QUASI-STATIONARY ANALYSIS ON THE CHLORINATION AND VAPORIZATION REACTION OF PB-OXYCHLORIDE IN ASH AND DUST RECYCLING

摘要

A quasi-stationary analysis on chlorination-vaporization reaction of Pb-oxychloride in pyrometallurgical processing of ash and dust has been made, with the goals of clarification of reaction mechanism, estimation of rate-limiting step and establishment of rate-controlling equation. A molten salt layer composed of PbO-PbCl2 was considered to be formed dependent on the relative magnitude of evaporation rate of PbCl2 to its formation one, and the corresponding bulk diffusion of components throughout the formed molten salt layer was estimated to be the rate-limiting step for the overall reactions. Based upon the theoretical treatment of phenomenological mass transport equations, simulation calculation for the relative chemical potential, molar fraction and mass flux of the related components throughout molten salt layer have been performed under quasi-steady state, which can be used to evaluate the effects of treatment temperature and Cl-potential in atmosphere on the chlorination-vaporization reaction. Furthermore, the possibility of the corresponding diffusion of combined oxygen-ion as rate-limiting step was also proposed.