Experimental study on oxyfuel-combustion of solid recovered fuel using ilmenite as bed material in a 1 MWth fluidized bed reactor

The transition from coal-based power generation to carbon-neutral alternatives remains a critical challenge in mitigating climate change. Circulating Fluidized Bed (CFB) boilers offer fuel flexibility, enabling the integration of more environmentally friendly biogenic or waste-derived fuels such as Solid Recovered Fuel (SRF). However, replacing conventional fuels with high-volatile alternatives poses challenges related to combustion stability and efficiency. Oxygen Carrier Aided Combustion (OCAC) with ilmenite as a bed material enhances combustion efficiency and reduces emissions by facilitating oxygen transport within the fluidized bed. Additionally, oxyfuel combustion offers a promising pathway for carbon capture but is hindered by high oxygen demand. This study combines OCAC and oxyfuel combustion, presenting the first autothermal Oxyfuel-OCAC (Oxy-OCAC) experiments conducted at the 1 MW_th scale, utilizing 100 % SRF as feedstock. The pilot plant enables oxyfuel operation with wet flue gas recirculation and pure oxygen supply, allowing a controlled transition from air-fired to oxyfuel conditions in 16 min. Differential pressure profiles revealed increasing particle loads in the free board zone with increasing inlet oxygen concentration, leading to a more uniform temperature distribution throughout the CFB reactor. Flue gas analysis confirmed that Oxy-OCAC improves combustion stability compared to oxyfuel combustion with sand as bed material, enhancing oxygen distribution within the reactor. These findings demonstrate that Oxy-OCAC is a promising approach to increasing the efficiency and economic viability of oxyfuel combustion in CFB systems. The combination of ilmenite with SRF in an oxyfuel environment enhances CO₂ capture potential while ensuring stable reactor operation, supporting sustainable energy production.