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 ship including a gas processing system. [Background technology]

[0002] A ship is a means of transportation that sails 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 propellers 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 to drive a propeller.

[0004] However, when heavy oil such as HFO or MFO is used as a propulsion fuel, environmental pollution due to various harmful substances contained in the 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 and diesel.

[0006] Such liquefied gases are stored in liquefied gas storage tanks in the liquid phase, and the advantage of this is that liquefied natural gas is reduced to 1 / 600 of its volume through liquefaction, while liquefied petroleum gas (LPG) is reduced to 1 / 260 of its volume for propane and 1 / 230 of its 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, technology for stably storing and processing liquefied gas is being continuously researched and developed. 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 concentration of load on the refrigerant heat exchanger by cooling the refrigerant using the evaporated gas, taking into account the temperature of the evaporated gas supplied to the main compressor in the process of supplying evaporated gas to a demand destination from a liquefied gas-propelled ship.

[0009] The object of the present invention is not limited to the above-mentioned objects, 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 further includes a second liquefied gas supply unit that supplies liquefied gas to the evaporative gas in the rear stage of the main compressor, and whether or not to operate a pump provided in the liquefied gas storage tank can be determined depending on whether or not the temperature of the evaporative gas supplied to the front stage 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 evaporative gas supplied to the upstream stage of the main compressor is equal to or 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 evaporative gas supplied to the upstream stage of the main compressor is lower than a preset 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, in the first heat exchanger, heat exchange may be performed between the evaporated gas transferred from the liquefied gas storage tank to the main compressor and the refrigerant discharged from a refrigerant compressor. Effect of the Invention

[0017] The ship according to the present invention can supply evaporation 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 description of the claims. [Brief description of the drawings]

[0019] [Figure 1] 1 shows a ship according to a first embodiment of the present invention. [Diagram 2] FIG. 4 shows a vessel according to a second embodiment of the present invention. [Diagram 3] FIG. 13 shows a vessel according to a third embodiment of the present invention. [Figure 4] FIG. 13 shows a vessel according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[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) or liquefied petroleum gas (LPG), ethylene, ammonia, etc., and gas that is not in a liquid state due to heating or pressure can also be referred to as liquefied gas for convenience. This can also be applied to evaporated gas. In addition, LNG can be used to encompass not only natural gas (NG) in a liquid state, but also natural gas (NG) in a supercritical state, for convenience, and evaporated gas can be used to encompass not only evaporated gas in a gaseous state, but also evaporated gas that has been liquefied.

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

[0023] In the following, the expressions "first", "second", etc., are intended to indicate that a specific configuration is provided in a plurality of times in the present invention, and each expression may indicate any one of the plurality of configurations. When the expressions "first", "second", etc., are not added, the configuration may be a concept that includes all the configurations to which the expressions "first", "second", etc., are 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 consumer 50.

[0027] The ship 1 may be anchored or in operation, and when the ship 1 is anchored, the generator engine 51 operates, and when the ship 1 is in operation, the generator 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 about 13 bar, and the inlet temperature of the main compressor 40 may be -70°C. The liquefied gas storage tank 10 stores the liquefied gas to be supplied to the demand destination 50. In this case, the liquefied gas storage tank 10 may store the 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, and a plurality or more of them may be arranged side by side.

[0029] Although the liquefied gas storage tank 10 has a thermal insulation structure, when heat is applied to 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 level 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, the pressure of the evaporated gas increases, and the evaporated gas may reach a pressure state required by the consumer 50.

[0032] The consumer 50 may be a dual fuel (DF) engine as a main propulsion device. In this specification, when it is stated that the liquefied gas is delivered to the consumer 50, it may include the liquefied gas being delivered to a generator 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 heat 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 evaporated gas cold energy 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 a first control valve V1 provided in the evaporated gas cold energy recovery line L31 and a 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 through the evaporated gas cold heat recovery line L31, the flow rate of the refrigerant supplied to the second heat exchanger 30 is relatively reduced, and the load required to cool the refrigerant in the second heat exchanger 30 can be reduced. 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, and thus the load required to cool the refrigerant in the second heat exchanger 30 is reduced.

[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 or exceeds a certain level upstream of the main compressor 40.

[0037] The evaporated gas supply line L1 branches off in a portion downstream 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 at the rear 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 parts. The second heat exchanger 30 may include a first evaporation gas heat exchange part 31, a second evaporation gas heat exchange part 32, and a refrigerant heat exchange part 33. In this specification, the first evaporation gas heat exchange part 31, the second evaporation gas heat exchange part 32, and the refrigerant heat exchange part 33 provided in the second heat exchanger 30 may refer to regions provided in one device, the second heat exchanger 30, or flow paths provided in the second heat exchanger 30.

