合金组元过量焓与真空蒸馏气液相平衡的关联

基于Wilson方程，通过组元的摩尔体积和无限稀偏摩尔过量焓获得Wilson方程的相互作用参数，预测了Sn-X（X=Bi, Cd, Ga, Ge, In, Pb, 和 Sb）体系在5 Pa时的VLE（气-液平衡）相图。结果表明预测值与实验数据具有很好的一致性，在缺乏组元活度的情况下，该方法可以有效预测合金真空蒸馏的气液平衡，为粗金属的真空分离与提纯提供理论指导。     

Densification,mechanical and thermal properties of ZrC1 − x ceramics fabricated by two-step reactive hot pressing of ZrC and ZrH2 powders

Densification behavior, mechanical and thermal properties of ZrC_1 ? x ceramics with various C/Zr ratios of 0.6–1.0 have been investigated by two-step reactive hot pressing of ZrC and ZrH₂ powders at 30 MPa and 1500–2100 °C. The two-step reactive hot pressed ZrC_1 ? x ceramic has a higher relative density (> 95.3%) than that (91.9%) of stoichiometric ZrC sintered at 2100 °C. A cubic Zr₂C-type ordered phase forms in the ZrC_1 ? x sample obtained at a ZrC/ZrH₂ molar ratio of 0.6 at a relatively low temperature of 1100 °C. The decrease in C/Zr ratio is beneficial to densification of ZrC_1 ? x ceramic, however, excess grain growth occurs after sintering above densification temperature. The elastic modulus and Vickers hardness decrease with decreasing the C/Zr ratio. With decreasing the C/Zr ratio, both thermal conductivity and specific heat decrease due to the enhanced scattering of conducting phonons and electrons by carbon vacancies.     

Inherent safer design for chemical process of 1,4-dioldiacetate-2-butene oxidized by ozone

Abstract

Oxidation reaction is the typical thermal runaway reaction, and the reaction of 1, 4-dioldiacetate-2-Butene oxidized by ozone was investigated in this study. Firstly, the thermal hazards of the oxidative exothermic reactions were identified and evaluated combined process risk assessment method. The Qualitative Assessment for Inherently Safer Design (QAISD) was used to identify the risk of the reaction process. Meanwhile, the Reaction Calorimeter (RC1^e) was used to obtain the thermal properties of the oxidation reaction. Then the inherent safer designs (ISD) were proposed according to the risk assessment results to increase the level of safety of chemical industry technique. 1) ISD I: reaction temperature was improved to –5?°C, and ventilation rate was improved to 200?L?h^?1. 2) ISDII: using a tubular reactor as reaction vessel. The results indicated that the severity of the reaction hazard was reduced by 43%, and safety was improved significantly via two ISDs. Moreover, the inherent safety level of the reaction was increased by 63% and 43.4% via ISD Iand II, respectively. The reaction process get closer to inherent safety theories of “minimize,” “substitute,” and “moderate”.     

Properties of alkali activated slag–fly ash blends with limestone addition

In this article, the effects of raw materials’ composition on fresh behavior, reaction kinetics, mechanical properties and microstructure of alkali activated slag–fly ash–limestone blends are investigated. The results indicate that, with the increasing content of fly ash and limestone, the slump flow increases. The setting times are shortened when increasing the slag content, while both fly ash and limestone show a negligible influence. The reaction process is slightly accelerated by the presence of limestone due to the extra provided nucleation sites, but the reaction process is mainly governed by the slag. The slag content exhibits a dominant role on strength in this ternary system, while for a constant slag content, the compressive strength increases with the increasing limestone content up to 30%. The microstructure analysis shows that the gel characteristics are independent of the limestone powder content. The presence of limestone in initially high Ca and Al conditions does not lead to the formation of additional crystalline phases, which is different from Portland cement systems. Both physically and chemically bound water contents are slightly increased when limestone powder is incorporated.     

碱度对包钢高炉渣物理性能的影响

摘要：为探明二元碱度对包钢高炉渣物理性能的影响机理，基于包钢7号高炉渣化学组成，添加纯试剂CaO、SiO2调整炉渣的二元碱度。通过实验研究二元碱度对包钢7号高炉渣熔化温度、黏度和熔化性温度的影响规律；同时采用Factsage70热力学软件，计算了不同碱度下炉渣的液相线温度和热焓值。结果表明：随着碱度升高，炉渣熔化温度不断升高，黏度和熔化性温度先降低后升高，碱度在1.1～1.3之间，碱度每提高0.1，炉渣半球温度提高4.67℃，软熔区间为3.33～4.60℃；碱度在1.1～1.4之间，1450℃以上炉渣黏度均低于0.5Pa·s，流动性良好；Factsage7.0计算结果表明：随着碱度的升高，炉渣的液相线温度不断升高，热焓值不断降低。综合考虑碱度对包钢炉渣熔化温度、熔化性温度、热焓和黏度的影响规律，建议包钢高炉渣的碱度应控制在1.1～1.3之间。     

压水堆核电厂一回路首次钝化工艺研究

压水堆核电厂热态功能试验中的一回路首次钝化对核电厂一回路材料腐蚀控制和减少腐蚀产物等方面具有重要作用。本文结合理论研究与工程实际情况，提出了在热态功能试验过程中钝化膜的生成包含电化学反应和化学反应的观点，阐述了双层膜的生长机理，解释了用电化学测试方法分析钝化工艺过程的合理性，推导出钝化温度与钝化膜反应速率的函数关系式，钝化温度升高，反应速率升高，钝化时间缩短；明确了钝化工艺温度的理论限值应不低于260℃。      

