Sezonenko O. Improvement of the three-stage technology and innovative processes of manganese ferroalloys smelting with silicon reduction

The thesis consists of theoretical and experimental studies, industrial implementation and commercialisation of three-stage technology and innovative processes of manganese ferroalloys smelting with silicon reduction in electric arc furnaces. Physical chemistry of the processes and different technologies economical data are compared and the importance of the silicon-reducing production method is analysed. New technology of high-carbon ferromanganese FMn78B (DSTU 3547-97) and intermediate manganese slag ShMP-78 is theoretically analysed for the conditions of JSC "ZFZ". This technology foresees substitution of expensive coke with Donetsk anthracite using retrofitted arc fur-naces RKO-7.0. For these processes thermodynamic analysis of manganese reduction by silicon from the slag ShMP-78 is performed for the conditions of metallic manganese and medium-carbon ferromanganese. The effect of MgO on stabilisation of ?-2CaO·SiO2 phase is analysed to prevent increased basicity slag from pulverisation. Processes slags compositions were studied with EMPA and MgO influence on lining stability of the arc furnaces was analysed. This lead to improvement of the periclase lining P96 instead of previous P91 that allowed extension of the furnace operations by 30-35% and improve productivity. In parallel stability of the chromite-periclase lining of lime production fur-naces was studied. The premature local melting of the lining was found to be caused by increased silica dust content in the offgas of ferrosilicon furnaces, which is used as additive to natural gas. Substitution of this lining to new periclase-chromite type was suggested. Altogether implementation of technology of manganese ferroalloys smelting with silicon reduction has allowed to decrease carbon consumption, specific electrical energy demand, improve furnace lining stability leading to economic effect of 37,687 mln. UAH with author's share of 7,238 mln. UAH.