TAIL GAS TREATING PROCESS

摘要

A process for treating a sulfur-containing gas stream such as the Claus process off-gases by hydrogenation of unreduced sulfur followed by selective hydrogen sulfide absorption resulting in a vent gas that can be discharged directly to the atmosphere without incineration. A gas stream containing substantial unreduced sulfur values relative to the total sulfur concentration in the stream, is passed to a hydrogenation zone along with a hydrogenous gas. The gas stream may be first passed to a hydrolysis zone within which reduced sulfur values are hydrolized to produce hydrogen sulfide and carbon dioxide and the effluent from this zone then applied to the hydrogenation zone. The feed from the hydrogenation zone is cooled and passed to an absorption zone where it is contacted with an aqueous solvent which preferentially absorbs hydrogen sulfide in the presence of carbon dioxide. The absorption solution comprises an alkaline hydrogen sulfide absorbent and an acid having a pKa of 6 or less in a concentration to protonate 0.1-22% of the alkaline absorbent. The gas stream from the absorption zone is discharged to the atmosphere without prior incineration. Specifically disclosed solvents include solutions of alkanolamines in combination with organic or inorganic acids present in an amount to protonate 2-13% of the absorbent.