Patent ID: 8739569

Claim:
A liquefied gas reliquefier for reliquefying boil-off gas (hereinafter abbreviated to “BOG”) resulting from evaporation of liquefied gas in a plurality of liquefied-gas storage tanks to prevent a rise in the internal pressure of the liquefied-gas storage tanks, the liquefied gas reliquefier comprising: a cooling unit for liquefying a secondary refrigerant which is a liquid having a melting point lower than a condensation temperature of the BOG, the cooling unit being disposed in a secondary-refrigerant circulating channel through which the secondary refrigerant circulates; a liquefied-secondary-refrigerant feeding unit for feeding the liquefied secondary refrigerant cooled by the cooling unit through the secondary-refrigerant circulating channel; a heat exchange unit disposed in the secondary-refrigerant circulating channel to condense the BOG by heat exchange between the BOG and the liquefied secondary refrigerant fed by the liquefied-secondary-refrigerant feeding unit; a header pipe for being disposed above the plurality of liquefied-gas storage tanks; a precooling unit for precooling the secondary refrigerant supplied into the secondary-refrigerant circulating channel with cold energy possessed by the BOG, wherein the heat exchange unit is disposed inside a channel of the header pipe, wherein the cooling unit includes a plurality of pulse-tube refrigerators, and wherein the number of pulse-tube refrigerators in operation and/or the cooling capacities of the individual pulse-tube refrigerators are controlled based on a measurement result from at least one of thermometers, pressure gauges, and pump discharge flow meters installed in the liquefied gas storage tanks.