Experimental Study On The Preparation Of Ferromanganese Alloy By Selective Reduction-Smelting Of Low-Grade Ferromanganese Ore

Ferromanganese alloy is one necessary product in iron and steel production,which can act as an excellent deoxidizer and alloy additive in the steelmaking process.The supply of manganese ore in China is heavily dependent on imports with its relatively deficient manganese ore resources but large demands.Currently,the blast furnace process for smelting manganese ore requires high investment and high energy consumption.Besides,its products contain plenty of impurities.The selective reduction-magnetic separation process based on direct reduction with coal has the advantages of high efficiency,low consumption and cleaning production,it can also be combined with smelting process to remove impurities and prepare ferromanganese alloy.Experimental study on the preparations of ferromanganese alloy by selective reduction of low-grade ferromanganese ore was put forword in this paper based on the resources and technical conditions in China.Firstly,thermomechanical analysis was conducted to obtain the thermodynamics of selective reduction and smelting proces.Secondly,the selective reduction-magnetic separation process was investigated.The effects of reduction temperature,reduction time,carbon addition ratio,ferromanganese ore particle size and intensity of magnetic separation on selective reduction-magnetic separation indexes were researched.Finally,the preparations of ferromanganese alloy by smelting process were investigated.The effects of binary basicity,carbon coefficient,smelting time and smelting temperature on the smelting preparation of ferromanganese alloy and ferromanganese alloy which meets the requirements of industry were obtained.Through the above research,the following conclusions are drawn.(1)The thermodynamic analysis shows that the reduction of manganese oxides is followed by the successive reduction principle.The selective reduction of manganese and iron can be realized by controlling the reduction temperature at 737?1407?.Mn7C3 and Mn3C are more easily generated when manganese oxide is reduced by carbon;(2)Selective reduction-magnetic separation optimization process parameters:reduction time 6 h,reduction temperature 1050?,carbon addition ratio 2.5,ferromanganese ore particle size 8?13 mm,intensity of magnetic separation 75 mT.The recovery rate of manganese can reach 78.11%.Under these conditions,Mn/Fe and Mn contents in non-magnetic slag(manganous rich-slag)can reach 8.70 and 53.48%,respectively.The slag is a high quality material that meets the smelting requirement of ferromanganese;(3)During the selective reduction process,the transformation process of iron bearing phase is:Fe2O3?Fe3O4?FeO?Fe/FeO-Al2O3;The transformation process of manganese bearing phase is:MnO(OH)?Mn2O3?Mn3O4?Mno/MnO·SiO2;(Fe,Mn)2O3?Mn7SiO12?MnO/MnO·SiO2;(4)Optimization smelting process parameters include binary basicity 1.7,carbon coefficient 1.1,smelting time 60 min and smelting temperature 1550?.Under these conditions,the recovery ratio of manganese and iron are 75.47%and 97.70%.The Mn,TFe,C,Si,P and S contents in the ferrormanganese alloy are 76.76%,12.13%,6.73%,0.168%,0.14%,0.008%,respectively.The ferrormanganese alloy is high-quality high carbon ferromanganese superior to the corresponding indexes requirements of FeMn75C7.5,FeMn70C7.5,FeMn65C7.0.