(431h) Characterizing the Mixing Efficiency of the Planetary Powder Mixer Triaxe® Through An Extended Power Consumption Study

While mixing
processes have been largely employed in industry since a long time, a need of
comprehensive studies of these processes is recently growing. Indeed modern materials are frequently performed in very tight intentions,
especially in high added-values industries. It is usual to find formulations
containing several tenths of ingredients, but for which end-use properties
finally depend on the efficiency of a single mixing step.

Fig 1: Triaxe®
mixing system

Planetary mixers take
a large place among the proposal of equipment manufacturers. The combination of
several motions ensures interesting mixing conditions and allows the mixer to be
adapted to a wide range of raw material properties. The Triaxe® mixing system
combines a gyration motion and a rotation motion of an impeller across a
spherical tank, as shown in fig. 1. Previous studies from our group enhanced
the versatility of this mixer, being able to achieve mixing of free-flowing or
cohesive materials in a short mixing time. For a given product, mixing time and
power consumption depend on gyrational and rotational speeds of the impeller. A
characteristic speed, corresponding to the maximum tip speed of the impeller
for given gyration and rotation conditions, is defined and its versatility is
demonstrated. It is concluded from mixing and power consumption experiments
that this speed governs agitation and mixing of free-flowing powders. In
addition, some correlations involving dimensionless Power numbers and Froude
numbers deduced from this characteristic speed are highlighted. This is enlarged
to account for powders of very different flow characteristics, as well as their
mixtures.