Peng-Robinson状态方程计算合氢系统汽液平衡——超临界气体的参数处理

本文修正了Peng-Robinson 状态方程,使之适用于氢烃二元系统的汽-液平衡计算.对超临界气体氢引入了新的、随温度而变的a表达式和协体积项b的二元交互作用参数.计算了19个二元系统,结果表明本研究较前人为优.尤其是对氢-重烃(C_6-C_(16)),亦优于Mathias修正的Redlich-Kwong-Soave状态方程和Chao等人最近提出的立方型转子链状态方程(CCOR状态方程).修正后的a表达式除改进了汽液平衡结果,还可准确地推算氢气的P-V-T关系和第二维里系数.本研究推荐的方法可用于实际工程计算.     

Measurement and correlation of the isobaric vapor-liquid equilibrium for mixtures of alcohol+ketone systems at atmospheric pressure

Vapor-liquid equilibrium (VLE) for binary mixtures composed of ethanol+methyl isobutyl ketone, 1-butanol+ methyl ethyl ketone, and 1-butanol+methyl propyl ketone systems was measured using a circulation type equilibrium apparatus at atmospheric pressure. The measured data and literature data for alcohol and ketone systems have been correlated by the UNIversal Quasi-Chemical (UNIQUAC) model with two binary interaction parameters and the non-random lattice fluid equation of state with hydrogen bonding equation of state (NLF-HB EoS) using a single binary interaction parameter. For the NLF-HB EoS calculations, the numbers of proton acceptor for ketones were adjusted between 0 and 1. The calculation results with the NLF-HB EoS are better than those with the UNIQUAC model.     

A generalized correlation for the prediction of phase behaviour in supercritical systems

A generalized two parameter model is presented which uses molecular properties of pure fluids to predict interaction parameters in the attractive term of the Peng-Robinson equation of state. The predictive method is based on a consideration of London (dispersive) forces and includes attractive forces between polar and non-polar molecules that result from induction. Polar-polar effects and quantum forces are omitted. A large body of experimental vapor-liquid equilibrium data measured at near and supercritical conditions (that excludes quantum components and polar-polar systems) was used to calibrate the generalized model. Overall bubble point pressure deviations calculated using the proposed generalization were 5.66% for 3240 data points which compares to average deviations of 3.27% obtained by using regressed binary interaction parameters. Average vapor mole fraction deviations were just under 0.01 using both the generalized and the regressed interaction parameters. The sensitivity of predicted phase envelopes to dispersive and inductive term in the generalized correlation is shown graphically for several systems. Comparisons are also made to another recent interaction parameter generalization presented by Nishiumi et al. (1988).     

Volumetric expansion and vapour–liquid equilibria of α-methylstyrene and cumene with carbon dioxide at elevated pressure

Volumetric expansion data and vapour-liquid equilibria (VLE) for α-methylstyrene (AMS) with CO₂ are reported at temperatures of 308 and 323 K and pressures approaching the mixture critical point. Similar data are reported for the mixture of carbon dioxide and cumene at a temperature of 323 K. It is shown that the volumetric expansion data for the various systems coincide when plotted as a function of the solubility of CO₂ in the liquid phase. A procedure is described for calculating the molar volume of the liquid phase from the phase compositions and volumetric expansion data. The experimental VLE data are correlated with the Peng-Robinson (PR) equation of state and the interaction parameter for each binary system is obtained by regression. The interaction parameter is subsequently used to predict the liquid molar volume for each binary system. The use of a single interaction parameter with the PR equation of state provides a satisfactory correlation of the liquid molar volume.     

A multi-fluid nonrandom lattice fluid model: Mixtures

A multi-fluid nonrandom lattice fluid model with no temperature dependence of close packed volumes of a mer, segment numbers and energy parameters of pure systems and its consistent method for phase equilibrium calculation were presented in the previous paper. In this work, the model was extended to mixtures by using consistent method for phase equilibrium calculation with fugacity coefficients derived from the present equation of state and it was applied to vapor-liquid equilibrium. We consistently tested the present model on 17 phase equilibrium data sets of vapor-liquid equilibria and compared it with the MF-NLF model and the SAFT model. The present model (3 pure parameters for pure component and one binary interaction parameter) showed better results for most systems than the MF-NLF model (6 adjustable pure parameters and one binary interaction parameter) and the SAFT model (3 pure parameters and one binary interaction parameter).     

