1994 Fiscal Year Final Research Report Summary
A Study on Preservation Treatment of Waterlogged Wood by Supercritical Drying
| Project/Area Number |
05835018
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
文化財科学
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| Research Institution | Nara National College of technology |
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Principal Investigator |
KAWAGOE Mikio Nara National College of Technology, Department of Chemical Engineering, Professor, 科学工学科, 教授 (90043489)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Conservation Science / Waterlogged Wood / Supercritical Drying |
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| Research Abstract |
In the present study, application of supercritical drying to preservation of waterlogged wood and PEG impregnation method were investigated from the view poit of chemical engineering.
PEG impregnation method : We have already analyzed the impregnation with PEG based on the diffusion model and found that the processing time can be predicted through the model. In this study, we found the effects of wood species, wood structure, temperature, and PEG concentration on the impregnation rate. Further, we investigated the shrinkage of woods after drying and found that the volumetric shrinkage is lower than 5% if the concentration of PEG is larger than 74% in mass fraction.
Supercritical drying : Carbon dioxide was used as the supercritical fluid. Since the mutual solubility in water-carbon dioxide system is small, water in the wood was replaced by ethanol and then the ethanol was replaced by isoamyl acetate. In this work, penetration rates of ethanol and isoamyl acetate were measured and analyze
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d based on the diffusion model to estimate effective diffusion coefficients. The effective diffusion coefficient was 44% of the molecular diffusion coefficient for ethanol-water system. For isoamylacetate-ethanol system the effective diffusion coefficient was about the same as that for the ethanol-water system. Consequently, the effective diffusion coefficients for the both systems were found to be 0.3 cm^2/day at 25ﾟC,regardless of wood species. The molecular diffusion coefficient of isoamylacetate in supercritical carbon dioxide was predicted to be 11.5 cm^2/day. In this case, the effective diffusion coefficient was taken to be 5.06 cm^2/day which is 44% of the molecular diffusion coefficient, as in the case of ethanol-water system. Predicting the processing times for both of the PEG impregnation and supercritical drying methods, the time required for the supercritical drying method was found to be a quarter of that for the PEG impregnation method. Finally, the shrinkage of wood after drying was measured. The volumetric shrinkage after supercritical drying was less than 20%, which is 7% in length assuming isotropic shrinkage of wood. Less
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