METHOD OF NITROGEN DOUBLE EXPANSION Russian patent published in 2013 - IPC F25J1/02 

FIELD: machine building.

SUBSTANCE: method of natural gas liquification using the first and the second flow of nitrogen refrigerating agent; in this method each flow is subject to cycles of compression, cooling, expansion and heating during which the first flow of nitrogen is expanded to the first intermediate pressure, and the second flow of nitrogen - to the second, lower pressure; heating is performed in one or more heat exchangers, in which at least one of flows of expanded nitrogen is in heat exchange with natural gas. At least in one or more heat exchangers the first and the second flows of expanded nitrogen are in heat exchanger with natural gas and with both - the first and the second flow of compressed nitrogen. Liquification may be performed in three stages: at the initial stage the first flow of heated expanded nitrogen is used for cooling of natural gas; at the intermediate stage the first flow of compressed nitrogen is expanded to intermediate pressure and is used for cooling of natural gas; and at the final stage the second flow of compressed nitrogen is expanded to low pressure and is used for cooling of natural gas.

EFFECT: use of invention will allow complete liquification of natural gas not using hydrocarbons.

18 cl, 2 dwg