Wood drying

The Simpson model proposes that the rate of wood drying is directly proportional to average moisture content. In this work was done the fitting and the reproduction of drying curve for Heveabrasiliensis wood through of Simpson model and the chi-square statistical method. The curves were obtained by drying 108 specimens Heveabrasiliensis wood with size 10 mm x 20 mm x 100 mm that were drying in a laboratory kiln. The drying control was performed through gradual temperature increase in order to minimize the errors arising due the drastic loss of moisture by wood. The gravimetric method was used to evaluate the drying process, the specimens have theirs mass measured every 6 hours until the timber reached the theoretical anhydrous state. The drying curve of rubber wood obtained here can be used to estimate the drying time of this species for different kiln temperature settings.

Se realiza el diseño y simulación de un horno de
secado de madera que utilice el sol en reemplazo de los quemadores
tradicionales. Tomando los datos de un proceso de secado de madera
Roble realizado en un horno comercial del SENA, se realiza la
simulación de dicho proceso usando el simulador de dinámica de
fluidos computacional Autodesk CFD 2016, se realiza una
validación de la simulación, comparando la medición del sensor real
de temperatura y humedad relativa con los resultados de la
simulación en esta misma ubicación. Con el simulador validado, se
diseñan y simulan diversas geometrías del horno, cada una teniendo
en cuenta los errores de la anterior. En este documento se mostrará
el último diseño y simulación del horno. Para el diseño de detalle se
utilizó la metodología de diseño de Ulrich. El horno de secado se
diseña con el fin de disminuir costos energéticos y económicos a la
empresa Tecninsumos Ltda durante el proceso de secado de madera
roble en Taraza, Antioquia.

Acacia melanoxylon and Acacia dealbata are two Australian species well acclimated in Chile, both wood species with an interesting industrial potential. In this work, has been studied kiln drying runs and the wood drying quality of the sawn wood of Acacia melanoxylon and Acacia dealbata during kiln drying at conventional temperatures. Eight tests of kiln drying to conventional temperatures are made, using a convective drying of 0,3 m 3 of capacity. The experimental design includes as variable the species (A. melanoxylon an A. dealbata), the wood thickness (25 and 50 mm) and the cut-type (fl atsawn-wood and quartersawn-wood). The wood drying quality on the basis of European and Chilean standards is evaluated.

In Brazil, research on wood drying has been more focused on applied aspects than on fundamentals ones, and results have been published almost exclusively in Brazilian journals. The study of lumber deformation under aggressive drying conditions resulted in methods to group species and to define kiln schedules. Relationship between moisture content and electrical resistivity was used to improve quality control

Conventional kiln and vacuum drying are commonly used in industry to dry wood. In this research, an attempt was made to develop a better understanding of the effects of both drying methods on the mechanical properties of wood at the ultra-structure and cellular structure levels. Dynamic mechanical analysis (DMA) and nanoindentation (NI) were used together with standard static bending tests according to ASTM D143 to assess the respective effects of both drying methods on the performance of yellow birch ( Betula alleghaniensis Brit.) wood, an important species in the Canadian wood industry. Measurements of equilibrium moisture content (EMC) at different relative humidity (RH) levels showed that vacuum drying consistently yielded higher EMC values.  Vacuum-dried wood also exhibited superior MOE and MOR performance. Tests conducted by DMA demonstrated that the chemical structure of wood had undergone more changes during conventional kiln drying than during vacuum drying. The elastic mod...

Conventional kilns dominate the wood drying industry. However, energy consumption during the process of ventilation remains a significant challenge. In this study, we designed a device to recover waste heat from exhausted wet air during kiln drying. To determine energy conservation, the device was installed in a 50 m 3 kiln used for drying sawn timber in two different Chinese cities, and a traditional kiln with identical size was chosen to enable comparison. Two kinds of hardwood (Betula costata and Quercus mongolica) swan timbers were dried using conventional technology to investigate the energy saving effect of rainy seasons as well as seasonally different temperature. The results revealed that drying time and energy consumption decreased with the use of this energy-conserving device. Electrical and energy consumption were reduced by 18,9% and 38,5%, respectively. Waste heat recovery efficiencies ranged from 20,32% to 28,15%. Energy-conservation efficiency can be predicted to range from 12,23% to 22,74% annually. Equipment costs can be recovered within 3,5 years.

