Abstract
Laboratory scale experiments were conducted to study the emission characteristics and elemental partition of submicron particulate matter (PM) burning Pingdingshan bituminous coal in a drop tube furnace (DTF). Factors influencing the emission characteristics and elemental partition of the submicron PM were investigated, which include the distribution of furnace temperature, coal particle size and oxygen concentration. The fly ash smaller than 10 μm (PM10) in the combustion products was collected by a low pressure impactor (LPI) to obtain size segregated ash samples, and the larger ash particles were collected by a cyclone before the impactor. A similar bimodal distribution of ash particles with a small and a large mode at 0·1 and 4·3 μm respectively, was obtained in all runs. Based on the comparison of concentrations of ash forming elements in the size segregated ash, it was concluded that the ash smaller than 0·4 μm was formed by the nucleation and growth of vaporised ash components. The microstructure of submicron PM was measured by a scanning electron microscopy (SEM). Coal particle size, oxygen concentration, and especially temperature affect submicron PM emission significantly in the combustion. Increasing temperature and oxygen concentration, and decreasing coal particle size leads to more submicron PM formation. With increasing temperature and oxygen concentration, the fractions of Si, Fe, Cu, Zn and Pb in submicron PM increase by 2–3·5 times, the fractions of Mg and Ca show a moderate increase, but Al and Mn appear to be nearly unchanged. It is also found that the coal particle size has little influence on the elemental partition of submicron PM.