Process for purifying a gas containing oxygenated sulfur compounds and recovering sulfur using ammonia liquors

Claim 1

A PROCESS FOR REMOVING SULFUR DIOXIDE FROM A GAS CONTAINING IT, WHEREIN THE GAS IS CONTACTED WITH AMMONIA AND WATER AT A TEMPERATURE OF FROM 30* TO 80*C SO AS TO OBTAIN A SOLUTION OF AMMONIUM SULFITES IN WHICH THE MOLAR RATIO OF H2O TO AMMONIUM SULFITES (EXPRESSED AS SO2) IS FROM 11 : 1 TO 100 : 1, THE SOLUTION IS CONCENTRATED IN A CONCENTRATION ZONE BY EVAPORATING WATER AT A TEMPERATURE LOWER THAN 100*C SO AS TO OBTAIN A MOLAR RATIO OF H2O TO SO2 OF 4 : 1 TO 10 : 1, THE RESULTING CONCENTRATED SOLUTION IS HEATED UP TO 105*-200:C SO AS TO CONVERT AT LEAST THE MAJOR PORTION OF THE AMMONIUM SULFITES THEREIN INTO A GAS MIXTURE OF SULFUR DIOXIDE, AMMONIA AND STEAM, AND SO AS TO PRODUCE A MORE CONCENTRATED RESIDUAL SOLUTION CONTAINING AMMONIUM SULFATES, SAID RESIDUAL SOLUTION BEING DISCHARGED FROM THE PROCESS, SAID GAS MIXTURE IS THEN PASSED WITH HYDROGEN SULFIDE THROUGH A LIQUID PHASE CONSISTING ESSENTIALLY OF AN ORGANIC SOLVENT, AT A TEMPERATURE OF FROM 120* TO 170*C, SO AS TO PRODUCE SULFUR, SAID SULFUR AND A GAS PHASE CONSISTING ESSENTIALLY OF STEAM AND AMMONIA ARE SEPARATED FROM THE LIQUID PHASE, AND AMMONIA IS RECIRCULATED THROUGH THE ZONE OF CONTACT WITH THE SULFUR DIOXIDE CONTAINING GAS.