Process for reduction of sulfur dioxide to sulfur

A process for producing elemental sulfur from sulfur dioxide-containing gases having at least about 10 percent sulfur dioxide therein comprising

• introducing a carbonaceous fuel and an oxygen-containing gas into a thermal reduction zone, said oxygen-containing gas being up to about a sufficient amount on a stoichiometric basis for complete combustion of the fuel,
• combusting said carbonaceous fuel with said oxygen-containing gas within the thermal reduction zone to provide combustion gases having temperatures at about 1100.degree. to 2000.degree. C. and to provide sufficient heat to maintain thermal reduction temperatures in the thermal reduction zone;
• introducing a reducing agent capable of reducing sulfur dioxide to sulfur in the thermal reduction zone;
• introducing into the thermal reduction zone, and commingling said sulfur dioxide-containing gases with the combustion gases wherein said combusting has proceeded sufficiently such that the combustion gases contain less than about 0.2 volume percent free or molecular oxygen, and wherein the mole ratio of hydrogen equivalents contained in said reducing agent and in said combusted gases to sulfur dioxide provided for thermal reduction in the thermal reduction zone is about 1.8 to 2.2;
• thermally reducing about 50 to 80 percent of the sulfur dioxide in the sulfur dioxide-containing gases to elemental sulfur in the thermal reduction zone under reducing conditions including temperatures of about 950.degree. to 1250.degree. C. and an essential absence of free or molecular oxygen to produce an elemental sulfur-containing thermal reduction effluent wherein the gas velocity in the thermal reduction zone is about 1 to 25 meters per second and the residence time of the sulfur dioxide-containing gases in the thermal reduction zone is about 0.1 to 4 seconds;
• cooling the thermal reduction effluent to about 240.degree. to 400.degree. C.;
• subjecting the cooled thermal reduction effluent to catalytic hydrolysis in the presence of a catalytically-effective amount of a hydrogenation and hydrolysis catalyst to hydrolyze carbon disulfide and carbonyl sulfide contained in the thermal reduction effluent to hydrogen sulfide and reduce at least part of the sulfur dioxide present in the thermal reduction effluent to hydrogen sulfide;
• and
• cooling the hydrolyzed thermal reduction effluent to about 118.degree. to 170.degree. C. to condense and separate elemental surface from the gases.