三相热偶合精馏过程的模拟

本文对具有双液相的精馏过程的数学模型予以修正,以适用于三相热偶合精馏过程;提出了以改进Naphtali-Sandholm法为基础的计算方法;给出了Jacobi矩阵及其所含各类子矩阵的结构和用于计算子矩阵中所有非零元素的偏导数表达式;用多相闪蒸结合自由焓比较校验存疑级上液相的分相情况.以正丁醇-水-正丙醇三元系的分离为例说明了此法的正确性,结果是满意的.     

蒸馏塔板上汽液传质系数的确定——非平衡池法(Ⅰ)模型的建立及求解

本文提出一种确定蒸馏塔板上汽液传质系数的新方法——非平衡池法.该法将塔板沿液流方向分为适当数目的串联非平衡池,通过联立求解每一池各相的物料衡算、能量衡算、相平衡和传质传热速率方程,可从塔板入口组成得到出口组成.调整汽液传质系数使计算的出口组成与实测值相等,从而可确定出两相传质系数.方程组用混合牛顿法求解.     

Axial dispersion in two phase co-current flow with fast and instantaneous reactions

Approximate solutions to the governing equations for two phase co-current flow with fast and instantaneous reactions between a gaseous and a liquid species are considered. These solutions are obtained by perturbation technique for large Peclet numbers of the gas and the liquid phases and by Galerkin's method for small and intermediate values of the gas and liquid Peclet numbers. The approximate solutions are compared with a numerical solution obtained under the limiting condition of the gas phase Peclet number becoming infinite. Criteria for axial dispersion in a two phase column are also obtained based on the perturbation solutions.     

液固搅拌槽中固、液相停留时间分布

本文以海沙和自来水为介质研究了在标准搅拌槽内影响固液两相停留时间分布的主要因素,以便比较两相之间的差异,并利用双区模型描述出口流体中固体和液体的停留时间分布。对所建立模型中的参数进行估值后,建立了模型参数与搅拌雷诺数、固体颗粒浓度及搅拌槽几何参数之间的关联式。     

Heterogenous azeotropic distillaion-homotopy-continuation methods

An algorithm for the simulation of three-phase distillation towers and associated phase separators is presented. The algorithm utilizes the homotopy-continuation method of Allgower and Georg[1] to accurately track the homotopy path, with extensions to avoid limit points when multiple solutions are encountered and when liquid phases are introduced on the trays. The Allgower and Georg algorithm is also extended to track solution paths in parametric studies. Emphasis is placed on the calculation of liquid—liquid equilibria, with a reliable, yet efficient, homotopy-continuation algorithm introduced. An effective method for incorporating the LLE algorithm in the homotopy-continuation algorithm for heterogenous distillation is also introduced.

The combined algorithms have located two steady-state solutions for an industrial azeotropic distillation tower a very narrow range of the reflux ratios, one with a single liquid phase on the trays, the other with two liquid phases on 70% of the trays. In addition, for the dehydration of ethanol with benzene, it has detected a region in which five steady-state solutions exist for the same specifications. Three of these solutions were reported by Magnussen .[2] and observed in dynamic simulations by Prokopakis and Seider[3].     

先进理念是尿素技术创新之本

对传统法尿塔是在全液相状态下进行合成反应的理论观点提出了质疑;从热力学反应过程和尿素合成塔内气液相体积变化过程对传统法尿素合成反应的化工过程进行了论证,得出工业装置尿素合成塔内呈气液两相流物系的尿素合成模型构架;通过对国外多种尿素流程的剖析,认为尿塔以气液两相流的合成过程具有普遍性意义,提出了传统法尿素合成理论有待于完善和更新的观点。     

THE THREE-LIQUID PHASE NONEQUILIBRIUM PROBLEM

This article deals with the development of a non-equilibrium model for solving problems with three liquid phases. The model consists of the material balance equations, the interface material balance equations, the transfer-rate equations and the interface equilibrium equations. First the two liquid phase non-equilibrium solution is obtained. Then rigorous stability analysis in the form of the tangent plane criterion is used on two liquid phase solutions to detect the presence of the third liquid phase. The model equations are then solved to obtain the three liquid phase non-equilibrium solution.     

