Evolution of metal contaminants from incinerated solids

The vaporization behavior of metal contaminants was studied in both a bench-scale and a pilot-scale reactor. The results of bench-scale experiments indicated that the behavior of metal contaminants at low concentrations on solid substrates can be very different from the pure component behavior of the metal contaminant. Pilot-scale studies focused on characterizing the behavior of metal contaminants at low concentrations in a batch rotary kiln environment. Solid samples of the contaminated clay bed material were removed from the kiln at various intervals providing data for the concentration of chromium, cadmium, copper, barium, lead, zinc, and strontium in the clay material over time. The resulting evolution plots indicated that after an initial drop in concentration, a temperature dependent, pseudo-equilibrium concentration was maintained in the batch rotary kiln simulator. Further processing for times up to 2 hours did not result in additional vaporization. In addition, different initial metal contamination solutions were used in the pilot-scale experiments including nitrate, chloride, and sulfate solutions of the contaminant metals and the results indicated essentially the same vaporization behavior for most all of the metals regardless of the initial spiking solution.