The progressive formation of submicron particulate matter in a quasi one-dimensional pulverized coal combustor

In this work, we aim to investigate the formation mechanisms of submicron particulate matter (PM1) by observing progressive changes of collected samples at different combustion stages. A 25 kW quasi one-dimensional down-fired pulverized coal combustor was used, where PM1 was collected from the furnace centerline through the desired sampling ports by using a nitrogen-aspirated, water-cooling isokinetic sampling probe followed a 13-stage electric low pressure impactor. First, the mass concentration particle-size-distributions (PSD) of PM1 sampled at coal flame zone clearly exhibit two distinct modes separated by a fraction of 0.173–0.267 μm, ultrafine mode and intermediate mode. However, the ultrafine peak around 63 nm greatly decreases and becomes flat as coal combustion further progresses along axial length. Then, the contributions of either organically bounded minerals or inherent minerals to these two modes at different stages are analyzed. Finally, the evolution of sulfur-concentration PSD reveals the effects of pyrite decomposition and the sulfation reaction on PM1 formation in the combustion system.