Liquid–liquid–solid mass transfer and phase behavior of heterogeneous etherification of glycerol with isobutene

Previous experiments observed auto‐acceleration in the etherification of glycerol with isobutene. This article engaged to uncover the reason for this phenomenon via investigating the heterogenicity, including liquid–liquid phase equilibrium and liquid–liquid–solid mass transfer, of the reaction system. Phase behavior analysis showed that the reaction mixture separates into two liquid phases during the whole course of the reaction. The produced mono ethers of glycerol thermodynamically promote the homogenization of the two liquid phases. The modeling results of liquid–liquid–solid mass transfer indicated that the resistance of mass transfer is insignificant during the reaction. The bulk compositions of the two liquid phases are very close to their corresponding equilibrium compositions. An increase of isobutene concentration in the reaction phase is believed to lead all reactions speeding up. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2526–2535, 2018     

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.     

CFD‐Simulation und LDA‐Messung der Strömungsvorgänge beim Fluidphasenresonanzmischen

The principle of fluid phase resonance mixing is to apply harmonic oscillating pressure via a gas cushion on a liquid phase in a vessel and thus to cause the liquid phase to start oscillating. This principle is simulated as an unsteady flow of two separate phases with open source CFD software OpenFOAM and the results are verified with measurements by Laser Doppler Anemometry.     

PROVISION与PHEES集成模拟无机盐生产工艺

以ＰＲＯＶＩＳＩＯＮ和ＰＨＥＥＳ为基础,建立了固液相平衡级计算的通用方法,通过自动判别平衡时的相数及析出固相的种类,可获得固液平衡时各相分率和组成,通过对几种无机盐生产的蒸发、结晶流程的模拟计算证明该方法可适用于目前文献中尚难以处理多离子复分解反应体系,从而满足涉及电解质溶液的化工过程的模拟计算与实际生产的需要     

Effect of Binary/Ternary Fatty Acids Ratio and Glycerin on the Phase Behaviors of Soap Solutions

Phase behaviors of liquid soaps prepared with single myristic acid, binary fatty acid mixtures and ternary fatty acid mixtures (with 30% total fatty acids) are described. The influence of glycerin on the phase behaviors of ternary soaps is discussed. Phase behaviors were characterized by combining pH, viscosity, polarization microscopy, X‐ray scattering and differential scanning calorimetry (DSC) analysis. The results showed that the kind and proportion of fatty acids played key roles in the phase behaviors of soaps. Glycerin had a significant influence on the phase behaviors of soaps. Liquid and Cub + Hex (cubic and hexagonal phase) phase were stable, while Liq + Crystal (liquid micelle and crystal phase), Liq + Lam (liquid micelle and lamellar phase), Liq + Hex + Lam (liquid micelle and hexagonal and lamellar phase) phases displayed separation regions, Glycerin was investigated to improve the stability of separation phases for two weeks, appropriate percentage of the fatty acids in soaps application.     

Simultaneous heat and mass transfer in binary distillation—I: Theory

Binary distillation in continuous contact equipment is modeled as a simultaneous heat and mass transfer process. In order to account for the interactions between heat and mass transfer between the two phases, the equations developed from enthalpy and material balances are analyzed simultaneously and it is revealed that the individual phase mass transfer coefficients can be evaluated rigorously by measuring liquid phase compositions and temperatures in distillation experiments. Using the theoretical relations, it is proved that the liquid phase in a distillation column will be saturated if and only if there is negligible resistance to mass transfer in the liquid film. For the case of comparable resistances in both phases, the possible amount of superheat in the liquid phase would be considerable and thus convenient to determine experimentally. The liquid phase temperatures are shown to be important in experimental analysis (i.e. in determining the individual phase transfer coefficients) but not in design applications. For the latter case, the model equations reduce to the conventional mass transfer relations which are not as sensitive to temperatures.     

