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Hydrodynamics and solids mixing behaviour of fluidized beds with inclined-hole distributor

University of British Columbia

Most research on the hydrodynamics and solids mixing of swirling fluidized beds has targeted applications relate to drying and combustion processes, with large mean particle diameters. A potential use of such reactors is in the area of catalyst regeneration to improve mixing. In the present study, the hydrodynamics and solids mixing behaviour of swirling fluidized beds were investigated for particles in Groups A and B of the Geldart classification. Three distributors were designed and fabricated in-house. They shared the same specifications, but differed in the orifice inclination angle (30, 45 and 90 to the horizontal). The effect of orifice angle on the hydrodynamics of a fluidized bed of glass beads was investigated. The study showed that, in an empty bed, the distributor pressure drop was lower for the inclined-hole distributors compared to the 90-hole distributor by a factor of 10%. In addition, bed pressure drop increased with the inclined-hole distributors as well with static bed height. Bed expansion was also investigated and found that in a shallow bed, the inclined-hole distributor led to less expansion compared to the 90-hole distributor. However, in a deep bed, the orifice angle had negligible influence on bed expansion. The minimum fluidization velocity was found to change with static bed height for the inclined-hole distributors, and it was also higher for steeper angles. Solids mixing was also explored, axial mixing for the 90-hole distributor and tangential mixing for all three distributors. Residence time distribution studies were conducted using phosphorescent tracer particles belonging to Group A, activated by ultraviolet light. The turnover time was estimated using the bubbling bed model and found to match the experimental results well. It was found that the probes installed at the walls of the fluidization column reduced the dense phase downward velocity. The tangential particle velocity was also estimated and was found to be highest for the 30-hole distributor, decreasing with increasing orifice angle. A dispersion model was used to describe tangential mixing for all three distributors which showed that the dispersion coefficient for the inclined-hole distributors was twice that for the 90-hole in a shallow bed.

Text

2017-06-22

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/62101

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/