(458e) Novel Economical Hg(0) Oxidation Reagent for Mercury Emissions Control from Coal-Fired Boilers

The authors have developed a novel economical additive for elemental mercury (Hg⁰) removal from coal-fired boilers. The oxidation reagent was rigorously tested in a lab-scale fixed-bed column with the Norit America's FGD activated carbon (DOE's benchmark sorbent) in a typical PRB subbituminous/lignite simulated flue gas (500 ppmv SO₂, 200 ppmv NO, 10 ppbv Hg⁰, 7% H₂O, 3% O₂, 12% CO₂ balanced with N₂) at 140 °C for sorbent injection. The test results showed excellent performance on Hg⁰ removal by the mixture of the additive and the activated carbon. Fixed-bed results also showed that a very small amount (~10%) of activated carbon injection could eliminate almost all of the mercury generated by reaction(s) of Hg⁰ with the additive, indicating promising use in subbituminous/lignite flue gases with relatively high Hg⁰ content.

A preliminary cost estimate for sorbent injection was almost 70~80% less than that of raw FGD activated carbon at subbituminous and lignite-firing sites. The additive is thermally stable up to 350 °C, suggesting potential high-temperature applications for coal gasification and hot-side electrostatic precipitator. As an alternative, the oxidized mercury generated from reaction(s) with the additive could be removed in wet scrubbers due to its high solubility in water. Therefore, the additive can be applied to virtually all coal-fired power plants where Hg⁰ emissions are relatively high such as PRB subbituminous and/or lignite coal-firing sites as an economical and viable option.