An overview of inorganic particulate matter emission from coal/biomass/MSW combustion: Sampling and measurement, formation, distribution, inorganic composition and influencing factors

This paper systematically reviews the PM sampling and measurement methods, formation mechanisms, distribution, inorganic composition and the factors influencing PM emission during combustion of coal/biomass/MSW. Particle sampling and measurement methods are developing rapidly utilizing various techniques, however, the direct sampling techniques for particle in the high temperature flue gas is still lacking. Particle is generated by a series of physical processes (evaporation, condensation, fragmentation etc.) and chemical reaction processes of inorganic mineral components and organically bound metal compounds in the solid fuels. The available literature data shows that the emission of coarse particles from coal combustion is generally higher than that from biomass, while the emission of ultrafine and fine particle from biomass combustion is higher than that of coal. Particle emission is related to a variety of influencing factors such as solid fuels particle size, inherent ash content, mineral properties, binding form of inorganic elements, combustion parameters (temperature, pressure, residence time, oxygen concentration etc.) and ash chemical composition. The content of Na, K, S, Cl, Si and Al plays a decisive role in PM10 emissions, the (Na2O + K2O)/(SiO2 + Al2O3) ratio of ash can be used as an index to predict the yield of PM0.3 in coal and biomass combustion.