(400x) Fluidized Bed Rheology I - Fundamentals

Authors: 
Schütz, D., Anton Paar
Riedl, E., Anton Paar Gmbh
Hartmann, K., Anton Paar Gmbh
Shetty, A., Anton Paar USA
Recently Anton Paar released the Powder Cell for MCR Rheometers , this device is capable of high performance measurements with large ranges of shear rate and shear stress, as well as oscillation measurements for the first time in gas-fluidized beds. Being able to measure extremely small torques (+- 10 nNm) in a reproducible manner enables a proper rheological study of fluidized beds in the style of complex fluids.

Unsurprisingly the behavior of fluidized beds mirrors that of complex fluids (e.g. suspensions) in some regards, while still showing a large influence of the particulate matter itself but also presenting wholly unique phenomena.

Direct measurements of apparent viscosity, defluidization/deaeration rates in rotational as well as oscillatory manner will be discussed. Comparisons of multiple conventional concentric cylinder geometries for apparent viscosity measurement system based on the Stokesian surface viscosity relation will be demonstrated and discussed.

In this talk we will present multiple results from multiple Geldart groups and grain sizes/distributions as well as explore the underlying physical phenomena that govern the behaviour of fluidized and collapsed beds especially between incipient and full fluidization.