PERFORMANCE OF INDUSTRIAL SOLAR KILN FOR DRYING TIMBER

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PERFORMANCE OF INDUSTRIAL SOLAR KILN FOR DRYING
TIMBER

• M. N. Haque
• Forest Research, NZ
• T.A.G. Langrish
• Department of Chemical Engineering,
• University of Sydney

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Outline

• Background to this research
• Description of this solar kiln
• Materials and methods
• Actual measurements assessment of performance
• Comments on suitability in NZ
• Conclusions

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Solar kilns for drying timber
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Solar kilns for drying timber
Solar kiln at Boral Timbers Herons Creek site,
NSW, AUSTRALIA
Recent design of solar kiln by Solar Dryers
Australia, Bellingen, NSW
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Air-drying site
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Typical drying example
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Materials methods
INPUT
SOLAR KILN MODEL
OUTPUT
Timber MC, air T RH
Borals Solar Kiln
Ambient T
RH
Timber properties
Quality prediction
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Procedure for measuring MC

• Biscuit samples 20?250?43 mm, oven-dry test
• Kiln sample boards 300?250?43 mm
• estimated MC based on biscuit samples

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Results- run 1 (May-June)
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Results- run 2 (July-August)
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Results- run 3 (Sep-Oct)
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Results- run 4 (Nov-March)
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Results- run 5 (March-May)
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Results- summary
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Measured solar radiation
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Results- HEX status
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Some NZ facts

• About 2 million m3 timber dried each year (mainly
  radiata pine)
• Average 3 GJ/m3 energy requirements
• Total 6 PJ energy consumption
• 95 thermal, 5 electrical
• 60 thermal from wood residue
• Processing of alternative species is growing

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Solar radiation at Rotorua, NZ (NIWA, 2002)
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Initiatives in NZ

• Greenhouse companies
• Redpath www.greenhouse.co.nz
• Harford www.greenhouses.co.nz
• Do not have drying tech experience but an
  engineering company can be brought together

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Conclusions

• Solar energy, ambient T RH, kiln T RH and
  wood MC were measured.
• Average increases in kiln air T (compared with
  ambient) were
• 17.3?C (May-June)
• 13.8?C (July-August)
• 10?C (September-October)
• 8.2?C (November-March)
• 7.5?C (March-May)

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Conclusions (continued)

• Drying times were 3 to 4 months from initial (43
  to 62) to final MC (12 to 22).
• Overall solar kiln is considered as an acceptable
  alternative to air-drying method for pre-drying
  of hardwoods (e.g. blackbutt, Eucalyptus
  pilularis).
• So Australasian timber industry is showing an
  increasing interest in use of solar kilns.

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Acknowledgements

• Boral Timber Division
• Faculty of Engineering, The University of Sydney
  for financial assistance