Abstract: The present invention relates to an improved process for the reliquefaction of boil-off gas containing up to 10% nitrogen resulting from the evaporation of liquefied natural gas (LNG) contained in a storage vessel. In the process, a closed-loop nitrogen refrigeration cycle is utilized wherein the nitrogen is isenthalpically expanded under conditions for generating a liquid and vapor with the liquid being pressurized by pumping and warmed against an initially cooled boil-off stream. The boil-off LNG stream is initially cooled by indirect heat exchange with an isentropically expanded refrigerant stream.

Abstract: The present invention is directed to a process for the purification and liquefaction of helium from a feed stream consisting essentially of nitrogen and helium with some minor impurities, wherein the helium is purified in a two step process: the first purification step comprising refrigerating the feed stream to condense nitrogen and any impurities from the feed stream, feeding the cooled feed stream to a separator, and removing from the bottom of the separator the condensed nitrogen and impurities in the feed stream and from the top of the separator a gaseous, high-helium-content stream; the second purification step comprising warming the gaseous, high-helium-content stream from the first purification step, feeding said stream to a pressure swing adsorber, and removing from the pressure swing adsorber an essentially pure helium stream, which is liquefied by feeding said essentially pure helium stream to a liquefier; wherein refrigeration is provided for the warm end of the liquefier and the two step purifica

Abstract: A system for liquefying and subcooling natural gas wherein compression power is shifted off the closed cycle refrigerant by subcooling the liquid natural gas to a relatively warm exit temperature and subsequently reducing the pressure and flashing the liquefied natural gas to recover a gaseous phase natural gas in excess of plant fuel requirements, the excess being recompressed and recycled to the feed to the process.

Abstract: A process and system are set forth for precooling, liquefying and subcooling a methane-rich feed stream, such as natural gas, with two closed circuit multicomponent refrigerant cycles in which the first refrigerant comprises a binary mixture of propane and butane in a flash refrigeration cycle and the second refrigerant comprises a mixture of nitrogen, methane, ethane, propane and butane in a subcool refrigeration cycle. The first refrigerant preferably cools the feed stream in a plate and fin heat exchanger.