| Description |
A novel flash ironmaking technology is being developed at University of Utah aiming at producing iron directly from magnetite concentrate (< 100 μm) using natural gas in a flash suspension reactor in the temperature range 1150-1600 °C. Natural gas is partially oxidized with oxygen generating a reducing gas mixture of H2 and CO as well as the heat required for the reaction. This process will eliminate cokemaking, pelletization, and sintering steps, decreasing the energy requirement for the ironmaking process. The kinetics of the reduction of magnetite concentrate to iron by H2, CO, and H2+CO mixtures were investigated in the temperature range 1150-1600 °C. Complete rate equations were formulated, and the effects of temperature, reducing gas partial pressures, and particle size were investigated. The nucleation and growth model was used to develop the rate equations. For reduction by H2 only, Avrami parameter n = 1 and first-order dependence on hydrogen partial pressure was obtained. The reduction rate by CO was much slower than that by H2 with Avrami parameter n = 0.5 and first-order dependence on CO partial pressure. The rate equations for reduction by the mixture were developed using the developed rate equations of individual gases. A laboratory scale flash reactor was built where iron concentrate was reduced by a reducing gas mixture generated from the partial oxidation of methane and/or hydrogen with pure oxygen. Magnetite reduction degree > 90% was achieved at a temperature as iv low as 1175 °C in a few seconds of residence time. The results obtained from this reactor was verified by the developed rate equations and good agreement was achieved. A Larger Scale Bench Reactor (LSBR) was installed in which heat and reductants were generated by a natural gas/oxygen flame in the temperature range 1200-1600 °C and concentrate feeding rate of 1-7 kg/h. This reactor was controlled completely with an automated system with high built-in safety measures. Complete reduction of magnetite concentrate was obtained at an average temperature of 1350 °C and H2/H2O ratio in the offgas of about 3. |
