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.     

Numerical simulation of influence of mass transfer on phase transfer catalytic reaction

Mass transfer with chemical reaction by liquid/liquid phase tranfer catalysis (LLPTC) for an isothermal batch reactor was analyzed. The results for the phase transfer catalyzed reaction system can be generally described by a pseudo first-order hypothesis, whereas the reaction system can be controlled by simultaneous mass transfer of the catalysts between two liquid phases and chemical reaction in the organic phase. The mass transfer limitation is mainly from the mass transfer step of QX from the organic phase to the aqueous phase. The concept of catalyst-effectiveness vs. physically meaningful parameters in a liquid/liquid phase transfer catalyzed reaction is introduced. The catalyst effectiveness is increased as the mass transfer factors increase, the ratio of reaction rate coefficients of aqueous forward reaction to organic increases, and the equilibrium constant in the aqueous solution increases.     

A MODEL FOR THE DISTRIBUTION OF ACID GASES BETWEEN AN AQUEOUS ALKANOLAMINE SOLUTION AND LPG

The model of Deshmukh and Mather (1981) is a popular method for correlating and predicting the vapor-liquid equilibria in systems containing acid gases (hydrogen sulfide and carbon dioxide) and aqueous solutions of alkanolamines. The model includes phase equilibrium between an aqueous liquid and a gas as well as chemical equilibrium in the aqueous phase. A recent review by Weiland et al. (1993) demonstrated the accuracy of the correlation. Presented here is a model based on that of Deshmukh and Mather (1981) for calculating the distribution of acid gases between two liquid phases - an aqueous phase and a non-aqueous liquid (typically a propane- or butane-rich liquid)

In the new model the phase equilibrium is modeled using a modified Henry's law approach. Fugacities of the components in the non-aqueous phase are calculated using the Peng and Robinson (1976a) equation of state. All of the parameters in the model are taken from the literature. Thus the model represents a prediction of the behavior. It is demonstrated that the predictions are in good agreement with the available experimental data     

HYDRODYNAMICS OF BUBBLE COLUMNS WITH TWO IMMISCIBLE LIQUID PHASES

An experimental study of hydrodynamic parameters of bubble columns with the presence of two immiscible liquid phases, water and kerosene, was performed. The solid used consisted of glass beads with a narrow size distribution. The analysis was based on the determination of global gas holdups and phases distribution along the length of the column in the semibatch mode of operation. The results show thai the presence of two immiscible liquid phases significantly reduces the gas holdup in the bubble column as compared to the results obtained with pure aqueous and organic liquid phases. The distribution of solid phase in a slurry bubble column is drastically affected by the presence of immiscible liquid phases, and exhibits a qualitatively different behavior when compared lo systems with one liquid phase. The addition of small amounts of aqueous phase to a slurry bubble column in which the liquid phase is kerosene results in the sedimentation of the solid. As the amount of aqueous phase added is increased, the solid fluidizes yielding almost flat concentration profiles.     

Predictions of moisture removal efficiencies for packed-bed dehumidification systems

Liquid desiccant-based dehumidification systems have been widely used to remove water vapour from air in a packed column using different liquid desiccants. The liquid desiccants are usually grouped into two categories: aqueous solutions of inorganic salts and aqueous solutions of organic compounds. In order to design such a desiccant—dehumidification system, correlations of the column performance parameters are necessary. A correlation of column efficiency for different packings and desiccant solutions was developed in this study using lithium chloride (LiCl) as the inorganic salt and triethylene glycol (TEG) as the organic compound. This correlation involves the air and liquid flow rates, air and liquid inlet temperatures, column and packing dimensions, and the equilibrium properties of the desiccant solutions. The correlation was tested for polypropylene Flexi rings, ceramic Berl saddles, glass Raschig rings and polypropylene Pall rings. The average value of the errors between predicted values and experimental data was about 7%.     

