Modeling of sapwood and heartwood delignification kinetics of <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> using consecutive and simultaneous approaches |
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Authors: | Ana Lourenço Jorge Gominho Helena Pereira |
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Institution: | 1.Centro de Estudos Florestais, Instituto Superior de Agronomia,Universidade Técnica de Lisboa,Lisbon,Portugal |
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Abstract: | Eucalyptus globulus sapwood and heartwood were delignified at 130°, 150°, or 170°C by kraft pulping. Pulp yields of heartwood were lower than
those of sapwood (46.5% vs. 50.4% at 170°C). Delignification was modeled using consecutive and simultaneous kinetic models.
The modeling was similar for heartwood and sapwood, and either approach could be used, with both yielding good correlations
between experimental and model data. The consecutive model identified two delignification phases with similar reaction rates
and activation energies for heartwood and sapwood at 150° and 170°C. At 130°C only one phase was identified. Three reactive
types of lignin fractions were identified using the simultaneous model, without differences between heartwood and sapwood.
Their reaction rates were 0.152, 0.138, and 0.003 min−1 at 170°C, and the activation energies were 132, 119, and 102 kJ.mol−1. The presence of heartwood did not influence the kinetic development of delignification. The negative impact of heartwood
in pulping is related to the higher content of extractives (9.8% vs. 3.9% in heartwood and sapwood) and to their influence
on the process, namely in the heating-totemperature phase when a substantial mass loss occurs (30% vs. 20% for heartwood and
sapwood). |
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