Oxidation rates of coals as measured from one-dimensional spontaneous heating

A study of the oxidation rates of several coals from New Zealand is reported for temperatures below similar to 100 degrees C. Extensive oxygen analyses during one-dimensional spontaneous heating, using an adiabatic (2 m long) column filled with similar to 110 kg of crushed coal particles, yielded oxidation rates. Scatter in the kinetic plots was due to the experimental technique and a variety of complications, e.g., shrinkage of the coal bed, oxidation aging and moisture transfer (evaporation, condensation, drainage, etc). This work demonstrates the difficulty of relating adiabatic laboratory experiments to the spontaneous heating and ignition of piles of stored coal. (C) 1997 by The Combustion Institute.