Sawed wood drying system with secondary air circulation

Abstract

A sawn wood drying system, which allows to take advantage of the heat contained in the dry wood that leaves the system to preheat the wet and cold wood that enters the system, the system comprising: a heating chamber, a drying chamber and a cooling chamber, sequentially arranged, and a transport path that allows the transfer of sawn wood through these three chambers; a first air circulation system, which provides a first high temperature air flow inside the drying chamber; and a second air circulation system that provides a second air flow, independent of the first air flow, which allows the heating chamber to be in fluid communication with the cooling chamber by means of external chambers or ducts connecting both chambers.

Claims

1. A sawn wood drying system, comprising: a heating chamber, a drying chamber and a cooling chamber, sequentially arranged, and a transport path that allows transfering sawn wood through the heating chamber, the drying chamber and the cooling chamber; a first air circulation system, which provides a first temperature air flow inside the drying chamber; and a second air circulation system, which provides a second air flow, independent of the first air flow, and allows the heating chamber to be in fluid communication with the cooling chamber through external chambers or ducts directly connecting said heating chamber and said cooling chamber.

2. The drying system of claim 1, wherein the second air circulation system comprises at least one fan that drives the second air flow, which are located on the external chambers or ducts, either in an entrance, an exit, or in a central part thereof.

3. The drying system of claim 2, wherein the heating, drying and cooling chambers are separated from each other by separation walls, which also allow operating said first and second air circulation systems independently.

4. The drying system of claim 3, wherein the external chambers or ducts are located adjacent to external side walls of the drying system, symmetrically, on opposite sides thereof.

5. The drying system of claim 4, wherein the drying chamber comprises inclined side walls extending from a top to a bottom of the drying chamber at an angle inside the drying chamber, reducing a space in the first air circulation system.

6. The drying system of claim 5, wherein the inclined side walls extend from a bottom of heaters to the bottom of the drying chamber.

7. The drying system of claim 5, wherein the inclined side walls extend from a level of a dropped ceiling or the level of a top of piles of wood, to a bottom of the piles of wood.

8. The drying system of claim 5, wherein a hallway is arranged in a lower part of the external chambers or ducts to facilitate circulation of people.

9. The drying system of claim 3, wherein the external chambers or ducts are arranged in an upper part of the drying system, thereby communicating the heating and cooling chambers above the drying chamber.

10. The drying system of claim 9, wherein the drying chamber comprises two inclined walls in an upper part of said drying chamber for circulating the second air flow, allowing a fluid communication between the heating and cooling chambers.

11. The drying system of claim 1, wherein each of the heating chamber, the drying chamber and the cooling chamber includes one section or a plurality sections separated or communicated with each other.

12. The drying system according to claim 1, further comprising two transport paths for the transport of vehicles loaded with wood piles, and one or more central heaters between both transport paths, arranged along an entire drying zone or in one or more sections thereof.

13. The drying system according to claim 1, wherein the drying system is a progressive or continuous type system, wherein the sawn wood is moved in only one direction, from an inlet end of wet wood to an outlet end of dry wood, and the heating chamber, the drying chamber and the cooling chamber include one or more sections controlled together or independently.

14. The drying system according to claim 1, wherein the second air flow is circulated between the heating and cooling chambers through ducts that are arranged on one or both sides of the drying system, side by side, overlaid or in combinations of these locations.

15. The drying system of claim 11, wherein the second air circulation system comprises at least one air flow, which flows between more than one of the sections of the heating chamber, the cooling chamber or a combination thereof, by ducts arranged on one or both sides of the drying system, side by side, overlaid or in combinations of these locations.

16. The drying system according to claim 1, wherein wet vapors leaving the drying chamber are evacuated outside at one or more locations of the second air circulation system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic representation of a progressive drying kiln of the prior art.

(2) FIG. 2 shows a schematic representation of a first embodiment of the drying kiln of the present application.

(3) FIG. 3 shows a schematic representation of a second embodiment of the drying kiln of the present application.

(4) FIG. 4 shows a schematic representation of a third embodiment of the drying kiln of the present application.

