The reduction smelting of ferromanganese is divided into two methods: flux method (low manganese slag method) and flux free method (high manganese slag method).The flux method is based on the same principles as blast furnace smelting except that electric energy replaces the heating coke.High alkali slag (CaO/SiO2 between 1.3 and 1.6) was formed by adding lime to reduce the loss of manganese.Without the addition of lime in the fluidization process, low alkalinity (CaO/SiO2 < 1.0) and high content of low iron, low phosphorus and manganese rich slag were formed.This method has a low amount of slag, which can reduce the power consumption and reduce the evaporation loss of manganese due to the low temperature of slag. At the same time, the byproduct manganese rich slag (containing 25~40% manganese) can be used as the raw material for smelting manganese silicon alloy, and higher comprehensive recovery rate of manganese (over 90%) can be achieved.Modern industrial production mostly USES the flux free method to smelt the carbon ferromanganese, and with the manganese silicon alloy and the low carbon ferromanganese smelting composition joint production.
Electric furnace refining
The medium and low carbon ferromanganese are usually refined by the electric furnace of 1500~6000 kva.
The reaction is: MnSi + mno 2 + 2 cao ─ - > 3 mn + 2 cao, SiO2
High alkalinity slag can reduce the content of manganese and reduce the loss of manganese caused by waste slag.Low slag alkalinity (CaO/SiO2 less than 1.3) was used in the combined production, and the slag containing high manganese (20~30%) was used to smelt the manganese silicon alloy.Preheating or loading liquid manganese-silicon alloy can shorten smelting time and reduce power consumption.The refined power consumption is usually around 1000 kw.Medium and low carbon ferromanganese are also produced by thermal blending of liquid manganese-silicon alloy, manganese ore and lime melt.