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WO1990006840A1 - Method and apparatus for the heating of wood or other materials sensitive to dehydration and heat - Google Patents

Method and apparatus for the heating of wood or other materials sensitive to dehydration and heat

Info

Publication number
WO1990006840A1
WO1990006840A1 PCT/DK1989/000294 DK8900294W WO9006840A1 WO 1990006840 A1 WO1990006840 A1 WO 1990006840A1 DK 8900294 W DK8900294 W DK 8900294W WO 9006840 A1 WO9006840 A1 WO 9006840A1
Authority
WO
WIPO (PCT)
Prior art keywords
wood
chamber
heating
temperature
steam
Prior art date
Application number
PCT/DK1989/000294
Other languages
French (fr)
Inventor
Steen Ole Moldrup
Original Assignee
Steen Ole Moldrup
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 Steen Ole Moldrup filed Critical Steen Ole Moldrup
Publication of WO1990006840A1 publication Critical patent/WO1990006840A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/0278—Processes; Apparatus involving an additional treatment during or after impregnation
    • B27K3/0292—Processes; Apparatus involving an additional treatment during or after impregnation for improving fixation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K1/00—Damping wood
    • B27K1/02—Apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
    • B27K5/001—Heating

Definitions

  • the invention relates to a method and apparatus for the heating of wood or other materials which are sensitive to dehydration and overheating.
  • these agents are characteristic in that the hexavalent chromium reacts with the organic components of the wood, and is hereby converted to trivalent chromium. During this process, the . main part of the chromium, copper, arsenic and phosphate forming part of the agents is precipitated as salts which are difficult to dissolve, and which only with difficulty can be washed out of the wood. This process is called fixation.
  • the speed at which the fixation takes place depends on a number of factors such as, for example, the precise chemical composition of the agents, the concentration of the impregnation agent, the kind of wood etc. However, the speed of fixation depends first and foremost on the temperature of the wood.
  • the heating is effected by the first method of heating with steam at a temperature of 100°C, and with the vacuum drying processes which are known from the similarly above-mentioned US patent publications no. 4,176,466, no. 4,194,296 - and no. 4,198,763, the heating is effected following the second of the two methods of heating, i.e. with hot air.
  • the heating is effected by the steam penetrating the wood pack, where it condenses on the surface of the wood and hereby heats the wood.
  • the penetration of steam into the wood takes place either by diffusion or as a consequence of the dynamic pressure which the vapours achieve in connection with the reduction in pressure which arises when the vapours are introduced into the heating chamber.
  • the greater the re ⁇ duction in pressure the greater will be the dynamic pressure.
  • the use of steam at high pressure in- volves the risk of overheating of the wood and of a strong drying out of the surface of the wood.
  • the heating is effected by hot air being circulated through the wood pack by natural or forced circulation.
  • a circulation of air through the wood pack presupposes that the wood has been carefully stacked with lists between the individual layers of wood.
  • the relative humidity of the air is kept constantly relatively high. This is done by introducing water to the air during the heating, and by ensuring that the temperature of the air does not signi ⁇ ficantly exceed the temperature of the wood. With a small temperature difference, the transfer of heat from the air to the surface of the wood will, however, take place very slowly, and the circulation of very large amounts of air is required.
  • the object of the present invention is therefore to pro ⁇ vide a method for the heating of wood and other materials which are sensitive to dehydration and overheating, by which method the necessary heating and drying of the rele- vant materials is effected in the quickest possible and
  • the transfer of heat will then take place very quickly, even with a small difference in temperature, and thus the heat transfer can take place with steam if the temperature is only slightly higher than the surface temperature of the material in the vacuum chamber, and as already mentioned it is a prerequisite to be able to ensure that the water vapours in the vacuum chamber can be held saturated.
  • Fig. 1 shows schematically an embodiment of the apparatus according to the invention
  • Fig. 2a and 2b show schematically two different embodi ⁇ ments of a steam generator in a condensate tank in the apparatus shown in fig. 1, and Fig. 3 shows the relationship between the surface temperature of material in the apparatus shown in fig.l and the pressure in this apparatus.
  • the heating takes place in an apparatus of the kind shown in fig. 1.
  • the apparatus consists of a vacuum chamber 1 with one or two covers 2 which can be opened.
  • the vacuum chamber must be completely airtight and must be able to withstand full vacuum.
  • the walls 3 of the vacuum chamber should be thermally insulated in order for better control to be effected over the climate in the chamber.
  • the vacuum chamber I is filled batchwise with the material 5 which is desired to be heated.
  • the material 5 is intro ⁇ quizd into the vacuum chamber 1 through the covers 2 in the chamber.
  • the covers 2 are closed and air is evacuated from the chamber 1 by means of a vacuum pump 6, an extractor or a similar element. With this evacuation, as much air as possible is removed from the vacuum chamber 1.
