Abstract
The kinetics of Zn fuming from a fayalite-based slag through stirring with air-CH4 gas mixtures have been studied by laboratory-scale experiments. The influence of process parameters including carbon addition, gas flowrate, slag composition and temperature on the Zn fuming rate is identified. A kinetic model of Zn fuming in a bubble-stirred bath is developed according to the understanding of the rate-controlling step of the fuming process, and the volumetric mass transfer coefficient k(l)a is obtained by fitting with experimental data. The theoretical k(l)a is further calculated to deepen the understanding of the gas flow rate effect on the fuming kinetics. The results indicate that the fuming process consists of an unsteady fuming stage and a main fuming stage, and k(l)a in the latter agrees well with the Zn fuming kinetic model. The mass transfer of ZnO in the liquid phase, which is closely related to the gas flow rate, is likely to be the rate-controlling step. The model can be extended to simulate bubble-stirred fuming systems and to optimize the process parameters of laboratory-scale and industrial set-ups.