Scale-up of the homogenization process

There can be no doubt that the nd Re) and Ne Re) characteristics as well as the relationship Hi = /(n2, Re) in Fig. 3.11 represent the mandatory source materials for designing stirrers for homogenization processes. Formerly it was often claimed 

This relationship is reproduced in Fig. 3.12a with the test results from Hoogen-dom and den Hartog [220]. It shows that FIs = const applied in the laminar range for several axially conveying stirrer types (helical ribbon stirrers propeller stirrers in a draught tube), i.e. the stirrer power per unit volume, which is required for a particular homogenization time, is here proportional to the viscosity n of the liquid and independent of the tank diameter. FIj and therefore P/D P/V in this range is actually a scale-up criterion for these stirrers. 

In the range 112 IO is no longer constant for these stirrer types, but decreases rapidly only to start strongly increasing again from 112 = 10 see also Fig. 3.12b, from [611]. In general P/V is by no means suitable as a scale-up criterion for homogenization operations. 

The P/ y values given in Table 3.1 for the same mixing time of 6 = 30 s and for a blade stirrer in a tank without baffles for different tank diameters shows the large differences. 

Mersmann et al. [363] determined from the d(Re) characteristics for different stirrer types in different publications those (nd, R ) value pairs, in which the mixing time characteristic in the turbulent flow range changes into a straight line and plotted these values, converted into fli and 112, as can be seen in Fig. 3.13 upper left. 

---