WATER-ADSORPTION AND SMALL-ANGLE X-RAY-SCATTERING STUDIES ON THE EFFECT OF COAL THERMAL-TREATMENT

The effect of thermal treatment, at a relatively high temperature (sim ilar or equal to 340 degrees C), on two high-volatile bituminous coals is examined by water adsorption and small angle X-ray scattering (SAX S). The results suggest that the mesopore structure in both samples un dergoes a partial collapse. Furthermore, a strong hydrophobic effect, at the very early stages of the adsorption process, is noted for only one of them. This observation is attributed to differences in the rigi dity of each of the structures. Analysis of the spectra in terms of fr actal geometry is also performed. It is proposed that thermal treatmen t changes the coal matrices from a dilute to a dense configuration. He ating causes a breakage of some oxygen and sulphur bridges giving rise to these structural alterations. Copyright (C) 1996 Elsevier Science Ltd