燃煤烟气中Hg迁移转化特性研究

Hg Formation and Transformation Characteristics in Flue Gas of Coal-fired Boiler

研究了300 MW煤粉锅炉系统选择性催化还原(selective catalytic reduction,SCR)、低低温电除尘器、海水脱硫、湿式电除尘器等超低排放设施在不同工况、不同煤种情况下的Hg迁移特性和脱除能力。结果表明:各工况下总汞排放浓度为1.16~2.90μg/m^3。最终排入大气中的汞主要以单质汞存在,还有少量氧化态汞,颗粒态汞被全部脱除;汞主要是在海水法烟气脱硫中被去除的,低低温电除尘器、海水脱硫、湿式电除尘器对总汞平均脱除率分别为25%、62%、37%;Hg^2+占比是影响烟气中汞脱除效率的关键,气相中较高的Hg^2+份额有利于在电除尘器和海水脱硫装置中获得较高的脱除效率;在该配备SCR脱硝、低低温电除尘器、海水脱硫、湿式电除尘器等超低排放设施的300 MW煤粉锅炉电厂中,总汞平均脱除率约为83%,能够实现较大程度的汞脱除。

The transfer characteristics and removal capability of Hg in ultra-low emission facilities such as selective catalytic reduction(SCR),low temperature electrostatic precipitator,seawater desulfurization and wet electrostatic precipitator in a 300 MW coal-fired boiler of a power plant were studied under different working conditions and different types of coal.The results show that under different working conditions,the total emission concentration of mercury is basically 1.16–2.90μg/m^3.The final release of mercury into the atmosphere is mainly composed of elemental mercury and a small amount of oxidized mercury,the particulate mercury was completely removed.Most mercury is removed in seawater flue gas desulfurization.The overall removal efficiency of mercury of low temperature electric precipitator,a seawater flue gas desulfurization scrubber and wet electric precipitator is 25%,62%and 37%respectively on average.The proportion of Hg^2+is the key to affect the efficiency of mercury removal in flue gas,and the higher proportion of Hg^2+in flue gas is beneficial to obtain higher efficiency in electrostatic precipitators and seawater flue gas desulfurization devices.In the 300 MW coal-fired boiler of a power plant equipped with a selective catalytic reduction unit,a low temperature electrostatic precipitator,a seawater flue gas desulfurization scrubber,and a wet electrostatic precipitator and other ultra-low emission facilities,the average removal rate of total mercury is about 83%,which can achieve greater levels of mercury removal.