Effect of supercritical CO2 dewatering followed by oven-drying of softwood and hardwood timbers

Dawson, Bernard S. W.; Pearson, Hamish

doi:10.1007/s00226-017-0895-8

Cited by 24 publications

(27 citation statements)

References 10 publications

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“…Permeability values for birch (Betula pubescens) and lime (Tilia vulgaris) are slightly smaller than those for spruce (Petty and Palin, 1983), which agrees with our findings here for beech compared with pine. Red beech timber is very susceptible to collapse during drying (Haslett and Kininmonth, 1986;Dawson and Pearson, 2017). Our observation of cell walls with greater porosity but smaller pores in this species generally supports the involvement of micropore size in cell wall collapse.…”

Section: Discussionsupporting

confidence: 71%

Comparison of Micropore Distribution in Cell Walls of Softwood and Hardwood Xylem

2018

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The porosity of wood cell walls is of interest for both understanding xylem functionality and from a wood materials perspective. The movement of water in xylem generally occurs through the macroporous networks formed in softwood by bordered pits and in hardwood by the intervessel pits and open conduits created by vessels and perforation plates. In some situations, such as cavitated xylem, water can only move through the micropores that occur in lignified tracheid and fiber cell walls; however, these micropore networks are poorly understood. Here, we used molecular microscopy analysis of radiata pine () and red beech () to determine the distribution of micropores in the secondary walls and middle lamellae of tracheids and fibers in relation to cell wall composition. Using two different types of probe, we identified a greater porosity of secondary cell walls and a reduced porosity of the middle lamella. Areas of reduced porosity were observed in the outer regions of the secondary cell wall of both tracheids and fibers that appear unrelated to lignification or the distribution of cellulose, mannan, and xylan. Hardwood fiber cell walls were less lignified than those of softwood tracheids and showed greater accessibility to porosity probes. Vessel cell walls were comparable to those of fibers in terms of both porosity and lignification. Lignification is probably the primary determinant of cell wall porosity in xylem. The highly lignified middle lamella, and lumen surface, act as a barrier to probe movement and, therefore, water movement in both softwood and hardwood.

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Section: Discussionsupporting

confidence: 71%

Comparison of Micropore Distribution in Cell Walls of Softwood and Hardwood Xylem

2018

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“…Eucalyptus nitens was chosen as a collapse-prone species known to have a medium lumen water expulsion efficiency (Dawson and Pearson 2017).…”

Section: Methodsmentioning

confidence: 99%

“…The supercritical CO 2 treatment of wooden specimens involves raising the CO 2 pressure around the specimens to 20 MPa and holding for an incubation period so that the CO 2 can diffuse into the specimen sap (water), while maintaining the treatment chamber at 50 °C. Depressurisation down to atmospheric pressure then results in conversion from supercritical fluid to gas phase CO 2 inside the specimen, which forces water out of specimen wood cells (Dawson et al 2015;Dawson and Pearson 2017). The pressurisationdepressurisation cycle is repeated multiple times to continue water expulsion from the specimens.…”

Section: Methodsmentioning

confidence: 99%

“…Drying methods for refractory Eucalyptus species often require a lengthy pre-drying phase to lessen the prevalence of collapse, washboard depression and internal checking. High pressure supercritical CO 2 treatment is a faster water removal technique from green timber that also reduces collapse (Dawson et al 2015;Franich et al 2010Franich et al , 2013 in a variety of softwoods and hardwoods (Dawson and Pearson 2017;Dawson et al 2015). The water removal efficiency of the supercritical CO 2 treatment varies according to species (Dawson and Pearson 2017).…”

Section: Introductionmentioning

confidence: 99%

“…High pressure supercritical CO 2 treatment is a faster water removal technique from green timber that also reduces collapse (Dawson et al 2015;Franich et al 2010Franich et al , 2013 in a variety of softwoods and hardwoods (Dawson and Pearson 2017;Dawson et al 2015). The water removal efficiency of the supercritical CO 2 treatment varies according to species (Dawson and Pearson 2017). To better understand the process, a computational fluid dynamics model has been developed to predict the behaviour of the supercritical CO 2 (Pearson et al 2019a, b).…”

Section: Introductionmentioning

confidence: 99%

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Effect of supercritical CO2 treatment and kiln drying on collapse in Eucalyptus nitens wood

et al. 2020

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Collapse-prone timbers such as species of Eucalyptus are poorly utilised due to low conversion rates that necessitate long pre-drying times. A supercritical CO 2 lumen water expulsion pre-treatment prior to kiln drying is proposed to bypass lengthy pre-drying. After drying (air, kiln or oven drying), shrinkage, collapse, washboard depression and checking of Eucalyptus nitens were determined using image analysis of 0.8 mm thick wafers and 5 mm thick biscuits. Lumen water expulsion-kiln drying reduced collapse by 75% and washboard depression by 71%, compared to drying from green. As water is removed from the water conductive tissue (vessels, rays, and fibre-tracheids) by lumen water expulsion, the water column is broken throughout the specimen, thereby disrupting the development of meniscus-induced water tension as subsequent drying occurs. Remaining water is proposed to reside in the non-water-conductive fibre tissue. If the process can be applied on large scale to Eucalyptus nitens, there is the opportunity for higher conversion rates to increase the commercial viability of solid wood products.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Dewatering fresh bamboo strips using supercritical carbon dioxide

Liu

Xie

et al. 2023

Eur. J. Wood Prod.

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Effect of supercritical CO2 dewatering followed by oven-drying of softwood and hardwood timbers

Cited by 24 publications

References 10 publications

Comparison of Micropore Distribution in Cell Walls of Softwood and Hardwood Xylem

Comparison of Micropore Distribution in Cell Walls of Softwood and Hardwood Xylem

Effect of supercritical CO2 treatment and kiln drying on collapse in Eucalyptus nitens wood

Dewatering fresh bamboo strips using supercritical carbon dioxide

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