Energy Recovery and Emissions of PBDD/Fs and PBDEs from Co- combustion of Woodchip and Wastewater Sludge in an Industrial Boiler

摘要

The emissions of polybrominated dibenzo-p-dioxins, dibenzofurans (PBDD/Fs), and polybrominated diphenyl ethers (PBDEs) from trial combustion of 10 wt % dried industrial-wastewater-treatment sludge (IWTS) and 90 wt % woodchip in an industrial boiler were investigated and compared to that from woodchip combustion. The PBDD/F toxic equivalent (TEQ) and PBDE emissions increased from 0.121 pg TEQNm~(-3) and 2260 pg Nm~(-3), respectively, of the woodchip combustion to 0.211 pg TEQ Nm~(-3) and 4200 pg Nm~(-3), respectively, of the trial combustion. PBDD/F and PBDE congener profiles of inputs and outputs of the same type of combustion were similar; they also show similarity between woodchip and trial combustions, revealing that the destruction pathway was little affected by the introduction of the IWTS. The fates of PBDD/Fs and PBDEs show that the indigenous pollutants in the feed were effectively depleted (＞93.5%). The dominant releasing route of PBDD/F and PBDE shifted from the stack flue gas of woodchip combustion to the ashes of trial combustion. This study demonstrates that co-combustion not only handles the fast growing sludge stream but also yields a saving of 26.3% in the fuel cost and treatment fees of sludge and ashes.