铝灰脱氮的实验研究

研究了一种新的铝灰脱氮工艺。讨论了焙烧温度,药剂添加比和保温时间对铝灰脱氮率的影响。采用XRD,SEM,EDS,XRF和氮元素分析仪分析了焙烧前后的铝灰。铝灰与药剂的混合焙烧可以有效地脱除铝灰中的氮化铝。保持焙烧温度为890～920℃,药剂添加比为32.5～35 wt.%,保温时间为2.5～3 h,可以达到较好的脱氮效果,最大脱氮率达到98.13%。考虑到能耗和成本问题,推荐的焙烧条件为890℃,35%和2.5 h。AlN最终分解为Al_2O_3和N_2,药剂与铝灰中的Al_2O_3和SiO_2反应形成多孔结构的Na_(1.95)(Al_(1.95)Si_(0.05)O_4),称为沸石。脱氮过程无废水废渣、环境友好。     

超重力技术在海洋工业气体净化领域应用试验

本文介绍了一种新兴的方法,即采用超重力技术结合循环再生药剂--铁基脱硫剂开展了天然气中H2S脱除中试实验。实验中考察气液比,超重力机转速,环状多孔填料床(RPB)种类,药剂循环量等因素对脱硫效果的影响。根据实验结论,采用超重力技术结合铁基脱硫剂进行脱除酸性气体效果良好,并且基于超重力机设备运行稳定、占用体积小等特点,可以应用于海上平台进行气体净化,工业化应用前景良好。     

铬盐清洁生产工艺中铝硅的脱除

研究铬盐清洁生产工艺中铝硅的脱除。理论计算表明：CaO加入浸出液中不会有致癌物铬酸钙的生成。结果表明：在反应温度为70-90℃时,添加适量的CaO,浸出液中的铝硅可以脱除到要求值。无铁渣存在时脱铝硅产物为Ca2.93Al1.97Si0.64O2.56（OH）9.44,有铁渣存在时为Ca3AlFe（SiO4）（OH）8。铁渣的存在可以加速铝硅脱除反应的速度,提高铝硅的脱除率,而溶液中K2CO3的浓度对CaO脱除铝硅的影响不大。     

钢渣用于烧结烟气脱硫的动力学分析

根据喷射鼓泡反应器内鼓泡区和反应区的主要限制因素,通过建立双模理论讨论钢渣浆液脱除烧结烟气中SO_2的影响因素。在无化学反应的气液两相传质受气膜、液膜共同控制下,假设钢渣脱硫反应是在瞬间和不可逆的条件下完成,钢渣脱除烧结烟气中SO_2的吸收速率近似为气膜传质,即该反应是气膜控制反应。     

高岭石脱水反应的非等温热重法研究

在系统分析非等温固相反应特点的基础上,建立了非等温脱水反应速率方程.采用非等温热重法、通过计算机辅助计算,对高岭石脱水反应动力学规律进行了研究.结果表明:由于高岭石晶体结构中内、外羟基脱除的顺序不同,其脱水反应机制在反应分数(α)为0.7左右时发生改变.在反应前期(0＜α＜0.7)时,脱水反应遵循二维扩散控制规律,脱水反应表观活化能为159.682 kJ/mol、表观频率因子为1.007×10 10/min.     

低品位菱镁矿浮选试验研究

针对辽宁某低品位菱镁矿,采用反-正浮选工艺进行了硅钙杂质脱除研究。其中,反浮选作业采用阳离子捕收剂BK428,主要脱除含硅脉石;正浮选作业采用阴离子捕收剂BK420,强化含钙脉石脱除。试验结果表明,采用上述工艺流程与药剂制度可以使MgO品位为43.52%,SiO2含量3.74%和CaO含量2.69%的原矿,获得MgO品位为47.02%的精矿,菱镁矿精矿中SiO2和CaO含量分别降低到0.29%和0.93%,MgO回收率为71.64%。达到了选矿除杂的目的。为综合利用菱镁矿资源打下基础。     

拜耳法生产系统中硫化钠除锌正交试验分析

对拜耳液中硫化钠法脱除杂质锌进行评价,采用正交试验对比反应温度、反应时间及硫化钠浓度三因素对除锌效果的影响。结果表明:对除锌效果影响最大的是硫化钠浓度,其次是反应时间和反应温度。当反应温度为60℃,反应时间为120min,硫化钠浓度为0.5g/L时除锌效果最佳,拜耳液中杂质锌从70mg/L脱除到10mg/L。     

