Hydrogen production through catalytic low-temperature bio-ethanol steam reforming

As a provider of our energy requirements, hydrogen seems to be one of most promising fuels, in particular when used to feed PEM fuel cells. When produced from a renewable source, it has got the potential to reduce the dependence on non-renewable fossil fuels and lower the amount of harmful emissions. Ethanol steam-reforming (ESR) reaction is an interesting option to obtain a H₂- and CH₄-rich stream with a low content of CO, combining the deep knowledge of the technology with the advantage of the biomass-derived feedstock. Thermodynamic analysis has indicated that the most interesting operating range to enhance the H₂ production and minimize CO and coke formation requires low pressure, high temperature, and high water-to-ethanol molar ratio. On the other hand, despite its endothermic nature, ESR could be carried out at low temperature, to increase overall thermal efficiency, even if at these conditions the catalyst's deactivation, due to coking and sintering phenomena, is not negligible. The main objective of this study is to investigate on the activity, stability, and durability of bimetallic Pt–Ni and Pt–Co catalysts supported on CeO₂ for low-temperature bio-ESR reaction. The catalysts have been prepared through different methods and with an optimized metal's content. They have also been characterized with various physico-chemical characterization tests, and the catalytic studies have been carried out in a lab-scale apparatus. While evaluating the effects on the catalysts' performances of preparation method, reaction temperature, space time, and water-to-ethanol molar ratio, the selected catalysts were found effective for the production of H₂ by steam reforming at low temperature. In particular, the Pt/Ni/CeO₂ catalyst shows a perfect agreement with equilibrium calculations yet at low contact times, although some carbon deposition occurs. Also the cobalt-based catalysts appear attractive. The relative rates of carbon growth versus gasification have been studied, and ascending water contents were used to study the effect of steam addition in the feed stream. An in-depth investigation of the reaction mechanism and the evaluation of the kinetic parameters will be crucial to complete the study of the proposed process.     

基于含油废水处理的电催化膜反应器优化设计及性能研究

以负载纳米TiO2的电催化膜为阳极,辅助电极为阴极,构成电催化膜反应器用于含油废水处理.考察了电极间距、电解质浓度、电流密度、空时速率、pH和温度对电催化膜反应器降解效果即含油废水化学需氧量(COD)去除率的影响.根据单因素实验分析结果,采用响应面法对电极间距、电解质浓度、pH和温度四个参数进行优化,得出最佳参数为:电极间距43.1mm,电解质浓度14.3 g/L,pH=6.3,温度32.5℃.在电流密度0.312mA/cm2,空时速率15.8 h-1的条件下,电催化膜反应器处理200mg/L含油废水COD去除率为97.54％,能耗为0.75 kWh/m3.     

Using a membrane reactor for the oxidative coupling of methane: simulation and optimization

An oxidative coupling of methane (OCM) is a promising process to convert methane into ethylene and ethane; however, it suffers from the relatively low selectivity and yield of ethylene at high methane conversion. In this study, a membrane reactor is applied to the OCM process in order to prevent the deep oxidation of a desirable ethylene product. The mathematical model of OCM process based on mass and energy balances coupled with detailed OCM kinetic model is employed to examine the performance of OCM membrane reactor in terms of CH₄ conversion, C₂ selectivity, and C₂ yield. The influences of key operating parameters (i.e., temperature, methane-to-oxygen feed ratio, and methane flow rate) on the OCM reactor performance are further analyzed. The simulation results indicate that the OCM membrane reactor operated at higher operating temperature and lower methane-to-oxygen feed ratio can improve C₂ production. An optimization of the OCM membrane reactor using a surface response methodology is proposed in this work to determine its optimal operating conditions. The central composite design is used to study the interaction of process variables (i.e., temperature, methane-to-oxygen feed ratio, and methane flow rate) and to find the optimum process operation to maximize the C₂ products yield.     