DETAILED DESCRIPTION OF THE INVENTION

(5) As can be seen in FIGS. 2 to 4, the invention relates to a wood drying system (100) that allows to take advantage of the heat contained in the hot wood leaving the system to optimally preheat the wood entering the drying kiln, which comprises: a heating chamber (110), a drying chamber (120) and a cooling chamber (130), arranged successively, which may each consist of one or more sections, and a transport path that allows sawn timber transfer (180) through these three chambers; a first (vertical) air circulation system that provides a first flow of hot air (151) inside the drying chamber; and a second (horizontal) air circulation system that provides a second air flow (152), independent of the first flow, which a fluid communication between the heating chamber and the cooling chamber via side chambers or ducts (140) that connect both chambers.

(6) In this way, the drying system of the invention corresponds to a progressive or continuous system, where the wood is moved in single direction, from a wet wood inlet to a dry wood outlet. Thus, the heating chamber is located at the inlet end, followed by the drying chamber and, subsequently, the cooling chamber is located at the outlet end of the drying system.

(7) In optional embodiments of the invention, each of the chambers can include one or several sections, independent or communicated with each other. In addition, the second circulation system can include one or more air flows, which are flows between the one or more sections of the heating and/or cooling chambers by means of ducts arranged on one or both sides of the drying system, side by side, overlaid or in combinations of these possible locations.

(8) The heating and cooling chambers (110, 130) are communicated such to allow the circulation of the secondary air flow (152) of the second circulation system, which is driven by one or more fans located anywhere in said ducts or chambers, either at the entrance or at the exit of the same. In all embodiments there are spaces or ducts (140) that allow the circulation of the secondary air in both directions, as shown in FIGS. 2 to 4, and allow the return of the air heated by the wood that leaves the system to the inlet end of the system.

(9) As shown in FIGS. 1 to 4, the three chambers of the system, of heating (110), drying (120) and cooling (130), are separated from each other by separation walls (190), which allow the operation of both air circulation systems independently. Thus, as shown in FIG. 2, one or more fans are arranged inside the drying chamber for the creation of a first air flow (151) inside the chamber, while the second flow of air flows through two external chambers or ducts (140), located adjacent to the side walls of the drying system, symmetrically on its opposite sides.

(10) In alternative embodiments of the invention, it may be convenient to reduce the space of the first air circulation system in the drying chamber(s). As shown by way of example in FIG. 3, this reduction of space can be carried out by means of an inclined wall (121) extending from the top of the drying chamber, in angle inward the chamber, to the bottom of the same. Preferably, the inclined walls extend approximately from the dropped ceiling or the level reached by the piles of wood (180), to approximately the bottom of the piles, thus separating the inclined vertical flow of the primary air (151) from the horizontal flow of secondary air (152). This configuration has the additional advantage that the primary air flow is improved, since the air speed tends to be kept constant against the wood piles, thereby improving the speed distribution in the heights and reducing the losses of load of circulated air.

(11) In a preferred embodiment of the invention, in order to facilitate the circulation of people in the kiln, a hallway can be provided in the lower part of the external chambers (not shown in the figures), with dimensions suitable for the circulation of people, for example, approximately 400 mm wide.

(12) Another alternative embodiment of the invention is described in FIG. 4, wherein the second air circulation system is arranged such that the secondary air flow (152) circulates through upper part of the kiln, communicating the heating and cooling chambers, above the drying chamber. In this embodiment, the drying chamber comprises in its upper part two inclined walls (122) that create sufficient space for the circulation of the second air flow, allowing fluid communication between the heating and cooling chambers.

(13) Optionally, the embodiments described above can also be used in drying kilns with two paths for vehicles loaded with wood piles. Particularly, in case that an accelerated or high temperature drying process is provided, it may be convenient to use central heaters preferably located in the first drying zone.

(14) Thus, by means of the invention it is possible to improve the deficiencies recognized in the known technologies of the state of the art, since due to the shape and arrangement of the different chambers that constitute the drying system, and especially to the shape and arrangement of the external chambers, it is possible a fluid communication between the heating and cooling chambers, without a considerable increase in energy consumption, allowing to take advantage of the heat contained in the hot wood that leaves the system to optimally preheat the wood that enters the kiln. It is also possible to optimize the conditioning of the wood and ensure that it will have the desired final humidity.

(15) Finally, it should be noted that particular characteristics of the invention, such as dimensions, materials, and specific aspects of the preferred embodiments described above, may vary or be modified depending on the design requirements. Accordingly, the specific embodiments described above are not intended to be limiting, and such variations and/or modifications falls within the spirit and scope of the invention.