Effect of specimen dimension and pre-heating temperature on supercritical CO2 dewatering of radiata pine sapwood
-
Bernard S.W. Dawson
,
Hamish Pearson
Abstract
Removing water from wood is a critical requirement for applications in building and construction and for chemical modifications. Normally, green radiata pine (Pinus radiata D. Don) timber, with a moisture content (MC) range at harvest between 150% and 200%, is kiln dried to below fiber saturation point (FSP) to 10–14% MC. In the present work, a physical-chemical-mechanical dewatering process is presented, which involves pressure cycling with supercritical CO2 to remove water to near the FSP. When the CO2 was cycled from ∼4 MPa into the supercritical state, at pressures up to 20 MPa, specimens of cross-sectional dimensions of up to 52 mm were successfully dewatered from a MC of 174%, typical of the green state, to approximately 39% in seven cycles. The specimens with the smallest cross-sectional dimensions dewatered more slowly than the larger specimens. Preheating the green wood before loading it into the dewatering vessel increased the rate of dewatering. The final MCs were similar in all experiments and were independent of specimen dimension (15–52 mm) or preheating temperature between 40°C and 60°C. Pressure-temperature phase diagrams show that it is necessary to compress the CO2 to the supercritical state for efficient dewatering. Diffusion rates and solubility of CO2 in sap were important, but channel opening within specimens was proposed to be a critical factor in the dewatering process. The reason why pressure-based experiments remove water from wood to an MC greater than the established FSP of 30% is not yet clear.
Acknowledgments
The authors acknowledge funding provided by the New Zealand Ministry of Business, Innovation & Enterprise (MBIE, formerly the Foundation for Research Science and Technology) for the Wood Products for the Future (C04X0207) and Elite Wood Products (C04X0702) programs. Elspeth MacRae, Scion, is thanked for advice during editing.
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©2015 by De Gruyter
Artikel in diesem Heft
- Frontmatter
- Review Articles
- A large-scale test set-up for measuring VOC emissions from wood products under laboratory conditions in simulated real rooms
- Industrial waste water for biotechnological reduction of aldehyde emissions from wood products
- Original Articles
- Light scattering characterization of lignosulfonate structure in saline solutions
- Differences in wood properties of Picea abies L. Karst. in relation to site of provenance and population genetics
- Rapid determination of biomass and polypropylene in three types of wood plastic composites (WPCs) using FTIR spectroscopy and partial least squares regression (PLSR)
- Thermal modification of Southern pine combined with wax emulsion preimpregnation: effect on hydrophobicity and dimensional stability
- Mixed-mode fracture toughness of bond lines of PRF and PUR adhesives in European beech wood
- Effect of specimen dimension and pre-heating temperature on supercritical CO2 dewatering of radiata pine sapwood
- Sound absorption of wood-based materials
- Threshold for ion movements in wood cell walls below fiber saturation observed by X-ray fluorescence microscopy (XFM)
- Oxygen plasma treatment of bamboo fibers (BF) and its effects on the static and dynamic mechanical properties of BF-unsaturated polyester composites
- A combined view on composition, molecular structure, and micromechanics of fungal degraded softwood
- Morphological changes induced in wood samples by aqueous NaOH treatment and their effects on the conversion of cellulose I to cellulose II
- Young’s modulus and shear modulus of solid wood measured by the flexural vibration test of specimens with large height/length ratios
- Effects of cell wall ultrastructure on the transverse shrinkage anisotropy of Scots pine wood
- Short Note
- Reacted copper(II) concentrations in earlywood and latewood of micronized copper-treated Canadian softwood species
Artikel in diesem Heft
- Frontmatter
- Review Articles
- A large-scale test set-up for measuring VOC emissions from wood products under laboratory conditions in simulated real rooms
- Industrial waste water for biotechnological reduction of aldehyde emissions from wood products
- Original Articles
- Light scattering characterization of lignosulfonate structure in saline solutions
- Differences in wood properties of Picea abies L. Karst. in relation to site of provenance and population genetics
- Rapid determination of biomass and polypropylene in three types of wood plastic composites (WPCs) using FTIR spectroscopy and partial least squares regression (PLSR)
- Thermal modification of Southern pine combined with wax emulsion preimpregnation: effect on hydrophobicity and dimensional stability
- Mixed-mode fracture toughness of bond lines of PRF and PUR adhesives in European beech wood
- Effect of specimen dimension and pre-heating temperature on supercritical CO2 dewatering of radiata pine sapwood
- Sound absorption of wood-based materials
- Threshold for ion movements in wood cell walls below fiber saturation observed by X-ray fluorescence microscopy (XFM)
- Oxygen plasma treatment of bamboo fibers (BF) and its effects on the static and dynamic mechanical properties of BF-unsaturated polyester composites
- A combined view on composition, molecular structure, and micromechanics of fungal degraded softwood
- Morphological changes induced in wood samples by aqueous NaOH treatment and their effects on the conversion of cellulose I to cellulose II
- Young’s modulus and shear modulus of solid wood measured by the flexural vibration test of specimens with large height/length ratios
- Effects of cell wall ultrastructure on the transverse shrinkage anisotropy of Scots pine wood
- Short Note
- Reacted copper(II) concentrations in earlywood and latewood of micronized copper-treated Canadian softwood species
