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Schematic illustration of sorption isotherms in the hygroscopic and over-hygroscopic moisture ranges. Both absorption (right-pointing arrows) and desorption (left-pointing arrows) isotherms are illustrated. The right diagram is a zoom of the over-hygroscopic moisture range. In the hygroscopic range, water is predominantly found within the cell walls interacting with the wood polymers. In the over-hygroscopic range, the dominating sorption mechanism is capillary condensation in the macro-void structure.
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Wood-water interactions are central to the utilization of wood in our society since water affects many important characteristics of wood. This topic has been investigated for more than a century, but new knowledge continues to be generated as a result of improved experimental and computational methods. This review summarizes our current understandi...
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... content is also commonly expressed as a percentage of dry solid mass. The relationship between u eq and RH of the environment at a given temperature is known as the water vapor sorption isotherm, as illustrated in Figure 2. This relationship is fundamental to the understanding of wood-water interactions. ...
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... content is also commonly expressed as a percentage of dry solid mass. The relationship between ueq and RH of the environment at a given temperature is known as the water vapor sorption isotherm, as illustrated in Figure 2. This relationship is fundamental to the understanding of wood-water interactions. ...
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... relationship is fundamental to the understanding of wood-water interactions. Figure 2. Schematic illustration of sorption isotherms in the hygroscopic and over-hygroscopic moisture ranges. ...
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... division reflects differences in the dominant sorption mechanisms as well as the experimental techniques for moisture conditioning of samples. The hygroscopic range extends from 0% to about 95%-98% RH; the upper limit of this range may depend on the specific material and does not necessarily reflect an abrupt transition (Figure 2). In the hygroscopic range, water is primarily located within the wood cell walls, interacting with polymers by hydrogen bonding. ...
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... the hygroscopic range, water is primarily located within the wood cell walls, interacting with polymers by hydrogen bonding. The overhygroscopic range extends above about 95%-98% RH to full saturation, where the additional water is largely capillary water in the macro-void structure (Figure 2). ...
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... division reflects differences in the dominant sorption mechanisms as well as the experimental techniques for moisture conditioning of samples. The hygroscopic range extends from 0% to about 95%-98% RH; the upper limit of this range may depend on the specific material and does not necessarily reflect an abrupt transition (Figure 2). In the hygroscopic range, water is primarily located within the wood cell walls, interacting with polymers by hydrogen bonding. ...
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... the hygroscopic range, water is primarily located within the wood cell walls, interacting with polymers by hydrogen bonding. The over-hygroscopic range extends above about 95%-98% RH to full saturation, where the additional water is largely capillary water in the macro-void structure (Figure 2). ...
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... the moisture content increases, several phenomena give rise to an increase in water mobility: the polymer systems swell with an accompanying increase in porosity, the tortuosity of the environment for water movement decreases, the connectivity between water molecules increases, and the activation energy needed to break a hydrogen bond at a polymer sorption site decreases [203,204]. These phenomena in molecular dynamics simulations are consistent with measurements indicating that water softens the polymers in the wood cell wall [70] and that the strength of interaction between water and cell wall polymers decreases as moisture content increases [15,83,84,87,89] (Section 3.2). Furthermore, diffusion coefficients measured with NMR for absorbed water in cellulose fibers increase exponentially with moisture content [205]. ...
Citations
... Numerous equilibrium sorption models have been applied to water vapor sorption in cellulosic materials in the literature [19][20][21][22][23][24][25][26][27]. These models range from simple empirical equations to theoretical models based on an idealized physical system. ...
... We take a similar approach in this article and develop a sorption model using an empirical relationship between macroscopic thermodynamic properties and EMC. Although our approach does not aim to build a theoretical model from the molecular level or describe all the complex physicochemical phenomena involved in the sorption of water vapor by cellulosic materials [24,25], this type of model may be useful for accurately simulating heat and moisture transfer in high temperature applications such as steam drying or wildland fire. Prior literature on the thermodynamics of water vapor sorption in cellulosic materials is limited by reliance on the Clausius-Clapeyron equation [23,33,35,39,40]. ...
... It is not intended for modeling EMC in the overhygroscopic region because materials differ considerably in pore volume distribution. In materials such as wood the EMC increases dramatically at higher RH levels with capillary water [25,59]. The extrapolated values u f and X f given above should not be interpreted as being physically significant; they are not intended for comparison with any experimentally determined values. ...
