Browsing by Author "Kleppe, Peder J."

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    Improving the Pulp Yield by Using Ps/Aq And/Or Two Stage Oxygen Delignification
    (1998) Minja, Rwaichi J. A.; Moe, Størker T.; Kleppe, Peder J.
    The effect of polysulfide (PS) and anthraquinone (AQ)addition on kraft cooking is investigated together with oxygendelignification of the high-yield PS/AQ kraft pulps. Additionof polysulfide and AQ increases pulp yield. The yield benefitis considerably lowered when cooking to kappa numbersbelow 27-28. Oxygen delignification to about 55%delignification preserves the yield increase attained by PS/AQaddition. For two-stage extended oxygen delignificationbeyond 55% kappa decrease , the yield increase is lowered.Peroxyacetic acid “activation” of the pulp followed by asecond oxygen stage also lowered the yield significantly.From the data presented, optimal yield for bleached pulpwould be reached when cooking with PS/AQ addition tokappa numbers between 40 and 45, followed by oxygendelignification to kappa numbers around 22. This could thenbe followed by bleaching with more selective bleachingchemicals like ozone and/or chlorine dioxide.
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    Modified Polysulphide (Aq) Pulping Of Softwood
    (1997) Minja, Rwaichi J. A.; Kleppe, Peder J.; Karlsen, Trond
    A review of the polysulphide (PS) liquor generation methods has been made. By preparing some PS liquors which simulate future possibilities, pilot scale PS-(AQ) pulping studies were conducted. The studies were carried out in a recently acquired pilot plant which can simulate both conventional cooking techniques as well as the latest pulping developments. Two types of pulps were made, type 1 were liner board grade pulps and type 2 were bleachable grade pulps. Type 1 pulps were made by using up to 20% green PS-liquor in conventional PS-AQ pulping. Type 2 pulps were made by adding all PS in the impregnation stage of ITC simulated cooks and applying either NaOH (Soda liquor) or kraft liquor (WL) as the major alkali source.
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    The Possibilities to Apply Polysulphide-Aq Pulping in Kraft Mills
    (1998) Kleppe, Peder J.; Minja, Rwaichi J. A.
    Developments in polysulphide pulping during the last 35 years are reviewed with emphasis on the successful PSpulping experience at the Peterson kraft mill in Moss, Norway. New and economical PS generation technology not disturbing the Na/S-balance in kraft mills will enhance application of PS-pulping world wide. Multi-stage PSpulping may improve the yield increase for a given PSsulphur charge to a digester system. Especially PS-black liquor impregnation followed by kraft cooking with conventional white liquor is interesting. Drying of fresh wood chips before PS-AQ pulping has a negative effect on obtainable yield increase. The paper and board making properties of polysulphide-AQ pulps are comparable to kraft pulps from a given wood source. PS-AQ paper grade pulps seem to preserve their paper making properties by recycling better than kraft pulps containing less hemicelluloses.