| abstract |
A continuous process is described for contacting a raw hydrocarbon gas which is lean and/or at a pressure above about 400 psia with a preferential physical solvent within an extractive-stripping (ES) column to produce a residue gas, containing selected amounts of an undesired hydrocarbon component and lighter hydrocarbons, and a rich solvent, containing the remaining desired hydrocarbons, which is sent to a distilling step in which the product is produced as overhead and the lean solvent is produced as bottoms. To avoid undesirably high bottoms temperatures in the ES column, a portion of the product is recycled to and admixed with the inlet raw gas to the extractive-stripping step to enrich the raw gas. This recycled stream may be: (1) a broad-spectrum recycle stream of gas products, after compression and before cooling thereof, (2) a broad-spectrum recycle stream of liquid products, after compression, cooling, and complete condensation thereof, (3) a relatively narrow-spectrum recycle vapor stream of C2-C4 products, after compression, cooling, and partial condensation thereof, or (4) a relatively narrow-spectrum recycle liquid stream of predominantly C4+ product, for example, after compression, cooling, and partial condensation thereof. This enriching step increases the partial pressure of the heavy hydrocarbon components and thereby permits higher recoveries of ethane and/or propane and/or butane while rejecting undesirable hydrocarbons without having to use an undesirably high temperature within the ES column. Without the recycling step, it is quite difficult to achieve high recoveries of desired components and meet product specifications regarding undesired hydrocarbons in the residue gas stream and in the product stream. |