A ship comprises: a liquefied gas storage tank; a multi-stage compressor for compressing a boil-off gas discharged from a storage tank and comprising a plurality of compression cylinders; a second heat exchanger for heat exchanging a fluid, which has been compressed by the multi-stage compressor, and thus cooling same; a first decompressing device for expanding a flow (flow a1) partially branched from the flow (flow a) that has been cooled by the second heat exchanger; a third heat exchanger for heat exchanging, by flow a1 which has been expanded by the first decompressing device as a refrigerant, the remaining flow (flow a2) of flow a after excluding flow a1 that has been branched and thus cooling same; and a second decompressing device for expanding flow a2 which has been cooled by the third heat exchanger.

Disclosed is a re-liquefying device using a boil-off gas as a cooling fluid so as to reliquefy the boil-off gas generated from a liquefied gas storage tank provided in a ship. A boil-off gas re-liquefying device for a ship comprises: a multi-stage compression unit for compressing boil-off gas generated from a liquefied gas storage tank; a heat exchanger in which the boil-off gas generated from the storage tank and the boil-off gas compressed exchange heat; a vaporizer for heat exchanging the boil-off gas cooled by the heat exchanger and a separate liquefied gas supplied to a fuel demand source of a ship, and thus cooling the boil-off gas; an intermediate cooler for cooling the boil-off gas that has been cooled by the heat exchanger; and an expansion means for branching a part of the boil-off gas, which is supplied to the intermediate cooler, and expanding the same.

Disclosed is a re-liquefying device using a boil-off gas as a cooling fluid so as to re-liquefy the boil-off gas generated from a liquefied gas storage tank provided in a ship. A boil-off gas re-liquefying device for a ship comprises: a multi-stage compression unit for compressing boil-off gas generated from a liquefied gas storage tank; a heat exchanger in which the boil-off gas generated from the storage tank and the boil-off gas compressed exchange heat; a vaporizer for heat exchanging the boil-off gas cooled by the heat exchanger and a separate liquefied gas supplied to a fuel demand source of a ship, and thus cooling the boil-off gas; an intermediate cooler for cooling the boil-off gas that has been cooled by the heat exchanger; and an expansion means for branching a part of the boil-off gas, which is supplied to the intermediate cooler, and expanding the same.

A ship comprises: a tank; a multistage compressor for compressing a boil-off gas discharged from a storage tank and comprising a plurality of compression cylinders; a first heat exchanger for heat exchanging a fluid, which has been compressed by the multistage compressor, with the boil-off gas discharged from the storage tank and thus cooling the same; a first decompressing device for expanding a flow (flow a1) partially branched from the flow (flow a) that has been cooled by the first heat exchanger; a third heat exchanger for heat exchanging, by flow a1 which has been expanded by the first decompressing device as a refrigerant, the remaining flow (flow a2) of flow a after excluding flow a1 that has been branched and thus cooling the same; and a second decompressing device for expanding flow a2 which has been cooled by the third heat exchanger.

A ship comprises: a liquefied gas storage tank; a multi-stage compressor for compressing a boil-off gas discharged from a storage tank and comprising a plurality of compression cylinders; a second heat exchanger for heat exchanging a fluid, which has been compressed by the multi-stage compressor, and thus cooling same; a first decompressing device for expanding a flow (flow a1) partially branched from the flow (flow a) that has been cooled by the second heat exchanger; a third heat exchanger for heat exchanging, by flow a1 which has been expanded by the first decompressing device as a refrigerant, the remaining flow (flow a2) of flow a after excluding flow a1 that has been branched and thus cooling same; and a second decompressing device for expanding flow a2 which has been cooled by the third heat exchanger.

A power-saving type liquefied-gas-fuel ship includes: a liquefied gas storage tank storing liquefied gas; an engine using the liquefied gas stored in the liquefied gas storage tank or boil-off gas generated by spontaneous vaporization of the liquefied gas as fuel; a fuel feeder supplying the liquefied gas as fuel for the engine; a compressor compressing the boil-off gas to a pressure required for the engine; a heat exchanger cooling the remaining boil-off gas not supplied to the engine among the boil-off gas compressed by the compressor; a refrigerant circulation line in which the refrigerant supplied to the heat exchanger circulates; a refrigerant compressor compressing the refrigerant discharged from the heat exchanger after heat exchange in the heat exchanger; and a cold heat recovery device recovering cold heat of the liquefied gas supplied as fuel for the engine to cool the refrigerant compressed by the refrigerant compressor.

A system and a method with boil-off management for liquefied fuel storage are provided. The system includes a cryotank for storing a liquefied fuel, a pump for providing and compressing a first stream of the liquefied fuel, a heat exchanger for provide cooling duty to the first stream of the liquefied fuel, and an expansion valve for expanding the first stream of the liquefied fuel after the heat exchanger into a multiphase stream comprising a liquid phase and a gas phase. The multiphase stream has a temperature lower than an initial temperature of the first stream from the cryotank. The system further comprises a liquid-vapor splitter for separating the liquid phase and gas phase in the multiphase stream. The liquid phase is returned into the cryotank.

A vessel includes an engine; a first self-heat exchanger for heat-exchanging boil-off gas discharged from a storage tank; a multi-stage compressor for compressing, in multi-stages, the boil-off gas, which has passed through the first self-heat exchanger after being discharged from the storage tank; a first decompressor for expanding a portion of the boil-off gas, which has passed through the first self-heat exchanger after being compressed by the multi-stage compressor; a second decompressor for expanding the other portion of the boil-off gas, which has passed through the first self-heat exchanger after being compressed by the multi-stage compressor; and a second self-heat exchanger for heat-exchanging and cooling the portion of the boil-off gas, which has been compressed by the multi-stage compressor, by using, as a refrigerant, a fluid which has been expanded by the first decompressor.

A boil-off gas supply device is provided with: a storage tank configured to store a liquefied gas; a first compression mechanism configured to suck in the boil-off gas of the liquefied gas stored in the storage tank and compress the sucked boil-off gas; a second compression mechanism configured to compress the boil-off gas after being compressed by the first compression mechanism; a discharge path in which the boil-off gas discharged from the second compression mechanism flows; a first drive source configured to drive the first compression mechanism; and a second drive source that is different from the first drive source and configured to drive the second compression mechanism.

A vessel comprising an engine comprises: a first self-heat exchanger for heat-exchanging boil-off gas discharged from a storage tank; a multi-stage compressor for compressing, in multi-stages, the boil-off gas, which has passed through the first self-heat exchanger after being discharged from the storage tank; a second self-heat exchanger for precooling the boil-off gas compressed by the multi-stage compressor; a first decompressor for expanding a portion of a fluid which has been cooled by the second self-heat exchanger and the first self-heat exchanger; and a second decompressor for expanding the other portion of the fluid which has been cooled by the second self-heat exchanger and the first self-heat exchanger.