Effects of carbide slag blending combustion on particulate matter formation characteristics of high-alkali coal

The effects of industrial carbide slag (CS), a Ca-based sorbent, on particulate matter formation were investigated in a drop-tube furnace using two high-alkali coals: high-Ca Zhundong (ZD) and high-Fe Hongshaquan (HSQ). Increasing the CS blending ratio from 3% to 9% shifted the particle mass distribution towards the coarse mode. At 6% and 9% CS, the combined mass proportion of ultrafine and fine particles was lower than that from raw coal combustion for both coals, with a greater decrease for ZD coal. The overall Ca mass fraction increased with CS addition, whereas the overall Na mass fraction peaked at 3% CS and then decreased. For ZD coal, 9% CS increased the ultrafine-mode Na and transitional-mode Ca mass fractions by 12.4 and 12.6 percentage points, respectively, relative to raw coal. Fe and Si enrichment in HSQ fine particles suggested the possible presence of Fe-containing silicates. Morphological and elemental analyses suggested that Na-containing surface deposits may promote the agglomeration of Ca-silicate and Fe-containing silicate particles in the coarse mode.