Comparative study of low-temperature pyrolysis and solvent treatment on upgrading and hydro-liquefaction of brown coal

Low-temperature pyrolysis (LTP) and solvent treatment (Sol-T) of Yunnan brown coal were conducted for purpose of comparing their effects on upgrading and hydro-liquefaction. Sol-T is effective in both dewatering and deoxygenation of the brown coal. LTP is also effective in dewatering but less effective in deoxygenation, and more extensive cross-linking occurred during LTP than in Sol-T. Sol-T at mild temperatures (less than 200 °C) enhances coal conversion and oil yield during hydro-liquefaction, while treatment at above 250 °C lowers coal conversion and oil yield. LTP of brown coal is definitely detrimental to its hydro-liquefaction, as both conversion and oil yield are significantly reduced. Thus, Sol-T at mild temperatures is more preferable for upgrading brown coals prior to their use in hydro-liquefaction.