Mechanism Study on the Effect of Magnesium-based Flux on the Fusibility of Coal Ash with High Fusion Point

The effect of magnesium-based flux on the fusibility behavior of Huainan coal ash with high fusion point was studied by adding different amount of magnesium-based flux to the coal ash. Results show that for Huainan coal ash, the ideal addition is 5%, in which case the coal ash fusion point may be reduced to 1 350 ℃; the high fusion point of Huainan coal ash is found to be caused by the refractory mineral mullite by XRD and SEM analysis, which may be reduced by Mg²⁺ reacting with mullite to form eutectic minerals, such as cordierite and Ringwoodite, etc. Through quantum chemical calculation, the mullite system is proved to be completely stable, and the Mg²⁺ could easily enter into mullite crystals from the unsaturated O(7) and O(13), which results in both the rupture of the covalent bond between Al(1)-O(13) and Al(8)-O(13), and the distance enlargement between two Si atoms in silicate, and finally leads to the lattice recombination of mullite.