Measurements and analysis of CO and O2 emissions in CH4/CO2/O2 flames

Concerns about green house gas emissions have encouraged interest in hydrocarbon combustion techniques that can accommodate carbon dioxide capture and sequestration. Oxy-fuel combustion, where the fuel is combusted in oxygen diluted with steam or CO2, is one promising approach for post-combustion carbon capture. In this paper we focus on CO2 dilution effects and, in particular, on CO and O-2 emissions from these flames. The emissions issue must be considered from a different perspective than conventional power plants as the combustor effluents will be sequestered, and, thus, their interactions with the terrestrial atmosphere are not relevant. CO and O-2 are of interest for these systems as their presence in the exhaust stream represents wasted fuel and oxidizer. In addition, CO2 pipeline specifications impose limitations on CO and O-2 levels, which also must then be controlled either through the combustion process or post gas cleanup. Equilibrium and kinetic modeling of CH4/O-2/CO2 combustion systems was performed in order to analyze CO2 dilution effects upon CO and O-2 emissions level. Companion experiments were also performed in an atmospheric pressure, swirl stabilized combustor. These numerical and experimental results demonstrate the key tradeoffs associated with optimizing these systems, as well as the dependence of emissions on stoichiometry, pressure, CO2 dilution and residence time. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.