Mixed Brazilian Eucalyptus and Pinus Species - Bleaching Evaluation, 2008 Engineering, Pulping and Environmental Conference

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Eucalyptus fiber is shorter in relation to softwood species. These short fibers are useful in improving paper formation, but strength properties are better when long fibers are used. Most Brazilian pulp production uses eucalyptus species as raw material. Pulp production from softwood is concentrated in the south of Brazil due to the suitability of its climate for growing pine species. Looking for the possibility of obtaining pulp with adequate properties for formation and strength, this paper analyzes results of kraft pulp bleaching by the (OO)(AD)EopDP bleaching sequence, using pulps produced with mixtures of Eucalyptus grandis x Eucalyptus urophylla hybrid and Pinus taeda wood chips, and Eucalyptus globulus and Pinus taeda wood chips. Target brightness was 88.5 ± 1 % ISO. Chlorine dioxide consumption of the Eucalyptus tested was around 10 kg ClO₂/odt. For the mixtures of eucalyptus and pine in the proportions of 10% up to 50% pine, it varied from 11.2 up to 16.2 kg ClO₂/odt, increasing as the proportion of pine wood chips increased in the mixtures. Hydrogen peroxide consumption varied from 5 to 8 kg H₂O₂/odt for the pulps analyzed. Total active chlorine consumption for Eucalyptus globulus was 40.4 kg/odt, while for the Eucalyptus grandis x Eucalyptus urophylla hybrid it was 41.1 kg/odt. In the mixtures it varied from 41.9 up to 64.5 kg/odt, the consumption of the mixture of the Eucalyptus grandis x Eucalyptus urophylla hybrid and Pinus taeda being higher. For Pinus taeda, active chlorine consumption was 76.5 kg/odt. Viscosity values had a tendency to decrease as the proportion of pine increased in the mixtures. Brightness reversion varied from 1.7% to 2.5% ISO in the mixtures. In conclusion, manufacturing units that want to produce a differentiated kind of pulp with a high resistance to tearing, to get higher productivity from paper machines, or even to produce special, low-gram papers, must consider the addition of small proportions of Pinus to Eucalyptus.