ANTHRAQUINONE -A SIMPLE APPROACH FOR EXTENDED DELIGNIFICATION IN CONVENTIONAL KRAFT PULPING, 2002 Kraft Pulp Yield Anthology

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The effect on pulp yield and strength properties of extending the delignification in kraft pulping conditions by using a higher H-factor, increasing the alkali charge, or by addition of anthraquinone,was investigated. It was found that delignification could be extended by only 15% using a 27% increase in H-factor with 2% decrease in pulp yield. An 11% increase in effective alkali resulted in a 24% reduction in kappa number, but also with lower yield. Increasing the H-factor at higher alkali charge failed to reduce the kappa number any further. Addition of 0.1% anthraquinone at standard pulping conditions (1720 H-factor, 16% EA, 30% sulfidity) resulted in a 24% reduction in kappa number without an increase in alkali charge or H-factor and resulted in a 2% pulp yield increase. Lowering the kappa number from 30 to 22 by these methods of extended delignification did not affect the strength properties. Anthraquinone extended delignified pulps were as strong as the reference pulp, and by virtue of their lower kappa number could be bleached to the same brightness levels with 26% less active chlorine charge in the chlorination stage. Fully bleached anthraquinone pulps and reference pulps were found to be virtually identical in strength properties.