中低温SCR脱硝催化剂技术及工程应用案例分析

SCR脱硝技术应用可实现水泥生产NO_x超低排放，而中低温SCR脱硝有低运行成本、高脱硝效率等优势。通过对传统高温催化剂的改性研究，开发了具有低温活性、高抗硫抗碱尘的中低温催化剂，并在长兴南方5 000 t/d水泥熟料生产线SCR脱硝项目中得到了工程化应用。     

水泥窑SCR脱硝催化剂磨损机理分析及解决措施

水泥窑SCR脱硝系统运行过程中，催化剂的磨损过快问题逐步显现出来。水泥窑SCR脱硝系统催化剂磨损的主要原因有灰尘含量大、原始设计不合理和粉尘堵塞造成流场不均匀、吹灰制度不合理，催化剂自身抗磨性能差等。通过理论分析，催化剂磨损的最大影响因素为烟气流速，磨损速度与烟气流速的三次方相关。为缓解催化剂磨损快的问题，通常采取选择合理的催化剂，增加催化剂自身的抗磨性能，数值模拟合理的设计反应器流场，改善催化剂服役环境和合理的吹灰制度等方式进行解决，从而保证脱硝系统的运行稳定性，达到超低排放的环保要求。     

钕改性铁基催化剂用于氮氧化物脱除

采用分步浸渍法，分两步将金属铁和钕依次引入商业化成品二氧化钛表面，研究其脱硝性能。通过X射线衍射(XRD)、氮气吸附-脱附(N₂-BET)、X射线光电子能谱(XPS)、氨程序升温脱附(NH₃-TPD)、氢气程序升温还原(H₂-TPR)等方法对样品进行表征分析。通过氮气吸附-脱附发现，钕的引入使得负载铁后的催化剂比表面积减小。X射线衍射分析结果表明，引入的金属物种在催化剂表面具有良好的分散性。氨程序升温脱附测试结果显示，钕的引入增加了催化剂的总酸量，同时改变了催化剂的酸性分布。X射线光电子能谱测试结果表明，钕改性增加了催化剂表面吸附氧和铁(Ⅱ)的含量，有利于脱硝反应的进行。氢气程序升温还原测试结果表明，钕的引入使得催化剂氧化还原性能略有下降。活性测试结果表明，适量钕负载有利于提升催化剂的脱硝性能，钕元素在催化剂中的质量分数为9%时催化剂表现最优，最佳脱硝效率为81.4%。     

高尘烟气脱硝催化剂耐磨强度研究

本文对SCR脱硝催化剂的相关性能做出了详细的,准确的评价,对SCR脱硝催化剂的装置的性能检测结果进行深层次的研究探索。火电厂在进行催化剂的安装或替换前通过催化剂,有必要对烟气脱硝催化剂系统进行各种类型的性能测试实验,并且对所用的催化剂进行性能测验,脱硝催化剂耐磨强度是火电厂烟气脱硝系统的运作管理的重要依据。     

废弃选择性催化还原催化剂混掺对新催化剂脱硝性能的影响

采用"混炼-挤出-干燥-煅烧"工艺制备了不同废弃选择性催化还原（SCR）催化剂混掺比例的新催化剂样品,在自制实验台架上进行了脱硝性能和脱硝寿命评估实验。实验表明,当废催化剂混掺比例小于5%时,样品脱硝性能相比无混掺样品有轻微下降,催化剂脱硝效率随运行时间的衰减速率正常;当混掺比例大于5%时,催化剂样品脱硝性能大幅衰减,催化剂寿命缩短。结合N₂吸附-脱附、扫描电子显微镜（SEM）、X射线荧光光谱（XRF）、X射线衍射（XRD）等表征手段分析,废催化剂的掺入会将碱金属、As等有害物质带入到高混掺量的样品中,导致催化剂脱硝性能下降;混掺比例高达15%时,15-cat样品表面复杂程度大幅下降,不利于SCR反应进行。实验论证了较高废弃催化剂混掺比例会严重影响制备所得新催化剂的脱硝性能。     

