Study on the mineral transformation and heavy metal distribution during high-silicon coal combustion

The high-silicon coal in Xuanwei area of Yunnan is selected to study the transformation behavior of minerals and the distribution and enrichment of heavy metals during the combustion process. The minerals in high-silicon coal are mainly composed of quartz, kaolinite, pyrite and anatase. The mullite in fly ash may come from the transformation of quartz and kaolinite in coal; the quartz in fly ash mainly comes from the original quartz component in coal or is formed by the conversion of SiO₂-Al₂O₃ system. Analyzing the enrichment characteristics of several heavy metals in high-silicon coal and its fly ash, it can be found that Cr, Cu, and As are enriched in the high-silicon coal, and Mo is the heavy metal enriched in the electric fields of the ESP, while Se contents in high-silicon coal and fly ash in China are both lower than the world average level. The contents of radioactive elements of Th and U in the fine-particle high-silicon fly ash are higher than the average of world coal ash, and the enrichment factors in the fly ash in the four electric fields of the ESP are 1.51 and 1.59, respectively.