Thermal treatment of polychlorinated dibenzo- p-dioxins and dibenzofurans from contaminated soils

Abstract

Thermal treatment technology was used to remove polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) from heavily contaminated soil. For a soil with an original PCDD/F content of 35,970 ng International Toxic Equivalents (I-TEQ)/kg, >99.99% PCDD/F removal efficiency was obtained with a primary furnace at two different treatment temperatures (750 °C and 850 °C), while a secondary furnace at 1200 °C gave >98% decomposition efficiency. The total PCDD/F I-TEQ contents in treated soils at 750 °C and 850 °C were 1.56 ng I-TEQ/kg and 2.15 ng I-TEQ/kg, respectively, which were far below the soil pollution standard of Taiwan (1000 ng I-TEQ/kg soil). Although air pollution control devices had significant effects on the removal of PCDD/Fs, the total I-TEQ concentrations in the upstream flue gas of PUF cartridge at 750 °C and 850 °C (2.61 ng I-TEQ/Nm 3 and 2.38 ng I-TEQ/Nm 3, respectively) were still higher than the stationary emission limit of the Taiwan EPA (0.5 ng I-TEQ/Nm 3). The above results also suggested that additional APCDs, such as activated carbon injection in front of the filter are needed to enhance PCDD/F removal efficiency.