Method of recovering ferrochromium

Claim 1

THE METHOD OF PRODUCING FERROCHROMIUM OF CONTROLLED CARBON CONTENT WHICH COMPRISES SMELTING A CHARGE COMPRISING CHROMITE ORE IN A THREE-PHASE SUBMERGED ARC ELECTRIC FURNACE IN THE PRESENCE OF AN AMOUNT OF CARBON SUFFICIENT TO EFFECT REDUCTION TO THE METALLIC STATE OF SUBSTANTIALLY ALL OF THE IRON OF THE CHROMITE ORE BUT INSUFFICIENT TO EFFECT REDUCTION TO THE METALLIC STATE OF ALL OF THE IRON AND ALL OF THE CHROMIUM OF THE CHROMITE ORE AND FORMING A MOLTEN PRODUCT CONTAINING MOLTEN METAL AND MOLTEN SLAG CONTAINING IN OXIDE FORM THE UNREDUCED CHROMIUM OF THE CHROMITE ORE, INTRODUCING THE MOLTEN PRODUCT THUS PRODUCED, INCLUDING THE MOLTEN METAL AND THE MOLTEN SLAG, INTO AN OPEN-ARC ELECTRIC FURNACE TO FORM THEREIN A MOLTEN BATH COMPRISING MOLTEN METAL COVERED BY A LAYER OF MOLTEN SLAG, PLACING ON THE SURFACE OF THE LAYER OF MOLTEN SLAG, AT POINTS REMOTE FROM THE ARCING ZONES OF THE FURNACE ELECTRODES, FINELY DIVIDED SOLID CARBONACEOUS MATERIAL AND MAINTAINING THE LAYER OF MOLTEN SLAG BY MEANS OF COMBINED ELECTRIC ARC AND RESISTANCE HEATING AT A TEMPERATURE SUFFICIENTLY HIGH TO PROMOTE AND EFFECT REDUCTION TO THE METALLIC STATE OF THE CHROMIUM OF THE CHROMIUM OXIDE CONTAINED IN THE SLAG AND PERMIT THE METALLIC CHROMIUM THUS PRODUCED TO PASS DOWNWARDLY THROUGH THE RESIDUAL MOLTEN SLAG AND ENTER THE MOLTEN METAL BENEATH THE SLAG WITH THE PRODUCTION OF MOLTEN FERROCHROMIUM CONTAINING IRON AND CHROMIUM OF THE ORIGINAL CHROMITE ORE, AND SEPARATING THE FERROCHROMIUM FROM THE RESIDUAL SLAG.

Claim 2

THE METHOD OF PRODUCING FERROCHROMIUM OF CONTROLLED CARBON CONTENT WHICH COMPRISES SMELTING A CHARGE COMPRISING CHROMITE ORE IN A THREE-PHASE SUBMERGED ARC ELECTRIC FURNACE IN THE PRESENCE OF AN AMOUNT OF CARBON SUFFICIENT TO EFFECT REDUCTION TO THE METALLIC STATE OF SUBSTANTIALLY ALL OF THE IRON OF THE CHROMITE ORE BUT INSUFFICIENT TO EFFECT REDUCTION TO THE METALLIC STATE OF ALL OF THE IRON AND ALL OF THE CHROMIUM OF THE CHROMITE ORE AND FORMING A MOLTEN PRODUCT CONTAINING MOLTEN METAL AND MOLTEN SLAG CONTAINING IN OXIDE FORM THE UNREDUCED CHROMIUM OF THE CHROMITE ORE, INTRODUCING THE MOLTEN PRODUCT THUS PRODUCED, INCLUDING THE MOLTEN METAL AND THE MOLTEN SLAG, INTO AN OPEN-ARC ELECTRIC FURNACE TO FORM THEREIN A MOLTEN BATH COMPRISING MOLTEN METAL COVERED BY A LAYER OF MOLTEN SLAG, PLACING ON THE SURFACE OF THE LAYER OF MOLTEN SLAG, AT POINTS REMOTE FROM THE ARCING ZONES OF THE FURNACE ELECTRODES, FINELY DIVIDED SOLID CARBONACEOUS MATERIAL AND MAINTAINING THE LAYER OF MOLTEN SLAG BY MEANS OF COMBINED ELECTRIC ARC AND RESISTANCE HEATING AT A TEMPERATURE SUFFICIENTLY HIGH TO PROMOTE AND EFFECT REDUCTION TO THE METALLIC STATE OF THE CHROMIUM OF THE CHROMIUM OXIDE CONTAINED IN THE SLAG AND PERMIT THE METALLIC CHROMIUM THUS PRODUCED TO PASS DOWNWARDLY THROUGH THE RESIDUAL MOLTEN SLAG AND ENTER THE MOLTEN METAL BENEATH THE SLAG WITH THE PRODUCTION OF MOLTEN FERROCHROMIUM CONTAINING IRON AND CHROMIUM OF THE ORIGINAL CHROMITE ORE, AND SEPARATING THE FERROCHROMIUM FROM THE RESIDUAL SLAG.