Method for removing arsenic from arsenopyrite ores

Claim 1

A METHOD FOR ROASTING PYRITE ORES CONTAINING ARSENIC COMPRISING THE STEPS OF AUTOGENOUSLY ROASTING SAID ORES IN AN OXYGEN DEFICIENT ATMOSPHERE IN A FIRST FLUIDIZED TREATMENT ZONE TO PRODUCE VOLATILE ARSENIC PRODUCTS, SULFUR GASES AND PARTIALLY ROASTED IRON SULFIDES, REMOVING SAID VOLATILIZED ARSENIC PRODUCTS FROM SAID FIRST TREATMENT ZONE WITH THE EXITING FLUIDIZING GASES, DISCHARGING SOLIDS FROM SAID FIRST FLUIDIZED TREATMENT ZONE TO A SECOND FLUIDIZED TREATMENT ZONE, MAINTAINING AN ATMOSPHERE OF EXCESS FREE OXYGEN WITHIN SAID SECOND FLUIDIZED TREATMENT ZONE, AUTOGENOUSLY ROASTING SAID SOLIDS IN SAID SECOND TREATMENT ZONE TO PRODUCE FERRIC OXIDE AND SULFUR DIOXIDE, DISCHARGING ROASTED SOLIDS FROM SAID SECOND FLUIDIZED TREATMENT ZONE, CONDUCTING SAID EXITING GASES FROM SAID FIRST TREATMENT ZONE TO A DUST SEPARATOR, THE IMPROVEMENT WHICH COMPRISES: MAINTAINING SAID DUST SEPARATOR AT TEMPERATURES IN EXCESS OF THE CONDENSATION TEMPERATURE OF SAID VOLATILIZED ARSENIC PRODUCTS CONTAINED IN SAID EXITING GASES, CONDUCTING SOLIDS SEPARATED IN SAID DUST SEPARATOR TO SAID SECOND TREATMENT ZONE, CONDUCTING EFFLUENT GASES FROM SAID DUST SEPARATOR TO A COMBUSTION CHAMBER, INTRODUCING SUFFICIENT FREE OXYGEN SUBSTANTIALLY ALL VOLATILE COMBUSTION CHAMBER TO OXIDIZE SUBSTANTIALLY ALL VOLATILE ARSENIC PRODUCTS CONTAINED IN SAID EFFLUENT GASES TO SOLID ARSENIC COMPOUNDS AND ALL ELEMENTAL SULFUR AND SULFIDE SULFUR IN SAID EFFLUENT GASES TO SULFUR DIOXIDE, TRANSFERRING THE COMBUSTION PRODUCTS COMPRISING SULFUR DIOXIDE AND SOLID ARSENIC COMPOUNDS FROM SAID COMBUSTION CHAMBER TO A GAS SCRUBBING STAGE TO EFFECT SEPARATION OF SAID SOLID ARSENIC COMPOUNDS FROM THE GASEOUS SULFUR DIOXIDE WHEREBY SUBSTANTIALLY ARSENIC FREE SULFUR DIOXIDE IS RECOVERED AND THE IRON CONTENT OF SAID PYRITE ORES CONTAINING ARSENIC IS RECOVERED AS FERRIC OXIDE SUBSTANTIALLY FREE OF ARSENIC AND SUITABLY CONDITIONED FOR BLAST FURNACE FEED.

Claim 2

A METHOD FOR ROASTING PYRITE ORES CONTAINING ARSENIC COMPRISING THE STEPS OF AUTOGENOUSLY ROASTING SAID ORES IN AN OXYGEN DEFICIENT ATMOSPHERE IN A FIRST FLUIDIZED TREATMENT ZONE TO PRODUCE VOLATILE ARSENIC PRODUCTS, SULFUR GASES AND PARTIALLY ROASTED IRON SULFIDES, REMOVING SAID VOLATILIZED ARSENIC PRODUCTS FROM SAID FIRST TREATMENT ZONE WITH THE EXITING FLUIDIZING GASES, DISCHARGING SOLIDS FROM SAID FIRST FLUIDIZED TREATMENT ZONE TO A SECOND FLUIDIZED TREATMENT ZONE, MAINTAINING AN ATMOSPHERE OF EXCESS FREE OXYGEN WITHIN SAID SECOND FLUIDIZED TREATMENT ZONE, AUTOGENOUSLY ROASTING SAID SOLIDS IN SAID SECOND TREATMENT ZONE TO PRODUCE FERRIC OXIDE AND SULFUR DIOXIDE, DISCHARGING ROASTED SOLIDS FROM SAID SECOND FLUIDIZED TREATMENT ZONE, CONDUCTING SAID EXITING GASES FROM SAID FIRST TREATMENT ZONE TO A DUST SEPARATOR, THE IMPROVEMENT WHICH COMPRISES: MAINTAINING SAID DUST SEPARATOR AT TEMPERATURES IN EXCESS OF THE CONDENSATION TEMPERATURE OF SAID VOLATILIZED ARSENIC PRODUCTS CONTAINED IN SAID EXITING GASES, CONDUCTING SOLIDS SEPARATED IN SAID DUST SEPARATOR TO SAID SECOND TREATMENT ZONE, CONDUCTING EFFLUENT GASES FROM SAID DUST SEPARATOR TO A COMBUSTION CHAMBER, INTRODUCING SUFFICIENT FREE OXYGEN SUBSTANTIALLY ALL VOLATILE COMBUSTION CHAMBER TO OXIDIZE SUBSTANTIALLY ALL VOLATILE ARSENIC PRODUCTS CONTAINED IN SAID EFFLUENT GASES TO SOLID ARSENIC COMPOUNDS AND ALL ELEMENTAL SULFUR AND SULFIDE SULFUR IN SAID EFFLUENT GASES TO SULFUR DIOXIDE, TRANSFERRING THE COMBUSTION PRODUCTS COMPRISING SULFUR DIOXIDE AND SOLID ARSENIC COMPOUNDS FROM SAID COMBUSTION CHAMBER TO A GAS SCRUBBING STAGE TO EFFECT SEPARATION OF SAID SOLID ARSENIC COMPOUNDS FROM THE GASEOUS SULFUR DIOXIDE WHEREBY SUBSTANTIALLY ARSENIC FREE SULFUR DIOXIDE IS RECOVERED AND THE IRON CONTENT OF SAID PYRITE ORES CONTAINING ARSENIC IS RECOVERED AS FERRIC OXIDE SUBSTANTIALLY FREE OF ARSENIC AND SUITABLY CONDITIONED FOR BLAST FURNACE FEED.