Calorimetric Study of the Heat of Drying of a Sub-Bituminous Coal

This paper presents recently measured heats of drying of Ohai sub-bituminous coal at two temperatures, 50 °C and 75 ° C, using a Calvet type microcalorimeter. The study demonstrates the heat of drying increases with the reducing of moisture content of coal in a pattern such that at least three progressive energy levels are involved. This indicates that there are three types of moisture which co-exist in the tested coal, namely free moisture, loosely bound and tightly bound moisture. These data are valuable in the mathe matical simulation of the spontaneous ignition process in which the effect of moisture transfer is considered. The high heat of drying, as measured in this study, indicates that the extent of the moisture effect on the spontaneous igni tion is beyond 100 ° C.