Research on the effect of microwave pretreatment on moisture diffusion coefficient of wood

Li, Xianjun; Bi-guang, Zhang; Li, Wenjun; Li, Yanjun

doi:10.1007/s00226-005-0007-z

Cited by 18 publications

(13 citation statements)

References 3 publications

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“…The damage of pit membrane and pit torus due to steaming has also been reported by previous researchers (Nicholas and Thomas 1968;Jianxiong et al 1994;Zhang and Cai 2008). Although the contribution of pit pairs to water vapor diffusion is usually neglected (Li et al 2005;Kang et al 2008), our results revealed that the hydrolysis of pit toruses in Abies alba L. due to steaming at a high temperature (160°C) can influence the diffusion characteristics. Indeed, based on the results obtained here, it can be claimed that the effect of pit pairs torus hydrolsis in Abies alba L. on its diffusion coefficient is more pronounced compared to that of cell wall holocellulose hydrolysis.…”

Section: Effect Of Pre-steaming On the Diffusion Coefficientsupporting

confidence: 88%

“…In fact, how the wood porous structure is damaged due to the heat treatment determines the ease of fluid migration through the wood. For example, Li et al (2005) found that the microwave pretreatment was able to damage the structure of pit membrane in Masson pinewood, but could not effectively improve the diffusion coefficient. …”

Section: Effect Of Pre-steaming On the Diffusion Coefficientmentioning

confidence: 99%

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Effect of Pre-Steaming on Mass Transfer Properties of Fir Wood (Abies Alba L.); A Gymnosperm Species With Torus Margo Pit Membrane

Dashti¹,

Tarmian²,

Faezipour³

et al. 2012

BioResources

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In this research, the effect of pre-steaming on mass transfer properties, including air permeability and water vapor diffusivity of fir wood (Abies alba L.), a gymnosperm species with torus margo pit membrane, was evaluated. The pre-steaming was performed at temperatures of 120, 140, and 160°C for 1 hour under a pressure of 2-3 bars. Then, the presteamed specimens were conventionally dried at a constant temperature of 160°C and a relative humidity of 50% to the final moisture content of 10%. Subsequently, the mass transfer properties of the dried specimens were measured in longitudinal and radial directions. Overall, the presteaming was found to be an effective modification method to improve the mass transfer properties of Abies alba L. The improvement was more remarkable for the air permeability as well as through the radial direction. The specimens steamed at the temperature of 160°C had higher mass transfer rates than those steamed at the temperatures of 120 and 140°C. Results of chemical analyses, FT-IR spectroscopy, and SEM imaging provide some explanations for the effects of pre-steaming.

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Section: Effect Of Pre-steaming On the Diffusion Coefficientsupporting

confidence: 88%

Section: Effect Of Pre-steaming On the Diffusion Coefficientmentioning

confidence: 99%

Effect of Pre-Steaming on Mass Transfer Properties of Fir Wood (Abies Alba L.); A Gymnosperm Species With Torus Margo Pit Membrane

Dashti¹,

Tarmian²,

Faezipour³

et al. 2012

BioResources

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“…Parameters including MW intensity, moisture content (MC) of the treated lumbers, and processing time are prime factors influencing the efficiency of treatments. Also, the structural changes during MW treatment can lead to changes in wood properties, such as permeability, density, and strength (Seyfarth et al 2003;Li et al 2005;Harris et al 2008;Vinden et al 2011). However, a systematic investigation of how these parameters influence the properties of treated wood and the mechanisms of liquid permeability improvement of MW-treated wood is imperative.…”

Section: Introductionmentioning

confidence: 99%

Microwave Treatment for Enhancing the Liquid Permeability of Chinese Fir

He¹,

Lin²,

Fu³

et al. 2014

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A microwave (MW) treatment method was applied to Chinese fir wood to improve its liquid permeability. It was found that the optimum parameters for the MW treatment of Chinese fir to achieve an improved permeability without significantly affecting its mechanical properties were as follows: a MW intensity of 20 kW, moisture content (MC) ranging from 40% to 60%, and a processing time of 60 s. The microscopic structure of Chinese fir wood before and after MW treatment was examined using a scanning electron microscope (SEM), which revealed that micro-checks were formed at the intercellular layer of ray cells and longitudinal tracheids; pit membranes were destroyed; and damage to cell walls was also observed. Mercury intrusion porosimetry (MIP) test results showed that the pore diameter at pit opening range increased after MW treatment (peak value of control sample: 553.7 nm; peak value of MW-treated sample: 921.1 nm) and micropores were generated, which also contributed to the improved permeability of Chinese fir wood. Positive correlations between microstructural changes and liquid permeability were found.

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“…Microwave pretreatments have been used to reduce the number and depth checks and honeycomb in the conventional kiln drying of backsawn/flatsawn messmate stringybark (Eucalyptus obliqua) [99] and to increase the diffusion coefficient of hinoki (Chamaecyparis obtusa) timber up to 3 % [100]. A pre-treatment with dielectric heating at radio frequency (RF) on sub-alpine fir results in higher permeability and increased drying rates both above and below the fiber saturation point, 18-30 % and 21-55 %, respectively [101].…”

Section: Pre-treatment To Accelerate Dryingmentioning

confidence: 99%

A Decade of Improved Lumber Drying Technology

Bond

Espinoza

2016

Curr Forestry Rep

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In this paper, we comprehensively review the relevant literature published from 2005 to 2016, focused on lumber drying and provide a summary of where we feel future research will focus. Drying is a critical part of most wood products manufacturing process, and the methods used and proper control are key to achieving the appropriate production level, quality, and costs. While a combination of drying methods may be used, most lumber is dried in a kiln at some point in the process. The most common commercial kilns can be classified as conventional, high temperature, and vacuum; however, there continues to be some interest in solar and compression drying. While no new drying technologies have been proposed, work has continued on improving the existing methods. Control of the drying process varies with the type of kiln used, the species being dried and the temperatures used in the process; however, it usually involves some type of measurement of the moisture content of the wood being dried. The development of new methods for controlling the drying process focuses on new ways to measure moisture content or moisture content variation, temperature drop across the load, and drying stresses. While wood quality can be defined differently by its various users, for example, industrial or end users, certain aspects of quality remain constant across these groups, such as minimizing warp, checks, and splits, and discoloration, and maintaining or enhancing mechanical properties. New schedules have been proposed to increase drying rate and improve drying quality. Methods to reduce drying defects and improve its quality have focused mainly on mechanical restraint to prevent warp, better understanding of defect formation, and pre-treatments to speed up the drying process or reduce final moisture content variation. Finally, concerns regarding the environmental impacts of wood drying, most importantly the high energy demands and emissions, have increased in importance as concerns about sustainability and health issues become more mainstream.

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Research on the effect of microwave pretreatment on moisture diffusion coefficient of wood

Cited by 18 publications

References 3 publications

Effect of Pre-Steaming on Mass Transfer Properties of Fir Wood (Abies Alba L.); A Gymnosperm Species With Torus Margo Pit Membrane

Effect of Pre-Steaming on Mass Transfer Properties of Fir Wood (Abies Alba L.); A Gymnosperm Species With Torus Margo Pit Membrane

Microwave Treatment for Enhancing the Liquid Permeability of Chinese Fir

A Decade of Improved Lumber Drying Technology

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