Conversion Enhancement in a 10 kWth Chemical-Looping Combustion Unit: Effect of Random Metal Packings

Other conference contribution, 2026

Chemical-looping combustion (CLC) is a promising technology for heat and power generation with inherent CO₂ capture. By preventing the mixing of flue gases with nitrogen, CLC eliminates the need for downstream gas separation typically required in conventional combustion systems. CLC applies interconnected fluidized bed reactors and a major challenge is incomplete gas–solid contact, which can result in unconverted volatile gases leaving the fuel reactor. This phenomenon is commonly due to gas bypassing through large bubbles in bubbling fluidized beds, ultimately necessitating an additional and costly oxy-polishing step to achieve complete fuel conversion.

This study investigates the use of random metal packings to counteract gas bypassing and enhance gas–solid mass transfer in a CLC fuel reactor. The underlying concept is to introduce physical hindrance within the bubbling fluidized bed in to disrupt bubble growth, promote a more uniform fluidization pattern, and improve the conversion of volatile gases within the oxygen carrier bed. The packings used in this work are stainless steel thread saddles (known as RMSR packing). The characteristic packing size is 0.025 m, with a nominal bulk density of 228 kg/m³. Due to their high void fraction (>90%), these packings are expected to have only a minor influence on the overall pressure drop, while preventing bubble growth and improving the quality of fluidization.

CLC experiments are carried out in a 10 kWth CLC pilot plant. Ilmenite concentrate is chosen as both the bed material and oxygen carrier. The biomass solid fuel used in the experiments is steam-exploded wood, which is subsequently pelletized to produce black pellets (BP). Experiments are done at different temperatures. The experimental results indicate that the gas conversion efficiency increased from approximately 61% in a conventional bubbling fluidized bed to about 78% by modifying the operating conditions and when the packings are applied. These findings show the potential of random metal packings to enhance conversion performance in CLC systems.