Pine wood modification by heat treatment in air

Maritime pine (Pinus pinaster) wood has low dimensional stability and durability. Heat treatment was made in an oven using hot air during 2 to 24 h and at 170-200 ºC. A comparison was made against steam heat treatment. The equilibrium moisture content and the dimensional stability (ASE) in radial and tangential directions were evaluated at 35%, 65% and 85% relative humidity. MOE, bending strength and wettability were also determined. At the same mass loss improvements of equilibrium moisture content and dimensional stability were higher for oven heat treatment but the same happened for mechanical strength degradation. A 50% decrease in hemicellulose content led to a similar decrease in bending strength

Heat induced colour changes of pine (Pinus pinaster) and eucalypt (Eucalyptus globulus) wood

Heat treatment of Pinus pinaster and Eucalyptus globulus wood was made by hot air in an oven during 2 to 24 h at 170-200 ºC and by steam in an autoclave during 2 to 12 h at 190- 210 ºC. The colour parameters L*, a* and b* were determined by the CIELAB method on radial, tangential and transverse sections for untreated and treated wood, and their variation with the treatment (ΔL*, Δa* and Δb*) were calculated in percent. In the untreated woods, for eucalypt wood lightness (L*) varied between 54.1- 63.8% with a* between 7.4-8.5 and b* 15.7-19.9, and for pine wood L* varied between 67.3-76.1%, a* between 6.9 -7.6 and b* 16.3 -24.1. With the heat treatment wood became darker, more for oven treatment (ΔL* about 50% for 4% mass loss), and at the same treatment conditions more for eucalypt wood. In general the contribution of the red colour (a*) and yellow (b*) decreased with the heat treatment. The transverse section darkened less in the two species and for both treatments, with small differences between radial and tangential sections. Lightness decrease was related to chemical changes, with good correlations with glucose (R2= 0.96), hemicelluloses (R2 = 0.92) and lignin (R2 = 0.86). As regards colour, the heat treatments showed an interesting potential to improve the wood quality for solid timber products from pine and eucalypt

Wood modification by heat treatment: a review

Wood heat treatment has increased significantly in the last few years and is still growing as an industrial process to improve some wood properties. The first studies on heat treatment investigated mainly equilibrium mois-ture, dimensional stability, durability and mechanical properties. Mass loss, wettability, wood color, and chemical transformations have been subsequently extensively studied, while recent works focus on quality control, modeling, and study the reasons for the improvements. This review explains the recent interest on the heat treatment of wood and synthesizes the major publications on this subject on wood properties, chemical changes, wood uses, and quality control

Improvement of technological quality of eucalypt wood by heat treatment in air at 170-200ºC

Eucalypt wood is a low value wood considered a non durable species with low dimensional stability, used almost exclusively for pulp and paper or as firewood. The heat treatment was made in an oven in the presence of oxygen during 2 to 24 h and temperatures of 170-200ºC. Mass loss with treatment, equilibrium moisture content, dimensional stability measured as ASE in radial and tangential directions and at 35%, 65% and 85% relative humidity, MOE, bending strength and wettability were determined. Mass loss increased with treatment time and temperature reaching 9.5% for wood treated at 190ºC for 24h. Equilibrium moisture content decreased more than 50% (at 35% relative humidity) reaching a maximum of 61% reduction. At higher air relative humidity the reduction was smaller, 49% and 38% at the most for 65% and 85% relative humidity. Dimensional stability (ASE) increased with maximum values of 88% and 96% in radial and tangential direction, respectively. The improvement was higher for lower relative humidity. There was a reduction on mechanical resistance with heat treatment especially for bending strength that decreased about 20% for 3% mass loss, reaching 60% for mass losses higher than 10%. MOE decreased with heat treatment the reduction was under 10% until 8% mass loss. The contact angle increased until 5% mass loss, decreasing slightly afterwards. Heat treatment was shown to be a useful method to improve the technological quality of eucalypt wood as regards dimensional stability allowing it to compete with higher cost woods for some applications

