Formation of polychlorinated dibenzo-p-dioxins and dibenzofurans on secondary combustor/boiler ash from a rotary kiln burning hazardous waste

摘要

Ash from the secondary combustor/boiler of a rotary kiln burning hazardous chemical waste was tested in the laboratory for its potential to form polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F). The ash contained only a small quantity of "native" PCDD/F, i.e., formed on the ash in the facility. However, it produced a considerable amount of these compounds when heated in 10% O_2/N_2 under "de novo" conditions, i.e., with residual carbon (present on the ash as result of incomplete combustion) as the only organic material. The ash yielded PCDD/F for up to 90 min; gave PCDD/F yields proportional to the amount of ash used in the reaction bed; and displayed an optimum temperature range for formation (397-548℃) higher than seen for most municipal solid waste (MSW) fly ashes. The role of copper and iron as catalytic material on the ash is discussed.