Water vapor sorption is a fundamental property of cellulosic materials. Numerous theoretical and empirical models have been developed to describe the relationship between water activity, temperature, and equilibrium moisture content (EMC). However, a meaningful connection between model parameters and thermodynamic properties related to the sorption process is often lacking. In cases where models yield thermodynamic properties, such as through use of the Clausius-Clapeyron equation, these are limited to temperatures where the ideal gas equation is applicable. In this paper we advance a thermodynamic framework and formulate a new semi-empirical sorption model based on the differential Gibbs energy of sorption as a function of EMC and temperature, intended for high temperature applications such as steam drying or fire modeling. We refer to this as the Comprehensive Analytical Sorption Thermodynamic (CAST) model. It has six parameters, includes temperature explicitly, and is invertible. The CAST model includes analytical equations for the differential enthalpy of sorption, the differential entropy of sorption, and the integral heat of wetting. The model is evaluated using sorption data and calorimetric data over a range of temperatures from the wood science literature and compared with several existing models. Overall, the CAST model fits the experimental sorption and calorimetric data with higher accuracy than existing models.
... With the intention of the retention of any products in the wood, the solution of that product must be impregnated into the wood efficiently. Impregnation depends on the physical and anatomical characteristics of the wood and on the physical properties of the solution, such as the surface tension and viscosity [53]. In the present study, in which there is standardization in the wood samples, the differences in impregnation and mass retention are due to the intrinsic characteristics of the products used. ...
In civil construction, one of the primary challenges associated with wood application is its high flammability and low durability during fires. Although chemical treatment with fire-retardant properties exists, they are expensive and of non-renewable origin. Tannin, a wood extractive, being a phenolic compound, holds promise for enhancing the thermal properties of wood. This study aimed to assess the efficacy of tannin as a fire retardant and compare it with a commercial product, as well as comparing different application techniques for these products. Wood samples from the Simarouba amara Aubl. species were utilized. Tannin and a commercial flame retardant were applied via immersion, vacuum impregnation, brushing, and a treatment of tannin incorporated into water-based wood varnish. Alongside the burning test performance, assessments of the wood's physical properties, such as colorimetry, thermal stability, and mass retention, were conducted. The application of tannin altered the wood's color and reduced the spread of fire; its presence significantly reduced the flame duration and maintained the wood's structural integrity. However, tannin retention was lower compared to commercial flame retardant, leading to reduced fire retardancy. Among the methods tested, immersion proved to be the most effective in enhancing the wood's resistance to flame contact.
... The higher moisture content in the pellets produced in the T3 treatment is due to the greater mass of water used in the process (20%) and the shorter drying time (4 hours). Thus, adsorbed water has a high energy demand for its removal in the form of vapor, which requires high temperature and/or longer drying time (Thybring et al., 2022). Treatment T2, with the lowest water mass and longest drying time between treatments, presented lower moisture content in the black pellets. ...
Charcoal fines are co-products of the wood carbonization process, unwanted because they reduce the gravimetric yield of the main product, charcoal. It can be produced due to the carbonization process, during the storage and transport of charcoal. Pelletizing charcoal fines increases the energy density of this material, producing a homogeneous fuel with lower moisture content, enabling burning in equipment with high energy efficiency, in addition to desirable properties in energy products such as high fixed carbon content and low moisture content. This study evaluated the effect of moisture content and drying time on the production of black pellets from charcoal fines bound with rice starch (Oryza sativa) on the physicochemical and mechanical characteristics. Black pellets were produced using two proportions of water (10 or 20%) and a drying time of 4 or 6 hours. Black pellets were evaluated for their proximate analysis, elemental composition, moisture content, size, apparent density, calorific value and energy density. The addition of water did not affect the content of volatile matter, ash, and fixed carbon, while the treatment with addition of 20% water and four hours of drying showed a higher moisture content (3.34%). The addition of water allowed for better heat conduction and particle arrangement, producing pellets with a durability greater than 98%. The better arrangement promoted by the addition of 20% water also increased the density of the pellets, resulting in greater energy density. Black pellets can be considered an alternative for residential heating, with T3 treatment (20% - 4h) with a high energy density and better performance in terms of desirable properties for use and commercialization according to the standard EN 14961-6.
... Quality of black pellets of charcoal... Carvalho et al. 2024 The higher moisture content in the pellets produced in the T3 treatment is due to the greater mass of water used in the process (20%) and the shorter drying time (4 hours). Thus, adsorbed water has a high energy demand for its removal in the form of vapor, which requires high temperature and/or longer drying time (Thybring et al., 2022). Treatment T2, with the lowest water mass and longest drying time between treatments, presented lower moisture content in the black pellets. ...
