EP0759137B1 - Method for processing wood at elevated temperatures - Google Patents

Method for processing wood at elevated temperatures Download PDF

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Publication number
EP0759137B1
EP0759137B1 EP95918005A EP95918005A EP0759137B1 EP 0759137 B1 EP0759137 B1 EP 0759137B1 EP 95918005 A EP95918005 A EP 95918005A EP 95918005 A EP95918005 A EP 95918005A EP 0759137 B1 EP0759137 B1 EP 0759137B1
Authority
EP
European Patent Office
Prior art keywords
wood
temperature
internal
difference
oven
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP95918005A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0759137A1 (en
Inventor
Pertti Viitaniemi
Alpo Ranta-Maunus
Saila JÄMSÄ
Pentti Ek
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Valtion Teknillinen Tutkimuskeskus
Original Assignee
Valtion Teknillinen Tutkimuskeskus
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from FI942210A external-priority patent/FI103834B1/fi
Priority claimed from FI942209A external-priority patent/FI104286B/fi
Application filed by Valtion Teknillinen Tutkimuskeskus filed Critical Valtion Teknillinen Tutkimuskeskus
Publication of EP0759137A1 publication Critical patent/EP0759137A1/en
Application granted granted Critical
Publication of EP0759137B1 publication Critical patent/EP0759137B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2210/00—Drying processes and machines for solid objects characterised by the specific requirements of the drying good
    • F26B2210/16—Wood, e.g. lumber, timber

