Wall losses of volatile metal oxides during spray pyrolysis

Abstract

The role of product evaporation during lead monoxide (PbO) powder generation by aerosol decomposition (spray pyrolysis) was studied as a function of temperature in a flow reactor. The dominant phase of the particles formed changed from litharge to massicot with increasing temperature. Scanning Electron Microscopy analysis of the powders showed particles produced at lower temperatures had a lumpy surface morphology and at higher temperatures appeared to be solid, indicated by the faceted surfaces and a platelike morphology. There were significant evaporative losses of PbO X to the reactor walls due to the substantial vapor pressure of PbO X. A simple model was developed that takes into account particle evaporation and mass transfer of lead oxide vapor to the reactor walls. Model simulations suggested that the loss of lead oxide to the reactor walls was limited by diffusional transport of lead oxide vapor to the reactor walls.