Sulfur dioxide reduction process

A process for simultaneously reducing sulfur dioxide to elemental sulfur and an alkali metal sulfate to an alkali metal sulfide which comprises:

• providing a reaction zone containing a molten salt comprising an alkali metal sulfide;
• introducing into said reaction zone gaseous sulfur dioxide, solid alkali metal sulfate, solid carbonaceous material and oxygen;
• reacting the sulfur dioxide and carbonaceous material to produce gaseous elemental sulfur and gaseous sulfur compounds;
• reacting the alkali metal sulfate and carbonaceous material to produce an alkali metal sulfide;
• withdrawing a gaseous product stream containing elemental sulfur, gaseous sulfur compounds, carbon dioxide and carbon monoxide from said reaction zone;
• cooling said gaseous product stream to condense elemental sulfur therefrom;
• reheating said gaseous product stream from which sulfur has been condensed and passing it through a catalyst bed to convert a portion of said gaseous sulfur compounds into elemental sulfur;
• condensing additional elemental sulfur from the converted gaseous product stream;
• repeating the reheating, catalytic conversion and sulfur condensation steps to provide a gas containing less than about 15% of the sulfur contained in the original sulfur dioxide feed;
• removing a portion of the molten salt from said reaction zone;
• and
• quenching said removed molten salt in an aqueous bath to produce a solution comprising an alkali metal sulfide;
• said oxygen being introduced into said reaction zone in an amount sufficient to maintain the temperature of the reaction zone above the melting point of the salts contained therein by oxidizing a portion of said carbonaceous material, but not sufficient to also oxidize the carbonaceous material required for the reduction of sulfur dioxide to elemental sulfur and the reduction of the alkali metal sulfate to alkali metal sulfide.