High-shear mixers advantages

In order to combine the advantages of a batch type and continuous production, a prototype for a quasi-continuous production line was developed (15-18,33-35). The principle of this quasi-continuous production line is based on a semi-continuous production of mini-batches in a specially designed high-shear mixer/granulator which is connected to a continuous multicell-fiuidized (Glatt Multicell ) bed dryer (Fig. 10). 

It is well recognized that extensional flow is advantageous to deform and break up droplets with large viscosity difference. As shown in Fig. 7.9 [22], shear flow can lead to the droplet break-up only under the condition of a viscosity ratio of up to 3.8. This suggests that one should utilize sufficient extensional flow as well as high shear flow [22]. For this reason, the simulation of extensional flow to obtain the optimum screw design and the use of an additional, extensional mixer are considered as significant tools [23]. 

In double-screw mixers, the screws normally rotate in one direction at the same speed, an advantage ensuring a high rotational speed and increasing a shearing force and the output of the entire machine. 

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