  • saturated water vapour 8 is introduced into the chamber at a temperature which is slightly higher than that of the material in the chamber.
  • the steam is easiest to produce by heating water placed in the vacuum chamber 1 itself or
  • a steam generator 7 which stands in direct connection with the vacuum chamber 1 (see fig. 2).
  • the vacuum chamber 1 In order to ensure that the water vapour produced is saturated and has the same temperature as the surface temperature of the mate ⁇ rial 5 in the vacuum chamber 1, it is important that there is no pressure regulating valve, cut-off or the like between the steam generator 7 and the vacuum chamber 1. The pressure and the temperature in the vacuum chamber and the steam generator must be the same.
  • a measuring element 14 which, in a commonly-known manner, is in connection with a not-shown control unit for the automatic control of the drying process.
  • Use can also be made of steam produced at high pressure in a separate steam generator.
  • the steam must be cooled and have moisture added before it comes into con ⁇ tact with the material 5 in the vacuum chamber 1.
  • This moisturizing is effected most expediently by leading the steam through a water bath, which is placed in the same manner as the water in the steam generator 7 described in the above.
  • the steam 8 will hereby be automatically saturated and assume approximately the same temperature as the surface temperature of the material 5 in the vacuum chamber 1.
  • the steam 8 produced in the steam generator 7 will condense on the surface of the material 5, whereby this is heated. Under gravitation, the condens- ed steam will seek towards the bottom of the vacuum chamber 1.
  • the condensate is collected from the bottom of the vacuum chamber by means of gravitation or by a condensate pump in a condensate tank 9. It can be advantageous to connect the condensate tank directly to the steam generator 7.
  • the pressure in the vacuum chamber 1 will depend on the surface temperature of the material 5 in the vacuum chamber in the relationship as shown in fig. 3, namely that the higher the temperature of the material 5, the greater will f also be the pressure in the vacuum chamber.
  • the steam pressure will be lowest in those areas of the vacuum chamber 1 which are the coldest.
  • the vapours 8 will there ⁇ by automatically seek towards the coldest parts of the va ⁇ cuum chamber 1, and possible temperature differences in the vacuum chamber 1 will thus be equalized rapidly and effectively. Since the movement of the water vapours 8 is due to pressure differences in the vacuum chamber 1, the vapours can penetrate deeply even into materials 5 which are packed tightly, and hereby the system distinguishes itself fundamentally from the earlier described systems of heating.
  • the problems of corrosion can be held on a relatively low level, for the reason that the system is devoid of air.
  • neutralizing amines such as, for example, morpholine
  • the neutralizing amines will remove the acids which emanate from the material 5 during the heating, and without oxygen and acids in the system the corrosion will be extremely limited.
  • the addition of amines is regulated most expe ⁇ trans by measuring the pH of the water collected in the condensate tank 9, and the amine is added in a manner so that the condensate water does not become acid at any time.
  • the walls 3 of the vacuum chamber 1 are provided with heating elements 4 which prevent the condensation of water vapours 8 on the inside walls of the vacuum chamber 1 by holding the temperature of the walls 3 at a slightly higher temperature than the dewpoint temperature of the vapours present in the chamber.
  • the condensate collected in the condensate tank 9 is re ⁇ used with advantage for the production of new steam, in that the condensate collected in the condensate tank is particularly suitable for steam production.
  • the condensate As a con ⁇ sequence of the process taking place in an air-free atmosphere, the condensate is totally devoid of oxygen. In the cases where neutralizing amines are added to the steam, the condensate is also completely devoid of corrosive acids.
  • a considerable amount of the water present in the material 5 can be removed from the material 5 by concluding the heating phase with the vacuum.
  • This concluding vacuum is established most easily by condensing the water vapours in the vacuum chamber 1 by means of not-shown cooling ele- ments disposed in the vacuum chamber 1 or in an also not- shown separate cooling tank. This condensation is effected relatively easily in the present system, as the system is completely evacuated of air prior to the concluding vacuum phase.
  • the condenser With air in the system, as with the known methods of heat ⁇ ing as discussed by way of introduction, the condenser must have a far greater cooling area and lower cooling temperature than required in the condensation of water vapours in an air-free atmosphere. As a consequence here ⁇ of, the system's economy is considerably diminished.
  • the method according to the invention thus affords a number of advantages in relation to the traditional methods of heating.
  • the method according to the invention is not, however, restricted to these applications, and can be used in almost all cases where there is a need for a quick and careful heating of wood or other materials which are sensitive to dehydration and overheating.
  • the method according to the invention can also be used with liquids other than water.
  • the vacuum chamber 1 it lies within the scope of the invention for the vacuum chamber 1 to be filled with hot water instead of with saturated water vapours.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Forests & Forestry (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

