Apparatus and method for drying and/or curing of materials

Abstract

The invention involves an apparatus and a method for drying and/or curing impregnated wood. The apparatus includes a chamber comprising a stack containing space for containing a plurality of elongated wood planks arranged in a stack of a height H.sub.s, width W.sub.s and length L.sub.s, a heating element arranged within or adjacent to the space, a flow generating device arranged outside the space and configured to generate a circulating flow (F) of curing fluid within the chamber and a fluid flow restrictor arranged between the space and the flow generating device. The flow generating device and the fluid flow restrictor are further configured such that the circulating flow (F) of curing fluid is guided through the heating element generating a homogeneously heated and distributed flow (F) of curing fluid in the space. At least one motor is arranged outside the chamber, the at least one motor being configured to operate the flow generating device via a connecting shaft.

Claims

1. An apparatus for curing impregnated wood, wherein the apparatus comprises a chamber comprising: a stack containing space for containing a plurality of elongated wood planks arranged in a stack of a height H.sub.s, width W.sub.s and length L.sub.s, a heating element for heating curing fluid arranged within or adjacent to the stack containing space, wherein the size and orientation of the heating element is configured such that the heating element extends along at least the height H.sub.s and the length Ls of the stack's surface area when the stack has been inserted into the stack containing space, a fan arranged outside the stack containing space and configured to generate a circulating flow of curing fluid within the chamber and a fluid flow restrictor arranged between the stack containing space and the fan, wherein the fluid flow restrictor is having a size and orientation extending over the entire surface area of the stack in the stack's length L.sub.s and width W.sub.s and/or the height H.sub.s and width W.sub.s when the stack (3) has been inserted into the stack containing space (11), wherein the fan and the fluid flow restrictor are further configured such that the circulating flow of curing fluid is guided through the heating element generating a homogeneously heated and distributed flow of curing fluid in the stack containing space, and wherein the apparatus further comprises at least one motor arranged outside the chamber, the at least one motor being configured to operate the fan via a connecting shaft, wherein a part of the shaft contained within the chamber is arranged within an enclosing tube that, during operation, contains an inert gas.

2. The apparatus according to claim 1, wherein the fluid flow restrictor is arranged between 0.1 and 50 cm from the stack, during use.

3. The apparatus according to claim 1, the fan is arranged within or adjacent to at least one fluid flow preventing wall, the at least one wall being configured to guide the flow of curing fluid fully through the fan.

4. The apparatus according to claim 1, wherein the chamber is comprising at least two heating elements, wherein at least two heating elements are arranged on the opposite side of the stack extending along at least the height H.sub.s and the length L.sub.s of the stack's surface area when the stack has been inserted into the stack containing space.

5. The apparatus according to claim 1, wherein heating elements are arranged between 0.1 and 50 cm from the stack during use.

6. The apparatus according to claim 1, wherein the chamber is comprising at least three heating elements, wherein at least two of the at least three heating elements are arranged on the opposite side of the stack extending along at least the height H.sub.s and the length L.sub.s of the stack's surface area when the stack has been inserted into the stack containing space, and at least one of the at least three heating elements is arranged in between the at least two opposite arranged heating elements.

7. The apparatus according to claim 1, wherein the heating element comprises a plurality of interconnected pipes for flow of heating element fluid therethrough, wherein the plurality of pipes are spaced apart, thereby forming a plurality of slits into which the circulating flow of curing fluid may pass through during operation.

8. The apparatus according to claim 1, wherein the heating element comprises a plurality of interconnected horizontal pipes and vertical pipes for flow of heating element fluid therethrough, wherein at least two horizontal pipes are spaced apart by the plurality of vertical pipes forming a plurality of slits into which the flow of curing fluid may pass through during operation.

9. The apparatus according to claim 8, wherein the number of vertical pipes exceeds the number of horizontal pipes by a factor of at least 2.

10. The apparatus according to claim 8, wherein the plurality of vertical pipes are equally or near equally spaced apart, and the plurality of horizontal pipes are equally or near equally spaced apart.

