【作者】 罗辉；

【导师】 赵士林；

【作者基本信息】 中南大学 ， 工程热物理， 2023， 硕士

【摘要】 燃煤电厂排放的烟气汞约占全球人为汞排放量的26%,因其会对人类健康和环境造成巨大危害引起广泛关注。吸附剂喷射技术（ACI）是目前最为成熟、具有工程化应用前景的脱汞技术。针对传统吸附剂改性方法复杂、吸附剂脱汞能力差、脱汞产物存在二次释放风险等不足,本文提出机械化学硫改性木屑焦烟气脱汞实验研究。主要内容和结论如下:（1）在未添加任何改性剂的前提下,探讨热解工况对木屑焦的Hg⁰脱除效率的影响。以最高Hg⁰脱除效率为指标,通过N₂等温吸附/脱附（BET）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、傅里叶红外光谱（FTIR）及汞程序升温分解（Hg-TPD）对木屑焦表面物理化学特性的分析,讨论了各因素对吸附剂脱汞特性和理化特性的影响规律,结果表明,热解气氛N₂+7%O₂、热解终温800℃及升温速率10℃/min下制备的木屑焦Hg⁰脱除效率最高,为34.89%。同热解工况中,热解终温和热解气氛对于样品Hg⁰脱除特性的影响较大,而升温速率对于样品的影响不明显。（2）在前期研究工作的基础上选用S₂Cl₂为改性剂、采用机械化学方式进行硫改性木屑焦脱汞特性的实验研究,采用BET、SEM、XPS、FTIR及Hg-TPD探讨机械化学硫改性木屑焦改性及脱汞机制。结果表明,机械化学法S₂Cl₂改性显著提高R-BC的Hg⁰脱除效率,S₂Cl₂添加量为800μL,球磨参数为球料比10:1,采用大尺寸（直径=20mm）的氧化锆球磨珠条件下制备的吸附剂Hg⁰脱除效率最高,为97.12%。改性后的吸附剂对Hg⁰吸附主要以化学吸附为主,其表面的O-H、C=O、C=S等官能团和噻吩/单质硫及亚砜为Hg⁰吸附的活性位点。脱汞产物中主要以Hg S（black）形式存在。（3）在模拟烟气固定床Hg⁰脱除实验装置上,基于Hg⁰脱除量、Hg⁰脱除效率、Hg⁰吸附量、Hg²⁺逃逸量和Hg²⁺逃逸率,研究烟气成分（O₂、CO₂、SO₂和NO）对吸附剂的Hg⁰脱除特性的影响机制。研究结果表明,O₂对Hg⁰脱除影响不大,而CO₂对Hg⁰脱除有促进作用。较低的SO₂浓度（400～800 ppm）对吸附剂的Hg⁰脱除特性影响不大,但高浓度的SO₂（1200 ppm）明显促进了Hg⁰吸附量和Hg²⁺逃逸量,但对Hg²⁺逃逸率影响不大。当提高NO的浓度时,吸附剂的Hg²⁺逃逸量越来越高,Hg⁰吸附量越来越低,从而导致Hg²⁺逃逸率越来越高。SO₂和NO分别促进了Hg SO₄和Hg（NO₃）₂的产生。为了真正意义脱除燃煤电厂烟气中的Hg⁰,在保证高效汞捕捉的同时,应更关注吸附剂的孔隙结构。图26幅,表7个,参考文献136篇更多还原

【Abstract】 Mercury emitted from coal-fired power plants flue gas accounts for approximately 26%of global anthropogenic mercury emissions amount,which have attracted widespread attention because its the significant risks they pose to human health and the environment.Adopting the adsorbent injection（ACI）technology is currently the most mature and promising engineering-ready technology for mercury removal.To deal with the shortcomings of complex modification methods,poor mercury removal ability,and a risk of mercury secondary release of the traditional adsorbent,this work proposes an experimental study on the mercury removal from coal-fire flue gas by mechanochemical sulfur modified sawdust coke.The main contents and conclusions are as follows:（1）The effect of pyrolysis conditions on the Hg⁰ removal efficiency of sawdust coke was investigated without adding any modifiers.Taking the highest Hg⁰ removal efficiency as the index,the physical and chemical characteristics of sawdust coke were analyzed by N₂ isothermal adsorption/desorption（BET）,Scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）,Fourier transform infrared spectroscopy（FTIR）and Hg⁰ programmed temperature decomposition（Hg-TPD）.The effects of each factor on the Hg⁰ removal characteristics and physical and chemical characteristics of sawdust coke were studied.The results showed that the Hg⁰removal efficiency of sawdust coke prepared under pyrolysis atmosphere N₂+7%O₂,final pyrolysis temperature of 800℃and heating rate of 10℃/min was the highest,which was 34.89%.In the same pyrolysis condition,the effect of final pyrolysis temperature and pyrolysis atmosphere on the Hg⁰removal characteristics was greater,while the effect of heating rate was not obvious.（2）On the basis of the previous research work,S₂Cl₂ was used as modifier to prepare mechanochemical sulfur modified sawdust coke.The BET,SEM,XPS,FTIR and Hg-TPD were used to investigate the modification and Hg⁰removal mechanism of mechanochemical sulfur modified sawdust coke.The results showed that the Hg⁰ removal efficiency of raw sawdust coke was significantly improved by mechanochemical sulfur modification.When the addition of S₂Cl₂ of 800μL,the ball milling parameter of 10:1 and zirconium oxide ball milling beads with large size（diameter=20 mm）were used,Hg⁰removal efficiency reached the highest value（97.12%）.The Hg⁰ adsorption by modified adsorbent was mainly chemical adsorption,and O-H,C=O,C=S and thiophene/elemental sulfur and sulfoxide were the main active sites of Hg⁰ adsorption.Hg⁰ was predominantly present as Hg S（black）on adsorbents after mercury removal.（3）The influence mechanism of flue gas composition（O₂,CO₂,SO₂and NO）on the Hg⁰ removal by the adsorbent was investigated on a simulated flue gas fixed bed Hg⁰ removal experimental device,which was mainly based on Hg⁰ removal amount,Hg⁰ removal efficiency,Hg⁰adsorption amount,Hg²⁺escape amount and Hg²⁺escape ratio.The results showed that O₂ had little effect on Hg⁰ removal,while CO₂ promoted Hg⁰removal.Low-concentration SO₂（400～800 ppm）had little effect on the Hg⁰ removal,but high-concentration SO₂（1200 ppm）significantly promoted the Hg⁰ adsorption amount and Hg²⁺escape amount with little effect on the Hg²⁺escape ratio.When increasing the NO concentration,the Hg²⁺escaping amount from the adsorbent increased,and the Hg⁰adsorption amount decreased,which led to the increasing escape ratio of Hg²⁺.SO₂ and NO promoted the production of Hg SO₄ and Hg（NO₃）₂,respectively.In order to remove Hg⁰ from flue gas of coal-fired power plant,more attention should be paid to the pore structure of adsorbent while ensuring efficient mercury capture.更多还原