Influence of water vapor on continuous cooling crystallization characteristics of coal ash slag

Abstract

The influence of water vapor on crystallization characteristics and kinetics of two synthetic ashes during continuous cooling were investigated by the single hot thermocouple technique (SHTT) and differential scanning calorimetry (DSC) under Ar with 0%, 10%, 20% and 30% H2O. Anorthite (CaAl2Si2O8) and gehlenite (Ca2Al2SiO7) were the major crystalline phases for the slag with 75.44% (YL) and 29.72% (YZ) silicon-aluminum levels, respectively. As the water vapor content increased, the initial crystallization temperature (Ton) and the maximum crystal ratio (Xmax) of the YL slag increased, while it decreased for the YZ slag. The continuous cooling crystallization kinetics was determined based on DSC data. The effect of water vapor proportion on crystallization temperature of the slag showed a similar trend with that on the TCV. As the water vapor proportion increased, the obtained values of crystallization activation energy (Ec) of the YL slag decreased, while it increased for the YZ slag. The influence of water vapor on crystallization kinetics of coal ash slag showed its dependence on nucleation and crystal growth style during continuous cooling. The results well explained the influence of water vapor on crystallization behavior of anorthite and gehlenite crystalline phases as well as its effects on slag viscosity and TCV in our previous studies.