Insights into gas-solid flow structures in fluidized beds up to 1600 °C via analysis of gas residence time distributions

This study investigates gas residence time distributions (RTDs) in a fluidized bed of Al2O3 particles at temperatures ranging from ambient to 1600 degrees C, focusing on the impact of temperature on gas back-mixing and flow patterns. We find that at low temperatures (up to 300 degrees C), gas flows in a near-plug flow pattern, represented by narrow RTD curves with early peaks. As temperature increases to 600 degrees C, the RTD curves broaden, featuring delayed peaks due to bubble breakup and enhanced gas drag. Between 800 degrees C and 1200 degrees C, significant deviations from plug flow emerge, driven by stronger interparticle forces and increased gas transfer to the emulsion phase. Interestingly, beyond 1200 degrees C, the RTD curves shift back toward plug flow, influenced by intensified interparticle forces and physicochemical changes in the bed materials.