When research into the measurement and control of Hg emissions from coal-fired power plants began in earnest in the early 1990s, it was observed that oxidized mercury can be scrubbed at high efficiency in wet FGD systems, while elemental mercury can not. In many cases, elemental mercury concentrations were observed to increase slightly across wet FGD systems, but this was typically regarded as within the variability of the measurement methods. However, later measurements have shown substantial re-emissions from some FGD systems.

The goal of this project is to develop a fundamental understanding of the aqueous chemistry of mercury (Hg) absorbed by wet flue gas desulfurization (FGD) scrubbing liquors.  Specifically, the project will determine the chemical reactions that oxidized mercury undergoes once absorbed, the byproducts of those reactions, and reaction kinetics. 

The project will develop an empirically adjusted, theoretically based reaction kinetics model to predict the chemical reactions of Hg species in FGD liquors. It is expected that the development of this model will allow FGD systems to be optimized to maximize Hg capture and prevent or reduce Hg re-emissions, either through modification of FGD conditions or through the use of additives, and to avoid high liquid-phase Hg concentrations in FGD blow-down liquors.