Environmental Engineering Reference
In-Depth Information
1.02
1
0.98
0.96
0.94
0.92
Y = -9.67252 × 10
-5
t+1
R
2
= 9.98484 × 10
-1
0.9
0.88
0
200
400
600
800
1000
1200
1400
t
(s)
FIGURE 10.6
Plot of (1 −
X
)
1/3
versus time for the TGA char + CO
2
reaction of
Example 10.2.
c. The plot is given in Figure 10.6.
The requested maximum initial reaction rate per unit volume is
R
X
=
k
0
1
c
X
,
g
a
s
,
0
=
3
ρ
Y
1
−
ε
ð Þ
τ
MW
Y
ν
Y
τ
follows from Figure 10.6, from the slope of the straight line:
τ
= 1/9,67252 × 10
−5
s; substituting the other properties, with
ν
Y
=1, it
s
−1
.
d. A check on lack of external mass transfer limitation can be made via the fol-
lowing criterion:
follows that
R
X
= 1.55 × 10
−2
kmol
m
−3
d
p
6
k
g
c
X
π
6
k
g
=
−
R
X
π
k
1
d
p
d
p
1
The nominator is the first-order reaction rate, and the denominator represents
maximum mass transfer (with maximal driving force between bulk concen-
tration and surface concentration).
Substitution of the parameter values in the aforementioned equation leads
to the quantity on the left-hand side of the equation to be 9.5 × 10
−3
, which is
much smaller than 1. This is OK.
e. A check on the lack of internal mass transfer limitation can be made by rea-
lizing that the mole flow of CO
2
(X) to the char particle (Y) must be equal to
the inner particle transport (mole flow,
Φ
A
) and that the relative difference
Search WWH ::
Custom Search