四种锅炉管材料650℃/26MPa的蒸汽氧化研究

研究了S30432、TP347H、TP310HCbN和T91钢4种锅炉管材料在650℃/26MPa超临界水蒸气中的氧化行为,氧化1 500h后,采用增重法测量试样单位表面上的质量变化,用扫描电子显微镜(SEM)及能谱仪(EDS)分析氧化膜表面及截面形貌、微观结构和元素分布,用X射线衍射仪(XRD)进行氧化膜物相表征.结果表明:4种材料氧化情况差异显著,其抗蒸汽氧化性能很大程度上取决于合金中Cr元素的含量;4种材料都形成了双层氧化膜结构,包括内层富Cr尖晶石型氧化物及外层铁氧化物(Fe3O4或Fe3O4+Fe2O3);氧化膜中形成的孔洞会成为阳离子由材料基体向氧化膜/蒸汽界面扩散,以及氧和水分子由氧化膜/蒸汽界面向金属基体扩散的快速通道,使氧化速率加快;S30432、TP347H及TP310HCbN氧化膜的剥落机制可用屈曲模型解释,T91钢氧化膜的剥落机制可用楔入模型解释.     

晶粒尺寸和表面状态对S30432钢蒸汽氧化行为的影响

利用自制的蒸汽氧化装置对不同晶粒度和表面状态的S30432钢管试样在650℃下进行不同试验时间节点的蒸汽氧化试验,采用光学显微镜、扫描电镜和X射线衍射等分析方法研究了氧化层的形貌、成分和相组成.结果表明：在试验时间内,不同的S30432钢管试样的抗蒸汽氧化性能存在差异;细化晶粒及提高晶粒度均匀性有利于提高S30432钢的抗蒸汽氧化性能;喷丸处理能改变钢管试样的内壁表面状态,加快Cr从基体向内壁表面扩散,形成富Cr的致密氧化层,显著降低了氧化膜的生长速度;在蒸汽氧化过程中形成的氧化层分内外两层：内层富Cr,与基体界面处形成高铬含量愈合层,外层为铁的氧化物.     

过热器受热面蒸汽氧化层形成机理研究

针对电厂锅炉屏式过热器TP304H钢管内壁蒸汽氧化现象,采用光学显微镜、扫描电镜、能谱和X射线衍射等测试技术,对其氧化层表面形貌,管内壁截面的Fe、Cr、Ni元素分布以及氧化层的物相进行了分析。研究结果表明:TP304H奥氏体不锈钢氧化层为双层结构,其内层为铁铬尖晶石结构FeCr2O4,外层为Fe3O4和Fe2O3氧化物结构,而Fe3O4多孔疏松结构和多层氧化物热膨胀系数差异是导致长期运行后氧化层的剥落重要原因。     

冷却制度对430不锈钢氧化层结构的影响

以430不锈钢为原料,系统研究冷却制度对不锈钢氧化层结构的影响;不同冷却制度条件下430不锈钢表面氧化层组成均为Fe2O3和Cr2O3,但空冷条件下的试样衍射峰强度明显高于雾冷条件下的试样;同时氧化层外层较为致密,内层为多孔结构,而且外层为富铁相,内层为富铬相,此外在雾冷条件下,铬元素不仅分布在内层氧化物中,且在中间层...     

STBA24钢管蒸汽氧化的微观特征研究

利用宏观检查、金相检验、电镜观察、能谱分析和X射线衍射仪等方法,对某热电厂过热器和再热器管内壁氧化皮的化学成分和组织结构进行了试验研究,探讨了STBA24钢高温蒸汽氧化的微观特征和氧化机理.结果表明:STBA24钢管在运行中,当管壁温度超过材料的许用温度时,易发生高温水蒸汽氧化;腐蚀产物分内外2层,外层以Fe2O3、Fe3O4为主,易剥落,内层为致密的保护性氧化物,具有长期抗氧化能力.金属材料的蒸汽氧化和剥落会增大管壁应力,造成管壁破裂或爆管.     

