A Mechanism Study on the Decomposition of Sulfate in Zhundong Coal with High Sulfur Content in Coal Ash

Sulfate in Zhundong (ZD) coal combustion plays a significant role in fouling, slagging, and particle emissions. This study aimed to investigate the effect of SiO2 and kaolin addition on sulfate transformation in ZD coal ash by using thermogravimetric analysis (TGA) and other characterizing methods for ash with SiO2 and kaolin addition under different temperatures. Results showed that SiO2 and kaolin both enhanced the decomposition of sulfates in ZD coal ash under higher temperatures. The decomposition of sulfates in pure ZD coal ash started above 1050 °C, while the starting temperature was ahead by 50 and 100 °C, when SiO2 and kaolin were added, respectively. Kaolin addition was more efficient to improve the thermal decomposition of sulfates than SiO2 addition. However, the enhanced effect of SiO2 and kaolin was very weak below 815 °C. The thermal calculation results also gave the similar result on the enhancement effect on sulfate decomposition of SiO2 and kaolin addition.