Influence of ash on particle size distribution evolution during coal combustion

Abstract

In this work we describe a numerical model of the evolution of the particle size distribution (PSD) during coal combustion. The model includes burning and fragmentation. The model examines the sensitivity of PSD evolution to different modes of fragmentation by allowing the input of alternative fragmentation scenarios. A highlight of the model formulation is the incorporation of mineral matter as a distinct constituent of the coal. Evolution of the size distribution of mineral matter is modeled explicitly. We apply the model to two different initial size distributions, a monodispersion and a power-law distribution similar to that of pulverized coal, each with three alternative modes of fragmentation: no fragmentation, fragmentation into a few relatively large fragments, and fragmentation into a family of fragments covering a wide size range. The simulations suggest that the size distribution of ash particles obtained from an initially monodisperse feedstock is sensitive to the fragmentation scenario; in contrast the ash size distribution is not sensitive to the mode of fragmentation if the initial feedstock is power-law distributed.