Effect of Heating Rate on Glass Transition Temperature of Zonguldak Bituminous Coal

The effect of heating rates in the range of 5-40 K/min on the glass transition temperature of original and pyridine-extracted Zonguldak bituminous coal during pyrolysis experiments under a nitrogen atmosphere was investigated. The initial glass transition temperatures of the original and pyridine extracted coals were measured as 615 and 621 K, respectively. It was observed that the phase transition of the Zonguldak bituminous coal at about 615 K tar evolution was both due to thermal cleavage of covalently bonded material and due to trapped molecules already present in the coal rapidly diffusing out of the physically relaxed macromolecular matrix created by the effect of heat treatment, while the pyridine-extracted coal showed a phase transition slightly at a higher temperature of 621 K, produced material probably by bond cleavage. It seemed that the glass transition temperatures of both original and pyridine-extracted coals were independent of the heating rates.