Optimization of dolomite usage in iron ore sintering process

Abstract

To achieve the action mechanism and optimal usage of dolomite in the sintering process, solid reaction tests, fluidity tests, bonding strength tests and sinter pot tests were conducted, then microstructure and energy spectrum were analysed further. Reaction temperature of dolomite with calcium ferrite was lower than that with limonite iron ore about 155° C. Fluidity of bonding phase and strength of sinter using dolomite were lower than that using light burned dolomite and serpentine owing to the higher MgO content in the calcium ferrite and formation of secondary bonding phase. Action mechanism of dolomite in sintering process mainly included 4 steps, thermal decomposition, solid reaction, formation of primary bonding phase and formation of secondary bonding phase. Dolomite mainly played it's role in the third step in which high viscosity CFM (calcium ferrite with MgO) and magnetite solid solution formed. Increasing the solid solubility of MgO in magnetite by mixing dolomite with magnetite concentrate before granulation, decreasing the dispersity of MgO in sinter mixture by increasing the particle size of dolomite appropriately, increasing the separation degree of MgO and CaO by light-burning the dolomite, and decreasing the reaction amount of MgO by using big particle size magnesia, all could decrease the content of MgO in calcium ferrite, thus showed good performance in sinter pot tests.