Wood Moisture Research Articles

Influence of the type and output of domestic hot-water boilers and wood moisture on the production of fine and ultrafine particulate matter

Abstract The Ministry of the Environment of the Czech Republic within the Operational Programme Environment of the European Union (EU) has supported a ‘grant to replace old boilers’ from 2015 to 2020. The aim was to replace outdated, non-ecological, solid-fuel boilers with modern low-emission boilers (for the combustion of biomass, coal, or a combination), heat pumps, gas boilers, or solar systems. All heat sources must comply with the Ecodesign Directive of the EU. According to the Air Protection Act in the Czech Republic, commencing in 2022, outdated boilers of the 1st and 2nd emission classes will no longer be operable in households. The grant also aimed to reduce particulate matter (PM), organic gaseous compounds, and CO and NOx emissions. Our goal was to compare the PM emissions of four boilers: an outdated overfire boiler (B1), an outdated boiler with down-draft combustion (B2), a new gasification boiler (B3), and a new automatic boiler (B4). A Dekati low-pressure cascade impactor was used to determine the mass concentration of individual dust fractions; a scanning mobility particle sizer SMPS 3936 was utilized to determine the particle size distributions of the dust particles. Dry and wet spruce wood and wood pellets were combusted. Regarding the mass concentration of the PM and specific emissions (SE) of individual size fractions, they were much higher in boilers of older types (B1 and B2), while the reduction in SE of PM was very significant in boilers of newer types (B3 and B4). However, the SE of ultrafine particles (PM0.1) from the newer boilers remained in a range similar to that of B1 at a reduced output (Pmin) and B2.

Moisture Performance of Façade Elements Made of Thermally Modified Norway Spruce Wood

Wooden façades are gaining in importance. Thermally modified wood is becoming one of the preferred materials for claddings. In spite of the fact that façades made of thermally modified wood have been in use for more than two decades, reports about long-term monitoring have been sparse. The results of three-year monitoring of a façade made of thermally modified wood in Ljubljana are reported. Moisture content measurements of thermally modified façades were taken at 22 locations and compared to the moisture content of untreated Norway spruce wood. Temperature and relative humidity were recorded in parallel. The moisture content of the wood was compared to the average relative humidity before the measurements. The results confirm the lower moisture content of thermally modified wood in comparison to reference Norway spruce. The moisture content of the wooden façade could be best correlated with the average relative humidity and temperature 48 h before the wood moisture content measurement was taken.

Effects of Wood Moisture Content and the Level of Acetylation on Brown Rot Decay

Acetylation is one of the most common types of wood modification and is commercially available throughout the world. Many studies have shown that acetylated wood is decay resistant at high levels of acetylation. Despite its widespread use, the mechanism by which acetylation prevents decay is still not fully understood. It is well known that at a given water activity, acetylation reduces the equilibrium moisture content of the wood cell wall. Furthermore, linear relationships have been found between the acetylation weight percent gain (WPG), wood moisture content, and the amount of mass loss in decay tests. This paper examines the relationships between wood moisture content and fungal growth in wood, with various levels of acetylation, by modifying the soil moisture content of standard soil block tests. The goal of the research is to determine if the reduction in fungal decay of acetylated wood is solely due to the reduction in moisture content or if there are additional antifungal effects of this chemical treatment. While a linear trend was observed between moisture content and mass loss caused by decay, it was not possible to separate out the effect of acetylation from fungal moisture generation. The data show significant deviations from previously proposed models for fungal moisture generation and suggest that these models cannot account for active moisture transport by the fungus. The study helps to advance our understanding of the role of moisture in the brown rot decay of modified wood.

The Problem of Compressive Strength in Direction Perpendicular to the Grains on Example of Tests of the Load-Bearing Capacity of the Continuously Supported Timber-Frame Sill Plates.

This paper presents a discussion of the problem of compressive strength in a direction perpendicular to the grains based on test results of the joints made by timber posts and sill plate. These tests accompanied a larger series of full-scale tests of timber frame walls. The test elements were made of solid softwood (spruce). The wood moisture was low, which corresponds to the real working conditions of these elements in the walls of a building (low humidity is typical for dry wood in the built-in wall of a real building). In the tests, the compression strength of timber perpendicular to the grain was exceeded in the sill plate in the area in contact with the posts. Shortly before reaching the state of failure, large displacements in the sill plate were measured on the contact surface with the post, and the grains in the sill plates were cut off at the edge of the post. The full-scale test results showed an overestimation of the load-bearing capacity in compression perpendicular to the grain when calculated on the basis of EN 1995-1-1+A1:2008 (Eurocode 5), and, therefore, the need to modify the current approach for determining it.

