Assessment of air emissions from industrial kiln drying of Pinus radiata wood

D. Don) at 100 °C dry bulb and 70 °C wet bulb, were assessed by measuring the concentration of chemical components in the kiln atmosphere at regular time intervals and determining air-flows and temperature differentials across the stack. The volatile organic compounds (VOC) were trapped on activated carbon and analyzed by GC-MS. The aldehydes were trapped in 2,4-dinitrophenol-hydrazine solution and the aldehyde derivatives analysed by HPLC. Polar compounds were trapped in water and then alcohols were analysed by GC and organic acids by ion exchange chromatography. The two major VOC found were α-pinene and β-pinene, which made up 90% of the total discharge (405 g/m³ wood). Most of the VOC fraction was released during the early stages of drying. The release of potentially hazardous components (formaldehyde, acetaldehyde, furfural) was found to be relatively low (1.1, 8.7, and 0.1 g/m³ wood, respectively) provided the kiln emissions are well dispersed, these levels of release are unlikely to cause adverse environmental effects.     

Heat distribution in thermally modified timber

The heat distribution during thermal modification of beech (Fagus sylvatica L.) and spruce (Picea abies L. Karst) wood with dimensions of 80 × 80 × 200 mm³ has been investigated. Heat distribution was continuously measured by thermocouples in longitudinal and transverse directions. Significant temperature gradients occur in the initial phase of the process as well as during the modification phase (set temperature 200 °C for 3 h), where ongoing chemical reactions in wood were taking place. Thus, the temperature in the investigated positions increased to 240 °C (beech) and 215 °C (spruce). The mentioned properties should be taken into account when optimizing the heat treatment process (quality control, energy savings, etc.).     

Liquid water flow in Pinus radiata during drying

End-sealed 60×60×250?mm³ Pinus radiata pieces were dried at 65/37 °C (dry bulb/wet bulb temperature) and 4 ms^-1 air speed to study various drying phenomena above fibre saturation point. While drying, an X-ray computed tomography (CT) scanner captured a cross-cut density image every ten minutes. The density data was used to determine moisture content, rate of moisture loss from the core, wetline (boundary line of the free water region) depth and cross-cut area of the wood pieces. Repeating patterns were observed, which indicated that the cavity-size distribution of the wood pieces dictated fluctuations in the rate of moisture loss from the core and cross-cut area shrinkage during drying in the free water phase. It is hypothesised that, while drying an interconnected capillary network in the free water phase, the largest meniscus penetrates a wood piece through the largest cavities, thus also allowing air into the capillary network. The largest meniscus would always get smaller as it penetrates the wood piece until it is not the largest meniscus in the network anymore. Then the new largest meniscus would start penetrating the capillary network, etc. The largest meniscus would also determine the liquid tension in the capillary network. When the largest meniscus gets small enough, and the liquid tension strong enough, deformation and collapse of the remaining liquid-filled cavities can occur. A large liquid-filled interconnected capillary network would eventually fragment into a number of smaller liquid-filled interconnected networks, at which point a receding wetline could be observed.     

Low temperature fluidized wood chip drying with monoterpene analysis

This paper describes the drying of ponderosa pine wood chips at low (20°C and 50°C) temperatures using a bench-scale batch pulsed fluidizer to evaluate both volatile pine oils (monoterpenes) and moisture losses during drying. Ten monoterpenes were measured; anecdotal information on inter-tree differences in monoterpene composition indicate that while overall total monoterpene composition is similar for each tree, the ratios of ??-pinene, ??-pinene, ??-3-carene and limonene differ between individual trees. Results of the drying studies show normal drying curves at 20°C and 50°C; at the air flow rates used, a 20% final moisture content resulted after approximately 45 and 25 min for the two temperatures, respectively. Oil content data were highly variable but indicated that at 50°C, oils start to volatize by approximately 10 min of drying. At 20°C, oil content does not appear to change over drying time.     