Charcoal fines are co-products of the wood carbonization process, unwanted because they reduce the gravimetric yield of the main product, charcoal. It can be produced due to the carbonization process, during the storage and transport of charcoal. Pelletizing charcoal fines increases the energy density of this material, producing a homogeneous fuel with lower moisture content, enabling burning in equipment with high energy efficiency, in addition to desirable properties in energy products such as high fixed carbon content and low moisture content. This study evaluated the effect of moisture content and drying time on the production of black pellets from charcoal fines bound with rice starch (Oryza sativa) on the physicochemical and mechanical characteristics. Black pellets were produced using two proportions of water (10 or 20%) and a drying time of 4 or 6 hours. Black pellets were evaluated for their proximate analysis, elemental composition, moisture content, size, apparent density, calorific value and energy density. The addition of water did not affect the content of volatile matter, ash, and fixed carbon, while the treatment with addition of 20% water and four hours of drying showed a higher moisture content (3.34%). The addition of water allowed for better heat conduction and particle arrangement, producing pellets with a durability greater than 98%. The better arrangement promoted by the addition of 20% water also increased the density of the pellets, resulting in greater energy density. Black pellets can be considered an alternative for residential heating, with T3 treatment (20% - 4h) with a high energy density and better performance in terms of desirable properties for use and commercialization according to the standard EN 14961-6.
Keywords:
Residential heating; Bioenergy; Charcoal residue
... Additionally, via forming hydrogen bonds with hydroxyl (OH) groups, water molecules interact closely with the cellulose, hemicellulose, and lignin molecules that make up wood. Hemicellulose is the chemical element that can form a hydrogen bond with water the most quickly [10]. Hemicellulose has a more open and non-crystalline structure than cellulose, which makes it more hygroscopic and draws more water molecules. ...
This study investigated physical, chemical, and thermal properties of the branch’s mangrove wood of Bruguiera gymnorhiza during conversion into charcoal and charcoal briquette. Two types of the branches were wood only (WO) and wood with bark (WB). Physical property of moisture content (MC) dropped from 34.76% to 3.02% for WO and 33.71% to 6.46% for WB when the wood was converted into charcoal briquette. In chemical property, carbon dioxide increased up to more than 90% for both WO and WB samples when the branches wood experienced carbonization into charcoal. Thermal properties comprised of calorific value showed positive characteristics of the branches wood when they were converted into bioenergy such as charcoal and briquette charcoal. The calorific value (MJ/kg) increased from 16.33 to 29.57 and 28.08, respectively for WO and from 15.98 to 26.72 and 26.07, respectively for WB. All these values indicated that branches of mangrove wood originated from B. gymnorhiza were prospective to be developed as source of bioenergy, particularly in the form of charcoal and briquette charcoal.
... as possible. In fact, the interactions between water vapor and wood or wood-derived materials have been reviewed and reported for a long time (Engelund et al. 2013;Nguyen et al. 2021a;Thybring et al. 2022). The behavior, interactions, hygrothermal, and durability properties of wood and bio-sourced materials with water vapor have been reported (Promis et al. 2019(Promis et al. , 2018Rahim et al. 2017;Nguyen et al. 2018aNguyen et al. , 2017. ...
The mechanism of fluid and heat transmission within materials with complex porous structures has not yet been fully explored and understood using basic analytical techniques. Therefore, the lack of advanced equipment and techniques has left an important knowledge gap in explaining the complex mechanisms of fluid motion and heat transfer in complex porous structures. This review provides an overview of how image analysis and processing techniques allow insight into the complex and heterogeneous porous structure of materials and explains the mechanism of heat and mass transfer in these complex porous materials in 3D and 4D observation in different directions. Accordingly, it provides interesting results related to the evaluation of microporous properties of complex porous materials including porosity, distribution and size of pores, distribution and orientation of fibers, tortuosity and mechanism of cracking, and destruction of the porous materials under mechanical tests. It also explains the mechanism of liquid transport in porous materials through 3D/4D observation thanks to image processing techniques. Therefore, this review has completed some limited knowledge in microstructural analysis and helped to understand the physical phenomena of liquid transfer in complex porous materials that were not fully exploited by experimental or simulation work. The paper also provides useful data for physical model simulation of imbibition and drying porous materials.
