Press Section Paper Sheet Rewetting
Paper sheet rewetting appeared in paper machine press section will affect normal paper making, so what’s the reason of press section paper sheet rewetting?
Press Section Paper Sheet Rewetting Reasons
1. Most wet paper/felt interface volumes are filled with water and only partially come into contact with felt and wet paper. Because the wet paper and felt expand on the nip, the air fills the emerging vacuum, and as the air enters the press zone, first is the felt surface, so there have pressure difference, with the interface water into the wet paper, resulting in moisture content of pressed wet paper increased.
2. Capillary forces also can increase wet paper moisture in most papermaking conditions. Because on the nip exit side, a three-phase system of solids, water and air has been rebuilt and the capillaries draw water from the felt surface into the wet paper with finer capillary. This paper rewetting, as long as there is wet paper/felt interface, can also continue to produce paper rewetting after press zone.
3. The rewetting mechanism appears in the water break of paper and felt separation, which can be assumed to be some fine water droplets close to the paper surface, which have a stronger affinity for wet paper than the felt, this water droplets is eaby to produce “rewetting flow” with wet paper in the separation of paper and felt.