The invention relates to a method for the quick and careful heating of wood or other materials which are sensitive to dehydration and heat damage. The heating is effected by placing the material in a chamber from which the air is completely evacuated prior to the heating phase. The chamber is then filled with saturated water vapours at a temperature which does not significantly exceed the temperature of the material which is required to be heated. The heating takes place by the saturated water vapours penetrating the spaces between the individual material parts. Here, the vapours condense on the surface of the material, whereby the material is heated. Among other things, the method can be used with advantage for the fixation of a number of impregnation agents in wood and for the drying of wood. There is also revealed an apparatus for use in the execution of the invention.

Description

METHOD AND APPARATUS FOR THE HEATING OF WOOD OR OTHER MATERIALS SENSITIVE TO DEHYDRATION AND HEAT.
The invention relates to a method and apparatus for the heating of wood or other materials which are sensitive to dehydration and overheating.
In 1988, on a world basis more than 15 million m3 of wood were impregnated with agents consisting of copper and hexavalent chromium, and with arsenic, boron, fluorine or phosphorous as possible third/fourth component.
These agents are characteristic in that the hexavalent chromium reacts with the organic components of the wood, and is hereby converted to trivalent chromium. During this process, the.main part of the chromium, copper, arsenic and phosphate forming part of the agents is precipitated as salts which are difficult to dissolve, and which only with difficulty can be washed out of the wood. This process is called fixation.
The speed at which the fixation takes place depends on a number of factors such as, for example, the precise chemical composition of the agents, the concentration of the impregnation agent, the kind of wood etc. However, the speed of fixation depends first and foremost on the temperature of the wood.
Until the conclusion of fixation, the salts can be washed out of the wood and hereby give rise to environmental problems and problems connected with health. With the increasing environmental demands, there is considerable interest in being able to accelerate the fixation process by heating the newly-impregnated wood in a quick and lenient manner. Also within other areas in the wood industry there are needs for a quick and lenient heating of wood, for example in the drying of wood.
It has long been known that wood can be dried by alternat¬ ing between a heating phase and a vacuum phase, see for example US patent publications no. 3,921,309, no. 3.986,268, no. 4,176,466, no. 4,194,296 and no. 4,198,763. This process is called .vacuum drying.
- With the hitherto-known vacuum drying processes, the heat¬ ing has, however, been carried out by the traditional heating methods, of which can be mentioned:
1. Heating by means of steam with a temperature of 100- 120°C, and
2. Heating by means of hot air.
With the vacuum drying process from the above-mentioned US patent publication no. 3,921,309, the heating is effected by the first method of heating with steam at a temperature of 100°C, and with the vacuum drying processes which are known from the similarly above-mentioned US patent publications no. 4,176,466, no. 4,194,296 - and no. 4,198,763, the heating is effected following the second of the two methods of heating, i.e. with hot air.
Among other known methods for the heating of wood can be mentioned heat radiation, submersion in hot liquid or. by means of high-frequency energy, as in the above-mentioned US patent publication no. 3,986,268. However, these last- mentioned methods of heating are not as common as the aforementioned first and second heating methods.
For the above-mentioned methods of heating, it applies that the heated materials are strongly exposed to drying out during the heating. When using heat radiation, the application of steam and high frequency there is also a great risk of heat damage to the wood in the form of di¬ minished strength, discoloration and resin secretion.
With the first method of heating, the heating is effected by the steam penetrating the wood pack, where it condenses on the surface of the wood and hereby heats the wood. The penetration of steam into the wood takes place either by diffusion or as a consequence of the dynamic pressure which the vapours achieve in connection with the reduction in pressure which arises when the vapours are introduced into the heating chamber. Actually, the greater the re¬ duction in pressure, the greater will be the dynamic pressure. However, the use of steam at high pressure in- volves the risk of overheating of the wood and of a strong drying out of the surface of the wood.
