The effects of heat and mass transfer on the spontaneous heating of coal.
Thesis DisciplineChemical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Low temperature oxidation of coal was carried out in an insulated container in air currents, the velocities of which had been found to be most favourable in the development of spontaneous heatings. Temperature rises, rate of oxidation and drying were recorded. A computer program which solves the equations describing the processes considered to be significant in the initial stages of a heating, particularly the moisture transfer, was separately used to obtain the rate of heating and the rate of oxidation of the experiment. The experimental and calculated results were compared, and the calculated results could be made to fit the experimental results by modifying within the range of known practical data the following constants in the oxidation equation: (i) temperature dependent coefficient, (ii) the order of ,reaction, and (iii) the decrease in the rate of oxidation with the extent of oxidation. Diffusion, the perfect gas law and vapour pressure-moisture content relationship were included in the processes considered. The results showed that the important processes in spontaneous heatings are the oxidation and the evaporation of moisture of coal. Conditions under which heaps of coal are likely to fire are determined.