Alkali Resistant Fe-Zeolite Catalysts for SCR of NO with NH3 in Flue Gases

Fe-zeolite catalysts were prepared by ion-exchange and characterized by nitrogen physisorption, electron paramagnetic resonance (EPR) spectroscopy, NH₃-temperature programmed desorption (TPD), H₂-temperature programmed reduction (TPR) and Energy dispersive X-ray spectroscopy (EDX) methods. The effect of potassium doping on the acidic and redox properties of the Fe-zeolite catalysts were studied. The prepared catalysts showed high surface area and surface acidity. This is essential for increased alkali resistivity in comparison with conventional metal oxide supports like, e.g. TiO₂ and ZrO₂, towards e.g. potassium salts in flue gases from biomass fired power plants. These properties allowed both undoped and potassium doped Fe-zeolite catalysts to posses high activity during the selective catalytic reduction (SCR) of NO with NH₃. The extent of deactivation of the Fe-zeolite catalysts was further compared with commercial V₂O₅–WO₃–TiO₂ catalyst (VWT) with various levels of potassium poisoning. While VWT catalysts severely deactivated at relative low potassium concentration levels the Fe-zeolite catalysts also showed superior alkali resistivity even at high potassium loadings.     

The Role of Minute Droplets in the Separation of Aerosols from Gases

Air pollution is caused to a large extent by submicrometre liquid and solid particles called 'aerosols'. Separation of aerosols from residual gases is a major problem today. Well-known equipment like the venturi scrubber cannot handle submicrometre aerosols successfully. However, enlargement of the aerosols by condensed water vapour and subsequent separation by inertia forces in an air jet containing minute water droplets can lead to an acceptable process with moderate energy consumption. The generation of minute water droplets and their role in the separation of aerosols from gases is described in this paper.     

Laboratory and Field Test of a Sampling Method for Characterization of Combustion Aerosols at High Temperatures

The objective of this study was to design and experimentally examine a sampling method for high-temperature aerosols from biomass combustion, in which nucleation and condensation from fly ash forming vapors is controlled. The sampling method includes a high-temperature probe in which the hot gas is diluted and then cooled. Laboratory results from sampling a model aerosol with known concentrations of SiO₂ particles and KCl vapor showed that when using a high dilution ratio, the KCl vapor was effectively separated from the aerosol by deposition onto the probe walls. When a lower dilution ratio was used, the KCl vapor generated a distinct nucleation mode when cooled in the probe. The sampling method was also used for sampling flue gas from a circulating fluidized bed boiler fired with forest residues. The results suggest that the major fractions of Ca, K, S, and Zn were present as particles at 780°C, whereas most of the Cl and Pb were present as gases. The field results are consistent with results previously reported and indicate that the method can be used for efficient and precise characterization of high-temperature combustion aerosols containing inorganic vapors.     

Role of Cement Alkali Content in Acid Attack: A Pore-Solution and Pore-Size-Distribution Study

The behavior of hydrated portland cement pastes in an acid-buffered solution of acetic acid/sodium acetate (HAc/NaAc) (pH 4.5) during a period of 90 days at a temperature of 21°C has been studied. The changes that were caused by the acid ingress were monitored via analysis of the extracted pore solution. The evolution of the porosity and pore-size-distribution changes were evaluated by using intrusion mercury porosimetry, and those of crystalline compounds were evaluated by using X-ray diffractometry. A similar study was conducted with an equivalent series of samples that were immersed in distilled water. The results showed the important role that cement alkali content (1.03% K₂O, 0.2% Na₂O) has in the mechanism of the acid attack. Interesting correlations were established between pore-solution and porosity data.     

