Peculiarities of Interaction of Electric Arc Furnace Dust with Biochar during Heating in an Inert Atmosphere

Processes occurring during heating of biochar, electric arc furnace (EAF) dust, and their mixtures at different EAF dust/biochar ratios (70/30, 50/50, 30/70) in an inert atmosphere at temperatures up to 1000°C have been studied. According to X-ray diffraction analysis, EAF dust contains phases of Zn0.2Fe0.8Fe2O4 and carbon. Biochar is amorphous carbon with CaCO3. Taking into account the data of thermal analysis of pure components (EAF dust and biochar), including exhaust gas analysis, and elemental and X-ray diffraction analysis data, the processes occurring during reduction of Zn0.2Fe0.8Fe2O4 by biochar carbon are described. It was determined that, during heating of EAF dust/biochar mixtures, in addition to metal reduction reactions (zinc and iron), dehydration and pyrolysis of biochar occur. It has been found that the reduction of Zn2+ from ferrite to Zn0 occurs in the temperature range of 620–720°C, reduction of Fe3+ ions to Fe2+ occurs at 720–850°C, and reduction of Fe2+ to Fe0 occurs at 850–1000°C. According to the value of mass loss, on the thermogravimetry curves in these temperature ranges, taking into account the proposed reduction reactions, the highest yield of reaction products is observed at the ratio of EAF dust/biochar = 70/30.