Isothermal and Non-Isothermal Reduction Behaviors of Iron Ore Compacts in Pure Hydrogen Atmosphere and Kinetic Analysis

Abstract

This study examines the isothermal and non-isothermal reduction behaviors of iron ore compacts in a pure hydrogen atmosphere and compares the results obtained during the reduction process by CO. The different phases accompanying the reduction reactions were identified using X-ray diffraction (XRD) and its morphology was microscopically examined. In isothermal experiments, temperature plays a significant role in the reduction process. At any given temperature, the reduction rate during the initial stages is higher than that during the final stages. The reduction rate in H2 atmosphere was faster than in CO gas. The comparison of activation energy values suggested that reduction with H2 is more efficient than with CO. At the same temperature, the time required to achieve a certain degree of reduction was lower when using H2 gas than CO atmosphere. In non-isothermal tests, the heating rate has a significant effect on the reduction rate and reduction extent. At the same heating rate, the degree of reduction was higher in H2 atmosphere than in CO gas. Based on experimental data, the parameters of reaction kinetics were deduced by application of model-free and model-fitting methods. The reduction in H2 atmosphere was controlled by nucleation model (Avrami-Erofeev model), while the CO reduction reaction was controlled by gas diffusion.

The Influence of Nitrogen on Hydrogen Reduction of Iron Ore Pellets

“…The activation energy calculated by the Arrhenius equation can be used to identify the rate limiting step of the reduction mechanism. [33,37] As the rate limiting step may differ with the reduction degree, activation energy was calculated in the interval R = 0.1-0.5. The calculation was made from 0.1°of reduction to exclude the heating of the sample, which may distort the activation energy estimation.…”

“…This value is in line with previously reported values. [33,34,37] It is important to note that, as there is a mixed control regime, only the apparent activation energies can be calculated from the experimental reduction curves. Therefore, the results should be treated with care.…”

Hierarchical Nature of Hydrogen-Based Direct Reduction of Iron Oxides

“…(f) Hematite sample fully reduced with H 2 up to 10 0 0 °C at a heating rate of 20 °C/min. Iron grows in the form of whiskers (pink arrow) and pores are formed [38] . (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)…”

Non-Isothermal Reduction Kinetics of Iron Ore Fines with Carbon-Bearing Materials

“…The effect of reduction parameters, for example, reduction temperature, retention time, the molar ratio (C/O), iron ore and carbon particle sizes and different additives, on the reduction process were adequately examined by several researchers [16][17][18][19][20][21][22][23]. In general, most of these studies focused on raw materials and the products after the reduction, but only a few works predict the kinetics parameters of iron ore reduced by carbon, which is the significant factor in the reaction mechanism.…”