Membrangestützte Flüssig/Flüssig‐Extraktion – Wo stehen wir heute?

Thanks to advancements in materials science and manufacturing technology, membranes are now available for stable liquid‐liquid extraction processes. Rigorous calculation models can be used to calculate the membrane areas required for a given separation task as well as to optimize the module design. In rapid tests, the basic suitability and kinetic parameters can be determined. Thus, the general requirements are for utilizing the specific advantages of this separation technology in technical applications are fullfilled.     

Batch‐Rektifikation mit Mittelbehälter

Batch Distillation in Middle Vessel Columns Batch distillation in a middle vessel column is a promising alternative to conventional batch distillation as disadvantages such as high temperatures in the feed vessel or a high energy and time demand of the process can be avoided. The article describes the basics of the synthesis of processes for the separation of zeotropic and azeotropic mixtures using this type of column. Furthermore, experimental results are presented and the advantages of batch distillation in a middle vessel column are explained.     

Waschverfahren partikulär‐disperser Systeme – Verfahrensspektrum und Aspekte der Verfahrensauswahl

Washing of Disperse Solid Systems – Existing Washing Processes and Guidelines for Choosing the Appropriate Washing Procedure Washing of disperse solid systems is a widely used and complex operation. Since the washing‐step is mostly integrated into other process operations, it is subject to numerous demands, which exceed the primary demands like a good separation result and a low specific wash liquid demand. Because of the phenomenology and limits of different washing procedures it is difficult to choose an appropriate washing process. Additionally, the acting transport mechanisms of some washing procedures are not yet sufficiently understood. This work shows a broad overview over the existing washing processes, the numerous parameters and the demands they have to fulfill. A categorization of washing procedures as well as a classification of the processes concerning their macroscopic transport phenomena are the base for a broad decision chart which compares and evaluates existing washing processes and shows their individual limits. The work can be seen as a rough guideline for choosing the appropriate washing procedure.     

Verhalten gedehnter Flüssigkeitsfäden in viskosen Flüssig/Flüssig‐ Systemen

The stability of jets in elongational flow is exploited to receive thin threads before break up. Fine drops can be generated in suitable geometries with comparable large cross flow areas. The examination deals with the stability of liquid threads simultaneously extended with the continuous phase in convergent flow. Break up limits and regimes are discussed.     

Hydrodynamik und Stofftransport in einem Perlschnurreaktor für Gas/Flüssig/Fest‐Reaktionen

In this work, a pellet string reactor was characterized with respect to hydrodynamics and mass transfer. The catalyst packing consists of a cylindrical channel with a diameter of 1.41 mm, which was filled with spherical catalyst particles, having an outer diameter of 0.8 mm. Under reaction conditions (liquid phase hydrogenation of α‐methylstyrene) overall (gas‐liquid‐solid) volumetric mass transfer coefficients for hydrogen between 0.8 and 5.5 s^–1 were computed. Due to high mass transfer rates and simple reactor geometry, pellet string reactors can be applied in industry as highly efficient reaction units.     

Interfacial tension of fluid system considering the nonstationary case with respect of mass transfer

Interfacial properties exert a fundamental influence on fluid/liquid separation processes, with the interfacial tension being an important quantity associated with mass transfer and mutual solubility of participating compounds. A better understanding of transport phenomena is achieved by obtaining interfacial tension data under different conditions of pressure and temperature and as a function of time. Generally, interfacial tension decreases with increasing pressure due to increased adsorption of the compressed fluid at the interface. In the case of considerable mutual solubility, interfacial tension further decreases with time as mass transfer into the bulk phase proceeds. Prediction of colloidal behaviour in a separation process requires acquisition of additional information on the presence of surfactants.     

Transport processes at single droplets in micellar liquid/liquid systems

In many industrial applications, the knowledge of the occurring transport processes in liquid/liquid systems is of great interest to design a multiphase reactor or an extraction column, for instance. All transport processes in liquid/liquid systems are governed by the interface. In some processes surfactants are needed. Surfactants change many interfacial properties which affect the transport processes. In this work, the influence of high surfactant concentrations (micellar systems) on transport processes is regarded. To understand, the occurring reduction of the drop rise velocity and of mass transfer rates experimental investigations of the occurring interfacial phenomena are carried out. Therefore, interfacial tension measurements as well as colloidal probe atomic force measurements of liquid/liquid systems were conducted. It was proved that for high nonionic surfactant concentrations a change of the phase behavior must be taken into consideration to describe transport processes in micellar liquid/liquid systems. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1092–1104, 2015