The article contains sections titled: 1. Fundamentals and Fields of Application 2. Thermodynamic Fundamentals 2.1. Graphic Representation of Phase Equilibria 2.1.1. Triangular Diagrams 2.1.2. Other Graphic Representations 2.2. Measuring Methods of Phase Equilibria 2.3. Correlation of Phase Equilibria 2.4. Selection of Solvent 2.5. Determination of Mass‐Transfer Performance 2.5.1. Specific Methods for Determining the Theoretical Number of Stages 2.5.2. Determining Equipment Behavior Based on Drop‐Population Balances 2.5.3. Evaluation of Stage‐Number Calculation for Process Design 3. Apparatus 3.1. Survey 3.1.1. Columns without Energy Input 3.1.2. Pulsed Columns 3.1.3. Columns with Rotating Internals 3.1.4. Mixer – Settlers 3.1.5. Centrifugal Extractors 3.2. Fluid‐Dynamic Fundamentals 3.2.1. Problems and Process Strategy 3.2.2. Operating Characteristics of Pulsed Columns and Columns with Rotating Internals 3.2.3. Fluid Dynamic Calculation Methods 3.3. Apparatus Design 3.3.1. Internals and Operating Conditions 3.3.2. Column Diameter 3.3.3. Column Height 3.4. Criteria for Equipment Selection 4. Phase‐Separation Equipment 4.1. Gravity Settlers without Inserts 4.2. Settlers with Coalescing Aids 5. Liquid – Liquid Extraction Processes 5.1. General 5.2. Combined Processes of Extraction and Distillation 5.3. Reactive Extraction 5.3.1. Introduction 5.3.2. Extraction Mechanism of Different Types of Solvent 5.3.3. Uses 5.3.4. Setting up an Extraction System 5.3.5. Diluents and Modifiers Liquid–liquid or solvent extraction is the separation method of choice where distillation fails, e.g., for azeotropic mixtures or temperature‐sensitive components. Separation is achieved by adding a liquid solvent phase to the original liquid carrying the component(s) to be extracted. One of the phases must be dispersed into droplets in the other, continuous phase to achieve a sufficiently large mass‐transfer interface. Extraction is performed in mixer–settler equipment or extraction columns, which are frequently equipped with rotating internals or pulsators for energy input to positively influence droplet size. Here the different principles for equipment design are presented: coupling thermodynamic equilibrium and balances for determination of required number of theoretical stages, fluid‐dynamic design, and selection of equipment and operating conditions. Additionally, a modern method for linking these aspects more efficiently is shown. A method to characterize coalescence behavior for settler design is explained. Finally, reactive extraction is presented, which is applied, e.g., for metal separation or purification. The separation efficiency in reactive extraction is enhanced by a chemical reaction.

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Das Trennen von Flussig/Flussig-Dispersionen gilt als Verfahrensschritt, der in vielen Fallen im technischen MaBstab erhebliche Schwierigkeiten bereitet. An einer Reihe von Beispielen aus chemischen Prozessen wird gezeigt, wo Phasentrennprobleme auftreten, welche Auswirkungen sie haben und welche industriell praktikablen Methoden fur ihre Losung zur Verfiigung stehen. Die vorgestellte Problemanalyse geht vom Entstehungsmechanismus der Dispersion aus und fuhrt zu einer qualitativen Charakterisierung der verschiedenen Koaleszenzprobleme, ohne daB die Kenntnis des Tropfenspektrums vorausgesetzt wird. Diese Vorgehensweise gewinnt wesentliche Erkenntnisse aus der Beurteilung vorangegangener Verfahrensschritte. Aus den Ursachen fur eine schlechte Phasentrennung werden MaBnahmen zu deren Verbesserung aufgezeigt: Modifikation der physikalischen Eigenschaften, h d e r u n g der Dispergierung, mechanische Trennhilfen (Packungen, Koalisierfilter), Anlegen eines elektrischen Feldes, Zentrifugen und Hydrozyklone, koaleszenzfordernde chemische Zusatze. Fur die Auslegung von Apparaten zur Durchfuhrung dieser Verfahrensweisen werden industriell anwendbare Methoden mitgeteilt.Coalescence problems in chemical processes. Separation of liquid/liquid dispersions is a process step which often gives rise to considerable difficulties on an industrial scale. A number of selected examples taken from chemical processes demonstrates where phase separations occur, the consequences they may have, and what industrially practicable methods are available for their solution. The problem analysis presented starts from the mechanism of generation of the dispersion and leads to a qualitative characterization of the various coalescence problems without presuming any knowledge of the droplet spectrum. This procedure acquires important knowledge from an assessment of prior process steps. Measures for improvement are deduced from the causes of poor phase separation: modification of physical properties, change of dispersion, use of mechanical separation aids (packings, coalescing filters), application of an electrical field, centrifuges and hydrocyclones, coalescence-promoting chemical additives. Industrially applicable methods are reported for design of equipment for implementation of these approaches.

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dieses Berechnungsverfahren ist es, daB zu seiner Anwendung nur meBtechnisch einfach zu erfassende GroBen benotigt werden.Ausgehend von einer Massenbilanz an einem Volumenelement im Filterkuchen wird bei der Herleitung des Dispersionsmodells eine Differentialgleichung fur die Konzentration im Filterkuchen aufgestellt: