Marangoni效应对填料塔精馏传质过程的影响

通过 4种正体系、 5种负体系的精馏实验 ,考察了Marangoni效应对填料塔中传质过程的影响。结果表明 :正体系的气相体积总传质系数KGa与组成无关 ,仅受气相流量 qG 的影响 ,可用关联式KGa =AqGB,和B =0 .94± 0 .0 4表示 ;而对负体系 ,由于Marangoni效应的存在 ,顺着液相流动方向 ,KGa逐渐减小。其关联式为KGa =AqGBMsC,B =1.0 5± 0 .0 4,C =0 .3± 0 .0 5 ,该式的平均误差约为 6%。     

气液界面Marangoni效应对传质系数的影响

在气液相际传质过程中,界面Marangoni湍动会对传质过程产生重要的影响,为此,建立了一套气液接触传质设备,以使得通过N2与异丙醇稀溶液逆流接触将液体中使表面张力降低的溶质解吸出来,从而引发Marangoni湍动,提高传质速率。发生Marangoni对流时,液相的传质系数比只依靠扩散传质而不考虑Marangoni效应时大,因此引出增强因子F这一概念,通过计算F的值即可判断Marangoni效应对传质速率影响的程度。提出了一个包括Marangoni准数的计算传质系数关联式,其计算结果与实验结果相符．     

Influence of the Marangoni Effect on Mass Transfer in Inclined Falling Films

The Marangoni effect on the mass transfer coefficient of falling films was investigated on inclined stainless‐steel plates to elucidate the influence on the mass transfer performance of structured packing surfaces. Desorption of ethanol from water generated the Marangoni effect in the liquid phase while the process of oxygen desorption from water was proceeded. The enhanced liquid phase mass transfer by the Marangoni effect was found to be related to the ethanol concentration in the liquid, inclination of the plate, and liquid flow condition. A generalized correlation was proposed to predict the effective enhancement factor of the system incorporated with the Marangoni effect.     

板式精馏塔的塔板效率

塔板效率包括:点效率、莫夫里效率和全塔效率,它们的值主要受流体多相流动时的动力学体系特性的影响;点效率可由双膜理论推出,莫夫里效率和全塔效率存在一定的内在关系。     

受热降膜Marangoni效应临界状态表征

采用红外热成像技术,研究了水和Na2SO4水溶液受热降膜的Marangoni效应及对降膜流动的影响。发现在降膜的流向和径向都存在热Marangoni效应,但Marangoni数却不能较好地表征Marangoni效应对液膜流动的影响程度。因而引入Marangoni效应影响因子ε。结果表明,ε能较好地表征Marangoni效应对液膜流动的影响程度,且不同溶液受热降膜存在一个近似相同的临界值(εLc)。当εLεLc,降膜流向热Marangoni效应将引起降膜明显的扰动。根据εLc值,可获得临界Marangoni数MaTc,L。     

Marangoni效应对降膜加热流动的影响

采用红外热像仪和智能化薄膜厚度测试仪研究了垂直板上受热降膜的流动特性, 得到液膜表面温度分布、液膜宽度、液膜厚度、局部液膜厚度随时间变化关系等参数 通过对这些参数的分析,可知降膜加热流动时,液膜表面出现轴向和径向的温度梯度,由此产生的表面张力梯度引起Marangoni效应对降膜流动有着很大的影响降膜加热流动过程中,Marangoni 效应使液膜产生较大的收缩,膜厚增加,表面波动加强.     

雾沫夹带对蒸馏塔板效率的影响

在塔板上液体完全混合的条件下,雾沫夹带对蒸馏塔板效率的影响,导出了一个新的关系式.著名的Colburn关系式是本文关系式的一种特殊情况(λ_o=1).计算结果表明,用于校正雾沫夹带对塔板效率的影响,本文关系式与Colburn关系式相比,具有较小的误差.     

自回流式精馏塔在轻组分精馏中的优势及操作特性

深入分析了自回流式精馏塔与传统精馏设备的区别以及在轻组分精馏中的优势,同时分析了其在生产过程中的操作特性。     

Numerical Simulation of the Solute‐Induced Marangoni Effect with the Semi‐Lagrangian Advection Scheme

The level set method is combined with the concentration transformation method to solve the interphase mass transfer process. However, the artificial diffusion generated in the mass transfer convection term across the interface is inevitable, especially when large shape deformation is encountered at high Reynolds numbers. A semi‐Lagrangian advection scheme is introduced to overcome this disadvantage. The methyl isobutyl ketone (MIBK)‐acetic acid‐water system is adopted to study the unsteady mass transport process accompanied with the Marangoni effect of a single deformable drop ascending in the infinite continuous phase. The predicted overall mass transfer coefficients agree with experimental data very well. The configuration of Marangoni convection is revealed and its effect on the interphase mass transfer process is investigated.     

Effect of Solute‐ and Solvent‐Derived Marangoni Flows on the Shape of Polymer Films Formed from Drying Droplets

The effects of mixed solvents on the shape of films formed on a hydrophilic surface from polymer solute droplets were investigated experimentally. The film shape depended on the two solvents used, and the mixing ratio. It was also found that the flow direction was dominated by solute‐derived rather than solvent‐derived Marangoni flows. Consequently, the changes in the shape of the film could not be explained only by the Marangoni flow direction.     

Electrohydrodynamic Spraying (EHDS) of Conductive Liquids and Mass Transfer in EHDS Distillation Columns

A physicomathematical model for electrohydrodynamic spraying (EHDS) of a conductive liquid and the mass transfer in a parallel plate electrodes system of an EHDS distillation column is presented. The influence of the electric field on the formation and general characteristics of the finely dispersed aerosol flow of the conductive liquid in EHDS distillation columns has been determined from the model. It allows to explain in detail the mechanism of the influence of the electric field on the mass transfer in the gas‐liquid system. In addition, the maximum possible liquid flow rate in the mass transfer section of the EHDS distillation column has been estimated. The role of process parameters is discussed in detail.     

短程蒸馏工艺参数对二元组分分离效果的影响

应用刮膜式短程蒸馏装置以邻苯二甲酸二甲酯(DMP)和邻苯二甲酸二丁酯(DBP)二元组分为对象进行系列实验。重点考察了进料速率、蒸馏温度、蒸馏压力和刮膜器转速对二元组分分离效果的影响。实验结果表明:在实验所取数值范围内,蒸馏温度和蒸馏压力为二元组分分离效果的主要控制因素,而进料速率和刮膜器转速对于分离效果的影响相对不明显。     

Experimental investigation and numerical simulation of Marangoni effect induced by mass transfer during drop formation

Marangoni effect induced by interphase mass transfer plays an important role in liquid–liquid extraction and reaction processes. The interaction of Marangoni effect and interphase mass transfer during drop formation at different injection rates and different initial solute concentrations was investigated by experimental and numerical simulation. The extraction fraction was measured and the corresponding correlation was proposed. The level‐set method coupled with mass‐transfer equation is for the first time used to simulate the mass‐transfer induced Marangoni effect during drop formation. The simulated drop volume, shape, and extraction fraction are in good accordance with experimental data. Through the numerical simulation, it is found that the mass transfer in the first mass‐transfer period is the most efficient during drop formation when Marangoni convection occurs. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4424–4439, 2013     

Influence of Temperature on the Surface Tension of Triton Surfactant Solutions

The surface tension of different Triton surfactants (X-100, X-405, and X-705) with or without adding sodium chloride was measured in the temperature range between 20 and 40°C using the maximum bubble pressure method. Rising temperature reduced the surface tension of Triton surfactants via disrupting the H-bonds between the ethylene oxide (EO) group and water. Increasing the number of the EO groups created the steeper thermal gradient of the surface tension. The data indicated that EO-water bonds are easier to be broken by rising temperature than the water–water H-bonds, with an entropy change of −0.535 J deg⁻¹ per mole of EO. The presence of NaCl decreased the surface tension for all systems. However, NaCl produced a synergistic effect with surfactants on the surface tension.     

Effects of Liquid Holdup in Condensers on the Start‐Up of Reactive Distillation Columns

Compared with start‐ups in conventional distillation columns, those in reactive distillation (RD) columns are much more time and energy consuming, and generate a large amount of by‐products which are not easy to deal with together. For several years, researchers have been trying out different methods to shorten the time required to lower the cost of the start‐up. In this work, a rigorous dynamic model in the ChemCAD simulator is applied to model the start‐up process for the esterification of ethyl acetate in a reactive distillation column. In the model, two sets of equations are employed: one for the fill‐up and heating stage and the other for the equilibration process which follows. In the fill‐up and heating stage, fluctuation curves of the reboiler temperatures with respect to time which are similar to those for conventional distillation columns are observed, while in the equilibration process it is found that the increase of the liquid holdup volume in the condenser reduces the time required to reach steady state for the reactive column and decreases the liquid holdup volume in the reboiler at the equilibrium state. This shows that the liquid holdup volume in the condenser has an important effect on the start‐up of reactive distillation columns.     

两液层体系传质引发的Marangoni效应的数值模拟

The Marangoni effect induced by mass transfer at the interface between two immiscible liquids displays important influence on laboratory and industrial operation of solvent extraction. A systematic numerical study of the two-dimensional Marangoni effect in a two liquid layer system was conducted. The linear relationship of the inter- facial tension versus the solute concentration was incorporated into a mathematical model accounting for liquid flow and mass transfer in both phases. The typical cases analyzed by Sternling ＆ Scriven （AIChE J., 1959） using the linear instability theory were simulated bv the finite difference method and good agreement between the theory and the numerical simulation was observed. The simulation suggests that the Marangoni convection needs certain time to develop sufficiently in strength and scale to enhance the interphase mass transfer, the Marangoni effect is dynamic and transient, and remains at some stabilized level as long as the mass transfer driving force is kept con- stant. When certain level of shear is imposed at the interface as in most cases of practical significance, the Maran- goni effect is suppressed slightly but progressively as the shear is increased gradually. The present two-dimensional simulation of the Marangoni effect provides some insight into the underlying mechanism and also the basis for further theoretical study of the three-dimensional Marangoni effect in the real world and in chemical engineering applications.     

Robust Nonlinear PLS Based on Neural Networks and Application to Composition Estimator for High-Purity Distillation Columns

The accurate and reliable on-line estimation of product quality is an essential task for successful process operation and control. This paper proposes a new estimation method that extends the conventional linear PLS (Partial Least Squares) regression method to a nonlinear framework in a more robust manner. To handle the nonlinearities, nonlinear PLS based on linear PLS and neural network has been employed. To improve the robustness of the nonlinear PLS, the autoassociative neural network has been integrated with nonlinear PLS. The integration allows us to handle the nonlinear correlation as well as nonlinear functional relationship with fewer components in a more robust manner. The application results have shown that the proposed Robust Nonlinear PLS (RNPLS) performs better than previous linear and nonlinear regression methods such as PLS, NNPLS, even for the nonlinearities due to operating condition changes, limited observations, and measurement noise.     

不同浓度二元复合体系对驱油效果的影响

近年来,水驱开发效果较差。油藏一般采取"调驱+水驱"方式取得了较好增油降水效果,但也存在药剂费用投入较高和配注工艺复杂等问题。对于强碱或者弱碱三元的复合体系中普遍存在采出液乳化和结垢的问题,优先选用聚合物和表面活性剂复合而成的二元体系,并采用室内物理模拟的方法,对比不同浓度聚/表二元体系的界面张力、黏度、驱油效果进行研究,发现聚/表二元体系可以实现超低界面张力的要求,而且聚/表二元体系的黏度也比较大,通过室内非均质岩心物理模拟实验研究,表明不同浓度的聚/表二元体系对驱油效果的影响效果差异较大。     

Experimental Investigation of Droplet Entrainment in the Feed Section of Distillation Columns

Droplet entrainment was investigated in the feed section of distillation columns for multiple feed inlet devices under different flow conditions. Entrainments from two-phase flow regimes were measured in the feed section of a column with an air and water system. A new feed inlet device named demister flash box was developed. Measurements with two-phase flow regime in the feed pipe indicated that the demister flash box had the lowest entrainment. Experiments with a surfactant in water due to low surface tension demonstrated that the entrainment was higher compared to water. In addition, entrainment determinations with high droplet flow rate from a spray nozzle in feed were conducted. The results indicated that the V baffle had the lowest entrainment.