Light gas separation from hydrocarbons for variable composition feed streams

Abstract

The invention is a process and apparatus for separating the components of a multi-component gas stream comprising light and heavier volatility components with a variable composition. The process includes contacting the multi-component gas stream with a lean solvent in an absorber to produce a light component overhead stream and a rich solvent bottoms stream, flashing the rich solvent bottoms stream in at least a first, second and third reduced constant pressure of sequentially lower pressure wherein the released gas is compressed and a part is routed back to the absorber bottoms as stripping gas and a part is routed as a part of the heavier product stream. In this invention compressed vapor from the first or second reduced constant pressure rich solvent flash vessel is split by flow control between recycle routing to the absorber bottom stage as stripping gas and to the heavier product hydrocarbon stream, depending on the feed gas concentration of light component. The third and any additional flash vessels at sequentially lower pressure produce flash gas that is the remainder of the produced hydrocarbon product stream. The lean solvent remaining after the lowest pressure flash is routed back to the top of the absorber.