Mercury Release from Coal Combustion By-Products (CCBS) in Guangzhou Pearl River Power Plant

Mercury is one of the most toxic metal elements, which has been paid more and more attention nowadays because of its volatility, persistence and bioaccumulation. It can be found as a trace pollutant in coal combustion by-products (CCBs) when gaseous mercury captured by them during coal combustion. In this paper, we will study mercury enrichment and transfer in the CCBs and significantly discuss their influencing factors, including the CCBs particle grades, ambient acidity and calcination temperature. The conclusions were drawn that mercury was enriched to a certain degree in the fly ash with the particle grades below 250 μm and the flue gas desulfurization (FGD) residue. When the particle grades of the fly ash were larger than 250 μm, the mercury enrichment factor fell to 0.596 rapidly. Only 10.69-17.85% of the total mercury occurred to transfer from the CCBs at the pH=1-7 with acid leaching solution on average. When calcination temperature increased progressively from 200 to 400°C, the mercury emission from the CCBs increased remarkably. When calcination temperature was higher than 400°C, about three fourth of the total mercury in the CCBs was emitted into atmosphere, and then almost maintained these emission amounts from 400 to 1000°C for 1 hour calcination. The total mercury content in the CCBs could meet the control standards of mercury pollutants in sludge for agriculture (GB8173-87) enacted by China.