MEASUREMENT TECHNIQUES FOR DROP SIZE DISTRIBUTIONS IN STIRRED LIQUID-LIQUID SYSTEMS

The design of stirred tank reactors for liquid-liquid dispersions usually requires expensive experimental investigations. Complete models for the drop size distribution as a function of power input, material and process parameters are rare and relatively inaccurate. Therefore, it is necessary to analyze drop size distributions for accurate modelling. Furthermore, industrial applications, like e.g., suspension polymerization processes, require a distinct average drop diameter and a small standard deviation of the distribution. For the controlling of such systems fast acquisition of information is needed but difficult to obtain. While many users are confronted with both requirements an adequate measurement technique for all applications is needed but has not yet been developed. The aim of this publication was to give an overview for already existing measurement techniques and compare the most important properties and the resulting data to simplify the decision process for the selection of the "right" measurement technique according to the used system. The measurement applications are divided into three main groups: sound, laser and photo based techniques. The Lasentec FBRM (R), the 2D-ORM (R) from Messtechnik Schwartz GmbH and the FBR-sensor which all give online and in-situ information and furthermore an in-house developed endoscope technique are discussed in detail. They have been tested for various applications in a stirred tank and the results are compared. It is clearly shown that laser based methods give only qualitatively good but fast results for the tested system toluene-water. Quantitatively accurate experimental results of the endoscope technique gave a good base for testing and developing numerical models for even transient behaviour of drop size distributions.