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 liquefied natural gas (LNG) management system that stores natural gas in a liquefied state in an isothermal storage tank. A modular multi-fueling platform is in fluid communication with the isothermal storage tank. The modular multi-fueling platform includes a LNG conditioning tank, a compressor, a heat exchanger, a heater, plumbing, associated valves, various sensing transmitters, and a programmable logic computer (PLC). Data acquired by the PLC determines actions by the modular multi-fueling platform, including operation of valves, the compressor, etc. The system transfers LNG between the storage tank, the conditioning tank, and a cargo tank (consumer's vehicle tank). The system employs steps of heating and compressing the LNG and boil off gas to maintain the LNG at temperature. The system employs pressure differences for transferring the LNG between tanks.

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.

Systems and methods are described for increasing capacity and efficiency of a nitrogen refrigerant boil-off gas recovery system for a natural gas storage tank. Boil-off gas is condensed against two-phase nitrogen in a condensing heat exchanger having an inner vessel through which the boil-off gas flows and an outer vessel through which the two phase nitrogen flows. Logic controls maintain storage tank pressure and power consumption within preferred levels by adjusting the pressure of the two-phase nitrogen in the heat exchanger. Additional logic controls maintain the temperature difference between the nitrogen streams entering into and returning from the cold end of a second heat exchanger by controlling the position of an expansion valve on the return circuit.

A gas processing system according to an embodiment of the present invention controls inflow fuel pressure of a low pressure demand source according to an operation or a non-operation of a high pressure demand source and the low pressure demand source.

Disclosed is a method of discharging lubricant oil from a BOG reliquefaction system configured to reliquefy BOG by compressing the BOG by a compressor, cooling the compressed BOG through heat exchange with non-compressed BOG by a heat exchanger, and reducing a pressure of fluid cooled through heat exchange by a pressure reducer. In the lubricant oil discharge method, the compressor comprises at least one oil-lubrication type cylinder and it is determined that it is time to discharge condensed or solidified lubricant oil, if at least one of preset conditions is satisfied.

The invention relates to a gas treatment method and system of a gas storage facility (2), in particular on board a ship, the method comprising the following stages: an extraction of a first gas (4a, 4b, 5a, 5b,) in the liquid state from a first tank (4) or first vessel (5; 500), a first subcooling of the first gas in the liquid state, and storage of the subcooled first gas in the liquid state in the lower part of the first tank (4) or of the first vessel (5; 500) or of a second tank or of a second vessel, so as to constitute a reserve layer of cold (4c, 5c, 500c) of the subcooled first gas in the liquid state at the bottom of the first or second tank (4) or of the first or second vessel (5; 500).

Disclosed is a BOG reliquefaction system. The BOG reliquefaction system includes: a compressor compressing BOG; a heat exchanger cooling the BOG compressed by the compressor through heat exchange using BOG discharged from a storage tank as a refrigerant; a bypass line through which the BOG is supplied to the compressor after bypassing the heat exchanger; a second valve disposed on a second supply line through which the BOG used as the refrigerant in the heat exchanger is supplied to the compressor, the second valve regulating a flow rate of fluid and opening/closing of the second supply line; and a pressure reducer disposed downstream of the heat exchanger and reducing a pressure of fluid cooled by the heat exchanger, wherein the compressor includes at least one oil-lubrication type cylinder and the bypass line is joined to the second supply line downstream of the second valve.

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.

A method for large-scale, air-cooled floating liquefaction, storage and offloading of natural gas gathered from onshore gas pipeline networks. Gas gathered from on-shore pipeline quality gas sources and pre-treated to remove unwanted compounds is compressed and cooled onshore before being piped to an offshore vessel for liquefaction to produce LNG.