溴素改性ESP飞灰脱汞机理的实验研究  

Experimental Study of Mercury Removal Mechanism by Bromine-modified Fly Ash

作　　者：陈明明[1] 段钰锋[1] 李佳辰[1] 周强[1] 柳帅[1] 刘猛[1] 

机构地区：[1]能源热转换及其过程测控教育部重点实验室(东南大学),江苏省南京市210096

出　　处：《中国电机工程学报》2017年第11期3207-3215,共9页Proceedings of the CSEE

基　　金：国家自然科学基金项目(51376046);国家重点研发计划(2016YFC0201105;2016YFB0600604-02)~~

摘　　要：燃煤飞灰因含有残炭(UBC)及少量过渡金属元素而被认为是一种具有工业应用前景的价廉高效脱汞吸附剂。然而由于飞灰的成分、结构及性质复杂,在烟道中与汞的反应机理尚不统一清晰。文中在固定床上对4种燃煤电厂静电除尘器(ESP)飞灰(FA)及1%NH4Br改性后的ESP飞灰(NBFA)进行了汞吸附实验,分别考查了N2及模拟烟气气氛对吸附剂汞吸附的影响,利用X射线荧光光谱法(X-ray fluorescence spectrometry,XRF)、扫描电子显微镜(scanning electron microscope,SEM)对其汞吸附能力的影响因素进行了分析。利用程序升温脱附(temperature programmed desorption,TPD)探讨了改性飞灰对汞的吸附机理。结果表明溴化铵改性可显著增加NBFA的汞吸附性能,且在模拟烟气下汞吸附能力大大增强;烟气中酸性气体的存在能极大的促进Hg^0的氧化,其中75%的Hg^0被氧化,只有25%Hg^0被吸附在飞灰表面。溴素改性飞灰对Hg^0的作用机制主要遵循Langmuir-Hinshelwood和Eley-Rideal机理,而飞灰含有的无机组分对Hg^0的氧化作用遵循Mars-Masessen机理;在飞灰表面主要生成的是HgB r2和HgO,UBC含量高的飞灰表面还会生成HgS和Hg_2(NO_3)_2。根据实验结果,飞灰对汞吸附氧化主要以Langmuir-Hinshelwood和Eley-Rideal机理为主,伴随有微弱的Mars-Masessen机理。Fly ash from coal combustion has been recognized as an effective sorbents for mercury removal in flue gases. However, the mechanism between fly ash and mercury reaction is unclear due to the complicated composition of it, so the oxidation and adsorption on the surface of fly ashes are crucial to mercury control. In this study, the mercury adsorption and oxidation mechanisms on the surface of four bromine-modified electrostatic precipitator （ESP） fly ashes were explored based on the experimental results of a fixed-bed reactor and temperature programmed desorption （TPD） technique. The fly ashes were characterized by the X-ray fluorescence spectrometry （XRF）, Scanning electron microscope （SEM） to study the reaction mechanism. The results indicated that bromine-modified fly ashes played a significant role in mercury oxidation and adsorption compared with raw ones, about 75% elemental Hg transformed into oxidized Hg was achieved. The heterogeneous oxidation process has been confirmed that follows the Langmuir-Hinshelwood and Eley-Ridea mechanism, while the inorganic material in fly ashes oxidizing mercury follows the Mars-Masessen mechanism in the second.

关 键 词：燃煤电厂 溴素改性 飞灰 汞 程序升温脱附 

分 类 号：X511[环境科学与工程—环境工程]