Recovering magnesium-aluminum spinel from ferro-chromium slag

Claim 1

A PROCESS FOR BENEFICIATING HIGH CARBON FERROCHROMIUM SLAG BY REMOVING SILICA AND RECOVERING MAGNESIUMALUMINUM SPINEL-CONTAINING MATERIAL THEREFROM SUBSTANTIALLY FREE FROM METALLIC IMPURITIES, SAID PROCESS COMPRISING MIXING HIGH CARBON FERROCHROMIUM SLAG WITH IRON AND CARBON AND SUFFICIENT ALUMINUM OXIDE AND MAGNESIUM OXIDE TO PROVIDE A REACTION MIXTURE HAVING A MAGNESIUM OXIDE TO ALUMINUM OXIDE RATIO, BY WEIGHT, MEASURED AS MGO AND AL2O3, OF BETWEEN ABOUT 0.67 AND 1.1 AND HAVING A CAO CONTENT OF LESS THAN 3 PER CENT, THE CARBON IN THE MIXTURE BEING IN AT LEAST THE AMOUNT SUFFICIENT TO COMPLETELY REDUCE ALL SILICA CONTAINED IN THE REACTION MIXTURE UPON THE HEATING OF THE REACTION MIXTURE TO AN ELEVATED TEMPERATURE AND THE IRON IN THE REACTION MIXTURE BEING IN AN AMOUNT SUFFICIENT TO COMBINE WITH ALL SILICON AND CARBON-REDUCIBLE METALLIC IMPURITIES CONTAINED IN THE REACTION MIXTURE TO PROVIDE A FERROSILICON MATERIAL CONTAINING AT LEAST ABOUT 75 PERCENT IRON; HEATING THE REACTION MIXTURE TO A TEMPERATURE AT WHICH THE REACTION MIXTURE IS IN A CONDITION INTERMEDIATE ITS SOLIDUS AND LIQUIDUS STATES; MAINTAINING THE REACTION MIXTURE IN THIS INTERMEDIATE CONDITION UNTIL SUBSTANTIALLY ALL OF THE SILICA IN THE REACTION MIXTURE HAS BEEN REDUCED AND UNTIL THE MIXTURE IS SUBSTANTIALLY FREE FROM UNCOMBINED CARBON; SUBSEQUENTLY INCREASING THE TEMPERATURE TO A VALUE AT WHICH THE MIXTURE IS IN THE LIQUIDS STATE TO THEREBY COAGULATE THE METALLIC MATERIAL IN THE MIXTURE AND PROVIDE DISTINCT METALLIC AND NON-METALLIC PHASES; AND SEPARATING THE NON-METALLIC SPINEL PHASE FROM THE MIXTURE.