【作者】 王春杰；

【导师】 刘清雅； 刘振宇；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2015， 硕士

【摘要】 氮氧化物(NOx,硝)被公认为主要的大气污染物之一,其中燃煤排放的NOx占其排放总量的60%左右。以钒钛为催化剂的NH3选择性催化还原(SCR)脱硝技术,成熟高效,广泛用于燃煤烟气中NOx的减排。由于该类催化剂在运行过程中通常布置在高温高尘区,因此,不可避免会遭遇飞灰中的各类物质(包括碱金属、碱土金属和重金属等)而导致中毒失活。解析中毒机制不仅可以指导催化剂的改进,而且可以指导运行操作。纵观文献,不仅有关碱土金属中毒的研究较少,而且研究多数不考虑烟气中SO2、CO2和水汽的影响。鉴于此,本文以MgCl2和CaO为碱土金属代表,系统考察了C02和水汽存在时催化剂的碱土金属中毒机制。此外,针对我国燃煤锅炉粉尘量大,板式催化剂更适于高灰烟气脱硝的特点,本文探索了板式钒钛基脱硝催化剂的制备,以期兼顾活性和强度,降低中毒几率,延长催化剂寿命。主要得出以下结论：1.催化剂中的CaCl2量越多,中毒程度越深。SO2总体上缓解催化剂的CaCl2中毒：烟气中的SO2在有水条件下被气氛中O2氧化生成SO42-,尽管SO42-与CaCl2反应生成CaSO4而造成催化剂部分堵孔,但由于SO2增强了催化剂的表面酸性,进而增加NH3吸附而提高脱硝活性。2.C02对催化剂的CaCl2中毒没有影响,却可以减弱MgCl2中毒。对于MgCl2中毒的催化剂,CO2的存在大大增加了其活性氧比率,使得反应前大量的V3+氧化为V4+和V5+,并且能够把之前与V3+相互作用的Ti02释放出来,从而使得催化剂的脱硝活性增加。对于任何气氛条件下,CaCl2对催化剂的毒化作用要比MgCl2强。催化剂的毒化程度与碱土金属的碱性有关,碱性越强,则对催化剂的毒害程度越大。3.相同Ca/V比的条件下,CaCl2对催化剂的中毒作用比CaO大。二者均能导致催化剂表面B酸性位减弱以及V氧化能力的下降,但CaCl2对催化剂的这种作用更大,其中的Cl-能够与催化剂表面分散相V相互作用导致V不易被还原,从而催化剂活性丧失。对于催化剂的CaCl2中毒,浸渍法对催化剂的毒害作用比气溶胶法强。4.泥料水含量对催化剂的强度影响很大,但并非随水含量的增加催化剂的强度减弱,水含量在32.72%为宜；随着玻纤长度从0.038 mm增加到3 mm,催化剂的强度逐渐增强。但催化剂脱硝活性却相差不大；钛粉粒度为10 nm时,催化剂的强度最好,且活性也优于其它两种催化剂。更多还原

【Abstract】 Nitrogen oxide (NOX, Nitre) is one of the main atmospheric pollutants recognized around the world, and The NOX account of coal-fired emissions is around 60%.Flue gas denitration technology of NH3 selective catalytic reduction (SCR) is the most effective way to removal NOX in flue gas by now. Catalysts in operation process are decorated in high temperature region, they will inevitably encounter substances (including alkali, alkaline earth metals and heavy metals) in the fly ash and cause poisoning deactivation. Parsing poisoning mechanism can not only guide the improvement of catalyst, and can guide the operation. In literatures, not only studies of alkali earth metals poisoning is less, and most studies don’t consider the influences of SO2, CO2 in flue gas and water vapor. Therefore, this article made CaCl2, MgCl2 and CaO as representatives of alkaline earth metals, studied influences of SO2, CO2 on alkaline earth metals poisoning of the catalyst. In addition, because of the large amount of coal-fired boiler dust in China, plate type catalyst is more suitable for the characteristics of high ash, this paper studied the plate vanadium titanium base denitration catalyst preparation. So it can give attention to both activity and strength, which can limit your chances of poisoning, extend the life of the catalyst. The main conclusions are shown as follows:1. With the increasing of CaCl2 loadings, the degree of its poisoning to catalyst is greater. SO2 can alleviate the poisoning of alkaline earth metal to catalyst:it can be oxidated to SO42- under the condition of water by O2 in the atmosphere, although SO42- can react with Ca2+ to generate CaSO4 causing the catalyst blocking, but it increases surface acidity of catalyst to adsorb more NH3 which is of advantage to the SCR reaction.2. CO2 has no effect on CaCl2 poisoning of catalyst, but can weaken MgCl2 poisoning. For poisoning of MgCl2 to catalyst, CO2 can significantly increase the ratio of reactive oxygen, making V3+ oxidated into V4+ and V5+, and can release TiO2 interacting with V3+, thus making the denitration catalyst activity increased. For any atmosphere conditions, the poisoning of CaCl2 to catalyst is stronger than MgCl2.The stronger basicity of alkaline earth metal is, the greater the degree of catalyst poisoning is.3. Under the condition of the same Ca/V ratio, CaCl2 on catalyst poisoning effect is stronger than CaO. Both can lead to decline B acid sites and the oxidation ability of V, but CaCl2 catalyst is stronger, Cl- can interact with dispersed phase Ⅴ on catalyst surface, leading to loss of catalyst activity. For poisoning of CaCl2 to catalyst, the toxicity of impregnation method of is stronger than method of aerosol.4. Water content of sludge has a great influence on the strength of the catalyst,32.72% is advisable to water content; with glass fiber length increasing from 0.038 mm to 3 mm, the strength of the catalyst increases. But for denitration activity, the four are almost same; For 10 nm of titanium powder particle size, the strength of the catalyst is best, and also the denitration activity is better than the other two.更多还原