METHOD OF PRODUCING BLEACHED THERMOMECHANICAL PULP (TMP) OR BLEACHED CHEMITHERMOMECHANICAL PULP (CTMP)

摘要

There is a need for a cheaper method of producing bleached TMP and CTMP without impairing the properties of the pulp. This is made possible by the present invention, which relates to a method of producing said pulps in whic h finely divided lignocellulosic material is defibrated after pretreatment and the resultant pulp is bleached in the form of a suspension with bleaching agent that increases the anionic charge of the pulp fibres, whereafter the pulp suspension is cleaned and then possibly further treated, for instance bleached, characterised in that the defibration is effected with the aid of a) a refiner that has counter-rotating refining discs while using an extra high temperature (HTDD), or b) a refiner that has a single rotating refining disc(s) having a single refining zone or two parallel refining zones, while using an extra high temperature and while rotating the disc(s) at an extra high speed (RTS), and in that the cleaning treatment comprises first screemi ng the pulp suspension and them hydrocyclone cleaning said suspension, wherewit h the reject obtained with each cleaning process is treated individually and t he treated reject is returned to the advancing pulp suspension.