Conversion of hydrogen sulfide into free sulfur

Claim 1

IN A PROCESS FOR THE RECOVERY OF FREE SULFUR FROM A GAS CONTAINING AT LEAST 10 TO 15 PERCENT HYDROGEN SULFIDE BY THE REACTION OF A HYDROGEN SULFIDE-SULFUR DIOXIDE MIXTURE IN THE PRESENCE OF A CATALYST IN A REACTION ZONE AT AN INITIAL TEMPERATURE IN THE RANGE OF FORM ABOUT 400* TO ABOUT 500*F. WHEREIN SAID MIXTURE IS PREPARED BY BURNING SAID GAS IN THE PRESENCE OF SUFFICIENT OXYGEN TO CONVERT APPROXIMATELY ONE-THIRD OF SAID HYDROGEN SULFIDE TO SULFUR DIOXIDE IN A COMBUSTION ZONE WHEREIN THE TEMPERATURE OF THE EFFIUENT GAS FROM SAID COMBUSTION ZONE RANGES FROM ABOUT 350* TO BELOW 400*F., THE METHOD OF CONTROLLING THE REACTION TEMPERATURE IN SAID REACTION ZONE WHICH COMPRISES FIRST OXIDIZING IN SAID COMBUSTION ZONE FROM ABOUT 25.6 TO ABOUT 32.5 PRECENT OF THE HYDROGEN SULFIDE IN SAID GAS TO SULFUR DIOXIDE, WITHDRAWING THE RESULTING MIXTURE FROM SAID COMBUSTION ZONE, NEXT INJECTING OXYGEN INTO SAID RESULTING MIXTURE IN AN AMOUNT REANGING FROM ABOUT 2 TO ABOUT 12 PERCENT OF THE THEORETICAL OXYGEN REQUIRED TO GIVE A MIXTURE CONTAINING HYDROGEN SULFIDE AND SULFUR DIOXIDE IN A MOLAR RATIO OF ABOUT 2:1, AND THEREAFTER INJECTING THE MIXTURE THUS FORMED HAVING SAID RATIO INTO SAID REACTION ZONE TO PRODUCE A REACTION TEMPERATURE OF FROM 400* TO ABOUT 500*F.