Effect of kaolinite additive on water-soluble sodium release and particle matter formation during Zhundong coal combustion

Abstract

Zhundong coal causes serious slagging problems and particle matter (PM) pollution due to its high sodium content. In this paper, sodium release and PM formation experiments were carried out in tube and laboratory dropper furnaces using three types of coal in Zhundong. The effects of kaolinite additives on sodium release and PM formation, as well as the mechanism of different types of sodium release and PM formation, were investigated. The results showed that compared with water-soluble sodium, most organic sodium was released after a series of complex complexation reactions, such that kaolinite exhibited a better adsorption effect on water-soluble sodium. Furthermore, the concentration of different types of Na in PM emitted differed as a result of different coals, which would lead to different collision frequencies between particles and kaolinite. The PM2.5 stemmed from the homogeneous condensation of volatile elements and the fragmentation of minerals in the combustion, while the PM10 originated from the coalescence of the fine fragments of fly ash. Moreover, the kaolinite additive intensified the heterogeneous condensation reaction with gaseous sodium to form larger particles, due to the reaction effect of kaolinite for water-soluble sodium of PM2.5 being stronger than organic sodium and the organic sodium of PM10 being stronger than water-soluble sodium.