Technology of mercury removal from exhaust from coal fired boilers

Abstract

For the Polish power industry, the basic fuel is hard coal and lignite, which contains significant amounts of mercury. Current emission standards in the European Union (IED directive and in the near future BAT conclusions) create conditions for investment in flue gas cleaning installations for coal-fired power plants. During the combustion of coal, mainly metallic mercury (Hg0) is produced, which is difficult to remove from the flue gas in dedusting installations (electrostatic precipitators and fabric filters) and wet flue gas desulphurization plants. In these installations, oxidized mercury (Hg2+) and ash bound mercury (Hg(p)) are removed. In order to reduce the mercury concentration in flue gases, the DEMERTEC technology was created, which is based on the oxidation of metallic mercury to an oxidized form and its removal from flue gas in an existing flue gas de-dusting or de-sulphurization installations. The article presents the results of field tests of the DEMERTEC technology for flue gas from hard coal and lignite. This technology was tested on a ~ 400 MWe unit fed with lignite and on an FGD absorber in which flue gas was purified from two units with a capacity of 195 and 220 MWe fed with hard coal. In both cases, mercury emissions were reduced below the levels required by the BAT conclusions.