TITLE:
Mercury Speciation of Flue Gas Desulphurization By-Products in Coal-Fired Power Plants in China
AUTHORS:
Gang Tian, Hongyan Long, Yu Liu, Chen Zhang, Fan Zhang, Hongchang Wang, Jinwei Zhu, Yanping Zhang, Hongmei Wang, Fan Wang
KEYWORDS:
Mercury, Mercury Speciation, Flue Gas, Desulphurization, By-Product, Sequential Chemical Extractions, Morphology and Distribution, Gypsum
JOURNAL NAME:
Journal of Power and Energy Engineering,
Vol.8 No.11,
November
26,
2020
ABSTRACT: The aim of this study was to develop and examine the morphology and
distribution of mercury (Hg) in flue gas desulfurization (FGD) by-product. Mercury
in the coal of coal-fired power plants is concentrated in the by-products of
desulfurization process, and it is widely used as an additive in cement,
building materials and other industries. Due to the different stability of
various forms of mercury in the environment, subsequent use of products
containing desulfurization by-product additives will continue to be released
into the environment, endangering human health. Therefore, it is very necessary
to study the form and distribution of mercury in the by-products of
desulfurization in coal-fired power plants to provide a theoretical basis for
subsequent harmless treatment. For
content and morphology of mercury analysis, 1 sample of dry FGD ash and 6
samples of wet FGD gypsum were analyzed. The total 7 samples were extracted
using a modification of sequential chemical extractions (SCE) method, which was
employed for the partitioning Hg into four fractions: water soluble, acid
soluble, H2O2 soluble, and
residual. The Hg analysis was done with United States Environmental Protection
Agency (USEPA) method 7471B. Comparing with the wet FGD gypsums of coal-fired boilers, the
total Hg content in the dry FGD by-product was as high as 1.22
mg/kg, while the total Hg content in the FGD gypsum is 0.23 - 0.74
mg/kg, which was 2 times over the wet FGD gypsum. The concentration of water
soluble Hg in the dry FGD by-product was the highest amount (0.72 mg/kg), accounting
for 59.02% of the total mercury. While residual Hg content was 0.16 mg/kg, only
about 13.11% of the total mercury. Mercury content in FGD gypsum was expressed
in the form of ρ (residual Hg) > ρ (H2O2 soluble Hg) > ρ (water soluble Hg) > ρ (acid soluble Hg). The morphology and distribution of mercury in FGD
by-products is supposed to be analyzed before utilization, and the impact of
mercury on the environment should be considered.