Microwave treatment of <Emphasis Type="Italic">Eucalyptus macrorhyncha</Emphasis> timber for reducing drying defects and its impact on physical and mechanical wood properties

Microwave is a useful and proven tool for increasing permeability of refractory wood and, thereby, it can be used for reducing drying time and defects. However, strength loss is always a concern. In this study, green timber boards were treated with microwave in two intensities, low microwave (LMW), 89 kWh/m³, and high microwave (HMW), 95 kWh/m³, and compared with control boards. Samples of all three treatments were kiln dried together. Density and selected mechanical properties were also assessed after drying. LMW, the treatment which presented the best results, showed reduction in some drying defects, such as collapse (20%), surface check length (84%), internal check length (50%) and internal check width (70%). Density, MOE and MOR on static bending were unchanged, whereas reductions in shear strength (13%) and compression strength parallel to grain (10%) were observed. HMW, on the other hand, produced higher strength reductions and more drying defects than LMW. Fine adjustments of LMW microwave power might bring drying benefits without strength losses.     

VOC sorption and diffusion behavior of building materials

In this study 25 different building materials often used in timber constructions (wood based panels, gypsum boards, vapor barriers, adhesive tapes, insulation materials and sealants) were investigated with regard to their adsorption, desorption and diffusion behaviour towards volatile organic compounds (VOC). The materials were exposed to four, respectively five selected VOCs typically found in indoor air: hexanal, butyl acetate, p-xylene, nonane and α-pinene. Adsorption and desorption properties were investigated under static conditions, whereas the diffusion behavior was examined in a 0.225 m³ emission chamber with an air exchange rate of 1 h^?1. The results of the experiments indicate that some building products have a high potential to reduce VOCs in indoor air. Apart from the vapor barriers, two insulating materials and one plasterboard, all tested materials represented an adsorption efficiency of about 50 % or higher related to the injected VOC standards. Materials with high adsorption capacity bound substances strongly and desorbed them less, whereas less adsorbing materials acted inversely. The obtained results indicate that material properties and processing play a considerable role in diffusion behavior of building materials.     

Influence of temperature on the embedding strength

In order to determine the influence of the temperature on the embedding strength at the yield threshold, 150 tests were carried out using 8 mm dowels. The tests were performed on samples of Pinus sylvestris L. with density in the range between 489 kg/m³ and 679 kg/m³ with an initial moisture content of about 11%. The tests were carried out in the longitudinal and transversal directions to the wood grains, with the temperature varying from 20°C to 240°C. The tests and the specimen dimensions follow the standard NF-EN 383.     

Wood–water relations of chestnut wood used for structural purposes

Hygroscopic properties and water vapour permeability of chestnut (Castanea sativa Mill.) wood were studied using saturated salt solutions, and the results were analyzed using the Hailwood–Horrobin model. At 20 °C/65 % the equilibrium moisture content (MC _eq ) and density were 11.5 ± 0.1 % and 576.6 ± 10.2 kg m^?3, respectively, and the fiber saturation point was 20.83 %. The average water vapour permeability was 0.320 kg m^?1 s^?1 Pa^?110⁸, lower than that of Radiata pine (0.726 kg m^?1 s^?1 Pa^?110⁸). Furthermore, there was no difference in permeability between tangential and radial cuts. This low permeability is explained by the scant development of the multilayer of the Hailwood–Horrobin model. This is attributed to the wood extractives, which reduce the void space and hindered condensation. Chestnut wood has different vapour sorption and vapour permeability than conifers normally used in construction.     

Effects of delayed drying and CO2 application on copper amine fixation in ACQ treated red pine

Fixation of copper and amine in alkaline copper quaternary (ACQ-C) wood preservative was investigated to determine the effects of delayed drying and application of CO₂ gas under pressure. Unlike the fixation of CCA preservative, where the rate of fixation reaction is slowed down by evaporative cooling during drying, delayed drying of ACQ treated wood had no observable effect on the copper fixation rate. However, at 50 °C, delayed drying resulted in a higher degree of copper fixation, while this effect was not observed at 22 °C. Post-treatment of ACQ treated wood with pressurized CO₂ immediately after treatment, reduced the pH of the solution in wood and resulted in rapid fixation of the copper. However, in time, the pH increased as CO₂ dissipated from the solution allowing the copper to re-solubilize.     

