Effect of magnesium additives on PM2.5 reduction during pulverized coal combustion

The effect of three types of Mg-based additives on reducing the emissions of particulate matter with an aerodynamic diameter smaller than 2.5 μm (PM2.5) during pulverized coal combustion has been investigated. Combustion test was carried out in a lab-scale drop tube furnace (DTF) at 1723 K in air. The physical and chemical properties of PM were quantitatively analyzed by XRF and CCSEM. Experimental results indicate that three different Mg-based additives significantly increase the coalescence probability between sub-micron mineral particles hence reduce the PM2.5 emission during combustion accordingly. In a case of the superfine dispersed Mg-based additive, ca. 60% PM1 and PM2.5 reduction were achieved comparing with raw coal combustion, respectively. However, it is confirmed that the reduction efficiency on PM emissions also related to the physical properties of the additives used in this study. The transformation pathways, which different Mg-based additives undergoing during ash formation process, result in the variation in element distribution and morphology of resultant ash particles.

Research highlights
► Both of the sorts and the particle size of Mg-based additives influences their efficiency on PM2.5 reduction.
► The super dispersed M201 shows significant effect.
► With its addition, the PM1 and PM2.5 were reduced to 40% comparing with raw coal combustion, respectively.
► Under the contribution of added Mg, refractory elements of Al, Si, and Fe are transferred into coarse particles, and the emission of PM are reduced accordingly.