Pilot Plant Testing of Elemental Mercury Reemission from a Wet Scrubber

Abstract

This paper is to discuss the recent observations of elemental mercury (Hg0) reemissions from a pilot-scale limestone wet scrubber. Simulated flue gas was generated by burning natural gas in a down-fired furnace and doped with 2000 ppm of sulfur dioxide (SO2). Mercuric chloride (HgCl2) solution was delivered to the scrubber at a controlled rate to simulate the absorption of ionized mercury (Hg2+). Testing results have shown that, after Hg2+ was injected, elevated Hg0 concentrations were soon detected both in the scrubber effluent flue gas and the hold tank air, which reflected the occurrence of Hg0 reemissions in both places. When the HgCl2 feed was stopped, the Hg0 reemission continued for more than 2 h. In addition, a significant Hg0 reemission was also detected outside the scrubber loop. In an attempt to understand the Hg0 reemission increase across the wet scrubber system under transient and steady states and to understand the underlying relationship with the mercury complexes retained in the wet scrub...