甲烷水蒸气重整反应研究进展

甲烷水蒸气重整(SMR)作为可与多种高温发电系统耦合的燃料供应过程,目前受到相当普遍的重视。本文从SMR的过程和反应机理、甲烷重整催化剂材料和性能评价、传统反应器和微反应器的SMR性能比较,以及耦合SMR系统的匹配等方面,对SMR反应的研究进展进行了归纳和分析。分析结果表明,目前与固体氧化物燃料电池(SOFC)耦合的SMR反应,尤其是与非传统的微小型反应器匹配的催化剂材料、反应器结构设计、结构与材料一体化的研究都有待深入。     

Grafted NiO on natural olivine for dry reforming of methane

Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ray diffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe)₂SiO₄ structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism.The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparation method and the calcination temperature. For calcination at 1100 °C, the effects of the amount of NiO and the number of impregnation have been studied. At a high temperature of calcination (1400 °C), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH₄+CO₂) yielding 96% CO and 76% H₂. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system.Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system.     

Grafted NiO on natural olivine for dry reforming of methane

Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-raydiffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe)₂SiO₄ structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism.

The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparationmethod and the calcination temperature. For calcination at 1100 ºC, the effects of the amount ofNiO and the number of impregnation have been studied. At a high temperature of calcination (1400 ºC), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH₄ + CO₂) yielding 96% CO and 76% H₂. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system.

Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system.     

Multiwalled carbon nanotubes-supported Nickel catalysts for the steam reforming of propane

Multiwalled carbon nanotubes (MWCNTs)-supported nickel catalysts with different metal-loading contents were synthesized trough deposition–precipitation (DP) method for its subsequent performance study on steam reforming reaction of propane. The metal-loading content was set at 5, 10, 20, and 25% of nickel. Results showed that 20 wt% nickel oxide over MWCNTs (20% NiO/MWCNTs) had the best performance, on the propane steam reforming reaction, in terms of H₂ conversion comparing with the rest of the NiO/MWCNTs catalysts (5, 10, 25 wt% Ni) and a nickel over alumina (Ni/Al₂O₃) commercial catalyst. The features of the NiO/MWCNTs catalysts were studied trough FT-IR, Raman spectroscopy, N₂ adsorption–desorption isotherms, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy measurements. The results evidenced that optimum relation between Ni content, Ni dispersion, and particle size played a main role in the catalyst performance, rendering the 20% NiO/MWCNT as the most promising, among the catalysts studied, for the steam reforming of propane.     

Stable Ni/Al2O3 catalysts for methane dry reforming

To obtain insight into the effect of metal-support interactions in the CO₂ reforming of CH₄, a series of alumina-supported nickel catalysts were prepared by calcination of the catalyst precursors in air at different temperatures. The increase in the intensity of Ni-Al₂O₃ interactions with the calcination temperature was found to be unfavorable to the reduction of the catalyst. However, the catalyst with strong Ni-Al₂O₃ interactions suppressed carbon deposition effectively, which can be attributed to the formation of spinel, NiAl₂O₄, after calcination. When the reaction was carried out at temperatures higher than 973 K, all the catalysts tended to exhibit equilibrium activity. Received: 30 March 2000     

PdZn/ZrO2催化剂上二甲醚低温蒸汽重整制氢

采用溶胶-凝胶法制备ZrO2载体,然后采用沉积沉淀法制备一系列PdZn/ZrO2重整催化剂,对其进行BET、XRD的分析;并将其与水解催化剂(m(ZSM-5)∶m(γ-Al2O3)=2∶1)复合用于二甲醚蒸汽重整反应.考察了载体焙烧温度、表面活性剂、活性组分负载顺序和催化剂的装填方式对重整反应性能的影响.研究结果表明,以500℃焙烧,加入表面活性剂及PdZn共同负载制备的PdZn/ZrO2重整催化剂和水解催化剂机械混合组成的复合催化剂显示出较好的活性和较高的选择性,H2收率可达56.1％,CO2选择性为90.2％.     

