燃煤飞灰的物化性质及其吸附汞影响因素的试验研究

EXPERIMENTAL STUDY ON PHYSICOCHEMICAL CHARACTERISTICS AND INFLUENCING FACTORS OF MERCURY ADSORPTION BY FLY ASH FROM COAL COMBUSTION

采用X射线荧光光谱仪、扫描电子显微镜、粒度分析仪等分析了燃煤飞灰的物化性质。利用汞渗透管产生汞蒸气，将其与N2、O2、CO2组成的基本气体混合，在小型固定床试验台上进行了燃煤飞灰吸附气态汞影响因素的试验研究。研究结果表明：随着入口汞浓度的增大，飞灰对汞的吸附率先降低，再升高（仍低于汞入口浓度较低时），然后会再次降低；汞入口浓度增加，飞灰对汞的绝对吸附量随之增加，但吸附率不一定增加；在40～120℃范围内，飞灰对汞的吸附主要是物理吸附，飞灰对汞的吸附效率随着温度的上升而下降；试验所用飞灰在其粒径介于50μm和74μm之间时，可达到最佳的汞吸附效果。

The physicochemical characteristics of fly ash from coal combustion were analyzed by X - ray fluorescence （XRF）, scanning electron microscopy （SEM） and particle distribution analyzer, etc. The influencing factors of vapor mercury adsorption by the fly ash were conducted by using a bench - scale fixed - bed apparatus. A simulated flue gas was prepared by mixing heated, nitrogen gas streams con- taining mercury vapors （by an elemental mercury diffusion tube） and basic compositions of flue gas. Experiments indicated that with the inlet mercury concentration continuously increasing, the adsorp- tion efficiency of mercury by fly ash firstly decreased, and to certain extent increased, but it still was lower than that of the lower mercury concentration and it may dropped again with increasing to some extent. With the inlet mercury concentration gradually improving, the relative adsorption capacity of mercury by fly ash was thereupon becoming lager and lager , but the adsorption efficiency of mercury was not always increasing. The mercury adsorption of fly ash was primarily physical adsorption in the range of 40~120℃ ,and the adsorption efficiency of mercury decreased with the temperature increas- ing. When the particle diameter was between 50 μm and 74μm,the optimum effect of mercury adsorp- tion was possibly realized.