ESP飞灰对燃煤锅炉烟气汞的吸附特性

Adsorption characterization of coal fired flue gas mercury by ESP fly ashes

用氮气(N2)等温吸附(77K)测量了一座600MW煤粉锅炉电厂静电除尘器(ESP)各个电场飞灰的比表面积、孔径、孔比表面积、孔容积和孔分布,采用扫描电镜(SEM)和X射线能谱分析仪(EDX)分析了飞灰颗粒表面结构和化学组分.结果表明,颗粒粒径越小,比表面积越大,飞灰的汞吸附趋于增加.飞灰含碳量与汞含量呈正相关关系,亚微米级颗粒物对汞的吸附不仅与其比表面积有关,而且与其比表面积的利用率有关.静电除尘过程中飞灰的孔隙结构在不断地变化和发展,孔分布越宽越有利于对汞的吸附,微孔越发达且可利用率越高,越有利于汞的被吸附.

Fly ash samples were collected from the hopper of each electric field of an electrostatic precipitator （ESP） of a 600 MW pulverized coal boiler. The particle specific area, pore size, pore specific surface area, pore volume and pore distribution of the ash samples were measured via nitrogen adsorption at 77 K. The morphologies and chemical compositions of ash samples were analyzed by scanning electron microscope （SEM） and energy dispersive X-ray （EDX） detector respectively. The results show that the smaller the particle diameter, the bigger the specific surface areas and thus the more mercury adsorbed by fly ash. There is a positive correlation between carbon content and mercury content. The mercury adsorption on the micron fines is related not only to its specific surface area, but also to its surface utilization rate. The pore structures of fly ashes in different ESP electric fields are diversified. Wider pore distribution is beneficial to mercury adsorption. Developed pores with high surface utilization rate can adsorb more mercury.