Linear relationships for modeling CO2 absorption in aqueous alkanolamine solutions in a thermodynamically consistent way

A thermodynamically consistent model for the carbon dioxide (CO₂) absorption in aqueous alkanolamine system is of great importance in the research and development of a CO₂ capture process. To facilitate the development of thermodynamic models, linear Gibbs free energy, enthalpy, and heat capacity relationships using well-known amines as reference are used to correlate the standard reference state properties of ionic species with those of molecular species in the electrolyte system, which has been approved to provide a reliable and consistent way to estimate required parameters when there is minimal or no appropriate experimental data available. The proposed relationships have been applied to the development of an electrolyte nonrandom two liquid (NRTL) activity coefficient model for CO₂ absorption in aqueous 1-amino-2-propanol (A2P) solution, as an example to demonstration the methodology. With limited vapor–liquid equilibrium data and other thermodynamic properties, the parameters in the electrolyte NRTL model are identified with good accuracy.     

Experimental and modelling study of gas dispersion in a double turbine stirred tank

Gas dispersion in a double turbine stirred tank is experimentally characterised by measuring local gas holdups and local bubble size distributions throughout the tank, for three liquid media: tap water, aqueous sulphate solution and aqueous sulphate solution with PEG. For all these media, bubble coalescence generally prevails over breakage. Where average bubble size decreases, this can be attributed to the difference in slip velocity between different sized bubbles. Most of the coalescence takes place in the turbine discharge stream.A compartment model that takes into account the combined effect of bubble coalescence and breakage is used to simulate gas dispersion. The model predicts spatial distribution of gas holdup and of average bubble size, with average bubble size at the turbines as an input. Reasonable agreement between experiment and simulation is achieved with optimisation of two parameters, one affecting mainly the slip velocity, the other related mainly to the bubble coalescence/breakage balance. Different sets of parameters are required for each of the three liquid systems under study, but are independent of stirring/aeration conditions. The model only fails to simulate the smaller average bubble diameters at the bottom of the tank.     

Extraction of strontium ion from sea water by contained liquid membrane permeator

To develop a liquid membrane permeator that extracts strontium ion from sea water effectively and continuously, we investigated the extraction of strontium ion from artificial and natural sea water in a contained liquid membrane permeator. The permeator consists of a liquid membrane and two cells for aqueous solutions. The liquid membrane containing D₂EHPA(di-2-ethylhexyl-phosphoric acid) and DCH18C6(dicyclohexano-18-crown-6) is trapped between two hydrophobic microporous polyethylene films and separates sea water and the 0.2 M H₂SO₄ aqueous stripping solution. The effects of various operating parameters on the extraction of strontium ion were experimentally examined. The extractant of DCH18C6 -D₂EHPA mixture in kerosene had a synergistic effect on the extraction of strontium ion. The permeator extracted strontium ion from sea water effectively and continuously with long membrane lifetime.     

Description of the thermodynamic properties and fluid-phase behavior of aqueous solutions of linear,branched, and cyclic amines

The SAFT-γ Mie group-contribution equation of state is used to represent the fluid-phase behavior of aqueous solutions of a variety of linear, branched, and cyclic amines. New group interactions are developed in order to model the mixtures of interest, including the like and unlike interactions between alkyl primary, secondary, and tertiary amine groups (NH₂, NH, N), cyclic secondary and tertiary amine groups (cNH, cN), and cyclic methine-amine groups (cCHNH, cCHN) with water (H₂O). The group-interaction parameters are estimated from appropriate experimental thermodynamic data for pure amines and selected mixtures. By taking advantage of the group-contribution nature of the method, one can describe the fluid-phase behavior of mixtures of molecules comprising those groups over broad ranges of temperature, pressure, and composition. A number of aqueous solutions of amines are studied including linear, branched aliphatic, and cyclic amines. Liquid–liquid equilibria (LLE) bounded by lower critical solution temperatures (LCSTs) have been reported experimentally and are reproduced here with the SAFT-γ Mie approach. The main feature of the approach is the ability not only to represent accurately the experimental data employed in the parameter estimation, but also to predict the vapor–liquid, liquid–liquid, and vapor–liquid–liquid equilibria, and LCSTs with the same set of parameters. Pure compound and binary phase diagrams of diverse types of amines and their aqueous solutions are assessed in order to demonstrate the main features of the thermodynamic and fluid-phase behavior.     