The dynamic pressure disappears rapidly. Therefore, in or¬ der to utilize the dynamic pressure as well as possible, it is important that the supply of steam takes place at many points evenly distributed in the chamber, and there should be ample air spaces between the items of wood in the wood pack, hereby enabling the steam to penetrate the pack unhindered. The latter requires that the individual items of wood are mutually separated by placing lists between them, which results in considerable extra costs. As a consequence of the limited ability of the water vapours to penetrate into the wood pack, the heating often becomes irregular. Moreover, because of the great difference in temperature between the vapours and the wood, the vapours could have a strong drying-out effect on the wood surface.
With the second method of heating, the heating is effected by hot air being circulated through the wood pack by natural or forced circulation. A circulation of air through the wood pack presupposes that the wood has been carefully stacked with lists between the individual layers of wood.
In order to prevent the surface of the wood drying out during the heating in accordance with the second method of heating, it is important for the relative humidity of the air to be kept constantly relatively high. This is done by introducing water to the air during the heating, and by ensuring that the temperature of the air does not signi¬ ficantly exceed the temperature of the wood. With a small temperature difference, the transfer of heat from the air to the surface of the wood will, however, take place very slowly, and the circulation of very large amounts of air is required.
With both the first and the second methods of heating, there are often great problems with corrosion of the materials forming part of the heating chambers, and there¬ fore the chambers should preferably be executed in corrosion-proof materials, which considerably increases the cost of construction.
The object of the present invention is therefore to pro¬ vide a method for the heating of wood and other materials which are sensitive to dehydration and overheating, by which method the necessary heating and drying of the rele- vant materials is effected in the quickest possible and
_•* therewith the most economical manner, and also that the said method shall be devoid of the disadvantages described, and this object is achieved by a method which according to the invention is characteristic in that the wood or the material during heating is placed in an air¬ tight, thermally-insulated chamber which, during the heating phase, is completely evacuated of air and instead filled with saturated steam at a temperature which is only slightly higher than the surface temperature of the material or the wood.
Establishing of a high vacuum in the vacuum chamber makes the steam pressure of the water in the wood exceed the pressure of the surroundings, and the water will thereby start to boil out into the wood. By evaporation of the water the thermal energy in the wood is consumed, and the temperature of the wood will drop until the steam pressure of the water present in the wood corresponds to the pressure of the surroundings, whereby the further drying ceases. By repeating the mentioned heating and evacuation phase several times", the main part of the water in the wood will gradually be removed from the wood.
If the air is evacuated from the vacuum chamber, the transfer of heat will then take place very quickly, even with a small difference in temperature, and thus the heat transfer can take place with steam if the temperature is only slightly higher than the surface temperature of the material in the vacuum chamber, and as already mentioned it is a prerequisite to be able to ensure that the water vapours in the vacuum chamber can be held saturated.
Since the temperature for the saturated steam is only in- significantly higher than the temperature of the material or the wood, no significant increase in the temperature of these takes place, and therefore no heat damage is caused to the wood o /r the material.
It is advantageous to produce the steam in the manner revealed in claim 2, as the least possible heat loss and pressure drop in the steam is hereby achieved.
It is herewith expedient to generate the steam as described in claim 3.
In order to reduce the corrosion in the chamber, it is advantageous to introduce neutralizing amines as revealed in claim 4.
Furthermore, .it is expedient to heat the walls of the chamber, as revealed in claim 5, whereby the condensation of the vapours is countered.
For use in the execution of the method according to the invention, there is'provided an apparatus as revealed and characterized in claim 6.
The method and the apparatus according to the invention will now be described in more detail with reference to the drawing, where
Fig. 1 shows schematically an embodiment of the apparatus according to the invention,
Fig. 2a and 2b show schematically two different embodi¬ ments of a steam generator in a condensate tank in the apparatus shown in fig. 1, and Fig. 3 shows the relationship between the surface temperature of material in the apparatus shown in fig.l and the pressure in this apparatus.
