Mercury emission characteristics and control in coal-fired power plants: field evaluation of APCDs and enhanced Hg0 removal by Cu-Fe co-impregnated magnetospheres

This study investigated the mercury emission and control characteristics of different coal-fired power plants (315 MW and 640 MW). The effects of conventional air pollution control devices (APCDs) on mercury speciation and removal were systematically analyzed by measuring mercury content in raw coal, flue gas, fly ash, bottom ash, gypsum, and desulfurization wastewater. To achieve near-zero mercury emissions, magnetospheres (MF) co-impregnated with copper chloride and ferric chloride were employed to replace commercial activated carbon (AC), and their elemental mercury (Hg 0 ) removal performance was evaluated. The results showed that mercury was mainly present in flue gas and fly ash, accounting for 44.6–61.3% and 24.8–47.0% of the total mercury (Hg T ). The existing APCDs achieved Hg T removal efficiencies of 64.3–68.8% for the 315 MW plant and 33.5–42.9% for the 640 MW plant. Particulate mercury (Hg p ) was almost completely removed by the dust collectors, while the synergistic effect of dust removal and wet desulfurization systems removed 62.6–96.7% of Hg 2+ and 13.4–53.7% of Hg 0 . Furthermore, adsorption experiments and characterization analyses revealed that, under the effect of the Cu and Fe dual active sites, the modified MF achieved an Hg 0 removal efficiency of up to 95% under simulated flue gas conditions, with a saturated adsorption capacity over 10 times that of AC. Finally, the feasibility analysis indicated that the modified MF not only exhibits excellent magnetic recovery performance, but also has a raw material cost only about 1/200 that of AC, demonstrating significant industrial application potential and economic benefits.