Nongray EWB and WSGG Radiation Modeling in Oxy-Fuel Environments

TL;DR

This paper reviews recent developments in nongray radiative property models for oxy-fuel combustion, emphasizing five WSGG-based models and their performance in environments with varying H2O and CO2 concentrations.

Contribution

The paper introduces and compares five new WSGG-based radiative property models specifically designed for oxy-fuel combustion environments.

Findings

Models show varying accuracy depending on H2O and CO2 mole fractions.

All models effectively handle environments without N2 dilution.

Performance differences highlight the importance of environment-specific modeling.

Abstract

According to a recent U.S. Greenhouse Gas Emissions Inventory (1), about 42% of 2008 CO$_2$ (a greenhouse gas) emissions in the US were from burning fossil fuels (especially coal) to generate electricity. The 2010 U.S. International Energy Outlook (2) predicts that the world energy generation using coal and natural gas will continue to increase steadily in the future. This results in increased concentrations of atmospheric CO$_2$, and calls for serious efforts to control its emissions from power plants through carbon capture technologies. Oxy-fuel combustion is a carbon capture technology in which the fossil fuel is burned in an atmosphere free from nitrogen, thereby significantly reducing the relative amount of N$_2$ in the flue-gas and increasing the mole fractions of H$_2$O and CO$_2$. This low concentration of N$_2$ facilitates the capture of CO$_2$. The dramatic change in the flue composition results in changes in its thermal, chemical, and radiative properties. From the modeling point of view, existing transport, combustion, and radiation models that have parameters tuned for air-fuel combustion (where N$_2$ is the dominant gaseous species in the flue) may need revision to improve the predictions of numerical simulations of oxy-fuel combustion. In this chapter, we consider recent efforts done to revise radiation modeling for oxy-fuel combustion, where five new radiative-property models were proposed to be used in oxy-fuel environments. All these models use the weighted-sum-of-gray-gases model (WSGGM). We apply and compare their performance in two oxy-fuel environments. Both environments consist of only H$_2$O and CO$_2$ as mixture species, and thus there is no N$_2$ dilution, but the environments vary in the mole fractions of these two species.