The heating takes place in an apparatus of the kind shown in fig. 1. The apparatus consists of a vacuum chamber 1 with one or two covers 2 which can be opened. The vacuum chamber must be completely airtight and must be able to withstand full vacuum.
The walls 3 of the vacuum chamber should be thermally insulated in order for better control to be effected over the climate in the chamber. In order to limit the condens¬ ation of the water vapour on the inner walls of the chamber, it is an advantage to provide the walls 3 of the vacuum chamber with heating elements 4 which can maintain the walls of the chamber at a temperature which is higher than the dewpoint temperature of the water vapours present in the vacuum chamber 1, but at the same time so low that the water vapours are not heated further by the walls 3.
The vacuum chamber I is filled batchwise with the material 5 which is desired to be heated. The material 5 is intro¬ duced into the vacuum chamber 1 through the covers 2 in the chamber. After the filling of the chamber with mate¬ rial, the covers 2 are closed and air is evacuated from the chamber 1 by means of a vacuum pump 6, an extractor or a similar element. With this evacuation, as much air as possible is removed from the vacuum chamber 1.
After the air has been evacuated from the vacuum chamber 1, saturated water vapour 8 is introduced into the chamber at a temperature which is slightly higher than that of the material in the chamber. The steam is easiest to produce by heating water placed in the vacuum chamber 1 itself or
_•* in a steam generator 7 which stands in direct connection with the vacuum chamber 1 (see fig. 2). In order to ensure that the water vapour produced is saturated and has the same temperature as the surface temperature of the mate¬ rial 5 in the vacuum chamber 1, it is important that there is no pressure regulating valve, cut-off or the like between the steam generator 7 and the vacuum chamber 1. The pressure and the temperature in the vacuum chamber and the steam generator must be the same.
In order to control the surface temperature of the material 5 in the vacuum chamber 1, and also the temperature of the saturated vapours, in the vacuum chamber there is arranged a measuring element 14 which, in a commonly-known manner, is in connection with a not-shown control unit for the automatic control of the drying process.
Use can also be made of steam produced at high pressure in a separate steam generator. In this case the steam must be cooled and have moisture added before it comes into con¬ tact with the material 5 in the vacuum chamber 1. This moisturizing is effected most expediently by leading the steam through a water bath, which is placed in the same manner as the water in the steam generator 7 described in the above. The steam 8 will hereby be automatically saturated and assume approximately the same temperature as the surface temperature of the material 5 in the vacuum chamber 1.
In the vacuum chamber 1, the steam 8 produced in the steam generator 7 will condense on the surface of the material 5, whereby this is heated. Under gravitation, the condens- ed steam will seek towards the bottom of the vacuum chamber 1. The condensate is collected from the bottom of the vacuum chamber by means of gravitation or by a condensate pump in a condensate tank 9. It can be advantageous to connect the condensate tank directly to the steam generator 7.
In order to ensure a rapid transfer of heat from the vapours 8 to the material 5, it is important that in principle the vacuum chamber 1 is completely evacuated of air. The reason for this is that if there is air in the system, a considerable difference in temperature will be necessary between the water vapours 8 and the material 5 in order to ensure a sufficiently rapid transfer of heat. This difference in temperature will have the effect that the vapours around the material 5 will not remain saturated, and there will hereby arise a risk of a strong drying out of the material. There is also a risk of heat damage to the material in the form of reduced strength in the material, resin secretion and discoloration.
The fact that the transfer of heat is very effective, and the fact that there is a direct connection between the vacuum chamber 1 and the steam generator 7, results auto- matically in the vapours produced in the steam generator 7 becoming saturated and that they assume approximately the same temperature as the surface temperature of the material 5 present in the vacuum chamber 1, and this is a precondition for the present system to be able in a simple manner to avoid the drying out of the material 5 in the vacuum chamber 1 and heat damage to the material.
