Environmental Engineering Reference
In-Depth Information
gas environment. Generally, the free-radical based multi-pollutants removal
technology includes e-beam and pulsed-corona methods.
E-beam method
[86-92]
. The research on e-beam simultaneous desulfurization
and denitrification technologies began in the 20
th
century. In principle, all types of
active groups (including OH, OH
2
, O, and O
3
), generated by the high-energy
e-beam irradiation process of flue gas, can oxidize SO
2
and NO
x
to generate
H
2
SO
4
and HNO
3
, respectively. These acids react with the ejected NH
3
to form
NH
4
NO
3
and (NH
4
)
2
SO
4
. Ebara Company in Japan has developed a commercial
e-beam multi-pollutants removal technology, which uses a high-energy electron
excitation of N
2
, O
2
, and H
2
O molecules to generate N, O, O
3
, OH, and other
active radicals. With these free radicals assistance, NO and SO
2
can be oxidized to
a high state naturally (i.e., the common forms of NO
2
and SO
3
), which then react
with NH
3
to generate by-products spontaneously. Ebara has applied this
technology commercially in Chengdu and Hangzhou thermal power plants in
China.
Pulsed-corona method
[93,94]
. The pulsed-corona method uses the
pulsed-corona discharge to obtain active electrons. These active electrons are then
injected into flue gas to break down molecular bonds of various components, so as
to form a variety of active free radicals that used to remove SO
2
and NO
x
. Khacef
and Cormier
[95]
applied the pulsed-corona method to deal with SO
2
and NO
x
in
the flue gas of a glass processing plant. The Power Span Company adopts the
corona discharging low-temperature plasma to remove NO
x
, SO
2
, PM, Hg, HCl,
and other pollutants simultaneously, coupled with NH
3
absorption and wet
electrostatic precipitators
[96]
. However, NH
3
can volatile easily and tends to have
secondary pollution risk because of the NH
3
leakage.
1.3.2.4 Wet Chemical Multi-Pollutants Removal Technology
This type is characterized by the preparation of a solution coupled with special
reagents. The solution is sprayed into flue gas to remove SO
2
and NO
x
simultaneously. The drawbacks lie on a long time lasting for the gas component
absorption process, low removal efficiency, and the potential secondary pollution
because of the waste liquid discharge. Mainly divided by the added reagents, the
wet chemical multi-pollutants removal technology has several subcategories.
Sub-ferrous complex method
. Taking the sub-ferrous complex contained-SH
groups as the absorbent, Shi
et al
.
[97]
used the renewable sub-ferrous cysteine
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