Abstract: A process for separation of a high pressure gas stream such as refinery gas in which the starting gas mixture is cooled and separated into a first vapor portion and a first liquid portion which is expanded to an intermediate pressure. The first vapor portion is further cooled and separated into a second vapor portion which may be further processed for ultimate recovery of, for example, a methane-rich product gas and a second liquid portion which is expanded to essentially the same intermediate pressure and combined with the expanded first liquid portion. The resulting mixed intermediate pressure stream or a portion thereof is then employed as refrigerant.

Abstract: A process for separation of a high pressure gas stream such as light refinery gases in which the gas mixture is expanded, preferably through a turbine, and separated into first vapor and liquid portions. The first vapor portion may be recovered as, for example, methane-rich product gas. The first liquid portion is raised to an intermediate pressure, revaporized, and introduced to a fractionator from which an ethane-containing stream is recovered. The ethane-containing stream is then cooled and separated into a second vapor portion and a second liquid portion which is then expanded and combined with the expanded starting gas mixture to increase the amount of refrigeration that may be recovered from the first liquid stream prior to its fractionation.

Abstract: A process for separating gaseous or liquid hydrocarbons in first and second fractionation zones wherein the first fractionation zone employs a side reboiler discharging below the side draw point. A vapor sidestream is removed from the first fractionator below the side draw point and introduced to the second fractionator. The flow scheme permits control of the first fractionator bottoms temperature to match available low level waste heat which may therefore be used in fractionator reboiling duty.