Beneficiation of low-grade hematitic ore materials

Claim 1

CYCLICAL PROCESS OF REDUCTIVELY ROASTING A FERRUGINOUS ORE MATERIAL TO CONVERT THE IRON CONTENT THEREOF TO MAGNETITE, WHICH COMPRISES ESTABLISHING A GRAVITATIONALLY DESCENDING COLUMN OF THE INITIALLY SUBSTANTIALLY UNHEATED ORE MATERIAL IN PARTICULATE FORM, REMOVING ROASTED ORE MATERIAL FROM THE BOTTOM OF THE COLUMN AND ADDING FRESH ORE MATERIAL TO BE ROASTED ONTO THE TOP OF THE COLUMN TO MAINTAIN THE LATTER''S HEIGHT, INTRODUCING INTO AND COUNTERCURRENTLY PASSING THROUGH THE COLUMN FROM SUBSTANTIALLY THE BOTTOM TO THE TOP THEREOF A REACTIVE GAS MIXTURE, INITIALLY AT ABOUT ROOM TEMPERATURE, CONTAINING CARBON DIOXIDE, INERT GASES AND A GASEOUS ACTIVE REDUCING AGENT SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, CARBON MONOXIDE AND A MIXTURE OF HYDROGEN AND CARBON MONOXIDE, THERE BEING PRESENT SUBSTANTIALLY MORE CARBON DIOXIDE THAN GASEOUS ACTIVE REDUCING AGENT, INTRODUCING INTO THE COLUMN, AT A LEVEL INTERMEDIATE THE TOP AND THE BOTTOM OF THE SAME AND SUBSTANTIALLY ABOVE THE LEVEL OF INTRODUCTION OF THE REACTIVE GAS MIXTURE, AND COUNTERCURRENTLY PASSING THROUGH THE REMAINDER OF THE COLUMN A SUBSTANTIALLY INERT, NON-OXIDING, HEATING GAS MIXTURE COMPRISING HOT GASEOUS PRODUCTS OF THE COMBUSTION OF A FLUID FUEL IN AIR, SAID HEATING GAS MIXTURE BEING INTRODUCED AT SUCH AN ELEVATED TEMPERATURE AND IN SUCH A VOLUME AS TO MAINTAIN THE ORE IN A MAXIUM TEMPERATURE ZONE IN THE UPPER PART OF THE COLUMN AT A TEMPERATURE OF FROM ABOUT 800* F. TO ABOUT 1,700*F., CLEANING AND COOLING A SUBSTANTIAL PART OF THE SPENT GAS MIXTURE ISSUING FROM THE TOP OF THE CHARGE COLUMN, ADDING TO A PORTION OF THE SAME A GAS RICH IN SAID GASEOUS ACTIVE REDUCING AGENT IN AN AMOUNT TO RECONSTITUTE THE AFORESAID REACTIVE GAS MIXTURE IN COMPOSITION AND IN VOLUME, USING THE LATTER AS THE REACTIVE GAS MIXTURE IN CONTINUATION OF THE PROCESS, BURNING A FLUID CARBONACEOUS FUEL IN AN AMOUNT OF AIR JUST SURFICIENT TO CONVERT THE COBUSTIBLE CONTENT OF THE FUEL TO CO2, MIXING WITH THE RESULTING HOT GASEOUS COMBUSTION PRODUCTS A FURTHER PORTION OF THE CLEANED AND COOLED SPENT GAS MIXTURE IN AN AMOUNT TO RECONSTITUTE SAID HEATING GAS MIXTURE, USING THE RESULTING HOT GAS MIXTURE AS THE SUBSTANTIALLY INERT, NON-OXIDING HEATING GAS MIXTURE IN CONTINUATION OF THE PROCESS, AND MAINTAINING THE VOLUME OF CIRCULATING GASES SUBSTANTIALLY CONSTANT BY DIVERTING A MINOR PART OF SAID SPENT GAS MIXTURE FROM THE CYCLE.