Providing that the vacuum chamber 1 is evacuated of air, the pressure in the vacuum chamber 1 will depend on the surface temperature of the material 5 in the vacuum chamber in the relationship as shown in fig. 3, namely that the higher the temperature of the material 5, the greater will falso be the pressure in the vacuum chamber. In the event of possible pressure differences, the steam pressure will be lowest in those areas of the vacuum chamber 1 which are the coldest. The vapours 8 will there¬ by automatically seek towards the coldest parts of the va¬ cuum chamber 1, and possible temperature differences in the vacuum chamber 1 will thus be equalized rapidly and effectively. Since the movement of the water vapours 8 is due to pressure differences in the vacuum chamber 1, the vapours can penetrate deeply even into materials 5 which are packed tightly, and hereby the system distinguishes itself fundamentally from the earlier described systems of heating.
With the method according to the invention, the problems of corrosion can be held on a relatively low level, for the reason that the system is devoid of air. By adding neutralizing amines such as, for example, morpholine to the water vapours 8 "produced in the steam generator 7, the risk of corrosion can be held on a very low level. The neutralizing amines will remove the acids which emanate from the material 5 during the heating, and without oxygen and acids in the system the corrosion will be extremely limited. The addition of amines is regulated most expe¬ diently by measuring the pH of the water collected in the condensate tank 9, and the amine is added in a manner so that the condensate water does not become acid at any time. In order to further reduce the risk of corrosion, the walls 3 of the vacuum chamber 1 are provided with heating elements 4 which prevent the condensation of water vapours 8 on the inside walls of the vacuum chamber 1 by holding the temperature of the walls 3 at a slightly higher temperature than the dewpoint temperature of the vapours present in the chamber.
The condensate collected in the condensate tank 9 is re¬ used with advantage for the production of new steam, in that the condensate collected in the condensate tank is particularly suitable for steam production. As a con¬ sequence of the process taking place in an air-free atmosphere, the condensate is totally devoid of oxygen. In the cases where neutralizing amines are added to the steam, the condensate is also completely devoid of corrosive acids.
A considerable amount of the water present in the material 5 can be removed from the material 5 by concluding the heating phase with the vacuum. This concluding vacuum is established most easily by condensing the water vapours in the vacuum chamber 1 by means of not-shown cooling ele- ments disposed in the vacuum chamber 1 or in an also not- shown separate cooling tank. This condensation is effected relatively easily in the present system, as the system is completely evacuated of air prior to the concluding vacuum phase.
Out of regard for the condensation of the water vapours in the above-mentioned cooling system, it is important that the vacuum chamber 1 is completely airtight and that it is completely evacuated of air prior to the concluding vacuum phase.
If there is air in the system, a vacuum pump 6, an extractor or a similar element is required for the removal of the air, and the demands on the condenser used for the condensation of the water vapours are considerable.
With air in the system, as with the known methods of heat¬ ing as discussed by way of introduction, the condenser must have a far greater cooling area and lower cooling temperature than required in the condensation of water vapours in an air-free atmosphere. As a consequence here¬ of, the system's economy is considerably diminished.
Moreover, these known methods of heating give rise to great problems with strong drying out of the surface of the wood and other heat damage, and as a consequence of this and other things, vacuum drying has hitherto never found particularly broad application. However, by using the method of heating as revealed with this invention, it is possible to heat the wood in both a quick and careful manner. At the same time, since the process takes place in a completely air-free atmosphere, one avoids the problems in the form of long heating times, difficulties surround- ing the establishing of complete vacuum, corrosion problems and discoloration of the wood, which arise in those systems where"the drying chamber is filled with air during the heating phase.
Both in the fixation of wood and in the drying of wood, the method according to the invention thus affords a number of advantages in relation to the traditional methods of heating. The method according to the invention is not, however, restricted to these applications, and can be used in almost all cases where there is a need for a quick and careful heating of wood or other materials which are sensitive to dehydration and overheating. The method according to the invention can also be used with liquids other than water. Furthermore, it lies within the scope of the invention for the vacuum chamber 1 to be filled with hot water instead of with saturated water vapours.

