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 considere d were nickel, lead, and cadmium. These metals were introduced into th e system as aqueous nitrate solutions, sprayed down the center of a na tural gas flame, supported on a variable swirl burner. Kaolinite, baux ite, and hydrated lime were injected along the centerline in the postf lame, near the peak system temperature. Measurements of both the submi cron aerosol size distribution and the size segregated particulate com position 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 form ed melted particles. Bauxite, which did not melt, was exceedingly effe ctive in capturing cadmium. However, chlorine inhibited metal capture in these instances. Hydrated lime also captured cadmium to form a eute ctic 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 ef fectively captured. These results are interpreted and compared to benc h scale results in the literature. Two mechanisms, or scenarios, for t oxic metal capture are presented.