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

Abstract

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