The Mercury and Air Toxics Standard (MATS) published by EPA December 16, 2011, established limits on mercury emission for electricity generating units (EGUs) burning fossil fuels to less than 1.2 lb/TBtu depending on fuel. EGUs that currently employ wet flue gas desulfurizers (WFGDs) to reduce sulfur emissions expect significant mercury capture co-benefit from this device. However, laboratory and field tests show that oxidized mercury can be reduced to water-insoluble elemental mercury within the WFGD. This problem, termed mercury re-emission, leads to an increase in total stack mercury emissions. This paper summarizes two case studies of patented mercury re-emission control technology. The demonstrations involved 500 MWe EGUs burning subbituminous and bituminous coals. At baseline the percent mercury re-emission ranged from 20 to 100%. A low capital, simple, noninvasive, and patented technology reduced mercury re-emission to near zero.
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