Abstract: An ammonia-containing gas stream and a hydrogen sulfide-containing gas stream are combusted to a mixture of SO.sub.2 and H.sub.2 S in a ratio of substantially 1:2 in the thermal zone of a sulfur recovery unit by feeding said streams separately to a burner comprising a double-barrelled gun of two concentric tubes, the ammonia-containing gas stream being fed to the inner tube of the gun and the hydrogen sulfide-containing gas stream being fed to the outer tube.

Abstract: An improved Claus off-gas treating process is disclosed where sulfur dioxide and other convertible sulfur compounds present in the off-gas are catalytically reduced to hydrogen sulfide by mixing said off-gases with the hot gaseous product of the combustion of a carbonaceous fuel with an oxygen-containing gas in a line burner to heat the off-gases to a temperature above 175.degree.C and passing the heated gaseous product together with a hydrogen-containing gas over a reduction catalyst thereby converting substantially all of the sulfur dioxide and other convertible sulfur compounds present to hydrogen sulfide which is subsequently removed with an absorbent or absorbent for hydrogen sulfide.