Investigation of the fundamentals of fluorescent behavior of kraft-anthraquinone pulping liquors

approved: AN ABSTRACT OF THE THESIS OF Signature redacted for privacy. W J. Bublir The kraft and kraft-anthraquinone pulping processes were used for pulping Douglas-fir chips at 170°C, 180°C and 190°C temperatures. Anthraquinone was added to the pulping liquor at two levels, 0.1% and 0.2% based on wood, to study its effect on pulp delignification at the three temperatures. The fluorescent behaviors of kraft and kraft anthraquinone liquors were related to pulping times, Kappa numbers, and yields. The beneficial effects of anth aquinone decreased as the pulping temperatures increased. Anthraquinone showed the least improvement at 190°C (0% change in yield, -10 points change in Kappa number), while its best effect was shown at 170°C pulping temperature (.6% change in yield, -33 points change in Kappa number), all values relative to kraft cooks at these temperatures. These results suggest that at 190°C, anthraquinone did not stabilize the carbohydrates of the pulp nor the dissolved lignins in the pulping liquor. The fluorescent intensity of the pulping liquor at 170°C was increased by the addition of anthraquinone; but at 190°C pulping temperature, anthraquinone did not show any significant effect on this property. These results suggest that, at 170°C pulping temperature, addition of anthraquinone increased the amount of lignin in the pulping liquor, but at 190°C anthraquinone probably did not prevent the condensation of the dissolved lignin. This was also suggested by the decrease in fluorescent factors with the pulping