Due to its hygroscopic properties, the wood material reach a certain equilibrium moisture content at various usage areas according to the existing relative humidity and adapting the weather conditions considering the temperature. For this reason, there could be shrinkages and swellings in wood material dimensions if it is not dried enough with respect to its intended purpose and place of use. Therewith, a number of deformations occur in wood material such as cracking, warping and split-up at joints. Because of the high amount of water found in eucalyptus, which is the subject of the study, it is known that it is one of the most late-drying trees and difficulties occur during its drying process. In this study, the effects of natural drying methods performed at different environments upon eucalyptus (Eucalyptus camaldulensis) timber’ density and dimensional stability were investigated. Within this scope, sample timbers were stacked under two different atmospheres being open closed env...

Wood contains amount of water in the fibers due to its hygroscopic chemical structure. However, this moisture
content should be decreased with drying until according to suitable for each application. In the present drying methods, wood waste of fossil-based fuels are preferred to achieve the required temperatures. As a result of recent
developments, energy efficiency, sustainability and environment impacts have begun to be taken into account as costs. In this study, to reduce the negative impacts on the environment for solid wood drying with conventional methods, various methods of alternative clean energy sources that used in Turkey were examined. It can be said that examinations showed energy efficiency and a reduction in drying costs implementation of environmentally less harmful drying can be achieved with using these alternative energy sources.

Canelo wood is a highly valued native species in Chile that shows delicate marbling patterns with a pinkish soft silver luster. Due to its decorative qualities, canelo wood is dried for the manufacture of furniture and musical instruments. However, canelo wood lacks vessels cells that typically transport the water in hardwoods. Per its drying behavior, canelo wood is considered a transition species between hardwoods and softwoods. Therefore, this article reports drying schedules that were developed for drying 25-mm and 50-mm canelo lumber. In addition, this article reports experimental overall mass transfer coefficients, so that drying times for each of the drying stages can be easily estimated.

Low permeability of many wood species due to their anatomical properties causes problems during timber drying as well as impregnating with preservatives and resins. Microwave treatment influences heartwood permeability and improves preservative uptake and distribution. In the present study, microwave treatment of chir pine (Pinus roxburghii) wood was done at 2.45 GHz frequency at different level of intensity and radiation time. The gas permeability of chir pine wood was measured in an in-house built apparatus. Preservative uptake was tested using acid copper chromate preservative by a dipping process. The effect of radiation intensity and time on preservative uptake and air permeability were studied. The results revealed remarkable increase in longitudinal wood air permeability and preservative uptake with the increase of intensity and time of treatment. The results indicate that this technology can be tested and applied on pilot scale for application in wood preservation industry.

Background: The choice of a particular method of drying influences the drying time, quality of drying material and also on obtaining the desired moisture content for a particular purpose. It is possible to reduce the drying time and the incidence of defects when the process is conducted in an appropriate manner. Solar kiln drying is a method that has been was developed between the late 1950 and early 1960. This method is an
intermediary between the air-drying and in conventional kiln drying. The main features of this method are the low operating costs and a partial control of the drying conditions. Solar kiln drying is an alternative to methods that have high costs of investment, maintenance and energy consumption. The fact of the studied species present desirable
characteristics for the use of wood in the form of sawn, in addition to the absence of studies relating to drying, configures itself as relevant to search for such information. Objective: This study aimed to evaluate the drying of wood from bracatinga (Mimosa scabrella Benth), eucalypts (Eucalyptus dunnii) and teak (Tectona grandis L. f) in the solar kiln. Methodology: To do so, boards of the respective species with 25 mm
thickness were used, and monitored the loss of moisture in control samples, assessing the mass loss of the woods weekly. Results: The woods hard a apparent specific gravity at 12% of moisture content of 0.55; 0.79 and 0.58 (g.cm-3), respectively for Mimosa scabrella, Eucalyptus dunnii and Tectona grandis. These species reached a final moisture content of 10.36; 10.85 and 11.49%, being that the drying time was 119; 98 and 92 days with drying rate of 0.37; 0.19 and 0.73 (% .day-¹), respectively, for the studied species. In relation to environmental variables, the temperature of the interior d solar kiln has always been high than the average temperature of the external environment, even during nocturnal periods. Conclusions: Regarding the drying tensions, the wood of Tectona grandis did not develop drying tensions however the timber Mimosa scabrella and Eucalyptus dunnii developed drying stresses classified as mild and strong

