A COMPUTATIONAL STUDY FOR AIR-€“SOLID PARTICLES FLOW PATTERNS IN RIB-ROUGHENED FLUIDIZED BED VESSELS

Abstract

This paper includes analysis of the flow of air and solid particles in fluidized bed units using a computational fluid dynamics (CFD) technique. The CFD simulations are carried out with three geometries, one plane vessel and the other two with ribs of square and triangle shape. The results are obtained in terms of velocity, volume fraction distribution, and bed expansion. The effect of other parameters, such as coefficient of restitution, initial bed height, and particle diameter, is also examined. When the particle diameter is large, airflow in an upward direction increases the solid bed height but the flow is almost steady. In the case of small-sized particles, the velocity field and volume fraction profiles for both phases vary with time. In certain regions within the bed, the air becomes concentrated and takes the form of a bubble. The results also show that in fluidized bed units, the unsteady behavior is usually enhanced when ribs are used. The comparison in terms of root mean square values indicates that velocity variation is ~50% more when triangular ribs are used The overall results show that placement of triangle-shaped ribs can be favorable for enhancing momentum and related processes/phenomena in the fluidized bed devices.