Title: Impacto da densidade básica da madeira de >i<Eucalyptus>/i< na eficiência dos processos de polpação kraft estendidos.
Abstract: Impact of Eucalyptus wood basic density on the efficiency of extended kraft pulping processesThis research aimed to evaluate the influence of Eucalyptus wood basic density on the extended kraft pulping processes.For that, it was used six different genetic materials, chosen of commercial planted forests, from three Brazilian states: E. urophylla x E. grandis (U x G) and E. urophylla x E. tereticornis (U x T) -Maranhão; E. urophylla (Ur) and E. grandis híbrido (HGr) -Bahia; E. grandis x E. urophylla (G x U) and E. grandis (Gr) -São Paulo.These materials were characterized in terms of wood basic density, chemical composition, and fiber dimensions.Then, the materials were subjected to two pulping processes: conventional (C): pulping process reference and extended (E): a simplified laboratory simulation for modified pulping processes.Both processes were carried out targeting kappa number in brownstock pulp of 18±5%, and effective residual alkali concentration between 5 and 8 gNaOH/L.To achieve these premises, the applied alkali charge and the maximum temperature were adjusted.Wood physical characterization showed wood chips basic density values statistically distinct, between 0.416 (Gr) to 0.610 g/cm³ (U x T).The wood with the lowest basic density (Gr) presented chemical properties most favorable to the pulping processes, if compared to the other materials: higher holocellulose content (69.37%), lower extractives content (1.46%), and ash content (0.21%).The wood with the highest basic density showed fibers properties distinct, with a higher wall fraction (60%) and lower lumen diameter (6.76 µm).The variability in woods characterization reflected in their behavior toward the pulping processes, with advantages observed for the extended pulping process in relation to the conventional one: 5.9% average increase in screened yield, 50% average reduction in reject content, 5.7% average reduction in specific wood consumption, 35% average increase in pulp viscosities, and 7.0% average reduction in the black liquor solids, with emphasis on the denser woods.The extended pulping process studied presented itself as a simplified alternative for laboratory execution, and more feasible with the industrial reality when it comes to analyzing woods for pulping.For wood quality studies aiming at pulping production, isolated analysis of the wood basic density is not recommended.