Thermal conductivity and deformation of Taxodium hybrid ‘Zhongshanshan’ during heat transfer process

The thermal conductivity and the deformation of wood from the Taxodium hybrid ‘Zhongshanshan’ were studied in the process of heat transfer. The results showed that the average thermal conductivity of this wood was 0.1257 W/(m·K) under the condition of 12% wood moisture content and 30 °C heat transfer temperature. When the testing temperature exceeded 0 °C, the thermal conductivity increased linearly with both temperature and wood moisture content and was affected by the moisture content of the wood. During the heat transfer process, the deformation of features caused repeated swelling and shrinkage in the longitudinal, radial, and tangential directions. The dimensional change was greatly affected by the wood’s moisture content and was less affected by the temperature. These results are of great meaning for the study of the heat transfer process of Taxodium hybrid ‘Zhongshanshan’ wood. Furthermore, it provides a scientific basis for the heat preservation effect, drying treatment, and pyrolysis treatment of Taxodium hybrid ‘Zhongshanshan’ wood for use as a building material.

The growth, pilodyn penetration, and wood properties of 12 Neolamarckia cadamba provenances at 42 months old

Abstract. Anna N, Supriyanto, Karlinasari L, Sudrajat DJ, Siregar IZ. 2020. The growth, pilodyn penetration, and wood properties of 12 Neolamarckia cadamba provenances at 42 months old. Biodiversitas 21: 1091-1100. Jabon (Neolamarckia cadamba (Roxb) Bosser) is a potential tree species for the development of plantation forests and community forests to supply timber demands. Information on the growth characteristics and wood properties of N. cadamba is important for the present and future development, yet. Those data is not available. This study aimed to assess the variations on growth (height, diameter), pilodyn (Pilodyn®) penetration, and physical properties of wood from core sample; and characterize the wood properties of 12 N. cadamba provenances at Parung Panjang, Bogor. The assessment of growth characteristics, pilodyn penetration, and physical properties of wood from core sample was carried out through census (1030 trees) on all provenance (using non-destructive method). The wood properties analysis was carried out using destructive method to one sample for each of the 12 N. cadamba provenances. Growth characteristics observed were the height (numerical scale pole), diameter (calipers), and pilodyn penetration. Meanwhile, the wood properties consisted of wood density, specific gravity, moisture content, fiber length (light microscope), MFA (x-ray diffraction), MOE, and MOR. The results showed that the correlation between the height and moisture content with pilodyn penetration was weak and positive, while the correlation between diameter, wood density, and specific gravity was weak and negative. The result of non-destructive test showed that Gowa provenance is superior. The results of destructive tests to investigate the wood properties of the twelve provenances showed that Batu Licin provenance is superior in terms of specific gravity and MOE, while Gowa provenance is superior in terms of MOR and fiber length. The results of the wood properties (i.e. density, specific gravity, moisture content, MOE, MOR, MFA, and fiber length) of the 12 N. cadamba provenances showed that the woods can be potentially used as non-structural materials only.

RETRACTED ARTICLE: The effect of soil nutrients and moisture during ontogeny on apparent wood density of Eucalyptus grandis

Knowledge of the effect of soil nutrients, such as K and Na and their interaction with water availability, on the growth and wood properties of the eucalypts, is needed to increase the productivity of commercial plantation forests in Brazil that generate employment and taxes. The present study evaluates the apparent wood density (at 12% wood moisture) of Eucalyptus grandis trees at 12, 24, 36 and 48 months old under ambient and lower than ambient (66%) rainfall conditions and K and Na nutrient enrichment. The treatments were two water availability (100 and 66% of the rainfall) and the three nutrient treatments were: K (4.5 kmol/ha), Na (4.5 kmol/ha) and a control (natural conditions). The apparent wood density of samples at breast height (1.3 m) was determined by X-ray densitometry and digital images. Increased nutrients at all four ages and water availability at 36 and 48 months reduced apparent wood density in E. grandis trees, however, effects of nutrients are lower under water availability reduction. The radial profile of wood density was higher in four-year-old trees, but there was radial variation in apparent wood density at all ages. These findings predict that, under water stress, apparent wood density will not decline in commercial E. grandis plantations fertilized with potassium. The use of sodium, as a substitute of potassium, should consider their negative impacts on wood density of Eucalyptus grandis trees.

