| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 98 === The pulp industry was trying to change and improve the old bleaching sequences to decrease the dosage of bleaching chemicals and environmental pollution furthermore increase the pulp properties. Currently the most important application of enzymes is in the pre-bleaching of kraft pulp. Xylanase enzymes have been found to be most effective for that purpose.
The purpose of this study was to investigate the effect of xylanase (Pulpzyme HC) pre-treatment and oxygen bleaching time on Eucalyptus globules kraft pulp. Unbleached pulps, divided into low kappa number and high kappa number, were pre-treated with xylanase (10 IU/g of oven-dried pulp, 65oC) before oxygen delignification stage. After varying oxygen bleaching time, ranges from 0, 15, 30, 45, and 60 min and the temperature maintained at 99oC, it enhanced the removal of the kappa number of low and high kappa number pulps after 60 min reaction, besides, the viscosity of those can be enhanced to 6.4o/o and 1.3o/o at final oxygen delignification, respectively; the residual lignin can be removed 17o/o and 13o/o, respectively. Besides, it enhanced the bleachability and selectivity of pulp.
The removal of hexenuronic acid (HexA) has attracted a lot of concerns, because HexA will react with potassium permanganate so that increase the consumption of bleaching chemical agents. The HexA contents in the low kappa number and high kappa number contribute kappa number about 18.0o/o and 13.1o/o. The result showed that the dosage of bleaching agent will be reduced as the removal of hexenuronic acid.
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