Abstract: A method of manufacturing bleached mechanical and chemithermomechanical pulp is provided, having enhanced bleaching effect, wherein lignocellulose material is passed through at least one preheater or through a chemical treatment system, a steam separator and a refiner where the lignocellulose material is converted into a pulp suspension which, after steam separation, is passed at least to a storage vessel and to a screening department, from which the major part of the pulp suspension is separated as a substantially finished product or is separated and further treated. The reductive bleaching agent is added to the advancing pulp suspension without a bleaching tower. The method is characterized by adding the bleaching agent at a location downstream of the refiner and upstream of the screening department, and by bleaching the pulp under drastic conditions of temperature and minimized oxygen access at the location and immediately downstream of the location.
Type:
Grant
Filed:
March 7, 2000
Date of Patent:
June 15, 2010
Assignee:
Holmen Aktiebolag
Inventors:
Eric Yijing Zhang, Micael Axelfelt, Sverker Bengtsson, Charlotte Wancke Stahl, Johanna Magnusson
Abstract: The content of ray cells in cellulose pulp causes problems and therefore these ray cells should be removed from the cellulose pulp to improve the pulp quality. The present invention makes this possible and comprises a method wherein at first an advancing pulp suspension is screened or vortex cleaned, (3) leading to the formation of an accept pulp fraction (4) and a reject pulp fraction (5) and that the reject pulp fraction is cleaned and divided, and that accepted material (pulp fibres and valuable fine material) is brought to further treatment and/or use.
Type:
Application
Filed:
April 28, 2004
Publication date:
February 1, 2007
Applicant:
HOLMEN AKTIEBOLAG
Inventors:
Christer Sandberg, Carl Nilsson, Per Engstrand