水泥窑低温SCR脱硝技术研究

介绍了研究水泥窑低温脱硝的必要性,阐述了水泥窑低温SCR脱硝工艺技术路线和工艺布置。通过对低温SCR脱硝技术与中温SCR脱硝技术对比,表明低温SCR脱硝技术具有安装条件可选择性强、成本费用小、催化剂用量少、维护方便等优点。并且通过对几种低温SCR脱硝催化剂的性能研究,结果表明需要在提高其活性、选择性、抗SO_2、K、Na等中毒能力、机械强度及稳定性、再生性能等方面对其进行改进。     

水泥窑SCR脱硝吹灰方式的选择应用

SCR脱硝技术的核心是催化剂,水泥窑烟气中粉尘含量高,易使催化剂堵塞和中毒失活。有效的吹灰系统是水泥窑SCR脱硝催化剂正常运行的关键之一。本文论述了水泥窑SCR脱硝吹灰装置比较与选择,为水泥窑SCR脱硝技术的进一步完善和推广提供一定的积累。     

煅烧温度对V2O5-WO3-TiO2体系SCR脱硝催化剂耐磨损性能影响研究

选用市场上常见的18×18孔蜂窝式SCR脱硝催化剂干燥样品,经过不同温度煅烧后,测试其磨损率。结果表明煅烧温度越高,催化剂耐磨损性能表现越好。同时研究了煅烧温度对催化剂比表面积(BET)的影响,温度过高会导致催化剂烧结,BET下降。煅烧温度在540-650℃范围内,对脱硝催化剂的脱硝效率无明显影响。     

微波热解制备γ-Fe2O3催化剂及其SCR脱硝性能

以 FeSO4·7H2O[Fe(NO3)3·9H2O]为铁源,采用新型微波热解法制备γ-Fe2O3[α-Fe2O3]催化剂样品,通过XRD、N2等温吸附-脱附、压汞法等实验手段对催化剂样品晶相、微观孔结构等进行表征;考察两种催化剂样品的 NH3-SCR 脱硝性能,通过归一化处理得到两种催化剂在不同温度下的本征脱硝反应速率,同时对比研究了γ-Fe2O3与钒系催化剂的脱硝活性;研究氨氮比、氧浓度等运行参数对γ-Fe2O3催化剂NH3-SCR脱硝性能的影响规律,并对其抗硫抗水性能进行考察。结果表明：采用新型微波热解法可得到纯度较高的γ-Fe2O3催化剂,其介孔分布合理且大孔数量丰富;同时γ-Fe2O3催化剂表现出优于α-Fe2O3催化剂的脱硝性能,400℃时最大 NOx转化率达到96%,300、325、350℃下单位面积脱硝速率达到α-Fe2O3催化剂的3倍左右;γ-Fe2O3催化剂具备优良的抗硫抗水性能,其最佳氨氮比为1、最佳氧体积分数为3.5%。     

工业MnOx颗粒催化剂的制备及其低温脱硝应用研究

以工业硫酸锰为前体，通过沉淀、洗涤、挤出、煅烧步骤批量制备了高活性颗粒状低温MnO_x脱硝催化剂（?5 mm×30 mm）。针对天然气冷热电三联供高含水低含硫烟气开展应用示范，研究催化剂在不同工况下的脱硝性能与长周期活性稳定性，结果表明：在入口NO_x浓度850~1000 mg/m3、床层温度145~175℃、空速4405 h^-1工况条件下，脱硝率达到87.88%～97.47%，连续运行1180 h后脱硝效率有约3%的微弱衰减。对长周期运行后催化剂进行取样，进行XRD、BET、SEM表征及活性测试结果表明：该催化剂在该高湿烟气长时间运行中发生了一定程度的晶型转变，颗粒烧结、尺寸变大以及比表面积降低，导致其脱硝活性降低。该研究结果将为高活性锰基催化剂的制备及其低温脱硝工业应用提供参考和借鉴。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.