Inconel 740合金在空气和含有水蒸气的空气中的氧化研究

利用热重分析法、X射线衍射仪和扫描电镜与能谱分析仪研究了Inconel 740合金在空气和含有水蒸气的空气中的高温氧化行为,并分析了该合金的氧化机制.结果表明：Inconel 740合金在950℃的静态空气中氧化时,氧化动力学遵循抛物线规律,氧化膜黏附性能良好,表面氧化膜完整,外层由Cr2O3和少量的（Ni,Co）Cr2O4、TiO2组成,中间层为SiO2和Al2O3,内层氧化物为Al2O3和TiO2;合金在750℃含有10%水蒸气的空气中的腐蚀动力学也近似遵从抛物线规律,表面氧化膜很薄且致密性较差,表面氧化层主要为Cr2O3,内层氧化物为Al2O3和TiO2.     

低温渗铝涂层对P92钢650℃饱和蒸汽氧化行为的影响

利用低温粉末包埋渗法在P92钢服役温度下制备了铝化物涂层,并结合氧化增重法、扫描电镜观察及X射线衍射分析,研究了P92钢及其铝化物涂层在650℃下的饱和蒸汽氧化行为。结果表明:P92钢抗蒸汽氧化性能不足,350 h前氧化动力学遵循抛物线规律,外层疏松层氧化物Fe_3O_4+Fe_2O_3与内层氧化物FeCr_2O_4呈双层结构,氧化700 h后外层氧化膜发生严重剥落;低温包埋渗铝后,试样表面形成保护性Al_2O_3氧化膜,可显著提升P92钢抗蒸汽氧化性能;Al_2O_3氧化膜具有较慢的生长速度,因此铝化物涂层的耗损并不是继续形成Al_2O_3带来的消耗,而是Al向内扩散形成AlN相以及Fe向铝化物涂层扩散形成Fe_3Al相,从而降低Al浓度梯度。     

表面加工状态对Super 304H钢抗蒸汽氧化性能的影响

对6种不同表面加工状态(磨床粗磨、砂轮磨削、320号砂纸研磨、600号砂纸研磨、1200号砂纸研磨和抛光)的Super 304H钢在650℃/25MPa超临界水蒸气中的氧化行为进行了研究,采用增重法对氧化1 200h后的试样单位表面上的质量变化进行了测量,采用扫描电镜(SEM)和能谱仪(EDS)对氧化膜表面和截面形貌、微观结构和元素分布进行了分析,并利用X射线衍射仪(XRD)对氧化膜物相进行了表征.结果表明:Super 304H钢的抗蒸汽氧化性能对材料的表面加工状态比较敏感;不同表面加工状态的Super 304H钢经氧化后,试样单位表面上的质量变化、表面氧化物形态以及横截面氧化物形态差异明显;形成的典型氧化膜分内、外2层,外层氧化膜主要为Fe3O4,内层氧化膜主要为含Cr量较高的(Fe,Cr)3O4以及少量的Cr2O3;随着材料表面粗糙度的增加和比表面应变层的形成,越容易形成具有保护性的富铬氧化膜,Super 304H钢的抗蒸汽氧化性能越好.     

锅炉高温受热面蒸汽侧氧化膜在线监测技术研究

建立了高温受热面炉内壁温在线监测模型、氧化膜生长模型、氧化膜应力在线监测计算模型和氧化膜脱落评估模型等.在此基础上,开发了锅炉高温受热面蒸汽侧氧化膜管理系统,并利用该系统对某600MW超临界锅炉高温受热面炉内管壁温度和蒸汽侧氧化膜厚度及应力状态进行实时计算与分析.结果表明:利用该系统可以减小沿烟道宽度方向的热偏差,有效降低偏差屏的炉内温度,减缓管内氧化膜生成速率;通过对温度变化速率、氧化膜应力状态的实时监测,可以积极预防氧化膜的脱落和堆积.     

