Properties and structure of hard coals from the borehole Niedobczyce IG-1 in the Rybnik Coal District, Upper Silesian Coal Basin, their petrographic and group constituents. 2. Variations in petrographic composition of the coals along the depth of borehol
Characteristic parameters are given for coal samples from the borehole Niedobczyce IG-1 ranging from gas-flame (611-Ⅶ) to orthocoking (435-VB) types (described in part in the preceding paper) (Fuel Proc. Technol. 41 (1995) 207-220), including the petrographic composition and change trends in this composition and also structure of the macerals. An interesting growth tend in inertinite content was observed, principally semifusinite, with increase in the depth of borehole. The tested coals are characterized by the results of analysis of vitrinites as the most numerous and homogeneous macerals. Vitrinites were examined by the methods of infrared spectroscopy and X-ray diffraction. Petrographic analysis of 60 samples of the coals from the borehole was taken into consideration and spectroscopic analyses were realised for a series of choiced samples of vitrinites. Changes in the coal properties indicate that metamorphism of the organic substance takes place by gradual removal of peripheral fragments of the coal structure together with simultaneous internal regroupings, disproportioning and cyclisation. The effect of this is to give in general lowering in content of aliphatic structures and oxygen groupings and an increase in proportion of aromatic structures. The observed chemical transformations taking place in the tested range of coalification are accompanied by an increase in coal coking capacity, see Part 1. The relatively uniform changes in vitrinites' reflectance suggest a systematic rise in ordering of the aromatic structures (reduction in d_(002) values and rise in L_(002)). Increase in aromaticity indicated by f_(ar) determined for the vitrinites from 0.62 to 0.72 is a consequence, to a greater degree, of the formation of new simple aromatic structures (increase in proportion C-H_(ar)) than of condensation of rings to large aromatic nuclei.