Ignition behavior of single coal particle in a fluidized bed under O2/CO2 and O2/N2 atmospheres: A combination of visual image and particle temperature

Single coal particle ignition behavior was studied in a two-dimensional (200 mm x 20 mm x 400 mm) fluidized bed under O-2/N-2 and O-2/CO2 atmosphere with O-2 volume concentration in the range of 0-40%, by a combination of visual observation of the volatile flame and measurement of the particle center temperature. A piece of transparent quartz glass was used as the front wall of the fluidized bed to allow visual observation. The investigated fuel particles were spherical sub-bituminous coal particles with diameter in a range of 6-13 mm, which were artificially carved from selected original coal particles. The volatile combustion flame was recorded by a color video camera to analyze its ignition time delay and extinction behavior. The temperature in the particle center was measured by a very thin thermocouple to follow the particle heating process. Results indicate that under O-2/CO2 atmosphere the ignition delay time is much longer than in O-2/N-2 atmosphere. The devolatilization process is controlled by internal and external heat transfer but it is almost unaffected by atmosphere at the same O-2 concentration. The effect of volatile combustion on heating and extinction delay time can be neglected for larger coal particles. (C) 2013 Elsevier Ltd. All rights reserved.