Upgrading of TMP to an SC/LWC quality

摘要

Described are processes for production of upgraded TMP to SC/LWC qualities. The newsprint pulp is pumped to an LC-refiner (1) in which the average fibre length is reduced, and is then transferred to a primary screen (2) in which the pulp is divided into a primary accept and a primary reject with the aid of a slotted screen basket which has a narrow slot width. The primary accept is transferred to the main line, where the primary reject is dewatered and then refined in an HC-refiner (3). The refined primary reject is then transferred to a second screen (4) in which the reject is divided into a secondary accept and a secondary reject with the aid of a slotted screen basket which has a narrow slot width. The secondary accept is returned to the main line and mixed with the primary accept from the primary screen.