Effect of Mixed-grinding on Reduction Process of Carbonaceous Material and Iron Oxide Composite.

Mixing state and structure of composite significantly influence reduction kinetics of carbonaceous materials/iron oxides mixture. The present study reports the effect of mixed-grinding of the mixture on the reduction of the composite by indirect heating. Mixtures prepared by different combinations of hematite and graphite reagents, iron ores and metallurgical coke were mixed-ground by two types of ball mills. TG-DTA measurements for the composites were carried out under different heating patterns and total pressures. Reaction temperature remarkably decreases by the mixed-grinding operation in any combinations of materials and total pressures. A catalytic effect of iron produced during reaction is observed when using graphite reagents but seems to be inhibited when using metallurgical coke. A simple kinetic analysis suggests that gasification of carbon is promoted through enhancement of the catalytic effect and/or change of rate limiting step from the gasification of carbon to the direct reactions between iron oxides and carbon.