A Study of Hydro-Mechanical in Disk Refiners with Low Concentration

The purpose of this article is to propose an overall description of the hydro-mechanical forces that take place in the crossing areas of the bars in the gap clearance of a refiner. This description can apply to conical refiners as well as to disk refiners in the low consistency domain of pulp suspension, i.e. between 2 and 6%. On the one hand, with the help of the measurement of the axial force exerted on the shaft of rotor, it is possible to quantify the intensity of the normal reaction force that the compressed suspension exerts on the bar. On the other hand, considering the net power consumed resulting from the suspension friction against the bars, we provide a theoretical justification of an empirical expression, proposed by BANKS in 1967, and the determination of the net tangential force in these conditions. Then, the so-called coefficient of friction may be defined and calculated without any ambiguity. Its evolution, in terms of refining kinetics of the pulp, may be interpreted by analogy with the pressing process. As the refining proceeds, the regime extends continuously from solid/solid to solid/liquid friction of the pulp suspension against the bars. A deeper insight is thus obtained to explain the complex physics that occur in the gap clearance of refiners.