Economic recovery of ethylene and/or propylene from low concentration feeds
First Claim
1. A process for recovering C2 -C4 olefins from a gaseous feedstream obtained from a Fischer-Tropsch waste gas containing about 2-3 mol % ethylene or propylene, said process comprising in a first process stage, scrubbing said gaseous feedstream with a C4 -C8 liquid hydrocarbon, to absorb said olefin therein and recovering from said liquid hydrocarbon a gaseous stream, the weight percent concentration of said olefins in said gaseous stream being at least about 25%;
- and in a second process stage, recovering said olefins from said gaseous stream by a low-temperature separation, and wherein said Fischer-Tropsch waste gas is subjected to a carbon dioxide separating step before entering the first stage.
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Abstract
C2 -C3 olefins are recovered from a low concentration gaseous feedstream, e.g. a Fischer-Tropsch waste gas. In a first process stage, the weight percent concentration of the olefins is enriched to at least about 25%. One specific enrichment technique includes scrubbing, preferably 2-stage scrubbing, with hydrocarbon scrubbing agents. Another technique comprises condensation of the olefin in regenerators and absorbing same in a purge phase. The resultant enriched stream, in any case, is then subjected to conventional low temperature separation to recover relatively pure individual streams of ethylene and propylene.
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Citations
20 Claims
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1. A process for recovering C2 -C4 olefins from a gaseous feedstream obtained from a Fischer-Tropsch waste gas containing about 2-3 mol % ethylene or propylene, said process comprising in a first process stage, scrubbing said gaseous feedstream with a C4 -C8 liquid hydrocarbon, to absorb said olefin therein and recovering from said liquid hydrocarbon a gaseous stream, the weight percent concentration of said olefins in said gaseous stream being at least about 25%;
- and in a second process stage, recovering said olefins from said gaseous stream by a low-temperature separation, and wherein said Fischer-Tropsch waste gas is subjected to a carbon dioxide separating step before entering the first stage.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A process for recovering C2 -C4 olefins from a gaseous feedstream obtained from a Fischer-Tropsch waste gas containing 2-3% ethylene or propylene, said process comprising in a first process stage partially condensing said feedstream in at least one of several cyclically operated and interconnected regenerators to condense out olefins in said regenerator and then removing said condensed out olefins therefrom as a gaseous stream having a weight percent concentration of said olefins of at least 25%;
- and in a second process stage recovering said olefins from said gaseous stream by a low temperature separation, and wherein said Fischer-Tropsch waste gas is subjected to a carbon dioxide separating step prior to entering the first stage.
- View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
Specification