(215i) Fluidized Bed Rheometry – Science, Practice and Industrial Applications

The rheological behavior of fluidized beds has been an object of study ever since their first technological use in the 1940´s.

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.

For the first time it is possible to directly correlate the airflow through particulate matter to their apparent viscosity (via both Bingham and Stokes assumptions) and therefore reliably measure this value with multiple geometries.

Oscillatory measurements show the gradual decline of elastic behaviour and emergence of a wholly viscous behaviour as soon as the pseudofluid (fluidized bed) forms fully.

While exhibiting some wholly unique effects, the shear rate dependent behaviour of a gas fluidized bed can be for the most part be likened to that of particulate suspension. Effects such as solid fraction dependence, jamming are found and demonstrated in fluidized beds as well.

This provides new avenues for the development/improvement for a multitude of industrial processes.