Process for purifying a sulfur dioxide containing gas with production of elemental sulfur

Process for purifying SO2-containing gas comprising a first step of contacting said gas with an aqueous solution of an ammonium sulfite or an ammonium thiosulfate also containing ammonium sulfate, a second step of contacting the resulting solution with a H2S-containing gas at 20 DEG -90 DEG C. to produce sulfur which is separated from the remaining solution, a third step of recyling 90 to 99.99% by volume of said remaining solution to the first step, and a fourth step of introducing 0.01 to 10% by volume of said remaining solution into a molten salt formed of ammonium sulfate and/or bisulfate so as to produce a gas containing SO2, ammonia, sulfur and steam, which is recycled to the first step.