Environmental Engineering Reference
In-Depth Information
Fig. 3 Energy output for various oxygen carrier feeds and air
fl
flow rates for 100 kg/h of coal feed
rate is increased above a certain threshold value, the marginal increase in energy
output becomes extremely small. The red line in Fig.
3
represents the baseline
experimental case (Fe
2
O
3
at 5,921 kg/h) for which the maximum energy output is
685.26 kW with around 900 kg/h air
flow rate. For the threshold Fe
2
O
3
rate of
7,000 kg/h, the maximum energy output of 824.33 kW occurs at around 1,000 kg/h
air
fl
flow rate. Thus, 138.97 kW of additional energy output is obtained by increasing
the oxygen carrier rate from 5,921 to 7,000 kg/h. Therefore, for maximum energy
output with a coal feeding rate of 100 kg/h, the optimum rates of air flow and
oxygen carrier feed are 1,000 and 7,000 kg/h, respectively. In other words, the
optimum ratio of coal, air, and oxygen carrier is 1:10:70 for maximum energy
output.
It should be noted that the above ratio of coal, air, and oxygen carrier feeds is
based on using Colombian coal. Compared to the baseline case corresponding to
the work of Sahir et al. (
2012
), a net increase in power of 48 % can be obtained by
increasing the air
fl
flow rate by 40.25 % and the OC feeding rate by 18.22 % to attain
this optimum ratio for the given coal feed. Other parameters that may also in
fl
uence
the energy output include the temperature and pressure of the reactors, types of
coal, particle size, etc., which are not investigated in this work.
fl
3 CLOU Process Simulation Using ASPEN Plus
When solid fuel such as coal is used in a CLC system, it is often the case that the
reactivity of char is low because of the limited contact of oxygen carrier and
gasi
ed coal. An alternative process known as the chemical looping with oxygen
uncoupling (CLOU) has been proposed to overcome the low reactivity of the char
gasi
cation stage in the CD-CLC (Leion et al.
2009b
; Mattisson et al.
2009a
,
b
;
é
Ryd
n et al.
2011
). CLOU is based on the strategy of using materials which release
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