【作者】 郭东旭；

【导师】 路春美；

【作者基本信息】 山东大学 ， 热能工程， 2013， 硕士

【摘要】 氮氧化物严峻的排放形势及其对我国可持续发展造成的巨大压力,使得氨选择性催化还原(NH3-SCR)技术成为我国火电脱硝领域的重要选择。SCR技术的核心是催化剂,低温SCR技术相对于现有SCR技术能耗及运行成本更低,因此低温SCR催化剂的研发正成为当前的热点。本课题组前期研究表明铁铈催化剂具有相对较高的中低温SCR活性,但活性温度还不能满足低温脱硝的要求,本文在保证Ti摩尔总量不变的前提下,通过向铁铈催化剂中引入另一种Ti化合物,来探讨改善其低温脱硝特性的途径,并对该新型铁铈钛催化剂进行脱硝性能及反应动力学研究。Ti与Fe元素序号相近,当Ti添加到铁铈催化剂中时,会对Fe原子核外电子云产生诱导,在此过程中发生的物理化学变化会使催化剂的内部结构及表面化学特性发生改变,从而影响催化剂的SCR性能。本文通过对Ti添加量不同的催化剂进行SCR活性实验,探讨改善其低温脱硝特性的途径并确定Ti的最佳添加量；通过对该催化剂进行孔隙结构(BET)、表面元素价态及浓度分布(XPS)、X射线晶格衍射(XRD)、程序升温脱附(TPD)等表征结构测试,发现Ti添加使催化剂的孔径更小从而比表面积和比孔容更大,活性组分以无定形态高度分散在催化剂表面,且催化剂表面的氧浓度更大,低温区间内NH3吸附量更多,这些都能促进低温SCR反应的进行。在此基础上,本文系统考察了煅烧温度、反应温度、O2浓度、氨氮比(NH3/NO)(?)口空速比(GHSV)对新型铁铈钛催化剂SCR脱硝活性的影响规律,发现：煅烧温度为400℃制备的催化剂SCR活性最高,煅烧温度过高会导致活性组分结晶、分散度降低；反应温度为175℃时,催化剂脱硝效率即可达到90%,低温活性优良,在200-400℃区间内,脱硝效率保持在95%以上；02在SCR反应中至关重要,反应气氛中没有02时,催化剂脱硝效率极低,通入少量02,脱硝效率即迅速升高,02浓度超过3%后,脱硝效率达到最大并保持不变；氨氮比为1、空速比为30,000h-‘时,催化剂的脱硝效率最高。此外,本文还对该新型铁铈钛催化剂进行了反应动力学特性实验研究,在分析NH3浓度、NO浓度、O2浓度对SCR反应速率影响的基础上,得到SCR反应中,NH3为零级反应,NO为一级反应,当O2浓度大于3%时,其为零级反应,而O2浓度小于3%时,其反应级数为0.39。同时计算得到催化剂的反应活化能Ea=28.6KJ·mol-1(目前商用钒钛催化剂活化能一般为70～90KJ·mol-1铁基催化剂活化能一般为50～70KJ·mol-1)、反应速率常数k=23248.4exp[-28559.1/(RgT)]。更多还原

【Abstract】 The austere situation of NOx emissions is a huge pressure to sustainable development of our country, So NH3-SCR technology is very important to De-NOx field of coal-fired power plants in our country. The key to SCR technology is catalyst, compared to existing technology, low temperature SCR technology costs less power and money, so researching and developing low temperature SCR catalyst is a focus. Existing iron-cerium catalyst has high SCR activity at meddle-low temperature, but the activity temperature can not meet the requirements of low temperature SCR technology, so this paper dops another kind of titanium in it to explore a way to improve its low temperature SCR activity on the condition that titanium dosage is constant, and researches its De-NOx performance and reaction kinetics.Since the atomic number of titanium is near that of iron, titanium doping can induce the extranuclear electron of iron, so it can change the physical-chemical nature in the process to influence SCR performance of catalyst. The SCR activity tests of catalysts with different titanium loading amount are carried out to explore a way to improve its low temperature SCR activity and obtain the optimum loading amount of titanium; From the test results of BET, XPS, XRD, TPD, we find that cerium doping makes a larger specific surface area and pore volume but smaller bore diameter, active components in amorphous state highly disperse on the catalyst surface, the oxygen concentration and NH3adsorbance are higher at low temperature, all of which can promote SCR reaction.On this basis, this paper investigates the effects of calcined temperature, reaction temperature, oxygen concentration, NH3/NO and GHSV on the SCR De-NO, performance of iron-cerium-titanium catalyst systematically, we find that:the catalyst calcined at400℃has the best SCR activity, higher calcined temperature can lead to the crystallization of active components and parts of anatase TiO2change into rutile TiO2; the denitration efficiency can reach90%at175℃, indicating that low temperature activity is good, and the denitration efficiency is higher than95%between200℃and400℃; the denitration efficiency is very low without O2in the feeding gas, and when bubbling little amount of O2while the denitration efficiency rises rapidly, the denitration efficiency stays the same when oxygen concentration is over3%,indicating that O2is very important in SCR reaction; the denitration efficiency is highest when NH3/NO is1and GHSV is30000h-1.Furthermore, this paper studies the reaction kinetics of this novel iron-cerium-titanium catalyst considering the effects of NH3, NO and O2concentration on the reaction rate. We find that in the SCR reaction, the reaction order of NH3is0, the reaction order of NO is1, the reaction order of O2is0when the oxygen concentration is over3%While it becomes0.39when the oxygen concentration is less than3%. The reaction activation energy is28.6KJ·mol-1(while the activation energy of commercial catalyst is70～90KJ·mol-1and the iron-based catalyst is50～70KJ·mol-1) and the reaction rate constant is23248.4exp [-28559.1/(RgT)], after knowing the effects of NH3, NO and O2concentration to reaction rate.更多还原