Correlations for prediction of diffusion in liquids

Based on an extensive experimental data collection (about 1925 points), empirical correlations for the estimation of binary liquid diffusion coefficients have been developed. The new correlations for organic mixtures and for aqueous solutions (including dissolved gases) require only well known and simple parameters like the viscosity of the solvent and the molar volumes of solute and solvent at the normal boiling point. They are shown to predict the limiting diffusion coefficients with the same or sometimes better accuracy than established correlations which make use of additional parameters. The concentration dependence of the mutual diffusion coefficients can be estimated from the knowledge of the two limiting diffusion coefficients and thermodynamic data. Established equations are investigated and classified for different groups of systems e.g. nonpolar + nonpolar, nonpolar + polar and polar + polar liquid mixtures.     

有机物水溶液粘度的关联和预测

在Eyring的液体粘性流动模型的基础上,根据Sandler的水溶液过量自由焓溶质聚集模型,导出有机物水溶液的粘度模型。利用该模型方程参数与温度的关系,可预测低压下各种温度和不同组成的有机物水溶液的粘度。用该模型计算了7个体系442个不同温度和组成的二元水溶液和3个体系164个不同温度和组成的三元水溶液的粘度,计算值与实验值的总平均相对偏差分别为1.554%和2.588%,计算值与实验数据吻合很好。     

A study of the applicability of the capillary rise of aqueous solutions in the measurement of contact angles in powder systems

The rate of wetting of a powder bed was studied in terms of the wetting parameters, liquid surface tension and powder/liquid contact angle, using three carbon black powders and aqueous solutions of surfactants and organic liquids. The rate of capillary rise of pure organic liquids through a powder bed can be described by the Washburn equation, and when compared with the behavior of aqueous surfactant solutions, it showed that deviations from linearity of the latter are attributable to adsorption of surfactant on the solid surface with resultant depletion of solute from the liquid phase. Agreement between Washburn capillary rise results and sessile drop results was observed whenever adsorption was absent.     

Wäßrige Flüssigmembranen — Stand der Entwicklung

Aqueous liquid membranes – State of the art. Use of emulsion liquid membranes with an aqueous membrane phase is a promising technique for the separation of hydrocarbons, if distillation is difficult or impossible. Intensive investigations on aqueous membranes during the past five years have increased our knowledge of the mass transfer mechanism which exploits different solubilities and diffusivities for the separation of hydrocarbons. The influence of the most important process parameters on the selectivity of the separation and on an overall mass transfer coefficient, serving as a measure of the mass transfer rate, are discussed. Possible applications and further developments are presented.     

Mass transfer performance of structured packings in a CO2 absorption tower

This paper studies the mass transfer performance of structured packings in the absorption of CO2 from air with aqueous NaOH solution. The Eight structured packings tested are sheet metal ones with corrugations of different geometry parameters. Effective mass transfer area and overall gas phase mass transfer coefficient have been measured in an absorption column of 200 mm diameter under the conditions of gas F-factor in 0.38–1.52 Pa0.5 and aqueous NaOH solution concentration of 0.10–0.15 kmol·m?3. The effects of gas/liquid phase flow rates and packing geometry parameters are also investigated. The results show that the effective mass transfer area changes not only with packing geometry parameters and liquid load, but also with gas F-factor. A new effective mass transfer area correlation on the gas F-factor and the liquid load was proposed, which is found to fit experiment data very well.     

Study on creeping film pertraction. Recovery of copper from diluted aqueous solutions

Creeping film pertraction (CFP) is a new liquid membrane technique for simultaneous removal and concentration of dissolved species from their diluted aqueous solutions. A mobile organic membrane interposed between two creeping aqueous films, a donor (feed) solution and an acceptor (strip) liquor, selectively transports the specified species. CFP is a continuous mass transfer process in which eddy diffusion controls the mass fluxes in all three liquid films. A laboratory scale pertractor—CFP-50—was used to study the effects of principal process parameters on pertraction efficiency in the case of copper transport across a membrane of parafinic oil, containing 2% (vol.) commercial oxime extractant ACORGA P-5100 as carrier.     

