The emissions of PAHs and heavy metals from co-combustion of petrochemical sludge with coal in CFB incinerator

Abstract

The polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Hg, Pb, Ni, Cr, Cu, Zn) emission characteristics in flue gas from co-combustion of petrochemical sludge and coal were investigated in a pilot-scale circulating fluidized bed (CFB) incinerator with a thermal input of 0.2 MW. Experimental results show that when mass ratio of petrochemical sludge/coal increases from 10% to 40%, PAHs, Hg and Zn emissions increase, while Pb and Ni emissions decrease. Mass mixing ratio has no obvious effect on the emissions of Cr and Cu. As combustion temperature increases, PAHs emission decreases at first and then increases, there is an optimum combustion temperature inhibiting PAHs formation, while emissions of Hg, Pb, Cu, Zn increase relatively rapidly. With Ca/S molar ratio increasing, PAHs, Hg, Pb, Ni, and Cu emissions decrease due to adsorption by calcium sorbents. Limestone is effective in adsorbing Pb and Ni, while lime is suitable to adsorb Hg and Cu. However, Ca/S molar ratio doesn't have much influence on the emissions of Cr and Zn. Some combustion parameters are recommended based on stable combustion and low pollutant emission.