11. The apparatus according to claim 10, wherein each of the plurality of pipes are straight.

12. The apparatus according to claim 11, wherein each of the plurality of pipes has a smooth outer surface.

13. The apparatus according to claim 1, wherein the elongated wood planks, when installed within the stack containing space are being separated in height by spacer elements, thereby allowing the flow of curing fluid to circulate between the stacked layers of elongated wooden planks.

14. The apparatus according to claim 1, wherein the chamber further comprises a chamber floor at or adjacent to a base of the stack containing space intended to support the stack, wherein the chamber floor has a gradient allowing continuous drainage of deposits originating from the stack during operation.

15. The apparatus according to claim 14, wherein the chamber displays at least one drain port in or adjacent to the gradient chamber floor for continuously draining any deposits originating from the wood planks during operation.

16. The apparatus according to claim 1, wherein the end of the enclosing tube connected to the chamber wall of the chamber encloses at least one inert gas inlet allowing inlet of inert gas from outside the chamber into the enclosing tube and that the other end of the enclosing tube arranged adjacent to the fan has at least one outlet penetrating its enclosing tube wall, allowing outlet of inert gas through the enclosing tube.

17. A method for drying and/or curing impregnated wood in an apparatus according to claim 1, for obtaining a homogeneously heated and homogeneously distributed flow of curing fluid within the stack containing space comprising the flowing steps: a) inserting the stack of wood planks inside the stack containing space of the chamber, b) sealing the chamber, c) activating the fan for producing a circulating flow of curing fluid inside the chamber and d) forcing the circulating flow of curing fluid to pass through the heating element.

18. The method according to claim 17, wherein the method further comprises the step of flushing the chamber with an inert gas prior to step c) to remove oxygen from the atmosphere inside the chamber.

19. The method according to claim 18, wherein the method further comprises the step of continuously draining deposits originating from the wooden planks during operation through at least one drain port.

20. The apparatus according to claim 1, wherein the fluid flow restrictor is arranged between 0.3 and 20 cm from the stack during use.

21. The apparatus according to claim 1, wherein the fluid flow restrictor is arranged between 0.5 and 5 cm from the stack during use.

22. The apparatus according to claim 1, wherein heating elements are arranged between 0.3 and 20 cm from the stack during use.

23. The apparatus according to claim 1, wherein heating elements are arranged between 0.5 and 5 cm from the stack.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a cross-sectional front view of an apparatus according to the present invention.

(2) FIG. 2 shows a perspective three-dimensional view of an open apparatus according to the present invention.

(3) FIG. 3 shows the same as FIG. 2.

(4) FIG. 4 shows a perspective side view of an open apparatus according to the present invention.

(5) FIG. 5 shows a stack of wood.

(6) In the drawings, equal reference numbers refer to equal equipment.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 to 4 shows an open apparatus according to one exemplary embodiment of the invention comprising a chamber 1 for drying and/or curing a stack 3 comprising two partial stacks 3″ of elongated planks 3′. The planks 3′ to be dried can formerly be saturated, impregnated or dosed with an impregnation solution of a polymerizable monomer or oligomer, thus the wood can be cured in the same apparatus.

(8) In terms of general operation, the chamber 1 comprises a least one door (not shown) to pass the stack 3 of partial stacks 3″ of elongated planks 3′ in and out of the chamber 1. The door is closed in a sealed manner during the drying and/or curing process of the planks 3′.

(9) The chamber 1 displays a stack containing space 11 having a stack 3 of two partial stacks 3″ of planks 3′ in a height H.sub.s (see FIG. 3). As illustrated the partial stacks 3″ of elongated planks 3′ are arranged adjacent to each other.

(10) Further, as can be seen in FIGS. 2 and 3, a plurality of fans 7 are arranged on top of the stack containing space 11, but may in another arrangement be arranged in front, back and/or underneath/below the stack containing space 11.

(11) The plurality of fans 7 are arranged inside openings of a wall 12.

