Environmental Engineering Reference
In-Depth Information
Transformation in Flue Gas
1) Reaction order
Based on the kinetic model established in this section, the simulated flue gas in
the experiment was close to that of the actual gas. It was because the oxidation of
mercury in flue gas was mainly the reaction of Hg
0
with chlorine-containing sub-
stances, but also was affected by the other components. In the experiment, the HCl
concentration and reaction temperatures were changed. Mercury reaction kinetic
experiments in the simulated flue gas were conducted under experimental condi-
tions as shown in Table 4.7.
Table 4.7
The simulated flue gas in the kinetic experiments
Name
Composition
O
2
7%
CO
2
13%
SO
2
1200 ppm
NO
800 ppm
HCl
20, 40, 60, 80, and 100 ppm
6.478 g/m
3
Hg
N
2
Equilibrium gas
T
373, 573, 773, 973, and 1173 K
Mercury concentrations were measured for different flue gas components, in-
cluding the HCl concentration, reaction temperature and residence time. Based on
the experimental results, the reaction rates were obtained for different situations.
Then, according to Eq. (4-22), a straight line could be drawn from the logarithm of
the reaction rate to that of the mercury concentration.
could be obtained from the
slope, and
k
1
could be obtained from the linear intercept. The reaction rate constant
at a given HCl concentration and reaction temperature, as well as the simulation
results of the reaction order, are shown in Figs. 4.17 to 4.41, respectively.
-1.4
-0.4
-1.6
-0.8
-1.8
-1.2
-2.0
-1.6
-2.2
-2.0
-2.4
1.0
1.2
1.4
1.6
1.8
1.4
1.5
1.6
1.7
1.8
ln
C
Hg
ln
C
Hg
Fig. 4.18
and
K
1
when
C
HCl
=20 ppm and
T
=573 K (
=1.876;
K
1
=0.0258;
r
2
=0.961)
Fig. 4.17
and
K
1
when
C
HCl
=20 ppm and
T
=373 K (
=1.762;
K
1
=0.00765;
r
2
=0.931)
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