Prediction of moisture content of wood using Modified Random Frog and Vis-NIR hyperspectral imaging

Vis-NIR hyperspectral imaging was adopted to predict the moisture content (MC) of wood. A total of 30 beech blocks were used in the experiments, each block was dried 7 times to generate different cases of moisture contents. The 210 samples were divided into a calibration set (140) and a prediction set (70) using Kennard-stone (KS) algorithm. The spectral data of each sample was collected by the hyperspectral imaging system, and pretreated using standard normal variate (SNV). To solve the problem that the random frog algorithm (RF) needs to reset threshold after obtaining the selection probability of all variables at a time, adaptive reweighted sampling (ARS) and exponentially decreasing function (EDF) are applied to improve RF in this paper. The modified RF (MRF) was compared with RF, successive projections algorithm (SPA) and competitive adaptive reweighted sampling (CARS). Based on the full spectrum data (FS) and four characteristic spectral data, different models were built using Gaussian process regression (GPR). The results show that the MRF not only avoids setting thresholds, but also improves the stability and accuracy of the model. The MRF-GPR model achieved the best predictive performance of wood moisture content, with Rp2, RMSEP of 0.9785, 1.6125%, respectively. So the hyperspectral imaging technique is suitable for predicting the moisture content of wood.

Моделирование процесса сушки пиломатериалов

The article considers the problem of sawn timber drying. The relevance of research is driven by the need to improve the automated process control system for drying sawn timber on the basis of modern information technologies, as well as to reduce the energy intensity of these technologies, which is enshrined in the program documents of forest industry development at the government level. The functional purpose of the automated control system is to provide a set level of the wood moisture content with the required quality of wood (zero ruptures). It is of immense complexity to obtain such functional dependency on the heating temperature in the chamber and the equilibrium air humidity by traditional statistical methods due to the uncertainty conditions of parameters, therefore, the apparatus of the fuzzy set theory should be used. Thus, the research purpose included generation of functional dependences of the sawn timber moisture content and drying time on the heating temperature and the equilibrium air humidity in the drying chamber based on fuzzy inference. The methodological basis of the theoretical studies was as follows: the theory of drying; the provisions of athematical and fuzzy modeling; and, in terms of checking the adequacy of the proposed fuzzy model, the methods of mathematical statistics and experimental theory. The research results are the obtained dependences of the moisture content of sawn timber and drying time on the heating temperature and the equilibrium air humidity in the drying chamber, the synthesis of which is performed by means of Fuzzy Logic Toolbox of MATLAB application. The proposed functions of the moisture content and sawn timber drying time take into account the basic process configurations (the heating temperature and the equilibrium air humidity) and are experimentally verified for adequacy. The practical applicability of the results lies in the possibility of creating an intelligent system of automatic control of the sawn timber drying process. For citation: Gorokhovsky A.G., Pobedinsky V.V., Shishkina E.E., Pobedinskiy E.V. Modeling the Process of Sawn Timber Drying. Lesnoy Zhurnal [Russian Forestry Journal], 2020, no. 1, pp. 154–166. DOI: 10.37482/0536-1036-2020-1-154-166

Monitoring a building made of CLT in Ljubljana

ABSTRACT The importance of renewable and environmentally acceptable materials in the construction industry is increasing. Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades, mainly due to the development of modern composites, firstly glue lam, OSB (Oriented Strand Board), LVL (Laminated Veneer Lumber) and a considerable breakthrough was later achieved with the development of cross-laminated timber. In order to enable even more extensive and reliable use of wood in outdoor applications, factors affecting a wood’s service life need to be understood. It is well known that fungal degradation of wood is predominantly affected by temperature and wood moisture content. In order to elucidate the influence of these two factors, long-term monitoring of temperature, relative humidity and moisture content at the newly-built Annex of the Department of Wood Science and Technology was carried out. The Annex is designed from CLT composites and glue-lam beams and was finished in December 2015. The results clearly show that microclimatic conditions in the monitored building in the first years of use are far below the limit required for fungal decay or mould growth.

