Removal of sulfur dioxide from gases containing sulfur dioxide and oxygen

Claim 1

IN A PROCESS FOR REMOVING SULFUR DIOXIDE FROM A GAS STREAM CONTAINING SO2 AND 32 IN WHICH SAID GAS STREAM IS CONTACTED IN A SCRUBBER WITH AN AQUEOUS SOLUTION CONTAINING A SULFITEFORMING REAGENT SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL HYDROXIDES AND CARBONATES AND AMMONIUM HYDROXIDE AND CORBONATE IN AT LEAST THE AMOUNT REQUIRED TO CONVERT THE PROMOTE REACTION OF THE SO2 WITH THE SULFITE-FORMING REAGENT, TO THEREBY YIELD AN EFFLUENT GAS STREAM OF REDUCED FULFUR DIOXIDE CONTENT AND AN EFFLUENT AQUEOUS SOLUTION CONTAINING ALKALI METAL OR AMMONIUM SULFITE, THE IMPROVEMENT WHICH COMPRISES: A. INTRODUCING FRESH AQUEOUS SCRUBBING SOLUTION INTO SAID SCRUBBER WHICH CONTAINS, IN ADDITION TO SAID SULFITE-FORMING REAGENT, AT LEAST 15 PERCENT BY WEIGHT OF AN ALKALI METAL OR AMMONIUM THIOSULFATE, AND THEREAFTER B. OPERATING THE SCRUBBER AT CONDITIONS SELECTED TO MAINTAIN THE PH OF THE SOLUTION LEAVING THE SCRUBBER BETWEEN 6.3 AND 8.0, AND TO YIELD AN EFFLUENT GAS STREAM WHICH IS SUBSTANTIALLY FREE OF SO2 AND AN EFFLUENT AQUEOUS SCRUBBING SOLUTION WHICH CONTAINS SUBSTANTIALLY ALL THE SULFITE PRODUCED IN THE SCRUBBER BY THE REACTION OF SO2 AND THE SULFITE-FORMING REAGENT.