Improving the Removal Efficiency of Elemental Mercury by Pre-Existing Aerosol Particles in Double Dielectric Barrier Discharge Treatments

ABSTRACT

Plasma technology has been employed for the removal of gaseous elemental mercury (Hg⁰) from simulated flue gases without pre-existing airborne particles. This study developed a double dielectric barrier discharge (DDBD) treatment system, in which two coaxial electrodes were covered by quartz dielectrics, for removing mercury with the presence of aerosol particles. The increase in pre-existing aerosol surface concentration can improve Hg⁰ removal efficiency up to 160% in the DDBD device. Inorganic aerosol particles (sodium chloride) perform better than organic ones (sucrose) in improving Hg⁰ removal efficiency. These aerosol particles can be collected in the DDBD system. For sodium chloride particles, a collection efficiency of more than 90% was observed in the tested diameter range of 10–100 nm. The improvement in Hg⁰ removal with the presence of particles is possibly due to that (i) aerosol particles provide additional surface for surface-induced Hg⁰ oxidations, (ii) reactive species (such as Cl) generated by plasma etching particle surface rapidly react with Hg⁰, and (iii) charged particles can in-flight adsorb mercury species.