THE EFFECT OF PROCESSING ON THE FRACTAL PORE STRUCTURE OF VICTORIAN BROWN COAL

Using small angle X-ray scattering we show that the pore surfaces of Victorian brown coal in unprocessed and various processed states may be described by fractal concepts. Furthermore, values of the surface fractal dimension, Ds, and the surface measure, N0, extracted from the SAXS data are shown to be very sensitive to the processing conditions used. In all cases at low processing temperatures little change is seen in the pore surfaces. However, for “raw” coal processed in hydrogen-rich atmospheres Ds increases and N0 decreases dramatically and sharply at processing temperatures of around 325°C. This effect, which is interpreted as pore collapse, is shown to be consistent with other features of the coal. By contrast if the coal is merely heated in an inert nitrogen atmosphere or acid-washed coal is used then the pore surfaces appear to be little affected by the temperature of processing. © 1993 by Academic Press, Inc.