【作者】 解宏端；

【导师】 孙冰；

【作者基本信息】 大连海事大学 ， 环境科学， 2009， 博士

【摘要】 随着现代工业的发展,温室气体排放与日俱增。在众多温室气体中,全氟化碳（PFCs）因其具有低毒、化学性质稳定等特点,被广泛应用于工业生产。PFCs在大气中具有较长的存在年限和强烈的红外吸收能力,PFCs直接排放到大气中将引起强烈的温室效应。微波等离子体处理PFCs气体具有去除率高,没有二次污染等优点,是二十世纪九十年代发展起来的新工艺。本研究设计了一套微波等离子体反应器,在大气压下激发并维持稳定的等离子体。利用发射光谱对常压下（大气压）微波等离子体特性进行了诊断。采用微波等离子体对CF₄这种最难分解的PFCs气体进行分解,考察了载气种类、微波功率、气体流量、初始浓度、添加气体等因素对去除率的影响。对CF₄分解的产物进行了分析。采用自由基诊断实验及热分解实验论证了CF₄在大气压微波等离子体中的分解过程和机理。开发了催化剂与微波等离子体协同分解CF₄的新方法。研究结果表明,大气压微波等离子体具有较高的电子温度和电子密度,其中含有多种活性粒子和自由基。CF₄气体的最高分解率可达99%以上,分解率随微波功率的提高而增加,随气体流速的增加而减小。适量的添加气（如O₂、H₂O）可以提高PFCs的分解效率,但过多的添加气体消耗等离子体中的高能电子,导致去除率下降。当O₂和H₂O在最适宜添加量时,CF₄去除率最高可提高17%和10%左右。在有氧气等添加气存在的条件下,CF₄完全分解时的最终产物主要为CO₂和F₂。CF₄在微波等离子体中分解机理是首先通过高能电子碰撞逐次失去一个F原子生成CF,基团,随后O自由基与CF_i基团发生链式反应生成CO₂和F₂等最终产物,而热分解不是CF₄分解的主要途径。添加催化剂与微波等离子体协同分解CF₄时,去除率可以提高10%左右,紫外线,高温和等离子体自身都可以激发催化剂催化分解CF₄。更多还原

【Abstract】 With the development of modem industry,the more and more greenhouse gases are released to the atmosphere.In all of greenhouse gases,perfluorocompounds（PFCs） have low toxic and stable chemical characters,and are widely used in industrial processes.Because of their strong infrared absorption and long atmospheric lifetimes, PFCs emission will cause the globe warming effect.Atmospheric microwave plasma, which is the new technology on decomposing PFCs from 1990,has relative high destruction and removal efficiencies and no secondary pollution in PFCs treatment.In this study,the microwave plasma device is designed to excite and maintain stable plasma on atmospheric press.The characters of plasma are diagnosed by emission optical spectroscopy.Microwave plasma is employed to decompose the CF4,which is the most difficult to be decomposed.The experiment has been done with a varity of conditions including carrier gases,microwave power,gas flow rate,initial concentration,additive gases.The products of CF4 decomposition are analysed.The process and mechanism of PFCs decomposition is certified by radicals’ diagnosis and thermodynamic experiment.The combined catalysts and microwave plasma is developed to decompose PFCs.The results indicate that the atmospheric microwave plasma has relative high electron temperature and high electron density.There are kinds of actived radicals in plasma.The highest DRE of CF4 is up to 99%.The DRE is increased with the increase of microwave power,and is decreased with the increase of gas flow rate.Optimum volume of additive gases can promote the DRE,while the excessive additive gases will exhaust the electron and result in the decrease of DRE. The optimum volume of O₂ and H₂O can enhance the DRE about 20%and 10%, respectively.With O₂ exist,CO₂ and F₂ is the main products of CF₄ decomposition.The mechanism of CF₄ decomposition is that the CF₄ molecular lost one F atom each time to form CF_i by the electron collision firstly,and the O radicals was the assistance in the later reaction,to further transform CF_i to CO₂ and F₂.The thermal decomposition is not the main process in CF₄ decomposition.The DRE of CF₄ is enhanced about 10%by catalysts used,the ultraviolet radiation,high temperature and plasma all can actived the catalysts to decompose CF₄.更多还原