铑催化剂在NBR加氢领域的应用及回收方法

研究了铑催化剂在丁腈橡胶(NBR)均相加氢领域的应用,并开发了一种新的水相萃取回收铑的方法,首次以氯化亚锡为络合剂,2mol/L盐酸为萃取剂,可以很容易从氢化丁腈橡胶(HNBR)胶液中脱除铑催化剂。主要研究反应温度、时间、络合剂用量及萃取剂用量等条件对脱除铑催化剂的影响,在得到铑络合催化剂的最佳脱除条件下,铑催化剂的脱除率可达99%以上。IR以及1HNMR表征表明这种脱除铑催化剂工艺对HNBR的结构无影响,且不影响耐油的CN基团。     

响应曲面法优化黄金氰渣亚硫酸钠-空气氧化法脱氰工艺

采用氰化法进行提金处理会产生大量黄金氰渣，对环境安全和人体健康产生严重危害，根据国家标准必须对其进行脱氰处理。使用亚硫酸钠-空气氧化法对某黄金企业产生的黄金氰渣进行脱氰处理，利用响应曲面法探究各因素对脱氰结果的影响及交互作用，进而得到脱氰的最佳工艺条件。结果表明：矿浆初始pH值、亚硫酸钠用量以及反应温度对脱氰结果产生明显影响，空气充入量的影响不大，脱氰反应在开始的15 min内迅速进行，60 min后基本反应完全。对响应曲面模型预测结果进行优化，在最佳条件初始pH值12.90，药剂用量为理论量的3.5倍，反应温度为40℃时对氰渣进行脱氰处理，总氰化物脱除率可达到88.94%，脱氰尾渣毒性浸出液中总氰含量为2.95 mg/L，满足国家标准。     

基于真空立体闪蒸技术的海上油田老化油处理系统的设计与试验

为了解决海上油田的老化油处理问题,提出了基于真空立体闪蒸技术的老化油处理工艺,并试制了一台样机对流花油田的老化油样品进行了脱水试验.试验结果表明,该工艺设计合理,简便高效,所试制的样机结构紧凑、效率高,操作简便,不需要添加药剂,可以将老化油含水率脱除至0.5％以下,达到外输原油标准,满足浮式生产储卸油装置(FPSO)和...     

Heißkorrosion durch Verbrennungsrodukte von Heizölen hoher und mittlere Dichte

High-temperature corrosion by products of combustion of fuel oils of high and medium density The author describes a pilot plant for the investigation of the corrosive attack by products of combustion of heavy and light fuel oils on 18 different materials at 650, 700 and 750° C; test conditions are maintained widely comparable. The materials were selected in view of the technical suitability for the construction of turbine blades. The following fuel oils were used: (a) heavy fuel oils having a high ash content; (b) oils having a low ash content; (c) a light fuel oil to which the author added, gradually and in the form of oil-soluble compounds, the elements S, Na and V which are considered as mainly responsible for the corrosion. The oils mentioned under (c) permitted to show that

• 1 The three elements mentioned, in the form of their compounds formed during combustion, are mainly responsible for the corrosion;
• 2 It is not an individual element or its compounds but the combination of the three aggressive ash species which produces the damages found in the tests.

Thanks to this investigation the solution of the problem of corrosion by fuel oils has brought a little closer to its final solution although another considerable research effort will have to be made in order to establish such measures as might be able to prevent such corrosion.     

Processing intermetallic composites by self-propagating,high-temperature synthesis

Initiated at the interface of dissimilar elemental metal foils, a self-propagating, high-temperature synthesis (SHS) reaction can be used to produce a fully dense, well-bonded metal-intermetallic layered composite. In the research described here, aluminum foils were sandwiched between metal foils (Fe, Ni, Ti) and heated in a hot press to approximately the melting point of aluminum. An SHS reaction occurred at the metal-aluminum interface, consuming all of the aluminum foil and part of the metal foil, resulting in a strongly bonded metal-aluminide interface. Tensile tests conducted at room temperature revealed that composites can be designed to behave in a high-strength and high-toughness manner by altering the thicknesses of the elemental foils.     