Failure under stress of grapevine wood: The effects of the cerambycid Xylotrechus arvicola on the biomechanics properties of Vitis vinifera

Xylotrechus arvicola is an insect pest on Vitis vinifera in the main wine-producing regions of Spain. X. arvicola larvae bore inside grapevine wood, which cause structural damages in the plants´ biomechanical properties. Grapevine wood affected and unaffected by larvae, were collected from vineyards. Compression and flexural tests were used to quantify biomechanical wood properties. Affected wood broke more quickly and endured a lower supported force than unaffected wood in both varieties and moisture states. Tempranillo was the most resistant variety on trunks, while Cabernet-Sauvignon was the most resistant variety on branches, where all infested varieties showed a lower rate of bending. Grapevine wood affected by X. arvicola larvae shows an important decrease in its resistance in both moisture states - dry and wet wood - and it is observed due to the faster break in time and a lower supported force. These damages give the affected wood greater sensitivity to external mechanical factors in the vineyards, such as strong winds, harvest weight and the vibration exerted by harvesting machines. The aspect of stress-time curves in all cases follow similar patterns, so in future studies might be possible to stablish relationships between both wet and dry samples and different infestation levels.

Impact of Wood Moisture in Charcoal Production and Quality

Abstract The charcoal production when performed in woods with high moisture content negatively impacts the pyrolysis and causes an increase of greenhouse emissions. The aim of this study was to investigate the effects of moisture on the production and quality of charcoal for the pig iron industry. The slow pyrolysis of Eucalyptus sp. was carried out in four different wood moistures, 0, 20, 40 and 60% (dry base). The charcoal and gas yield decreased according to the increase of wood moisture. On the other hand, the bio-oil yield and charcoal friability increased along with the moisture content. The proximate analysis, bulk density and higher heating value of the charcoal were not influenced by the moisture content. The use of wood with moisture content below 20% in the production of charcoal is an alternative to improve productivity, contributing for the economic sustanainability of this sector.

Drying of Steaming Maple Timber in Drying Kilns, While Preserving the Color Acquired by the Wood Steaming Process

The paper presents a mode for drying steaming maple timber of thickness h = 38 mm from moisture W1 = 50 % to W2 = 10 %, while preserving the color of wood obtained by the steaming process. The drying process is divided into two parts. Evaporation of free water from wet wood at drying medium temperatures td = 35 - 40 °C and evaporation of water from wood below the hygroscopicity limit W ≤ 25 % at drying medium temperatures td = 70 - 80 °C. Total color difference ΔE* determined by the difference in values on the CIE L*a*b* color space coordinates dried by the proposed mode for steaming maple timber and the reference values ΔE* = 1.03. According to the categorization of wood color changes in thermal processes by work (Cividini et al. (2007), this change belongs to the category of small color changes. A negative aspect of this drying mode is the approx. 25 % increase in timber drying time.

Forecasting of Wood Moisture Content Based on Modified Ant Colony Algorithm to Optimize LSSVM Parameters

Wood moisture content (WMC) is an important technical index used in the wood drying process, and assessing its change accurately and reliably is the key to improving wood drying quality. In order to improve the accuracy and reliability of WMC forecasting, a modeling method is proposed that uses a modified ant colony algorithm (MACA) to optimize the least square support vector machine (LSSVM). The MACA combines the large-step size global search with the small-step size local fine search to obtain the optimal parameter combination automatically and are tested by five standard functions. Then the MACA-LSSVM model is proposed to predict the WMC and compared with back propagation neural network (BP-NN), LSSVM model, and ant colony optimization LSSVM (ACO-LSSVM). The drying data from a small-sized wood drying kiln independently developed by Northeast Forestry University are taken as the samples for analyzing. The results indicate that the root mean square relative error (RMSRE) obtained by the proposed method (MACA-LSSVM) is only 1.82%, which is 0.77%, 0.50%, and 0.20% less than those of the BP-NN, LSSVM, and ACO-LSSVM models. The forecasting time are 0.0070 s, 0.0030 s, and 0.0010 s shorter, respectively. The relative error (RE) and the mean absolute error (MAE) are also lower than those of the latter three models. The MACA-LSSVM shows the characteristics of low computational complexity, fast convergence speed, high prediction accuracy and strong generalization ability, and the prediction effect is ideal. This model can provide the theoretical support for intelligent control of the wood drying process.

