A NOVEL ORTHOGONAL MICROSCOPE IMAGE-ANALYSIS METHOD FOR EVALUATING SOLVENT-SWELLING BEHAVIOR OF SINGLE COAL PARTICLES

A novel orthogonal microscope image analysis method was developed to o bserve and evaluate quantitatively the dynamic solvent-swelling behavi or;Ind characteristics of coal particles separated using density gradi ent centrifugation technique. The important results obtained using the new method are as follows: (1) The maximum statistic probability of a nisotropic swelling ratio from 1.1 to 1.3 measured in this work agrees very well with the data measured by Cody et al.; in addition, the sam ples with high vitrinite concentrate and high swelling ratios seem to have high anisotropic swelling feature. (2) The existence of a charact eristic distribution of volumetric swelling ratio in the vitrinite con centrates strongly suggests the existence of a characteristic distribu tion of the molecular weight between cross-link points. (3) The averag e volumetric swelling ratios measured using the new method are compara ble to that measured by the traditional packed bed method. (4) The sim ulated results using modified Painter's disinterspersion model based o n the measured characteristic swelling ratios suggest that each cluste r has aromatic and hydroaromatic rings from 1 to 3 in PDC-HV coal and from 1 to 5 in Witbank coal. Moreover, the relatively short average vi rtual bond length per carbon atom and the random walk of the chains ar e the main features of the coals in pyridine. (5) Although the case II and super-case II are dominant as for diffusion of pyridine in the co al particles, a few cases of Fickian and anomalous diffusion are also existing for two kinds of coal. In addition, because the value of diff usion exponents, n, of some PDC-HV coal samples changes from 0.22 to 0 .39, which does not match to any classical diffusion mechanism, it see ms to be the reflection of one diffusion mechanism.