Moisture readsorption and low temperature oxidation characteristics of upgraded low rank coal

This study investigated the behavior of upgraded low rank coal produced by a coal–oil slurry dewatering process regarding moisture readsorption, low temperature oxidation, and spontaneous combustion. The upgraded low rank coal had higher heating values than raw coal. It also showed lower moisture readsorption than raw coal and had less susceptibility to low temperature oxidation and spontaneous combustion. This seemed to result from the coating of the asphalt on the surface of the coal, which covered fine pores and suppressed the active functional groups from reacting with moisture and oxygen in the air. The increasing upgrading pressure negatively affected the moisture readsorption, low temperature oxidation, and spontaneous combustion.

► Moisture readsorption and low temperature oxidation of upgraded low rank coal.
► Coal was upgraded by coal–oil slurry dewatering process with heavy oil addition.
► Upgraded coal showed lower moisture readsorption than raw coal.
► Upgrading suppressed low temperature oxidation and spontaneous combustion of coal.
► Increasing upgrading pressure affected moisture readsorption and CPT negatively.