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The impact of the PGW washing stage on bleaching efficiency

Pulp & paper Canada, 1995-01, Vol.96 (1), p.24

Copyright Southam Business Communications, Inc. Jan 1995 ;ISSN: 0316-4004 ;EISSN: 1923-3515

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  • Title:
    The impact of the PGW washing stage on bleaching efficiency
  • Author: Manner, H. (Lappeenranta University of Technology, Finland.) ; Reponen, P ; Alhoniemi, O
  • Subjects: BLANCHISSEMENT ; BLANQUEADURA ; BLEACHING ; LAVADO ; LAVAGE ; MECHANICAL PULP ; mechanical pulps ; PASTA ; PASTA MECANICA ; PATE CELLULOSIQUE ; PATE MECANIQUE ; pressurized groundwood ; PULP ; Pulp bleaching ; Pulp cleaning ; WASHING ; WOOD PULP
  • Is Part Of: Pulp & paper Canada, 1995-01, Vol.96 (1), p.24
  • Description: When the PGW washing stage and neutral papermaking were introduced, the paper brightness target was set at 76 ISO. The favorable effect of the washing stage on the PGW brightness and the bleaching chemical charge is obvious. The dithionite consumption was reduced by an additional 30% and the final PGW brightness was increased by over two ISO points. This indicates that the PGW washing stage increases the brightness by 3.5 points. The effect on PGW brightness and paper brightness due to this development is shown in Fig 8. The target brightness of 76 ISO is achieved with only 55% of the earlier chemical costs. The concentration of detrimental substances in the PM water circulation was reduced considerably after installing the PGW washing stage. The washing stage allows the COD concentration to be cut by about 70% in waters carried over from the PGW plant to the PM. The effect of the washing stage is even more obvious in decreasing the amount of anionic trash. The anionity in PGW was reduced by over 80% in the washing stage. The number of disturbances on the paper machine due to impurities in the PGW decreased after installing the washing stage, reducing the need for wet - end chemicals. The use of fixing agent in PGW was cut considerably. The fixing chemical charge in PGW was reduced to almost zero after installing the washing stage and there is only occasional need to use fixing chemical. The use of talc for pitch control also decreased after installing the PGW washing stage. Abstract: The washing of mechanical pulp can boost the bleaching of pulp. A study of PGW bleaching and the influence of a PGW washing stage on bleaching is reviewed in this report. Objectives were to optimize the operation of two - stage peroxide - dithionite bleaching and to minimize the chemical charge in bleaching of PGW. A comparison between two PGW bleaching lines was done to clarify the effect of a PGW washing stage on bleaching. As a conclusion, it was found that the bleaching chemical charge could be reduced to 65% by introducing the new process arrangements.
  • Publisher: Westmount: Annex Publishing & Printing, Inc
  • Language: English
  • Identifier: ISSN: 0316-4004
    EISSN: 1923-3515
  • Source: AUTh Library subscriptions: ProQuest Central
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