Pelletized iron ore concentrate composition and process for making the same

Claim 1

IN THE PROCESS OF PELLETIZING IRON CORE CONCENTRATES, THE PARTICLES OF WHICH ARE ESSENTIALLY ALL FINER THAN MINUS 100 MESH AND INCLUDE A LARGE PROPORTION OF MATERIAL FINER THAN 325 MESH, IN WHICH CONCENTRATE THE IRON OXIDES ARE ASSOCIATED WITH GANGUE MATERIAL INCLUDING ACIDIC COMPONENTS IN EXCESS OF THE COMBINED PROPORTION OF ITS BASIC COMPONENTS, ACCORDING TO WHICH PELLETIZING PROCESS A MOIST CONCENTRATE IS HOMOGENEOUSLY ADMIXED WITH FINELY DIVIDED SOLID CARBONACEOUS FUEL AND BENTONITE AND THE MIXTURE IS FORMED INTO PELLETS AND THE PELLETS ARE INDURATED AT AN ELEVATED TEMPERATURE IN EXCESS OF 1832*F., THE IMPROVEMENT WHICH CONSISTS IN HOMOGENEOUSLY ADMIXING WITH THE MOIST CONCENTRATE, PRIOR TO BALLING, A FINELY DIVIDED ALKALINE EARTH METAL CARBONATE ROCK THE PARTICLES OF WHICH ARE ALL MINUS 28 MESH, THE AMOUNT OF SUCH ADDED CARBONATE ROCK BEING SUCH AS TO YIELD, UPON CALCINATION THEREOF, A SLAG-FORMING BASIC REAGENT IN AN AMOUNT SUFFICIENT TO SLAG ALL OF SAID EXCESS ACIDIC COMPONENTS, AND HEAT-TREATING THE RESULTING DISCRETE PELLETS BY CONTACTING A MASS OF THE DISCRETE PELLETS WITH A STREAM OF FREE OXYGEN-CONTAINING HEATING GAS INTRODUCED INTO THE PELLETS MASS AT A TEMPERATURE OF FROM ABOUT 2000* TO ABOUT 2100*F., THE HEAT-TREATMENT BEING CONTINUED FOR A PERIOD SUFFICIENT TO EFFECT (A) THE COMPLETE CALCINATION OF THE CARBONATE ROCK AND (B) SUBSTANTIALLY COMPLETE COMBINATION OF THE CALCINED MATERIAL WITH ALL OF THE ACIDIC COMPONENTS OF THE PELLETS THEREBY SUBSTANTIALLY COMPLETELY PRE-SLAGGING THE GANGUE CONSTITUENTS OF THE PELLETS TO THE PRODUCTION OF MECHINICALLY STRONG AND RUGGED SELF-FLUXING IRON OXIDE CONCENTRATE PELLETS.