The objective of this project was to provide the information required by Canadian lumber producers to evaluate the superheated steam/vacuum (SS/V) drying process by comparison with conventional methods as applied to 4/4-inch red oak with respect to drying time, final product quality, efficiency and costs. The study was divided into two parts. In the first part, three loads of red oak were dried in Forintek’s eastern SS/V kiln to identify a suitable schedule with respect to time and quality. In the second part, comparative tests were conducted between the SS/V kiln and a conventional kiln of similar capacity. The tests involved measurements of drying time as well as wood quality before and after the drying operation, including distortion, drying checks and splits, final moisture content (MC) gradient, shrinkage, and residual stress (prong test). Energy consumption was also measured for the SS/V and conventional kilns. Finally, drying costs were evaluated for the two systems in an industrial scenario.
We successfully developed a schedule to efficiently dry 4/4-inch red oak through the SS/V process. With this schedule, 4/4-inch red oak can be dried in approximately a third of the time required for a similar load in the conventional kiln. Our results from parallel measurements indicate that the final quality of the wood dried with the SS/V process is quite comparable to that obtained with conventional drying. In addition, quality results proved achievable without a conditioning phase at the end of the cycle. Parallel drying tests conducted on similar loads of 4/4 red oak indicated that total energy consumption was 15% lower with the SS/V kiln than with the conventional kiln. A comparison of drying costs for the two systems based on annual production of 10 million fbm suggested that capital and operating costs might be slightly lower with the SS/V kiln.
The objective of this project was to provide the information required by Canadian lumber producers to evaluate the superheated steam/vacuum (SS/V) drying process as applied to 8/4-inch red oak with respect to productivity, final product quality, efficiency and energy consumption. Another objective was to compare SS/V drying with conventional drying in terms of productivity and wood quality.
Two homogeneous test loads were prepared from a single lumber lot for the SS/V and conventional tests. Initial lumber moisture content in the two loads averaged 28%. The tests involved measuring drying time as well as wood quality before and after the drying operation, including: distortion, drying checks and splits, final moisture content gradient, dimensional shrinkage, and residual stresses (prong tests). In addition, the tests included measurements of energy consumption, both thermal and electrical, with meters. The schedule used for conventional drying was drawn from Boone et al. (1993) and that for SS/V drying was supplied by Iwotech, the equipment manufacturer. In both cases, the drying cycle was terminated when the all boards used for control had reached the 7 ± 1.5% moisture content range.
Drying was achieved in 7.6 days with the SS/V process, representing a significant reduction (by a factor of 2.2) relative to the time required with the conventional method; and wood quality after drying was comparable. The results obtained with respect to distortion, checking, moisture content gradients, and residual stresses attest to the quality of the drying operation with both processes. Total energy consumption for the SS/V process was 11,307 kJ/kg of evaporated water with 58% as thermal energy and 42% as electrical energy.
The objective of this project is to provide the information required by Canadian lumber producers to evaluate the superheated steam/vacuum (SS/V) drying technology as applied to 8/4-inch red oak with respect to drying time, final wood quality, and energy consumption. Two loads of red oak were dried in Forintek’s eastern SS/V kiln with the objective of identifying a suitable schedule with respect to time and quality. The tests involved measurements of drying time as well as wood quality before and after the drying operation, including distortion, drying checks and splits, final moisture content gradient, shrinkage and residual stress (prong test). Energy consumption of the SS/V kiln was also measured.
We were able to develop a schedule to efficiently dry 8/4-inch red oak through the SS/V process. With this schedule, an industrial load of 8/4-inch red oak can be dried in a quarter of the time typically required in conventional kilns. Our results indicate that quality drying is achievable with the SS/V process if the set point temperature is kept relatively low and the relative humidity relatively high while the wood is above the fibre saturation point. 8/4-inch red oak dried by the SS/V process required no conditioning phase to equalize moisture contents at the end of the cycle. Energy consumption measurements indicate that the process used more electrical energy than thermal energy, this being due to the relatively long time required to dry 8/4-inch red oak.
The objective of this project was to provide the information required by Canadian lumber producers to evaluate the superheated-steam/vacuum (SS/V) drying technology as applied to 8/4-inch white oak with respect to productivity, wood quality, and energy consumption.
A drying test was conducted on a load consisting mostly of lumber in the Select&Better grade. Initial board moisture contents averaged 53.1%. The tests involved measurements of drying time as well as wood quality before and after the drying operation, including: distortion, drying checks and splits, final moisture content gradient, dimensional shrinkage, and residual stresses (prong tests). In addition, the tests included measurements of energy consumption, both thermal and electrical, with meters. A schedule that had been used successfully in SS/V drying tests with 8/4-inch red oak was used for this test.
