Swelling coal volume fraction

Accurate determination of the coal volume fraction in the swollen coal particles can be done by calculating and excluding the pore volume, Vp, occupied by the solvent during swelling. Values of the porosity p, expressed according to equation (7) in terms of the pore volume per dry coal weight n, were determined from recent studies for similar coals (13). Where no values of this parameter were available, an interpolation of the porosity versus carbon content data (% C, dmmf basis) was used to determine p. 

Figure 2. Dependence of apparent coal volume fraction at equilibrium swelling on the carbon content (% C, daf), for various American coals. Experimental values of v, app for pyridine vapor swelling 57 . 2°C, 20-30 mesh (extracted coals) (O) 50°C, 30-40 mesh (unextracted coals) (%).

Figure 4. Dependence of apparent coal volume fraction at equilibrium swelling on the oxygen content (% O, daf) of various coals. The three curves represent best fitting of the three sets of Purdue data for American coals. Values for other coals (8, 9) are included for comparison. Experimental values of vg, app for pyridine vapor swelling 57 2°C, 20-30 mesh (extracted coals) (O) 50°C, 30-40 mesh (unextracted coals) (A) 25° C, 30-40 mesh (unextracted coals) (0) Sanada and Honda (1966) 25°C, 30-60 mesh O/ Kirov et al. (1967) 25°C, 50-170 mesh (Ah...

Figure 6. Dependence of true coal volume fraction at equilibrium swelling in pyridine at 57 2°C on the (O) carbon and (%) oxygen contents (%, daf) of various American coal samples.

Free Volume. An increase in the free volume of the macromolecule (or that volume not occupied by the molecules themselves) allows more room for the molecules to move around, and thus an accompanying reduction in the Tg. Therefore, swelling of a macromolecule by a thermodynamically compatible solute (i.e., possessing similar op values as the sorbent) will tend to increase the free volume and lower the Tg (Kelley and Bueche, 1961 Haward, 1973 Barton, 1983). Lucht et al. (1987) developed a relationship between the glass transition temperature of several coals and the weight fraction of pyridine within the coal network,... 

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