Effect of flue gas purification facilities of coal-fired power plant on mercury emission

Abstract

The types and concentration of mercury in flue gas of nine coal-fired units were measured by OH method and the mercury content in desulfuration wastewater, slag, fly ash and gypsum were also measured. The influences of conventional pollutant removal facilities such as SCR denitration facility, dust removal facility, and wet flue gas desulfurization facilities on mercury type and concentration were studied. The results indicate that mercury emission type is mostly gaseous mercury and mercury emission in nine units all meets the standard requirement. SCR denitrification facilities have a great effect on mercury type, promoting oxidation of elemental mercury into oxidized mercury which is easily removed by downstream dust removal facilities and wet desulfurization facilities. Particulate mercury is synergistically removed in dust removal facilities, with mercury removal ratio between 13.5% and 80.6% which depends on particulate mercury proportion. The oxidized mercury is synergistically removed in wet desulfurization facilities, with mercury removal ratio between 9.0% and 72.9%. Mercury is transferred from coal to fly ash and desulfuration gypsum, and mercury stability in the solid by-products needs to be studied.

Keywords

• Coal-fired flue gas
• Pollutant purification facilities
• Mercury
• Emission characteristics