On Expediency of the Preliminary Heat Treatment for Liquid-Phase Reduction of Waste Steelmaking Slag

The problem of using waste steelmaking slags as a technogenic source of metallurgical raw materials still has no sustainable solution and requires innovative ideas and approaches. The purpose of this paper is a theoretical and experimental study of the possibility and expediency of the preliminary heat treatment of steelmaking slags in a reducing medium for greater metal recovery. The subject of research is a slag sample taken from the slag heaps at Zlatoust Metallurgic Plant (the Russian Federation). To perform thermodynamic simulation of the processes running during heat treatment of a slag substance, the FactSage software package (version 6.4) was applied. For the ease of analysis the key calculation results are presented as a logarithmic dependence of component weights and composition of the considered phases on temperature. The experimental studies include heat treatment tests on slag samples at temperatures of 1100 and 1200°C in air and in the carbon monoxide medium with further separation of the derived product. The composition of test samples is determined by electron microprobe analysis and X-ray diffraction analysis. It has been reported that heat treatment in carbon monoxide medium makes possible to significantly increase the iron content in the derived magnetic fraction. The results of thermodynamic simulation, composition analysis of samples and weight data for the obtained magnetic fractions (resistant or non-resistant to the magnetic field) suggest that the preliminary heat treatment of slag in carbon monoxide medium is expedient.