EOS状态下基于多相流有规栅格理论的水-碳氢化合物两相体系的临界轨迹关系

Quantitative representation of complicated behavior of fluid mixtures in the critical region by any of equation-of-state theories remains as a difficults thermodynamic topics to date.In the present work,a computational efforts were made for representing various types of critical loci of binary water with hydrocarbon systems showing Type Ⅱ and Type Ⅲ phase behavior by an elementary equation of state[called multi-fluid nonrandom lattice fluid EOS(MF-NLF EOS)]based on the lattice statistical mechanical theory.The model EOS requires two molecular parameters which representing molecular size and interaction energy for a pure component and single adjustable interaction energy parameter for binary mixtures.Critical temperature and pressure data were used to obtain molecular size parameter and vapor pressure data were used to obtain interaction energy parameter.The MF-NLF EOS model adapted in the present study correlated quantitatively well the critical loci of various binary water with hydrocarbon systems.     

The prediction of the ternary liquid-liquid equilibrium by means of the NRTL-equation

The prediction of ternary liquid-liquid equilibria by means of the NRTL-equation and using the parameters obtained by the correlation of the limiting binary systems is examined. The predicted data are compared with experimental data for systems composed of an aromatic and an aliphatic hydrocarbon and sulpholane. The number of sets of binary parameters obtained from the correlation of the binary systems is infinite. For any value of the non-randomness parameter a corresponding pair of energy parameters can be determined, giving rise to a set fitting the data equally well. Limits to the value of the parameters can only vaguely be determined on the basis of their physical meaning. The upper limit of the non-randomness parameter related to the heterogeneous binary system is more precisely defined. Some general conclusions for the selection of the parameters could be reached. The predicted heterogeneous area is in general too large but decreases with increasing values of the non-randomness parameter of the heterogeneous binary system. The value of the parameters of the homogeneous binary system has only a small influence on the position of the binodal. The slope of the tie lines is mainly determined by the non-ideality of the homogeneous binary systems.     

Vapor-liquid equilibrium correlations for systems containing amines using a lattice fluid equation of state with hydrogen bonding

The nonrandom lattice equation of state with hydrogen bonding (NLF-HB EOS) was examined for the correlation of vapor-liquid equilibria (VLE) for binary amine and hydrocarbon mixture at various temperatures. For these mixtures, the consideration of hydrogen bondings in the lattice equation of state clearly improves the prediction for VLE. The amines were divided into four groups due to the different strength of the hydrogen bonding. For all groups, different hydrogen bonding parameters were obtained and evaluated. The effects of varying hydrogen bonding energies for NLF-HB EOS are discussed. For systems containing lower amines, the NLF-HB EOS showed excellent agreement with the experimental data. For the correlation of systems containing tertiary amine molecules, binary interaction parameter had to be involved instead of hydrogen bonding parameters.     

用FRKS状态方程关联高度非对称二元系超额焓

引言对于组分分子大小、形状、结构相差较大的高度非对称混合物,迄今仍未有计算其超额焓的满意的方法．最近Lin等用转子链立方状态方程计算了高度非对称二元系的超额焓．在他们的工作中,使用两个可调参数虽然明显改进了计算,但对大多数体系,误差仍较大．对于这一类体系,立方状态方程失败的两个主要原因是：一、对于纯物质,立方状态方程中的引力参数α通常表为温度T和偏心因子ω的函数．对于复杂化合物,特别是长链碳氢化合物,由于其性质偏离正常流体较远,偏心因子已不可靠,另外,对于高沸点物质,也难以得到可靠的ω数值;因此,…     

A modification of Wong-Sandler mixing rule for the prediction of vapor-liquid equilibria in binary asymmetric systems

Systems consisting of light components and heavy hydrocarbons are highly asymmetric and industrially important. Design and control of facilities for separation and purification of such mixtures require vapor-liquid equilibrium data. Coupling of the cubic equation of state (EOS) with excess Gibbs energy models (EOS/G ^ex models) failed to represent the vapor-liquid equilibria (VLE) of such systems accurately. The main purpose of this work is to present a modification of Wong-Sandler mixing rule with using the composition dependent binary interaction parameter. Vaporliquid equilibria for 30 binary systems are calculated using the SRK equation of state with proposed model and Wong-Sandler mixing rule. Calculated pressures and mole fractions of vapor phase are compared with experimental data. The average absolute percentage deviation indicates that error involved in the application of modified Wong-Sandler model is less than Wong-Sandler model in most cases.     

