A new three-dimensional microscopic image analysis method was developed to observe and evaluate quantitatively the dynamic swelling behavior and characteristics of coal macerals in solvent. The most important result obtained using this new method is: the existence of characteristic multi-peak distribution of volumetric swelling ratio in the coal macerals strongly suggests the existence of characteristic multi-peak distribution of the molecular weight between cross-link points. Therefore, the results seem to be new direct evidences to prove the concept of physically associated model of coal structure.
