Abstract
The paper presents an analysis of measurement results on
cluster properties in a two-dimensional lab-scale cold
fluidized bed operating in turbulent and circulating
fluidized bed modes. Experiments were carried out with
Geldart B particles of (Sauter mean) diameters varying
from 0.256 mm to 0.440 mm. Different particle size
distributions and bed mass were used along with different
superficial gas velocities in the range of 2.75 m/s to
4.00 m/s. High-speed images of the bed were taken in a
controlled lighting environment. Analysis of the
experimental images was conducted to determine the
horizontal length scale distribution of the solid
clusters along the 3 m high CFB. Additionally, the solid
hold-up inside the clusters was evaluated. The effects of
particle size, bed mass and superficial gas velocity on
the measured cluster properties were determined. The
solid hold-up of the clusters was correlated to the
horizontal length scales of the clusters to estimate the
importance of each cluster size in terms of the mass
fraction of solids residing in clusters of a specific
width range. In the bottom region up to 0.2 m from the
air distributor, about 5% of the solid mass in clusters
was found to reside in structures with horizontal length
scales less than 1 cm while at 1.2 m height the
corresponding share was about 10%. This information is
relevant for determination of the mesh resolution
required to describe all the significant cluster sizes in
CFD simulations. The findings of the study on the width
distributions of the clusters and the solid
concentrations inside the clusters may also be used as a
point of comparison with corresponding measures observed
in simulations, by which a quantitative validation of CFD
results could be made.
Original language | English |
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Pages (from-to) | 420-436 |
Journal | Powder Technology |
Volume | 291 |
DOIs | |
Publication status | Published - 2016 |
MoE publication type | A1 Journal article-refereed |
Keywords
- circulating fluidized bed (CFB)
- cluster dimension
- length scale
- solid hold-up
- image analysis