Flash-point prediction for binary partially miscible mixtures of flammable solvents

Flash point is the most important variable used to characterize fire and explosion hazard of liquids. Herein, partially miscible mixtures are presented within the context of liquid-liquid extraction processes. This paper describes development of a model for predicting the flash point of binary partially miscible mixtures of flammable solvents. To confirm the predictive efficacy of the derived flash points, the model was verified by comparing the predicted values with the experimental data for the studied mixtures: methanol+octane; methanol+decane; acetone+decane; methanol+2,2,4-trimethylpentane; and, ethanol+tetradecane. Our results reveal that immiscibility in the two liquid phases should not be ignored in the prediction of flash point. Overall, the predictive results of this proposed model describe the experimental data well. Based on this evidence, therefore, it appears reasonable to suggest potential application for our model in assessment of fire and explosion hazards, and development of inherently safer designs for chemical processes containing binary partially miscible mixtures of flammable solvents.     

A non-ideal model for predicting the effect of dissolved salt on the flash point of solvent mixtures

Flash point is one of the major quantities used to characterize the fire and explosion hazard of liquids. Herein, a liquid with dissolved salt is presented in a salt-distillation process for separating close-boiling or azeotropic systems. The addition of salts to a liquid may reduce fire and explosion hazard. In this study, we have modified a previously proposed model for predicting the flash point of miscible mixtures to extend its application to solvent/salt mixtures. This modified model was verified by comparison with the experimental data for organic solvent/salt and aqueous-organic solvent/salt mixtures to confirm its efficacy in terms of prediction of the flash points of these mixtures. The experimental results confirm marked increases in liquid flash point increment with addition of inorganic salts relative to supplementation with equivalent quantities of water. Based on this evidence, it appears reasonable to suggest potential application for the model in assessment of the fire and explosion hazard for solvent/salt mixtures and, further, that addition of inorganic salts may prove useful for hazard reduction in flammable liquids.     

The prediction of the flash point for binary aqueous-organic solutions

A mathematical model, which may be used for predicting the flash point of aqueous-organic solutions, has been proposed and subsequently verified by experimentally-derived data. The results reveal that this model is able to precisely predict the flash point over the entire composition range of binary aqueous-organic solutions by way of utilizing the flash point data pertaining to the flammable component. The derivative of flash point with respect to composition (solution composition effect upon flash point) can be applied to process safety design/operation in order to identify as to whether the dilution of a flammable liquid solution with water is effective in reducing the fire and explosion hazard of the solution at a specified composition. Such a derivative equation was thus derived based upon the flash point prediction model referred to above and then verified by the application of experimentally-derived data.     

Liquid immiscibility in ternary metallic alloys

Abstract

Two models have been proposed which can be used to predict the occurrence of liquid immiscibility in ternary metallic alloys. One model, derived from an earlier proposal by Axon for predicting liquid immiscibility in binary alloys, was based on differences in the atomic sizes and melting points of the metals. The second model, based on a proposal made by Mott (from the binary metallic liquid immiscibility rule of Hildebrand and Scott), utilises solubility parameters and electronegativities as the determinants. The models were tested against the known behaviour of 27 metallic ternary systems which show liquid immiscibility and 36 systems which show either complete liquid miscibility or only a small region of liquid immiscibility confined to a region adjacent to an immiscible binary system. Both models showed good predictive ability when applied to the first group of 27 systems, but the first model proved to be superior when applied to the 36 miscible liquid systems. The behaviour of the liquid phase was always predicted correctly by one or other of the models in all the ternary systems examined.

MST/1412     

HFCs混合制冷剂热力性质的研究

为了利用PR方程和Huron-Vidal混合规则对三元混合制冷剂的热力性质进行精确计算,通过对10组二元HFCs混合制冷剂的汽液相平衡实验数据进行热力学关联,得出了相应的NRTL模型参数,由优选得到的过量Gibbs自由能NRTL模型的相互作用系数预测了构成R407C和R404A的三元混合制冷剂R32／R125／R134a以及R125／R143a／R134a的汽液相平衡,结果表明,泡点压力实验值和计算值的算术平均相对偏差小于0．42％,各组分的汽相组成实验值和计算值基本吻合。最后还应用相关热力性质分别对R32／R125和R407C进行了理论制冷循环分析计算并和其他模型的计算结果进行了比较。     

An extended corresponding-states model for predicting thermodynamic properties of N2-Ar-O2 mixtures including vapor-liquid equilibrium

A formulation developed previously for the prediction of the thermodynamic properties of single-phase states of binary and ternary mixtures in the nitrogen-argon-oxygen system has been revised to include the calculation of vapor-liquid equilibrium (VLE) properties. The model is based on the theory of extended corresponding states with van der Waals mixing rules. Binary interaction parameters have been determined with single-phaseP-p-T and vaporliquid equilibrium data to improve the accuracy of thermodynamic property predictions. The model accurately represents single-phase and vapor-liquid equilibrium properties over a wide range of compositions for binary and ternary mixtures. Comparisons of calculated properties to selected mixture data for both single-phase and VLE states are included.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Predicting the virial coefficients and thermodynamic properties of a multicomponent mixture with application to the ternary mixture of CH2F2+CF3CHF2+CF3CH2F