Definitions

  • the present invention relates to a method according to the preamble of Claim 1 for processing wood at an elevated temperature.
  • Wood is processed at elevated temperatures in connection with, e.g., seasoning, thermal modification, and different manufacturing processes in general. Wood expands when heated.
  • thermal expansion is a small-scale phenomenon, and accordingly, it has not been taken into account in connection with thermal treatments.
  • only longitudinal wood expansion occurs on a small scale; cross-grain expansion even exceeds that of aluminium.
  • Significant thermal expansion in the cross-grain direction of wood easily gives rise to internal cracks unless taken into consideration in developing different types of processes.
  • the invention is based on the principle that, during processes where wood is kept at an elevated temperature, the temperatures of the wood core and the outer surface of the wood, respectively, are continuously determined, and the difference between the two temperatures is kept reasonably small, this too occurring on a continuous basis. These measures are taken both during the heating step, whereby the temperature of the wood is raised for the purpose of, e.g., seasoning, and the cooling step, whereby the wood is cooled back to its basic temperature.
  • the temperature difference is preferably about 30 °C at the most. Surprisingly, it has been noted that this concept can be used to even totally prevent the generation of internal cracks in the wood material.
  • the method according to the invention is mainly characterized by what is stated in the characterizing part of Claim 1.
  • the term "internal temperature” of wood is used to denote the temperature of wood at some distance from the outer surfaces of the wood. Depending on the shape of the piece of wood, the “internal temperature” is typically measured at a depth of at least about 2 to 5 cm.
  • the “external temperature” is the temperature measured at or slightly below the wood surface. Thus, in many cases the “external temperature” essentially corresponds to the ambient temperature, for instance the temperature in a drying oven.
  • the arrangement according to the invention can be carried out in, for instance, a drying oven provided with adjustable temperature and means for vapour discharge.
  • the temperature is gradually raised such that the temperature difference between the surface and the inner part of the wood is not allowed to exceed 30 °C.
  • the temperature difference is advantageously kept constant at a value between 10 and 30 °C.
  • the temperature difference is kept constant with a margin of at least about 5 °C depending on the thermostatic controllers used, whereby the external temperature is altered along with the rising internal temperature.
  • the concept according to the invention can be implemented by fitting a test piece with at least two sensors, one sensor measuring the internal temperature and the other sensor the surface temperature of the wood. When seasoning larger amounts of timber, it is advisable to provide several test pieces with sensors. In industrial-scale arrangements, the measurement results are used as basis for devising a suitable heating-up program for each type of wood, thereby observing the effect of the initial moisture content on the process.
  • the actual thermal treatment according to the invention is not initiated until the moisture content of the wood core has been reduced to a value below 30 %, advantageously below 10 %, in some cases below the above-mentioned limit at 5 %.
  • a piece of wood at room or factory temperature is inserted into a drying oven at a temperature of about 110 to 140 °C for the purpose of removing the main part of the water.
  • the ambient temperature that is, for instance, the temperature of the drying oven is subjected to a gradual increase while the difference between the internal and external temperatures of the wood is kept constant at a value below approximately 30 °C.
  • the concept according to the invention is applicable in particular in the context of hot drying and thermal processing of wood.
  • wood is dried until it exhibits a moisture content of, e.g., below 15 %, in some cases advantageously below 10 %.
  • a solution is achieved for rapidly seasoning wood.
  • An advantageous embodiment of the present invention can be implemented to remove the problems related to conventional drying techniques.
  • the invention is based on the notion that, apart from joiner timber, colour changes and resin discharges are acceptable in most practical wood applications, for instance when wood is used as construction material. Even in these applications, however, is is necessary to prevent the generation of internal cracks in the wood.
  • the seasoning method is based on the combination of the following three steps:
  • the oven temperature is advantageously set at a temperature between 100 and 150 °C, preferably in the range 100 to 130 °C. The heating is continued until the moisture content of the wood has been reduced to a value below at least 30 %.
  • step b the heating is discontinued when the wood exhibits a low enough moisture content in view of the intended use.
  • a moisture content of about 1 to 20 % is aimed at, preferably below 15 % and typically between about 10 and 15 %.
  • the temperatures inside the wood and at the outer surface of the wood can be continuously determined by means of, e.g., sensors fitted on the piece of wood, whereby the difference between said temperatures can be continuously kept moderately small on the basis of the measurement results.
  • the temperature can be raised to a value exceeding 130 °C, even exceeding 150 °C, whereby the time needed for the evening out of the wood temperature can be reduced, as the drying of the core part of wood is more effective at a higher temperature, thus reducing the differences in moisture content between the core and the surface.
  • the difference between the temperatures is monitored both during the heating step b, whereby the temperature of the wood is raised to dry the wood, and the cooling step (step c) during which the wood is cooled back to its basic temperature.
  • the temperature difference is advantageously kept at a constant value which is approximately 30 °C at the most, preferably about 10 to 30 °C. Too small a difference in temperature will prolong the seasoning process, whereas a great difference will increase the risk of internal crack generation. It has been found that the solution disclosed herein (i.e., temperature difference ⁇ 30 °C) can be implemented to even totally prevent the formation of cracks in the wood.
  • Step c comprises reducing the oven temperature until the internal temperature of the wood has reached a value below 100 °C. As stated above, it is of advantage to keep the difference between the inner and outer temperatures of the wood smaller than 30 °C even during the cooling step in order to prevent the formation of internal splits.
  • water vapour is introduced into the oven, and the so called wet bulb temperature is kept at about 80 to 120 °C, preferably about 100 °C, using this vapour.
  • the same water vapour introduction is applicable even at other points in the inventive method.
  • the present invention offers considerable benefits.
  • the invention can be used to accelerate normal seasoning, to control special seasoning processes at temperatures exceeding 100 °C, and to develop compression seasoning applications.
  • the formation of internal splits in the wood subjected to treatment can in practice be totally prevented during seasoning and heat treating.
  • test pieces exhibited a final moisture content of below 5 %.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Microbiology (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical And Physical Treatments For Wood And The Like (AREA)
  • Drying Of Solid Materials (AREA)
EP95918005A 1994-05-11 1995-05-11 Method for processing wood at elevated temperatures Expired - Lifetime EP0759137B1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
FI942210 1994-05-11
FI942210A FI103834B1 (fi) 1994-05-11 1994-05-11 Menetelmä puun kuivaamiseksi
FI942209 1994-05-11
FI942209A FI104286B (fi) 1994-05-11 1994-05-11 Menetelmä puun sisähalkeamisen estämiseksi
PCT/FI1995/000252 WO1995031680A1 (en) 1994-05-11 1995-05-11 Method for processing wood at elevated temperatures

Publications (2)

Publication Number Publication Date
EP0759137A1 EP0759137A1 (en) 1997-02-26
EP0759137B1 true EP0759137B1 (en) 1998-02-04

