Implementing oxyfuel combustion in waste-to-energy: Analysis of flue gas recirculation strategies using a combined modeling and thermal analysis approach

Given the potential of oxyfuel combustion for carbon capture, the impact of flue gas recirculation on oxyfuel combustion in Waste-to-Energy is investigated using a combined modeling and thermoanalytical approach, providing the basis for technical implementation. The oxyfuel combustion model reveals distinct gas compositions and flow rates for different recirculation strategies. Recirculation before flue gas treatment results in high pollutant concentrations in the oxidizer mixture but reduces the volume flow in downstream units. Recirculation after flue gas treatment lowers pollutant levels and, as in the first case, shows high H 2 O concentrations in the oxidizer mixture. Dry flue gas recirculation achieves the highest CO 2 concentration but also the highest relative N 2 content in the clean, dry flue gas. By recirculating a larger absolute amount of O₂ to the oxidizer mixture, dry recirculation reduces the O₂ demand by 11.6% compared with wet recirculation. Thermogravimetric and differential thermal analysis of refuse-derived-fuel examines the influence of O 2 and H 2 O concentrations on combustion performance. Increasing O 2 concentration strongly promotes char combustion, while devolatilization is slightly affected. Achieving similar combustion and burnout as with air, requires 32–35 vol-% O 2 in CO 2 . Higher H 2 O content slightly enhances char combustion, indicating a positive effect of the wet recirculation.