Forces on an Immersed Horizontal Baffle Made of Multiple Inclined Slats in Fluidized Beds

Baffles made of multiple inclined slats are often used in fluidized bed reactors to improve gas-solids contact and optimize residence time. However, the baffles have to suffer continuous dynamic forces induced by vigorous bubble and particle motion in beds. The information on the dynamic forces acting on immersed baffles is very helpful to their reasonable strength design. In our previous study^[1], forces on a single horizontal slat were investigated systematically, which is usually placed in the bed center in experiment. For the horizontal baffles made of multiple slats used in fluidized bed reactors, information on forces acting on slats at different lateral positions and the influence of major geometrical parameters on forces on slats are more interested. In this study, distribution of forces on different slats of an immersed horizontal baffle made of multiple inclined slats and the influence of slat pitch were measured in detail.

The experiment was conducted in a cold fluidized bed with a square cross-section of 300 mm×300 mm. The horizontal baffle made of multiple slats with an inclined angle of 45^o were inserted in the bed at height of 500 mm from the bottom distributor. One of the inclined slats is test slat that adhered strain gauges on its surface. The bed material was coarse silica sand belonging to Group B particle. The force distribution of slats located at different lateral positions and effect of slat pitch were investigated by moving the position of the test slat and changing the number of inclined slats in the experiment.

The distribution of forces on the different slats shows the forces on the slat located far from the oriented side of the baffle were much larger than that at other positions, which resulting from guide fuction of the baffle. The forces on the test slat located in bed center with increasing slat pitch indicates that forces on the slats made up of the baffle significantly decreased when the slat pitch was less than 71 mm, especially at high superficial gas velocity. However, the forces increased a little when the pitch was larger than 71 mm. The forces on the slat with a small distance of 35 mm was about 1/3 of forces on a single slat immersed in a freely fluidized bed (i.e. L_s=104 mm). This result demonstrates that decreasing the distance of inclined slats is an effective measure to reduce dynamic forces on the horizontal baffles immersed in fluidized beds.

[1] D. Liu, S. Zhang, R. Wang, Y. Zhang. Dynamic forces on a horizontal slat immersed in a fluidized bed of fine particles. Chemical Engineering Research & Design, 117 (2017): 604-613.