Experimental Quantification of the Lateral Mixing of Binary Solids in Bubbling Fluidized Beds

A novel experimental method for the lateral mixing of binary solids in bubbling fluidized beds was developed based on the capacitance probe technique. The evolutions of local mixing ratios in a fluidized bed which can be assumed as one mixing cell were analyzed in detail. The solids mixing within one mixing cell was resolved and the effect of convection and diffusion mechanism on lateral mixing was evaluated individually. The results show that at lower part of the fluidized bed, convection plays a more important role in the mixing process near the wall; meanwhile, diffusion is very important for the mixing around the center line. This is opposite with that at the higher part. A lateral micro dispersion coefficient was proposed to characterize the lateral mixing within the mixing cell and the value is generally between 0.005 and 0.025 m/s. A new mixing index was proposed to evaluate the lateral mixing quality of binary solids. It was found that at the lower part of the fluidized bed, the best mixing is acquired at the half radius, whereas mixing at the center line is the worst. At the higher part, solid mixing is better when increasing the distance from the wall. The influences of gas velocity and static bed on the lateral mixing were also discussed from a microscopic perspective.

Analysis of a Vortexing Circulating Fluidized Bed for Process Intensification Via High-G Flows

Fluidized beds are used in many industries where gas–solid reactions are present for their favorable characteristics of good solids mixing, high heat, and mass transfer rates, and large throughputs. In an attempt to increase throughput, reduce reactor footprints, and reduce costs, process intensification by unconventional reactor designs is being pursued. Specifically, this work focuses on the development of high-G reactors where the particles are experiencing a centripetal force typically on the order of ten times the force of gravity. This operating regime provides intensified gas–solids contact providing higher mass transfer, heat transfer, and gas throughput than a typical fluidized bed. This work focuses analysis of a cold flow vortexing circulating fluidized bed (CFB). Through mapping the pressure distributions in the riser, insights into the behavior of the system were made and compared to CPFD Barracuda computational fluid dynamic models. The simulation results outlined the working envelope of the system and provided a baseline to compare the experimental results. The experimental pressure data determined angular velocities of the gas in the range of 30–40 m/s, with corresponding particle velocities around 15 m/s.