Abstract: A method is disclosed for cooling, condensing and subcooling a substantially single component gas stream by passing the gas stream through a heat exchange relationship with a vaporizing multicomponent stream so that carry-up of the condensed liquid phase is maintained without condensed phase backmixing and pot-boiling of the coolant stream is avoided. The single component gas stream is passed through a cold-end up heat exchanger having a serpentine pathway for the gas stream comprising a series of horizontal passes separated by horizontal dividers and alternatingly connected by turnaround passes at each end. The method is particularly applicable to the condensing of a recycle methane stream in a nitrogen rejection process which uses a methane heat pump cycle to provide refrigeration.

Abstract: A method is disclosed for cooling a multicomponent gas stream containing variable amounts of the components by passing the gas stream through a heat exchange relationship with a fluid coolant stream so that carry-up of the condensed phase is maintained without condensed phase backmixing over the compositional range of the multicomponent gas stream. The gas stream is cooled by passing it through a cold-end up heat exchanger having a serpentine pathway for the multicomponent gas stream comprising a series of horizontal passes separated by horizontal dividers and alternatingly connected by turnaround passes at each end, the cross-sectional area of at least one horizontal pass nearer the cold-end being less than the cross-sectional area of a horizontal pass nearer the warm-end. The method is particularly applicable to cooling a natural gas feed stream having a variable nitrogen content in a nitrogen rejection process.

Abstract: Enhanced recovery of the methane content of a multicomponent stream containing lower boiling gas components is obtained by effecting condensation of at least the major portion of the methane content in a dephlegmator wherein separated lower boiling components are employed as indirect heat exchange refrigerants.

Abstract: Enhanced recovery of ethane and ethylene from demethanizer overhead is obtained by subjecting the uncondensed vapor effluent from the main reflux condenser to further condensation and accompanying rectification in a dephlegmator and returning the liquid condensate from the dephlegmator to the demethanizer column. One or more of the refrigerants employed in the dephlegmator comprises vapors leaving the dephlegmator and cooled by pressure reduction.

Abstract: A process is provided for the separation and recovery of a major portion of the C.sub.2 + hydrocarbon content of a feed gas comprising hydrogen, methane, ethylene, and ethane. The feed gas is introduced to a dephlegmator to effect its separation into a vapor stream and a condensate stream. The condensate stream which is rich in C.sub.2 + hydrocarbons is passed to a demethanizer column where it is fractionated into an overhead methane-hydrogen stream and a bottoms product ethylene-ethane+ stream.