Effect of solution pH on SO_2, NO_X, and Hg removal from simulated coal combustion flue gas in an oxidant-enhanced wet scrubber

摘要

This paper presents a study on the simultaneous removal of SO_2, NO_x and Hg (both Hg~0 and Hg~(2+))from a simulated flue gas by oxidant injection in a bench-simulated wet limestone scrubber for a wide range of slurry pH. The slurry pH strongly influenced the chemical mechanism in the scrubber and, therefore, affected pollutant removal. This paper also examines the potential ClO_(2(gas)) reemission from a developed multipollutant scrubber at different slurry pHs. To better understand the chemical mechanisms at each slurry pH and to apply a mass balance to the process, detailed product ion analyses were performed for all experiments. Ion analysis covered three different chlorine species (chlorite, chloride, chlorate), sulfate, nitrite and nitrate.Different NO_x removal efficiencies and mechanisms were found in acidic and alkaline pHs in the multipollutant scrubber. The acidic solution was favorable for NO and Hg~0 oxidation, but increasing the slurry pH above 7.0 was disadvantageous for NO and Hg oxidation/removal. However, the rate of NO_x absorption (by percentage) was higher for the alkaline solution.