A model for estimating second and third virial coefficients, which has been used successfully to represent the behavior of pure gases and binary mixtures, was applied to a ternary mixture. An estimate for the ternary third virial coefficient.C ₁₂₃, was added to the model. Three experimentally determined binary interaction parameters were also used. The model has been applied to the ternary mixture CH₂F₂+CF₃CHF₂+CF₃CH₂F (R32+R125+R134a). The results are useful for calculating gas-phase densities, thermodynamic properties, and fugacities for phase equilibrium calculations. The use of such models leads to a considerable economy of effort in the case of multicomponent mixtures. Examples of the thermodynamic properties are given for the equimolar ternary mixture in the range from the dew-point temperature to 400 K at pressures of 0.5, 1, and 2 MPa. Calculated densities and speeds of sound are compared with new experimental values for a near-equimolar composition.     

The electrochemical corrosion and passivation behaviour of Monel (400) in concentrated acids and their mixtures

The electrochemical polarisation behviour of Monel (400) in different compositions of binary and ternary solution mixtures of concentrated phosphoric, sulphuric, formic and acetic acids has been studied by potentiostatic polarisation technique at 25°C. The cathodic polarisation curves are almost linear and similar in all the binary and ternary solution mixtures and cathodic reaction is hydrogen evolution. The anodic polarisation curves reveal active, passive and transpassive behaviour in all the solution mixtures. The magnitude of the critical current density (i _c) and passivity current density (i _p) is higher in binary solution mixtures of phosphoric-formic acid than binary solution mixtures of either phosphoric-acetic acid or phosphoric-sulphuric acid. In the ternary solution mixtures of phosphoric-sulphuric-formic acids and phosphoric-sulphuric-acetic acids, the passivity is improved in comparison to their binary solution mixtures. Addition of sulphuric acid is found to improve the passivity in case of ternary solution mixtures. The effect of temperature on polarisation behvaiour of Monel (400) in a selected composition of solution mixture (60% H₃PO₄ + 4% H₂SO₄ + 36% HCOOH) has been studied at 25, 37, 45 and 56°C. Higher temperature increased the corrosion and enhanced the surface reflection. The stability of the passive film formed on the surface of the alloy has been examined by current decay method. Examination of the surface of working electrode, after polarisation studies was done using scanning electron microscopy (SEM) and atomic force microscopy (AFM) in contact mode.     

Phase behaviour and microstructure of partially-miscible, glass-forming, alcohol-water-maltotriose mixtures

The miscibility, occurrence of glass formation, and microstructure of maltotriose mixtures with water, methanol, ethanol, propan-1-ol and butan-1-ol at 20°C were studied. Maltotriose is fully miscible with water, but in binary mixtures, it is only partially miscible with short-chain alcohols. In methanol mixtures, the maltotriose-rich phase is a highly viscous liquid, but it is glassy in ethanol, propan-1-ol and butan-1-ol mixtures. In ternary alcohol-water-maltotriose mixtures, increasing water content increased miscibility, resulting in the progressive transformation of two phase liquid-glass mixtures into low viscosity single phase solutions. At water contents below about 4% w/w, the state diagram of ethanol-water-maltotriose mixtures includes a region of liquid-glass coexistence. Quenching single phase solutions into this region of the state diagram yielded aggregated dispersions of glassy particles, a process we term glassy precipitation.     

Excess Molar Volumes of the Ternary Mixture (Cyclohexane+Tetrahydrofuran+Chlorocyclohexane) and the Binary Mixtures (Cyclohexane + Tetrahydrofuran and Cyclohexane + Chlorocyclohexane) at 298.15 and 313.15 K

Densities of the ternary mixture (cyclohexane + tetrahydrofuran + chlorocyclohexane) and the binary mixtures (cyclohexane + tetrahydrofuran and cyclohexane + chlorocyclohexane) have been measured at 298.15 and 313.15 K. Excess molar volumes for the binary and ternary systems were fitted to the Redlich-Kister and Cibulka equations. Flory's theory has been used to predict excess molar volumes of binary and ternary mixtures at 298.15 K.     

