Process for reducing the total sulfur content of a high CO2 -content feed gas

Claim 1

A process for reducing the total sulfur content of a high CO 2 -content feed gas to environmentally acceptable levels comprising: (a) passing a feed gas stream comprising 40 to 95% volume CO 2 , 0.03 to 20% volume H 2 S, and 0.02 to 2% volume COS to a first absorption step where said feed gas stream is contacted with a liquid and regenerable polyalkanolamine absorbent selective for hydrogen sulfide, therein producing an unabsorbed portion and a hydrogen sulfide-enriched polyalkanolamine absorbent; (b) passing said unabsorbed portion of the feed gas stream from step (a) together with a hydrogen- and/or carbon monoxide-containing gas, the off gases from the associated Claus process step (e), and a certain amount of steam over a sulfided Group VI and/or Group VIII metal catalyst supported on an inorganic oxidic carrier in a reduction step wherein the aount of steam is adjusted to reduce the COS concentration in the resulting treated gas to a level below about 0.05% volume; (c) passing the gas stream thus treated in said reduction step (b) to a second absorption step in which said treated gas stream is contacted with a liquid and regenerable polyalkanolamine absorbent under such conditions that the unabsorbed portion of said treated gas stream has below about 0.05% volume total sulfur compounds, discharging the unabsorbed portion of said treated gas stream, optionally after incineration, into the atmosphere, and producing a hydrogen sulfide-enriched polyalkanolamine absorbent; (d) regenerating the hydrogen sulfide-enriched absorbents from absorption steps (a) and (c) by heating and/or stripping and using them again for further absorption of hydrogen sulfide; (e) passing the hydrogen sulfide liberated in the regeneration step (d) to a Claus process step; and (f) passing the off-gases produced in said Claus process step (e) to said reduction step (b).