Mechanism of high-temperature sulphide corrosion of metals and alloys

Sulfidation appears to be considerably more suitable than oxidation for studying the high-temperature behaviour of metals. Sulfide scales are formed at considerably higher rates and at lower temperatures, in addition it is much easier to work with the radioactive sulfide isotope. The experiments can be conducted in sulfur vapour or in hydrogen/hydrogen sulfide mixtures; differences are due only to different sulfur partial pressures. Sulfide scale is formed on pure metals (e. g. Cu, Ag, Ni) as well as in binary or ternary alloys. (e. g. FeNi, NiCr, CuZn, CoCr, FeCrAl) with consistantly reproducible results. Irrespective of scale thickness and structure the reaction rates are always controlled by outward diffusion with the high defect concentration favouring high reaction rates. Since various metals tend to form low melting metal/metal sulfide eutectics, it is necessary to keep temperatures below the particular melting point. Contrary to inner oxidation there is no inner sulfidation. The protective action of sulfide scale is considerably inferior to that of oxide scale. According to the results of the present compilation no material has become available which combines sufficient scaling resistance with good high-temperature mechanical properties. Solution of this problem may perhaps be found by adding rare earth metals.     

Ti/Al异种合金电弧熔钎焊接头温度场与界面微观组织

采用交流TIG焊电弧与AlSi12焊丝实现了TC4钛合金与LF6铝合金熔钎焊连接,通过有限元软件分析接头温度场,并利用扫描电镜观察接头钎焊界面的微观组织特征.结果表明,接头温度分布极不均匀,钛侧梯度大高温区窄,铝侧梯度小高温区范围广,冷却时高温区逐渐向钛侧偏移.当钨极正对钛钝边时,等温线平行于钎焊界面,温度分布均匀,有利于形成组织均匀的界面反应层.冷体熔钎焊加速了钎焊界面的冷却,降低了钛的溶解量,可抑制金属间化合物的生长.化合物层形貌由空冷时的锯齿状转变为胞状生长.     

Development and Property Tuning of Refractory High-Entropy Alloys: A Review

In the past decade, multi-principal element high-entropy alloys (referred to as high-entropy alloys, HEAs) are an emerging alloy material, which has been developed rapidly and has become a research hotspot in the field of metal materials. It breaks the alloy design concept of one or two principal elements in traditional alloys. It is composed of five or more principal elements, and the atomic percentage (at.%) of each element is greater than 5% but not more than 35%. The high-entropy effect caused by the increase of alloy principal elements makes the crystals easy form body-centered cubic or face-centered cubic structures, and may be accompanied by intergranular compounds and nanocrystals, to achieve solid solution strengthening, precipitation strengthening, and dispersion strengthening. The optimized design of alloy composition can make HEAs exhibit much better than traditional alloys such as high-strength steel, stainless steel, copper-nickel alloy, and nickel-based superalloy in terms of high strength, high hardness, high-temperature oxidation resistance, and corrosion resistance. At present, refractory high-entropy alloys (RHEAs) containing high-melting refractory metal elements have excellent room temperature and high-temperature properties, and their potential high-temperature application value has attracted widespread attention in the high-temperature field. This article reviews the research status and preparation methods of RHEAs and analyzes the microstructure in each system and then summarizes the various properties of RHEAs, including high strength, wear resistance, high-temperature oxidation resistance, corrosion resistance, etc., and the common property tuning methods of RHEAs are explained, and the existing main strengthening and toughening mechanisms of RHEAs are revealed. This knowledge will help the on-demand design of RHEAs, which is a crucial trend in future development. Finally, the development and application prospects of RHEAs are prospected to guide future research.     

XPS STUDIES OF OXIDATION BEHAVIOR OF NICKEL AND THERMAL STABILITY OF SURFACE OXIDES

Surface oxidation of polycrystalline nickel foil in air and pure water at different temperaturesand the thermal stability of the surface oxides have been investigated by means of XPS.In ad-dition to NiO,Ni_2O_3 is formed especially after long periods of air exposure.Nickel surfacesare much less reactive to pure water than to air.The thermal stability of the surface oxides isrelated to oxidative temperature.The surface species of oxides formed by air exposure attemperatures below 120℃ can be reduced into nickel metal after heating the sample in vacuumat 300℃ for only 10 minutes (in the case of room temperature) to 1 h (in the case of 120℃).This reduction is caused by reaction with surface carbon contaminants.However,the surfacespecies of nickel oxides formed by air exposure with heating at temperatures above 200℃ cannot be reduced into metal after heating the sample in vacuum at 300℃ for 1h.     

