Process for the production of ferromanganese from high-grade manganese-bearing materials

Claim 1

A SINGLE STAGE SMELTING PROCESS FOR PRODUCING FERROMANGANESE FROM RELATIVELY HIGH-GRADE MANGANESEBEARING MATERIAL COMPRISING OXIDES OF MANGANESE, IRON, CALCIUM AND SILICA, THAT COMPRISES CALCINING THE MANGANESE-BEARING MATERIAL AT A TEMPERATURE CONTROLLED WITHIN THE RANGE 900-1200*C. TO STABILIZE THE SAME BY ELIMINATION OF WATER AND LABILE OXYGEN WITH THE PRODUCTION OF A SUBSTANTIALLY CONSTANT COMPOSITION REDUCTION BURDEN, PASSING THE HOT STABILIZED CHARGE THUS PRODUCED DIRECTLY INTO A COVERED OPEN-ARC ELECTRIC FURNACE AND ONTO THE SURFACE OF A MOLTEN SLAG BATH MAINTAINED THEREIN IN THE PRESENCE OF (1) REDUCING MATERIAL IN AN AMOUNT SUFFICIENT TO EFFECT REDUCTION OF THE IRON AND MANGANESE OXIDES OF THE MATERIAL TO THE METALLIC STATE, (2) ADDED CALCIUM OXIDE IN AN AMOUNT SUFFICIENT TO PROVIDE FOR THE PRODUCTION OF RESIDUAL SLAG COMPRISING SILICA AND BASIC OXIDES IN PROPORTIONS EQUAL TO ABOUT TWO MOLECULES OF BASIC OXIDE TO EACH MOLECULE OF SILICA, AND (3) IRON IN AN AMOUNT AS REQUIRED TO COMBINE WITH MANGANESE AND IRON NATURALLY PRESENT IN THE MATERIAL TO PRODUCE A DESIRED GRADE OF FERROMANGANESE, SMELTING THE CHARGE AT A TEMPERATURE CONTROLLED WITHIN THE RANGE 1300-1500* C. TO EFFECT REDUCTION TO THE METALLIC STATE OF THE IRON AND SUBSTANTIALLY ALL OF THE MANGANESE OXIDE OF THE MATERIAL BY MEANS OF SAID REDUCING MATERIAL WITH THE PRODUCTION OF A MOLTEN FERROMANGANESE PRODUCT AND MOLTEN RESIDUAL SLAG LOW IN IRON AND MANGANESE; AND SEPARATING AND RECOVERING THE FERROMANGANESE FROM THE RESIDUAL SLAG; SAID SMELTING TEMPERATURE BEING CONTROLLED WITHIN THE RANGE 1300-1500*C. DURING THE COURSE OF THE PROCESS AND VAPORIZATION OF MANGANESE BEING MINIMIZED BY (1) MAINTAINING THE ARCING TIPS OF THE FURNACE ELECTRODES BETWEEN ABOUT ONE-HALF INCH (1/2") FROM THE UPPER SURFACE OF THE MOLTEN SLAG BATH THERIN AND ABOUT THREE INCHES (3") BELOW THE UPPER SURFACE OF SAID MOLTEN SLAG BATH, (2) MAINTAINING A SUBSTANTIALLY CONSTANT RESISTANCE SLAG BATH WITHIN THE FURNACE BY CONTROLLING THE DEPTH OF MOLTEN SLAG, AND (3) INTRODUCING CHARGE MATERIAL INTO THE FURNACE AND ONTO THE SURFACE OF THE MOLTEN SLAG BATH THEREIN AT A RATE AND IN A DIRECTION CONTROLLED TO AVOID SUBSTANTIAL SUBMERGENCE OF THE ARCING TIPS OF THE ELECTRODES WITHIN RAW CHARGE MATERIAL.