Effect of MoO3 on vanadium based catalysts for the selective catalytic reduction of NOx with NH3 at low temperature

The selective catalytic reduction(SCR) activities of the MoO_3 doped V/WTi catalysts prepared by the incipient wetness impregnation method at low temperature were investigated.The results showed that the addition of MoO_3 could enhance the NO_ xconversion at low temperature and the best SCR activity was obtained when the dosage of MoO_3 reached5 wt.%. The NH3-TPD and DRIFTS experiments indicated that the addition of MoO_3 changed the type and number of acid sites on the surface of catalysts and reaction activities of acid sites were altered at the same time. The redox capacity and amount of active oxygen species got improved for V3Mo5/WTi catalyst, which could be confirmed by the H_2-TPR and transient response experiments. Water vapor inhibited the NO_xconversion at low temperature. Deposition of ammonium sulfate or bisulfate might be main reason for the loss of catalytic activity in the presence of SO_2 at low temperature. Choosing the suitable NH_3/NO ratio and elevation of reaction temperature both could weaken the influence of SO_2 on the SCR activity of the V3Mo5/WTi catalyst. Thermal treatment of the deactivated catalyst at350°C could get the low temperature activity recovered. The decrease of GHSV improved the de NO_x efficiency at low temperature and we speculated that the rational technological process and operation parameters could contribute to the application of this kind of catalysts in real industrial environment.     

Effect of barium sulfate modification on the SO2 tolerance of V2O5 /TiO2 catalyst for NH3-SCR reaction

Sulfur poisoning of V_2O_5/BaSO_4–TiO_2(VBT),V_2O_5/WO_3–TiO_2(VWT) and V_2O_5/BaSO_4–WO_3–TiO_2(VBWT) catalysts was performed in wet air at 350℃ for 3 hr,and activities for the selective catalytic reduction of NO_x with NH_3 were evaluated for 200–500℃.The VBT catalyst showed higher NO_x conversions after sulfur poisoning than the other two catalysts.The introduction of barium sulfate contributed to strong acid sites for the as-received catalyst,and eliminated the redox cycle of active vanadium oxide to some extent,which resulted in a certain loss of activity.Readily decomposable sulfate species formed on VBT-S instead of inactive sulfates on VWT-S.These decomposable sulfates increased the number of strong acid sites significantly.Some sulfate species escaped during catalyst preparation and barium sulfate was reproduced during sulfur poisoning,which protects vanadia from sulfur oxide attachment to a great extent.Consequently,the VBT catalyst exhibited the best resistance to sulfur poisoning.     

关于医疗垃圾飞灰中二噁英在惰性气氛下的低温热脱附研究

以医疗垃圾焚烧炉布袋除尘器前管道内飞灰(BG)及布袋除尘器后飞灰(AG)为对象,研究不同温度及时间段下其在管式炉中的热脱附特性.结果表明,在低温氮气气氛下,热脱附作用较为明显,2种飞灰中的二噁英都有了不同程度的脱除,其中布袋前飞灰中二噁英的脱除率为82.9%～99.9%之间,毒性当量脱除率为77.3%～99.8%,布袋后飞灰中二噁英的脱除率为66.8%～99.8%之间,毒性当量脱除率为43.5%～99.6%.检测收集到的实验尾气,发现了二噁英的存在,且在300～350℃这个温度段生成量最多,且生成的有毒二噁英同系物中以OCDD为主.通过比较发现,当温度为400℃,加热时间为45 min时2种飞灰中的二噁英脱除效率最高.鉴于惰性气氛下的热脱附对处理飞灰中的二噁英具有较好的作用,可将其大规模应用于实际工程中.     

呼和浩特市可镇污水处理厂工程设计

呼和浩特市可镇污水处理厂近期建设规模1.0×104m3/d,远期总规模2.5×104m3/d。污水处理主体工艺采用组合式A2/O生化池+砂滤,污泥处理采用污泥贮池+带式浓缩脱水一体机,尾水采用液氯消毒,设计出水水质执行GB 18918—2002《城镇污水处理厂污染物排放标准》一级A排放标准。介绍了该工程的工艺流程、设计参数,总结分析了工艺设计的技术特点。同时阐述了针对低温条件下的运行保障措施和要求,为寒冷地区同类污水处理厂的设计提供参考和借鉴。     

Fe2O3 particles as superior catalysts for low temperature selective catalytic reduction of NO with NH3