A total of 21.6 days was required to reduce the lumber moisture content from 53% to 16%. In fact, this result underestimated actual drying time due to the cycle being interrupted prematurely and to relative humidity in the kiln at the beginning of the cycle being lower than set. As a result, a significant increase in surface and internal drying checks was observed. Relative humidity lower than the set point at the beginning of the cycle may account for such checking. The average final moisture content gradient of 12.3% was attributed to the cycle being interrupted when overage moisture content was still higher than target. Prong tests showed no indication of significant residual stresses, even though no conditioning had been performed. Total energy consumption was 18,602 kJ/kg of evaporated water with 48% as thermal energy and 52% as electrical energy.
This manual is intended to serve as an educational resource and working tool for people actively involved in the drying of Spruce-Pine-Fir (SPF) lumber. The manual covers subject matter from the basic principles of drying through to the application of techniques specific to the drying of this species group. The range and depth of information presented has been selected to meet these objectives.
Disponible en français: https://library.fpinnovations.ca/en/permalink/fpipub7507
Lumber warp is the primary cause for drying degrade. Over the past decade, Canadian producers have been paying increasing attention to the box-store market and that of engineered wood products such as wood I-joists and glued-laminated beams (glulam). One characteristic of these markets is that they require straight and stable lumber. The objective of this study was to determine the effect of sticker spacing on stickering costs and lumber quality.
To address this objective, we conducted tests in three stud mills. Stickers were added as required for the assessment of 48-, 32-, 24- and 16-inch spacings, i.e. 3, 4, 5 and 7 stickers respectively with 8-foot lumber. The bundles of test lumber were dried in a single load in all mills. After drying, the lumber was graded by a grading agency inspector. He determined the potential grade before drying and the actual grade after drying for each piece of lumber. The moisture content (MC) of the test lumber was also determined on a sample basis.
In Mill 1, we observed that drying degrade for the entire sample was reduced from 2.2 to 1.3% in the bundles spaced at 24 inches, which represented a gain of $3.21/Mbf. As for lumber meeting the requirements for the special grade, degrade was reduced from 71.3 to 49.5%, which is a gain of $10.41/Mbf.
In Mill 2, drying degrade decreased from 32.1 to 26.3% when sticker spacing was reduced from 48 to 32 inches, for an approximate gain of $1/Mbf. In this particular mill, a 16-inch spacing failed to improve performance over a 32-inch spacing.
As for Mill 3, reducing sticker spacing from 48 to 24 inches decreased drying degrade in the special grade lumber by half, leading to a $5.33/Mbf gain. Drying degrade decreased regularly from 48 to 32 inches and from 32 to 24 inches. Closer spacing benefited lumber quality at both the top and the bottom of the stacks.
Optimal spacing in a sawmill should be based on species and stickering costs. As costs vary widely from mill to mill, the report provides information to help users calculate additional stickering costs. We observed significant gains from reduced sticker spacing. Twenty-four-inch spacing should become standard practice in the manufacture of quality lumber. As a rule, closer spacing requires only limited investments, i.e., the acquisition of additional stickers and, occasionally, minor modifications to the stickering equipment.
Identification des stratégies optimales de triage des bois EPS. Étape : Évaluation des technologies de prétriage - température près du point de congélation
Ce projet vise à mettre au point une méthodologie et des outils pour aider les usines à évaluer les différentes solutions de triage offertes pour le séchage de bois du groupe EPS et identifier les solutions optimales spécifiques. L’étape du projet faisant l’objet du présent rapport consiste plus particulièrement à évaluer différents systèmes de triage offerts sur le marché dans des conditions hivernales (température du bois sous le point de congélation).
Quatre systèmes de triage ont été évalués soit le Préclasseur 3DELTA de Fabrication Delta, le MC-Pro 1500 de NMI, l’optimisateur de séchage du sapin et de l’épinette d’AUTOLOG (SAPTEK) et le système de pesée dynamique SPD de VAB Solutions. Les 3 premiers systèmes ont été testés à l’usine d’AbitibiBowater de Maniwaki tandis que le système par pesée dynamique SPD a été testé à l’usine de Canfor à Daaquam, mais en utilisant le même échantillon de sciages à l’état vert.