(12) During drying and/or curing so-called “top condensate” is created comprising inter alia steam from water and volatile organic chemicals (VOC). To avoid the possibility of explosion, the fan(s) 7 are connected to electric motor(s) 9 arranged outside the chamber 1 via rotating shaft(s). The shaft(s) are arranged in protective tube(s) 10 comprising an inert gas that is led through the tube 10 from an inlet from the outside of the chamber 1 to an outlet penetrating through the tube 10 at or adjacent to the flow generating device 7.

(13) The operation of the fan motor(s) 9 can be regulated by controller(s) (not shown) regulating the speed and/or direction of the flow (F) of curing fluid within the chamber 1.

(14) A fluid flow restrictor 6 is arranged between the stack containing space 11 and the fan 7 prohibiting the flow (F) of curing fluid to pass therethrough, thereby guiding the flow (F) of curing fluid through the heating elements 2.

(15) To establish a homogenous flow (F) of curing fluid inside the stack containing space 11, the fluid flow restrictor 6 is arranged as closely as possible to the stack 3 or partial stack 3″. Further, each heating element 2 has two horizontal longitudinal pipes 2a,b separated by a plurality of equally spaced vertical longitudinal pipes 2c forming a plurality of slits 4 (see FIG. 4), wherein the flow (F) of curing fluid passes through the slits 4. As can be seen from FIG. 1 to 4 the chamber 1 comprises three heating elements 2 arranged on each side of the partial stacks 3″ along the height H.sub.s and length L.sub.s of the stack 3. The vertical and horizontal longitudinal pipes can be hollow and in fluid communication with each other allowing heating element fluid to pass therein.

(16) Further it is shown in FIG. 1 to 4 that the partial stacks 3″ in the stack 3 are arranged on top of support elements 8. The support elements 8 are creating a space between the stack 3 and the gradient floor 14 of the chamber 1, thus allowing condensate which is produced during drying and/or curing to precipitate to the gradient floor 14 and subsequently be removed through a drain port 15.

(17) Further the support elements 8 are arranged to enclose a volume underneath the stacked materials thereby guiding the flow (F) of curing fluid to enter into the stack containing space 11 through the slits 4 between the vertical longitudinal pipes 2c prohibiting the flow (F) of curing fluid to enter the stack containing space 11 from underneath the stack.

(18) During drying and/or curing, the pressure inside the chamber 1 increases and an outlet channel 5 guides a part of the curing fluid out of the chamber 1 into a capacitor (not shown) to lower the pressure inside the chamber 1.

(19) FIG. 1 indicates the flow (F) of curing fluid during drying and/or curing. Even if the flow (F) is alternating during operation, the figure illustrates only one direction of the flow (F). As can be seen from FIG. 1 the flow (F) of curing fluid is concentrated (indicated by large arrows) when leaving the fan 7. When the flow (F) of curing fluid passes into the stack containing space 11, through the slits 4 formed by the heating element 2, the concentrated flow (F) is divided into a homogenously distributed flow (F) (indicated by small arrows) which passes through the gaps 16 between the planks 3′ in one of the two partial stacks 3″ before entering through slits 4 of another heating element 2 which contributes to maintain the homogeneous flow (F) when the flow (F) is entering the second partial stack 3″. Before the flow (F) of curing fluid is leaving the stack containing space 11, it passes through the slits 4 of yet another heating element (2) which also contributes to maintain a homogeneous flow (F) within the stack containing space 11. Thereafter the flow (F) is concentrated again before passing through the fan 7.

(20) As shown in FIG. 1 the upper horizontal pipe 2a of the heating element 2 is in contact with the fluid flow restrictor 6, thus guiding the flow of curing fluid through the slits 4 of the heating element 2.

(21) FIGS. 2 and 3 are three dimensional views of an open apparatus of the exemplary embodiment of the present invention showing the arrangement of a plurality of fans 7 arranged in parallel inside openings in the wall 12. As can be seen from the figure the heating elements 2 are arranged along the side of the stack comprising space 11 covering the entire side surface of the stack 3 along the height H.sub.s and length L.sub.s thereof.

