PREDICTIVE MODELING OF HIGH-TEMPERATURE CHEMICAL-SYSTEM VAPORIZATION UNDER ATMOSPHERIC-PRESSURE

An improved numerical technique was evolved in order to stimulate the non-congruent vaporization of complex chemical systems under atmospheric pressure. It concerns a one-dimensional model of a liquid-gas transformation taking into account the connected concepts of interfacial chemical equilibrium and diffusion-regime mass transfer into a boundary layer of concentration. Such a model can be applied to a wide range of physiochemical and geometric configurations of vaporizing systems since the mass transfer coefficient can be estimated. The model has actually been applied to an oxide system at high temperature. It was underlined that the oxygen partial pressure acts strongly on the characteristics of the chemical equilibrium and mass transfer, and consequently on the selectivity of vaporization, in other words the separating power of a chemical species from the bulk. Experiments were also performed according to the physicochemical and geometric characteristics of the model, and their results analyzed and compared with theoretical ones. It was found as a relevant aspect of mass transfer that the oxygen concentration in the carrier gas has a great influence on the vapor boundary layer thickness in relation to the homogeneous nucleation process.