Effect of calcined kaolin on PM0.4 formation from combustion of Zhundong lignite

•During Zhundong lignite combustion, the order of the reactivities for inorganic elements with calcined kaolin is Na > Mg > Fe > Ca.•Chemical adsorption controls the removal of PM0.4 by calcined kaolin.•Addition of calcined kaolin increases the emissions of SO2 and NOx.•Comprehensive consideration of PM, SO2, NOx, and ash fusion temperature is needed to evaluate the performance of additives.•The removal efficiency of PM0.4 is proportional with the temperature between 900 °C and 1300 °C. Kaolin is a widely used additive to alleviate slagging and to control particulate matter (PM) during coal combustion. Calcination is a widely used method of physical modification of kaolin. However, the effect of calcined kaolin on PM during Zhundong lignite combustion is not fully studied. In this research, Zhundong lignite blended with calcined kaolin was combusted in a drop-tube furnace. The performance of calcined kaolin on PM0.4 reduction was analyzed by means of mass-based particle size distribution of PM10, elemental composition of PM0.4, and number-based particle size distribution of PM0.4. Aerosol dynamic modeling was adopted to compare the contribution of chemical adsorption and coagulation to PM0.4 reduction by calcined kaolin. The effect of the addition ratio and the furnace temperature on PM0.4 reduction was systematically investigated. The results showed that the reduction efficiency of PM0.4 by calcined kaolin for Zhundong lignite lacking Si-Al compounds was higher than that for Zhundong lignite rich in Si-Al compounds. Aerosol dynamic modeling indicated that chemical adsorption contributed the most to PM0.4 reduction by calcined kaolin. During Zhundong lignite combustion, the order of the reactivities for the inorganic elements with calcined kaolin was Na > Mg > Fe > Ca. Due to the formation of more reaction sites by calcination, PM0.4 reduction efficiency was proportional to the furnace temperature in range from 900 °C to 1300 °C. By considering the PM0.4 reduction, the increase in SO2 and NOx emissions, and the variation of ash fusion temperatures, the optimized addition ratio of calcined kaolin for Zhundong lignite is approximately 6%.