Quality Assurance of Model Infant Milk Formula Using a Front-Face Fluorescence Process Analytical Tool

Front-face fluorescence spectroscopy (FFFS) was evaluated as a quality assurance process analytical technology (PAT) tool for infant milk formula (IMF) manufacture. Batches of first-stage IMF (60:40 whey protein:casein ratio) powder were produced with protein:fat:lactose ratios of 1.3:3.6:7.3, differing only in heat treatment applied prior to spray drying (72, 95, or 115 °C for 15 s). Each IMF powder was stored at 15?±?2 °C and 37?±?2 °C and analyzed at months 0, 3, 6, and 12. Partial least squares (PLS) models were developed for IMF in both powder and liquid states using FFFS spectra to predict pre-drying heat treatment temperature, soluble protein content, and storage time. Models developed using tryptophan emission spectra for IMF powder predicted storage time, pre-drying heat treatment temperature, and soluble protein content with RMSECV values of 0.3 months, 8.3 °C, and 1.01 g protein/100 g powder, respectively. IMF powders were rehydrated to 13% total solids and analyzed using the vitamin A emission spectra. Models developed for rehydrated IMF predicted storage time and pre-drying heat treatment temperature with RMSECV values of 1.5 months and 6.7 °C, respectively. Surface free fats were predicted with an RMSECV range of 0.12–0.20% (w/w of powder) in rehydrated IMF. PLS discriminant analysis models developed for both powder and liquid IMF samples successfully discriminated for storage temperature. This preliminary study demonstrates the strong potential of FFFS as a PAT tool for IMF quality assurance.     

Effect of high-temperature drying on properties of Norway spruce and larch

In timber drying, mechanical properties may be changed due to treatment temperature and treatment duration. In general, when increasing the kiln temperature, drying time is decreased and some timber properties are negatively affected. In this study, the effect of different drying temperatures (80, 120 and 170 °C) on equilibrium moisture content and sorption rate, on bending strength and stiffness was investigated for Norway spruce and larch from four proveniences and the results were compared to those obtained for heat-treated wood (Thermowood ^®). The experiments confirm earlier research that both treatment temperature and treatment duration affect the properties. High-temperature drying or treatment can be optimized for several applications, yielding strong but not so durable timber or vice versa.     

Influence of drying temperature upon some mechanical properties of beech wood

The paper presents the results obtained in an experimental study concerning the influence of drying temperature upon the mechanical properties of beech wood (Fagus sylvatica L.). Sound wood samples without red heart were cut from white (unsteamed) beech timber parts, dried at different temperatures: 20 °C, 80 °C, 90 °C, 100 °C, 115 °C and same relative air humidity: 50%. After performing classical tests for evaluation of some selected mechanical properties, the following conclusions could be drawn: all bending properties (static bending strength, modulus of elasticity and impact bending strength) increased with increasing temperature, confirming thus the benefiting effect of heat upon wood plasticity. The tensile strengths, both parallel and perpendicular to grain, increased with increasing temperature, but only in the range below 100 °C; as soon as the temperature exceeded this value, the tensile strengths began decreasing. As far as compression strength parallel to grain, shearing strength and splitting resistance is concerned, no significant influence of temperature could be established. However, it seems that these properties are negatively affected by kiln-drying, as even with low kiln-drying temperatures these strengths are much lower than in case of air-drying.     

Measurement of wood grain angle, moisture content and density using microwaves

In many wood products manufacturing processes, it is important to ensure that the physical properties of the raw material lie within acceptable ranges and are measured reliably. It is also important for practical use that the measurement process is robust, low-maintenance, fast and preferably non-contacting. This paper describes the development and demonstration of a microwave system for simultaneously identifying wood grain angle, moisture and density. The method involves propagating a microwave beam through the wood and measuring the resulting depolarization, attenuation and phase shift. The wood physical properties can then be identified from these measurements. In a series of measurements, the prototype microwave system successfully identified wood grain angles for hemlock and Douglas fir respectively with standard errors of 0.9° and 2.5° (measured range = -90° to +90°), moisture content 1.2% and 1.9% (measured range = 7–28%), moisture density 3.7 kg/m³ and 7.9 kg/m³ (measured range = 40–150 kg/m³, and dry density 16 kg/m³ and 30 kg/m³ (measured range = 325–625 kg/m³).     

