Refrigeration method and apparatus

摘要

A method of liquefying a permanent gas stream includes the step of reducing the temperature of the permanent gas stream at elevated pressure to below its critical temperature. The reduction in temperature is effected at least in part by countercurrent heat exchange with work expanded working fluid, at least some of which is at a temperature below the critical temperature of the permanent gas when it is brought into heat exchange relationship with the permanent gas stream. The permanent gas stream after being cooled to below its critical temperature is then subjected to at least three successive isenthalpic expansions. Resulting flash gas is separated from the resulting liquid. At least some of the flash gas is heat exchanged with the permanent gas stream at elevated pressure.