JPH06297411A - Wood drying method - Google Patents

Abstract

PURPOSE:To efficiently dry wood in a state of material wood having bark by irradiating wood with microwaves to raise the temp. and pressure in wood and drying the irradiated wood in a drying chamber. CONSTITUTION:The wood in a wood storage chamber is supplied to a pretreatment chamber 2 one at a time. The pretreatment chamber 2 is equipped with a microwave heating device and the wood is rradiated with microwaves for 3-15min. By this irradiation, the interior of the wood is raised in temp. and pressure and the pressure in the wood becomes low toward the cut end. When this pressure gradient is generated, the water channels reaching the cut end are formed in the wood. The pretreated wood is fed into a drying chamber 4 equipped with a hot air generator, a temp. and humidity control system or the like and the moisture in the wood moves to the cut end through the water channels during hot air drying to be discharged to the outside through the cut end.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drying method for drying log (raw wood) with bark such as cedar and cypress.

[0002]

2. Description of the Related Art Generally, when wood is used as a lumber product such as a pillar without being dried, cracks or warpage of the product may occur due to a difference in water content between the sapwood and the core material or growth stress. Alternatively, a problem such as twisting occurs. For this reason, it is necessary to dry the wood to a certain moisture content and then finish and grind it into a product.In order to dry the wood, for example, it is naturally dried by stacking the wood outdoors. Alternatively, it is stored in a drying chamber and dried with hot air.

However, conventionally, it is almost impossible to dry wood with a bark having a bark as it is. Therefore, the bark is usually peeled off, and the back is split. It was releasing water. This is because the water inside the wood does not pass through the bark and is not discharged from the side (circumferential surface of the log), and even when the bark is peeled off, there is winter (a hard part of the annual ring). The reason is that the water inside cannot be released from the side unless the back is split.

[0004]

As described above, in the past, since it was not possible to dry the raw wood after cutting it out, it is necessary to dry it after undergoing steps such as rough grinding for bark stripping and splitting of the back. However, this requires time and labor for this, as well as various equipment and devices. Specifically, transportation of wood between each process and transportation equipment such as vehicles required for this, or chemicals (preservatives, crack preventives, etc.) to prevent mold or cracks during the drying process, and It requires a great deal of equipment investment such as the time and labor for applying this, as well as the rough grinding equipment and its installation space, and the personnel involved therewith.

Further, there is a problem in that the wood cannot be used effectively because the bark is stripped or the back is split in order to perform the drying, and therefore the product yield is not good.

The present invention has been made in view of these problems of the related art, and can be efficiently dried with the raw wood as it is,
Accordingly, it is an object of the present invention to provide a method for drying wood that eliminates steps such as rough sawing or back splitting to reduce costs and does not require extra flesh for finishing sawing and that can improve product yield. And

[0007]

In order to solve the above-mentioned conventional problems, the present invention performs pretreatment for irradiating a microwave with microwaves to increase the temperature and pressure inside the wood, and then It is characterized by being dried in a drying chamber in which temperature and humidity can be controlled.

[0008]

According to the above construction, when the wood is irradiated with microwaves, the water molecules inside the wood are activated due to the characteristics of the microwaves, which in turn raises the temperature and pressure inside the wood. When the temperature and pressure inside the wood rises, the cell valve of the wood opens, so the water inside the wood flows out of the cell valve and merges, and the merged water merges further toward the mouth. After all, inside the wood, after all,
A waterway is formed from the center to the mouth of the tree. Then, after performing such a pretreatment, when the wood is heated by blowing hot air or the like in the drying chamber where the temperature and humidity can be controlled, the water content inside easily moves toward the wood mouth and passes through the wood mouth. It is discharged to the outside.

Further, when the microwave irradiation is strongly applied to the central portion of the wood, the central portion is heated most and a temperature gradient in which the temperature becomes lower toward the mouth end is generated inside the wood. Since a pressure gradient with a higher pressure is generated, the formation of the water channel is further promoted, which is more preferable.

As described above, the temperature and pressure inside the wood are increased to form a water channel for guiding the water inside the wood to the wood mouth, and then drying is performed. It is not necessary to carry out a treatment such as bark stripping or splitting of the back, and it is possible to efficiently dry even a bark-attached raw tree.

[0011]

Embodiments of the present invention will now be described with reference to FIGS. FIG. 1 shows a schematic configuration of a drying device D used in the drying method of this example. This drying device D
As shown in FIGS. 1 and 2, the wood storage chamber 1 for storing the wood W, and the wood W carried out from the wood storage chamber 1.
And a drying chamber for blowing a large amount of wood W at one time by blowing hot air onto the wood W that has been subjected to a predetermined pretreatment in the pretreatment chamber 2. 4 and.

