Environmental Engineering Reference
In-Depth Information
4
Simultaneous Multi-Pollutants Removal with
Ozone and Wet Scrubber
4.1 Introduction
The discussion above shows that the conversion of NO is a key process in any
multi-pollutants control technique. The reaction kinetics of NO
x
and O
3
has been
mastered through our preliminary work. The main oxidation product of NO
through O
3
is NO
2
and NO
3
or N
2
O
5
can be generated only if excessive O
3
is
injected. The NO
2
generation turns out to be the initial step of an ozone oxidation
process integrated with WFGD system afterwards. It is no doubt that NO
x
with a
high valence, such as NO
2
, have a strong water solvency. However, the solubility
coefficient of NO
x
is rather different from that of SO
2
because of the oxidation
property of NO
x
. NO
x
vary the dissolution characteristic from SO
2
in several
aspects. For example, the NO
2
solubility coefficient of 0.012 mol/(L⋅atm) (25 °C)
[1]
is lower than that of SO
2
(1.4 mol/(L⋅atm)) (25 °C)
[2]
. The existence of reductive
substances (such as SO
3
2
and HSO
3
) in a solution can increase a little the NO
2
absorption rate because of the oxidation property of NO
2
and redox reaction
occurrence. Again, N
2
O
5
, which is the anhydride of nitric acid, can react quickly
with water to form nitric acid as the product. Therefore, the removal of NO
x
with a
high valence (particularly NO
2
) in a wet scrubber is investigated here, in addition
to the interactions of NO
x
with SO
2
and products generated. Given differences of
the gas-liquid mass transfer characteristics between NO
x
and SO
2
, the attention
necessitates to be focused on identifying whether a SO
2
-favored alkali solution is
appropriate to remove NO
x
.
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