METAL AEROSOL FORMATION IN A LABORATORY SWIRL FLAME INCINERATOR

Experiments were performed on an 82kW (280,000 Btu/hr) refractory-line d horizontal tunnel combustor to examine the aerosol particle size dis tribution (PSD) produced by simulated nickel, cadmium, and lead wastes injected into an incineration environment. Metal constituents in the form of aqueous solutions of nickel, cadmium, and lead nitrates were i ntroduced as secondary sprays within a swirl stabilized natural gas di ffusion flame. Aerosol size distributions were measured at stack locat ions using a differential mobility particle sizer and a cascade impact or as functions of combustor temperature and waste chlorine content. C admium and lead produced emissions of submicron metal aerosols with ma ss mean diameters of approximately 0.2 mu m. These submicron aerosol P SDs are consistent with a mechanism of metal vaporization followed by nucleation, condensation, and coagulation prior to sampling. Nickel al so formed submicron particles, but the PSD was not generally consisten t with a vaporization mechanism. With chlorine present, the PSDs for a ll three metals were similar in shape, and could be interpreted in lig ht of the effect of chlorine to enhance and prolong the presence of me tals in the vapor phase, and leading to the sampling of a less mature aerosol than that seen under baseline conditions. The effect of chlori ne on nickel partitioning was particularly significant, and is consist ent with vapor pressure predictions.