Mathematical modeling of uvaia byproduct drying and evaluation of quality parameters

Uvaia (Eugenia pyriformis) frozen pulp processing generates a solid byproduct that can potentially contain important components of human nutrition. In this study, the drying of uvaia byproduct was studied. Two different drying treatments were tested: drying of wet waste and drying of waste with prior removal of water by centrifugation. Three drying temperatures were used: 40, 60, and 80 °C. Eight models were applied to fit the drying curves: Page, Lewis, Modified Page, Logarithmic, Midilli, Wang and Singh, Henderson and Pabis, and Weibull. Midilli presented an excellent fit to the curves. The effective moisture diffusivity of the uvaia byproduct ranged between 8.52 × 10^?10 and 3.22 × 10^?9 m²/s. The activation energy was 25.65 and 24.97 kJ/mol for non-centrifuged and centrifuged assays, respectively. The dried byproducts had a reduction of 3–21% of the total phenolic content against the control. The assay performed at 40 °C with centrifugation presented the lowest total color difference value.     

Bio-transformed sawdust by white rot fungi used as a carrier for plant growth-promoting bacteria

This study assessed the bio-transformation of sawdust wood waste by a white rot fungi consortium and explores the use of the final product as a carrier for plant growth-promoting bacteria. During 75 days, Tabebuia roseae and Eucalyptus pellita (1:1) sawdust wood were used as growing substrates for Ganoderma lucidum, Pleurotus ostreatus, Trametes versicolor and Phanerochaete chrysosporium. Then, bio-transformed sawdust was evaluated as carrier of two strains of Enterobacter sp. and one strain of Stenotrophomonas maltophilia. Biologic activity and viability were determined at two storage temperatures (23–4 °C) for 60 days. Sawdust mixture was bio-transformed by white rot fungi. After 45 days, the carbon/nitrogen ratio was reduced up to 46 %, and 4.8 mg/g of CO₂ of residue was produced. Enzymatic activities attained a peak of 36.7 and 0.8 U g^?1 for laccase and manganese peroxidase, respectively in 45 days. Population of plant growth-promoting bacteria immobilized in bio-transformed sawdust wood decreased to 10⁵ CFU g^?1. However, this concentration and its biologic activity remained stable at 23 °C.     

Combination of hot air drying and deep‐fat frying to reduce the oil content in chicken nuggets

The combination of hot air drying and frying to reduce oil uptake in chicken nuggets was analysed. Two air velocities (2 and 4 m s^?1) and two dry bulb temperatures (44 and 61 °C) were employed in the drying process, as a treatment before or after deep‐fat frying at 160 °C for 90 s in fresh soybean oil. The lowest fat content was obtained by frying followed of drying at 61 °C with air velocity of 2 m s^?1. When drying was applied before frying, mass transfer (moisture loss) during the drying process was modelled according to Fick’s second law; diffusion coefficients ranged between 1.03 and 3.33 × 10^?6 m² s^?1. When drying was applied after frying, a constant rate period was observed during drying process, with velocities between 0.002 and 0.02 kg_water/kg_{dry solids}·min. Scanning electron microscopy (SEM) allowed to observe differences in the topography of chicken nuggets obtained from frying or the combination of frying and drying.     

Prediction of non-recoverable collapse in Eucalyptus globulus from near infrared scanning of radial wood samples

Near infrared (NIR) spectroscopy calibrations was used to predict radial profiles of cellulose content, wood density, cellulose microfibril angle (MFA) and modulus of elasticity (MOE) in 20-year-old plantation Eucalyptus globulus to identify non-recoverable collapse zones associated with tension wood. Radial (cambium-to-pith) wood cores were extracted at a height of 1.0 m from trees selected to represent a range of silvicultural treatments. NIR spectra were measured at 1 mm intervals along the radial-longitudinal face of each core after drying to 12 % equilibrium moisture content (EMC) at 40 °C. Tangential shrinkage was measured at eight points along each core, following steam reconditioning and re-drying to 12 % EMC. Additional cores from 20 of the sample trees were collected. Radial profiles of density, MFA and MOE were obtained for wood strips prepared from these cores, using the SilviScan 3 wood assessment system. Trait profiles were matched to radial NIR scans of these cores, enabling the development of NIR calibrations using partial least squares (PLS) regression. These, and an existing NIR calibration for cellulose content, were used to predict the radial profiles of the four wood properties for the first set of cores. Predicted wood properties were then related to actual tangential shrinkage measurements and the occurrence of visible bands of non-recoverable collapse. A regression model was developed to reliably predict regions of non-recoverable collapse from NIR-predicted cellulose content and MOE. Micrography of stained wood sections indicated that the collapse was caused by the presence of tension wood.     

