ABSTRACT
This work studies the technical viability of using mixtures of sawmill residues (slabs and others) and tree tops of 15 years old, with industrial wood chips, 7 years old, Eucalyptus grandis in the production of kraft pulp. Models were prepared to estimate total and commercial heights and commercial volumes adequate to sawing, all based on DBH. Anatomical data, wood densities and chemical composition of these mixtures are provided. The study shows that it is technically viable to perform kraft delignifications with these mixtures. The use of sawmill residues results in a fast yield loss but the pulp produced under the same conditions yields lower Kappa number than that obtained with 7 year-old Eucalyptus grandis. The delignification of tree tops results in the loss of gross yield, but the specific wood consumption is smaller. As the wood of tree tops increase, there is an increase of the wood density, the fiber average length remains practically the same and a small increase is obtained in the lignin content, but there is a decrease of extractives in ethanol, in hot water and in the solubility in NaOH 1%. The gross yield in pulp decreases slightly, but does not practically affect the Kappa number, the specific wood consumption falling sensibly. The sawmill residues increase in the mixtures practically does not affect the wood density, but the fiber average length increases, also with a small increase in lignin content. Extractives in ethanol, hot water and the solubility in NaOH 1% decrease. The gross yield in pulp falls a lightly, but with a significant fall in the Kappa number, without practically affecting the specific wood consumption. In short, for the same Kappa number, cooking conditions can be less drastic to obtain the same final result, since it possibly means a reduction in reagent consumption during the process. And as the fiber average length showed a small increase, the resulting pulp will certainly yield a higher mechanical resistance and consequently, a better quality paper.
Key words:
Eucalyptus grandis; forest residue; residue; kraft pulping