D - Textiles – Paper – 21 – C
Patent
D - Textiles, Paper
21
C
8/78
D21C 9/10 (2006.01) D21C 9/02 (2006.01)
Patent
CA 2033855
Abstract The invention relates to a process for countercurrent washing and bleaching of a pulp from chemical pulping (1). The pulp is washed on the washing line (2-5) countercurrently with hot water, the filtrate being ultimately directed to evaporation and to chemicals recovery, and the pulp thus washed is further after-washed (6) with warm water before being directed to the bleaching line (7-11), which has successively a chlorine - chlorine dioxide step (7), an alkali step (9) and a final bleaching (11), the bleached pulp being washed after each of the above bleaching steps. According to the invention, after the chlorine - chlorine dioxide step (7) and the alkali step (9) so much filtrate is removed from the washed pulp, for ex- ample, by pressing, that the solids content of the pulp will be at least 30 %, and at least a portion of the filtrate thus obtained is directed to the last step (5) of the countercurrent wash as its first washing water, which is displaced with the said hot water before the after-wash (6).
Cassan Maclean
Jaakko Poyry Oy
LandOfFree
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