Experiments on the smelting reduction of oxides of iron, chromium and vanadium and their mixtures with argon/methane‐plasmas

Abstract

The analysis of the smelted alloys and final slags reveals a preferential reduction of iron oxides. This result as well as the influence of an increasing amount of iron oxide in the mixtures on the degree of reduction, is in accordance with thermodynamic calculations. In order to give a detailed description of the kinetics of the smelting reduction, it is necessary to obtain more information on the transport properties of oxide‐ and gas phases as well as the changing partial pressures of the oxygen in melted oxides during the reduction period. Reduction of oxides with a low oxygen partial pressure, for example chromium‐, vanadium‐ and titanium oxides, by use of hydrocarbon gases mainly leads to carbon monoxide as product gas. The high temperatures reached in plasma processes increase this decomposition. Therefore, the hydrogen in the reduction gas can only be the transport medium for the main reducing agent carbon. On the other hand, high reduction temperatures favoured the kinetics of carbonmonoxide formation. Furthermore, higher temperatures lower carburization, which is a great advantage for the production of ferroalloys such as ferrochromium or ferrovanadium. The experiments show that it is possible to take advantage of thermal plasmas for melting and reducing of metal oxides and mixtures respectively, even for the high‐melting chromium oxide. It seems to be possible to melt steels with a high content of alloying elements in a one‐step procedure. For this reason, smelting reduction processes with plasma may be attractive for the production of high‐alloyed steels in small and flexible steel plants.