Effect of eucalyptus bark contamination during pulping of mixed southern hardwoods, November 2016 TAPPI JOURNAL

ABSTRACT: The use of eucalyptus as a partial replacement for mixed southern hardwoods can result in signifi-cant amounts of eucalyptus bark being incorporated into the chips going to the digester. When eucalyptus is first harvested, the bark peels off in large sheets, which will pass through chippers designed for southern hardwood. After being cut for more than about 4–6 weeks, the bark tightens onto the bole of the tree and again passes through chippers not designed for eucalyptus. As a result, significant quantities of eucalyptus bark could go to the digester. This study describes the effect of pulping eucalyptus bark in the laboratory. A series of control studies were per-formed on eucalyptus and mixed southern hardwood bark. The results show that incorporating bark into the cook results in increased kappa number, decreased pulp yield, and increased alkali consumption. If the percentage of applied active alkali is increased to counteract the increased alkali consumption, increased hexenuronic acid is generated,

Application: These data could be used to help justify in-woods debarking of eucalyptus to avoid contamination issues or to predict potential operational problems associated with partial substitution.

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