Evaluation of a Mg-Based Additive for Particulate Matter (PM)_(2.5) Reduction during Pulverized Coal Combustion

摘要

This paper aims to evaluate the addition of a 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 1723 K 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 of the coals tested here, the addition of the Mg-based additive increased the coarse ash fraction and substantially reduced the amount of ash particles smaller than 2.5 μm (PM_(2.5)). This is because the Mg-based additive is able to reduce the ash melting point via the formation of iow-melting eutectic compounds, which promote the coalescence among sub-micrometer mineral particles. The effect of the Mg-based additive on PM_(2.5) reduction also depends upon the properties of the original minerals present in the coal. The particle size distributions and concentrations of PM_(10) were also compared to that predicted by an advanced coalescence and fragmentation model developed here. 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 at high temperature.