[0040] Specifically, the first evaporated gas heat exchange section 31 and the second evaporated gas heat exchange section 32 exchange heat between the refrigerant that has passed through the expander 70 and the evaporated gas circulating from the main compressor 40 to the liquefied gas storage tank 10, and the refrigerant heat exchange section 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 the evaporated gas discharged from a liquefied gas storage tank 10, and in the second heat exchanger 30, the refrigerant exchanges heat with the 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, so that the refrigerant discharged from the refrigerant compressor 60 can be cooled. Also, in the refrigerant heat exchange section 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, so that the refrigerant that has passed through the refrigerant compressor 60 can be cooled.

[0044] The higher the temperature of the evaporative gas transmitted to the demand destination 50 via the main compressor 40, the larger its volume becomes, and as the volume of the evaporative gas increases, the greater the load on the main compressor 40 becomes. 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 is less than -50°C.

[0045] However, the refrigerant is cooled as it is repeatedly compressed and expanded, and the cold generated during this process is used to cool the evaporative gas. However, since this places a large burden 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 burden 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 in which the temperature of the evaporative gas passing through the main compressor 40 is maintained 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] In this manner, 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 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 to re-liquefy the evaporated gas by making maximum use of the cold energy of the evaporated gas.

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

[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. A portion of the refrigerant exchanges heat in the second evaporated gas heat exchange section 32 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 in the refrigerant heat exchange section 33 with the refrigerant discharged from the refrigerant compressor 60.

[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 evaporated gas heat exchange section 32 can primarily cool the evaporated gas circulating to the liquefied gas storage tank 10. The temperature of the refrigerant transferred from the rear stage of the first evaporated gas heat exchange section 31 to the second evaporated gas heat exchange section 32 can be lower than the temperature of the front stage of the expander 70. In the second evaporated gas heat exchange section 32, the refrigerant lowers the temperature of the evaporated gas circulating to the liquefied gas storage tank 10, thereby reducing the load applied to liquefy the evaporated gas in the first evaporated gas heat exchange section 31.

[0052] The first evaporative gas heat exchange section 31 can secondarily cool the evaporative gas discharged from the second evaporative gas heat exchange section 32. Since the evaporative gas is primarily cooled in the second evaporative gas heat exchange section 32, the load on the first evaporative gas heat exchange section 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 by using the refrigerant discharged from the first evaporation gas heat exchanger 31. Since the second evaporation gas heat exchanger 32 is partially responsible for cooling the evaporation gas of the first evaporation gas heat exchanger 31, the temperature of the refrigerant passing through the first evaporation gas heat exchanger 31 can be relatively low compared to a case in which the second evaporation 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 to increase the cooling efficiency of the refrigerant heat exchanger 33, and 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 in 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 refrigerant compressor 60 is cooled in the refrigerant heat exchanger 33 using the refrigerant discharged from the first evaporative gas heat exchanger 31, the refrigerant cooling efficiency is increased 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, details of which will be described below with reference to FIG. 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 can be 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 of 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 of the main compressor 40 is relatively high, the standard temperature of the evaporative gas passing through the main compressor 40 can be even lower, to -70°C.

[0057] In this way, the standard temperature of the evaporative gas passing through the main compressor 40 may change 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] Description of configurations common to those described in FIG. 1 may be omitted below.

[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. In the first heat exchanger 20, heat exchange may be performed between the evaporated gas in the evaporated gas supply line L1 and the refrigerant in the evaporated gas cold heat recovery line L31. In the second heat exchanger 30, heat exchange may be performed between the refrigerant in the expander line L4 and the refrigerant in the first refrigerant line L32, and heat exchange may be performed between the refrigerant in the expander line L4 and the liquefied gas or evaporated gas in the evaporated gas circulation line L2.

[0061] In the first heat exchanger 20, it is possible to recover the cold energy of the evaporated gas in the liquefied gas storage tank 10. The refrigerant that has passed through the first heat exchanger 20 along the evaporated gas cold energy recovery line L31 is pre-cooled, and is 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 reliquefied in the second heat exchanger 30.

[0064] Meanwhile, as described in Fig. 1, the higher the temperature of the evaporated gas transmitted to the demand destination 50 via the main compressor 40, the larger the volume thereof becomes, and as the volume of the evaporated gas increases, the load on the main compressor 40 may increase. Also, as the temperature of the evaporated gas passing through the main compressor 40 increases, the cold energy recovered in the first heat exchanger 20 becomes insufficient, and the efficiency of re-liquefying the evaporated gas in the second heat exchanger 30 may decrease. 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 is less than -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. The evaporated gas in the evaporated gas supply line L1 can be cooled by supplying low-temperature liquefied gas to the first liquefied gas supply unit S1.

