Estimativa do tempo de vaporização de toras de Eucalyptus grandis

Calonego, Fred Willians; Severo, Elias Taylor Durgante

doi:10.1590/s0100-67622006000300016

Cited by 8 publications

(5 citation statements)

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“…The variation in temperature by treatment of steaming or heating generally follows the model proposed by Steinhagen et al (Steinhagen et al 1987). This model proposes that the optimum steaming time relates to the log diameter, the thermal diffusivity constant and the Fourier number, which indicates the temperature that the log should reach (Calonego and Severo 2006). Temperature variation in the logs of different diameters of Hieronyma alchorneoides in both the heatingtreatment and the steaming treatment shows the behaviour of Steinhagen et al's model (Fig.…”

Section: Discussionmentioning

confidence: 96%

Reduction of growth stresses in logs of Hieronyma alchorneoides Allemão from fast-growth plantations using steaming and heating: effects on the quality of lumber

Moya

2021

Annals of Forest Science

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& Key message Growth stresses are usually present in the fast-growing trees of forest plantations and can be evaluated along stem diameter. Growth stresses are relaxed after tree felling and during sawing and drying, and are manifested in the lumber quality. Different methods have been employed to reduce the effect of growth stresses, such as steaming and heating treatments. Excellent growth and yield in forest plantations of Hyeronima alchorneoides were observed, but they showed difficulties in the primary sawing process and a high incidence of wood warping during the drying process. Steam and heat treatments on the log were used to study their effects on H. alchorneoides sawlog and to evaluate lumber quality. & Context Growth stresses in Hieronyma alchorneoides Allemão trees growing under fast-growth conditions show high and negative effects on the lumber quality (increased warps and splits or checks). Therefore, steaming and heating treatments have been applied to reduce these effects on the lumber. & Aims The main objective of the present work was to evaluate the effects of steaming and heating treatments on sawlogs of Hieronyma alchorneoides from the fast-growth plantations to reduce the longitudinal surface growth stress. & Methods Twenty-six trees ready for felling in the third thinning were sampled and commercial logs measuring 2.5 m long were extracted from them at different heights. These logs were used to investigate the effect of steaming and heating treatments and the growth stresses were measured before and after treatment. Crooking due to sawing, colour and wards, splits and checks were measured. & Results The results showed that the internal temperature of the logs was approximately 85 °C after the heating treatment, and it was nearly 90 °C after the steaming treatment. It resulted in a reduction of 1500 με (micro-deformations) before the treatment to 1000 με after the treatment. Therefore, crooking due to sawing decreased significantly in logs or semi-logs. The parameters such as colour, luminosity (L*), redness (a*) and lightness (b*) decreased in heartwood while L* increased and a* and b* decreased in sapwood, which led to the decrease in quality of the lumber, the magnitude and incidence of the defects in treated logs. & Conclusion As compared to untreated logs, the best performance was obtained with steaming treatment, followed by the heating treatment. The difference found between steaming and heating can be attributed to the temperature in the internal part of the log, which was more than 90 °C in steaming treatment; meanwhile, in the heating treatment, the internal temperature of the log was slightly lower (80-85 °C). Therefore, glass transition can be more easily reached by steaming treatment than by the heating treatment.

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Section: Discussionmentioning

confidence: 96%

Reduction of growth stresses in logs of Hieronyma alchorneoides Allemão from fast-growth plantations using steaming and heating: effects on the quality of lumber

Moya

2021

Annals of Forest Science

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“…However, it's noted that the proposed model underestimates the real time that Eucalyptus grandis logs need to reach the desired temperature (Calonego and Severo 2006).…”

Section: Introductionmentioning

confidence: 95%

“…In the evaluation of the steaming effects on drying defects of Eucalyptus grandis by submitting logs at a temperature of 90 • C during 20 hours, it's concluded that the cracks index reduction was 18.4%, 27.7% and 43.4%, respectively, for logs with 30 to <35, 25 to <30 and 20 to <25 cm of diameter (Calonego and Severo 2006). According to the authors, logs with smaller diameters present bigger reduction of defects when compared with the ones with bigger dimensions.…”

Section: Introductionmentioning

confidence: 99%

Use of glass transition temperature for stabilization of board's cracks of Eucalyptus grandis

Calonego

Severo

Cunha

et al. 2010

An. Acad. Bras. Ciênc.

