Abstract
Understanding the reaction kinetics of iron oxide reduction by carbon is a key task of the theory of metallurgical processes. One of the understudied features of the reaction kinetics of iron oxide solid-phase reduction by carbon is the discrepancy between the reacting substances’ small contact area and the process’s high rate. A convincing theoretical and experimental explanation of this effect has not yet been obtained. The data obtained earlier show that an increase in the scale of the briquetting pressure from 0 to 300 MPa increases the degree of its metallization during heating two-fold, and the metallization temperature decreases by more than 40 °C. Therefore, it was assumed that these effects during heating are a consequence of the mechanochemical activation (MCA) of iron oxides in the scale during its pressing. This paper presents the results of experimental studies on the influence of two types of scale MCA (grinding and pressing) on iron oxide reduction. The study of the MCA effect on the reaction kinetics of scale iron oxide reduction by carbon is a promising way to assess the criteria for scale phase composition changes under external factors. The presented results indicate a decrease in the amount of trivalent iron oxide (Fe2O3) after the MCA and an increase in the amount of one-and-a-half oxide (Fe3O4) and bivalent iron oxide (FeO). The obtained experimental data show that the initial stage of iron oxide reduction, consisting in the transition from higher iron oxides to lower ones, is possible at room temperature without carbon presence.
Highlights
Throughout the centuries-old practice of iron ore reduction, solid carbon in the form of wood, coal and coke has become the most widespread reductant
This paper presents the results of experimental studies on the influence of two types of scale mechanochemical activation (MCA) on iron oxide reduction
The study of the MCA effect on the reaction kinetics of scale iron oxide reduction by carbon is a promising way to assess the criteria for scale phase composition changes under external factors
Summary
Throughout the centuries-old practice of iron ore reduction, solid carbon in the form of wood, coal and coke has become the most widespread reductant. Most researchers into the solid-phase model of iron oxide and carbon interaction explain the reduction’s high rate by the presence of defects in the iron oxides’ crystal lattices, through which the ions of reacting substances are diffused. In the literature there is a significant amount of work on another MCA method (grinding to high specific surfaces of the oxide material) It was shown in [6] that mechanical treatment of Fe and α-Fe2O3 mixture in a planetary centrifugal mill leads to the formation of a nanocrystalline wustite (FeO) of nonequilibrium composition. The interaction of oxygen wustite with solid carbon will lead to the formation of metallic iron and CO according to Equation (5): FeO + C = Fe + CO↑ This reaction is thermodynamically possible from 800 ◦C. Changing the classical metallurgical scheme for preparing the raw mixture for firing by pelleting and for agglomeration for cold briquetting would significantly reduce the consumption of coke
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