ESACB - Comunicações em encontros científicos e técnicos
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Browsing ESACB - Comunicações em encontros científicos e técnicos by Subject "Acacia melanoxylon"
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- Effect of Acacia melanoxylon wood density on papermaking potentialPublication . Delgado, Carla; Santos, António J.; Simões, Rogério; Anjos, O.In this work we study the behaviour in kraft cooking and papermaking of 6 Acacia melanoxylon wood chip samples, with basic densities of 449, 489, 493, 505, 514 and 616 kg/m3. The wood chip samples were screened and submitted to the kraft cooking process. Experiments were carried out with 1000-g o.d. of wood in a forced circulation digester. The cooked chips were disintegrated, screened and washed. The screened and total yields, kappa number and pulp viscosity were determined according to the standard methods. The morphological properties of pulp fibres were determined by image analysis of a diluted suspension in a flow chamber in Morfi®. The unbleached kraft pulps were submitted to a bleaching D0E1D1E2D2 sequence and their papermaking potential evaluated. The pulps were beaten in a PFI mill at 500, 2500 and 4500 revolutions under a refining intensity of 1.7 N/mm. Paper handsheets were prepared according to the Scan standard and tested regarding structural, mechanical and optical properties. Regarding the pulping potential, the pulp yield ranged between 47.7 and 57.7%. The selected wood samples provided bleached kraft pulps with markedly different biometrics characteristics. In fact, the mean values of fibre length, fibre width and coarseness ranged between 0.77 and 0.98 mm, 17.8 and 19.4 μm, 4.8 and 6.2 mg/100m, respectively. As expected, these biometrics characteristics have very high impact on paper structure, including smoothness, and on mechanical and optical properties, for the unbeaten pulps. At a given beaten level, the differences between pulps remain very high. Moreover, for a given paper density, tensile and tear strength, and light scattering coefficient are significantly different. To reach a given paper density, however, the different pulps required very different energy consumptions in beating.
- Influence of wood basic density on acacia melanoxylon kraft processPublication . Santos, António J.; Simões, Rogério; Anjos, O.Wood density is a complex physical property related to the anatomical structure and the chemical composition of wood and one of the most important wood quality factors. Sampling was based on a total of 20 trees from four sites in Portugal that were harvested at a sawmill diameter class of 40 cm and wood discs taken at different height levels from the base to the top of the tree. The mean basic density of the Acacia melanoxylon trees measured at 5% height level (near breast height level) was 516 kg/m3 with a 34 kg/m3 standard deviation. The within-tree axial variation of density was of small magnitude, but showing higher values at the stem base and top. Site had no influence on the basic density of the wood. Overall the between tree variation of density was small possibly linked to the narrow genetic diversity of this introduced exotic species. In the Kraft process we can observe variability between stands and an increase of the pulp yield, and fiber width and length with the higher level in the tree. The wood basic density is well correlated with the ISO brightness and well correlated in inverse order with the pulp Yield and fiber width and length. The kappa number don’t present a great variation with the wood basic density.
- Paper making potential of Acacia dealbata and Acacia melanoxylonPublication . Santos, António J.; Anjos, O.; Simões, RogérioThe pulping and papermaking potential of Acacia dealbata and Acacia melanoxylon were studied using Eucalyptus globulus as a reference. Pulp yield, alkali consumption and delignification in the kraft process, of both species, compare very well with the reference. Pulp yield can be higher than that of E. globulus and the residual lignin content lower after cooking, which is in good agreement with the lower lignin and extractives content of the wood samples used. Pulps produced from Acacia have slightly lower fibre length and coarseness and higher fibre width and wet fibre flexibility than E. globulus pulps. As a consequence of fibre characteristics, the paper produced from Acacia is denser and exhibits higher tensile and burst strength, and lower tear resistance than that from E. globulus, at a given PFI revolution.
- Prediction of blackwood wood and pulp quality parameters using NIR-PLS-R spectral modelling : wavenumber ranges and smoothing pointsPublication . Pereira, Helena; Santos, António J.; Anjos, O.Prediction of blackwood wood and pulp quality parameters using NIR-PLS-R spectral modelling : wavenumber ranges and smoothing points.