热力学状态方程二元交互作用参数估算模型开发

基于气液平衡理论,建立了热力学状态方程二元交互作用参数估算模型。首先,结合气液平衡理论、状态方程以及相应的混合规则建立气液相平衡数学模型;然后以气相组成误差平方和与压力相对误差平方和之和作为目标函数,并使用计算机编程,利用单纯形法进行优化求解,实现了热力学状态方程二元交互作用参数估算模型的开发;最后,用该模型对5组二元气液平衡体系中的组分二元交互作用参数进行估算,并根据估算出的参数对各体系的气相组成进行预测,结果显示,预测值与实验值的平均相对偏差均小于1％,表明该模型计算结果准确,可应用于气液平衡计算中。     

氨—氢—氮—甲烷混合物气液平衡预测

利用改进的Ｌ－Ｌ二元互作用函数结合简单的ＲＫＳ立方状态方程关联氨－氢－甲烷混合物的６个组分二元系的相平衡实验数据,得到各组分二元系的二元系作用函数的各参数值,后者用来预测该混合物的气液平衡,预测结果和实验值吻合较好。     

Prediction of Hydrate Phase Equilibria in Aqueous Solutions of Salt and Organic Inhibitor Using a Combined Equation of State and Activity Coefficient‐Based Model

A thermodynamic model based on combination of the Valderrama modification of the Patel‐Teja equation of state with non‐density dependent mixing rules and a modification of a Debye‐Hückel electrostatic term is extended to systems containing salt and organic inhibitor by correcting the properties of the aqueous phase such as dielectric constant, density and molecular weight. A linear mixing rule is used for determining the dielectric constant of salt‐free mixture by introducing an interaction parameter (in dielectric constant mixing rule), which is tuned using the freezing point data of aqueous solutions containing salt and organic inhibitor. The binary interaction parameter between salt and organic inhibitor is adjusted using water vapour pressure data in the presence of salt and organic inhibitor. The predicted hydrate dissociation conditions are in acceptable agreement with the experimental data, demonstrating the reliability of the model developed in this work.     

Measurement of excess enthalpies using a high-pressure flow microcalorimeter and determination of binary interaction parameters for thermodynamic models

While an equation of state (EOS) plays a critical role in estimating thermodynamic properties, employing it in the determination of binary interaction parameters is extremely important. In general, these parameters can be determined from phase equilibrium data. However, data collection from experiments is a time-consuming and tedious process. In this study, after measuring the excess enthalpies of binary systems containing CO₂ by high-pressure flow isothermal microcalorimetry (IMC), we determined the EOS binary interaction parameters, specifically, the Peng-Robinson EOS binary interaction parameters. These binary interaction parameters obtained by IMC were compared with those obtained by vapor-liquid equilibrium (VLE) experiments. Hence, high-pressure flow IMC appears to be an effective method for the determination of interaction parameters that are used in the estimation of thermodynamic properties. Further, the Flory-Huggins interaction parameters of a binary mixture CO₂ containing with various mole compositions were also estimated by employing high-pressure IMC.     

Correlation of K-factors for mixtures of hydrogen and heavy hydrocarbons

K-factors for hydrogen-heavy hydrocarbon mixtures are becoming increasingly important in new industrial applications, particularly in coal liquefaction. When equations of state such as Soave's are used to fit hydrogen-heavy hydrocarbon binary data, unrealistic binary interaction parameters k_ij are required because equilibrium ratios are not sensitive to k_ij for highly asymmetric binary systems containing a highly supercritical component.Reliable representation of experimental results can be obtained by modifying the composition dependence of the covolume parameter b for the mixture. The modification introduces a binary parameter E_Hj which has a physically reasonable size. Upon adjusting E_Hj to fit the binary data (setting k_ij = 0), good results are obtained for seven hydrogen-heavy hydrocarbon binaries.     

