ResumoO presente trabalho teve como objetivo avaliar os efeitos de diferentes níveis de desbaste nas propriedades físicas e químicas da madeira e do carvão vegetal de híbrido de Eucalyptus urophylla W. Hill ex Maiden x Eucalyptus grandis S. T. Blake. O experimento foi instalado em um talhão de uma empresa do setor florestal, que foi dividido em quatro faixas, representando os níveis de desbaste de 0, 20, 35 e 50% aplicados ao povoamento aos cinco anos. Foram coletadas 3 árvores de cada tratamento, 62 meses pós-desbaste. Determinou-se densidade básica, poder calorífico superior (PCS) e composição química da madeira, os rendimentos gravimétricos além da densidade aparente, PCS e composição química imediata do carvão vegetal. A madeira apresentou características tecnológicas satisfatórias para produção de carvão vegetal, sob os diferentes níveis de desbaste, porém estes não influenciaram de maneira significativa as propriedades físicas e químicas doccarvão vegetal. Palavras-chave: Qualidade da madeira; carbonização; práticas silviculturais. Abstract Evaluation of different levels of thinning on properties of wood and charcoal from Eucalyptus grandis x Eucalyptus urophylla.This research aimed to evaluate effects of different levels of thinning in the physical and chemical properties of wood and charcoal from a hybrid clone of Eucalyptus urophylla W. Hill ex Maiden x Eucalyptus grandis S. T. Blake. The experiment was conducted in a plot of a forestry company which was divided into four tracks, representing the thinning levels of 0, 20, 35 and 50% applied to five years old plantations. Three trees were collected from each treatment, 62 months after thinning. Basic density, calorific power and chemical composition of wood had been determined, as well as charcoal properties as follows: gravimetric yields, density, chemical immediate composition and calorific power. Wood presented suitable technological characteristics for charcoal production, under different levels of thinning, but these did not influence significantly charcoal physical and chemical properties. Keywords: Wood quality; carbonization; forestry practices. INTRODUÇÃOA diminuição da oferta de combustíveis fósseis, restrições ambientais e aumento do consumo de energia propiciaram o aumento do uso da biomassa como fonte energética, visto que se trata de uma matéria-prima renovável, pouco poluente e de maior disponibilidade no Brasil.A madeira, e principalmente o carvão vegetal, constituem um dos principais insumos na geração de energia para a matriz energética brasileira.A qualidade do carvão vegetal é determinada pelas características da matéria-prima utilizada e da tecnologia de conversão. Segundo Campos (2008), no que se refere à matéria-prima, diversas pesquisas envolvendo as propriedades mecânicas, anatômicas, físicas e químicas da madeira vêm sendo realizadas
ResumoObjetivou-se realizar a caracterização energética de espécies de eucalipto para a produção de carvão vegetal. As espécies utilizadas foram Eucalyptus grandis x Eucalyptus urophylla, Eucalyptus propinqua, Eucalyptus robusta, Eucalyptus pellita e Eucalyptus botryoides. Avaliou-se o poder calorífico, densidades básica e energética, o rendimento gravimétrico e a análise química imediata do carvão vegetal. O experimento foi conduzido em delineamento inteiramente casualizado, com 3 repetições. A unidade experimental foi a tora, em que coletou-se discos com 5 cm de espessura, localizados à 0, 25, 50, 75 e 100% da altura total da árvore. As carbonizações foram realizadas em forno elétrico com temperatura final de 380 ºC. Realizou-se a ANOVA, teste Tukey e correlação segundo Pearson, todos a 5,0% de probabilidade. O poder calorífico da madeira e o rendimento não se diferiram significativamente entre as espécies em estudo. Os rendimentos médios encontrados foram de 39,65% em carvão e 21,06% em gases não condensáveis. O Eucalyptus robusta apresentou características energéticas semelhantes ao híbrido de Eucalyptus grandis x Eucalyptus urophylla, exceto pelas densidades, que naquele foram superiores. A densidade energética da madeira aumentou proporcionalmente à densidade básica, sendo que, a madeira mais densa apresentou maior quantidade de energia disponível. Conclui-se que, as características potenciais (PCS, Db e De) na produção de carvão vegetal foram evidenciadas em todas as espécies, no entanto, o Eucalyptus robusta foi a espécie mais promissora para fins energéticos para ser utilizada como biorredutor. Palavras-chave: Biomassa; carvão vegetal; Fonte renovável. AbstractEnergy characterization of different species of Eucalyptus. This study aimed to carry out energy characterization of Eucalyptus species for charcoal production. The species used were Eucalyptus grandis x Eucalyptus urophylla, Eucalyptus propinqua, Eucalyptus robusta, Eucalyptus pellita and Eucalyptus botryoides. The calorific value, basic and energetic densities, gravimetric yield and the immediate chemical analysis of charcoal were evaluated. The experiment was conducted in a completely randomized design with three replications. The experimental unit was the log, where 5 cm thick discs were collected at 0, 25, 50, 75 and 100% of the total height of the tree. The carbonization were carried out in an electric furnace with a final temperature of 380°C. Were evaluated the calorific power, basic and energy densities, yields of carbonization and chemical analysis. Were realized ANOVA, Tukey test and Pearson correlation, all at 5.0% probability. Calorific power of the wood and the carbonization yields did not differ significantly between the species under study. The average yields were 39.65% in coal and 21.06% in non-condensable gases. Eucalyptus robusta showed characteristics similar to the hybrid of Eucalyptus grandis x Eucalyptus urophylla, except for densities that were higher in first. The energy density of wood increases with increasing density, ...