- Pulping characteristics of Acacia melanoxylon wood as an exotic species in PortugalPublication . Santos, António J.; Simões, Rogério; Pereira, Helena; Anjos, O.Pulping characteristics of Acacia melanoxylon wood as an exotic species in Portugal
- Relation between wood density and paper properties of some hardwood speciesPublication . Santos, António J.; Simões, Rogério; Anjos, O.Relation between wood density and paper properties of some hardwood species.
- Utilização de tecnologia NIR-PLS-R como ferramenta de predição - parâmetros de qualidade da indústria celulósica.Publication . Santos, António J.; Anjos, O.A espectroscopia de infravermelho próximo (NIR) tem revelado interesse no desenvolvimento de métodos de análise expeditos e de baixo custo ao nível da composição química, propriedades físicas, mecânicas e anatómicas de materiais de madeira. A maioria dos trabalhos de investigação e divulgações técnicas com a utilização da NIRS para ciência e tecnologia da madeira encontram-se publicados entre 2006 e 2013. Nos últimos 25 anos só os Estados unidos, Japão, Austrália e China contribuíram com 314 publicações enquanto Portugal deu o seu contributo com 18 publicações. Com base em 120 discos de madeira de Acacia melanoxylon, pertencentes a 20 árvores de quatro locais em Portugal (1-2), foram estabelecidos modelos em NIRPLS-R para diversos parâmetros de qualidade (3-4), para a mesma amostragem de madeira. Os modelos obtidos permitiram estimar parâmetros de qualidade como a massa volúmica básica da madeira (2), rendimento em pasta, índice Kappa (4) e brancura ISO (5) de pastas cruas Kraft; e ainda a morfologia das fibras celulósicas (largura e comprimento ponderado em comprimentos das fibras). Os indicadores de qualidade da validação cruzada dos modelos, apresentaram uma variação de 79.0 a 98.9 % para o coeficiente de determinação; utilizando 3 a 9 componentes principais para explicar a variação encontrada para cada um dos parâmetros de qualidade em estudo; e um desvio residual de previsão (RPD) a variar entre 2,2 a 9,5. Todos os modelos utilizaram processos derivativos como pré-processamento (3-4). Os resultados dos modelos NIR-PLS-R demostraram que através da mesma informação espectral de madeira moída de Acacia melanoxylon, pode ser utilizada para prever uma grande variedade de parâmetros, tais como o rendimento em pasta, a largura e o comprimento ponderado em comprimentos das fibras; enquanto a informação espectral das pastas cruas permite obter a informação ao nível do índice Kappa e a brancura ISO das mesmas.
- Vessel morphological evaluation of Acacia melanoxylon woodPublication . Rodrigues, Catarina; Santos, António J.; Tavares, Mário; Anjos, O.In this paper we analyze the transversal variation of Acacia melanoxylon R. Br. wood porosity, using five trees with 40cm dbh collected in the Ponte de Lima region, in northwestern Portugal. Variation of porosity, vessel area, width and density were used to evaluate tree vessel variation, in order to relate it with other wood properties. Each value of these variables represents a mean of 60 vessels measurement. We collected five wood disks at the bottom, 5, 15, 35 and 65% of total height, and commercial top of those five trees, in order to acquire three radial cores at 10, 50 and 90% near the pith, and in north and south directions. We found great variability along the tree concerning the axial and radial positions. Porosity is higher near the bottom and lower at the top; vessel number varies inversely. Vessels width and density are similar at the different height levels. Radial variation show that porosity, vessel area and vessel width all increase, and density decreases, with distance to the pith. Principal components analysis was used to investigate the differences in vessel characteristics and levels in the trees, as well as their interaction. This methodology allowed us to determine how close, or how independent, the study variables were. We conclude there is a group of vessel morphologic characteristics which depend strongly on each other – porosity and vessel area and vessel number are negatively correlated with the other. The variation between North and south direction is not significant, because the values are very similar and the trees don’t present a higher eccentricity.
- Wood potential use of Acacia melanoxylon growing in pure or mixed stands with Pinus pinaster by the portuguese forest industryPublication . Santos, António J.; Teixeira, Andreia; Anjos, O.; Simões, Rogério; Nunes, Lina; Machado, José S.; Tavares, MárioWood potential use of Acacia melanoxylon growing in pure or mixed stands with Pinus pinaster by the portuguese forest industry.