Study On Characterization Of Atmospheric Mercury Emissions From A Coal-fired Power Plant In Beijing And Emission Factor

Atmosphere mercury has been identified as a persistent pollutant with characteristics of high toxicity, long-distance transmission, bioaccumulation and mutagenicity to human health and environment. In recent years, with the rapid development of Chinese economy, a large number of atmospheric mercury emissions by firing coal have seriously polluted the atmospheric environment. To conduct researches on emission characteristics is of great significance to make effective mercury abatement policies.This study adopted approach of on-site tests. Based on research of literatures, choose Ontario Method (OHM) and EPA method30B that EPA recommended to test atmospheric Hg emissions of coal-fired power plant, and collected and tested the samples of coal, ash, slag and other solid. The fate of mercury on coal combustion, the emission trend and the mercury removal efficiency of air pollution control devices (APCD) were analyzed. According to the experimental results, atmospheric mercury emission factors of coal-fired power plants in Beijing were established, and calculated atmospheric Hg emissions of Beijing. The main research results are as follows:(1)Mercury levels in fly ash are much higher than levels in coal and slag, about their7times and170times respectively. After coal burning in high temperature, the merchury lose in the slag, enrich in the fly ash. Mercury contents in the desulfurization gypsum are around100times of the limestone. The power of atmospheric mercury emission concentration is1.2μg/m3, and emission intensity is1.15μg/Kwh.(2)By material balance,96.81%Hg that come into gas come from coal, followed by limestone and desulfurization process water, respectively are2.47%,0.72%; the main destination of mercury is:the desulfurization gypsums take away54.27%, dust catcher bottom ashes take away39.86%,5.68%with flue gas are released into the atmosphere, the proportion that take by boiler slag and desulfurization wastewater are respectively6.1×10-3%and0.19%. The atmospheric mercury removal efficiencies of APCD of electrostatic precipitator (ESP), wet flue gas desulfurization (WFGD) are22.7%,29.4%, respectively. The toal mercury removal efficiencies of APCD combinations of selective catalytic reduction (SCR)+ESP+WFGD is73.55%.(3) Based on the measured results, obtain the atmospheric mercury emission factors of coal-fired power plants in Beijing, which are respectively0.1822mg/kg with no APCD,0.0612mg/kg with ESP,0.0612mg/kg with ESP+WFGD,0.0241mg/kg with FF+WFGD, and0.0414mg/kg with SCR+ESP+WFGD. The total mercury emissions from coal-fired power plants in Beijing in2010was4.93kg, the APCD reduced mercury emission8.37kg.