(260g) Cluster Characteristics of Polydisperse Group B Particles In a CFB Riser

Cluster characteristics of Polydisperse
Group B particles in a CFB riser

Jia Wei Chew^a, Drew M. Parker^a,
Roy Hays^b, John G. Findlay^b, Ted M. Knowlton^b,
S.B. Reddy Karri^b, Ray A. Cocco^b, Christine M. Hrenya^a,*

^aDepartment of Chemical and Biological Engineering,
University of Colorado at Boulder, Boulder, CO 80309

^bParticulate Solid Research Incorporated, Chicago, IL 60632

The important role of clustering in
high-velocity, gas-solid flow has been well documented in experiments and
simulations alike, though previous efforts have focused on monodisperse
systems. In this work, experiments with a focus on understanding the impact of
polydispersity on clustering characteristics (appearance probability, duration
and frequency) of Geldart Group B particles in a circulating fluidized bed
(CFB) riser have been carried out. In a moderately dense CFB riser, three
mixtures were investigated: (i) a density-difference binary mixture, with
particles of different material density (ρ_s)
but same particle sizes (d_ave),
(ii) a size-difference binary mixture, with particles of different d_ave but same material
density ρ_s, and (iii)
a continuous particle size distribution (PSD). In addition, in a dilute CFB
riser, varying widths of continuous PSDs and varying compositions of binary
mixtures were investigated. A
fiber optic probe was used for detection of solids, and cluster identification
was accomplished via wavelet decomposition. Collectively, results
show that: (i) local riser
position has a significant influence on all three cluster characteristics in
all cases, while effects of operating condition and material type (i.e.,
material property or effect of polydispersity) are secondary, (ii) among the
three cluster characteristics, appearance
probability appears to be largely a function of riser position only, and is
insensitive to changes in operating condition or material type, and (iii)
cluster duration and frequency are influenced by operating condition and
material type, though only at some axial positions. The
results presented provide a comprehensive picture of factors affecting cluster
trends.

^*Corresponding author:
hrenya@colorado.edu