Characterization of chars made of solvent extracted coals

Thermal extraction of a sub-bituminous coal (Roto south) using 1-methylnaphthalene solvent has produced ash-free coals successfully. The extracted (EC) and residual coal (RC) as well as its parent coal (PC) were pyrolyzed at 300–900 °C and then the carbonized products were characterized. The extracted coal (EC) contained lower molecular weight components than PC and RC, showing much higher fuel ratio after the pyrolysis. EC is expected to be advantageous over PC and RC when applied to coal gasification and reforming, because EC is readily decomposed and volatized. The heating value of EC chars (7,610–8,120 kcal/kg) was independent of the pyrolysis temperature and was higher than those of PC and RC chars, especially for the chars carbonized below 600 °C. The oxygen content of PC chars at T≤600 °C was mostly at least twice that of EC/RC chars, pointing out the difference in the chemical composition. 13CNMR and FT-IR spectra revealed the release of aliphatic hydrocarbons and reactive functional groups with increasing temperature, in agreement with ultimate/proximate analysis results.