High temperature flue gas treatment

Claim 1

IN A METHOD OF TREATING AN EFFLUENT GAS CONTAINING A MINOR BUT POLLUTING AMOUNT OF BOTH SULFUR DIOXIDE AND SULFUR TRIROXIDE BY CONTACTING SAID EFFLUENT GAS WITH AMMONIA TO FORM AN AMMONIUM SALT OF A SULFUR OXIDE, THE IMPROVEMENT COMPRISING: INTRODUCING SAID AMMONIA IN GASEOUS FORM WHILE SAID EFFLUENT GAS IS AT A TEMPERATURE ABOVE ABOUT 220*F AND BELOW ABOUT 1200*F, AND IN AN AMOUNT AT LEAST SUFFICIENT TO REACT WITH ALL THE SULFUR TRIOXIDE BUT NOT MORE THAN THAT EQUIVALENT TO ABOUT 2.0 MOLS OF AMMONIA PER MOL OF TOTAL SULFUR OXIDES IN SAID EFFLUENT GAS TO THEREBY CONVERT SUBSTANTIALLY ALL OF THE SULFUR TRIOXIDE TO AMMONIUM MONOSULFATE AND TO CONVERT SULFUR DIOXIDE PREDOMINANTLY TO THE BI-SULFITE, UNDER TEMPERATURE CONDITIONS MINIMIZING OXIDATION OF SULFUR DIOXIDE TO TRIOXIDE, WHEREIN SAID AMMONIUM SALTS INCLUDE SALTS OF BOTH SULFUR DIOXIDE AND SULFUR TRIOXIDE, RECOVERING THE RESULTING NON-CAKING SOLID AMMONIUM SALTS OF SULFUR OXIDES FROM SAID EFFLUENT GAS AT A TEMPERATURE ABOVE ABOUT 220*F, TREATING SAID SALTS WITH AT LEAST THE STOICHIOMETRIC AMOUNT OF AN AQUEOUS MEMBER OF THE GROUP CONSISTING OF ALKALINE EARTH METAL OXIDE AND ZINC OXIDE TO LIBERATE AMMONIA FOR RECYCLE AND TO FORM ALKALINE EARTH METAL OR ZINC SULFUR OXIDE SALTS, AND DRYING, DEHYDRATING, AND THERMALLY DECOMPOSING SAID SALTS UNDER REDUCING CONDITIONS TO CONVERT THE SULFUR FROM HEXAVALENT TO TETRAVALENT SULFUR OXIDE AND THEREBY LIBERATE A STREAM OF SULFUR DIOXIDE AND TO RECOVER ALKALINE EARTH METAL OXIDE OR ZINC OXIDE FOR RECYCLE.