V. Štěpánek1,2, J. Loskot1, M. Smolík1, L. Hyšplerová1, J. Kříž1
1) Faculty of Science, University of Hradec Králové, CZ; 2) Coal power plant Chvaletice, CZ
REDUCTION OF PARTICULATE MATTER AND MERCURY EMISSIONS FROM COAL POWER PLANTS, COMPARATIVE EMISSION MODELING IN CZ-PL REFERENCE POINTS
Tightening of standards for air protection leads to the development of new and significantly more effective technologies for removing particulate matter and SOx from flue gas which originates from large solid fuel combustion. Recently, it has been found that combinations of these environmental technologies can also lead to the reduction of mercury emissions from coal power plants. During coal combustion at temperatures in the range of about 700-800 °C, a thermal decomposition of mercury compounds occurs, which leads to the formation of gaseous elemental mercury (Hg0). This elemental mercury subsequently flows out of the combustion chamber together with the flue gas stream. Most of this mercury condenses or is captured on the phase interface of fly ash particles. In a heat exchanger for steam production, the flue gas is cooled down to 200-250 °C which results in an oxidation in the form of Hg2+(HgCl2), Hg+(Hg2Cl2) and Hg0. The HgCl2 form is captured by the wet flue gas desulphurisation process, but the Hg0 form passes through the adsorber. Now the greatest attention is paid especially to the coal power plants which use a new modern system for flue gas dedusting, so-called fabric filters. This system has a higher particle separation efficiency, which also applies to the mercury particles. In our work, the experimental values of mercury emissions measured at two coal plants equipped with different flue gas dedusting technologies were used for a comparative emission modeling using a dispersion model SYMOS´97 (updated 2014). The model calculations were done for nine reference points located in the Czech-Polish border region. Both the measurement and modeling results show that the mercury concentrations in the Czech-Polish border region are now significantly lower than in the past and the health risk associated with mercury contamination is small and still decreasing.
Keywords: coal power plants, particulate matter and mercury emissions, dispersion modeling