Mercury Speciation Transformation During Coal Combustion - Mercury Emission and its Control in Chinese Coal-Fired Power Plants - page 29

100

80

60

H g 2+

Hg 0

40

20

0

700 800 900 1000 1100 1200

Temperature ( ) C

Fig. 4.2 Temperature influence on mercury speciation during coal burning

Fig. 4.3 shows the distribution of Hg (g) and Hg p in flue gas when both Xinwen
(XW) and CG pulverized coals were used as combustion as the layer condition in
the quartz tube. The Hg p speciation was about 20% of the total flue gas Hg. The
remaining Hg was all Hg (g) , and there was a little Hg in the ash. In the actual pul-
verized coal combustion flue gas, the Hg concentration in fly ash ranged between
23%26% of the total Hg. The Hg (g) directly discharged into the atmosphere was in
the range of 56%69%. Future studies on mercury emissions during coal combus-
tion should focus on the mercury speciation transformation law in the flue gas. At
the same time, flue gas Hg control research should focus on the Hg direct discharge
in the flue gas to the atmosphere.

90

80

70

60

XW gas e ous merc ur y
C G gaseous m ercury
CG part i culate mer c ury
XW par t iculate me r cury

50

40

30

20

10

700 800 900 1000 1100 1200

Temperature ( O C

Fig. 4.3 Distribution of gaseous and Hg p in burning coal sample

Typically, the Hg speciation distribution in flue gas of coal combustion is dif-
ferent from that of coal pyrolysis. As shown in Fig. 4.4 and Fig. 4.5, the Hg 0 con-
centration was less during coal combustion. As the combustion temperature in-
creased, the Hg 0 concentration quickly decreased.