基于TRIZ和类比设计的服务接触点优化应用研究

目的通过改善服务接触点构成要素之间的作用关系来优化服务接触点,提升用户体验。方法在分析服务接触内涵和服务要素的基础上,对服务接触点构成要素及其作用关系进行研究;基于类比设计,将服务接触点构成要素与TRIZ中物质—场模型进行类比分析,构建服务接触点模型;运用TRIZ中标准解求解方法对服务接触点模型进行优化。结果由服务接触点三要素(服务提供者、媒介和顾客)构建服务接触点模型,并通过标准解的应用改善了此模型,实现了对服务接触点的优化。结论通过构建服务接触点模型,结合TRIZ中物质—场分析工具和标准解的应用,为服务接触点的优化设计提供一种新的方法。以丰巢智能快递柜服务系统中的服务接触点优化设计为例,验证该方法的可行性及有效性。     

Phase equilibria in the system CaO-ZnO-B2O3 at 850°C

Phase equilibria in the system CaO-ZnO-B₂O₃ were investigated at 850°C using X-ray powder diffraction techniques. The binary phases reported previously were confirmed, but no ternary phases were found. Solid solution effects were investigated for the binary phases by comparison of the patterns, whereas for calcium oxide and zinc oxide, accurate lattice parameters were compared. No solid solutions were detected.     

Calculation of the In/Ga/P ternary phase diagram and its relation to liquid phase epitaxy

The Ga/In/P ternary phase diagram is calculated. A regular solution is assumed for binary solubility and the derived interaction parameters are used to calculate the deviation from ideality of the ternary system using a quasi-regular solution model. Comparison is made between theoretical and experimental results on liquid epitaxial layers. It is suggested that a solid/solid miscibility gap in the Ga/In/P system is a distinct possibility.     

Thermophysical properties of polymers in aqueous two-phase systems

This work concentrated on very precise density measurements of aqueous twophase systems (ATPS). The relations between density and polymer concentration of solutions of binary systems were determined experimentally at 293.15 K at concentrations ranging from 0 to 20% (w w) of polymers mostly used for ATPS: PEG, dextrans, and Reppal PES. The effect of temperature on density in the temperature range from 29?.15 to 323.15 K was determined for binary dextran 250,000 and PEG 20,000 systems. Equations that describe the relation between density and polymer concentration in polymer water binary systems were calculated and combined for predicting the density of mixtures of ternary systems. When these values were compared with measured densities of ternary polymer systems, no significant difference was found (less than 0.2%, of dextran ). A combination of density and total dry matter analysis was therefore taken as a new method for determining the composition of upper and lower phases after phase equilibria of ternary systems. Perfect agreement from tie line plotting, mass balance, and volume ratio was observed.     

分子内链段排斥性相互作用导致的聚合物共混相容体系的研究

在高分子共混物相容性研究中，人们长期持有这样一种观点：为了获得均相的高分子共混物，需要在共混组分间引入特殊相互作用，通过组分之间的相互吸引力克服相分离倾向。相容性理论和实验工作的新进展表明分子间特殊相互作用，并不是唯一的，必要的条件，存在着另一类高分子共混相容体，其中共混组分中至少含有一个或更多的无规共聚物，推动组分形成均相混合物的动力来自共聚物分子内不同单体链段的排斥性相互作用，这一新发现引起了     

Correlating Thermal-Conductivity Data for Ternary Liquid Mixtures

The performance of several semi-empirical expressions for correlating the temperature, pressure and composition dependence of the thermal conductivity (λ) of pure organic liquids and mixtures was investigated. The temperature and pressure dependence is adequately represented by Chisholm approximants of order (1, 1) or (2, 1) with five and eight adjustable constants, respectively. The fully predictive Vredeveld equation uses mass fractions as the composition variable. It significantly underestimated λ values for the R32 + R125 + R134a ternary refrigerant system. Binary predictive models with one or two adjustable parameters include the quadratic Scheffé polynomial and its corresponding Padé approximant, the cubic “Margules” model and the theoretical Wassiljewa equation. It was found that the Padé (2, 2) approximant and the Wassiljewa equation satisfactorily correlated the extensive ternary mixture data published by Rowley and coworkers. Best results were obtained when the mole fraction was used as a composition variable. The predictive capability of the models was checked using the R32 + R125 + R134a ternary refrigerant system. Combining rules were used for cross parameters such that the temperature and pressure dependence was incorporated via the pure fluid properties. Model parameters were fixed using binary data alone. In this case, the quadratic Scheffé, Padé (2, 2), and Wassiljewa (with temperature- and pressure-independent parameters) all provided satisfactory predictions for ternary mixtures.     

Effect of mixture composition on the formation of pinch points in condensers and evaporators for zeotropic refrigerant mixtures: Influence des compositions de mélanges zéotropiques sur la formation de points de pincement dans les condenseurs et les évaporateurs utilisant ces mélanges

In a recent study, it was shown by the authors that perfect glide matching of heat transfer fluid and the refrigerant is difficult in condensers and evaporators for many zeotropic mixtures and also that pinch points can occur in both the condensers and evaporators due to the non-linear variation of enthalpy during phase change. Also, a simple method was presented for predicting the occurrence of pinch points. In this paper, the influence of mixture composition on occurrence of pinch points is studied. From the thermodynamic analysis, it is shown that multi-component mixtures are preferable over many wide boiling binary mixtures for various applications from the point of view of pinch points and glide matching. The results are illustrated with a number of examples.