Claims

C L A I M S
1. Method for the heating of wood or other materials which are sensitive to dehydration and overheating, c h a - r a c t e r i z e d in that during the heating the wood or the material is placed in an airtight, thermally in¬ sulated chamber from which the air is completely evacuated during the heating phase, and instead filled with saturated steam at a temperature which is only slightly higher than the surface temperature of the wood or the material.
2. Method according to claim 1, c h a r a c t e ¬ r z e d in that the steam used for the heating of the wood or the material is produced by the heating of liquid placed either in the chamber itself or in a separate tank which is in direct connection with the chamber.
3. Method according to claim 1, c h a r a c t e - r i z e d in that the steam used for the heating of the wood or the material is produced by a steam generator which is independent of the chamber, and thereafter con¬ verted to saturated steam with a temperature which is only slightly higher than the surface temperature of the wood or the material, by being led through a liquid which is placed either in the chamber itself or in a separate tank which is in direct connection with the chamber.
4. Method according to claim 1, c h a r a c t e - r i z e d in that during the heating phase, neutralizing amines, such as morpholine, are introduced into the chamber for the neutralization of the acids emanating from the wood or the material.
5. Method according to claim 1, c h a r a c t e - r i z e d in that the walls in the chamber are heated to a temperature which is slightly higher than the dewpoint temperature of the vapours present in the chamber.
6. Apparatus for use in the execution of the method as revealed in claim 1, in which wood or other materials sen¬ sitive to dehydration or overheating are heated, c h a ¬ r a c t e r i z e d in that the apparatus comprises a pressure-proof chamber (1) provided with covers (2), in that said chamber (1) can be evacuated by means of a vacuum pump (6) connected with the chamber (1), and a steam generator (7) connected with the chamber (1) via an open channel with large cross-sectional area, and which is arranged for the production of saturated vapours (8), said steam generator (7) being preferably disposed in a con¬ densation tank (9) connected to the chamber (1), and in that a measuring element (14) is provided for the control of the surface temperature of the wood or material (5) present in the chamber (1), and also the temperature and pressure of the saturated vapours.
PCT/DK1989/000294 1988-12-16 1989-12-14 Method and apparatus for the heating of wood or other materials sensitive to dehydration and heat WO1990006840A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK7019/88 1988-12-16
DK701988A DK701988D0 (en) 1988-12-16 1988-12-16 PROCEDURE FOR IMPROVING TREE

Publications (1)

Publication Number Publication Date
WO1990006840A1 true WO1990006840A1 (en) 1990-06-28

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PCT/DK1989/000294 WO1990006840A1 (en) 1988-12-16 1989-12-14 Method and apparatus for the heating of wood or other materials sensitive to dehydration and heat