Hygrothermal conditions in Cross Laminated Timber (CLT) dwellings

The use of CLT has been increasing the last decade, and a subsequently focus on documentation of the accompanying indoor climate and exposed wooden surfaces on human well-being. This study presents the results of a measurement campaign conducted over one year of a CLT apartment building in Grimstad, Norway. The apartment building consists of three floors with 35 apartments and comply with the Norwegian passive house standard and energy grade A. Measurements of the relative humidity (RH), indoor air temperature and wood moisture content (MC) were performed in the exposed CLT spruce panels in three apartments in two different floors. The results from the three apartments show a relatively small variation in the MC values regardless the residents behavior measured as RH variation through a complete year. Selected periods from a cold period (winter) and a warm period (summer) show the variation in relative humidity (RH) and moisture content in the CLT element. However, results from control measurements showed higher MC values. The gap between the measurements and methods are discussed.

Laminasi Kayu Sengon Sebagai Salah Satu Solusi Ketersediaan Kayu Untuk Bahan Bangunan

Abstracts. The supply of wood that is quite durable and of high quality has not been able to meet the needs of building construction at the present time, especially in the future. Sengon wood (Paraserianthes falcataria) is a fast-growing type of plant that has a large increase (volume of wood per hectare per year) which is around 28 - 48 m3 / ha / year. To fulfill various human objectives, the majority of Sengon wood can be collected from the age of 6 years. With the use of lamination technology, wood remnants can be utilized to be made into wooden blocks of various sizes and various shapes. Lamination can make the strength of Sengon wood higher than solid wood beams.The test is carried out by physical and mechanical tests as well as the Sengon wood laminated sliding block test. In testing physical and mechanical properties based on ISO 1975 regulations. Testing of physical properties of Sengon wood includes wood density test and moisture content test. Testing the mechanical properties of Sengon wood includes fiber parallel compressive strength test, fiber perpendicular compressive strength test, tensile strength test, shear strength test and flexural strength test. Testing of Sengon wood laminated sliding blocks to determine the strength of lamination has a variation of 30 MDGL, 40 MDGL and 50 MDGL slurry adhesives with 3 replications of each shear test.The average density of Sengon wood is 0.315 t / m3 and the average moisture content of Sengon wood is 13.539%. The average compressive strength of fibers is 26.85 MPa and the compressive strength of fibers is 9.62 MPa. The average tensile strength of Sengon wood is 61.48 MPa and the average shear strength of Sengon wood is 5.31 MPa. In testing the flexural strength of Sengon wood an average of 43.18 MPa. Testing of Sengon wood laminate sliding block for 30 / MDGL obtained an average of 0.05 kg / mm2. In the shear block 40 / MDGL obtained an average shear strength of 0.02 kg / mm2. For the 50 / MDGL laminate shear block an average shear strength of 0.08 kg / mm2 was obtained.

Doğu Ladini Odununun [Picea orientalis (L.) Link.] Rutubet Adsorpsiyonu Üzerine Bir Araştırma

Aim of study: The adsorption properties of the samples of full-dry Eastern Spruce (ES) [Picea orientalis (L). Link.] with 12.5 mm, 25 mm, 37.5 mm and 50 mm thick is to determine under the climate conditions with 42%, 65% and % 78 of relative humidity and at a constant temperature of 20 °C.
 Material and method: The wood samples used in this study were the Eastern Spruce woods which were obtained from Forestry Process Management in the city of Trabzon/Turkey. With regard to mathematical modeling used to determine the wood moisture content (MC), the equation constants in case of adsorption was determined. Experiments were conducted at three different equilibrium moisture content (EMC); 8%, 12% and 16%.
 Main results: Cross section had no crucial effect on the rate of accessibility to the final MC. However, EMC and thickness have been effective.
 Research highlights: In practice, since dried wood is kept at outside weather conditions for a certain time before operation, an increase can be observed in the wood MC. It is practically important that under the influence of climate conditions until its utilization, the tendency of water adsorption of wood is determined as a function of time.

