THE IMPORTANCE OF COKE QUALITY IN A SUBMERGED ARC ELECTRIC FURNACE FOR THE PRODUCTION OF FERROALLOYS

In the production of ferroalloys under production conditions, it is necessary to minimize the specific consumption of electrical energy. Its consumption depends mainly on the reactions occurring in the pre-reduction zone, while stable operation is determined by the size of the coke bed and the chemical reactions occurring there. Schematically, the ferroalloy furnace is divided into four zones and the main chemical reactions occurring there are shown. In the coke bed zone, chemical reactions of direct reduction of oxides occur, in the zones below - ore and fluxes are in a liquid state, mixed with coke. The amount of CO formed by direct reduction of MnO in the coke bed is sufficient for direct reduction of almost all higher manganese oxides and iron oxides present in the pre-reduction zone. Thus, the reducibility of the ore affects the rate of indirect reduction. Heterogeneous (gas-solid) reactions occurring in the pre-reduction zone of the furnace have a large impact on the total consumption of coke and electricity in the production of manganese alloys. The reduction of Mn3O4 to MnO can occur in parallel with the Boudoir reaction, while the reduction of MnO2 to Mn3O4 occurs at temperatures below the gasification threshold of the coke. The reactivity of the coke is a very important criterion for the selection of a reducing agent for use in an electric furnace for the production of ferroalloys, as it affects the specific carbon content and energy intensity of the process. The most common test in industrial practice is the Japanese test called CRI/CSR (coke reactivity index and coke strength after reaction). The reducing agent used for the production of ferroalloys should be more reactive than that used in the blast furnace. The intrinsic properties of the carbon reducing agent have a large influence on its reactivity, the isotropic microtextures of semi-coke being more reactive.