PARTITIONING OF MERCURY AT COAL POWER PLANTS AND EFFORTS TO MANAGE MERCURY IN KOREA

摘要

Mercury in flue gas were sampled before and after each air pollution control device (APCD) in coal fired power plants, equipped with selective catalytic reduction (SCR), electrostatic precipitator (ESP) and flue gas desulphurization (FGD) in series. In average 1.71 μg/ Nm3 and 2.04 μg/ Nm3 of total mercury was emitted from stack of plant 1 and 2 respectively. The partition coefficients of mercury within APCDs show that in flue gas it was mainly distributed in gaseous (elemental + oxidized) form. Specifically, at stack, 0.87 fraction of mercury was distributed in gaseous phase and only 0.13 fractions in particle phase. Before SCR almost all (0.99 fraction) of mercury species were partitioned in gas phase. Significant reduction in gaseous to particulate mercury partitioning coefficient (KGP) was found as temperature across APCDs decreases. Our result shows the higher oxidation of elemental mercury across SCR in plant 1 (73.95%) compared to plant 2 (34.41%). APCDs installed for removing NOx, SOx, and PM can achieve the co-benefits for mercury removal and the present study shows in an average 71.35 % and 67.51 % of total mercury was removed within APCD of plant 1 and 2 respectively. Mercury distribution within bituminous coal power plants shows that 61 % of Hg was collected in ESP fly ash hopper, 21.1 % released into atmosphere, 8.7% remained in the gypsum and 1.3 % was collected in bottom ash. Presentation will also include some efforts of research and development to control mercury and to investigate the status and transportation of mercury fate around the nation.