Mercury co-beneficial capture in air pollution control devices of coal-fired power plants

Abstract

Coal contains trace amount of mercury (Hg). Hg compounds in coal combustion flue gas are speciated into elemental (Hgo), oxidized (Hg2+), and particle-bound (Hgp). Air pollution control devices (APCDs) installed for removing NOx, particulate matter and SOx have a co-beneficial effect on Hg capture. In this paper Hg emission and speciation across APCDs in coal-fired power plants in S. Korea were measured; total emission and the co-beneficial control in existing APCDs were estimated for the year 2013. Hg concentration in flue gas at the outlet of the boiler and stack ranged from 7.5 to 9.9μg/Sm3 and 1.0 to 1.2μg/Sm3, respectively. APCDs (selective catalytic reactor (SCR)+electrostatic precipitator (ESP)+wet flue gas desulphurization (FGD)) were able to capture 80.8% of Hg as a co-beneficial control. SCR, ESP, and wet FGD independently and in a group promoted co-beneficial Hg control. Annually, 7.2t of Hg was captured as a co-beneficial control in existing APCDs of coal-fired power plants in South Korea. Even though, Hg co-beneficial controls in plants with advanced APCDs are significant, emphasis should be given for the direct control of Hg.