(85g) Dynamic Forces Induced By Geldart Group a and Group B Particles in Fluidized Bed Systems

Fluid bed internals such as heat exchanger tube bundles and baffles are subject to random buffeting forces induced by rising bubbles and particle motion in the bed. To understand and quantify these forces, a piezoelectric force sensor was mounted in a 2-D Plexiglas column, 30 cm wide and 2.5 cm deep for a visual depiction of the phenomenon. The magnitude of these forces not only depended on momentum and residence time of bubbles when they were in contact with the sensor, but also on the material that was being tested. Tests were conducted with fluid catalytic cracking catalyst particles (Group A) and glass beads (Group B). The average forces induced by these materials were compared at different fluidization regimes, ranging from a single bubble that was injected at minimum fluidization, as well as in a bubbling and turbulent bed. Tests were also done to quantify the forces during the startup of the bed, when there was no aeration. It was found that glass beads on average generated greater forces during the startup of the bed, as well as during subsequent fluidization. The larger bubbles sizes of Group B material moving with a greater momentum generated higher forces when they came into contact with the sensor. This is an important criterion in the design and fabrication of internals to mitigate structural damages.