Influence of particle sizes on combustion characteristics of coal particles in oxygen-deficient atmosphere

The combustion characteristics of coal samples with different particle size were investigated using a thermogravimetric analyzer. Three different heating rates were set in the oxygen-deficient atmosphere of 12 vol % oxygen concentration. Experiments were conducted on four particle sizes with a diameter of 0.6,1.0, 2.0, and 4.0 mm. It was found that ignition and burnout temperatures of coals rose approximately linearly with the increasing particle size. The ignition temperature of the coal with a diameter of 4.0 mm (482 degrees C-520 degrees C) varied greatly at different heating rates compared with that of 0.6 mm (473 degrees C-481 degrees C). The effect of particle size on the ignition temperature decreased with the increase in heating rate, while the effect on the burnout temperature was promoted. The calculation of the combustion index and the results of the kinetic analysis indicated that the reactivity decreased as the coal particle size increased. The results of this paper can provide guidelines for the development of a staged fuel-feeding horizontal circulating fluidized bed boiler. (C) 2019 Elsevier Ltd. All rights reserved.