Abstract
This paper will consider the low consistency refining kinetics of a pulp suspension at a given level of applied specific energy. The mechanical treatment on fibres caught in the confined zones of gap clearance (bar crossings) reveals some heterogeneity. It can be experimentally verified that the physical effects on fibres are not the same whether the confined zones are close to the internal radius (input side) or close to the external radius (output side). One must also account for the dynamic sliding motion of the confined zones through the rotation of the rotor plate (or cone) in front of the stator. Hence, each bar crossing has its own sliding velocity.
In order to predict the radial variability of the cutting effect on fibres, through engineering parameters that can be easily determined (radial coordinate; angular velocity; width of bars, width of grooves, average bar angle, both for rotor and stator patterns), a theoretical understanding of the radial distribution of the pressure must be undertaken. The pressure is locally applied on
the pulp pads in confined zones of the gap clearance.
The best homogeneous results are obtained either with a cylindrical or a conical refiner where the bars are parallel to the rotation axis. The degree of variability on the cutting effect on
fibres is increased with an increase of the bar inclination versus the radial direction and a decrease of the ratio between the internal and external radius.
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