One of the critical requirements to demonstrate the feasibility of oxy-coal combustion on a large scale is to ensure that the scenarios generate gas temperatures and wall radiative fluxes that are identical to those obtained during combustion in air. In order to address this need, ANSYS Inc. and the University of North Dakota are collaboratively employing computational modeling towards improving the fidelity of radiative transfer predictions in these scenarios and identify best practices. One of the goals is to examine the variations in the radiative transfer predictions due to the differences among the commonly employed radiation modeling options employed in the simulations. These include: the sensitivity to mesh size, particle radiative properties, spectroscopic database/emissivity correlations employed to determine the gas-phase radiative properties as well as the impact of gray/non-gray modeling. This paper summarizes the recent progress made towards this effort. As a first step, an assessment of the accuracies of the different modeling options is made by comparing predictions against experimental measurements of radiative heat flux from a front wall fired 300 MW Utility boiler burning coal in air. The predicted temperature, species concentrations and wall incident radiative fluxes were in reasonable agreement against experimental measurements. A 10% difference in the wall incident radiative fluxes was predicted between the gray and non-gray formulations of the WSGGM based on the Perry's Chemical Engineering Handbook emissivity correlations. However, nearly identical wall incident radiative fluxes were predicted by the Perry WSGGM as well as the WSGGM based on the HITEMP 2010 spectroscopic database. The particle as well as the gas-phase made nearly equal contributions to the radiative fluxes. We anticipate some of the best practices established from this study could be extended to simulate oxy-combustion scenarios where boiler measurements at this scale are currently lacking.
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