Kinetics and mechanism of llmenite reduction with graphite

The reduction of synthetic ilmenite with graphite in the solid state has been studied by ther-mogravimetric analysis. The reaction has been observed to initiate near 860°C at the contact points between the reactants. Up to 1020°C solid state reduction appears to be the main reaction mechanism, while above this temperature a rate increase has been observed and has been attributed to a change of mechanism to gaseous reduction of ilmenite by regenerated CO. Microscopic examination and electron probe analysis of the reduced particles have indicated a tendency toward segregation of the products iron and TiO2. Iron particles as large as 80 μ can be obtained by keeping the reduced sample at 1025° to 1075°C for several hours. Reduction rate data under isothermal conditions were fitted to different rate equations and have been found to be well represented by the equation. 1 − 2x/3 − (1 −x)2/3 =K’ This equation is based upon diffusion of reactants through a product layer. CO is suggested as the diffusing species. The activation energy for the reaction in the temperature range 1075° to 1140°C has been calculated to be 64 ± 6 kcal per mole.