Procedure and arrangement to defibrate fibrous material and use of a defibration drum

摘要

The present invention relates to a method for defiberizing fibrous material, especially recovered paper or recovered board, in a rotary defiberizing drum having a material defiberizing portion and a screening portion. The method comprises following steps: a) a batch of fibrous material and liquid is fed into the defiberizing drum, b) material is defiberized in the defiberizing portion of the defiberizing drum, b) the defiberized material batch is transferred to the screening portion of the defiberizing drum, c) the defiberized material batch is treated in the screening portion, wherein accepted fiber material is separated through the screening surface into accept, and d) the reject material is discharged from the defiberizing drum, and the direction of rotation or the inclination of the defiberizing drum, or both, is changed at least between method steps b) and e). The invention also relates to a defiberizing drum arrangement and use.