The Effect of Drying Heat and Moisture Content on the Maximum Temperature Rise During Spontaneous Heating of a Moist Coal Pile

Abstract

Recent work has suggested that the moisture of a sub-bituminous coal may exist in three forms, namely free moisture, loosely bound moisture and tightly bound moisture (these moistures do not include chemically bound moisture). The complete drying of each type of moisture requires a stepwise changing amount of energy, known as the heat of drying. This stepwise change in the heat of drying in relation to the moisture content of coal was, in the current study, incorporated into a mathematical model that describes the spontaneous heating process. More detail of the influence of moisture transfer on the maximum possible temperature rise in moist coal piles are revealed. Comparison between the predicted temperature levels and the published experimental observations provided greater confidence in using the proposed mathematical model and the physical and chemical parameters to predict quantitatively the spontaneous ignition process.

Keywords:

• Coal oxidation
• drying
• spontaneous combustion
• moisture content
• heat & mass transfer