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The Eucalyptus grandis logs temperatures were determined and correlated with the board's cracks during steaming. Thermocouples were inserted in the logs center, registering their temperatures during steaming at 90 • C. The logs were sawed and the board's cracks measured. It was concluded that: (1) the logistic S-shaped curve explains the logs temperature variation; (2) the logs with diameter of 20 to <25, 25 to <30 and 30 to <35 cm presented, respectively, 84.2 • C, 73.1 • C and 45.8 • C in the steaming; and (3) the cracks lengths significantly decreased in logs that reached the glass transition temperature.

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“…Assim, considerando os aspectos econômicos e de qualidade da madeira do gênero Eucalyptus, autores como Andrade (2000), Calonego (2004), Ciniglio (1998), Jankowsky (2008), Martins et al (1999), Northway (1996), Pratt (1974), Rozas (1993) e Santos (2002, recomendam o uso de um potencial de secagem ameno e de temperaturas iniciais que não excedam a 45ºC, principalmente nos estágios iniciais. Outra alternativa para atender a esses aspectos caracteriza-se pelo uso da pré-secagem ou a combinação da secagem ao ar livre com posterior secagem convencional, proporcionando redução de custos e otimização do processo, por meio da maior efi ciência das câmaras convencionais de secagem; além de atenuar o gradiente de umidade na madeira, responsável pela maioria dos defeitos durante a secagem (CAMPBELL;HARTLEY, 1988;CINIGLIO, 1998;DENIG et al, 2000;FRANZONI, 2001;JANKOWSKY, 2008;NORTHWAY, 1996;SANTOS, 2002;STÖHR, 1977).…”

Section: Souza J T De Et Alunclassified

Qualidade da madeira serrada proveniente de árvores dominantes e médias de Eucalyptus grandis submetidas à secagem

Souza¹,

Trevisan

Denardi

et al. 2012

CERNE

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RESUMO:Neste estudo, objetivou-se verifi car, em árvores de diâmetro dominante e médio, a infl uência da secagem ao ar livre e secagem convencional na qualidade da madeira serrada de um povoamento de Eucalyptus grandis W. Hill ex Maiden, aos 14 anos de idade, situado no município de Capivari do Sul, Rio Grande do Sul. Para tanto, a amostragem das árvores foi realizada após um inventário piloto, tendo como base o diâmetro à altura do peito (DAP) dominante e médio. Após a derrubada, foi retirada a tora localizada entre as posições DAP e 25% da altura comercial. As toras foram desdobradas em tábuas para serem submetidas à secagem ao ar livre até 18% do teor de umidade, e à secagem convencional foi conduzida até 13% de umidade. Rachaduras de topo e arqueamento das tábuas foram avaliadas após o desdobro, na secagem ao ar livre e na secagem convencional. Os resultados mostraram que, tanto para as árvores dominantes quanto para as médias, o índice de rachaduras de topo e a fl echa de arqueamento das tábuas não diferem signifi cativamente nas diferentes fases de processamento da madeira. No entanto, a comparação entre esses dois estratos evidencia que a magnitude desse defeito é mais pronunciada nas árvores médias.Palavras-chave: Rachaduras de topo, arqueamento, secagem ao ar livre, secagem convencional, madeira refratária. WOOD QUALITY OF Eucalyptus grandis DOMINANT AND AVERAGE TREES SUBMITTED TO DRYING

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Estimativa do tempo de vaporização de toras de Eucalyptus grandis

Cited by 8 publications

References 1 publication

Reduction of growth stresses in logs of Hieronyma alchorneoides Allemão from fast-growth plantations using steaming and heating: effects on the quality of lumber

Reduction of growth stresses in logs of Hieronyma alchorneoides Allemão from fast-growth plantations using steaming and heating: effects on the quality of lumber

Use of glass transition temperature for stabilization of board's cracks of Eucalyptus grandis

Qualidade da madeira serrada proveniente de árvores dominantes e médias de Eucalyptus grandis submetidas à secagem

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