Wood density is an important criterion for material classification, as it is directly related to quality of wood for structural use. Several studies have shown promising results for the estimation of wood density by near infrared spectroscopy. However, the optimal conditions for spectral acquisition need to be investigated in order to develop predictive models and to understand how anisotropy and surface roughness affect the statistics of predictive partial least square regression models. The aim of this study was to evaluate how the spectral acquisition technique, wood surface, and the surface quality influence the ability of partial least square-based models to estimate wood density. Near infrared spectra were recorded using an integrating sphere and fiber-optic probe on the tangential, radial, and transverse surfaces machined by circular and band saws in 278 wood specimens of six-yearold Eucalyptus hybrids. The basic density values determined by the conventional method were then correlated with near infrared spectra acquired using an integrating sphere and fiber-optic probe on the wood surfaces by means of partial least square regressions. The most promising models for predicting wood density were generated from near infrared spectra obtained from the transverse surface machined by the bandsaw, via an integrating sphere (r 2 p ¼ 0:87, RMSEP ¼ 23 kg m À3 and RPD ¼ 3.0) as well as for the optic fiber (r 2 p ¼ 0:78, RMSEP ¼ 35 kg m À3 and RPD ¼ 2.1). Surface quality affected the spectral information and robustness of predictive models with a rougher surface, caused by band sawing, showing better results.
Resumo -O objetivo deste estudo foi avaliar a qualidade da madeira de Cenostigma macrophyllum Tul para uso energético e determinar os rendimentos e propriedades do carvão vegetal produzido em diferentes temperaturas de carbonização. Foram retirados discos de 3 cm de espessura nas posições basal, 25%, 50%, 75% e 100% da altura comercial do fuste. Os discos foram cortados em cunhas e metade destas foi utilizada para análises na madeira e a outra metade foi carbonizada em temperaturas finais de 400 ºC, 500 ºC e 600 ºC para avaliação dos rendimentos e características do biorredutor. A densidade básica (1,2 g cm -3), teor de lignina (34%), poder calorífico superior (4.845 cal g -1 ) e rendimento gravimétrico de carbonização (RGC) aos 400 ºC (41,5%) da madeira do caneleiro se destacaram. O aumento da temperatura de pirólise da madeira de 400 ºC para 600 ºC resultou em acréscimo de 29,4% do teor de carbono fixo e redução de 19% e 63,4%, respectivamente, do RGC e do teor de materiais voláteis do carvão vegetal. Conclui-se que a espécie apresentou valores satisfatórios para produção energética. Wood and charcoal energy properties of Cenostigma macrophyllum: subsidies to sustainable useAbstract -This study aimed to evaluate the quality Cenostigma macrophyllum Tul wood for energetic use and to determine the yields and charcoal properties produced at different carbonization temperatures. Discs with 3 cm of thickness were obtained from stem basal positions, 25%, 50%, 75% and 100% of commercial height. The discs were split in two parts. One was used to determine wood properties and the other was carbonized at final temperatures of 400 ºC, 500 ºC and 600 ºC for bio-reducer evaluation . Basic density (1.2 g cm -3), lignin content (34%), higher calorific value (4,845 cal g -1 ) and gravimetric yield in charcoal (GYC) at 400 ºC (41.5%) were the highlights. The increase of wood pyrolysis temperature from 400 ºC to 600 ºC resulted in 29.4% increase in fixed carbon content and a reduction of 19% and 63.4%, respectively, in charcoal GYC and volatile matter content. In general, the species presented satisfactory energy production.
The objective of this study was to establish the correlation between the size of the wood knots and the modulus of elasticity (MOE) and the compressive strength (Fc) in Eucalyptus wood. 156 Eucalyptus urophylla samples with knots were separated into 3 classes (small, medium and large knots), and samples were selected from the same tree and submitted to the parallel fiber compression test for MOE and Fc determination. There was a significant difference between the MOE and Fc of the smaller knot class (Class 1) and the other classes with larger knots (Classes 2 and 3). In general, the larger the knot, the greater the difference between the MOE and Fc. Wood with small knots (8.31 mm 2 ) presents stiffness and strength statistically equal to wood free of defects. Eucalyptus wood stiffness is more sensitive to the presence of knots than the strength when compared to clear wood samples.
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