Process for magnetically roasting hematitic ore and ore materials

Claim 1

PROCESS OF MAGNETICALLY ROASTING A FERRUGINOUS ORE MATERIAL WHOSE IRON CONTENT OCCURS MOSTLY IN THE FERRIC STATE WHEREBY TO CONVERT AT LEAST THE MAJOR PORTION OF THE FERRIC OXIDE CONTENT THEREOF TO MAGNETITE, WHICH COMPRISES REPEATEDLY CIRCULATING A STREAM OF MIXED NON-OXIDIZING GAS THROUGH A REENTRANT CIRCUIT CONTAINING A MASS OF THE ORE MATERIAL AT AN ELEVATED TEMPERATURE BETWEEN 500*F. AND THE LIQUIDUS POINT OF THE ORE MATERIAL, THE MIXED GAS CONSISTING ESSENTIALLY OF NITROGEN, CO2, H2O AND CO, THE RATIO OF CO2 TO THE SUM OF THE CO2 AND CO IN SAID MIXED GAS BEING MAINTAINED AT A VALUE ABOVE THE LINE "B A" IN THE EQUILIBRIUM DIAGRAM FOR THE TERNARY SYSTEM FE-C-O REPRESENTED IN FIG. 1 OF THE ACCOMPANYING DRAWING; AFTER EACH PASSAGE THROUGH SAID MASS OF ORE MATERIAL RECONSTITUTING THE ORIGINAL COMPOSITION AND VOLUME OF THE MIXED GAS BY DISCARDING A MINOR FRACTION OF THE MIXED GAS AND ADDING TO THE RESIDUE A LIKE AMOUNT OF A GAS CONTAINING NITROGEN AND CO2 AND BEING RICH IN CO, THE AMOUNT OF CO SO ADDED BEING FROM ABOUT 0.6 TO A LITTLE IN EXCESS OF 1.12 CU. FT. OF CO PER EACH 1 POUND OF FE CONTENT IN THE ORE MATERIAL TREATED; HEATING THE MIXED GAS, PRIOR TO EACH PASSAGE THEREOF THROUGH SAID MASS OF ORE MATERIAL TO A TEMPERATURE BETWEEN 500*F. AND THE LIQUIDUS POINT OF THE ORE MATERIAL; AND MAINTAINING THE MASS OF ORE MATERIAL AT A TEMPERATURE BETWEEN 500*F. AND THE LIQUIDUS POINT OF THE ORE MATERIAL BY HEAT TRANSFERRED THERETO FROM SAID HEATED MIXED GAS, THE VOLUME OF THE MIXED GAS BEING ADJUSTED, BETWEEN 5 AND 30 CU. FT. PER EACH 1 POUND OF THE ORE MATERIAL TREATED, TO HAVE A HEAT CAPACITY SUFFICIENT TO INSURE THAT THE MASS OF ORE MATERIAL IS HEATED TO SUCH ELEVATED TEMPERATURE.