Abstract: Process and device to manufacture and dewater cellulose pulps in which defibered cellulose is screened to remove shives, fractionated in to at least three fractions (10, 3, 12), which fractions are treated each by itself and then are brought together completely or partly, and that the fractionation is done according to specific surface, preferably with hydrocyclones, and that the process comprises process stages (6,7) that fractionates out fibers with high specific surface, preferably thin-walled fibers, and that the process comprises process stages (2) that fractionates out fibers that have lower specific surface, preferably fibers with thicker fiber wall, and that one or several fiber fractions (3, 3a) are treated, to be split, fibrillated and permanently collapsed, preferably with a refiner, ball mill or similar.