超临界锅炉末级过热器爆管原因的分析

为研究超临界锅炉末级过热器爆管的原因,对1台600MW超临界锅炉末级过热器爆管上游管和相关管样的内壁氧化物的宏观形态、微观结构,脱落氧化皮的微观结构、物相、各区域的微观形态和成分等进行了分析.结果表明:堵塞末级过热器下弯头造成过热器爆管的脱落氧化皮来自于T23/T91钢管的T23管段内壁,而非T91管段内壁;T23钢管内壁氧化皮为二层结构,外层为粗大柱状晶的纯磁铁矿(Fe3O4),内层为等轴细晶的含W和Cr的尖晶石;原生氧化皮内层存在一条或多条沿圆周方向排列的孔洞链,氧化皮容易沿孔洞链分离,从而造成氧化皮脱落.     

Synthesis of FeCo2O4@Co3O4 nanocomposites and their electrochemical catalytical performaces for energy-saving H2 prodcution

In this study, FeCo₂O₄@Co₃O₄ bifunctional catalysts with a unique structure combining nanosheets and nanowires were prepared on nickel foam by a simple hydrothermal + annealing method. The catalysts exhibited excellent catalytic activity for hydrogen production during urea electrooxidation reaction (UOR) and ethanol oxidation reaction (EOR). For UOR, the potential at 10 mA/cm² current density is 1.387 V and the tafel slope is 67 mV/dec. In the configured two-electrode electrolytic cell, the FeCo₂O₄@Co₃O₄ catalysts in the UOR and EOR processes required only 1.425 and 1.471 V, respectively, to produce a current density of 10 mA/cm², which is much less than that of the (oxygen evolution reaction) OER (1.640 V). In addition, the current density remained stable at a fixed potential during a long time (20 h) i-t test in the urea solution.     

An investigation on the mechanism of the increased NO2 emissions from H2-diesel dual fuel engine

The addition of hydrogen (H₂) into the intake air of a diesel engine was found to significantly increase the emissions of nitrogen dioxide (NO₂). Previous research demonstrated a strong correlation between the emissions of NO₂ and unburned H₂ in exhaust gas. However, the mechanism whereby H₂ addition in increasing NO₂ formation in a H₂-diesel dual fuel engine. Previously has not been investigated.This research numerically verified the hypothesis that the increased NO₂ emissions observed with the addition of H₂ was formed through the conversion from NO to NO₂ during the post combustion oxidation process of the unburned H₂ when mixed with the hot NO-containing combustion products. A variable volume single zone model with detailed chemistry was applied to simulate post-combustion oxidation process of the unburned H₂ and its effect on NO₂ emissions. The mixing of the unburned H₂ with the NO-containing hot combustion products was found to convert NO to NO₂. Such a conversion is promoted by the hydroperoxyl (HO₂) radical formed during the oxidation process of the H₂. The factors affecting the NO₂ formation and its destruction include the concentration of NO, H₂, O₂, and the temperature of the bulk mixture. When H₂ and hot NO-containing combustion products mixed during the early stage of expansion stroke, the NO₂ formed during H₂ oxidation was later dissociated to NO after the complete consumption of H₂. The complete combustion of H₂ exhausted the source of HO₂ necessary for the conversion from NO to NO₂. The mixing of H₂ with combustion products during the last part of the expansion stroke was not able to convert NO to NO₂ since the temperature was too low for H₂ to oxidize and to provide the HO₂ needed. The bulk mixture temperature range suitable for meaningful conversion from NO to NO₂ aided by HO₂ produced during the oxidation of H₂ was examined and presented.     

