Chemometric analysis of trace elements distribution in raw and thermally treated high sulphur coals

In the present study, chemometric analysis is applied as a tool to evaluate the release behaviour of trace elements (TEs) during coal utilization processes. Principal component analysis (PCA) and linear discriminant Analysis (LDA) were applied on the TE concentrations of raw and thermally treated coals. PCA and LDA successfully predicted the association of 21 trace elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sb, Te, Pb) contained in coal and their thermal behavior at various temperatures. Application of chemometric on thermally treated coals shows that at temperature 450 °C, elements like Na, P, K, Fe, Ca, Mg, Al and Si have affinity with mineral matter and therefore have low volatility. Elements like Te, Sb and Ti may form their chlorides, which enhance the volatilities of these elements, while Co and Pb may form sulfides like Co2S4 and PbS. In the temperature range of 600–850 °C, either coal undergones an intense degradation of its structure during pyrolysis and the elements released may be adsorbed on coal surface or be volatile. The elements Cr, Co, V, Ni may react with sulphurous gases evolved during pyrolysis. At temperature 1000 °C, wide dispersion in data elements interact with carbon and sulphur compounds of coals. The formation of compounds like Si carbide, bassanite, gehlenite, anarthite may also be responsible for low volatilities of the elements Si, Al and Ca at higher temperatures. Predictive capabilities of PCA and LDA were evaluated in terms of TEs volatilities at different temperatures. The results of chemometric analysis are not only in good agreement with volatilities of TEs present in coals at various temperatures but also with FTIR analysis.