EP1439359A2 - Verfahren zum Erwärmen von Holz - Google Patents

Verfahren zum Erwärmen von Holz Download PDF

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Publication number
EP1439359A2
EP1439359A2 EP03445138A EP03445138A EP1439359A2 EP 1439359 A2 EP1439359 A2 EP 1439359A2 EP 03445138 A EP03445138 A EP 03445138A EP 03445138 A EP03445138 A EP 03445138A EP 1439359 A2 EP1439359 A2 EP 1439359A2
Authority
EP
European Patent Office
Prior art keywords
temperature
wet
timber
atmosphere
dry
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.)
Withdrawn
Application number
EP03445138A
Other languages
English (en)
French (fr)
Other versions
EP1439359A3 (de
Inventor
Thomas Wamming
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.)
Valutec AB
Original Assignee
WSAB FINLAND Oy
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
Application filed by WSAB FINLAND Oy filed Critical WSAB FINLAND Oy
Publication of EP1439359A2 publication Critical patent/EP1439359A2/de
Publication of EP1439359A3 publication Critical patent/EP1439359A3/de
Withdrawn legal-status Critical Current

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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
    • F26B21/00—Arrangements for supplying or controlling air or other gases for drying solid materials or objects
    • F26B21/30—Controlling, e.g. regulating, parameters of gas supply
    • 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 goods
    • F26B2210/16—Wood, e.g. lumber, timber

Definitions

  • the present invention relates to a method of heating timber to a predetermined temperature in a preheating phase of a timber drying process, wherein said predetermined temperature is the starting temperature of a following drying process.
  • the timber is preheated in a substantially closed chamber in which there is sustained a water vapour atmosphere that has a wet temperature and a dry temperature.
  • the method involves increasing the wet and the dry temperature of said atmosphere.
  • warm air is used as a heat and moisture transport medium for heating and drying timber in such chambers.
  • the timber is preheated in stacks or batches to the starting temperature of the following timber drying process. It has been found that cracks appear in the outer surface of the timber during the preheating phase.
  • the object of the present invention is to shorten the time taken by the timber preheating process.
  • This object is achieved in accordance with the invention by means of a method of heating timber in a preheating phase of a drying process, comprising the steps of feeding the timber into an at least generally closed chamber, maintaining in said chamber an atmosphere that contains water vapour and that has a wet temperature and a dry temperature, and increasing the wet and the dry temperature of said atmosphere.
  • the process according to the invention is characterised by raising the dry temperature in accordance with the rise in the wet temperature.
  • the dry temperature is maintained at a level of at most 5 degrees above the wet temperature.
  • the dry temperature will differ from the wet temperature by at least 0.1 degree.
  • degrees is meant degrees Celsius.
  • adaptation of the dry temperature to the wet temperature is caused to continue until the predetermined temperature has been reached.
  • adaptation of the dry temperature is carried out intermittently until the predetermined temperature has been reached.
  • the preferred rise in wet temperature is followed by an equally large rise in the dry temperature.
  • the difference between the wet and the dry temperature may swing about a constant value, e.g. 3 degrees.
  • the rise in wet temperature is optimised.
  • the timber placed in the drying chamber has a much lower temperature at the onset of the preheating phase than at the end of said phase, i.e. at the transition from the preheating phase to the drying phase.
  • the timber may often have a temperature beneath 0°C, particularly in the wintertime. This means that the water present in the timber is in the form of ice, which must be melted.
  • a conventional method of heating timber from its current temperature in a drying chamber to a predetermined value, for example a temperature of 57°C, corresponding to the wet temperature of the chamber atmosphere at which the transition to the drying phase is intended to take place is to increase the temperature of the timber linearly from the starting value to the end value.
  • the preheating time will depend on the desired increase in temperature per unit of time.
  • Such a preheating phase is illustrated in the figure by the straight line 2.
  • the ordinate axis and the abscissa axis are ungraded and show temperature, °C, and time, h, respectively.
  • a broken line illustrates the ordinate, T, for termination of the preheating phase at which the temperature of the drying phase commences.
  • aqueous steam is delivered to the chamber atmosphere when preheating timber in accordance with the invention, this steam atmosphere being caused to circulate through and around the stacks of timber in the chamber.
  • the atmosphere is also heated after its passage through the timber stacks and aqueous steam is then added to the heated atmosphere.
  • Heating of the atmosphere is normally effected by passing the atmosphere through or past electric elements.
  • the wet temperature of the atmosphere is measured either intermittently or continuously.
  • the delivery of heat to the atmosphere is adjusted with a starting point from the measured wet temperature of said atmosphere.
  • the set control value of the dry temperature of the atmosphere will preferably be less than 5°C higher than the wet temperature of the atmosphere. This temperature difference is normally 0.1-5 degrees, preferably 2-3°C.
  • the control value of the dry temperature is changed to an extent corresponding to the rise in wet temperature of the atmosphere.
  • This adjustment of the control value of the temperature of the atmosphere shall take place at least generally continuously or intermittently.
  • the control value of the dry temperature of the atmosphere may be changed when the wet temperature of the atmosphere has risen by 0.1 °C or by some other appropriate value, for example by 0.5 or 1 degree. If the wet temperature of the atmosphere has risen by 0.1 of a degree, the control value for the dry temperature will be increased by the same amount.
  • the greatest possible steam generating power is used for the timber preheating process, in other words the maximum steam generating capacity of the plant is used to this end.
  • the preheating phase may be terminated when the wet temperature of the atmosphere is in the order of 57°C or some other temperature at which it is intended to start the drying process.
  • the non-rectilinear graph 1 shown in the figure illustrates the preheating sequence according to the invention.
  • the starting temperature of the timber is shown to lie above 0°C, for instance 5°C. It will be seen from the figure that preheating of timber with a starting point from mutually the same starting temperature to mutually the same final temperature is achieved much more quickly by means of the present invention than by means of the known rectilinear preheating process. It has been found that when practising the present invention, the same final timber preheating temperature is achieved much more quickly than was hitherto possible. This time gain is at least 10 percent, and in particularly favourable cases up to 50 percent.
  • the curves shown in the graph represent the mean values around which the actual values vary. Such variations may depend on the set parameter values and system inertia.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Microbiology (AREA)
  • Chemical And Physical Treatments For Wood And The Like (AREA)
  • Drying Of Solid Materials (AREA)
EP03445138A 2003-01-20 2003-11-26 Verfahren zum Erwärmen von Holz Withdrawn EP1439359A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0300140 2003-01-20
SE0300140A SE524666C2 (sv) 2003-01-20 2003-01-20 Sätt att värma virke till torktemperatur