采用自蔓延高温合成技术连接TiAl合金

采用自蔓延高温合成技术实现了TiAl合金的连接。在连接过程中采用了具有很高放热量的Ti-Al-C中间层以及外加电磁场辅助连接。连接接头包括3个典型的反应区域,靠近TiAl母材界面处发现了深灰色的TiAl,反应层,在中间层内观察到了TiC颗粒以及Ti-Al系化合物。直接连接时由于产物和反应物之间的比热差,杂质的气化和孔隙中束缚气体的释放而导致孔隙无法避免。为了提高致密度,在粉末压坯和TiAl母材之间添加了Ag-Cu钎料箔。在SHS反应过程中熔化的钎料改善了中间层对TiAl母材的润湿同时填充到了中间层反应产物的孔隙中,采用这种方法能够提高反应产物的致密度和连接质量。     

Special aspects of localized High-temperature corrosion

As in aqueous corrosion a localized corrosive attack can be important in high-temperature corrosion of metallic materials and become, unvoluntarily, a lifetime determining factor for combustion systems. Deposit-induced corrosion is the most important form of localized corrosion on alloy 800 and other materials in advanced coal combustion systems. Coal-ash deposits may cause a sulfidation/oxidation reaction which propagates preferentially along grain boundaries into the underlying metallic material. Preferred grain boundary corrosion may also occur in the walls of the fuel nozzle tubes of gas combustion systems. In this case, an oxidation reaction takes place. The lifetime of the tubes can be increased by use of a special alloy 601 H grade. Pitting may be observed in coal combustion systems. It has also been observed on alloy 601 after service in ceramic firing kilns where it is promoted by the presence of chlorine. Additionally, pitting occurs under carburizing conditions (metal dusting) as does cracking being similar in appearance to stress corrosion cracking in aqueous corrosion. Compared to deposit-induced and grain boundary corrosion, crevice corrosion is of minor importance in high-temperature corrosion. Only one example has been identified so far on alloy 600 but which may also be interpreted as a kind of deposit-induced corrosion.     

Phase-field modelling of self-propagating high-temperature synthesis of NiAl

A phase-field model is developed and used to simulate high-temperature synthesis of intermetallic compounds. The model is based on a thermodynamic formulation, which incorporates the formation of chemically ordered phases and the associated heat generation. In contrast to previous approaches to modelling of high-temperature synthesis of intermetallics, the present model can be used to analyse the kinetics of the process at the microstructure level. The model takes general thermodynamic and kinetic parameters as input and gives as output a spatially resolved sequence of phase formation, from which the overall reaction kinetics can be inferred. Thus, no additional assumption has to be made on the nature of the kinetic mechanisms or on the magnitude of the overall reaction rate. Beside prediction of the microstructure, the model captures the key thermal characteristics of the combustion synthesis in both modes of thermal explosion and self-propagation. The results of simulations, as applied to the case of intermetallic formation in a simplified Ni–Al system, are shown to be consistent with the existing experimental data.     

Über den Mechanismus der Zunderbildung auf Metallen und binären Legierungen

The mechanism of scale formation on metals and binary alloys The scale formed during high-temperature oxidation of many metals consists of two layers which clearly differ from each other morphologically yet occur in the same phase of the reaction product. The inner layer in direct contact with the metal is porous whilst the outer layer is compact. Experiments have shown that the inner layer is formed as a result of secondary processes connected with the influence of the metal consumption zone on the progress of the oxidation process. As the reaction product cannot fully adapt itself to the continually shrinking metal core, a gap occurs between the metal and the reaction product. At the boundary between this gap and the scale, the reaction product begins to decompose. The oxygen atoms liberated as a result of this decomposition react with the metal core, thus giving rise to the formation of the inner layer of scale in the metal consumption zone. The dissociation of the outer layer thus has an anisotrope character so that, in the originally compact layer of scale, a porous consumption zone is formed. The singlephase reaction product is actually composed of three layers, viz. a compact outer layer, a porous transition layer, and a porous inner layer. The porous consumption zone may even comprise the entire originally compact layer of scale so that the oxygen is able to diffuse towards the metal core through fissures and gaps in the reaction product.