Bauarten von Kristallisatoren

Types of crystallizers . In the industrial application of single mass crystallization from solution clear aims exist with regard to crystallizate qualities. To fulfil these aims, one can choose between various types of crystallizers. Magma types, i.e. agitated tank crystallizer, forced circulation and draft tube (baffle) crystallizer, as well as classifying types with the well-known Oslo-crystallizer belong to the present state of the art. The rates of secondary nucleation decrease in the same sequence as that given above and the possibilities of influencing crystal size distributions increase, and coarser crystals are produceable.     

Dimensionierung von Kristallisatoren

Current status of crystallizer design . This paper surveys current knowledge in designing large scale crystallizers. The volume of a crystallizer depends on the desired mean crystal size, the suspended magma density and the permissible supersaturation, the latter determining the growth velocity and the nucleation rate. Different techniques for measuring the rate of crystal growth are outlined, as are also the methods used in its calculation, which are based upon various models of crystal growth. In designing a large scale crystallizer the phenomena of fluid dynamics and heat transfer must be taken into consideration. The paper deals with these two areas in detail and discusses problems associated with the control of population balance in the slurry.     

Auslegungsgrundlagen von Kristallisatoren

Design principles of crystallizers . Numerous processes in the chemical, heavy chemical, and food industries involve a crystallization step. Most commonly, a crystalline product is to be obtained from solution. Crystallizers are designed with the aim of cost-effective isolation of the product in the desired quality, i.e. in the necessary particle size and purity, while minimizing encrustation.     

Entwicklung von Siliciumcarbid-Verbundwerkstoffen

Development of silicon carbide composites . This paper describes the production of fibre-reinforced SiC composites applying the methods of chemical vapour impregnation (CVI), reaction bonding by liquid silicon impregnation (RB-SiC), and impregnation with subsequent polymerisation and thermal decomposition of organosilicon compounds. The chemical and physical fundamentals of these processes are discussed. Composites of different fibre/matrix combinations are introduced; the most promising combinations can be selected from the experimental results presented.     

Auslegung und Maßstabsvergrößerung von Kristallisatoren

Design and scale-up of crystallizers . Industrial scale crystallizers have to be designed in such a way that the crystalline product has the design particle size distribution, crystal form, and purity. Data on multiphase flow, solubility, balances of mass, energy, and number of crystals, kinetics (crystal growth rate and nucleation rate), and heat transfer are required. The present article discusses problems of kinetics in greater detail than other aspects. Multiphase flow is considered only briefly and heat transfer not at all. Familiarity with the terms homogeneous and heterogeneous (primary) and secondary nucleation [1, 2] is also assumed. This contribution is based on evaluation of available literature.     

Entwicklung von Biopolymermembranen mit funktionellen Eigenschaften

The manifold possibilities to apply coatings made from biopolymers require the design of such membranes with functional properties. The influence of different additives and process parameters on the mechanical stability and penetrability of biopolymer membranes, especially of films based on alginates, is given in this work. Spheres of alginates made by the falling droplet method were used as model system. Besides different effects of additives it turned out that the mechanical stability and the penetrability could be influenced independently.     

Entwicklung und Projektierung von Anlagen zur Hochdruck-Extraktion von Naturstoffen

Development and planning of plant for the high-pressure extraction of natural products . Important criteria in the designing of plant for the recovery of carrier or extract are reviewed, especially for the extraction of natural products with supercritical CO₂. The quantities to be determined in the planning of a large-scale plant are outlined and a typical process, the extraction of spices, is discussed in detail. The plant components and assemblies are presented together with their particular process engineering and construction characteristics. Finally, the thermodynamic aspects are dealt with in more detail and ways of optimizing a large-scale plant and reducing the power consumption are outlined. Particular attention is paid to the question of optimization regarding the most economic method of operation of such a plant in the future.     

Ein experimentell-numerischer Ansatz zur Entwicklung von Staubfreisetzungsfunktionen

When bulk materials are subjected to stress, the energy input releases particles, which disperse in the air. This is an effect that has to be avoided for both process-related and safety reasons. Therefore, the research project described here deals with the development of a method for the prediction of dust emissions during processes handling bulk materials. It is based on an experimental and concurrently on a numerical level. The calculation of dust emissions in advance allows for implementation of necessary measures before the construction and operation of a plant processing bulk materials.     

Entwicklung eines Simulationsprogramms zum Scale-up von Hydrierreaktoren

Development of a simulation program for the scale-up of hydrogenation reactors. The scale-up of trickle-bed reactors to pilot and production scale has been difficult and necessitated considerable over-dimensioning. Therefore a simulation program based on a cell model has been developed in which the dimensions of a cell are directly related to the dimensions of the catalyst particles used. The kinetic equation is formulated with an effective rate coefficient as the only key parameter to be adjusted. With this coefficient the intrinsic rate coefficient, the mass transfer, and the incomplete catalyst particle wetting are considered. The model was applied to the hardening of fatty acids and the hydrogenation of fatty acid methyl esters in laboratory reactors. Comparison with experimental results of pilot and industrial scale is favourable. Thus the model can be used for the scale-up of trickle-bed reactors.     

Die Entwicklung von Enzymen zur Verwendung in Waschmitteln

Development of Enzymes for their Use in Washing Agents The author deals with the properties of enzymes which are suitable as additives to biologically active washing agents. Methods for the determination of the above properties are reported. The investigations showed that the efficacy of a biologically active washing agent depends not only upon the properties of the enzymes but on the composition of the washing agent as well. The combination of enzymes and surfactants leads to a synergic effect. The further possibilities of development in the field of biologically active washing agents are given at the end.