... An ideal model for fragmentation and water absorption was established in Section 4.1.; however, it is known that the water absorption rate of wood specimens per unit of time is influenced by both the properties of the original wood material (wood is an anisotropic and heterogeneous natural material, and the water absorption performance of the sapwood is more robust than that of the wetwood) [39,40] and the degree of mechanical rolling cracking. To enhance the accuracy of the prediction model, the effect of material properties should be considered, since the impact of material properties is always considered static. ...
... An ideal model for fragmentation and water absorption was established in Section 4.1; however, it is known that the water absorption rate of wood specimens per unit of time is influenced by both the properties of the original wood material (wood is an anisotropic and heterogeneous natural material, and the water absorption performance of the sapwood is more robust than that of the wetwood) [39,40] and the degree of mechanical rolling cracking. To enhance the accuracy of the prediction model, the effect of material properties should be considered, since the impact of material properties is always considered static. ...
In this study, a machine learning-based method to assess and predict the cracking degree (CD) on wood fiber bundles (WFB) was developed, which is crucial for enhancing the quality control and refining the production process of wood scrimber (WS). By roller-cracking poplar wood one to three times, three distinct CD levels were established, and 361 WFB specimens were analyzed, using their water absorption rate (WAR) as the foundation for CD prediction. Through crack image analysis, four key quantitative parameters were identified—cracking density, coherence degree, crack count, and average width—and this study found through discriminant analysis that the discrimination accuracy on the CD levels by cracking density or coherence degree over 90%, emphasizing their significance in evaluation. Cluster analysis grouped the specimens into three clusters based on four key quantitative parameters, aligning with the CD levels. This study developed specialized prediction models for each CD level, integrating principal component analysis for dimensionality reduction with polynomial fitting, achieving mean squared error (MSE) of 0.0132, 0.0498, and 0.0204 for levels 1, 2, and 3, respectively. An integrated model, with an accuracy of 94.3% and predictions within a 20% error margin, was created, demonstrating the effectiveness of using surface crack image features to predict WAR of WFB. This research establishes a methodological framework for assessing CDs on WFB, contributing to enhancing WS product quality and helping to better understand wood cracking and water absorption mechanisms.
... Collisional quenching requires the quenching molecule (liquid water) to collide with the fluorophore, leading to energy transfer to the water. However, below fibre saturation, water is more and more firmly bound to the cell wall through H-bonding (Thybring et al. 2022), and the energetic states of both water and lignocellulose change (Guo et al. 2016). At low moisture levels, other mechanisms than energy transfer to water might prevail. ...
... Both is much lower than the measured excitation maximum of 385 nm in this study. 4. The excitation-dependent emission profile of lignocellulose is shown in Fig. 1a. 5. Through water uptake, hydrogen-bonds between cell wall composites in wood become weaker and some eventually break (Thybring et al. 2022), thus reducing the effective cluster size and clustering-triggered emission intensity. Although Zhang et al. (2020b) limited the term "size" (5) to generations of dendrimers, molecular weight of polymers, diameter of nanoparticles etc., we propose that the weakening of hydrogen bonds within the clusters has a comparable effect to size reduction. ...
The fluorescence behaviour of lignocellulose in Pinus sylvestris L. was studied under the influence of moisture. Fluorescence excitation-emission-matrices (EEMs) of the solid wood surfaces were recorded. Two emission peaks were identified, one attributed to lignocellulose, the other to pinosylvins. The two peaks were successfully modelled with PARAFAC2-deconvolution. Lignocellulose showed excitation-dependent emission. Its emission was quenched and blue-shifted by moisture, while pinosylvin showed none of these properties. The quenching efficiency was proportional to the moisture content (linear Stern–Volmer plot), a phenomenon first demonstrated for wood in this study. Potential mechanisms for the moisture quenching are discussed, with clustering-triggered emission best explaining most of the observed peculiarities. The strong influence of moisture on the fluorescence of pine wood suggests that carbohydrates, or interactions between carbohydrates and lignin, play an important role in lignocellulose fluorescence.
... Investigating the temperature dependence of sorption, SShimizu and Matubayasi (2021) expanded the classical isosteric theory of sorption and established a theoretical ground for using (1/T) as an input variable. The slope of the natural logarithm of water activity at a particular moisture content versus inverse absolute temperature is frequently used to calculate the isosteric heat of sorption, an indicator of the energy change associated with the sorption process (Igathinathane et al. 2005;Thybring et al. 2022). Therefore, incorporating the inverse absolute temperature into sorption isotherm models can enhance the models' adherence to thermodynamic principles (Yang et al. 2015). ...
