| 摘要 |
A method of natural gas liquefaction comprising first and second nitrogen refrigerant streams, each stream undergoing a cycle of compression, cooling, expansion and heating, during which the first nitrogen stream is expanded to a first, intermediate pressure and the second nitrogen stream is expanded to a second, lower pressure, and the heating occurs in one or more heat exchangers in which at least one of the expanded nitrogen streams is in heat exchanging relationship with natural gas, wherein, in at least one of said one or more heat exchangers, the first and second expanded nitrogen streams are in a heat exchanging relationship with the natural gas and both the first and second compressed nitrogen streams. The liquefaction can occur in three stages: in an initial stage the heated, expanded first nitrogen stream and the heated, expanded second nitrogen stream are used to cool the natural gas; in an intermediate stage the compressed first nitrogen stream is expanded to an intermediate pressure and used to cool the natural gas; and in a final stage the compressed, second nitrogen stream is expanded to a low pressure and used to cool the natural gas.
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