Hydrogen Reduction Kinetics of Hematite Concentrate Particles Relevant to a Novel Flash Ironmaking Process

As an integral part of developing a novel ironmaking process, the hydrogen reduction kinetics of hematite concentrate particles (average particle size 21 µm) were measured in the temperature range from 1423 K to 1623 K (1150 °C to 1350 °C). The novel ironmaking process aims at producing iron from iron oxide concentrates in a flash reactor using gaseous fuels and reductants, which will help reduce energy consumption and minimize greenhouse gas emissions. More than 90 pct reduction of hematite concentrate particles could be obtained by hydrogen at a temperature of 1573 K (1300 °C) and 3 seconds of residence time, indicating that hematite concentrate is suitable for the flash reduction process under development largely aimed at the use of magnetite concentrates. The nucleation and growth rate equation with the Avrami parameter, n, of 1.0 well described the kinetics of hematite reduction. The reduction rate has a 1st-order dependence on the partial pressure of hydrogen. The activation energy of the reaction was 214 kJ/mol, indicating strong temperature dependence. The following complete rate equation was developed that can satisfactorily predict the kinetics of hematite concentrate particles and is suitable for the design of a flash reactor: \( \frac{{{\text{d}}X}}{{{\text{d}}t}} = 4.41 \times 10^{7} \times {\text{e}}^{{\frac{ - 214{,}000}{RT}}} \times \left( {p{\text{H}}_{2} - \frac{{p{\text{H}}_{2} {\text{O}}}}{K}} \right) \times (1 - X), \) where X is fractional reduction degree, R is 8.314 J/mol K, T is in K, p is in atm, and t is in seconds.