Chemical-looping combustion in packed-fluidized bed reactor: Experimental and modeling investigation into the effect of random metal packings

Paper in proceeding, 2024

Chemical-Looping-Combustion (CLC) presents a promising technology for heat and power generation while concurrently facilitating CO2 capture. It prevents the mixing of flue gases with air, eliminating the need for post-combustion gas separation. However, a key challenge within CLC lies in mitigating reduced gas-solid mass transfer, necessitating expensive post treatment such as oxy-polishing. This could mean reduced contact between gas and solids in the fuel reactor, crucial for achieving optimal conversion.

This study investigates the impact of random metal packings RMSR (stainless steel thread saddles) and Hiflow (stainless steel pall rings) on fuel conversion and mass transfer in the fuel reactor. These packings have a void factor >90% and could be expected to have a limited impact on pressure drop and solid flux. CLC experiments are conducted in a stainless-steel reactor with I.D. of 7.8 cm with the gaseous fuels of syngas and carbon monoxide. Findings indicate that packings exhibit a noteworthy enhancement in syngas conversion, reaching 100% at 840°C and bed height 40 cm or higher, thereby suggesting their potential to facilitate complete fuel conversion and obviate the necessity for post-combustion treatment.

To study this further, a mass-transfer model is introduced to analyze the different mass-transfer steps (intra-particle, particle surface to emulsion gas, and emulsion gas to bubble gas) in the reactor. Model analysis shows that the main resistance for mass transfer occurs across the bubble-emulsion boundary. The incorporation of packings enhances the mass transfer coefficient across this boundary by up to 23% compared to conventional beds, underscoring the ability of packings to improve CLC performance.