Coke deposition mechanism on the pores of a commercial Pt-Re/γ-Al2O3 naphtha reforming catalyst

Coke deposition mechanism on a commercial Pt-Re/γ-Al₂O₃ naphtha reforming catalyst was studied. A used catalyst that was in industrial reforming operation for 28 months, as well as the fresh catalyst of the unit were characterized using XRD, XRF, and nitrogen adsorption/desorption analyses. Carbon and sulfur contents of the fresh and the used catalysts were determined using Leco combustion analyzer. The pore size distributions (PSD) of the fresh and the used reforming catalysts were determined using BJH and Comparison Plot methods. The Comparison Plot method produced the most reasonable PSDs for the catalysts. Through comparison of the PSDs of the fresh and the used catalysts, it was revealed that coke deposited on both micropores and mesopores of the catalyst at a constant thickness of 1.0 nm. The constant coke thickness on the catalyst pore walls in the naphtha reforming process (temp. ∼ 500 °C) implies that coke deposition reaction is the slow controlling step in comparison to the fast mass transfer rate of coke ingredients into the pores. The bulk density of the deposited coke on the used catalyst was calculated as 0.966 g/cm³.     

驴肉主要营养成分及与其它畜禽肉的分析比较

本文测定了驴肉的水分、灰分、蛋白质、粗脂肪、脂肪酸、矿物元素、氨基酸的含量,并将驴肉与其他畜禽肉的营养成分作对比分析。结果表明:驴肉蛋白质含量比羊肉、牛肉、猪肉高,而脂肪含量比羊肉、牛肉、猪肉低。驴肉的氨基酸和脂肪酸组成是比较理想的,矿物元素中Fe含量明显高于其它畜禽肉。从营养学角度看,驴肉是比较理想的动物性食品原料。     

人的可靠性分析方法比较

选择了THERP、ASEPHRA、HCR、HEART、SLIM、CREAM、ATHEANA等7种常用的人的可靠性分析（HRA）方法进行比较,提出了HRA方法比较的12个标准,并用这些标准得到了HRA方法的比较结果。方法比较的标准和依据来自HRA方法的理论基础、模型、分析过程、具体实践,以及文献调研和专家判断。     

我国与国际上非化石能源发电的能量折算方法比较分析

本文对IEA、EIA、BP和联合国等主要能源统计机构的非化石能源发电统计体系进行了分析,比较了各机构非化石能源电力能量折算方法中存在的主要差异,总结了不同方法对非化石能源电力消费统计结果的影响。     

中美金属与非金属矿山安全健康标准比对分析

通过对比我国与美国金属非金属矿山安全健康标准的制定背景、标准体系结构、标准修订办法以及具体的技术指标,找出了我国与美国金属与非金属矿山安全健康标准之间的差异,并在比对的基础之上,结合我国金属非金属矿山的实际生产情况,对具有差异的指标提出了具体修改建议,为完善我国《金属非金属矿山安全规程》提供参考意见。     

轧辊光纤激光无序毛化技术:无序毛化的应用(下篇)

在连轧机、平整机、光整机上对光纤激光无序毛化轧辊与电火花毛化轧辊的过钢量,粗糙度R_a和R_(pc)值随过钢量的变化进行了对比;同时,对光纤激光无序毛化轧辊R_a=2.0~5.0μm范围内与R_(pc)值的关联情况进行了研究。结果表明:光纤激光无序毛化轧辊适用于连轧、平整、光整等工艺,其R_(pc)值高于电火花毛化辊,且R_a与R_(pc)的关联度较弱。     

中美通信塔规范自立塔等肢角钢长细比研究

通过分析对比中美通信塔规范关于自立塔等肢角钢长细比的规定,指出两者的差异,并重点对国内标准此方面的规定提出建议。     

落锤式冲击加速度标准装置的研究与建立

阐述了基于落锤式冲击加速度标准装置的结构及试验原理,基于相应的数字化仪硬件,结合虚拟仪器技术,按照ISO16063—22冲击比较法校准标准的要求设计了相应的校准软件,实现了加速度计冲击比较法校准。并且与基于Hopkinson杆的冲击激励系统产生的冲击波形进行了比较分析,通过试验数据验证了该冲击加速度标准装置的可靠性,同时对振动与冲击2种校准方式进行了比较并说明了校准结果差异的原因。     

An evaluation of empirically-based models for predicting energy performance of vapor-compression water chillers

This paper presents an evaluation of six empirically-based models for predicting water chiller energy performance using over 1000 chiller data sets from chiller manufacturers and field measurements. The data sets comprise three broad classifications, including (1) constant condenser and constant chilled water flow, (2) constant condenser and variable chilled water flow, and (3) variable condenser and variable chilled water flow. The regression parameters for each performance model are obtained using least squares method. The criteria for evaluating the predictive ability of models are based on the coefficient of variation of root-mean-square error (CV). Results show that among the six empirically-based performance models for water chillers in this study, the bi-quadratic regression model (CV = 2.2%) and the multivariate polynomial regression model (CV = 2.25%) have the best prediction accuracy for all kinds of data sets. The results of this study can be used as a reference for selecting empirically-based models for the purposes of energy analysis, performance prediction, evaluation of energy-efficiency improvements, and fault detection and diagnosis of water chillers.     

Development of large-scale hydrogen liquefaction processes from 1898 to 2009

This paper presents a review of the development of large-scale hydrogen liquefaction processes throughout the world from 1898 to 2009. First, there is a concise literature review including numerous past, present, and future designs given such as the first hydrogen liquefaction device, long time ago simple theoretical processes, today's actual plants with efficiencies 20–30%, a list of the capacity and location of every hydrogen liquefaction plant in the world, and some modern more efficient proposed conceptual plants with efficiencies 40–50%. After that, further information about the development and improvement potential of future large-scale liquid hydrogen liquefaction plants is given. It is found that every current plant is based on the pre-cooled Claude system, which is still the same as was 50 years ago with little improvement. Methods to resolve the challenges of the future plants include proposing completely new configurations and efficient systems coupled with improved efficiencies of the main system components such as compressors, expanders, and heat exchangers. Finally, a summary and comparison of the process efficiencies are described, including a newly proposed Multi-component Refrigerant (MR) system being developed by NTNU and SINTEF Energy Research AS.