Conversion of low-grade coals in sub-and supercritical ...
Conversion of low-rank coal in high temperature water can obtain high-quality solid fuel. It is an effective method for upgrading low-rank coals extensively, lignite treated by hydrothermal process contains lower oxygen content due to the decrease of –OCH 3 (methoxyls) and –COOH (carboxyls), these oxygen functional groups can decompose easily even at a …