Impact of random packing on residence time distribution of particles in bubbling fluidized beds: Part 1–cross-current flow reactors

Journal article, 2025

In this work, the influence of employing random packings on the residence time distribution in a bubbling fluidized bed is investigated. The bubbling fluidized bed cold-flow reactor setup allows for continuous cross-current flow of particles. Expanded clay aggregate (ECA) is employed in the packed-fluidized bed experiments as the packing. The effects of different parameters such as packing type (ECA or no packing), Fluidization number (4.4, 6.6, and 8.8), and solid throughflow rates (92, 133, and 164 g/s) are investigated. The axial dispersion and tank-in-series models are used to categorize flow patterns of particles in the packed-fluidized beds and compared to beds using no packing. Results show that the vessel’s dispersion number for solids decreases in the presence of ECA packings up to fourfold compared to unpacked beds. Furthermore, tank-in-series model shows that the number of tanks for experiments utilizing packing increases by up to threefold compared to unpacked beds. The experimental results are also compared to a model known as a hybrid model. The hybrid model considers a continuous-stirred-tank-reactor in series with a plug-flow-reactor. Comparison of the model to the measured data shows a clear shift of the relative size or residence time from the stirred tank reactor towards the plug flow reactor with axial dispersion in the packed-fluidized bed compared to a bed with no packing. Also the vessel dispersion number of the plug flow reactor model with axial dispersion is significantly decreased in the case of packed-fluidized bed.