Process for combusting ammonia-containing gases which also contain hydrogen sulfide

A process for combusting two gas streams, a first stream containing ammonia and hydrogen sulfide gases, and a second stream containing hydrogen sulfide gas and no ammonia, in the thermal zone of a sulfur recovery unit in which hydrogen sulfide-containing gases are partially combusted to a mixture of sulfur dioxide and hydrogen sulfide in a ratio of substantially 1:2 by supplying said hydrogen sulfide-containing gases to a burner consisting of a double gun having two concentric tubes and surrounded by an air register, which burner debouches into a mixing zone followed by a combustion zone, comprising supplying said second stream comprising primarily hydrogen sulfide-containing gases to the mixing zone via the outer of the two concentric tubes and mixing said stream in said mixing zone with an oxygen-rich gas or gas mixture supplied to the mixing zone via the air register, and separately supplying said first stream comprising primarily ammonia-containing gases to the thermal zone via the inner of the two concentric burner gun tubes, said ammonia-containing gases leaving the burner and entering the mixing zone at about the plane of emergence of said hydrogen sulfide-containing gases, and combusting said gases in the combustion zone.