| The flue gas mercury emission caused by coal combustion in coal-fired power plants has always been the main source of anthropogenic mercury in China,as a heavy metal,mercury will accumulate in the human body for a long time,causing permanent damage to the human body.As a country with large anthropogenic mercury emissions,coal-fired power generation will continue to be China’s primary power generation method for a long time.In recent years,with the transformation of ultra-low emission technology of coal-fired power plants in China,researching the impact of ultra-low emission transformation on the emissions of mercury in the flue gas of coal-fired power plants,and exploring the emission characteristics of mercury in the flue gas of coal-fired power plants under ultra-low emissions are of great significance to China and the word in terms of emission reduction of flue gas mercury.This study selects 15 ultra-low emission coal-fired power plants in Henan,Hebei,Shandong,Tianjin and Hainan.The mercury concentration in flue gas was measured using the EPA standard method for the determination of metal emissions from stationary sources(EPA method 29).At the same time,the concentration of some important heavy metals(As,Cr,Mn,Ni,Pb,Se)in flue gas was monitored simultaneously.In addition,coal samples were collected simultaneously to test the mercury content in coal.The emission characteristics of flue gas mercury were studied,the synergistic removal effect of flue gas treatment facilities on flue gas mercury was investigated,and the emission factors of flue gas mercury from coal-fired power plants in China were determined.Using a mercury emission estimation model to estimate mercury emissions in flue gas from coal-fired power plants in China.The results showed that the mercury contents in coal samples from 15 coal-fired units were in the range of 0.018～0.400 mg/kg,and the average release rate of mercury in coal is 98.82%.The mercury production concentration was in the range of 2.69～47.13μg/m~3.The mercury contents in coal were positively correlated with the production concentration.Flue gas mercury emission concentration was between 0.001～4.30μg/m~3,which is far lower than the emission limit of 30μg/m~3 specified in China’s"Emission Standard of Air Pollutants for Thermal Power Plants"(GB13223-2011),it has reached the mercury emission standards of coal-fired power plants in developed countries and regions such as Canada,the European Union,Japan,and the United States.The combined mercury removal efficiency of the flue gas treatment facilities of the 15 coal-fired units was between 80.67%and 99.98%.Among the power plants selected for comparison,the mercury removal efficiency of SCR+EF/ESP+WFGD+WESP is between92.46%and 98.41%,and the mercury removal efficiency of SCR+EF/ESP+WFGD is between80.67%and 91.77%.The average removal efficiency of 15 coal-fired units for 6 heavy metals under ultra-low emission is between 96.94%and 99.97%,and the synergistic removal effect is remarkable,and the average emission concentration of 6 heavy metals has reached the emission standard limit of US coal-fired power plants.Based on the measured results of 15 coal-fired units and research results from relevant literature,the average mercury content in Chinese coal is calculated to be 0.191 mg/kg,and the coordinated mercury removal efficiency of flue gas treatment facilities in coal-fired power plants with ultra-low emissions was 86.72%,and that of flue gas treatment facilities in non-ultra-low emission coal-fired power plants was 74.42%.Through the established mercury emission factor model,the mercury emission factors of flue gas from coal-fired power plants in China in 2018,2019,2020,2025,and 2030 were calculated to be 0.0297,0.0283,0.0279,0.0262,and 0.0245 g/t respectively,this shows that the mercury emission factor can be effectively reduced by implementing ultra-low emission retrofits of coal-fired power plants.By establishing a mercury emission estimation model,the mercury emissions in flue gas of coal-fired power plants in 2018,2019 and 2020 were calculated to be 58.12,56.43 and 58.06 t,respectively.By predicting the GDP growth rate,electricity consumption elasticity coefficient,the proportion of coal-fired power and coal consumption for power generation in 2025 and 2030,it is calculated that the flue gas mercury emission of China’s coal-fired power plants in 2025under the existing policy will be between 54.08 and 58.01 t,and the flue gas mercury emissions under the enhanced policy are between 51.90 and 55.99 t.In 2030,the flue gas mercury emissions of China’s coal-fired power plants under the existing policy will be between 45.79and 51.99 t,and the flue gas mercury emissions under the enhanced policy will be between39.35 and 45.35 t. |
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