Mercury Speciation Transformation During Coal Combustion - Mercury Emission and its Control in Chinese Coal-Fired Power Plants - page 37

70

Case 1: no limestone
Case 2: adding limestone 60

50

40

30

20

10

0

Bottom ash Fly ash Flue gas

Fig. 4.13 Ratio of Hg in different ashes in No. 1 and No. 2 conditions

80

70 Case 1: no limestone

Case 2: adding limestone

60

50

40

30

20

10

0

Bottom ash Fly ash Flue gas

Fig. 4.14 Ratio of Hg in different ashes in No. 3 and No. 4 conditions

4.2.4 Mercury Emission in Different Combustion Types

By heating coal in a fixed quartz tube furnace, the behavior of mercury emission
was checked. In the pulverized coal boiler and circulating fluidized-bed bench tests,
the transformation of mercury speciation from coal in the two combustion types of
suspension combustion and fluidized-bed combustion were also studied.

4.2.4.1 Ratio of Hg(g) and Hg p in Flue Gas

The ratios of Hg (g) and Hg p in flue gas with three combustion methods are shown in
Figs. 4.15 and 4.16. The data in the figures were treated as the average values based
on all experimental conditions. From the experimental results of coal burning in a
fixed bed and a state of suspension, the ratios of Hg (g) and Hg p were found to be
similar. The proportion of Hg (g) was about 80% of total mercury in the fluidized-bed