Interpretation of evaporation behavior of lead from molten copper by the mass-transfer model in fluid flow

Recently, an increasing tendency to eliminate the lead in alloy design has been found because of its harmfulness in health. The lead is required to be removed from copper scrap for recycling. In order to get fundamental knowledge on the use of cheap copper scrap in the manufacturing of lead-free copper alloy, the possibility of removal of lead by gas bubbling from the molten copper alloy has been investigated. The influence of Ar gas flow rate was investigated based on the reaction kinetics and mass transport model. The removal rate of lead was increased with an increase of flow rate of Ar and temperature. The overall removal rate of lead from the molten copper alloy has been calculated from experimental results, and the mass transport of lead in the gas phase (the absolute molar flux of lead) was calculated from the one-dimensional steady state diffusion model. The calculated mass flux of lead in the model is found to be quite similar to the overall removal rate of lead obtained from experimental results. The mass transport of lead vapor in the gas phase seems to be a major part of the rate-controlling steps, under the present experimental condition.