A novel software-based tool to verify and predict heat treatment times for packaging wood in compliance with ISPM 15

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A novel software-based tool to verify and predict
heat treatment times for packaging wood in
compliance with ISPM 15

Hugh Evans and Christine Tilbury Forest
Research Emily Ho, Jenni Ferrans and Sajid
Rafique BHR Group Limited
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Objective

• To develop a software tool to optimise the
  operation of industrial heating chambers to
  comply with ISPM 15
• Wood packaging material should be heated in
  accordance with a specific time-temperature
  schedule that achieves a minimum wood core
  temperature of 56oC for a minimum of 30 minutes
• with
• confidence
• minimum energy cost
• minimum operational time

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Heating Chamber Calibration

• specific to timber species, loading and seasonal
  ambient temperatures
• Significant air temperature variations within the
  chamber
• Significant timber temperature variations within
  the chamber

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Current Methods of Verifying Compliance with ISPM
15

• precise duplication of conditions
• vary with time of year, wood moisture, etc.

• use of thermocouple probes in one or more pieces
  of wood
• Probe(s) require accurate drilling to place the
  tip precisely in the core of a piece of wood
• Probe(s) tend to be on the exposed sides of edge
  pieces these receive more heat than pieces in
  the centre of stacked wood

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Limitations of Current Methods of Verifying
Compliance with ISPM 15

• Due to uncertainty, the operators tend to be
  over-cautious and to use longer heat treatment
  times as a safety margin

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The Role of the Software

• Software predicts heating time from basic chamber
  parameters including wet bulb temperatures
• Can be used to verify, complement or replace
  probe measurements
• Useable by chamber operators to
• verify or predict heat-treatment times
• optimise heat-treatment times to save energy
• optimise chamber throughput to save time

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Future Potential Developments

• Use in real time control of heating chamber
  operation
• Installation of CFR 21 part 11capability
  allowing
• Secure time stamped encrypted and inviolable data
  storage
• Electronic storage and transmission of individual
  chamber performance
• Remote interrogation by authorities of production
  rates
• Assignment of unique batch bar code allowing
  traceability of timber during transit

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Thermal Diffusion Model into Wood

• The core ELASTEQ model uses verified complex
  algorithms derived during 12 years development
  and use in other industries
• 2-dimensional time-dependent model, based
  primarily on Ficks 2nd law of diffusion
• Novel six-noded quadratic triangular elements
• Predicts 1-dimensional or 2 dimensional heat
  penetration from the outside to the centre of the
  wood

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The Model in Practice

• Software uses surface temperature and diffusivity
  of the wood as the driving parameters for
  modelling core temperature
• Wet bulb temperature
• Good indicator of surface temp of wet wood
• Mildly conservative indicator of surface temp of
  dry wood
• The wet bulb temperature is used as a measure of
  wood surface temp (with corrections for wood with
  low moisture content)
• Diffusivity depends on wood density and moisture
  content

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Core Temperature - Wet Pine

• Computed temperature is a good average estimate
  of wet pine (39 -90 moisture content) based on
  wet bulb temperature

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Core Temperature - Dry Pine

• Computed temperature is a conservative estimate
  of dry pine (12 -17 moisture content) based on
  wet bulb temperature

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Core Temperature - Wet Oak

• Computed temperature is a good estimate of wet
  oak (54 -65 moisture content) based on wet bulb
  temperature

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Data Input
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Certification
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Certification
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Development and Practical Implementation

• Initial use by
• chamber operators to check and predict heating
  times
• quarantine staff to check and verify heating
  times
• First commercial version will be launched after
• Beta testing of the software by potential end
  users
• Final verification in commercial situations
• Register now for a beta version
• Contact enquiries _at_ timbertherm.com
• www.timbertherm.com

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The Future

• A stand-alone certification tool, employing data
  from each HT run
• Network integration and encryption for remote
  interrogation and international
  traceability.This requires endorsement/approval
  by RPPOs and/or IPPC
• Next steps to address this goal
• discussion with RPPOs and IPPC
• customise to individual RPPO requirements and
  local tree species

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Thank you for your attention
Hugh Evans and Christine Tilbury Forest Research
hugh.evans _at_ forestry.gsi.gov.uk Emily Ho, Jenni
Ferrans and Sajid Rafique BHR Group Limited eho
_at_ bhrgroup.co.uk