Effect of in situ growth of NiSe2 on NiAl layered double hydroxide on its electrocatalytic properties for methanol and urea

With high energy density and low theoretical potential, the methanol oxidation (MOR) and urea oxidation (UOR) are often used as substitute reactions to the oxygen evolution reaction (OER). As one of the popular non-precious metal catalysts for the MOR/UOR research in recent years, nickel-based layered double hydroxides (LDHs) have abundant active sites and low cost, but suffer from poor catalytic activity and poor stability. In the present study, we prepared NiAl LDH and then grew NiSe₂ in situ on its surface at different temperatures, and the catalyst obtained at 450 °C (4NiAlSe-450) exhibited excellent MOR/UOR electrocatalytic performance with potentials of 1.37 V vs. RHE and 1.36 V vs. RHE at a current density of 10 mA cm⁻², respectively, which were much higher than those of NiAl LDH (1.42 V vs. RHE and 1.39 vs. RHE). Chronoamperometry curves of 4NiAlSe-450 at 1.5 V potential showed that the methanol/urea oxidation was stable for more than 3 h. The physicochemical properties of 4NiAlSe-450 were analyzed by using X-ray diffraction, X-ray photoelectron spectroscopy and other techniques, and the results showed that the NiSe₂ nanoparticles were successfully grown in situ on the calcined layered structure, and therefore the excellent MOR/UOR electrocatalytic performance of 4NiAlSe-450 may be due to the synergistic effect between the NiAl composite oxides and NiSe₂.     

反应器形式对异丙苯氧化的影响

在100℃、0.5MPa下,以Na2CO3溶液为稳定剂的异丙苯液相空气氧化反应过程中,当反应时间相同时,在环流反应器内的过氧化氢异丙苯(CHP)浓度和异丙苯氧化速率均高于鼓泡反应器。在常压、85℃的UOP工艺条件下,经过诱导期后,高/径比相对较小的鼓泡槽反应器不用稳定剂比环流反应器和鼓泡塔反应器对异丙苯的氧化反应更为有利。     

Catalytic activity,stability and impedance behavior of PtRu/C,PtPd/C and PtSn/C bimetallic catalysts toward methanol and formic acid oxidation

PtRu, PtPd and PtSn with weight ratios of (2:1) on carbon black (Vulcan XC-72) supported bimetallic catalysts were prepared by using microwave method via chemically reduction of H₂PtCl₆·6H₂O, RuCl₃, PdCl₂ and SnCl₂·2H₂O precursors with ethylene glycol (EG). These prepared catalysts were systematically investigated and obtained results were compared with commercial Pt black, PtRu black catalysts and with each other. The catalysts were characterized with XRD, ICP-MS, EDS and TEM. The electrocatalytic activities, stability and impedance of the catalysts were investigated in sulfuric acid/methanol and sulfuric acid/formic acid mixtures using electrochemical measurements. The results showed that PtSn/C catalyst showed comparable activity and durability with commercial Pt/C catalyst toward methanol oxidation. The synthesized PtRu/C catalyst was found to completely oxidize methanol and it showed more catalytic activity than commercial PtRu catalyst. Bimetallic PtPd/C catalyst gave better activity than both commercial Pt black and synthesized Pt/C catalyst for oxidation of formic acid. Higher electrochemical active surface areas were obtained with supported bimetallic catalysts.     

The effect of CuO on a Pt−Based catalyst for oxidation in a low-temperature fuel cell

