May 28, 2002

S.B. Reddy Karri,  T.M. Knowlton in “Circulating Fluidized Bed Technology VII” (J.R. Grace, J-X. Zhu, H. de Lasa, eds.) Canadian Society of Chemical Engineering, Ottawa (2002) p. 310.

A circulating fluidized bed regime diagram mapping the regions where Geldart Group A solids in the annulus flow upward or downward was constructed.  This information was obtained in a 200-mm-diameter riser, 14.3 m long, operating with FCC catalyst with an average particle size (dp50) of 67 microns.  Air was the conveying gas.  The direction of solids flow at the wall was determined using extraction probes to map the radial distribution of solids mass flux.  It was also determined visually by viewing solids flow in Plexiglas riser inserts at two different points in the riser.  Gas velocities were varied from 2 to 15 m/sec, and solids mass fluxes were varied from 20 to 400 kg/m2-sec.  It was found that the transition from downward to upward solids flow at the wall was more sensitive to increasing gas velocity than by increasing solids mass flux.