Impacting Factors of Elemental Mercury Re-emission across a Lab-scale Simulated Scrubber

Elemental mercury (Hg0) re-emissions from slurries and solutions were evaluated in a lab-scale simulated scrubber. Oxidized mercury (Hg2+) standard solution was injected into the simulated scrubber at a desired rate to simulate absorbing and dissolving of Hg2+ in the flue gas across wet flue gas desulfurization (WFGD) systems. PS analytical mercury analyzer was used to continuously determine Hg0 re-emission concentrations in the carrier gas from the scrubber. Sulfite ion in the slurry of CaSO3 was validated to reduce Hg2+ to Hg0, while no Hg0 re-emission occurred from slurries of CaSO4 and CaO. Transitional metal ions with low chemical valence such as Fe2+, Pb2+, Ni2+, and Cu+ were used to prepare solutions with concentration levels of mmol·L−1. Reduction reaction of Hg2+ to Hg0 was observed from these solutions. Reduction capabilities for the different transitional metal ions in the solutions were: Pb2+>Cu+>Fe2+> AsO−2>Ni2+.