Emission of Polycyclic Aromatic Hydrocarbons from Co-combustion of Coal and Corncob

The emission of polycyclic aromatic hydrocarbons (PAHs) due to coal co-combustion with corncob (0, 10, 20, and 30%) was studied through a pilot scale drop tube furnace. Total PAHs ( n-ary sumation PAH) emission (gas + particulate) increased linearly from 19.4 mu g/m3 for coal combustion to 31.6, 39.8, and 42.0 mu g/m3 for 10, 20, and 30% corncob blends, respectively. Low-molecular-weight PAHs dominated the gas phase; medium- and high-molecular-weight PAHs in the particle phase. Naphthalene is the most prominent PAH in the gas phase. Emission of benzo[a]pyrene, increased by 45.9% at 10% corncob blend. However, its emission decreased by - 19.1% and - 87.3% for 20 and 30% corncob blends. Toxicity equivalence was also relatively higher for the 10% corncob blend but decreased greatly at 20 and 30% blends. For coal combustion, PAHs are generated due to the pyrolysis process, whereas for coal-corncob co-combustion, pyro-synthesis is the major route of PAH formation, as the PAH content was maximum at the later stage of combustion, i.e., at the bottom zone of the furnace. This study indicated that a minimum of 20% blending of corncob is required to achieve the beneficial effect of coal co-combustion in decreasing the emission of toxic PAHs.