Özet-TÜBİTAK 1001 projesi (Proje no: 112-O-818) olarak yapılan çalışmada, teknik olarak kurutulması güç ve uzun süreli olan Sapsız Meşe (6cm) ve Doğu Kayını (8cm) kerestesi yanında, 10 cm kalınlığında Sarıçam kerestesini kurutmada akustik emisyon (AE) yöntemini kullanarak, ağaç malzemeyi tahrip etmeden ulaşabilecek minimum kurutma sürelerini veren kurutma programlarının belirlenmesi hedeflenmiştir. AE yönteminde hedef, AE cihazı yardımıyla kurutma sürecinde ağaç malzemede oluşması muhtemel çatlak ve deformasyon gibi kusur oluşumlarını haber veren ses dalgalarını tespit etmek ve bu noktada kurutma şartlarına anında müdahale ederek kusur oluşumunu ortadan kaldırmaktır. Bu amaçla, önceden belirlenmiş kurutma programlarını uygularken AE cihazıyla eş zamanlı olarak ölçümler alınmış, bu süreçte sürekli ses dalgalarının takibi yapılarak kusurların oluşumunu haber veren frekanslarla ilgili eşik değerler belirlenmiş, daha sonra yapılan kurutma denemelerinde de bu eşik değerleri aşan durumlarda kurutma şartlarından ortam sıcaklığı ve bağıl nemine müdahale edilerek o ağaç türünün o kalınlığı için uygulanabilecek optimum kurutma programına ulaşılması sağlanmıştır. Bu sayede, hem haftalar veya aylar süren kurutma sürelerinin aşağı çekilmesi ve hem de ciddi maliyet oluşturan kurutma giderlerinden önemli tasarruflar sağlanması öngörülmüştür.

The objective of this study was to test a new in-kiln sensor for monitoring lumber moisture content during industrial drying. The theoretical foundation of the technology was already known, because it is based on electrical conductivity, but the mechanism of implementation was new and required validation. For this reason, the technology was compared with two other widely used methods for assessing lumber moisture content, namely, the oven-drying and electrical capacitance methods. The tests were performed in a 120-m3 industrial kiln operated by a sawmill in the eighth region of Chile, and the results showed that the average moisture content at the end of drying was satisfactorily determined by the new in-line sensor. As predicted by theory, the sensor was not able to accurately measure moisture content above 25%, but it was still able to provide the equivalent of a drying curve for monitoring of the drying process.

Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards. Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer.The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and ...

The relationship between drying and hygroscopic ability of Crateva adansonii and Populus deltoides woods to resist feeding by Odontotermes obesus was studied. Woods were dried under the sun and in the oven for a range of 5-25 days and then these were exposed to termites for 25 days in underground pits in Randomized Complete Block Design pattern with five replications. Results showed that lowest moisture gain was observed at a short time for drying with each method. Weight loss after termites’ exposure was more in less dried sap and heartwood of either plant species. The practical implication of these results is discussed.

