Sorbent capture of nickel, lead, and cadmium in a laboratory swirl flame incinerator,

The in situ capture of toxic metals by sorbents was investigated in a small semi-industrial scale 82 kW research combustor. Metals considered were nickel, lead, and cadmium. These metals were introduced into the system as aqueous nitrate solutions, sprayed down the center of a natural gas flame, supported on a variable swirl burner. Kaolinite, bauxite, and hydrated lime were injected along the centerline in the postflame, near the peak system temperature. Measurements of both the submicron acrosol size distribution and the size segregated particulate composition in the exhaust allowed the effects of sorbent injection to be ascertained, both with and without the presence of chlorine. Lead and cadmium could be almost completely scavenged by kaolinite, which formed melted particles. Bauxite, which did not melt, was exceedingly effective in capturing cadmium. However, chlorine inhibited metal capture in these instances. Hydrated lime also captured cadmium to form a eutectic melt, and this process was slightly enhanced by chlorine. Nickel alone did not significantly vaporize and was not captured by kaolinite. However, in the presence of chlorine, nickel did vaporize and was effectively captured. These results are interpreted and compared to bench scale results in the literature. Two mechanisms, or scenarios, for toxic metal capture are presented.