SYSTEM FOR REPEATED LIQUEFACTION OF BOIL-OFF GAS AND METHOD OF REMOVAL OF LUBRICATING OIL FROM SYSTEM OF REPEATED LIQUEFACTION OF BOIL-OFF GAS

摘要

FIELD: shipbuilding.;SUBSTANCE: invention relates to shipbuilding and concerns vessels for transportation of liquefied natural gas or operating on liquefied natural gas. Disclosed are a liquefying system for boil-off gas (BOG) and a method of removing lubricating oil from a BOG re-liquefaction system configured to be re-liquefied by BOG by compressing BOG with a compressor, cooling of compressed BOG by means of heat exchange with uncompressed BOG by means of heat exchanger and reduction of pressure of fluid medium, cooled by heat exchange, by means of pressure reducer. According to the method of removing lubricating oil, the compressor comprises at least one cylinder operating in an oil lubrication mode, and wherein it is determined that time has elapsed for removal of condensed or solidified lubricating oil, if the lower value between the temperature difference between BOG before the heat exchanger to be used in the heat exchanger as a cooling agent, and BOG, compressed in compressor and cooled by means of heat exchanger, and temperature difference between BOG, used as cooling agent in heat exchanger, and BOG, compressed by means of compressor and directed to heat exchanger, is the first preset value or more and is maintained for a predetermined period of time or more, or if the pressure difference between the BOG compressed by the compressor and directed into the heat exchanger, in the area ahead of the heat exchanger and the BOG cooled by the heat exchanger, in the place after the heat exchanger, is the second preset value or more and is stored for a predetermined period of time or more.;EFFECT: technical result consists in improvement of efficiency of repeated liquefaction BOG.;14 cl, 13 dwg