The objective of this work was to evaluate the yield of sawn wood and the operational efficiency in the sawing of Hovenia dulcis logs in a portable sawmill, as well as to evaluate the behavior of the wood in conventional kiln drying. For this purpose, five trees were selected, from which 14 logs of 1.8 meters in length were obtained to determine the volume, the yield of two diametric classes (20 to 24 and 24.1 to 28 cm) and the operational efficiency during the sawing of the logs. For the drying process, the parameters of initial temperature, final temperature and drying potential were obtained from the drastic drying method at 100ºC. The yield results showed that there were no statistical differences between the two diametric grades. For operational efficiency, the highest diameter class (1.00m³/worker/day) was higher than the lower diameter class (0.70m²/worker/day). For the drying of Hovenia dulcis wood, it is possible to consider this species as a difficult drying type according to the parameters found for the elaboration of the drying programs. In addition, the moisture loss of the wood occurred slowly due to its low permeability. keywords: Portable Sawmill, operational efficiency, drying program. Resumo Rendimento de uma serraria portátil e secagem da madeira de Hovenia dulcis em estufa convencional. Este trabalho teve por objetivo avaliar o rendimento em madeira serrada e a eficiência operacional no desdobro da madeira em uma serraria portátil, assim como o comportamento da madeira de Hovenia dulcis na secagem convencional. Para tanto, foram selecionadas 5 árvores, sendo posteriormente escolhidas 14 toras que foram traçadas com 1,8 metros de comprimento, para determinação do volume, rendimento de duas classes diamétricas (20 a 24 e 24,1 a 28 cm) e a eficiência operacional durante o desdobro das toras. Em relação a secagem, foram obtidos os parâmetros de temperatura inicial, final e potencial de secagem, pelo método de secagem drástica a 100ºC de pequenas amostras. Os resultados do rendimento demonstraram que não houve diferenças estatísticas entre as duas classes diamétricas. Para a eficiência operacional, a maior classe diamétrica (1,00m³/operário/dia) apresentou-se superior a menor classe diamétrica (0,70m²/operário/dia). E para a secagem da madeira de Hovenia dulcis, pode-se considerar uma espécie de difícil secagem em função dos parâmetros encontrados para elaboração dos programas de secagem, além disso, a perda de umidade da madeira ocorreu de forma lenta, em função de sua baixa permeabilidade. Palavras-chave: Serraria móvel, eficiência operacional, programa de secagem.

Attempts were made to develop solvent-resistant polyimide capillary membranes with integrally skinned asymmetric structure to be used for the treatment of wood dryer emissions or vacuum pyrolysis aqueous effluents. Model mixtures of 1-propanol (1-PrOH)/H2O and acetic acid (AA)/ H2O, with concentrations of 10–90 wt % of organic components, were used as vaporous feeds. Solvent-resistant membranes with good mechanical and excellent vapor separation properties were prepared from polyimides based on PMDA and BPDA by the dry/wet phase-inversion technique. Molecular structure largely influences membrane properties. For the asymmetric polyimide membranes studied, a tendency similar to that of homogeneous dense membrane was found. Membranes prepared from polyimides with diamine and dianhydride moieties, both containing rigid backbone and aromatic rings, displayed higher permeability and selectivity. Test conditions exhibited influences on membrane separation performance. Membranes prepared from copolyimide BPDA–50DDS/50ODA and PMDA–50DDS/50ODA exhibited the best mechanical and chemical properties as well as water vapor separation properties, which are considered to be of practical usefulness for applications of these membranes in the removal of water from water/organic mixtures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 139–152, 2002

Abstract This study reports experimental data of airflow distribution as a function of fan speed in an industrial batch kiln. Measurements were conducted with 20 hot-film anemometers distributed throughout the load at two occasions. The main result was that airflow distribution did not change significantly as the fan speed was reduced, and no positions where the air movement stopped were found. It was also found that relatively more air ran in the bolster spaces in comparison to the adjacent packages as the air ran through the load.

ABSTRACT The objective of this study was to determine the isothermal drying kinetics of Acacia mangium wood blocks by employing a relative humidity-controlled drying chamber. A model was developed based on solution of Fick's second law and evaluated through the coefficient of determination (R2 ), sum of square error (SSE), root mean square error (RMSE), and reduced chi-square (χ 2 ). This model was compared to semi-theoretical models which are commonly used to describe the drying behavior of biomass in previous studies. The porosity and shrinkage characteristics of dried specimens were also evaluated. Based on the findings in this work, it was determined that the proposed model resulted in an excellent fit with experimental data for all four drying temperature levels of 30, 35, 40, and 45∘ C to describe the isothermal drying kinetics of Acacia mangium . It appears that volumetric shrinkage of the samples decreased quadratically with decreasing moisture ratio. The activation energy of the drying process was determined to be 41.07 kJ/mol.

