| 摘要 |
A process for liquefying a gas at a pipeline pressure of above about 650 psia and at ambient temperature, in which the gas is cooled to sequentially lower temperatures, by passing the gas through a plurality of cooling stages in indirect heat exchange with at least one refrigerant and near its liquefaction temperature, the cooled gas is expanded to a lower pressure, the expanded gas is further cooled to its liquefaction temperature, using indirect heat exchange with an expanded refrigerant, the liquefied gas is expanded to atmospheric pressure for storage or transport, by passing the liquefied gas through at least one expansion stage and vapors collected from the expanded stage are compressed and added to the expanded gas prior to liquefaction. To the extent that the gas is natural gas and contains significant amounts of nitrogen, the liquefied gas is passed through a nitrogen rejection cycle prior to passage through the expansion stage.
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