Publications (2)

Publication Number Publication Date
EP1439359A2 true EP1439359A2 (de) 2004-07-21
EP1439359A3 EP1439359A3 (de) 2007-05-09

Family

ID=20290173

Family Applications (1)

Application Number Title Priority Date Filing Date
EP03445138A Withdrawn EP1439359A3 (de) 2003-01-20 2003-11-26 Verfahren zum Erwärmen von Holz

Country Status (3)

Country Link
EP (1) EP1439359A3 (de)
NO (1) NO20040247L (de)
SE (1) SE524666C2 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7963048B2 (en) * 2005-05-23 2011-06-21 Pollard Levi A Dual path kiln
US8201501B2 (en) 2009-09-04 2012-06-19 Tinsley Douglas M Dual path kiln improvement
US10619921B2 (en) 2018-01-29 2020-04-14 Norev Dpk, Llc Dual path kiln and method of operating a dual path kiln to continuously dry lumber

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995022035A1 (en) 1994-02-11 1995-08-17 ABB Fläkt AB Method and arrangement for drying wood

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1863943A (en) * 1928-12-07 1932-06-21 Utility Mfg And Sales Company Process and apparatus for drying lumber
US3386183A (en) * 1966-10-03 1968-06-04 Weyerhaeuser Co Lumber dryer and drying method
FR2046389A5 (de) * 1969-04-24 1971-03-05 Dso Avtomatisazia Pribor
US3714716A (en) * 1970-06-29 1973-02-06 Weyerhaeuser Co Process for kiln drying lumber by means of a predetermined drying rate
SE504818C2 (sv) * 1995-08-14 1997-04-28 Utec Sm Ab Förfarande vid torkning av virke

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995022035A1 (en) 1994-02-11 1995-08-17 ABB Fläkt AB Method and arrangement for drying wood

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7963048B2 (en) * 2005-05-23 2011-06-21 Pollard Levi A Dual path kiln
US8201501B2 (en) 2009-09-04 2012-06-19 Tinsley Douglas M Dual path kiln improvement
US8342102B2 (en) 2009-09-04 2013-01-01 Douglas M Tinsley Dual path kiln improvement
US10619921B2 (en) 2018-01-29 2020-04-14 Norev Dpk, Llc Dual path kiln and method of operating a dual path kiln to continuously dry lumber

Also Published As

Publication number Publication date
SE0300140D0 (sv) 2003-01-20
SE0300140L (sv) 2004-07-21
NO20040247L (no) 2004-07-21
EP1439359A3 (de) 2007-05-09
SE524666C2 (sv) 2004-09-14

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