[0066] However, if liquefied gas is supplied from the liquefied gas storage tank 1 to the first liquefied gas supply unit S1 and the liquefied gas is simply circulated to the liquefied gas storage tank 1, heat may be injected into the liquefied gas storage tank 1, decreasing the reliquefaction efficiency of the evaporated gas. To prevent this, the liquefied gas in the liquefied gas storage tank 10 may be transferred to the second liquefied gas supply unit S2 along the second liquefied gas supply line L6, which is branched off from the first liquefied gas supply line L5 and connected to the second liquefied gas supply unit S2. By supplying liquefied gas to the second liquefied gas supply unit S2, the reliquefaction efficiency of the evaporated gas may be increased by about 7%.

[0067] At this time, the third control valve V3 can be opened to transmit the 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 increased.

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

[0069] Rather, if the temperature of the evaporated gas supplied to the main compressor 40 is sufficiently low compared to the temperature of the evaporated gas passing through the main compressor 40, 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 reliquefaction 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 a waste of electricity used by the pump and an increase in the amount of evaporated gas generated in the liquefied gas storage tank due to heat seeping through 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 frequently repeated, 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 may reduce the re-liquefaction efficiency and increase energy consumption during the re-liquefaction 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, the operation of the pump installed in the liquefied gas storage tank 10 can be determined according to the temperature of the evaporated gas supplied to the upstream of the main compressor 40.

[0074] The temperature of the evaporated gas upstream of the main compressor 40, which determines whether the pump operates or not, 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 manner, the temperature of the evaporated gas may be adjusted by supplying the low-temperature liquefied gas supplied through 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 -90°C or more and less than -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 less 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, 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 ship 1's propulsion engine is running and the ship 1 is sailing, 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 -90°C or higher and lower than -70°C.

[0080] FIG. 3 shows a ship 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] Description of configurations common to those described in FIG. 1 and FIG. 2 may be omitted below.

[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 cross each other, so that heat exchange can be performed between the refrigerant in the expander line L4 and the refrigerant in the first refrigerant line L32, and heat exchange can be performed between the refrigerant in the expander line L4 and the liquefied gas or evaporated gas in the evaporated gas circulation line L2.

[0085] In the third heat exchanger 90, heat exchange can be performed 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 heat 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 exchanges heat with the refrigerant in the expander line L4 in the second heat exchanger 90, so that the evaporated gas is completely re-liquefied.

[0087] 2, when the temperature of the evaporated gas passing through the main compressor 40 is −50 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. The evaporated gas in the evaporated gas supply line L1 can be cooled by supplying low-temperature liquefied gas to the first liquefied gas supply unit S1.

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

[0089] On the other hand, when 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 interrupted, 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 section 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 less than -50°C, the pump operation is interrupted, 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, 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 ship 1's propulsion engine is running and the ship 1 is sailing, 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 -90°C or higher and lower than -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 concentration of load on the refrigerant heat exchange section 33 by cooling the refrigerant using the evaporative gas in consideration of the temperature of the evaporative gas supplied to the main compressor 40 during the process of supplying the evaporative gas to the consumer 50 in a liquefied gas propelled ship.

[0096] In addition, 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, it is possible to increase the cooling efficiency in the refrigerant heat exchange section 33 and reduce the size of the refrigerant heat exchange section 33.

[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, thereby controlling the temperature of the evaporated gas upstream of the main compressor 40.

[0098] In addition, 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 transmitted 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 transmitted to the main compressor 40 and the evaporative gas circulating from the main compressor 40.

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

[0101] The present invention has been described in detail above through specific examples. However, these 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 those having ordinary skill in the art within the technical spirit of the present invention.

[0102] Any simple variations or modifications of the present invention belong to 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 the evaporated gas generated in the liquefied gas storage tank and supplies it to a consumer; a first heat exchanger that recovers cold energy from an evaporated gas supplied from the liquefied gas storage tank to the main compressor; a second heat exchanger for cooling 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 evaporation gas in a front 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 rear stage of the main compressor, 2. The ship according to claim 1, wherein whether or not a pump provided in the liquefied gas storage tank is operated is determined depending on whether or not a temperature of the evaporated gas supplied to a front 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 in the range of -70°C to -50°C.

4. The ship described in claim 2, characterized in that when the temperature of the evaporative 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 section.

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. The ship described in claim 2, characterized in that when the temperature of the evaporative 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 evaporation gas supplied from the liquefied gas storage tank to the main compressor and the refrigerant discharged from a refrigerant compressor.

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