 is opened to transfer liquefied gas to the second liquefied gas supply unit S2. When the temperature of the evaporated gas passing through the main compressor 40 is lower than -50°C, the pump operation is interrupted, and at this time the fourth control valve V4 is opened to transfer a portion of the liquefied gas circulating from the second heat exchanger to the liquefied gas storage tank to the first liquefied gas supply unit S1.

[0077] In the above description, whether or not the pump operates is determined based on the evaporative gas temperature being -50°C. However, this is the case when the ship 1 is anchored and the propulsion engine is not running. When the propulsion engine is running and the ship 1 is operating, whether or not the pump operates can be determined based on the evaporative gas temperature being -70°C.

[0078] That is, when the ship 1 is operating, if the temperature of the evaporated gas is -70°C or higher, the pump is operated to transfer liquefied gas to the first liquefied gas supply unit S1, and a portion of the liquefied gas transferred to the first liquefied gas supply unit S1 can be supplied to the second liquefied gas supply unit S2.

[0079] Meanwhile, when the ship 1 is sailing, the operation of the pump may be interrupted if the temperature of the evaporated gas is below -70°C, and a portion of the low-temperature liquefied gas that has passed through the second heat exchanger 30 may be supplied to the first liquefied gas supply unit S1. Here, the temperature of the evaporated gas at which the operation of the pump may be interrupted may be above -90°C and below -70°C.

[0080] FIG. 3 shows a vessel according to a third embodiment of the present invention.

[0081] FIG. 4 shows a ship according to a fourth embodiment of the present invention.

[0082] The following description of the configuration common to the parts described in FIGS. 1 and 2 can be omitted.

[0083] Referring to FIG. 3, a ship 1 according to an embodiment of the present invention may include a liquefied gas storage tank 10, a second heat exchanger 30, a main compressor 40, a demand destination 50, and a third heat exchanger 90.

[0084] In the second heat exchanger 30, the lines of the first refrigerant line L32 intersect, so that heat exchange can occur between the refrigerant in the expander line L4 and the refrigerant in the first refrigerant line L32, and heat exchange can occur between the refrigerant in the expander line L4 and the liquefied gas or evaporated gas in the evaporated gas circulation line L2.

[0085] The third heat exchanger 90 can exchange heat between the evaporated gas in the evaporated gas supply line L1 and the liquefied gas or evaporated gas in the evaporated gas circulation line L2. The third heat exchanger 90 can recover cold energy from the evaporated gas in the evaporated gas supply line L1. At this time, the evaporated gas in the evaporated gas supply line L1 can be preheated and supplied to the main compressor 40, and conversely, the evaporated gas in the evaporated gas circulation line L2 can be precooled and supplied to the second heat exchanger 30.

[0086] The evaporated gas that has passed through the main compressor 40 exchanges heat with the evaporated gas discharged from the liquefied gas storage tank 10 in the third heat exchanger 90, and then passes through the second heat exchanger 30 refrigerant in the expander line L4 and is then completely re-liquefied.

[0087] 2, when the temperature of the evaporated gas passing through the main compressor 40 is −50° C. or higher, the liquefied gas in the liquefied gas storage tank 10 can be supplied to the first liquefied gas supply unit S1 using a pump provided in the liquefied gas storage tank 10. When low-temperature liquefied gas is supplied to the first liquefied gas supply unit S1, the evaporated gas in the evaporated gas supply line L1 can be cooled.

[0088] At this time, a portion of the liquefied gas delivered to the first liquefied gas supply unit S1 can be delivered to the second liquefied gas supply unit S2 along a second liquefied gas supply line L6 that branches off from the first liquefied gas supply line L5 and is connected to the second liquefied gas supply unit S2. By lowering the temperature of the evaporated gas in the evaporated gas circulation line L2 that is supplied to the third heat exchanger 90, the reliquefaction efficiency in the third heat exchanger 90 can be improved.

[0089] On the other hand, if the temperature of the evaporated gas passing through the main compressor 40 is below -50°C, the operation of the pump installed in the liquefied gas storage tank 10 is stopped, and a portion of the low-temperature liquefied gas that has passed through the third heat exchanger 90 is supplied to the first liquefied gas supply unit S1 along the liquefied gas branch line L7 to control the temperature of the evaporated gas.

[0090] When the temperature of the evaporated gas passing through the main compressor 40 is -50°C or higher, the pump operates, and at this time the fifth control valve V5 is opened to transfer liquefied gas to the second liquefied gas supply unit S2. When the temperature of the evaporated gas passing through the main compressor 40 is lower than -50°C, the pump operation is stopped, and at this time the sixth control valve V6 is opened to transfer a portion of the liquefied gas circulating from the second heat exchanger to the liquefied gas storage tank to the first liquefied gas supply unit S1.

[0091] In the above description, whether or not the pump operates is determined based on the evaporative gas temperature being -50°C. However, this is the case when the ship 1 is anchored and the propulsion engine is not running. When the propulsion engine is running and the ship 1 is operating, whether or not the pump operates can be determined based on the evaporative gas temperature being -70°C.