鼓泡反应器中幂律型流体流动与传质特性

很多废水处理装置涉及非牛顿型流体中的多相流动和传质问题,研究其中的气液传质过程有助于实现装置的优化设计和高效节能运行。以鼓泡反应器内清水和不同质量分数的羧甲基纤维素钠（CMC）水溶液为实验对象,分别研究气相表观气速和液相流变特性对气泡尺寸分布、全局气含率和体积氧传质系数的影响。实验结果表明,液相的流变特性对其传质特性参数均有较大影响。与清水相比,CMC水溶液中气泡平均直径和分布范围更大;清水和CMC水溶液的全局气含率均随表观气速的增加而增大;CMC水溶液的体积氧传质系数随CMC水溶液质量分数的增加而减小。基于实验研究,得出修正的体积氧传质系数公式和适用于幂律型非牛顿流体流动体系氧传递过程的无量纲关联式,可很好地实现非牛顿流体流动的废水处理装置中气液传质参数的计算。     

Application of peng-Robinson equation to high-pressure aqueous systems containing gases and sodium chloride

A novel approach is proposed for modeling vapor-liquid equilibria in systems containing aqueous NaCl and supercritical gases. The Peng-Robinson equation of state is used for all species, with the salt treated as a hypothetical liquid component. To correctly model the highly non-ideal liquid solution, a two-fluid model is used for the mixing rules in the equation of state. Effective pure-component parameters are reported for NaCl as well as binary interaction parameters for all possible binaries. Representation of high-pressure phase equilibria data show good agreement with experimental data. The principal advantage of this approach is the ability to treat high pressure systems containing non-volatile salts, while maintaining the simplicity of a cubic equation of state.     

Calculation of surface tensions for liquid mixtures using the SWCF-VR EOS and Butler-type method

A generalized surface tension model for various types of liquid mixtures by coupling the equation of state for square-well chain fluids with variable ranges and Butler type method was presented. Transferable molecular parameters fitted from experimental pVT of pure fluids were used. The reliability of this model were tested with liquid mixtures including 87 conventional fluid mixtures, 20 aqueous alcohol-amine solutions, 12 ionic liquid solutions, 7 polymer solutions, and 4 liquid alloys. The overall average absolute deviations in correlations with one parameter for all binary mixtures, in predictions for all conventional binary mixtures except aqueous solutions and for all ternary mixtures are 1.94%, 1.82%, and 2.69%, respectively. The potential application of the model in simultaneously describing the phase equilibrium and surface tensions was partially verified. The results demonstrate that this model has an overall robustness and reliability in calculations of surface tensions for various liquid mixtures.     

统计速率理论研究乙醇-水溶液中硫酸钾晶体的溶解动力学

Dissolution kinetics of K2SO4 crystal in aqueous ethanol solutions was studied on-line with ion selective electrode. The concentration of K2SO4 was calculated from the determined electromotive force in which the activity coefficient of components in the liquid phase was calculated with the Pitzer equation. Dissolution kinetic parameters in the modified statistical rate theory were regressed. The correlation results show that dissolution rate of K2SO4 is slower in aqueous ethanol solutions than that in aqueous solutions. The two most important reasons are as follows: (1) The solubility of K2SO4 in aqueous ethanol solutions is lower than that in aqueous solutions, which causes a decrease of the driving force of mass transfer. (2) The process of surface reaction of K2SO4 became slower due to the addition of ethanol, so that the whole process is mainly dominated by the surface reaction instead of mass transfer.     

统计速率理论研究乙醇-水溶液中硫酸钾晶体的溶解动力学

Dissolution kinetics of K2SO4 crystal in aqueous ethanol solutions was studied on-line with ion selective electrode. The concentration of K2SO4 was calculated from the determined electromotive force in which the activity coefficient of components in the liquid phase was calculated with the Pitzer equation. Dissolution kinetic parameters in the modified statistical rate theory were regressed. The correlation results show that dissolution rate of K2SO4 is slower in aqueous ethanol solutions than that in aqueous solutions. The two most important reasons are as follows:(1) The solubility of K2SO4 in aqueous ethanol solutions is lower than that in aqueous solutions, which causes a decrease of the driving force of mass transfer. (2) The process of surface reaction of K2SO4 became slower due to the addition of ethanol, so that the whole process is mainly dominated by the surface reaction instead of mass transfer.