Mercury Speciation Transformation During Coal Combustion - Mercury Emission and its Control in Chinese Coal-Fired Power Plants - page 84

4.5.2.3 Correlation between Hg and Cl Distribution
Fig. 4.78 shows the Hg's form and concentration distribution on the section plane of
the furnace. Fig. 4.78(a) is Hg 0 distribution in the furnace, Fig. 4.78(b) is HgCl 2
distribution in the furnace, and Fig. 4.78(c) shows the HgO distribution in the fur-
nace. According to Fig. 4.78(a), the highest concentration of Hg 0 appeared at the
bottom of the main combustion area, just above the cold ash bucket. That might be
attributed to the fact that the heavy metal element Hg had large molecular weight
(200 g/mol), and easily sank by gravity. Relatively, the Hg 0 concentration was quite
low at the burner area, only because a lot of HgO and HgCl 2 was generated in this
area. Figs. 4.78(b) and (c) also showed this phenomenon. According to Figs.
4.78(b) and (c), HgCl and HgO were mainly generated at the burner area and the
outlet area of the burner chamber. Besides, there was a process happening by which
Hg 0 transforms to Hg 2+ because of the cooling process at the outlet area of the
burner chamber.
(a) Hg 0 distribution in furnace (b) HgCl 2 distribution in furnace
(c) HgO distribution in furnace
Fig. 4.78 Hg species distribution in furnace