Effective identification of the three particle modes generated during pulverized coal combustion

Based on the mass fraction size distribution of aluminum (Al),an improved method for effectively identifying the modes of particulate matter from pulverized coal combustion is proposed in this study. It is found that the particle size distributions of coal-derived particulate matter actually have three modes, rather than just mere two.The ultrafine mode is mainly generated through the vaporization and condensation processes.The coarse mode is primarily formed by the coalescence of molten minerals, while the newly-found central mode is attributed to the heterogeneous condensation or adsorption of vaporized species on fine residual ash particles.The detailed investigation of the mass fraction size distribution of sulfur(S) further demonstrates the rationality and effectiveness of the mass fraction size distribution of the Al in identifying three particle modes.The results show that not only can the number of particle modes be identified in the mass fraction size distributions of the Al but also can their size boundaries be more accurately defined. This method provides new insights in elucidating particle formation mechanisms and their physico-chemical characteristics.