Changes in char structure due to inorganic matters during anthracite pyrolysis

- The effects of inherent and externally-added inorganics on char structure were carefully examined.
- The inherent minerals, Al2O3, SiO2, and CaO have all increased the disordering degree of chars.
- The addition of Fe2O3 has decreased stacking height and crystallite width simultaneously.

To understand effects of inherent mineral matters on the evolution of char structure, the microcrystalline structures of chars from the pyrolysis of raw, HCl-washed (CW) and HCl&HF-washed anthracites (CFW) were investigated by X-ray diffraction (XRD) respectively. Stacking height (Lc), interlayer spacing (d002) and crystallite width (La) were used as parameters for char structure estimation. The results showed that with increasing contents of inherent mineral matters, Lc of char decreased, whereas d002 and La increased. To study effects of a single inorganic matter, CFW was impregnated with Al2O3, SiO2, and CaO respectively. It was found that all of them (oxides) have resulted in the decrease in Lc and increase in La and d002. Differing from Al2O3, SiO2, and CaO, the introduction of Fe2O3 has caused the reduction for both La and Lc values simultaneously, especially when the Fe2O3 contents in the coal were high.