Author(s)

T. Zelenka

Abstract

Various pre-treatment procedures like hot oven drying under and without vacuum, purging with an inert gas at elevated temperatures, lyophilisation and long-term drying in a desiccator were applied on a sample of a subbituminous coal. Variously dried samples with known residual moisture contents were interpreted according to the microporous textural parameters. Adsorption isotherms of CO2 at 30°C were determined using a volumetric sorption analyser. Adsorption data were evaluated according to Dubinin–Radushkevich and Medek’s equation in order to determine micropores’ volume and micropores’ surface and modus of the micropores’ radii. It was found that the drying method has an influence on the microporous textural properties. Samples which were not exposed to oxygen during drying (vacuum drying, inert gas purging) have better micropore characteristics; likely due to the lower contents of the residual moisture in the order of a few tenths wt.%. If a sample is exposed to an oxidizing atmosphere at a comparable temperature and drying time, the reduction of the textural parameters was observed. It may be explained by a higher residual moisture content of this sample (1.4 wt. %). The effect of the drying temperature has not been clearly proven despite the fact that mean Smi and Vmi parameters have an increasing tendency with a decreasing drying temperature. It was also found that 2 hours is an effective time for the vacuum drying process at 60°C; even despite the difference in residual moisture contents of these samples. Keywords: subbituminous coal, pre-treatment procedure, surface area, micropores.

Keywords

subbituminous coal, pre-treatment procedure, surface area, micropores