Attrition of high ash Ekibastuz coal in a bench scale fluidized bed rig under O2/N2 and O2/CO2 environments

Abstract

While fluidized bed coal combustion technology has advanced significantly, attrition and its impact on combustion remains a problem. Using a bench scale fluidized bed unit, we examined the experimental attrition data for batches of coal ash particles. Experiments were carried out in the presence of bed material (sand) by adding coal particle to the hot riser, which has a height of 500 mm and internal diameter of 25.4 mm. Combustion of coal particles with high ash content was carried out in both O2/N2 and O2/CO2 environments. Coal particles with sizes of 0.4–0.8 mm and 0.8–1.4 mm were prepared by sieving and examined in this work. Using this data, the effect of critical factors on attrition such as gas velocity, particle size, and combustion environments were analyzed. In addition, the composition of ash particles was analyzed by SEM/EDX and XRF. The sizes of ash particles were less than 0.2 mm after combustion. A higher attrition rate was determined at higher gas velocity, regardless of the combustion environment. The ash composition analysis showed high concentration of silicon and aluminum oxide in the ash, and this possibly was increased due to kaolinite decomposition.