Environmental Engineering Reference
In-Depth Information
and 324 method, respectively. Hg (g) was the main speciation, which was about
86.5%
97.8% of the total mercury emission. Hg p was only 2.1%
13.5% of the
total. It is difficult to control gaseous Hg 0 by existing conventional pollution control
devices because Hg 0 , as a primary Hg (g) , has special characteristics, including
higher volatility, a lower water-solubility and a stable speciation, which can induce
global pollution with the help of atmospheric motion. Hg 2+ is another type of Hg (g) .
Common Hg 2+ is water-soluble and can be captured by most wet flue gas cleaning
technologies. Once it is emitted to the atmosphere, water soluble Hg 2+ is deposited,
thus polluting the vicinity of the mercury emission source.
Table 2.6 shows the concentration of total Hg (g) and ratio of mercury speciation
in the flue gas emitted into the atmosphere. The ratio of Hg 0 and that of Hg 2+ was
nearly equal when only the ESP was in place; the ratio of Hg 2+ decreased when both
ESP and WFGD were in place; and the ratio of Hg 0 and the concentration of total
Hg (g) decreased further when SCR, ESP, and WFGD were in place (Tables 2.3 to
2.6). This occurred because the SCR catalyzed Hg 0 to Hg 2+ under a certain condi-
tion and then the WFGD captured most Hg 2+ .
Table 2.3 Concentration and speciation of flue gas mercury emissions into the atmosphere (OH
method)
Percentage of
total Hg (%)
Unit
capacity
(MW)
Pollutant
control
device
Hg 0
(g/(N·m 3 ))
Hg 2+
(g/(N·m 3 ))
Combustion
method
Hg p
(g/(N·m 3 ))
Total Hg
(g/(N·m 3 ))
Location
Hg 0
Hg 2+ Hg p
Zhejiang
300
Four-corner
ESP
4.8468
3.3678
1.2831
9.4976
51.0
35.5 13.5
Front and
back walls
Zhejiang
600
ESP
7.4813
6.0838
1.9357
15.5007
48.3
39.2 12.5
Jiangsu
300
Four-corner
ESP
5.6532
6.5371
0.8708
13.0612
43.4
49.3 7.3
SCR+ESP
+FGD
Fujian
300
Four-corner
0.4460
2.3660
0.0310
2.843
15.7
83.2 1.1
Table 2.4 Concentration and speciation of flue gas mercury (excluding Hg p ) emissions into the
atmosphere (CEM method)
Percentage of
total gaseous
Hg (%)
Unit
capacity
(MW)
Pollutant
control
device
Total
gaseous
(g/(N·m 3 ))
Hg 0
(g/(N·m 3 ))
Hg 2+
(g/(N·m 3 ))
Combustion
method
Location
Hg 0
Hg 2+
Jiangsu
300
Four-corner
ESP
8.79
6.86
13.0612
56.2
43.8
Beijing
2*100
Four-corner ESP+FGD
1.97
1.11
3.08
64.0
36.0
Anhui
300
Four-corner ESP+FGD
6
0.28
6.28
95.5
4.5
SCR+ESP
+FGD
Fujian
300
Four-corner
0
ˉ
ˉ
ˉ ˉ
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