Comprehensive Analysis of the Effect of Oxyfuel Atmospheres on Solid Fuel Combustion Using Large Eddy Simulations

Abstract

Coupling oxyfuel combustion with carbon capture and storage (CCS) technologies offers a promising near-term solution for cleaner power generation. For understanding the effects of varying operating conditions, this study employs a Large Eddy Simulation (LES) approach coupled with advanced radiation and solid fuel conversion models, using six-dimensional flamelet tabulation and Lagrangian particle tracking. The framework is applied to a lab-scale swirl-stabilized methane-assisted solid fuel combustion chamber operated with pulverized Rhenish Lignite. Three single-phase methane flames and three comparable multiphase methane/coal flames are investigated. In both single-phase and multiphase conditions air serves as the reference oxidizer. Two additional oxyfuel operation modes are analyzed, both having 33 \% vol. \ce{O2}: One maintaining constant thermal power and the other maintaining constant feed flow rates, both compared to the respective single-phase or multiphase air case. The simulations are validated using uniquely comprehensive experimental data and are shown to capture key differences between operating conditions. A weaker swirl-stabilization is observed in same-power multiphase oxyfuel condition, explained by the drag force of particles and lower gas velocities. Furthermore, particle size and residence time distributions within the flame are calculated, revealing a higher tendency for particles in the intermediate size range to escape the air flame compared to oxyfuel flames.

Keywords: Oxyfuel, Pulverized coal combustion, Flamelet-LES