Family

ID=26159728

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95918005A Expired - Lifetime EP0759137B1 (en) 1994-05-11 1995-05-11 Method for processing wood at elevated temperatures

Country Status (6)

Country Link
EP (1) EP0759137B1 (da)
AT (1) ATE163084T1 (da)
AU (1) AU2410695A (da)
DE (1) DE69501588T2 (da)
DK (1) DK0759137T3 (da)
WO (1) WO1995031680A1 (da)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT410069B (de) * 2000-11-02 2003-01-27 Muehlboeck Kurt Verfahren zur hochtemperaturbehandlung von holz
DE102009047137A1 (de) 2009-11-25 2011-05-26 Institut Für Holztechnologie Dresden Gemeinnützige Gmbh Verfahren zur thermischen Modifizierung oder Vergütung von Holz und Holzprodukten
DE102011104025A1 (de) 2010-06-11 2011-12-15 Technische Universität Dresden Verfahren zur Modifizierung von Holz oder Holzwerkstoffen sowie chemisch und thermisch modifiziertes Holz
DE102015013450A1 (de) 2015-10-16 2016-04-14 Daimler Ag Verfahren zum Herstellen eines Holzzierteils

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI108880B (fi) * 1997-12-09 2002-04-15 Stellac Oy Menetelmä puutavaran lämpökäsittelemiseksi
NL1022548C2 (nl) * 2003-01-31 2004-08-03 Plato Internat Technology B V Werkwijze voor het veredelen van houtdelen.
FI118139B (fi) * 2005-02-22 2007-07-13 Valtion Teknillinen Menetelmä massiivipuuta käsittävän puukappaleen käsittelemiseksi
DE102007005527A1 (de) 2007-02-03 2008-08-07 Alzchem Trostberg Gmbh Verfahren zur Behandlung von Holzteilen
DE102007011703A1 (de) * 2007-03-08 2008-09-11 Sägewerk Hagensieker GmbH Verfahren zur Herstellung von Holzprofilen
FR2914734B1 (fr) * 2007-04-05 2010-06-11 Innovation Technologique Pour Procede pour le sechage de bois et dispositif pour sa mise en oeuvre
EP2196295A1 (de) 2008-12-04 2010-06-16 Fachhochschule Eberswalde Holz sowie Verfahren und Vorrichtungen zu dessen Herstellung
DE102009031639A1 (de) 2009-07-03 2011-01-05 Herbert Hagensieker Sägewerk GmbH Brettschichtholz
CN106524668A (zh) * 2016-10-31 2017-03-22 大亚(江苏)地板有限公司 地板用欧橡木材的干燥方法
CN106369936A (zh) * 2016-10-31 2017-02-01 大亚(江苏)地板有限公司 地板用乌金木的干燥方法

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE92391T1 (de) * 1989-12-13 1993-08-15 Rotberg Hans Werner Von Verfahren und vorrichtung zur schaedlingsvernichtung insbesondere bei der konservierung von objekten.

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT410069B (de) * 2000-11-02 2003-01-27 Muehlboeck Kurt Verfahren zur hochtemperaturbehandlung von holz
DE102009047137A1 (de) 2009-11-25 2011-05-26 Institut Für Holztechnologie Dresden Gemeinnützige Gmbh Verfahren zur thermischen Modifizierung oder Vergütung von Holz und Holzprodukten
DE102011104025A1 (de) 2010-06-11 2011-12-15 Technische Universität Dresden Verfahren zur Modifizierung von Holz oder Holzwerkstoffen sowie chemisch und thermisch modifiziertes Holz
DE102015013450A1 (de) 2015-10-16 2016-04-14 Daimler Ag Verfahren zum Herstellen eines Holzzierteils

Also Published As

Publication number Publication date
ATE163084T1 (de) 1998-02-15
AU2410695A (en) 1995-12-05
DE69501588D1 (de) 1998-03-12
EP0759137A1 (en) 1997-02-26
DE69501588T2 (de) 1998-09-17
DK0759137T3 (da) 1998-09-23
WO1995031680A1 (en) 1995-11-23

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