The uneven distribution characteristics of minerals in Zhundong high iron coal and its influence on the slagging process

Due to the influence of the special coal formation environment, the distribution of minerals in coal was not uniform, especially for the Zhundong high iron coal. The impact of this uneven distribution on slagging formation during coal combustion process was still unclear. In this study, three types of Zhundong coal with varying iron contents were selected, the coal and ash characteristics of different density fractions were analyzed after density fractionation. The minerals transformation characteristics of coal ash were also calculated by Factsage. The results showed that the density distributions of the three coal samples differ significantly. HSQ and JJM was primarily concentrated in below 1.4 g/cm3 and 1.4–1.5 g/cm3 two density fractions, but the proportion of >1.6 g/cm3 fraction of JJM was higher than that of HSQ. While the mass distribution of WCW across density ranges showed minor differences. The ash characteristics also exhibited significant differences across the density fractions. As coal density increases, the Na and Ca contents decreased, whereas the Si and Al contents gradually increased, and the Fe content increased substantially. This was particularly evident in JJM coal, where the iron content in the JJM4 ash exceeded 55 %. In the ash of low-density fractions, Na and Ca mainly existed in the form of Na2SO4 and CaSO4, while they mainly existed in the form of combined with Si and Al in the ash of high-density fractions. Besides, Fe2O3 was rich in the ash of high-density fractions, especially in the JJM, which can cause severe slagging and fouling problems under reducing atmosphere. The research results contribute to a deeper understanding of the uneven deposition behavior during Zhundong high iron coal combustion process.