Effect of Mg-based Additive on the Reduction of PM_<2.5> Emission during Pulverized Coal Combustion

Abstract

This paper aims to evaluate the addition of an Mg-based additive to coal on the emission/reduction of particulate matter (PM) during coal combustion. Four pulverized coals with different mineralogical properties were investigated. Each of them was mixed with Mg-based additive and combusted at 1723K in a lab-scale drop tube furnace (DTF). The results indicate that the Mg-based additive tested here has a pronounced impact on particle size distribution of PM and the morphologies of individual ash particles. For all the coals tested here, addition of the Mg-based additive increased the coarse ash fraction and substantially reduced the amount of ash particles smaller than 2.5μm (PM_<2.5>). This is because the Mg-based additive is able to reduce ash melting point via the formation of low-melting eutectic compounds which promote the coalescence among sub-micron mineral particles. The effect of the Mg-based additive on PM_<2.5> reduction also depends on the properties of the original minerals present in the coal. The comparisons indicate that the model can satisfactorily predict ash formation and properties, taking into account both coalescence of included minerals and fragmentation of excluded minerals.