Mixer scale

OS 40] [R 21] [P 29] A much larger dependence of yield on reaction temperature was observed for the caterpillar mixer-scale-up set-up than for the inter digital mixer-laboratory set-up [48]. At temperatares above ambient, significant decreases in yield of the order of several tens percent were determined. 

The importance of including mesomixing in the definition of tm has been demonstrated using jet-mixer scale-up experiments by Baldyga et al. (1995). In these experiments, the micromixing rate was found to scale as... 

The second method uses dimensionless numbers to predict scale-up parameters. The use of dimensionless numbers simplifies design calculations by reducing the number of variables to consider. The dimensionless number approach has been used with good success in heat transfer calculations and to some extent in gas dispersion (mass transfer) for mixer scale-up. Usually, the primary independent variable in a dimensionless number correlation is Reynolds number ... 

Therefore, even a moderate error in the mixer scale-up will have only a small effect on the agitator-side heat transfer coefficient. Other factors that include heat transfer area per unit volume are considerably more significant. For instance, in the jacketed tank, the heat transfer area per unit volume decreases upon scale-up. In order to assure the same proportionate heat removal or addition per unit batch size, additional heat transfer area (e.g., coils) may be required. Additionally, other variables such as temperature driving force may have to be adjusted to compensate for decreased heat... 

Oldshue, J. Y., "Current Trends in Mixer Scale-up Techniques," in Mixing of Liquids by Mechanical Agitation, ed. J. J. Ulbrecht and G. K. Patterson. New York Gordon and Breach Science Publishers, 1985, pp. 309-342. 

For a conservative pipeline mixer scale-up, use the following procedure ... 

As the equipment size is changed, this parameter remains fairly constant. This is a design feature of most high-shear granulators. The manufacturers purposefully design their equipment to deliver the same tip speed, regardless of mixer scale. 

Finally, following the examples discussed in the case studies, you can combine the results obtained at different end-points of the test batch or from different batches or mixer scales (assuming geometrical similarity). 

Example granulation in a high-speed mixer Scaling-up and other applications... 

With regard to bed weight, forces in fluid beds, and therefore consolidation and granule density, generally scale with bed height. As a gross nfle of thumb, ideally, the power input per unit mass should be maintained with mixer scale-up, related in part... 

A rubber compound has been used to test three simple models on the operation point transfer from a VIC 125 production mixer to a VIC 1.9 laboratory mixer (scale-down). In a second step, the model which gave the best conformity in the rheological and mechanical properties of compoimds and vulcanised specimen has been used for the operation point transfer tests from a VIC 1.9 laboratory mixer to a VIC 125 production mixer (scale-up). Using this model, the rheological and mechanical properties of the rubber compotmds corresponded very well. The rotor clearance variation of the internal mixers proved to be a primary condition to allow this simple scale-up/down model to be successfully applied. 6 refs. 

---