Oxy-fuel combustion of a single fuel particle in a fluidized bed: Char combustion characteristics, an experimental study

The effect of an oxy-fuel atmosphere on char conversion in a fluidized bed (FB) was examined by comparing measurements of single fuel particles exposed to O-2/N-2 and O-2/CO2 atmospheres. The experiments were carried out in a transparent and electrically heated FB at 1088 K and five O-2 inlet concentrations (ranging from 0 up to 40%(vol)) using four ranks of coal (from anthracite to lignite) and one type of wood, all with 6 mm (spherical)-diameter. The evolution of temperature with time of the various fuels at different gas atmospheres and the microstructure of the char resulting after devolatilization are presented, from which the effect of the oxy-fuel atmosphere (changing CO2 by N-2 at different fixed O-2 concentrations) on char combustion characteristics is determined and analyzed. Results show that the apparent average combustion rate of a fuel particle decreases (and consequently the burnout time increases) when changing O-2/N-2 by O-2/CO2. This effect was more significant at high O-2 concentrations and most notable for anthracite. Consistently, the time to reach the peak temperature was longer when shifting from O-2/N-2 to O-2/CO2. However, the char specific surface area, pore volume, and average pore diameter of char were not significantly modified by replacing N-2 with CO2. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.