Observations of FeO Reduction in Electric Arc Furnace Slag by Aluminum Black Dross: Effect of CaO Fluxing on Slag Morphology

The effect of CaO fluxing on slag morphology was investigated during the reduction of FeO in electric arc furnace slag by aluminum black dross (ABD). Macro- and microscopic observations, by evaluating entrapped gas bubbles and reduced iron droplets related to gas evolution, apparent slag morphologies, and vertical section of slag at different initial CaO contents and reaction times, confirmed that both aluminothermic (dominant reaction) and carbothermic (minor) reduction occurred. Thus, the production of CO(+CO 2 ) gas caused swelling-shrinking phenomena with repeated expansion and collapse of the slag pellet. In addition, macroscopic observation of slag morphologies as a function of the initial CaO content is well associated with quantitative consideration of the apparent viscosity as well as spinel ([Mg,Fe]Al 2 O 4 ) activity. Consequently, appropriate CaO fluxing is necessary to control the composition of highly fluid slag by changing the slag from a high-alumina system to calcium–aluminosilicate melts when utilizing ABD as a reducing agent.