(22) In another exemplary embodiment the apparatus may comprises only one heating element 2 arranged on the one side of the stack containing space, and the flow (F) of curing fluid may enter the stack containing space 11 before or after passing through the slits 4 of the heating element 2, depending on the direction of the flow (F). Due to the drop in pressure before the flow (F) enters through the slits 4, a homogeneously distributed flow (F) of curing fluid is obtained within the stack containing space 11 independently of the direction of the flow (F) of curing fluid.

(23) FIG. 5 illustrates a stack 3 of wooden planks 3′ wherein the planks 3′ are separated by spacer elements 13 in the direction of the height H.sub.s thereby creating a gap 16 between the planks 3′. FIG. 5 may also illustrate one partial stack 3″ of planks 3′, since a stack 3 may comprise one or more partial stacks 3″ of planks 3′. The gap 16 allows the flow (F) of curing fluid to pass therethrough during operation. If the stack 3 comprises one partial stack 3″, the stack 3 and the partial stack 3″ has the same size.

EXAMPLE OF A DRYING AND CURING PROCESS

(24) This example describes drying and curing wherein the elongated material is wood pre-treated with an impregnating material such as a monomer or oligomer which polymerizes during curing. The drying and curing operate to produce polymer impregnated cured wood. The pre-treating method is known from for example WO 2011/144608 A1 and will not be described in further detail.

(25) During drying and curing of wood comprising an impregnating solution, the increased temperature in the atmosphere inside the apparatus will result in removal of water (drying) and polymerization (curing) of the impregnating solution.

(26) The pre-treated planks of wood 3′ are arranged in layers of planks 3′ uniformly separated in height H.sub.s by spacer elements 13 creating a gap 16 between the planks 3′, thereby obtaining a partial stack 3″. The stack 3 which may comprise one or more partial stacks 3″ of planks 3′ are placed inside the stack containing space 11 of the chamber 1 by passing through a door. The door is closed in a sealed manner before the drying and/or curing process is activated.

(27) Before the drying or curing can be carried out, most of the oxygen inside the chamber 1 is removed. Oxygen inside the chamber 1 may otherwise react with volatile chemical compounds (VOCs) which are developed during drying and/or curing to cause an explosion inside the chamber 1. The chamber 1 is therefore filled with an inert gas such as nitrogen or argon passing through an inlet channel (not shown in the figures) and the fluid inside the chamber 1 is removed through the outlet channel 5.

(28) Thereafter the drying and curing process is achieved by circulating the curing fluid (F) in the chamber 1.

(29) The flow (F) of the curing fluid is driven and circulated by at least one fan 7. By arranging a fluid flow restrictor 6 between the stack containing space 11 and the fan 7, the flow of curing fluid is guided into the stack containing space 11 through slits 4 in the heating element 2. The fan 7 may be arranged centrally above the fluid flow restrictor 6 to obtain an equal flow distance from the stack containing space 11 when the fan alternates the direction of the flow (F) of curing fluid.

(30) The stack 3 of wood planks 3′ are arranged on top of support elements 8, wherein the support elements 8 blocks the fluid flow (F) from entering inside the stack containing space 11 from underneath.

(31) The flow (F) of curing fluid is forced through the slits 4 between the vertical elongated pipes 2c of the heating elements 2 into the stack containing space 11 indicated by arrows in FIG. 1. The bigger the arrows in the FIG. 1, the faster is the velocity of the flow (F) of the curing fluid. The heating elements 2 comprise hollow pipes 2a-c configured to receive and distribute a heating element fluid (for example steam) within the vertical and horizontal hollow longitudinal pipes 2a-c. The temperature of the curing fluid can be regulated by regulating the temperature of the heating element fluid entering the pipes 2a-c of the heating element 2. The curing fluid can thus obtain a desired temperature when passing through the slits 4 and the temperature of the curing fluid and the distribution of flow (F) becomes uniform/homogeneous within the stack containing space 11. This uniformly heated curing fluid passes into the stack 3 of wooden planks 3′ and is being uniformly distributed through the gaps 16 established by the spacer elements 13. The wooden planks 3′ inside the stack 3 are thereby uniformly dried by the curing fluid which vaporizes the water inside the wooden planks 3′ and polymerizes the impregnating solution. The configuration of the apparatus results in that all the dried wooden planks 3′ produced comprises a uniform amount of water and polymer regardless of their position inside the stack containing space 11.

