- MSc studentm Saeid Davam at Chalmers University of Technology. His 2026 master’s thesis, “Chemical Looping Combustion of Solid Biomass in a Packed-Fluidized Bed Reactor,” was supervised by Nasrin Nemati at the Department of Environmental and Energy Sciences, with Magnus Ryndén serving as examiner.
Abstract:
Chemical Looping Combustion (CLC) is a promising carbon capture technology that inherently separates CO₂ during fuel oxidation in fluidized bed, reducing the need for energy intensive gas separation. A key limitation of conventional fluidized bed CLC reactors is that at higher gas velocities, bubble size increases, which reduces gas–solid mass transfer and limits fuel conversion efficiency. This study investigates the effect of introducing packed materials into a fluidized bed CLC reactor forming a Packed-Fluidized Bed Reactor (PFBR) to address this limitation.
Batch experiments were conducted in a laboratory-scale reactor at 900°C using ilmenite as bed material and oxygen carrier. Two biomass fuels were tested: wood pellets and torrefied wood pellets. Two packing materials were evaluated: random metal-thread saddle rings (RMSR) and expanded clay aggregate (ECA). Experiments were performed at superficial gas velocities of 0.15 m/s and 0.3 m/s, and fuel conversion performance was assessed through CO₂ yield calculations based on carbon mass balances.
The results show that both packing materials significantly improve CO₂ yield compared to the unpacked configuration. For wood pellets at 0.15 m/s, the average CO₂ yield increased from 73.0% without packing to 91.8% with RMSR and 88.3% with ECA. Torrefied wood pellets consistently achieved higher CO₂ yields than wood pellets under all conditions. This is due to their lower volatile matter content, which leads to reduced bubble formation during devolatilization, as well as their higher fixed carbon content, which increases the overall carbon available for conversion to CO₂. Increasing the superficial gas velocity from 0.15 to 0.3 m/s led to decreased CO₂ yields in packed configurations, due to shorter gas residence times and dilution effects. ECA packing exhibited material losses at 0.3 m/s, likely due to co-fluidization and attrition. Overall, RMSR packing demonstrated superior and more stable performance across all tested conditions.