Fe203 particle catalysts were experimentally studied in the low temperature selective catalytic reduction （SCR） of NO with NH3. The effects of reaction temperature, oxygen concentration, [NH3]/[NO] molar ratio and residence time on SCR activity were studied. It was found that Fe203 catalysts had high activity for the SCR of NO with NH3 in a broad temperature range of 150-270℃, and more than 95% NO conversion was obtained at 180℃ when the molar ratio [NH3]/[NO] = 1, the residence time was 0.48 seconds and 02 volume fraction was 3%. In addition, the effect of SO2 on SCR catalytic activity was also investigated at the temperature of 180℃. The results showed that deactivation of the Fe2O3 particles occurred due to the presence of SO2 and the NO conversion decreased from 99.2% to 58% in 240 min, since SO2 gradually decreased the catalytic activity of the catalysts. In addition, X-ray diffraction, Thermogravimetric analysis and Fourier transform infrared spectroscopy were used to characterize the fresh and deactivated Fe2O3 catalysts. The results showed that the deactivation caused by SO2 was due to the formation of metal sulfates and ammonium sulfates on the catalyst surface during the de-NO reaction, which could cause pore plugging and result in suppression of the catalytic activity.     

燃煤电厂PM2.5微细颗粒物控制新技术——旋转电极式电除尘性能特点及安装技术

本文介绍了燃煤电厂PM2.5微细颗粒物控制新技术——旋转电极式电除尘器的工作原理、性能特点.同时介绍了某电厂330MW机组旋转电极式电除尘改造工程应用实例.在积累多个旋转电极式电除尘器安装调试经验的基础上,介绍了旋转电极式电除尘器安装工艺流程及安装调试技术.     

若尔盖高原湿地藻类多样性研究

分别于夏、冬两季采集若尔盖高原湿地水样,利用传统培养及显微镜检的方法和现代分子生物学方法对其藻类多样性进行了研究.结果表明,夏季水样至少培养出4种绿藻,分别为普通小球藻(Chlorella vulgaris Beij.)、浮球藻(Planktosphaeriagelatinosa G.M.Smith)、繁茂栅列藻(Scenedesmus abundans Kirchner)和柱状栅列藻(Scenedesmus bijuga Turp.),均属于绿球藻(Chlorococcales),其中普通小球藻为优势藻种,并被分离纯化.显微镜检结果表明冬季水样中主要的藻类种群为硅藻,此结果符合在低温季节天然水体中常以硅藻为主的常理.蓝藻16S rRNA基因克隆文库中的主要类群为硅藻(Bacillaripiophyta,35.3%),其次为蓝藻,包括色球藻(Chroococcales,5.9%)、念珠藻(Nostocales,11.8%)、颤藻(Oscillatoriales,11.8%)和一些未知种属的蓝藻类群(Unclassified Cyanobacteria,35.3%),还发现一些与低温环境微生物相关的类群,如颤藻目细纤菌属(Leptolyngbya).     

Kinetics of selective catalytic reduction of NO by NH3 on Fe-Mo/ZSM-5 catalyst

The catalyst of Fe-Mo/ZSM-5 has been found to be more active than Fe-ZSM-5 and Mo/ZSM-5 separately for selective catalytic reduction (SCR) of nitric oxide (NO) with NH3. The kinetics of the SCR reaction in the presence of O2 was studied in this work. The results show that the observed reaction orders were 0.74-0.99, 0.01-0.13, and 0 for NO, O2 and NH3, respectively, at 350-450℃. And the apparent activation energy of the SCR was 65 kJ/mol on the Fe-Mo/ZSM-5 catalyst. The SCR mechanism was also deduced. Adsorbed NO species can react directly with adsorbed ammonia species on the active sites to form N2 and H2O. Gaseous O2 might serve as a reoxidizing agent for the active sites that have undergone reduction in the SCR process. It is also important to note that a certain amount of NO was decomposed directly over the Fe-Mo/ZSM-5 catalyst in the absence of NH3.     

Effect of manufacturing methods of AgCl/Al2O3 catalyst on selective catalytic reduction of NOx

The AgCl/Al2O3 catalyst has potential for use in the selective catalytic reduction (SCR) of NOx. A compound hydrocarbon, following oxygenation is used as a type of reducing agent. In this experiment, the AgCl/Al2O3 catalyst was produced by four different methods, and the differences among their reduction catalysis of NOx were compared. Ethanol was used as a type of reducing agent. X-ray diffraction analysis was performed to study the crystalline structure and scanning electron microscope and transmission electron microscope (TEM) were applied to determine the microindentation. The results indicated that, in the range of 350–400°C, there was no significant difference on the NOx reduction rate; however, there was dispersion at high and low temperature ranges. The size of the AgCl particles was about 20–100 nm.     

燃煤电厂烟气氮氧化物排放控制技术发展现状

在广泛查阅文献的基础上,对近年来国内外已成功应用和正在研究开发的一些主要的燃煤烟气氮氧化物控制技术进行了介绍。结合我国目前脱硝行业整体水平和国家环保政策要求,对我国脱硝行业技术研发方向提出了建议。