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CA (1) CA2005419A1 (en)
DK (1) DK701988D0 (en)
WO (1) WO1990006840A1 (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994027102A1 (en) * 1993-05-12 1994-11-24 Valtion Teknillinen Tutkimuskeskus Method for improving biodegradation resistance and dimensional stability of cellulosic products
AU665058B2 (en) * 1992-03-12 1995-12-14 New Zealand Forest Research Institute Limited A bark extractant and method for preparing same
WO1995035191A1 (en) * 1994-06-17 1995-12-28 Seidner Marc A Method for heat-treating wood and wood products
WO2007039590A1 (en) * 2005-10-04 2007-04-12 Basf Se Production of modified lignocellulosic materials
WO2003106123A3 (en) * 2002-06-07 2009-03-26 Iwotech As A method and an apparatus for heat treatment of wooden objects
US7939177B2 (en) 2005-10-04 2011-05-10 Basf Aktiengesellschaft Lignocelluosic material which is low in formaldehyde and method for the production thereof
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
FR3063925A1 (en) * 2017-03-20 2018-09-21 Thermodynamic Workshop Training - Twt THERMAL TREATMENT DEVICE FOR LOGS
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 (4)

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Publication number Priority date Publication date Assignee Title
US1678559A (en) * 1927-05-28 1928-07-24 Joseph P Devine Drying materials
US2293453A (en) * 1939-02-24 1942-08-18 Gen Electric Dehydrating treatment
EP0199092A1 (en) * 1985-03-22 1986-10-29 Dr. Wolman GmbH Process for the accelerated fixation of chromate-containing wood preservative salts
DE3630743A1 (en) * 1986-09-10 1988-03-24 Scholz Gmbh Co Kg Maschbau METHOD AND DEVICE FOR THE SALT IMPREGNATION OF WOOD

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1678559A (en) * 1927-05-28 1928-07-24 Joseph P Devine Drying materials
US2293453A (en) * 1939-02-24 1942-08-18 Gen Electric Dehydrating treatment
EP0199092A1 (en) * 1985-03-22 1986-10-29 Dr. Wolman GmbH Process for the accelerated fixation of chromate-containing wood preservative salts
DE3630743A1 (en) * 1986-09-10 1988-03-24 Scholz Gmbh Co Kg Maschbau METHOD AND DEVICE FOR THE SALT IMPREGNATION OF WOOD

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU665058B2 (en) * 1992-03-12 1995-12-14 New Zealand Forest Research Institute Limited A bark extractant and method for preparing same
WO1994027102A1 (en) * 1993-05-12 1994-11-24 Valtion Teknillinen Tutkimuskeskus Method for improving biodegradation resistance and dimensional stability of cellulosic products
US5678324A (en) * 1993-05-12 1997-10-21 Valtion Teknillinen Tutkimuskeskus Method for improving biodegradation resistance and dimensional stability of cellulosic products
WO1995035191A1 (en) * 1994-06-17 1995-12-28 Seidner Marc A Method for heat-treating wood and wood products
WO2003106123A3 (en) * 2002-06-07 2009-03-26 Iwotech As A method and an apparatus for heat treatment of wooden objects
US7963048B2 (en) * 2005-05-23 2011-06-21 Pollard Levi A Dual path kiln
US7939177B2 (en) 2005-10-04 2011-05-10 Basf Aktiengesellschaft Lignocelluosic material which is low in formaldehyde and method for the production thereof
WO2007039590A1 (en) * 2005-10-04 2007-04-12 Basf Se Production of modified lignocellulosic materials
AU2006298714B2 (en) * 2005-10-04 2011-08-11 Basf Se Production of modified lignocellulosic materials
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
FR3063925A1 (en) * 2017-03-20 2018-09-21 Thermodynamic Workshop Training - Twt THERMAL TREATMENT DEVICE FOR LOGS
WO2018172343A1 (en) * 2017-03-20 2018-09-27 Thermodynamic Workshop Training - Twt Device for the thermal treatment of logs
EA039559B1 (en) * 2017-03-20 2022-02-10 Термодинамик Воркшоп Трейнинг - Твт Device for the thermal treatment of logs
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
DK701988D0 (en) 1988-12-16
AU4809490A (en) 1990-07-10
CA2005419A1 (en) 1990-06-16

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