Method for recovering fiber from screening reject and fine sorting pre-processing device for use in method for recovering fiber

A method for recovering fiber from screening reject in recycling of waste paper, comprising the steps of:

• feeding into a fine sorting pre-processing process a first screening reject that has been gained in a coarse sorting process, using a fine sorting pre-processing device configured to have an environment wherein heat of 90° C. or higher is generated through friction between fibers and sticky foreign material is softened so as to be expandable and contractable in order to progress the detachment of sticky foreign material from fibers and the granulation and balling up of the detached sticky foreign material via kneading of the sticky foreign material;
• afterwards, discharging resulting material from the fine sorting pre-processing device, and
• after discharging, feeding the resulting material from the fine sorting pre-processing device into a fine sorting process, wherein the balled-up sticky foreign material is separated as a second screening reject such that fiber is thereafter recovered, the device comprising:
• a cylinder body of which a direction of axis is horizontal;
• a rotating shaft that is provided within the cylinder body in the direction of the axis so as to be rotatable around the axis;
• a group of rotating blades attached to the rotating shaft;
• and a group of stationary blades provided so as to protrude from the inner surface of the cylinder body towards the axis, wherein
• rotating blades in the group of rotating blades are diagonal relative to the rotating shaft as viewed in the direction of the axis, and the group includes feeding blades and retrieving blades of which phases shift from each other in such a manner that planes of the blades cross each other,
• stationary blades in the group of stationary blades are located in one space between adjacent rotating blades after another as viewed in a direction that is perpendicular to the direction of the axis as the rotating blades rotate,
• a successive change in a positional relationship between the rotating blades and between the rotating blades and the stationary blades due to the rotation of the group of rotating blades progresses the detachment of the sticky foreign material from the fibers that are included in the first screening reject hit by the blades and the granulation and the balling up of the detached sticky foreign material by kneading the detached sticky foreign material, and
• in the fine sorting pre-processing device, both the rotating blades and the stationary blades are formed of quadrilateral plate-like bodies.