Water Adsorption and Desorption of Upgraded Brown Coal. Part 1: Isotherms of Adsorption and Desorption

Isotherms of water adsorption and desorption of upgraded brown coal (UBC) were compared to those of its feedstock coals, dried and not dried. The shape of isotherms showed that UBC was exposed to an irreversible collapse of capillaries by losing its original water, as was dried feedstock coal. By analyzing isotherms from the viewpoint of heat of adsorption and heat of wetting, the affinity of UBC to its adsorbed moisture was found to be smaller than that of its dried feedstock coal. This may be caused by the oil adsorbed onto its surface during slurry dewatering of the UBC process. The heat of wetting of UBC was smaller than those of its feedstock coals, which were dried. As far as UBC has the equilibrium moisture under normal ambient conditions, the risk of hot pile because of heat of wetting seems to be reduced.