| 摘要 |
PROBLEM TO BE SOLVED: To reduce the COD and chromaticity load in a bleaching drainage generated from the bleaching process of a kraft pulp in a paper-making plant. SOLUTION: In the case of carrying out multistage bleaching of a digested pulp in the production of a bleached kraft pulp by an ECF bleaching method, a bleaching step with chlorine dioxide is placed after an ozone bleaching step without using an alkali-extraction step after the ozone bleaching step. Preferably, a bleaching process composed of a combination of a chlorine dioxide bleaching step and a hydrogen peroxide bleaching step is carried out after the ozone bleaching step. Preferably, an acid treating process is carried out after the ozone bleaching step. COPYRIGHT: (C)2008,JPO&INPIT
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