Biomedical Engineering Reference
In-Depth Information
To chimney
Analytical balance
Manifold
5
ss tube
Flue gas
analyzer
Electric fumace
1
2
3
4
Pressure
transducer
SS porous
basket
O
2
N
2
SO
2
CO
2
FIGURE 13.5
Schematic of a QWM apparatus.
in the porous basket undergoes reaction, during which period the mass of the
sample is recorded continuously by an analytical balance, which is interfaced
with a computer. Gas temperatures are measured at various points by ther-
mocouples. Part of the gases escaping from the chamber is sent to a continu-
ous flue gas analyzer, which determines the percentages and composition of
the flue gas; the weight loss of the fuel is plotted as a function of time.
QWM helps to determine the reaction rate, reactivity, and study changes
in the physicochemical condition of the biomass or other samples. The fol-
lowing is an example of how reaction rate constant can be determined using
the QWM apparatus. Here we take the example of a calcination reaction to
illustrate its use.
Calcination reaction: CaCO
3
-
CO
2
.
We define rate constant, K (s
2
1
), in a first-order reaction of kinetic model
to examine the kinetics of calcination reaction.
CaO
1
K
ð
1
X
Þð
P
eq
2
P
CO
2
Þ
dX
dt
5
2
(13.1)
P
eq
Ea
RT
K
5
k
0
e
2
W
0
2
W
t
W
0
100
44
X
5
3
where X
conversion (
), P
eq
5
equilibrium decomposition pressure (atm),
5
2
(s
2
1
),
P
CO
2
5
partial pressure of CO
2
(atm), k
0
5
reaction rate constant
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