This paper describes a lab-scale simulating scrubber that was designed and built in the laboratory at Western Kentucky University's 'institute for Combustion Science and Environmental Technology. A series of tests on the slurry of CaO, CaSO_3, CaSG_4 and Na_2SO_3 were carried out to simulate recirculating slurry in different oxidation modes. Elemental mercury (Hg~0) re-emission was replicated through the simulating scrubber. The relationships of oxidation-reduction potential (ORP) of the slurries and Hg~0 re-emissions were evaluated. The results indicated that the higher the operational temperature of the scrubber and pH value of the slurry, the higher the Hg~0 concentrations emitted from the simulating scrubber. The Hg~0 re-emission rates decreased with the increase of O_2 concentration in the carrier gas. In addition, effects of additives on suppressing Hg~0 re-emission are evaluated in this paper. Sodium Tetrasulfide, TMT 15, NaHS and HI were added to the slurry, respectively; and Hg~(2+) absorbed in the slurry was retained in the slurry as mercury precipitates. Therefore, there was a significant capacity of additives to suppress Hg~0.
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