Flamelet LES of oxy-fuel swirling flames with different O₂/CO₂ ratios using directly coupled seamless multi-step solid fuel kinetics

Oxy-fuel combustion, in combination with carbon capture technologies, has generated significant interest since it has a high potential for rapid CO₂ cutbacks for newly built and retrofitted coal-fired power plants. Although research and development of oxy-fuel combustion technologies have been advancing recently, the combustion of solid fuels in an oxygen–carbon dioxide environment is not yet fully understood. In particular, the oxygen content in the recirculated flue gas is an adjustable parameter in oxy-fuel combustion. This work aims to analyze its impact on the thermo-chemical conversion by applying a recently developed approach for accurately predicting pulverized solid fuel combustion to a range of oxy-fuel swirl flames. The employed modeling framework builds upon a detailed solid fuel kinetic mechanism that seamlessly describes the entire solid conversion process. For the description of the gas phase, a combined flamelet modeling approach with large-eddy simulation is applied. This previously introduced high-fidelity framework (Nicolai et al., 2022) was applied to three operating points in a pilot-scale facility, for which in-reactor data is available. The overall model, combined the available experimental data, is employed for the three operating points with different oxidizer O₂/CO₂ ratios to give deeper insights into combustion. In particular, the influence of the local oxygen partial pressure on the solid fuel conversion is analyzed in detail.