Emissions of polycyclic aromatic hydrocarbons from fluidized and fixed bed incinerators disposing petrochemical industrial biological sludge

Abstract

This study investigated the emissions of polycyclic aromatic hydrocarbons (PAHs) from two fluidized bed incinerators (FLBI_A and FLBI_B) and one fixed bed incinerator (FIBI) disposing biological sludge generated from the petrochemical industries in Taiwan. The results of 21 individual PAHs (including low (LM-PAHs), middle (MM-PAHs) and high molecular weight PAHs (HM-PAHs)) were reported. The LM-PAHs mainly dominated the total-PAHs in the stack flue gases, whereas the LM- and HM-PAHs dominated the total-PAHs in the bottom fly, fly ash and WSB effluent. Due to high carcinogenic potencies (= total-BaP eq concentrations) in the bottom ash (195 ng g −1) and WSB effluent (20,600 ng L −1) of the FIBI, cautious should be taken in treating them to avoid second contamination. Lower combustion efficiency and elevated fuel/feedstock ( F/ W) ratio for the FIBI led to the highest total emission factor of total-PAHs (38,400 μg kg −1). Lower total-PAH removal efficiencies of wet scrubber (WSB) (0.837–5.89%), cyclone (0.109–0.255%) and electrostatic precipitator (ESP) (0.032%) than those reported elsewhere resulted in high fraction in PAH contributions from the stack flue gases. Lower total-PAH emission factor was found for FLBI_A (2380 μg kg −1 biological sludge) with higher combustion efficiency compared to those for FLBI_B (11,500 μg kg −1) and FIBI (38,400 μg kg −1 biological sludge), implying that combustion efficiency plays a vital role in PAH emissions.