220MW燃煤机组飞灰对汞的吸附特性研究

A Study of the Mercury Adsorption Characteristics of Flyash in a 220 MW Coal-fired Power Plant

用氮气(N2)等温吸附(77.35K)测量了一座220MW燃煤电站静电除尘器4个电场飞灰的比表面积、孔径、孔容积、孔分布和分形维数,采用扫描电镜(SEM)分析了飞灰颗粒表观形貌特征。结果表明,颗粒粒径减小,比表面积增大,飞灰的汞含量增高;飞灰碳含量与汞含量呈正相关关系;锅炉负荷越大,汞吸附越弱;存在一个合适的分形维数值使得飞灰对汞的物理吸附和化学吸附最为充分。孔分布越宽和孔容积有效利用率越大越有利于对汞的吸附,亚微米级颗粒物对汞的吸附能力取决于它的堆积形态和其比表面积的可利用率。

The specific surface area,pore diameter,pore volume,pore distribution and fractal dimension of flyash in four electric fields of an electrostatic precipitator(ESP)in a 220 MW coal-fired power plant were measured by use of nitrogen isothermal adsorption(at a constant temperature of 77.35 K).By employing a scanning electron microscope the visual morphological characteristics of flyash particles were analyzed.The results show that the smaller the particle diameter and the greater the specific surface area,the higher the mercury content in flyash.The carbon and mercury content in flyash exhibits a positive correlation.With an increase of load,the mercury adsorption tends to be weakened.There exists an optimum fractal dimension,at which the physical and chemical adsorption of mercury by flyash attains a maximum value.The broader the pore distribution and the greater the effective utilization rate of the pore volume,the more favorable condition for the adsorption of mercury.The adsorption capacity of mercury by a sub-micron level particle depends on its pileup morphology and the utilization rate of its specific surface area.