Kinetics of Gaseous Reduction of Iron Ore Fines

Abstract

Unsintered beds of blue dust of varying thicknesses were subjected to reduction in flowing reducing gases. The temperature range was 898 to 1123 K for hydrogen reduction and 1073 to 1373 K for reduction by carbon monoxide. Reduction by CO was carried out in two-stages, and only the data of second stage (wustite→iron) were analysed further. Several approaches to data analysis were attempted. The most satisfactory one was to take the slope of the initial linear region of fractional reduction vs. time curve as a measure of rate constant (k). Extrapolation of k vs. bed depth data to hypothetical zero bed depth for H₂-reduction and to 0.4 mm depth for CO-reduction allowed determination of chemical rate constants (k_c). In k_c vs. 1/T plots were not straight lines. This and other anomalous behaviours were attributed to structural changes in the bed during reduction.