Patent ID: 6250105
Filing Date: 2001-06-26
Classification: F25J

Abstract:
A process for liquefying a natural gas stream to produce pressurized liquid product having a temperature above -112.degree. C. (-170.degree. F.) and a pressure sufficient for the liquid product to be at or below its bubble point using two closed cycle, multi-component refrigerants wherein a high-level refrigerant cools a low-level refrigerant and the low-level refrigerant cools and liquefies the natural gas, comprising the steps of:(a) cooling and liquefying a natural gas stream by indirect heat exchange with a low-level multi-component refrigerant in a first closed refrigeration cycle,(b) warming the low-level refrigerant by heat exchange in countercurrent relationship with another stream of the low-level refrigerant and by heat exchange against a stream of the high-level refrigerant;(c) compressing said warmed low-level refrigerant of step (b) to an elevated pressure and aftercooling it against an external cooling fluid;(d) further cooling said low-level refrigerant by heat exchange against a second stream of the high-level multi-component and against the low-level refrigerant of step (b), said high-level refrigerant being warmed during the heat exchange; and(e) compressing said warmed high-level refrigerant of step (d) to an elevated pressure and aftercooling it against an external cooling fluid.