乙醇水蒸气重整制氢催化材料的制备及其性能研究

用浸渍法制备了以 CeO2 为助剂的镍基乙醇水蒸气重整制氢催化剂(Ni/CeO2/γ Al2O3)。该种催化剂在较低的温度下具有较高的氢气产率和较高的CO2 选择性,并使副产物 CH4 和 CO的选择性限制在较低水平。在 600℃,催化剂 16% Ni/CeO2/γ Al2O3的氢气产率可达4.8,生成 CO2、CO和 CH4 的选择性分别为70.7%、21%和7%。     

混合导体透氧膜反应器中焦炉煤气重整制合成气的实验研究

研究了以焦炉煤气为原料在BaCo0.7Fe0.2Nb0.1O3-δ(BCFNO)透氧膜反应器中制合成气。实验结果表明,BCFNO膜反应器的自催化性能差。加入催化剂后,膜反应器的重整性能得到明显提高,在875℃,焦炉煤气中甲烷转化率为87.0%,产物中氢气和一氧化碳选择性分别为78.3%、105.6%,透氧量达到15.8ml/(cm2.min)。焦炉煤气中的甲烷在膜反应器中反应路径为首先焦炉煤气中的氢气与膜片透过去的氧反应生成水,然后甲烷再与水重整生成氢气和一氧化碳。实验过程中,透氧膜没有出现破裂,BCFNO透氧膜反应器在富氢的焦炉煤气下显示出很好的稳定性。     

Development of transition metal joint for steam generator circuit of prototype fast breeder reactor

Abstract

A transition metal joint between type 304 stainless steel and 2·25Cr–1Mo steel, with Alloy 800 as the transition piece, is being developed for application in the steam generator circuit of the 500 MW prototype fast breeder reactor. As part of this programme, the hot cracking susceptibility of Inconel 82/182 and of 16–8–2 welding consumables were compared and the microstructure and mechanical properties of butt welds between type 304 stainless steel and Alloy 800, welded by the two consumables, were studied to select the appropriate welding consumables for this joint. It is recommended that the 16–8–2 consumable should be used for welding this joint because of its lower microfissuring tendency and reduced mismatch in the coefficient of thermal expansion across the joint, although this would mean a slight adverse effect on the elevated temperature mechanical properties. Further, to select the optimum post-weld heat treatment (PWHT) of the joint between Alloy 800 and 2·25Cr–1Mo steel, welded with Inconel 82/182 welding consumables, the effect of PWHT on the microstructure and mechanical properties was studied. Decreasing the PWHT temperature was found to improve the mechanical properties and the microstructural condition of this joint.

MST/842     

蒸汽加热器结构数值优化

通过FLUENT软件对某类型的蒸汽加热器进行分析,得出影响实际换热效率的主要因素为壳程进、出口影响以及壳程不布管区的横向面积的结论,提出了具体的优化方案。     

煤油水重整制氢催化剂的优化设计

以Ni为活性组分,稀土元素La,碱金属Li和贵金属Pt为助剂完成了催化剂体系设计;采用等体积分步浸渍法和溶胶凝胶法制备催化剂。考察了助剂La,Li和Pt的作用,研究了催化剂的活性、稳定性和抗析碳性,并筛选催化剂。研究了NiLaLiPt/γ-Al2O3催化剂上煤油水重整制氢的影响因素。     

Composite nozzle dam in the steam generator of a nuclear reactor

The period of normal shutdown and maintenance for a nuclear power plant can be remarkably shortened when the examination and maintenance of the tubes of a steam generator are simultaneously carried out with refueling. The nozzle dam in a steam generator is a closure to block the flow of coolant from the inlet-outlet nozzles in a steam generator. Recently, the installation and removal operations of the nozzle dam were attempted using a robot rather than the manual operation because of the radioactive hazard. For the operation using the robot the weight of the dam must be reduced because the robot's payload for assembling operations is usually small.

In this work, a lighter nozzle dam was designed and manufactured using a carbon-epoxy composite, a glass-epoxy fabric composite, an aluminium plate and honeycomb. The carbon-epoxy composite was used for the main structural material and the honeycomb was used to increase the bending stiffness, while the aluminium plate and the glass-epoxy fabric composite were used to reduce the stress concentration around bolt holes. Also, the variation in mechanical properties of composites with respect to radiation emission was investigated.

