Publications

Evaluation of effect of particle size on oxy-fuel combustion of pulverized coal

Geier, M.; Hecht, E.S.; Shaddix, Christopher R.

Previous research has highlighted the important role of reduced oxygen diffusivity through the particle boundary layer during oxy-fuel combustion with flue gas recirculation (i.e. high CO2 environments). Single-particle modeling of this process also revealed that partial conversion of the carbon oxidation product CO in the particle boundary layer was important during oxygen-enhanced combustion for particles approximately 130 μm in diameter. In this study, the influence of oxy-fuel combustion conditions on char combustion rates is being investigated both experimentally and through detailed modeling, for several different characteristic pulverized coal particle sizes. Both a high-volatile bituminous coal (Utah Skyline) and a typical PRB low-sulfur subbituminous coal (North Antelope) are being investigated. A combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometer is being used to determine the combustion kinetics of pulverized coal chars when burning in both reduced oxygen and oxygen-enriched atmospheres with either a N2 or CO2 bath gas. Preliminary calculations using the particle combustion code SKIPPY have shown that boundary layer conversion of CO becomes important for oxy-fuel combustion of char particles larger than 60 μm in diameter and, for a char particle reactivity characteristic of high-volatile bituminous coals, the boundary layer reactions result in over a 20% enhancement in the char burning rate for particle sizes between 70-80 μm in diameter. Copyright © (2009) by the International Pittsburgh Coal Conference.