Colagem e propriedades mecânicas da madeira de pinheiro tratada termicamente

O tratamento térmico da madeira permite diminuir a higroscopicidade da madeira, melhorando a sua estabilidade dimensional e a resistência a vários tipos de biodegradação. Utilizando este tratamento é possível atribuir um maior valor acrescentado, permitindo a madeiras menos nobres a sua utilização no exterior, sem a utilização de qualquer químico. O tratamento térmico da madeira de pinheiro (Pinus pinaster) foi feito na ausência de oxigénio numa autoclave com uma mistura de ar sobreaquecido e saturado durante 2, 4, 6, 8 e 12 horas à temperatura de 200 ºC. Determinou-se a resistência à colagem, a molhabilidade e a dureza nas secções tangencial e radial, o módulo de elasticidade e a tensão de rotura por flexão estática. A resistência à colagem, utilizando uma cola de acetato de polivinil (PVA) foi determinada de acordo com a norma DS/CEN/TS 13354. Determinou-se a molhabilidade da madeira pelo método do ângulo de contacto usando um goniómetro. A dureza foi medida de acordo com a norma ISO 3350 (1975). O módulo de elasticidade e a tensão de rotura à flexão foram determinados através de um ensaio a três pontos. Verificou-se que a resistência à colagem diminuiu com a intensidade do tratamento térmico. Foi possível obter uma relação aproximadamente linear (R2=0,81) entre a resistência à colagem e a perda de massa devido ao tratamento térmico. Ao mesmo tempo observou-se uma diminuição da molhabilidade da superfície da madeira o que contribui para uma diminuição da resistência à colagem. Em relação às propriedades mecânicas o MOE praticamente não foi afectado enquanto a tensão de rotura diminuiu com a intensidade do tratamento atingindo cerca de menos 30%. A dureza da madeira tratada também diminuiu quer na secção tangencial, quer na radial atingindo uma redução máxima de cerca de 30%

Labour share heterogeneity and fiscal consolidation programs

We show that the labour share of income is an important factor affecting the mechanisms behind fiscal consolidation programs, thus requiring consideration when evaluating fiscal mul- tipliers across countries. We calibrate a life-cycle, overlapping generations model to match key characteristics of different European economies and evaluate the recessive impacts of fiscal consolidation programs. We find a positive relationship between the labour share and the impact fiscal multipliers generated by our model. This result directly follows from the higher weight of labour on production and the lower opportunity cost of leisure present in economies with a higher labour share. Following the impact period, the relationship between the labour share and the fiscal multipliers is dependant on the type of fiscal instrument employed in the consolidation

Quality assessment of heat-treated wood by NIR spectroscopy

NIR spectroscopy was tested for predicting the properties of heat treated wood using pine (Pinus pinaster) and eucalypt (Eucalyptus globulus) woods with two types of treatment: in oven and in a steam autoclave. Mass loss, equilibrium moisture content, dimensional stability, MOE, bending strength, colour CIELAB parameters and extractives content were determined. NIR spectra were obtained using a fibre probe on the radial surface of the samples. NIR models for mass loss showed very high coefficients of determination (R2) for cross validation ranging from 96– 98%. The models obtained for wood properties were in general good with coefficients of determination ranging from 78–95% for equilibrium moisture content, 53–78% for dimensional stability, 47–89% for MOE, 75–77% for bending strength and 84–99%, 52–96% and 66–98% for colour parameters L, a∗ and b∗, respectively. R2 of the models for extractive content varied between 41.9–79.8% for pine and between 35.3–82.2% for eucalypt wood. NIR spectroscopy showed a good potential for quality control and characterization of heat treated woods

Chemistry and ecotoxicity of heat-treated pine wood extractives

Pine (Pinus pinaster) wood was heat treated in an autoclave for 2-12 hours at 190-210 ºC. Hemicelluloses were the first compounds affected by the treatment. In general, the sugar decrease was higher for arabinose and galactose followed by xylose and mannose. Lignin started to degrade for small mass losses but at a slower rate than hemicelluloses, and cellulose only degraded significantly for severe treatments. Almost all of the original extractives disappeared and new compounds arose like anhydrosugars and phenolic compounds. The compounds that might leach from heat treated wood were mainly those identified in the water and ethanol extracts, all of which were not harmful at the existing concentrations, thereby reinforcing the wood heat treatment as an environmental benign process.info:eu-repo/semantics/publishedVersio

Pyrolysis and Extraction of Bark in a Biorefineries Context: A Critical Review

Abstract: Bark-based biorefineries are estimated to become a trending topic in the coming years, particularly with their adsorbent applications and antioxidant production. While the potential benefits of bark-based biorefineries are well-recognized, it is not known how to develop a bark-based biorefinery considering different unit operations and the potential end products. The characterization and screening of different barks for chemical composition is the initial step in biorefinery development, along with the selection of the relevant conversion processes. This state-of-the-art review provides background knowledge on the pyrolysis and extraction studies of bark as the key conversion operations. The results of recent (2010–2022) bark pyrolysis and extraction studies were critically analyzed for process conditions, product properties, and product yields, as well as a discussion of energy-saving possibilities. A biorefinery scheme was proposed based on these data. The current knowledge gaps were identified and future directions were evaluated, which include the production of charcoals, platform chemicals, and extract profiling for specific applications. The results indicate that barks are particularly rich in hydrophilic extractives with potential antioxidant properties and pyrolysis operations, resulting in functional chars that may be used in value-added applications as adsorbent materials. A biorefinery scheme allows for the production of platform chemicals, antioxidant extracts and biochars from barks while contributing to the reduction of waste and environmental pollution.info:eu-repo/semantics/publishedVersio