Environmental Engineering Reference
In-Depth Information
performance of an experimental laboratory-scale iG-CLC apparatus. More impor-
tantly, the simulations are used to modify the design con
guration for enhanced
system performance. These simulations provide valuable insight in the various
physical processes critical to the ef
cient performance of the CLC process. Future
areas of promise in CD-CLC research are also discussed including issues related to
industrial-scale deployment and retro
tting in existing coal-
red power plants.
2 CLC Process Simulation Using ASPEN Plus
ASPEN Plus is a process simulation software that employs basic engineering rela-
tionships such as mass and energy balance, and multiphase and chemical reaction
models in modeling a process at system level. It consists of
fl
ow sheet simulations that
calculate stream
flow rates, compositions, properties, and operating conditions. It has
been demonstrated that ASPEN Plus can successfully model the CLC processes, and
the results of simulations are in excellent agreement with the observed data. ASPEN
Plus is employed tomodel the effect of different rates of coal feed, air
fl
ow, and oxygen
carrier feed in the CLC process. Based on the results of these simulations, a rela-
tionship between the energy output and the amount of coal, air
fl
fl
ow, and oxygen
carrier is derived and optimized for maximum energy output.
2.1 Validation of the CLC Process Simulation
with Experiment
The CLC process simulation in ASPEN Plus was validated against the experimental
work of Sahir et al. (
2012
). The physical and chemical properties of the Colombian
coal used as the solid fuel in the experiment are summarized in Table
1
.
The schematic of the
fl
flow sheet for this simulation is shown in Fig.
1
. The coal is
er
to be partially oxidized to form syngas. The oxygen carrier material used is a mixture
of 60 wt% Fe
2
O
3
and 40 wt% inert Al
2
O
3
as support. The molar ratio of steam and
carbon is maintained at unity for the process model. The syngas composition at the
gasi
first pulverized and dried before it is pressurized and introduced into a shell gasi
er outlet is 34.5 % CO, 50.3 % H
2
, 12.3 % H
2
O, and 2.4 % CO
2
. The syngas is
converted completely to CO
2
and H
2
O in the fuel reactor, while the Fe
2
O
3
in the
oxygen carrier is reduced to Fe
3
O
4
. The out
ow from the fuel reactor is a concen-
trated stream of H
2
O and CO
2
. After condensing the stream, high-purity CO
2
is
obtained. The reduced oxygen carrier is fed into the air reactor where the oxidation
reaction takes place with an 80 % conversion of Fe
3
O
4
to Fe
2
O
3
.
fl
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