Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas
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...
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-11-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/25/22/5367 |
| _version_ | 1797547693754548224 |
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| author | Robert A. Franich Roger Meder Volker C. Behr |
| author_facet | Robert A. Franich Roger Meder Volker C. Behr |
| author_sort | Robert A. Franich |
| collection | DOAJ |
| description | 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 CO<sub>2</sub> 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. |
| first_indexed | 2024-03-10T14:47:44Z |
| format | Article |
| id | doaj.art-649a209a4c2744f79d1811d23d5d9b2b |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-03-10T14:47:44Z |
| publishDate | 2020-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Molecules |
| spelling | doaj.art-649a209a4c2744f79d1811d23d5d9b2b2023-11-20T21:13:00ZengMDPI AGMolecules1420-30492020-11-012522536710.3390/molecules25225367Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and GasRobert A. Franich0Roger Meder1Volker C. Behr2Chemipreneur Limited, Rotorua 3010, New ZealandMeder Consulting, Queensland QLD 4017, AustraliaExperimental Physics 5, University of Würzburg, 97074 Würzburg, GermanyConventional 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 CO<sub>2</sub> 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.https://www.mdpi.com/1420-3049/25/22/5367supercritical CO<sub>2</sub>phase-changesapwooddewateringphysical chemistrynuclear magnetic resonance spectroscopy |
| spellingShingle | Robert A. Franich Roger Meder Volker C. Behr Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas Molecules supercritical CO<sub>2</sub> phase-change sapwood dewatering physical chemistry nuclear magnetic resonance spectroscopy |
| title | Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas |
| title_full | Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas |
| title_fullStr | Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas |
| title_full_unstemmed | Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas |
| title_short | Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas |
| title_sort | dewatering green sapwood using carbon dioxide undergoing cyclical phase change between supercritical fluid and gas |
| topic | supercritical CO<sub>2</sub> phase-change sapwood dewatering physical chemistry nuclear magnetic resonance spectroscopy |
| url | https://www.mdpi.com/1420-3049/25/22/5367 |
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