Kinetics of the Reduction of Hematite Concentrate Cross Mark Particles by Carbon Monoxide Relevant to a Novel Flash Ironmaking Process

A novel ironmaking process is under development at the University of Utah to produce iron directly from iron oxides concentrates by the gas solid flash reaction using gaseous fuels and reductants. This process will reduce energy consumption and minimize carbon dioxide emissions. Having investigated the hydrogen reduction kinetics of magnetite and hematite concentrate particles relevant to the novel flash ironmaking process, the carbon monoxide reduction kinetics of hematite concentrate particles (average particle size 21 pm) was determined in the temperature range 1473 K to 1623 K (1200 degrees C to 1350 degrees C) under various carbon monoxide partial pressures. At 1623 K (1350 C) and residence time 5 seconds, the reduction degree of hematite concentrate particles was more than 90 pct under a pure carbon monoxide. This is slower than reduction by hydrogen but still significant, indicating that CO will contribute to the reduction of hematite concentrate in the flash process. The kinetics of CO reduction separately from hydrogen is important for understanding and analyzing the complex kinetics of hematite reduction by the H-2 + CO mixtures. The nucleation and growth rate equation with the Avrami parameter n = 1.0 adequately described the carbon monoxide reduction kinetics of hematite concentrate particles. The reduction rate is of 1st order with respect to the partial pressure of carbon monoxide and the activation energy of the reaction was 231 kJ/mol, indicating strong temperature dependence. The following complete rate equation was developed that can satisfactorily predict the carbon monoxide reduction kinetics of hematite concentrate particles and is suitable for the design of a flash reactor di{= 1.91 x 10(7) x e-23100D/RT (pCO - pCKO(2/)K) x (1- X), where Xis the fraction of oxygen removed from iron oxide, R is 8.314 J/mol K, T is in K, p is in atm, and t is in seconds. (C) The Minerals, Metals & Materials Society and ASM International 2015