CFD Modeling of Bubbling Fluidized Bed Combustor

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CFD Modeling of Bubbling Fluidized Bed
Combustor Michael M. Choi, Troy Robinson, Larry
Baxter Chemical Engineering Department, BYU,
Provo, UT February 2003
Accomplishments During the past few months, we
developed a 1D model of a fluidized bed (version
0.1). The model predicts fluidized bed height,
reactant concentration leaving the bed, and
bubble rise velocity based on the bubble
diameter, minimum fluidization velocity (in the
emulsion phase), air flow-rate from the bottom,
and the original bed height.
Objective Our objective is to develop a CFD model
of bubbling fluidized bed combustor. We are
using object-oriented programming with OpenGL and
Visual C.
What is a Fluidized Bed Combustor? A fluidized
bed is similar to a conventional boiler except
that fluidized bed suspend solid-fuels, sands,
and catalysts (dolomite, limestone) on upward
blowing jets of air. The fuels trapped in the
bed are burned. Significant reductions of SO2,
NOx, and combustion of lower quality fuels can be
achieved with fluidized bed boilers.
Stage of Fluidization
Pictures Different views of the model version
0.1 with different input data. The calculated
results are shown on the right.
Future works The current model is being modified
to predict pressure drop concentration
gradient min. fluidization velocity
temperature gradient Better graphical interface
and user interactive features are being added
currently. An unfinished model of fluidized bed
is shown on the right. A significant improvement
has been made in object-oriented programming.
The model has a zooming/rotating capability that
can be easily controlled with a mouse, plus
changing variables are made easier with a dialog
box. Theoretical pressure drop within the bed
has been calculated and will be compared with the
experimental data with the fluidized bed at BYU.
HYBEX - Bubbling fluidized bed boiler Kymin
Voima, Kuusankoski, Finland Fuels Bark, forest
residue, sludge, peat, gas, oil Steam 269
MWth, 107 kg/s 114 bar, 541 C Start-up 2002
CYMIC - Circulating fluidized bed
boiler Alholmens Kraft, Pietarsaari,
Finland Fuels Wood, peat, coal Steam 550
MWth,194/179 kg/s, 165/40 bar, 545/545 C
Start-up 2001
Acknowledgement Special thanks to Keijo
Salmenoja, AKER KVAERNER, who provided the
pictures above