Importance

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Abstract

A method and apparatus is provided for controlling the effect of centrifugal force on pulp stock while being ground in the grinding space of a defibrating apparatus defined between a pair of grinding discs which rotate relative to one another in a fluid environment under superatmospheric pressure and corresponding elevated temperature. The grinding space includes a central portion, a first outwardly extending grinding space and a second outer grinding zone extending at an inclined angle from the first grinding zone. Pulp stock to be ground is introduced into the central portion and accelerated through the first and second grinding zones by centrifugal force generated by the rotating discs. The inclined grinding zone serves to split the centrifugal force into a vector perpendicular to the direction of flow of the pulp material and a vector aligned with the axial flow to reduce the accelerating force on the pulp grist in the direction of outward flow. By reducing the outward acceleration, the dwell time of the grist in the second grinding space is increased, resulting in optimum utilization of the entire grinding space for optimum refining efficiency.

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First Claim