The role of moisture and oxidation in spontaneous combustion of low rank coals
Clemens, A.H.; Matheson, T.W.
Pages 333-339 1995
The self heating of coal mainly involves exothermic reactions between the coal and oxygen and the moderating or enhancing effect that water has on these reactions. To study them the chemical and thermal responses of dried low rank coals on exposure to a flow of oxygen were monitored and it was found that over the temperature range 30 to 180 degrees C only one exothermic oxidation reaction (involving the breakdown of peroxy compounds to form carboxylic acid/aldehyde products) was responsible for self heating. To study the influence of moisture the thermal and chemical responses of dried and partially dried samples of the low rank coals were studied. It was found that the thermal response of coals in which tightly bound moisture remained was similar to that of the completely dried coal but when loosely bound moisture was allowed to remain in the coal the thermal response on exposure to oxygen fell off quickly. This was due mainly to hindered access to relative sites rather than desorption or any other moderating effect that moisture may have.