Internal mixer optimization

Silica compounds are generally processed in conventional internal mixers, preferably with intermeshing rotors. These mixers are designed and optimized for carbon black-fiUed compounds in which mixing is based only on physical processes. When a silica-silane reinforcing system is used, additionally a chemical reaction, the sUanization, occurs. One of the main influencing factors of the silanization reaction is the concentration of ethanol in the compound as well as in the mixer [25,26]. As the silanization finally reaches an equilibrium, low concentrations of ethanol in the compound are expected to enhance the reaction rate. 

P. S. Kim and White [4,73] have sought to model flow in intermeshing rotor internal mixers and the optimization of rotor design. They have rated different machines described in the patent literature. 

The internal mixer has been used for many years. Much experience has been accumulated to make optimal use of the mixer. Significant improvements have been made over the... 

General improvements of oxidation reactors (e.g., for terephthalic acid) include optimized feed points for gas and liquid, internals such as spargers, mixers, draft tubes, or trays, or an optimized setup with a secondary reactor [50, 51]. 

N. Kockmann, T. Kiefer, M. Engler, P. Woias, Channel networks for optimal heat transfer and high throughput mixers, ESI International Conference on Heat Transfer and fluid flow in Microscale, II Ciocco, Italy, 2005. 

Batch Extractions. In nearly all commercial scale operations, a continuous extraction process, either mixer-settlers or colunm units, would be used. However, batch extraction experiments are useful for assessing overall feasibility and for optimizing the many process variables such as emulsion formulation and volume ratios of the internal, membrane, and external phases. Consequently, the most common experiment in this study was the batch extraction. In these experiments, 500 ml of a selenium solution (1 mg/L) were prepared in the extraction vessel, either in the presence or absence of other competing anions. The prepared emulsion (50 ml) was added and the mixture was stirred at a speed of 150 rpm. In this manner the emulsion drops were uniformly dispersed in the external phase while extraction proceeded. Samples of the external aqueous phase were taken at appropriate intervals and the concentrations of Se(IV), Se(VI), and sulfate were determined. 

Similar optimization studies were done for the reduction step. Therefore, a cooled, freshly prepared ozonolysis reaction mixture was fed to microstructured reactors and contacted with a NaBH4 solution (3.5 M in DMF). For completion of the reduction, the microstructured mixer was connected to a residence time module (5 ml internal volume, LTF) (www.ltf-gmbh.com), as the rate of the reduction reaction is clearly slower than that of the ozonolysis. Within the scope of tested microstructured reactors, again the five-channel mixer by mikroglas (www. mikroglas.com) performed best. 

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