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suspension and fluidized-bed combustion; the research of the reaction kinetic model
on mercury speciation transformation in flue gas; the equilibrium thermochemical
analysis of mercury speciation transformation after coal combustion; and modeling
research on mercury speciation transformation during coal combustion.
4.2 Mercury Emissions from Coal of Different Combustion
Types
The mercury emission characteristics of pulverized coal using three general com-
bustion methods (i.e., grate-firing, suspension, and fluidized-bed combustion me-
thods) were studied using a quartz tube furnace, a small-scale pulverized coal fur-
nace, and a medium-scale circulating fluidized-bed test. The speciation distribution
of flue gas mercury was analyzed using the OH method.
4.2.1 Mercury Speciation during Coal Pyrolyzing and Burning in
a Fixed Bed
Distribution of mercury speciation during coal pyrolysis and coal burning was
researched. In the experiment, Changguang (CG) coal was chosen to analyse the
mercury speciation distribution at different temperatures of 700, 900 and 1,200 °C
during coal pyrolysis and burning, respectively.
As shown in Fig. 4.1, the Hg 0 concentration in the flue gas was reduced to 77%
from 95% when the thermal pyrolysis temperature of coal increased from 700 to
1,200 °C. When coal burning, the Hg 0 concentration in the flue gas was reduced to
45% from 83% with the temperature increasing from 700 to 1,200 °C (Fig. 4.2). Hg 0
was the main speciation in both the above conditions. However, the Hg 0 concen-
tration in pyrolyzing was higher than that in burning.
100
80
60
H g 2+
H g 0
40
20
0
700
800
900
1000
1100
1200
Temperature ( )
C
Fig. 4.1 Temperature influence on mercury speciation during coal pyrolyzing
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