Characteristics of Mercury Emissions from Coal-fired Power Plants in Chongqing

Abstract

Four typical coal-fired power plants in Chongqing, representing two different boiler types (circulating fluidized bed boiler and pulverized coal boiler), were chosen to investigate mercury emission characteristics through a mercury mass balance method by analyzing mercury contents in all input and output raw materials in order to accurately estimate mercury emissions. The results showed coal with mercury concentrations ranging (80.77±6.39)-(266.83±4.71) μg·kg-1 could be a significant contributor of input mercury in these four studied power plants. Most mercury output from these power plants entered into solid waste with high proportion of mercury entering the fly ash in CFB plants and entering the fly ash and desulfurization gypsum in PC plants. Mercury removal efficiencies of studied plants were in the range of 72.89%-96.05%, and these efficiencies in CFB plants were higher than those in PC plants. The mercury emission factors for EFelectricity and EFcoal of these four plants were 4.66-29.47 μg·(kW·h)-1 and 8.55-71.77 mg·t-1, respectively. The mercury emission was also calculated to be 6.13-429.17 g·d-1. Mercury emissions from coal-fired power plants were associated with the content of mercury in coal, boiler type, generation load, pollution control equipment, and so on. To control the mercury emissions, more attention should be paid to improving the generation load, increasing the mercury removal efficiency of flue gas cleaning equipment, and strengthening the supervision of solid waste re-utilization.