Effect of CO 2 gasification reaction on oxy-combustion of pulverized coal char Ethan S. Hecht a,⇑ , Christopher R. Shaddix a , Alejandro Molina b , Brian S. Haynes c a Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550, USA b School of Processes and Energy, Faculty of Mines, National University of Colombia, Medellı ´n, Colombia c School of Chemical and Biomolecular Engineering, University of Sydney, Sydney, New South Wales, NSW 2006, Australia Abstract For oxy-combustion with flue gas recirculation, as is commonly employed, it is recognized that elevated CO 2 levels affect radiant transport, the heat capacity of the gas, and other gas transport properties. A topic of widespread speculation has concerned the effect of the CO 2 gasification reaction with coal char on the char burning rate. To give clarity to the likely impact of this reaction on the oxy-fuel combustion of pul- verized coal char, the Surface Kinetics in Porous Particles (SKIPPY) code was employed for a range of potential CO 2 reaction rates for a high-volatile bituminous coal char particle (130 lm diameter) reacting in several O 2 concentration environments. The effects of boundary layer chemistry are also examined in this analysis. Under oxygen-enriched conditions, boundary layer reactions (converting CO to CO 2 , with concomitant heat release) are shown to increase the char particle temperature and burning rate, while decreasing the O 2 concentration at the particle surface. The CO 2 gasification reaction acts to reduce the char particle temperature (because of the reaction endothermicity) and thereby reduces the rate of char oxi- dation. Interestingly, the presence of the CO 2 gasification reaction increases the char conversion rate for combustion at low O 2 concentrations, but decreases char conversion for combustion at high O 2 concentra- tions. These calculations give new insight into the complexity of the effects from the CO 2 gasification reac- tion and should help improve the understanding of experimentally measured oxy-fuel char combustion and burnout trends in the literature. Ó 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Coal combustion; Gasification; Oxy-fuel; CO 2 recycle 1. Introduction With growing concern regarding the impact of continued CO 2 emissions on the environment, one strategy to reduce CO 2 emissions is to apply oxy- combustion of coal with flue gas recirculation and carbon sequestration. This strategy has received considerable attention as a viable, cost-effective technology for power production and can be used as a retrofit on existing coal-fired power plants. In a review of several studies, Buhre et al. find CO 2 capture from oxy-combustion to be more eco- nomical than conventional air-fired combustion 1540-7489/$ - see front matter Ó 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.proci.2010.07.087 ⇑ Corresponding author. Address: Sandia National Labs., MS 9052, 7011 East Avenue, Livermore, CA 94550, USA. Fax: +1 925 294 2276. E-mail address: ehecht@sandia.gov (E.S. Hecht). Available online at www.sciencedirect.com Proceedings of the Combustion Institute 33 (2011) 1699–1706 www.elsevier.com/locate/proci Proceedings of the Combustion Institute