Electrocatalytic oxidation of methanol, ethanol, and formic acid has currently attracted research attention for low-temperature fuel cells. However, the efficiencies of these fuel cells mainly depend on the electrocatalytic activities of Pt-based anodic catalysts due to the problems of low kinetics for small organic molecule electro-oxidation. An anode catalyst can be developed by the addition of some metal oxides into a Pt-based catalyst, which can effectively promote the electro-oxidation of fuels based on small organic molecules. In this work, a nanocomposite catalyst consisting of multi-wall carbon nanotubes (CNTs), copper oxide (CuO) and Pt nanoparticles was synthesized and used to improve fuel cell oxidation. Due to its low cost and oxophilic character, the metal oxide can play a major role in the oxidation of CO. The synthesis of xPt?yCuO/CNT electrocatalysts was executed through two steps: supporting of CuO nanoparticles on CNTs by the alcothermal method followed by Pt loading onto the prepared CuO/CNT by chemical reduction. The as-prepared catalysts were physically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and electrochemical measurements. The results demonstrate that CuO is well dispersed onto the CNTs and that this oxide can further interact with the active Pt present on the as-prepared catalyst composites. The activity of various xPt?yCuO/CNT electrocatalysts was determined by cyclic voltammetry (CV), where x and y are the mass ratios of Pt and CuO, respectively. The presence of CuO was found to significantly contribute to enhanced electroactivity towards oxidation reactions. The 1Pt–3CuO/CNT electrocatalyst is a capable catalyst for improving low-temperature fuel cell applications.     

电泳涂装废水处理技术

叙述了涂装工艺、涂装废水性质以及废水处理技术,指出,废水的成分复杂,排放无规律,水质变化大,废水先经微电解氧化后加药中和沉淀,再经AO生化处理,活性炭吸附过滤后出水达到GB8978-1996污水综合排放标准中的一级排放标准。     

Electrooxidation of ethanol and glycerol on carbon supported PtCu nanoparticles

Four carbon supported PtCu nanostructured catalysts with Pt:Cu atomic ratios of 1:3.20, 1:2.23, 1:0.61 and 1:0.35 were synthesized by a two-step route, involving the chemical reduction of Cu ions on the carbon support, followed by the partial galvanic replacement of Cu atoms by Pt. Bimetallic nanostructured particles with average sizes in the range of 2.3–3.2 nm were obtained. The bimetallic catalysts with surface Pt contents between 20 and 55 at. % were formed by a Cu-rich core surrounded by a Pt-Cu shell, while that with the highest Pt content presented a uniform alloy structure instead of a core-shell arrangement. The electrocatalytic performance of the as-prepared materials toward ethanol electrooxidation in acid and alkaline media and glycerol oxidation in alkaline environment was investigated by cyclic voltammetry and chronoamperometry. It was observed that the electrocatalytic activity of PtCu nanoparticles was found to depend on the surface composition, platinum utilization efficiency, structure and Pt ensemble. Among the as-prepared catalysts, Pt_0·62Cu_0·38/C core-shell material showed the best performance for ethanol oxidation in both acid and alkaline environments, while Pt_0·24Cu_0·76/C and Pt_0·31Cu_0·69/C core-shell catalysts exhibited the highest activity for glycerol oxidation in alkaline medium. The electrochemical results showed that the catalytic activity of the bimetallic Cu@PtCu core-shell nanostructured nanoparticles is between four and ten times higher than that of a commercial Pt_0·51Ru_0·49/C catalyst.     

Oxidation behaviour of cast Ni–Cr alloys in steam at 800°C

Abstract

To evaluate the steam oxidation resistance of cast Ni base alloy candidates for advanced steam turbine casings, laboratory experiments were conducted at 800°C. Alloys ranged from weaker, solid solution strengthened alloys 230 and 625 to stronger, precipitation strengthened alloys 105, 263 and 740, which are more difficult to fabricate and join. In general, these Ni–Cr based alloys exhibit low mass gains and form thin, protective Cr rich external oxides in 17 bar steam or 1 bar air. However, Al and Ti in these alloys internally oxidise in all cases. After 5000 h exposures, the average and maximum internal oxide penetration depths were measured, and the values were ranked based on the alloy Al+Ti contents. The middle range of Al+Ti compositions investigated, such as for alloys 617, 263, 282 and 740, showed the deepest penetrations. Further characterisation of the reaction products by electron microprobe showed a complex behaviour including significant Ti incorporation into the scale formed in both steam and air, and Ti rich oxide at both the gas and metal interfaces. Based on the Al and Ti contents, the internal oxidation observed in these alloys in steam was atypical.