Reduction of mercury emissions from combustion processes using electrostatic precipitators

Abstract

The article presents the results of laboratory and industrial tests on the reduction of mercury emission from coal combustion in power boilers. In laboratory conditions, the influence of the quantity of unburned carbon (UBC) in fly ash on the collection efficiency has been studied. The obtained results confirm that the higher content of unburned carbon in fly ash improves its ability to accumulate Hg and promotes the reduction of mercury emission downstream of the electrostatic precipitator by capture of particulate-bound mercury - Hg(p). In industrial tests, the possibility to add selected additives to oxidize the metallic mercury has been studied. The key feature of this solution is the oxidation of metallic mercury by injecting dedicated oxidizing additives into the flue gas duct upstream the electrostatic precipitator (ESP), and using fly ash as an adsorbent for mercury compounds. The use of the proposed solutions can contribute to the reduction of mercury emission. In some cases, it can ensure compliance with regulatory requirements of mercury concentrations in the flue gas without the need to build expensive mercury control installations.