Microwave drying of pine and spruce

Drying rates and power densities are determined for pine-and sprucewood when dried from green to 8% moisture content by microwave power. The process is controlled by measurements of internal wood temperature, internal vapour pressure and rate of moisture evaporation. Microwave power densities ranged from 25 to 78 kW/m³, microwave energy consumption from 365 to 760 kWh/m³. Internal wood temperatures up to 140 °C were used. Internal vapour pressure in the wood could rise to about 20 kPa without checking. Maximal drying rates of 0.20 to 0.45% moisture content per minute are possible to obtain when drying above fiber saturation (fsp). Below fsp the feasible drying rates ranged from 0.10 to 0.20% moisture content per minute. Spruce dried approximately 1.6 times faster than pine. No conditioning of the wood was necessary since the wood was free of stresses. The wood was free of checks but colour changes occured in the interior of some specimens.     

Physical,mechanical and biological properties of thermo-mechanically densified and thermally modified timber using the Vacu<Superscript>3</Superscript>-process

Densification and thermal modification change wood properties in different ways depending on the treatment conditions and the wood species. In the presented investigations, densification and thermal modification were applied consecutively. The primary objective of this treatment combination was the compensation of reduced mechanical properties due to the thermal modification by densification. The combined processes were applied to five European wood species: poplar (Populus nigra L.), beech (Fagus sylvatica L.), Norway spruce (Picea abies Karst.), English oak (Quercus robur L.) and European ash (Fraxinus excelsior L.). Depending on the mean density of the species, a thermo-mechanical densification of 43 or 50% was imposed to improve mechanical strength parallel to the grain. Subsequently, the densified material was thermally modified in the so-called Vacu³-process at 230 °C and 20 or 80% vacuum and at 240 °C and 20% vacuum. The thermal modification resulted in changing wood colour, mechanical strength, hardness, dimensional stability and durability. All the wood modification processes were carried out at industrial scale after pre-tests at laboratory scale. The modified material was characterized regarding flexural properties, static and dynamic hardness, structural integrity, abrasion resistance, moisture dynamics, dimensional stability, and durability against white, brown and soft rot fungi. In summary, the test results showed that the consecutive application of thermo-mechanical densification and thermal modification leads to significantly improved durability whilst mechanical properties at least for beech, ash and poplar remained and the material is dimensionally stable.     

Studies on the toxicity of phosphine to tolerant stages of Trogoderma granarium Everts (Coleoptera: Dermestidae)

Tests were conducted at 20 and 30°C at 60% r.h. to find the dosages of phosphine needed for control of diapausing larvae and eggs of Trogoderma granarium. At 20°C, 60% r.h., some larvae from each of four recently acquired field strains of T. granarium survived a 5-day exposure period at a concentration-time (Ct) product of 164 g hr/m³. Under these conditions laboratory stock larvae were killed by a 4-day exposure period of about 120 g hr/m³, and eggs by a 3-day exposure of about 50 g hr/m³. Eggs, aged 0–1 days, proved the most tolerant stage at 30°C, 60% r.h., surviving a Ct-product of 16 g hr/m³ over a 2-day exposure period. At 30°C the diapause of larvae became unstable and their tolerance of phosphine was low. Adults emerging after fumigation of larvae appeared normal and if sufficient numbers emerged together a second generation was produced.Complete control of larvae of several stocks (about 20 weeks in diapause) was achieved within a 4-day exposure at 20°C with a mixture of methyl bromide (2.0 g/m³) and phosphine (1.4 g/m³), whereas 6 days were required for these stocks using phosphine alone. To ensure elimination of all stages of non-resistant T. granarium, exposures to phosphine should last 7 days at 20°C and 4 days at 30°C.