Separation of coal macerals

Density gradient technique offers significant advantages over previous methods of maceral separation. It provides a rapid method of measuring the overall density ranges of the various macerals and of separating macerals having any density range desired. Of course, the smaller the fraction cuts, the less coal per fraction. Current fractions range between 0.007 to 0.010 g/cc. To obtain the same range using sink-float techniques would require over 40 separate stages. As the results show, good success were obtained with PSOC-297 and -124 coal samples using the DGC technique, although micrinite presents some problems. In the case of PSOC-297, the micrinite contribution does not drastically affect the material in which it is mixed, e.g., vitrinite is still over 90% pure. In the case of PSOC-124 much more exinite material is contaminated by micrinite inclusion, undoubtedly because of the very high micrinite concentration initially present. Two important points can be made from this study. First, the broad distribution of densities for exinite and inertinite and the corresponding large drop in H/C ratio for the exinites suggests large changes in chemical structure must be occurring. Thus, caution must be used in studying the properties of exinites and inertinites to insure that structural informationmore » is based on narrow range density fractions. In fact, this is probably why in the past the properties, both chemical and physical, have much broader limits for exinites and inertinites. Second, the density range for vitrinites is relatively narrow in both coals, suggesting that the properties of vitrinite should be generally less erratic and therefore considerably more predictable.« less