(32) As can be seen from FIG. 1-4, two parallel sets of heating elements 2 can be arranged centrally between two adjacent partial stacks 3″ of planks 3′. Such an arrangement of heating elements 2 contributes to a uniform/homogeneous flow (F) and temperature of curing fluid through the entire passage inside the stack containing space 11. The flow (F) of curing fluid is subsequently guided through the fan(s) 7 to continue the drying and curing process. A small amount of curing fluid can be guided out of the chamber 1 through the outlet channel 5 when the atmosphere in the chamber 1 expands as the water from the planks evaporates.

(33) To contribute to a homogeneous drying and curing of the wood inside the chamber 1 independently on the location of the wood, the fan 7 is alternating the direction of the flow (F) of curing fluid frequently during operation.

(34) During drying and curing released resins and polymerizable components tend to deposit on the surfaces of the heating elements 2. When the polymers and/or resin stick onto the heating elements 2, they grow layers on the heating elements 2 which over time result in clogging of the slits between the elements 2. Thus, the growing of resins and or polymers on the heating elements 2 causes a major reduction in the heating effect from the elements 2 and the thicker the heating elements 2 become due to layers of polymers and/or resins stuck thereto, the less curing fluid passes through the slits 4 between them. This results in reduced heat transfer between heating elements 2 and the curing fluid, and consequently causes extended process times and an uneven flow (F) of curing fluid within the stack 3 of wood, giving products with uneven residual moisture contents.

(35) Thus, to reduce the above-mentioned problems, the heating elements 2 are configured to comprise straight hollow longitudinal pipes (2a-c) having a smooth surface. The resins and polymers may therefore easily be scaling or flaking off the surface of the pipes (2a-c) and precipitate to the bottom of the chamber 1 during use, and/or can be easily removed from the surfaces of the pipes (2a-c) after use by cleaning with for example high pressure water or steam, or high pressure air.

(36) Both during the drying and the curing process, liquid state resins originating from the wood are created as well as other residual liquid components, and combines to a so-called bottom condensate, comprising inter alia released water, resins and polymers, which fall down/precipitate to the bottom/floor 14 of the chamber 1. The gradient or sloping chamber floor 14 having a drain port 15 in or adjacent to the floor 14 provides continuous draining of the bottom condensate. The bottom condensate may be routed to a separation tank outside the chamber 1 that permits separation of the re-useable parts of condensate from unusable heavy density polymers.

(37) To avoid the possibility of explosion, the electric fan motor 9 is arranged outside the chamber 1. Further, the moving parts of the shaft needing lubrication to function properly, are arranged inside an enclosing tube 10 of inert gas, and the top condensate comprising VOCs which tend to degrade the lubricants are hindered from entering the enclosing tube 10. The excess vapour is removed from the chamber 1 by routing it through the outlet channel 5 to condensers and tanks outside the chamber 1 for reuse in a mixing tank for new impregnation solution.

LIST OF REFERENCE NUMERALS/LETTERS

(38) 1 chamber 2 heating element 2a,b horizontal pipe 2c vertical pipe 3 stack 3′ elongated wooden planks 3″ partial stack 4 opening/slit 5 outlet channel 6 fluid flow restrictor 7 flow generating device 8 support element 9 motor 10 enclosing tube 11 stack containing space 12 fluid flow preventing wall 13 spacer elements 14 chamber floor 15 drain port 16 gap between the planks F flow of curing fluid H.sub.s height of a stack L.sub.s length of a stack W.sub.s width of a stack