Hydrogen Reduction of Iron-Bearing Silicates

The kinetics and mechanism of the reduction of olivine by H₂ have been studied at H₂ partial pressures between 0.046 and 0.14 atm and temperatures from 1070 to 1370 K. For Fa₉₃ (Fe_1.86-Mg_0.14SiO₄), the reaction order with respect to H₂ is 0.8 and the activation energy is 205 kJ/mol for conversions up to 40%. For Fa₁₀₀ (Fe₂SiO₄), the reaction order is 0.5 and the activation energy is 260 kJ/mol. The apparent kinetic parameters do not change significantly as conversion increases from about 15 to 60%. Mg²⁺ is less reducible than Fe²⁺, and its presence slows the reaction. The solid products of the reaction are metallic iron and vitreous silica. The products form a nonporous layer around an unreacted core. Permeation of H₂ through this layer is important in determining the rate of reaction.