Hydrogen production from thermal decomposition of ammonia-contaminated acid gas using a detailed reaction mechanism

The increase in the production of acid gas consisting of H₂S, CO₂, and associated impurities such as ammonia and hydrocarbons from oil and gas plants and gasification facilities has stimulated the interest in the development of alternative means of acid gas utilization to produce hydrogen and sulfur, simultaneously. The present literature lacks a detailed reaction mechanism that can reliably predict the thermal destruction of NH₃ and its blend with H₂S and CO₂ to facilitate process optimization and commercialization. In this paper, a detailed mechanism of NH₃ pyrolysis is developed and is merged with the reactions of NH₃ oxidation and H₂S/CO₂ thermal decomposition from our previous works. The mechanism is validated successfully using different sets of experimental data on the pyrolysis and oxidation of NH₃, H₂S, and CO₂. The proposed mechanism predicts the experimental data on NH₃ pyrolysis remarkably better than the existing mechanisms in the literature. The mechanism is used to investigate the effects of NH₃ concentration (0–20%) and reactor temperature (1000–1800 K) on the thermal decomposition of H₂S and CO₂. A synergistic effect is observed in the simultaneous decomposition of NH₃ and CO₂, i.e., NH₃ conversion is improved in the presence of CO₂ and the decomposition CO₂ to CO is enhanced in the presence of NH₃. The presence of H₂S suppressed NH₃ conversion, while the conversion of H₂S remained unchanged with increasing NH₃ concentration at temperature below 1400 K due to the low conversion of NH₃ (up to 18%). At temperature above 1400 K, NH₃ conversion increased rapidly and it triggered a decrease in H₂S conversion as well as the yields of H₂ and S₂. The major reactions involved in the decomposition of H₂S, CO₂, and NH₃ and the production of major products such as H₂, S₂, and CO are identified. The detailed reaction mechanism can facilitate the design and optimization of acid gas thermal decomposition to produce hydrogen and sulfur, simultaneously.     

Comprehensive numerical study of molecular diffusion effects and Eddy Dissipation Concept model in MILD combustion

Moderate or Intense Low-oxygen Dilution (MILD) combustion is a clean combustion technology with high thermal efficiency and low levels of emissions. In this paper, by employing Adelaide Jet-in-Hot-Co-flow (AJHC), several approaches are examined to increase the numerical solution accuracy. First, molecular diffusion effects are investigated in MILD combustion. Second, adjusting the Eddy Dissipation Concept (EDC) coefficients is comprehensively discussed, and finally, the reaction fraction coefficient and EDC formulation are investigated. The results show that the effect of enthalpy transport caused by molecular diffusion on the energy equation must be considered in the low oxygen concentration regions. Also, the maximum temperature in the MILD region can be kept constant by adjusting EDC coefficients. Furthermore, it is shown that applying the reaction fraction factor increases the accuracy of the numerical solution in the MILD region.     

Gasification of biomass model compounds in supercritical water: Detailed reaction pathways and mechanisms

Supercritical water gasification (SCWG) technology is an efficient and clean method to utilize biomass wastes. But the real biomass is complicated, bringing difficulties for the research of reaction pathway. In this paper, xylose was selected as a model compound for hemicellulose and the experiment was conducted in quartz reactors. The degradation pathway of xylose in supercritical water (SCW) was discussed. The main intermediates included phenols, furans, arenes, organic acids, ketones and alcohols. Phenols and arenes were difficult to be gasified while furans, organic acids, ketones and alcohols could be easily gasified. The degradation pathways of glucose and guaiacol as model compounds for cellulose and lignin in SCW have also been discussed in previous studies. By comparing the experimental data, it is found that guaiacol was more difficult to be gasified than glucose and xylose. The main organics in residual liquid of xylose and glucose were furans, cyclic ketones, open-chain compounds, phenols and arenes while that of guaiacol were phenols, arenes and open-chain compounds. The degradation of phenols and arenes was the key step of SCWG of biomass model compounds.     

Hydrogen sorption properties of V85Ni15

An alloy with nominal composition V₈₅Ni₁₅ was prepared in a vacuum induction melting apparatus. The chemical analysis of the sample showed a V (Ni) content of 82.63 (15.68) at% and small contaminations by carbon and aluminum. XRD measurements confirmed that the bcc Ni-V solid solution phase is the main constituent of the sample. However, a minor impurity (approximately 6.5 wt%) due to the precipitation of the sigma NiV_3-x phase is present in the sample.Hydrogen sorption measurements extending from 150 °C up to 400 °C in a wide pressure range (up to 90 bar) were performed. Upon hydrogenation below 250 °C, one observes the subsequent presence of an α phase and of two hydride phases with different values of dehydrogenation enthalpy: ΔH_dehydr = 21 ± 1 kJ/mol for 0.15 ≤ H/M ≤ 0.30 and ΔH_dehydr = 26 ± 2 kJ/mol for 0.53 ≤ H/M ≤ 0.59. Above 300 °C, there is no evidence of the formation of hydrides and only an α phase is present up to the maximum measured composition, with a hydrogenation enthalpy ΔH_hydr = 10.0 ± 0.5 kJ/mol.