Kraft cooking characteristics and hexenuronic acid concentration of pulps from Eucalypt and other hardwood species

Fifteen different hardwood species have been investigated with regard to their kraft cooking characteristics. Firstly, all the species were cooked to a reference kappa number of 16.4+/-1.0. The evaluation of the results includes cooking yield, viscosity, xylan content and hexenuronic acid concentration. The difference between the different species is very large in many respects. In a second part of the study, ten Eucalypt species were cooked under identical conditions. Interestingly, the species yielding pulps with the highest kappa numbers also showed the lowest cooking yield, which emphasizes the importance of the choice of Eucalypt species when a forest is planted for pulping purposes. In a third part of the investigation, the mechanisms determining the concentration of hexenuronic acid in a pulp are discussed and exemplified with trials on Oak and Birch.