Emission characteristics of PCDD/Fs, PAHs and PCBs during the combustion of sludge-coal water slurry

Abstract

This study focused on the combustive feasibility of Sludge-coal water slurry (SCWS) in a commercial circulating fluidized bed incinerator, and on the emission characteristics of the inorganic and organic contaminants in the flue gas during the combustion of SCWS. The results showed the flue gases emitted contained nitrogen oxides (NOx), sulfur oxides (SOx), PAHs, PCBs and PCDD/Fs during the combustion of SCWS in different mixture ratio (0%, 10%, 20%, 30%, 40%). When the ratio of sludge increased, the concentration of NOx increased and the concentration of SOx decreased, while no significant changes were found for the other inorganic gases. The ∑PAHs concentration range was from 2.0015 μg/m3 (0%) to 9.7064 μg/m3 (30%), Low molecular weight PAHs (two or three rings) were the main component in flue gases in all proportions. The maximal value of the PCB concentration was 1.7852 μg/m3 (20%), while the minimal value was 0.6191 μg/m3 (0%), all PCBs are mainly low rings. The I-TEQ content of PCDD/Fs increased slightly with increasing of the ratio, but it was still less than that (0.12382 ng/m3) of CSW burning alone. In general, the total PCDD/Fs of 10%–30% ratio does not exceed 0.1 ng/m3 of EU standards. Therefore, the combustion of sludge coal water slurry is feasible, comparing emission of PAHs, PCBs and PCDD/Fs with flue gas emission standards, the best ratio of SCWS is 20%–30%.