US Patent 7736463 Method for manufacturing bleached mechanical and chemithermomechanical pulp

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.