Extended Delignification of Kraft Pulping by Anthraquinone, Methanol and Black Liquor, 1996 Pulping Conference Proceedings

Rwaichi J. A. Minja and Per Koch Christensen - NTNU

Størker T. Moe

Norwegian University of Science and Technology (NTNU)

To achieve lower kappa numbers during kraft pulping, either modified cooking techniques or additives are used. Pulping of Norwegian pine by addition of anthraquinone (AQ), methanol (MeOH) or black liquor (BL) and a combination of AQ and BL or AQ and MeOH have been studied. The pulping has been done using 2 liter autoclaves at 170°C and a liquor ratio of 4:1. The results from kappa, viscosity, and pentosan analyses of the pulps suggested that addition of both MeOH and AQ in kraft pulping results in a lower kappa number pulp with higher viscosity. Anthraquinone increases the yield whether added alone or in combination with BL or MeOH. Combination of MeOH and AQ in kraft pulping produces pulps with higher viscosity at lower kappa than a combination of BL and AQ. By addition of MeOH viscosities remain almost unchanged at the same H-factor but because of the faster delignification lower kappa numbers are obtained, hence improved viscosities at given kappa numbers. The oxygen delignification of the pulps were not affected by the addition of the various additives. The tensile index appeared to be improved more by BL than the others while the tear index was maintained by MeOH and lowered more by AQ.