Abstract: Fluidized bed applications where the bed material plays an active role in chemical reactions,\ne.g. chemical looping combustion, have seen an increase in interest over the past decade. When these\nprocesses are to be scaled up to industrial or utility scale mass transfer between the gas and solids\nphases can become a limitation for conversion....Confined fluidized beds were conceptualized for other\npurposes in the 1960â??s but are yet to be applied to these recent technologies. Here it is investigated if\nthey can prove useful to increase mass transfer but also if they are feasible from other perspectives\nsuch as pressure drop increase and solids throughflow. Four spherical packing solids, 6.35â??25.4 mm\nin diameter at two different densities, were tested. For mass transfer experiments the fluidizing air\nwas humidified and the water adsorption rate onto silica gel particles acting as fluidizing solids\nwas measured. Olivine sand was used in further experiments measuring segregation of solids and\npacking, and maximum vertical crossflow of solids. It was found that mass transfer increased by\na factor of 1.9â??3.8 with packing solids as compared to a non-packed reference. With high-density\npacking, fluidizing solids voidage inside the packing was found to be up to 58% higher than in a\nconventional fluidized bed. Low density packing material favoured its flotsam segregation and with\nit higher fluidization velocities yield better mixing between packing and fluidizing solids. Maximum\nvertical cross-flow was found to be significantly higher with low density packing that fluidized,\nthan with stationary high-density packing. Conclusively, the prospect of using confined fluidized\nbeds for improving mass transfer looks promising from both performance and practical standpoints.
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