DEPENDENCE OF SOLVENT SWELLING ON COAL CONCENTRATION

Volumetric solvent swelling of coal is highly dependent on coal concentration, and is significantly enhanced at low concentration. This indicates that associated coal complexes dissociate at low concentration. The dependence of coal concentration on solvent swelling can be expressed by an empirical equation when the concentration is low. The intrinsic swelling ratio, which is independent of the concentration, has been introduced. Solvent swelling approaches a given (saturated) value when the concentration becomes high. The conventionally observed swelling is usually this saturated value. Associative equilibria observed through this swelling imply that significant portions (far more than is generally believed) of coal molecules are physically associated.