Superfund Research Program
Activation, Sensing, and Prevention of Formation EPFRs in Thermal Treatment of Superfund Wastes
Final Progress Reports
Environmentally persistent free radicals (EPFRs) are recently realized pollutants associated with particles emitted from thermal and combustion sources. Slawo Lomnicki, Ph.D., and his research team have discovered that EPFRs formation (and thus their emission) during the thermal treatment of Superfund materials can be suppressed by management of SO2 pollution control – shifting the SO2 scrubbing process to the lower temperature region of installations (below EPFRs formation window) will block the active sites on which EPFRs are formed. The team has also increased the understanding of the underlying mechanism of dioxins formation and emission from thermal treatment of Superfund materials. The dioxins are very sensitive to the catalytic metal speciation in the fly ashes. In particular, the presence of iron oxide above four percent by mass will increase the furans fraction to be formed. At smaller concentrations, iron oxide catalyzes oxidation of the dioxins precursors. When present in conjunction with copper, the dioxins emission is dependent on the process conditions. In oxygen-rich conditions (which equal to efficient mixing of gasses in the exhaust), synergy between iron and copper results in destruction of precursors and no dioxins formation. Process upsets, insufficient mixing, and formation of pyrolytic pockets in the flue gas stream will instantly result in the large yields of dioxins (much higher than compared to single metal oxide systems).