Environmental Engineering Reference
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Hg
(g)
in flue gas decreased greatly; however, the Hg
p
concentrations in flue gas
increased by 22% and 18%, respectively.
70
Particulate mercury
Gaseous mercury
60
50
40
30
20
10
0
No.1
No.2
Fig. 4.11
Ratio of Hg
(g)
and Hg
p
in No. 1 and No. 2 conditions
80
Particulate mercury
Gaseous mercury
70
60
50
40
30
20
10
0
No.3
No.4
Fig. 4.12
Ratio of Hg
(g)
and Hg
p
in No. 3 and No. 4 conditions
The mercury concentrations per unit mass (μg/g) in coal, fly ash, and bottom ash
under different working conditions are presented in Table 4.3. Mercury concentra-
tions in coal were 0.2977 and 0.3911 μg/g, respectively, and those in fly ash ranged
within 0.2569 - 0.3315 μg/g. Meanwhile, the mercury concentration in the bottom
ash ranged within 0.0192 - 0.0362 μg/g. The concentration of mercury in the bot-
tom ash was much lower than that in coal because most of the mercury evaporated
into gas at the high combustion temperature. Mercury concentration in the fly ash
was much higher compared with the bottom ash, which was different from other
major metal trace elements. This difference can be attributed to the relatively lower
temperature environment of the tail flue gas. Mercury vapor condensed on, or was
adsorbed by, the surface, thus increasing mercury concentration in the fly ash. The
mercury concentration in the fly ash can potentially pollute water and soil.
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