Thermodynamic modeling of vapor-liquid equilibrium of binary systems ionic liquid + supercritical {CO2 or CHF3} and ionic liquid + hydrocarbons using Peng-Robinson equation of state

Vapor-liquid equilibrium (VLE) data from literature for binary systems involving several ionic liquids were correlated. The Peng-Robinson equation of state, coupled with the van der Waals and Wong-Sandler mixing rules, was used as the thermodynamic model to evaluate the fugacity coefficients. The UNIQUAC and NRTL models were used to calculate the excess Gibbs free energy in the Wong-Sandler mixing rule. A molecular modeling strategy using the software ChemOffice was used to calculate the volume and surface area parameters of ionic liquids for UNIQUAC, while the binary interaction energy parameters for UNIQUAC and NRTL models, as well as the binary interaction parameter of the van der Waals and Wong-Sandler mixing rules were estimated through a method based on the genetic algorithm. The results show that, as expected, the Wong-Sandler mixing rules represented better the data, with both activity coefficient models showing high accuracy. However, in one case, NRTL predicted an erroneous azeotropic condition, while UNIQUAC was able to correlate the data without this error.     

应用正规溶液理论计算含水体系液液平衡

本文在正规溶液理论基础上，考虑了混合熵效应和长程静电作用，提出了可用于各种含水体系液液平衡计算的普遍方程，以及分子间作用参数与温度的关系式，关联了具有上会溶温度、下会溶温度和两者同时存在的有机物－水体系的液液平衡数据。该普遍方程可用于含水、有机物和（或）电解质的二元及三元体系液液平衡计算。     

A GE/Equation of State Mixing Rule for Vapor-Liquid Equilibria

A new excess Gibbs free energy/equation of state type mixing 0rule was derived byremoving the infinite pressure boundary condition imposed by Wong and Sandler.The mixing rulewas extensively tested in terms of a comprehensive data base,consisting of 52 simple nonpolar-nonpolar,carbon dioxide containing,hydrocarbon-hydrocarbon,CFC,polar-polar,nonpolar-polarbinary and multicomponent systems.Focused on the complete predictive capability,a comparisonbetween the Wong-Sandler and the mixing rule proposed was conducted.The results indicate that thenew mixing rule is in general superior to the Wong-Sandler's,and the binary interaction parameteras required by the latter is removed,which reduces computing effort and is reliable in predictions ofvapor-liquid equilibria from low pressures to high pressures.     

On the predictive capabilities of CPA for applications in the chemical industry: Multicomponent mixtures containing methyl-methacrylate,dimethyl-ether or acetic acid

The predictive performance of the CPA (Cubic-Plus-Association) equation of state for applications relevant to the chemical industry is illustrated in this work. Three such applications inspired by industrial requests/interest are illustrated here, all of which involve aqueous multicomponent mixtures exhibiting vapor–liquid (VLE) and/or liquid–liquid (LLE) equilibrium. The first two cases include mixtures of methyl-methacrylate with acetone or methanol and dimethyl-ether with ethanol, respectively. In these two cases, the classical form of CPA is used. The third case involves aqueous mixtures with acetic acid, esters, ethers and alcohols, and in this case for water–acetic acid the CPA-Huron Vidal (CPA-HV) version of the model is used. For the latter binary mixture, new CPA-HV binary parameter sets are estimated using, among others, data for activity coefficients at infinite dilutions. The modeling approach is similar in all three cases, i.e. the binary parameters are solely fitted to binary data and thus all multicomponent calculations are considered predictions.It is shown that CPA correlations for binary systems are excellent in all cases using temperature independent parameters except for the acetic acid–water system for which different parameter sets at different temperatures can be recommended. Even with the use of CPA-HV mixing rules, modeling of the acetic acid–water system with few interaction parameters remains a challenging task. Excellent simultaneous VLE and LLE correlation is obtained for complex systems such as aqueous mixtures with ethers and esters. The multicomponent results are, with a few exceptions, very satisfactory, especially for the vapor–liquid equilibrium cases. For the demanding aqueous acetic acid–water containing systems, one parameter set is recommended at the end for modeling ternary or multicomponent mixtures containing acetic acid and water.