Trace metal fate in a rotary kiln incinerator with an ionizing wet scrubber

A series of pilot-scale incineration tests was performed at the Environmental Protection Agency's (EPA's) Incineration Research Facility to evaluate the fate of trace metals fed to a rotary kiln incinerator equipped with an ionizing wet scrubber for particulate and acid gas control. Test variables were kiln temperature, ranging from 816–927 °C; afterburner temperature, ranging from 982–1204°C; and feed chlorine content, ranging from 0–8%. The test program evaluated the fate of arsenic, barium, bismuth, cadmium, chromium, copper, and lead. The test results indicate that cadmium and bismuth were relatively volatile, with an average of less than 40% discharged with the kiln ash. The other seven metals were relatively nonvolatile, with an average of greater than 80% discharged with the kiln ash. Observed relative metal volatilities generally agreed with predictions based on vapor pressure/temperature relationships, with the exception of arsenic which was much less volatile than predicted. The volatility of cadmium, bismuth, and lead increased as kiln temperature was increased; the discharge distributions of the remaining metals were not significantly affected by changes in kiln temperature. Apparent scrubber collection efficiencies for the metals averaged 22–71%, and were generally higher for the less volatile metals. The overall average metal collection efficiency was 43%.