Gas-Solid Flow Study of Multistage Fluidized Bed Red Mud Reduction Reactor with Downcomer

Multistage fluidized bed reactors with downcomers are widely conducted for red mud reduction due to their excellent residence time distribution and multiple dense phase zones, which result in favorable reaction characteristics. Furthermore, in the fluidized bed reactors, gas-solid flow plays an essential role in chemical reactions. However, the complex structure of multistage fluidized bed reactor make the study the gas-solid flow challenging, especially when the particles have an extremely fine size.

In this paper, a cold-test rig for a multistage fluidized bed cold test rig was constructed. Using experimental methods, appropriate size and structure of downcomers were determined to ensure the rapid transfer of solid between the upper and lower bed. Additionally, the distribution of gas residence time in multistage fluidized bed was obtained by using CO₂ tracer and function fitting noise reduction. The average gas residence time is 13.72 s and 50% longer than the single stage bed which is theoretically 9.09 s.