A method to estimate the surface moisture content below the fibre saturation point that is a function of the surface temperature, wet-and dry bulb temperatures, equilibrium moisture content, and fibre saturation point was evaluated. The method is based on the premise that the surface temperature is solely influenced by the surface moisture content and the climate that the surface is exposed to. The prediction model contends that the surface moisture content is equal to the fibre saturation point when the surface temperature is equal to the wet bulb temperature, and equal to the equilibrium moisture content when the surface temperature is equal to the dry bulb temperature, with a linear interpolation between those two points. The model thus predicts that the average moisture content of a thin piece of veneer can be predicted with fairly good accuracy. Also, when drying boards in a fast changing climate, e.g. fan reversals in industrial kilns, the surface temperature and surface moisture content should change as abruptly as the climate does. Additionally, the surface moisture content should correlate to the known drying phases, with a consistently high surface moisture content during the capillary phase when the wet line is close to the surface, and a quickly decreasing surface moisture content when the wet line moves into the wood during the transition to the diffusion phase. The prediction model was tested in these three scenarios and the results suggest that the basic premise is reasonable, and that the method is useful for surface moisture content estimation.

The determination of moisture content gradients is one of the most important steps for assessing the quality of wood drying. The general aim of this work was to study the quality of air-dried teakwood boards according to the gradients of moisture content in thickness and length. Six representative boards (40 × 180 × 2,300 mm) were sampled from a stack air-dried under shelter, divided into 30 equal parts in length and measured with a resistance moisture meter, resulting in four treatments: two depths (1/4 and 1/2 thickness) and two surfaces (inner and outer) of measurement. As main results, we can conclude that the air-drying quality can be considered good, mainly for two reasons: i) the average moisture content gradients in thickness were comparable to those reported in literature for kiln-drying of less thick boards; ii) the range of average moisture content among boards (2.5 p.p.) was satisfactory for a drying process carried out without environment control. Length moisture conten...

Abstract. The improvement and optimization of air-distribution systems in drying kilns contributes to the pres-ervation of the quality, safety and shelf life of perishable products. The present study reports on the numerical solution of airflow within a two dimensional drying kiln enclosure loaded with wooden pallets. The performance of air flow field is examined with and without supply of wooden pallets. Different arrangements of the supplied wooden pallets are investigated as well as the use of a screen in order to improve the airflow filed. The steady state RANS equations that formulate the flow problem are solved along with a turbulence model that is the stan-dard k-εor the rng k-ε. The effect of the turbulence modeling is distinguished through direct comparisons of the derived airflow patterns. The results obtained show the presence of stagnant zones inside the pallets columns and above of them and the presence of recirculation regions in different zones of the drying kiln with...

Conventional kiln and vacuum drying are commonly used in industry to dry wood. In this research, an attempt was made to develop a better understanding of the effects of both drying methods on the mechanical properties of wood at the ultra-structure and cellular structure levels. Dynamic mechanical analysis (DMA) and nanoindentation (NI) were used together with standard static bending tests according to ASTM D143 to assess the respective effects of both drying methods on the performance of yellow birch ( Betula alleghaniensis Brit.) wood, an important species in the Canadian wood industry. Measurements of equilibrium moisture content (EMC) at different relative humidity (RH) levels showed that vacuum drying consistently yielded higher EMC values.  Vacuum-dried wood also exhibited superior MOE and MOR performance. Tests conducted by DMA demonstrated that the chemical structure of wood had undergone more changes during conventional kiln drying than during vacuum drying. The elastic mod...

Juvenile Neolamarckia cadamba or kelempayan tree has been harvested from forest plantation and converted into sawn timber. Some basic properties of timber such as physical and mechanical were determined from different parts of the tree namely lower, center and upper. The physical properties were evaluated based on MS 837:2006, BS EN 13183-1:2002 and ISO 3131:1975 (E). The mechanical properties were conducted using small test clear specimens following BS 373:1957. The results indicated that the physical and mechanical properties of the lower portion of the trunk were significantly superior compared to the upper portion of the trunk. The investigation revealed that the wood be able to use as a substitute material of the furniture components after some modification undertaken on its properties.