DTGA combustion of coals in the Exxon coal library

• Published in: Fuel (Guildford) Vol. 60; no. 6; pp. 458 - 462
• Main Authors: Smith, Stewart E., Neavel, Richard C., Hippo, Edwin J., Miller, Robert N.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.1981
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(81)90103-4

Coal combustion experiments were carried out over the temperature range 25–900 °C using air at atmospheric pressure in a derivative thermogravimetric analysis system. Sixty-six coals high in vitrinite (> 80% mineral-matter-free basis) and low in inorganics (all but 12 samples < 10%) were examined as part of a coal characterization programme. The coals varied in rank from lignites (69% carbon on a dry, mineral-matter-free basis) to low-volatile bituminous (91% carbon). Combustion rates increased progressively with increasing temperature, passed through maxima and then declined. The rate data were fitted to an Arrhenius equation and plots showed four distinct regions of combustion. Apparent activation energies were calculated for each region and varied from ≈4 kJ mol −1 in the high-temperature, diffusion-controlled region to 290 kJ mol −1 in the chemical-reaction controlled, low-temperature region. The temperatures at which 50% of the sample had burned away ( sol1 2 - life ) were rectilinearly related to oxygen and carbon contents (correlation coefficient squared values of 0.88 and 0.86, respectively).