System for producing carbonized and prereduced iron ore pellets

Claim 1

THE PROCESS OF MAKING HARDENED PREREDUCED DISCRETE UNCLINKERED PELLETS OF IRON ORE IN A DEEP, HIGH CAPACITY, MOVING BED WHICH CONTAINS FROM 15% TO 40% OF THE AVAILABLE IRON VALUES IN THE METALLIC STATE, AND WHICH INCLUDES THE STEPS OF: (A) FORMING A PARTICULATE MIXTURE OF SUBSTANTIALLY UNIFORM COMPOSITION AND CONSISTING ESSENTIALLY OF IRON ORE, A CARBONACEOUS MATERIAL, AND A FLUXING MATERIAL, THE AMOUNT OF CARBONACEOUS MATERIAL INCLUDING FIXED CARBON IN AN AMOUNT AT LEAST SUFFICIENT TO REDUCE 100% OF THE IRON OXIDE IN SAID ORE TO FREE METAL AND NOT IN EXCESS OF 120% OF SUCH AMOUNT; (B) FORMING MOISTENED PELLETS OF SAID MIXTURE, SAID PELLETS HAVING AN AVERAGE DIAMETER OF ABOUT MINUS 1.5 INCH PLUS 0.5 INCH; (C) CHARGING SAID MOISTENED PELLETS TO A TRAVELING GRATE TO FORM A DEEP BED HAVING A TOP AND BOTTOM SURFACE AND A DEPTH OF FROM 10 INCHES TO 20 INCHES; (D) DRYING SAID BED IN A DRYING ZONE BY PASSING HEATED GASES THERETHROUGH AT A TEMPERATURE OF FROM ABOUT 300*F. TO ABOUT 600*F., AND AT A RATE OF FROM ABOUT 200 TO ABOUT 300 S.C.F.M./SQ. FT. OF WINDBOX AREA; (E) CONVEYING THE RESULTING DRIED PELLET BED TO A CARBONIZING AND PREREDUCING ZONE; (F) HEATING SAID BED TO CARBONIZE AND PREREDUCE SAID PELLETS BY PASSING GASES THROUGH SAID BED FROM ONE SURFACE TO THE OTHER TO RAISE THE TEMPERATURE OF THE BED AT THE HEAT FRONT MOVING THERETHROUGH TO FROM 1800*F. TO 2200*F., THE EXTENT OF PREREDUCTION OF IRON OXIDE TO METALLIC IRON BEING FROM ABOUT 15% TO ABOUT 40% BY WEIGHT OF THE IRON VALUES IN THE PELLETS, SAID GASES PASSING THROUGH SAID BED AT A RATE OF FROM ABOUT 100 TO ABOUT 200 S.C.F.M./SQ. FT. OF WINDBOX AREA; AND (G) BEFORE THE HEAT FRONT COMPLETELY TRAVERSES THE BED FROM ONE SURFACE THEREOF TO THE OTHER PASSING GASES THROUGH THE BED FROM ONE SURFACE TO THE OTHER IN A DIRECTION OPPOSITE TO THE DIRECTION OF THE GASES IN THE NEXT PRECEDING STEP TO INITIATE AN OPPOSITELY DIRECTED AND MOVING CARBONIZING AND PREREDUCING HEAT FRONT, WHEREBY THE EXTENT OF CARBONIZATION AND PREREDUCTION OF THE PELLETS THROUGHOUT THE BED IS SUBSTANTIALLY THE SAME AND REOXIDATION OF METALLIC IRON IS MAINTAINED AT A MINIMUM.