... For instance, between 25 C and 100 C, the enthalpy of vaporization of purified water varies by 8%. It is essential to acknowledge that the Clausius-Clapeyron equation demands constant EMC values for water activity, frequently requiring interpolation between measured data points (Thybring et al. 2022). ...
The temperature dependency of the adsorption isotherm renders its significance as one of the primary input parameters in models dealing with moisture transport. The present study involved the determination of the adsorption isotherm of sixteen building materials from various categories, including cladding, building paper, wood, sheathing boards, and insulations. The measurements were conducted under nine climatic conditions, a combination of three temperatures (3°C (37.4°F), 21°C (69.8°F), 45°C (113°F)) and three relative humidity levels (50%, 70%, 90%). The study indicated that relative humidity increased the building materials' equilibrium moisture content (EMC). In opposition, an increase in temperature decreased the EMC of the tested materials. It was discovered that cellulose fibre and wood-based materials had a greater capacity to store moisture than others. Conversely, the minimum moisture content was observed in brick, Densglass gold gypsum, and EPS products. Furthermore, we used the ABC model as an adaptable mathematical equation for a novel nonlinear surface fitting of adsorption isotherms of tested materials to make optimal use of the experimental data and effectively analyze the simultaneous impact of all temperatures and relative humidities. Tested against the measured experimental data, we obtained the best R-squared values from the second-order polynomial Equation.
... Although the actual CELL and HEMI content of trees vary by species and genotype, most of the measured values fall in the range of 40% to 50% for CELL and 15-25% for HEMI for North American tree species (Pettersen, 1984;Ross & Anderson, 2021 Using 0.55 as the fraction of accessible hydroxyl groups results in an estimate of total accessible hydroxyl groups that is at the low end of the range (6-10 mmol g À1 ) suggested in a recent review (Thybring et al., 2022). We quantified the sensitivity to alternative fractions of accessible hydroxyl groups (0.45, 0.35) on the distribution of 2 H before CVD. ...
... Our method for calculating the adjusted isotope ratio, *R, maintains a nominal 1:1 equilibrium between exchangeable hydrogen in XW and CELL + HEMI and sets a limit at 100% WEE. However, the actual chemical dynamics, when the tissue MC is 5% or less, is likely more complex (Thybring et al., 2022). We believe that our approach is conservative and likely underestimates the actual Δδ 2 H. Using un- (Reijenga et al., 2013). ...
... It is possible that the higher average value of exchangeable hydroxyl groups obtained by using tritium studies results from the use of whole tissues, which would include HEMI. In general, HEMI has a much larger fraction of accessible hydroxyl groups (Thybring et al., 2022). The accessible deuterium -OH estimates are based on laboratory studies with CELL pulps. ...
Stable isotopes δ ¹⁸ O and δ ² H are used to infer vegetation water sources. In some studies, significant xylem water δ ² H offsets from potential source waters have been observed. The offsets appear to be more prevalent with cryogenic vacuum distillation (CVD) of plant water. Hypothesized mechanisms for these offsets include changes during plant water uptake and transport, and methodological problems. We propose that a large portion of the offsets are due to hydrogen isotope exchange between xylem water and non‐crystalline hydroxyl groups of wood cellulose and hemicellulose during CVD. We present a method for estimating the hypothesized isotopic exchange between wood tissues and water, which is the result of Rayleigh and equilibrium fractionation. To estimate the exchange, we use published wood properties for North American tree species and isotope chemical relationships as a function of moisture content, CVD temperature and water extraction efficiency. A simple model of exchange between xylem water and hydroxyl groups captures the range of observations in studies in which CVD and non‐CVD methods were compared. To evaluate the model, we compared observed δ ² H offsets (sw‐excess) values from two field datasets (90°C, n = 364, and 170°C, n = 43) to δ ² H offsets estimated with our chemical model. We found good agreement between observed and estimated δ ² H offsets for samples extracted at 90°C ( r ² = 0.69) but not for samples extracted at 170°C ( r ² = 0.20). The offset may be eliminated by increasing the extraction temperature to 229°C or by adding a standard sufficient to raise the moisture content to >150%. A correction can also be approximated by applying a theoretical calculation based on the extraction temperature, moisture content and water extraction efficiency.
