On the correlation of CO and PAH emissions from the combustion of pulverized coal and waste tires

Results are presented on the correlation of the emissions of carbon monoxide (CO) and polynuclear aromatic hydrocarbons (PAH) from the combustion of pulverized bituminous coal and tire-derived fuel, The particle size cuts of coal and tire crumb were 63-75 and 180-212 mu m, respectively. Combustion experiments were conducted in laboratory-scale facilities under controlled conditions. The relation between CO and PAH species in the combustion effluent was investigated at drop-tube furnace gas temperatures, in the range of 1000-1300 degrees C, and several fuel mass loadings in the furnace, expressed in terms of bulk equivalence ratios in the range of 0.7-2.4. Up to 60 two-seven ring PAH compounds were detected by capillary gas chromatography-mass spectrometry (GC-MS) techniques. Results showed that both CO and PAH emission yields increased with increasing bulk equivalence ratio (in the aforementioned range) at a fixed gas temperature. The CO and especially the PAH yields from tire-derived fuel were much higher than those from coal, but the relative amounts of individual PAH components were remarkably similar in the combustion effluent of the two fuels. At fixed bulk equivalence ratios, however, as the furnace gas temperature increased the PAH yields from both fuels decreased drastically, while the CO yields increased. At the highest temperature tested herein (1300 degrees C), the effluent of the combustion of both fuels was practically devoid of PAHs [at a detection limit of 0.7 mu g of a PAH component/g of fuel burnt]. Reasons for the observed increase in CO with temperature are discussed. CO2 and NO(x )emission yields were also monitored, and the results are reported herein.