Dewatering green sapwood using carbon dioxide cycled between supercritical fluid and gas phase

Franich, Robert A.; Gallagher, Suzanne; Kroese, Hank W.

doi:10.1016/j.supflu.2014.02.019

Cited by 27 publications

(34 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Many scholars also use special drying methods to dry eucalypti, such as vacuum drying, microwave drying, freeze-drying, and solar drying [5][6][7][8]. Compared with the mentioned above drying methods, supercritical CO 2 drying (SCD) has the advantages of fast drying rate, environmental protection, and simple operation [9]. ScCO 2 is a fluid that exceeds the critical pressure of CO 2 (7.38 MPa) and the critical temperature (31.1 • C).…”

Section: Introductionmentioning

confidence: 99%

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

et al. 2020

View full text Add to dashboard Cite

Supercritical CO2 (ScCO2) is a drying medium with excellent solubility and mass transfer efficiency. Supercritical CO2 drying (SCD) can remove the water of wood rapidly and prevent a change of microstructure caused by capillary tension in the drying process. In this study, Eucalyptus urophylla × E. grandis specimens with lengths of 50 and 100 mm were dried with ScCO2. Conventional kiln drying (CKD) and oven-drying (OD) were used as control. After 1 h, the drying rate, shrinkage, moisture distribution, drying stress were measured to explore the influence of drying methods and specimen length for drying characteristics during the early drying stage. The results showed that compared with CKD and OD, water removal was the fastest under SCD, and the drying rate was nine times of CKD and one time of OD. The shrinkage of SCD was the lowest among the three drying methods. Moisture distribution of SCD and OD was uneven. The drying stress of SCD was relatively high, the drying stress index of it was almost five times of CKD and three times of OD. Regardless of the drying method, shorter specimens had a shorter drying period but greater drying defects than the long specimens.

show abstract

Section: Introductionmentioning

confidence: 99%

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Dewatering with supercritical CO 2 has potential to preserve the porosity of cell walls similar to that in the green state which potentially offers advantages for infiltration with wood modification reagents (Franich et al ., ). Our results suggested that although accessibility of cell wall pores to nitrophenyl‐substituted carbohydrates was broadly similar in dewatered and kiln dried wood, some differences were highlighted close to the exclusion point.…”

Section: Discussionmentioning

confidence: 97%

“…Radiata pine sapwood specimens (100 × 50 × 600 mm 3 ) free of compression wood, were sampled from a single piece of green lumber and were prepared by either dewatering with supercritical CO 2 (Dawson et al . ; Franich et al ., ) or by conventional kiln drying. Kiln drying was carried out using a 90°C schedule with a 60°C wet‐bulb temperature.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Detection of wood cell wall porosity using small carbohydrate molecules and confocal fluorescence microscopy

Donaldson

Kroese

Hill

et al. 2015

Journal of Microscopy

View full text Add to dashboard Cite

A novel approach to nanoscale detection of cell wall porosity using confocal fluorescence microscopy is described. Infiltration of cell walls with a range of nitrophenyl-substituted carbohydrates of different molecular weights was assessed by measuring changes in the intensity of lignin fluorescence, in response to the quenching effect of the 4-nitrophenyl group. The following carbohydrates were used in order of increasing molecular weight; 4-nitrophenyl β-D-glucopyrano-side (monosaccharide), 4-nitrophenyl β-D-lactopyranoside (disaccharide), 2-chloro-4-nitrophenyl β-D-maltotrioside (trisaccharide), and 4-nitrophenyl α-D-maltopentaoside (pentasaccharide). This technique was used to compare cell wall porosity in wood which had been dewatered to 40% moisture content using supercritical CO2, where cell walls remain fully hydrated, with kiln dried wood equilibrated to 12% moisture content. Infiltration of cell walls as measured by fluorescence quenching, was found to decrease with increasing molecular weight, with the pentasaccharide being significantly excluded compared to the monosaccharide. Porosity experiments were performed on blocks and sections to assess differences in cell wall accessibility. Dewatered and kiln dried wood infiltrated as blocks showed similar results, but greater infiltration was achieved by using sections, indicating that not all pores were easily accessible by infiltration from the lumen surface. In wood blocks infiltrated with 4-nitrophenyl α-D-maltopentaoside, quenching of the secondary wall was quite variable, especially in kiln dried wood, indicating limited connectivity of pores accessible from the lumen surface.

show abstract

“…delivery tank, a high-pressure pump, and a water bath at the set-point temperature for the experiments [19,20]. The result of testing the pressure variable vs. the maximum dewatering rate is shown in Figure 1b, which showed a good linear relationship between the dewatering rate and maximum applied supercritical carbon dioxide pressure.…”

Section: Laboratory Experiments To Study Dewatering Of Radiata Pine Smentioning

confidence: 94%

Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas

Franich

Meder²,

Behr

2020

Molecules

Self Cite

View full text Add to dashboard Cite

Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO2 volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.

show abstract

Dewatering green sapwood using carbon dioxide cycled between supercritical fluid and gas phase

Cited by 27 publications

References 15 publications

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

Drying Characteristics of Eucalyptus urophylla × E. grandis with Supercritical CO2

Detection of wood cell wall porosity using small carbohydrate molecules and confocal fluorescence microscopy

Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas

Contact Info

Product

Resources

About