低碱水泥系列在高碱原料地区的研制与生产

0引言随着城市基础设施和高速公路建设的不断发展,人们对矽学科的认识也在进一步提高。自1940年美国报导厂碱一集料反应是引起检最严重和最普遍破坏原因之一后,有许多国家也不断发现碱一集料反应、据有关资料介绍1981年损坏的建筑物计算价值超过2700万英磅。在我国碱一集料反应引起的破坏实例也不少,如乌鲁木齐机场跑道面的破坏。该机场跑道面建于70年代初,至今已使用20多年,仍在正常使用寿命期内。该机场使用频率不太高,飞机荷载一般电都在设计范围内,但机场跑道面破坏却比较严重。道面砼板受冻融作用是一个重要的客观原因,但是从…     

高砷烟道灰预处理水浸液中锌砷分离

对经热水浸出的高砷烟道灰水浸液进行锌砷分离,基于单独使用Fe2(SO4)3和CaO除砷的实验结果,提出了Fe2(SO4)3-CaO耦合分离锌砷工艺. 结果表明,在溶液pH=2、摩尔比H2O2/As3+ 1.3:1, Fe3+/As5+ 1:1.5, Ca2+/As5+ 1.5:1及反应温度70℃、反应时间1.5 h的条件下,砷脱除率超过80%,锌没有损失,实现了锌砷高效分离.     

联碱生产洗盐水中硫酸根的脱除工艺研究

研究了采用氢氧化锆为吸附剂对洗盐水中的SO42-进行快速和低成本的脱除工艺。对反应条件及其影响因素进行了详细的讨论,确定了最佳工艺条件,SO42-脱除率达到90%以上。     

A Comparative Study of Different Methods for the Sampling of High Temperature Combustion Aerosols

Three different probes, respectively based on aerodynamic quenching, N₂ dilution, and thermophoresis, were used for particle sampling in biomass postcombustion gases from a laboratory reactor at different temperatures (from 1300 to 560°C). The different artifacts caused by the use of each probe were identified and compared. While the classical dilution sampling resulted in the formation (inside the probe) of particles comparable in size and composition to those already existing in the sampled gases, the aerodynamic quenching particle sampling (AQPS) probe always caused the nucleation of vapors into very small (15–20 nm) particles. The difference is attributed to the much higher cooling rate (～ 10⁸ K/s) at the entrance of the probe. The preliminary results of the thermophoretic probe also reveal significant deviations between the collected sample and the actual particle population in the sampled gas. In general, the results shown here highlight the difficulties in obtaining representative samples in this type of systems, as well as the existence of a variety of possible sampling artifacts, whose interpretation is not straightforward. The AQPS probe is found to provide better results than the other methods considered, and its use might enable the study of both the condensed and vapor phase in hot gases containing important amounts of condensable inorganic vapours.     

高含量杀虫单原粉生产工艺研究

工业上稳定低耗地生产９５％以上含量的杀虫单,一直是杀虫单行业的一大难题。通过分析影响杀虫单含量和消耗的几个主要因素,找出了它们工艺上控制参数的最佳组合,提出了低温氯化物脱水这种全新方法,从而得已按最佳参数进行工业生产,使得工业上稳定低耗地生产高含量杀虫单成为现实     

高碱地区低碱硅酸盐水泥熟料的生产

通过严格控制进厂原物料指标,优化工艺配料方案,尤其是用煤系陶土按一定比例替代页岩进行配料,碱含量满足要求,熟料的产质量均保持正常,提高了废物的利用率,减轻了黏土资源的浪费,从而实现了高碱地区低碱硅酸盐水泥熟料生产。     

纳米级聚合物微胶乳在高固含量水性涂料中的应用研究

利用一种改进的微乳聚合技术成功制得了纳米级高固含量聚合物微胶乳,可有效地将聚合物的固含量提高到１０％～４０％（ｍ／ｍ）。并能使微粒的直径保持在１０～４０ｎｍ之间。内部交联的功能化的聚合物微球也能用此方法制备,且可直接应用于水性涂料。试验结果表明,由此制得的涂膜性能优于常规乳液聚合方法所制取的。本文还讨论了成膜交联机理,发现胶粒纳米级的粒径和胶粒内及胶粒间的交联对获得较好的涂膜性能至关重要。     

高掺量高细矿渣水泥的研究

采用矿渣与熟料分别粉磨再混合粉磨的技术,研究了不同细度、掺量的矿渣微粉对水泥物理性能的影响,确定了水泥中SO3的最佳掺入量和高掺量高细矿渣水泥的组成,认为高细粉磨的矿渣以高掺量与熟料、石膏混合可制备出各项性能良好的水泥.     

