Process for recovery of sulfur from so.sub.2 -containing gas

Abstract

A process for recovery of sulfur from SO.sub.2 -containing gas which comprises the steps of supplying said SO.sub.2 -containing gas mixed with additional oxygen to a SO.sub.2 reduction reactor filled with solid carbonaceous materials for reducing part of the SO.sub.2 into H.sub.2 S, a vaporous sulfur and COS; separating said vaporous sulfur by condensation from an effluent gas coming from this SO.sub.2 reduction reactor to thereby produce a first gaseous mixture; supplying this first gaseous mixture to a Claus reactor to further produce a vaporous sulfur by Claus reaction; separating said vaporous sulfur by condensation from an effluent gas coming from this Claus reactor to thereby produce a second gaseous mixture; measuring the concentrations of SO.sub.2 and H.sub.2 S in this second gaseous mixture and further the concentration of COS as occasion demands; and controlling the amount of oxygen supplied to the SO.sub.2 - containing gas introduced into said SO.sub.2 reduction reactor in accordance with said measured concentrations, thereby maintaining the H.sub.2 S/SO.sub.2 molar ratio or (H.sub.2 S+COS)/SO.sub.2 molar ratio of said first gaseous mixture at a level of about 2.