Assessment of Preservative-Treated Wooden Poles Using Drilling-Resistance Measurements

An IML-Resi PD-400 drilling tool with two types of spade drill bits (IML System GmbH, Wiesloch, Germany) was used to evaluate the internal conditions of 3 m wooden poles made from Scots pine (Pinus sylvestris L.). Drilling tests were performed on poles that were industrially vacuum-pressure-impregnated with a copper-based preservative (Korasit KS-M) and untreated reference poles. Both types of poles were subject to 10.5 years of in-ground exposure. Wood moisture content (MC) was measured using a resistance-type moisture meter. MC varied between 15% and 60% in the radial and axial directions in both treated and untreated poles. A higher MC was detected in the underground, top, and outer (sapwood) parts of the poles. Typical drilling-resistance (DR) profiles of poles with internal defects were analyzed. Preservative treatment had a significant influence on wood durability in the underground part of the poles. Based on DR measurements, we found that untreated wood that was in contact with soil was severely degraded by insects and wood-destroying fungi. Conversely, treated wood generally showed no reduction in DR or feeding resistance (FR). DR profiling is a potential method for the in-situ or in vitro assessment and quality monitoring of preservative treatments and wood durability. The technological benefits of using drill bits with one major cutting edge, instead of standard drill bits with center-spiked tips and two major cutting edges, were not evident. A new graphical method was applied to present DR data and their spatial distribution in the poles. Future studies should focus on the impact of preservative treatments, thermal modification, and chemical modification on the DR and FR of wood. This may further elucidate the predictive value of DR and FR for wood properties.

WOOD DRYERS: A SUSTAINABLE ALTERNATIVE FOR INCREASED CHARCOAL PRODUCTION

The aim of the study was to evaluate the technical and economic viability of a wood dryer in the charcoal production. Drying was carried out for 72 hours using wood from Eucalyptus sp. in two classes of diameter. The average admission temperature of combustion gases in the dryer was 100-150ºC. It was determined the mass of water withdrawn by drying and estimated the amount of wood that would be consumed during the pyrolysis to remove the same amount of water, being this wood converted into charcoal mass. In the economic analysis were determined the indicators net present value, internal rate of return and discounted payback. The dryer presented technical feasibility, reducing wood moisture by 8% and, consequently, increasing the charcoal productivity by 3.3%, and economic viability, with good financial indicators for current market conditions, including a discounted payback of 6 years. In this way, the use of a wood dryer was presented as an efficient way to take advantage of an environmental liability of pyrolysis, which contributes to the increase of sustainability in the charcoal production.

Fine Particle Emissions from Sauna Stoves: Effects of Combustion Appliance and Fuel, and Implications for the Finnish Emission Inventory

Sauna Stoves (SS) are simple wood combustion appliances used mainly in Nordic countries. They generate emissions that have an impact on air quality and climate. In this study, a new measurement concept for comparing the operation, thermal efficiency, and real-life fine particle and gaseous emissions of SS was utilized. In addition, a novel, simple, and universal emission calculation procedure for the determination of nominal emission factors was developed for which the equations are presented for the first time. Fine particle and gaseous concentrations from 10 different types of SS were investigated. It was found that each SS model was an individual in relation to stove performance: stove heating time, air-to-fuel ratio, thermal efficiency, and emissions. Nine-fold differences in fine particle mass (PM1) concentrations, and about 90-fold differences in concentrations of polycyclic aromatic hydrocarbons (PAH) were found between the SS, when dry (11% moisture content) birch wood was used. By using moist (18%) wood, particle number and carbon monoxide concentrations increased, but interestingly, PM1, PAH, and black carbon (BC) concentrations clearly decreased, when comparing to dry wood. E.g., PAH concentrations were 5.5–9.6 times higher with dry wood than with moist wood. Between wood species, 2–3-fold maximum differences in the emissions were found, whereas about 1.5-fold differences were observed between bark-containing and debarked wood logs. On average, the emissions measured in this study were considerably lower than in previous studies and emission inventories. This suggests that overall the designs of sauna stoves available on the market have improved during the 2010s. The findings of this study were used to update the calculation scheme behind the inventories, causing the estimates for total PM emissions from SS in Finland to decrease. However, wood-fired sauna stoves are still estimated to be the highest individual emission source of fine particles and black carbon in Finland.