Two types of coal used in coal-fired power plants were mixed with either Ca-based or Mg-based chemical additives. Raw coal and coal mixed with additives were burnt in a lab-scale drop tube furnace. The impact of the added additives on the transformation of the minerals, as well as on the emission of particulate matter (PM) having an aerodynamic diameter smaller than 2.5μm (PM_<2.5>) was investigated. The generated ash particles were collected using a cyclone combined with a low-pressure impactor. The physical and chemical properties of these ash particles were analyzed. The results indicate that the addition of chemical additives can affect the mineral transformation process, and thus, control the emissions of PM_<2.5> and PM_1 particles during combustion. In particular, the addition of additives has a visible impact on the particle size distribution and chemical composition of the PM, wherein, it improves the degree of coalescence of sub-micron and fine mineral particles, which reduces PM_<2.5> emissions. The effect on the reduction of PM_<2.5> emissions strongly depends on the type of coal being used.