高含量解草啶制取方法的研究

本文阐述了解草啶的特性以及提纯解草啶的方法、工艺流程。     

大掺量粉煤灰高性能混凝土的研究

本文从高分散性表面活性剂显著影响粉煤灰的形态效应而大幅降低混凝土用水量的角度出发,利用复合激发剂激发粉煤灰的火山灰效应,结合粉煤灰自身的微集料效应提高混凝土强度的技术手段,探讨了大掺量粉煤灰在混凝土中的应用,分析了高分散性表面活性剂与复合激发剂的组合对大掺量粉煤灰混凝土的作用机理。     

大型焦炉边火道加热研究

介绍大型焦炉边火道温度偏低的原因,针对其原因采取适当的技术措施,并提出改进的方案。     

成核剂含量对PS发泡复合材料泡孔形态的影响

在聚苯乙烯(PS)加入不同含量的成核剂,用自行研制的动态发泡模拟机研究了成核剂含量对PS发泡复合材料泡孔形态的影响。研究发现,成核剂有助于PS发泡材料形成大量成核点,泡孔成核更容易;并且PS中成核剂的含量不同会影响泡孔的形态,在发泡过程中尽量促进成核剂的分散,使体系内聚合物熔体、发泡剂和成核剂尽量均化,可以增加成核点数量并使泡孔分布均匀,改善泡孔形态。     

A Plug Flow Model for Chemical Reactions and Aerosol Nucleation and Growth in an Alkali-Containing Flue Gas

The paper presents a numerical model for the simulation of gas to particle conversion and the chemical changes during cooling of a flue gas from the combustion of fuels rich in volatile alkali species. For the homogeneous nucleation of alkali species the model uses the classical theory modified by the Tolman coefficient for the size dependent surface tension. A special adaptation of the theory to the nucleation of seeds of chloride salt from an equilibrium mixture of monomer and dimer chloride vapor molecules is also made. The growth of particles occurs by condensation and agglomeration. Different multicomponent growth models are treated. The local gas phase composition is determined from a gas phase chemical equilibrium calculation combined with finite reaction rate kinetics for slower reactions. The model is useful in the analysis of boiler operation with respect to the formation of particles, HCl, SO₂, and deposits.     

高掺量粉煤灰-矿渣超细粉建筑胶结料生产研究

以粉煤灰 -矿渣超细粉复合体系为主要材料 ,用普通激发剂激发其活性成分 ,配制成利废率达 80 %以上的建筑胶结料。通过正交试验对激发剂的配比进行优选。试验表明 ,掺入石灰 10 %、石膏 4%、Na2 CO3 0 .5 %和Na2 SO40 .5 %的复合激发剂能使粉煤灰 -矿渣超细粉复合体系的活性成分得到较好的激发。在该复合体系中掺入少量水泥能使该胶结料获得工程使用的强度。粉煤灰 -矿渣超细粉建筑胶结料具有原材料易得、成本低、利废率高等优点     

ICP-AES法测混凝土外加剂中碱含量的研究

研究了微波消解样品,试液用电感耦合等离子体原子发射光谱(ICP—AES)法测定混凝土外加剂中碱含量的新方法。对影响其光谱测量的各种因素进行了较为详细的研究,确定了实验的最佳测定条件,结果表明,钾和钠的检出限分别为0.855μg/mL和0.012μg/mL,回收率为92.0%~103.8%,RSD为0.87%~2.29%。该法准确、快速、简便,应用于混凝土外加剂中碱含量的测定,结果满意。