RESUMEN
One of the industrial wastes, red mud, was assessed as an additive to lime, as a new desulfurization flux for the hot metal in the steelmaking process. Since typical red mud contains some amount of iron oxide, a preliminarily reduced red mud was mainly investigated. Pre-reduction of the red mud and execution of mechanical stirring to the hot metal were effective to enhance desulfurization efficiency (extent and rate of the reaction). However, adding more than 20 pct of red mud in the lime/red mud (pre-reduced) flux did not increase the desulfurization rate. In order to assess the desulfurization efficiency in a more quantitative manner, a "DeS Index" was defined as: [Formula: see text] . This takes into account the extent, rate, and cost of the desulfurization simultaneously. With this index, it was found that the presently developed red mud (pre-reduced)/lime mixtures showed almost similar desulfurization efficiency compared with those of commercially used desulfurization fluxes. It was even better than a typical lime/fluorspar mixed flux, which is now prohibited from being used in many companies due to its environmentally harmful character. It is emphasized that the desulfurization efficiency should be assessed under the mechanical stirring in order to be used in the KR type desulfurization process.
RESUMEN
Evaporation kinetics of tramp elements (M = As and Sn) in liquid iron were investigated by high-temperature gas-liquid reaction experiments and a phenomenological kinetic model. Residual content of As or Sn in the liquid iron ([pct M]) during the evaporation was measured in the temperature range of 1680 °C to 1760 °C. [pct As] and [pct Sn] decreased faster as the reaction temperature and [pct C]0 increased. Assuming first-order reaction kinetics, the apparent rate constants (kM) were obtained at each reaction temperature and [pct C]0. [pct M] in a liquid iron during the top-blown oxygen steelmaking process was simulated, with an emphasis on enlarging the reaction surface area by forming a large number of liquid iron droplets. The surface area and the droplet generation rate were obtained based on the oxygen-blowing condition. The whole surface area increased up to â¼163 times the initial liquid iron (bath) surface area, due to the generation of the droplets. Using the kM obtained in the present study, the evaporation of M during the top-blown oxygen steelmaking process for 200 tonnes of liquid iron was simulated. For a condition of [pct M]0 = 0.005 (M = As and Sn), As and Sn could be removed from the liquid iron, which was seen to be much improved by the consideration of the droplet generation. However, additional actions are required to improve the evaporation rate, as the evaporation rate in the BOF process was not fast enough to be practically considered.