1996 Volume 82 Issue 5 Pages 366-371
Coals were heat-treated at the heating rate of 3°C/min or 100°C/min in an autoclave at 200550°C under nitrogen, and then quenched rapidly to room temperature. The heat-treated coals were extracted with a carbon disulfide-N-methyl -2-pyrrolidinone mixed solvent at room temperature. At the heating rate of 3°C/min, the maximum extraction yields were obtained at around the initial stage of softening, and the maximum yields showed a good correlation with the maximum fluidity of the coals. While, ultimate analysis and FT-IR measurement for the heat-treated coals showed that significant structural changes did not occur before the initial stage of softening. In the stages of maximum fluidity and resolidification, the extraction yield rapidly decreased, especially for caking coals. An increase in heating rate to 100°C/min shifted the temperature which gives the maximum extraction yield to higher temperature and the yield was high compared to the low heating rate (3°C/min), suggesting that the fluidity is increased by increasing the heating rate. Softening mechanism of coal was discussed from various coal structure models including associate model.