In order to verify the structural integrity of the nozzle dam installed on the nozzle ring with bolts, the stress analyses of the nozzle dam under hydrostatic pressure were performed using commercial finite-element software and the pressure test was performed. The stiffness of the composite nozzle dam was measured and compared to that obtained by finite-element analysis.     

惰性多孔无机膜反应器用于低碳烃类选择氧化

主要介绍邓用多孔无机膜作氧气分布器的新型膜反应器－－惰性膜反应器的特点、应用和发展概况，对于低碳烃类的氧化脱氢或部分氧化，沿反应器轴向分布氧气，可以降低反应工氧气的分压，提高选择性和收率；讨论了这种新型膜反应器今后有待研究的问题。     

A study of reactor neutrino monitoring at the experimental fast reactor JOYO

We carried out a study of neutrino detection at the experimental fast reactor JOYO using a 0.76 tons gadolinium loaded liquid scintillator detector. The detector was set up on the ground level at 24.3 m from the JOYO reactor core of 140 MW thermal power. The measured neutrino event rate from reactor on-off comparison was 1.11±1.24(stat.)±0.46(syst.) events/day. Although the statistical significance of the measurement was not enough, backgrounds in such a compact detector at the ground level were studied in detail and MC simulations were found to describe the data well. A study for improvement of the detector for future such experiments is also shown.     

充气膜结构零应力态求解

充气薄膜管属于柔性结构,荷载作用下产生的变形,会引起其内压改变,进而导致外围薄膜刚度的变化,对其变形产生重要影响,表现出内充气体压力与外围薄膜变形相互耦合的特点。该文采用有限元方法分析气-膜耦合作用对充气薄膜管动力特性的影响及其随影响因素的变化规律。通过将内充气体看作小扰动线性势流以考虑气-膜耦合作用以及内充气体附加质量的影响;通过建立内充气体的三种等效模型,分别将内充气体作用等效为外围薄膜静力边界条件、考虑内充气体附加质量影响的静力边界条件以及小扰动线性势流体,并将其相应的有限元分析结果进行对比,研究气-膜耦合作用和内充气体附加质量对充气薄膜管自振特性的影响及其随初始内压、长细比、膜厚以及端部约束类型的变化规律。研究结果表明：气-膜耦合作用以及内充气体的附加质量对低阶自振模态没有明显影响;气-膜耦合作用对自振频率有较显著的影响作用,而内充气体附加质量的影响则较小;随初始内压和长细比的增加,气-膜耦合作用对频率的影响体现出因阶次不同而不同的变化规律;气-膜耦合作用对频率的影响随膜厚的增加而降低,随约束程度的减弱而增强。该文的研究成果揭示了气-膜耦合作用对充气薄膜管自振特性的影响规律,有助于深入认识充气薄膜管的动力行为,确保其设计计算的合理性和可靠性。     

A modified Benedict-Webb-Rubin equation of state for methane using recent experimental data

A 33 term modified Benedict-Webb-Rubin equation of state is presented for methane. The adjustable parameters in the equation of state have been estimated using recent experimental data and least squares techniques which include the thermodynamic equilibrium conditions for the co-existing liquid and vapour phases. Comparisons of the new equation of state and an older modified Benedict-Webb-Rubin equation of state to experimental data are given.     

膜混凝反应器除砷

用国产中空纤维膜组件,研究膜混凝反应器小试规模条件下的除砷效果.结果表明:膜混凝反应器的除砷效果良好,砷的去除率高达92.8%～98.2%,可使原水中As(V)的浓度从100 μg/L左右降至10μg/L以下,出水平均舍砷4.40μg/L,完全满足城市供水水质标准的要求;膜污染是导致膜比通量下降的主要原因,铁盐对膜污染的贡献较小,膜污染主要是有机物污染,占总量的67.2%;通过物理清洗和化学清洗可使膜比通量恢复到新膜的87.8%.