Hydrothermal treatment of the blend of lignite and rapid hydrogasification char for preparing slurry fuels

The char produced from the rapid hydrogasification (RH char) has a high carbon content, a low volatile matter content and a high calorific value, whereas lignite has high contents of oxygen and volatile matter and a low calorific value. These two carbonaceous fuels are complementary to each other for making CWS, but both of them are poor in slurryability. Hydrothermal treatment (HTT) is consequently used to improve the slurryability of the blend. HTT experiments were carried out in a stirring autoclave at 150-320 °C with a holding time of 30 min. Two types of feedstock were found to have some interactive effects during HTT on changing the elemental composition, acidic functional groups, particle size distribution, particle morphology and water holding capacity in or of the treated blend. The slurryability of the blend is appreciably improved by HTT, and the extent of improvement increases with the temperature increasing till 300 °C but not to a higher temperature. The reasons for the slurryability changed after HTT are discussed.