Impact of Gas Release on the Mixing of Large Particles in Bubbling Fluidized Beds

Abstract

This study experimentally investigates solids mixing within a bubbling fluidized bed using a fluid-dynamically downscaled cold model and Magnetic Particle Tracking technology. The trajectories of gas-releasing tracers were tracked and compared to blank tracers to analyze the impact of gas release on mixing for various tracer densities and fluidization numbers. Lateral mixing was quantified using Einstein’s equation for Brownian motion, and probability density functions was utilized to analyze the axial position and velocity distribution of the tracers. The results indicate that gas release significantly enhances the lateral mixing of low density tracers at high fluidization numbers, while it has a more pronounced effect on the mixing of heavy tracers at low fluidization numbers. Additionally, gas release affects the vertical distribution of tracers in a complex manner, depending on the tracer density and fluidization number. Gas-releasing tracers with low density tend to immerse more into the bed at low fluidization numbers, while high-density gas releasing tracers tend to remain at higher axial positions. The impact of gas release on the velocity of the tracers is significant only at high gas release rates, for which the force balance on the tracers seems to be impacted, causing higher fluctuations in the velocity.