[0092] That is, when the ship 1 is operating, if the temperature of the evaporated gas is -70°C or higher, the pump is operated to transfer liquefied gas to the first liquefied gas supply unit S1, and a portion of the liquefied gas transferred to the first liquefied gas supply unit S1 can be supplied to the second liquefied gas supply unit S2.

[0093] Meanwhile, when the ship 1 is sailing, the operation of the pump may be interrupted if the temperature of the evaporated gas is below -70°C, and a portion of the low-temperature liquefied gas that has passed through the second heat exchanger 30 may be supplied to the first liquefied gas supply unit S1. Here, the temperature of the evaporated gas at which the operation of the pump may be interrupted may be above -90°C and below -70°C.

[0094] As shown in FIG. 3, the second liquefied gas supply unit S2 may be provided upstream of the third heat exchanger 90, and as shown in FIG. 4, the second liquefied gas supply unit S2 may be provided downstream of the third heat exchanger 90.

[0095] In this way, the ship 1 according to the present invention can prevent the concentration of load on the refrigerant heat exchange section 33 by cooling the refrigerant using the evaporated gas in consideration of the temperature of the evaporated gas supplied to the main compressor 40 during the process of supplying the evaporated gas to the consumer 50 in a liquefied gas propelled ship.

[0096] Furthermore, the ship 1 according to the present invention cools the evaporative gas by separating the first evaporative gas heat exchange section 31 and the second evaporative gas heat exchange section 32, and by arranging the refrigerant heat exchange section 33 downstream of the first evaporative gas heat exchange section 31, the cooling efficiency of the refrigerant heat exchange section 33 can be increased and the size of the refrigerant heat exchange section 33 can be reduced.

[0097] In addition, the ship 1 according to the present invention can control the temperature of the evaporated gas upstream of the main compressor 40 by operating a pump to supply liquefied gas from the liquefied gas storage tank 10 to the upstream of the main compressor 40, or by re-liquefying the liquefied gas circulating from the main compressor 40 and supplying it to the upstream of the main compressor 40.

[0098] Furthermore, the ship 1 according to the present invention can reduce the load on the main compressor 40 by adjusting the temperature of the evaporative gas in the upstream stage of the main compressor 40.

[0099] In addition, the ship 1 according to the present invention can pre-cool the refrigerant by performing heat exchange between the evaporative gas transferred to the main compressor 40 and the refrigerant discharged from the refrigerant compressor 60, and can pre-cool the evaporative gas circulating from the main compressor 40 by performing heat exchange between the evaporative gas transferred to the main compressor 40 and the evaporative gas circulating from the main compressor 40.

[0100] The present invention is not limited to the above-described embodiments, and may include combinations of the above embodiments or combinations of at least one of the above embodiments with known techniques as further embodiments.

[0101] The present invention has been described in detail above through specific examples. However, these examples are for the purpose of specifically explaining the present invention, and the present invention is not limited thereto. It is clear that modifications and improvements can be made by a person having ordinary skill in the art within the technical spirit of the present invention.

[0102] Any simple variations or modifications of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Claims

1. a liquefied gas storage tank for storing liquefied gas; a main compressor that compresses evaporated gas generated in the liquefied gas storage tank and supplies it to a consumer; a first heat exchanger that recovers cold energy from evaporated gas supplied from the liquefied gas storage tank to the main compressor; a second heat exchanger that cools the evaporated gas circulating from the main compressor to the liquefied gas storage tank; a first liquefied gas supply unit that supplies liquefied gas to the evaporated gas in the upstream stage of the main compressor.

2. The compressor further includes a second liquefied gas supply unit that supplies liquefied gas to the evaporative gas in a downstream stage of the main compressor, 2. The ship according to claim 1, wherein whether or not the pump provided in the liquefied gas storage tank is operated is determined depending on whether or not the temperature of the evaporated gas supplied to the upstream stage of the main compressor is higher than a preset temperature.

3. 3. The vessel according to claim 2, wherein the preset temperature is determined to be between -70°C and -50°C.

4. 3. The ship described in claim 2, characterized in that when the temperature of the evaporated gas supplied to the upstream stage of the main compressor is equal to or higher than a preset temperature, the pump is operated to supply liquefied gas to the first liquefied gas supply unit.

5. 5. The ship according to claim 4, wherein a portion of the liquefied gas supplied to the first liquefied gas supply unit is supplied to the second liquefied gas supply unit.

6. 3. The ship described in claim 2, characterized in that when the temperature of the evaporated gas supplied to the upstream stage of the main compressor is lower than a predetermined temperature, the pump is not operated and a portion of the liquefied gas circulating from the second heat exchanger to the liquefied gas storage tank is supplied to the first liquefied gas supply unit.

7. In the first heat exchanger, 2. The ship according to claim 1, wherein heat exchange is performed between the evaporated gas supplied from the liquefied gas storage tank to the main compressor and the refrigerant discharged from the refrigerant compressor.

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