Evaluation of mixtures of pine and eucalypt wood for the production of bleached kraft pulp

Blending wood species can combine complementary fiber attributes in a single pulp. This study evaluated kraft pulping of Pinus sp . and Eucalyptus sp. chip mixtures and the bleachability of the resulting pulp. Pulping was performed to reach Kappa 20 ± 1 using eucalypt/pine blends at 90/10, 80/20, 70/30, and 60/40 (oven-dry mass). A 100 % eucalyptus pulp served as the Reference. All pulps were bleached with an ECF sequence. As pine proportion increased, the H-factor rose from 481 (Reference) to 1,170 at 40 % pine. Brown pulp viscosity showed a decreasing trend with increasing long fiber content. Bleaching reacted in such a way that pulps with higher long fiber content and lower bleachability required higher active chlorine loads. Overall, kraft pulping of these mixtures proved technically feasible. However, these operational trade-offs should be weighed against potential property gains from longer fibers, so that chip-mix strategies can be tuned to balance product performance with pulping and bleaching.