La proportion d’essences des pièces de l’échantillon était de 41 % d’épinette, 21 % de pin et 38 % de sapin. Les pièces ont été mesurées avec les systèmes dans des conditions de température du bois variant de -2 à 2°C. L’objectif consistant à évaluer les systèmes alors que la température du bois était sous le point de congélation n’a pas été atteint. Les pièces retenues pour fin d’analyse ont été séchées pour permettre d’obtenir la courbe de séchage pour chaque pièce. De cette façon, il a été possible de déterminer le temps de séchage pour chaque pièce à toute teneur en humidité intermédiaire ou l’inverse.
Tous les systèmes étudiés ont montré des gains significatifs en productivité pour un triage en deux lots de l’échantillon d’essences mélangées. Le potentiel maximal théorique de gain en productivité par le triage en deux lots est de 33,4 %. Le système 3DELTA a montré des gains en productivité de 28,9 %, le système SAPTEK de 28,4 %, le système MC-Pro 1500 de 24,9 % et le système de pesée dynamique SPD de 18,3 %.
À l’intérieur du groupe d’essence épinette/pin, le potentiel maximal de gain en productivité de l’échantillon trié en deux lots est de 8,6 %. Le système de pesée dynamique a montré un résultat de gain en productivité au séchage de 4,1 %, le système MC-Pro 1500 de 3,3 %, le système 3DELTA de 2,9 % et le système SAPTEK de 2,1 %. À l’intérieur du sapin, le potentiel maximal de gains en productivité de tri en deux lots est de 14,7 %. Le système de pesée dynamique SPD a obtenu un résultat de gain en productivité de 6,3 %, les systèmes 3DELTA et MC Pro-1500 de 3,5 % et le système SAPTEK de 3,3 %.
Le gauchissement des sciages est le principal facteur responsable du déclassement du bois de construction lors du séchage. Dans la dernière décennie, les industriels canadiens se sont intéressés au marché des magasins entrepôts à grande surface et des bois d’ingénierie, comme les poutrelles en I et le bois lamellé-collé. La fabrication de ces produits nécessite entre autres des bois droits et stables. L’objectif de cette étude est de déterminer l’impact de l’espacement des lattes sur la qualité et les coûts de lattage pour le bois de construction.
Des tests pour évaluer l’impact de l’espacement des lattes ont été effectués dans trois usines de bois de colombage. Des lattes ont été ajoutées lorsque nécessaire pour évaluer des espacements de 48, 32, 24 et 16 pouces, ce qui correspond respectivement à 3, 4, 5 et 7 lattes pour des sciages de 8 pieds. Les paquets ont été séchés dans le même chargement à chacune des usines. Après séchage, les paquets furent classifiés par un inspecteur d’une agence de classification. Pour chacune des pièces des paquets, l’inspecteur a déterminé le classement potentiel avant séchage et le classement après séchage. Un échantillonnage de l’humidité du bois a aussi été réalisé.
Une réduction du taux de déclassement de l’ensemble de la production de 2,2 % à 1,3 % a été observée pour les paquets ayant un espacement de 24 pouces à l’usine 1, soit un gain de 3,21 $/Mpmp. Pour ce qui est des pièces ayant le potentiel de faire la classe de qualité spéciale, le déclassement est passé de 71,3 % à 49,5 % pour un gain de 10,41 $/Mpmp.
À l’usine 2, le taux de déclassement de la production complète a diminué de 32,1 à 26,3 % avec une réduction de l’espacement de 48 à 32 pouces, pour un gain d’environ 1 $/Mpmp. L’espacement de 16 pouces n’a pas offert une performance supérieure à l’espacement de 32 pouces pour cette usine.
En ce qui a trait à l’usine 3, la réduction de l’espacement de 48 à 24 pouces a permis de diminuer le déclassement de moitié pour la classe de qualité spéciale, soit un gain de 5,33 $/Mpmp. Le taux de déclassement a diminué de façon régulière de 48 à 32 pouces et de 32 à 24 pouces. La diminution de l’espacement permet de diminuer le déclassement autant pour les paquets du dessus du chargement que ceux du bas.
Le choix de l’espacement optimal des lattes pour une usine doit se faire en fonction des essences séchées et du coût de lattage. Comme ces coûts sont très variables d’une usine à l’autre, des données pour faciliter le calcul des coûts supplémentaires de lattage sont fournies dans ce rapport. Des bénéfices importants ont été observés lors de la diminution de l’espacement des lattes. Un espacement de 24" devrait devenir une pratique régulière lors de la fabrication de produits de qualité. En général, la réduction de l’espacement des lattes nécessite peu d’investissements, soit l’acquisition de lattes supplémentaires et quelquefois des modifications mineures aux équipements de lattage.
