Refiner segment

A refiner segment for a refiner of lignocellulosic material, the refiner segment being part of a refiner disc comprising a center area, wherein the refiner segment comprises:

• a number N, N≥2, of bar zones (Zi, i=1, . . . N) arranged at different radial positions with regard to a radial direction R extending from said center area of said refiner disc towards a periphery of said refiner segment, each of said bar zones (Zi) being defined by a corresponding set of refining bars (ZiRBi, i=1,. . . ,M) distributed angularly and encircling the center area, where refining bars (ZiRBi) belonging to different but neighboring bar zones (Zi, Zi+1) are angularly offset, wherein refining bars (ZiRBi) belonging to different but neighboring bar zones are arranged in such a way that a tangential direction of a particular refining bar (ZkRBk) belonging to a bar zone (Zi) points in a direction towards the mid-point between two refining bars (Zk+1RBk+1) belonging to a neighboring bar zone (Zi, Zi+1) and wherein a length of refining bars belonging to different bar zones decreases from a largest length for refining bars (Z1RB1) belonging to an innermost bar zone (Z1), with regard to the center area of said refiner disc, to the smallest length for refining bars (ZNRBN) belonging to an outermost bar zone (ZN) adjacent the periphery of said refiner segment,
• wherein each refining bar has a feeding angle greater than 0 degrees and less than or equal to 60 degrees, the feeding angle being an angle between a radial direction of the refiner segment and a length direction of a respective refining bar, and wherein the bar zones are distinct and separate from each other, and each refining bar is disposed in a single respective bar zone, and
• wherein between the refining bars are open areas that extend continuously from the center area of the refiner disc to the periphery of the refiner segment.