The important role of local dispersed phase hold-ups for the calculation of three-phase bubble columns

A computational fluid dynamics model is used to calculate a three-phase (air-water-solid particles) flow in a bubble column. The calculation of multi-phase flows is significantly influenced by the formulation of the inter-phase drag and the modelling of the turbulence. Both are influenced by the dispersed phases. The k-ε turbulence model extended with terms accounting for the bubble-induced turbulence is used to calculate the eddy viscosity of the liquid phase. Bubble-bubble and particle-particle interactions are considered as well as a direct momentum transfer between the two dispersed phases bubbles and solid particles. The local volume fractions of the dispersed phases are considered for the calculation of the drag coefficients between the dispersed phases and the continuous phase. Measured local gas and solid hold-ups as well as measured liquid velocities are compared with the corresponding calculated results. The measured and the calculated results show good agreement.     

Modelling of dispersed bubble and droplet flow at high phase fractions

The present paper describes an Eulerian two-fluid model for the prediction of dispersed two-phase (gas/liquid and liquid/liquid) flow at high volume fractions of the dispersed phase. The model is based on the standard Eulerian approaches for modelling two-phase flow that have hitherto been limited in validity to dilute systems. An extension to high phase fractions is made here and this involves two aspects. First, the closure models for inter-phase forces (namely drag and lift) are modified to account for the high concentration of the dispersed phase. Second, a turbulence model based on the k-ε equations for the mixture of the two phases is formulated. This turbulence model is suitable for computations at all phase fraction values and reduces to the equivalent single phase model in the extremes when only one or other of the phases is present. The model uses a response function to link the turbulent fluctuations of the continuous and dispersed phases. The variation of this response function with phase fraction is determined from experimental evidence made available recently. The overall model is applied to the prediction of air/water bubble flow in a pipe with a sudden enlargement where phase fractions can reach 25% and for which experimental data exist. The calculations show that marked improvement in the quality of the predictions, as compared to measurements, is obtained over the available model for dilute systems.     

酮麝香-二甲苯麝香双液相萃取结晶

To evaluate the effect of two liquid phase on the separation of musks mixture, the phase equilibria of musk ketone musk xylene dimethyl sulfoxide heptane system were studied for the first time. The whole and every part of the phase equilibrium for the quaternary system were shown by three-dimensional phase diagrams, the liquid-liquid equilibria, solid-liquid equilibria and solid-liquid-liquid equilibria of the quaternary system were also shown. As a result, the compositions of musks in the equilibrium liquid phases were different from those in the feed, that is, musk ketone was enriched in dimethyl sulfoxide phase while musk xylene was enriched in heptane phase. So these equilibrium liquid phases were useful in separating musk ketone and musk xylene. On the basis of these results, a new process “two liquid phase extractive crystallization” was proposed to separate the eutectics of musk ketone and musk xylene.     

A PRACTICAL METHOD FOR RECTIFYING INTERFACIAL TENSION DATA TO PREDICT THE SHAPE OF INTERFACES IN AN IMMISCIBLE LIQUID/LIQUID/GAS SYSTEM

The shape of interfaces formed by the contact of two liquid phases, immiscible with each other, and a gaseous phase can be predicted on the condition that the tension to work at each interface is known with a sufficient accuracy. In general, interfacial tension data available are not so accurate, however, as to be useful as they are in predicting the shape of interfaces, particularly when the spreading coefficient of either liquid (liquid 1) on the other (liquid 2) has a negative value of a small magnitude. Presented in this note is a simple method to rectify the interfacial tension data, with the aid of a measurement of the radius of a lens of liquid 1 of a known volume placed on the horizontal surface of liquid 2, and thereby make them usable for predicting interfacial geometries. The method is tested by applying it to benzene/water and n-pentane/water systems.     

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     

固液相平衡级的通用算法

从热力学原理出发,建立了一种固液相平衡级计算的通用方法,通过自动判别平衡时的相数及析出固相的种类,经过较少的迭代次数就可获得固液相平衡时各相分率和组成,从而满足化工过程模拟计算与实际生产的需要。由于该解法为虚拟的等温蒸发过程,在判别平衡相数的同时给出了过程中晶体的析出顺序与各晶体刚析出时溶液组成,这些中间结果为分离过程的模拟计算提供了理论指导。此算法不仅完全不依赖于相图,而且还可通过对不同进料配比的计算,绘制出全范围内的固液相图。通过实例计算证明该方法可适用于目前文献中尚难以处理的复盐、含结晶水盐以及多离子体系。