Process for treating acid gas in staged furnaces with inter-stage heat recovery and inter-stage sulfur production

A combustion process in a spent acid recovery plant for treating an acid gas comprising hydrogen sulfide which comprises:

• (a) introducing a first acid gas, which comprises hydrogen sulfide, and a first oxygen-containing gas into a reducing furnace producing a first oxidized gas stream;
• (b) introducing the first oxidized gas stream into a first heat recovery system which is a waste heat boiler, wherein the stream is cooled and heat is recovered therefrom;
• (c) introducing the cooled first oxidized gas stream to a sulfur condenser wherein elemental sulfur is removed from the stream to produce a sulfur-stripped stream;
• (d) introducing the sulfur-stripped stream, a second oxygen-containing gas, and spent acid comprising sulfuric acid into an oxidizing furnace, producing a second oxidized gas stream;
• and
• (e) introducing the second oxidized gas stream into a second heat recovery system;
• wherein the stream is cooled and heat is recovered therefrom;
• and