Process Development Division, Session T5003

Aiche Fall Meeting November 12-17, 2006

The flow pattern in an impeller type mixing system is a complex mixture of shear rates, (macro, micro, and nano scale) as well as a variety of blend times and flow patterns. Basic fluid mechanics research has given much basic information about these parameters. However, in an actual process, there is often no information about which of these parameters may be very important, and which of them are not a factor.

Geometric similarity controls no mixing parameter what so ever and in fact there may be good reason to use different geometric impellers in pilot and plant scale. The size of the pilot scale tank is important and also whether a batch pilot plant tank is to be scaled up to a continuous flow tank.

The Reynolds number around the impeller is normally lower in pilot scale than it will be in full scale.

Examples of how to practically characterize these parameters will be offered.