HYDROGEN REDUCTION OF IRON-BEARING SILICATES

The kinetics and mechanism of the reduction of olivine by H-2 have bee n studied at H-2 partial pressures between 0.046 and 0.14 atm and temp eratures from 1070 to 1370 K. For Fa93 (Fe1.86-Mg0.14SiO4), the reacti on order with respect to H-2 is 0.8 and the activation energy is 205 k J/mol for conversions up to 40%. For Fa100 (Fe2SiO4), the reaction ord er is 0.5 and the activation energy is 260 kJ/mol. The apparent kineti c parameters do not change significantly as conversion increases from about 15 to 60%. Mg2+ is less reducible than Fe2+, and its presence sl ows the reaction. The solid products of the reaction are metallic iron and vitreous silica. The products form a nonporous layer around an un reacted core. Permeation of H-2 through this layer is important in det ermining the rate of reaction.