Pine Wood Particles Research Articles

Fabricação de chapas de partículas aglomeradas usando gesso como material cimentante.

Neste trabalho, foram confeccionadas chapas aglomeradas, utilizando gesso como material cimentante e papel reciclável dissociado (jornal e offset) e partículas de madeira de pinus como reforços. Em todos os tratamentos, a razão madeira (ou fibras) para gesso foi mantida em 0,25 (base seca) e duas dosagens de água (w) foram empregadas: 0,4 e 0,8, correspondendo à razão água:gesso. As chapas foram prensadas a frio em prensa de laboratório, em um processo similar à produção de chapas aglomeradas convencionais. Após condicionadas em câmara climatizada, as chapas foram testadas em flexão estática, dureza, arrancamento de parafusos, absorção d'água e inchamento em espessura. Em geral, a adição de fibras causou melhoria nas propriedades das chapas. Diferenças estatísticas significativas em relação à testemunha (gesso puro) foram encontradas para resistência à flexão estática (MOR), dureza e arrancamento de parafusos em relação a alguns dos tratamentos estudados. Já a inclusão de fibras de papel reciclável, com w = 0,4, não apresentou diferenças significativas em relação à testemunha para absorção d'água e inchamento em espessura. Os melhores resultados foram encontrados com papel jornal, com um coeficiente w = 0,4.

Propriedades mecânicas de chapas aglomeradas estruturais fabricadas com madeiras de pinus, eucalipto e acácia-negra.

Neste trabalho, foram analisadas as propriedades mecânicas de chapas aglomeradas estruturais, fabricadas com madeiras de Pinus elliottii Engelm, Eucalyptus grandis W. Hill ex-Maiden e Acacia mearnsii De Wild. Buscou-se segregar os efeitos da densidade básica da madeira, instalando-se um experimento no delineamento blocos ao acaso em que taxas de compressão de 1,21, 1,32 e 1,43 constituíram os blocos. Quinze tratamentos onde cada espécie participou com 0, 25, 50, 75 ou 100% de proporção em peso seco, foram utilizados para fabricação de chapas aglomeradas estruturais, com partículas de dimensões médias de 90 x 20 x 0,6 mm e coladas com 8% de adesivo à base de tanino-formaldeído. As análises foram realizadas por meio da correlação e ajuste de modelos matemáticos, obtidos por regressão linear simples ou múltipla, entre as variáveis de produção e a proporção de cada espécie na mistura. Os valores obtidos para MOR e MOE ficaram acima dos padrões de qualidade internacionais, no entanto, as chapas apresentaram baixos valores de ligação interna demostrando baixa qualidade de colagem. Como conclusão geral, a mistura de espécies foi mais vantajosa que a utilização de cada espécie individualmente, principalmente em razão da influência das diferentes densidades básicas de cada madeira sobre as propriedades das chapas. A melhor mistura, porém, tem de ser determinada em razão do uso do produto final e da disponibilidade de matéria- -prima.

Coupled drying and devolatilisation of non-spherical wet pine wood particles in fluidised beds

Release of volatiles of non-spherical pine wood particles was analysed by means of continuous measurements of the CO 2 and O 2 concentrations obtained after the complete combustion of the volatiles and from flame extinction times. The effect of the atmosphere used for devolatilisation was tested. The volatiles' evolution was nearly identical using air or N 2 as fluidising gas. The devolatilisation times increased with increasing the equivalent particle diameter, but there was an important scattering in the results. The data dispersion greatly decreased when the shape factor of the wood particles was considered. The devolatilisation times were fitted to a power-law relation replacing the particle diameter by the equivalent particle diameter multiplied by the shape factor. The effect of the moisture content was studied by analysis of the devolatilisation process of pine wood particles of the same size and different moisture contents (0–50%). As the moisture content of the wood particles increased the devolatilisation rate of combustible volatiles decreased and was more uniform along the devolatilisation time.

Gas formation in the thermal decomposition of large spherical wood particles

Gas formation, weight loss and temperature profiles in the thermal decomposition of relatively large particles of pine wood have been studied. Experiments with spherical particles of different sizes (2, 3 and 4 cm in diameter) have been carried out at two heating rates of the system (5 and 12°C min −1). The existence of significant radial and angular profiles in the particles causes differences in the conversion and in the formation of gases. The experimental yields obtained for the majority gas, CO 2, have been compared with the calculated yields using a model without adjustable parameters. An acceptable agreement has been achieved between the experimental and calculated results.

Temperature profiles and weight loss in the thermal decomposition of large spherical wood particles

The thermal decomposition of relatively large particles of pine wood has been studied. By use of spherical particles of different sizes (2-5.6 cm in diameter), the experimental solid conversion values and the temperature at different points of the solid are analyzed for different heating rates of the system. The experimental results have been compared with those calculated with a simple model, which involves the solution of the heat and mass balances and the kinetic equations, using experimental values as boundary conditions. A good agreement has been obtained for particles up to 4 cm in diameter. For larger particles the mass transfer resistance inside the solid and the existence of secondary reactions may acquire an appreciable importance

Thermal decomposition of lignocellulosic materials: comparison of the results obtained in different experimental systems

An experimental system that allows the use of large particle sizes and the simulation of different operating conditions was built to study the thermal decomposition of lignocellulosic materials. The values of solid conversion and of temperature obtained at different points using spherical particles of pine wood 2 cm in diameter are shown. The conversion values are compared with those calculated from the equations obtained in a thermobalance for small particle sizes.

Single-particle biomass pyrolysis: correlations of reaction products with process conditions

Single, thermally thick particles of lodgepole pinewood were pyrolyzed under well-defined conditions of industrial importance. Particle thickness, heating level, moisture content, density, and grain axis relative to one-dimensional heating were varied using a Box-Behnken experimental design. Gross product fractions, as well as components therein, were measured and the batch yields were correlated with second-order polynomials. The empirical equations correlating the batch yields, together with their prediction uncertainties, are presented and are suitable for use in simulations of wood combustion and thermal conversion. Comparison of large particle pyrolysis product distributions to other studies of small-particle pyrolysis yields shows the trends with particle size to be consistent. Tar yield minima depend on both particle size and heating rate. Gas yield is dependent on both particle size and heating intensity. Because some process controllables were found to alter product yields from large particles in a multiplicative way, rather than an additive way, suggestions for future experiments are made.