A large number of woods W as materials to be dried are housed in the tree storage chamber 1 (not shown in the drawing), and a transfer conveyor 5 (not shown) provided in the tree storage chamber 1 conveys the woods W one by one. And is supplied to the pretreatment chamber 2. The wood W is a state in which the raw wood is simply cut into a certain length, and is stored without any processing such as bark stripping or back splitting.

The inside of the tree storage chamber 1 and the inside of a drying chamber 4 which will be described later are connected by a duct 7 so that the hot air in the drying chamber 4 also flows into the tree storing chamber 1. As a result, the inside of the wood storage chamber 1 is kept at a constant temperature, and the stored wood W is preheated.

The transfer conveyor 5 is arranged from the tree storage chamber 1 to the inside of the drying chamber 4, and the pretreatment chamber 2 is installed in the middle of the transfer conveyor 5.

The pretreatment chamber 2 is provided for performing the pretreatment described below on the wood W prior to the drying in the drying chamber 4, and for this reason, a predetermined microwave heating device is provided in the pretreatment chamber 2. (Not shown) is provided. That is, this pretreatment means irradiating the wood W with microwaves to bring the inside into a certain state described later. This pretreatment will be described in more detail.

The microwave heating device, which has been generally used conventionally, will not be described in detail because it is sufficient. However, the microwave heating device is composed of a microwave oscillator, a load circuit, a controller for controlling the operation of the load circuit, and the like. There is.

The wood W, which has been subjected to a predetermined pretreatment described later in the pretreatment chamber 2 thus constructed, is carried into the drying chamber 4 by the conveyor 5. A stacking device 3 is installed near the entrance of the drying chamber 4, and the wood W carried in by the stacking device 3 is sequentially stacked on the stocker pallet P. The stocker pallet P filled with wood W is sequentially dried in the drying room 4.
It is designed to be moved to the inner part of the.

The drying chamber 4 is of a type that has been generally used in the past and is capable of drying a large amount of wood W at one time by blowing hot air onto the wood W. It is equipped with temperature and humidity control system. As shown by the one-dot chain line in FIG. 1, this drying chamber may be expanded in the width direction (right direction in the drawing) so that a plurality of rows of stocker pallets P can be packed at one time.

The wood W dried in the drying chamber 4 is sorted into the wood W dried up to a predetermined water content and the wood W not dried by measuring its weight, and the wood W dried up to the predetermined water content. Is taken out of the drying device D as the drying is completed, and the wood W which is not so is returned to the tree storage chamber 1 and dried again by the above-mentioned steps.

Now, the drying device D constructed as described above
According to the above, the wood W is irradiated with microwaves in the pretreatment chamber 2 as a pretreatment before drying. This pretreatment utilizes the characteristics of microwaves. Specifically, when the wood W containing water inside is irradiated with microwaves, water molecules are activated and collide with each other. It utilizes the phenomenon that heat is generated.

Further, it is more effective to irradiate the microwave with the central portion of the wood W as the center, and it is more effective for the thick wood and the wood with a large amount of water, whereby the water inside the wood W is heated. As a result, the wood W is gradually heated so as to have a temperature gradient as shown in FIG. That is, the temperature increases as the water content in the central portion in the longitudinal direction of the wood W increases (about 100 ° C.), and the water content near the mouth end of the wood W has a lower temperature (about 7 ° C.) than the central portion.
It is heated to about 0 ° C. Thus, the water inside the wood W is heated in a state in which a temperature gradient is generated, so that the pressure (water pressure) inside the wood W rises, and this pressure rise also produces a gradient commensurate with the temperature gradient. . That is, the pressure near the mouth of the wood W becomes higher than the atmospheric pressure, and the internal pressure becomes higher toward the central portion.

The microwave irradiation time is about 3 to 15 minutes, which causes the inside of the wood W to have high temperature and high pressure.
In addition, a pressure gradient becomes low as it reaches the mouth. When this pressure gradient is generated, a water channel leading to the wood mouth is formed inside the wood W. That is, when the internal pressure (water pressure) rises, the water that had been scattered up to that point breaks the cell membranes and merges, eventually forming a number of water channels that pass between cells. Formed towards the mouth of the tree.

After such pretreatment, the wood W is carried into the drying chamber 4 and blown with hot air, and left in this state for several days. During the drying with hot air, the water content inside the wood W moves through the water channel toward the wood mouth and is discharged to the outside through the wood mouth.

As described above, according to the drying method of this embodiment, the wood W is subjected to the pretreatment utilizing the characteristics of microwaves prior to the actual drying. In Fig. 2, the wood W is irradiated with microwaves to increase the temperature and pressure inside the wood W, whereby the cell valve of the wood W is opened and a water channel leading to the wood mouth is formed.

Then, in the actual drying process performed in the drying chamber 4, the wood in which the water passage leading to the wood mouth is formed is blown with hot air under the control of temperature and humidity so that the water content in the wood is directed toward the wood mouth. Then, it is discharged to the outside through this wood mouth and dried. Therefore, it becomes possible to efficiently perform the drying even in the state of the raw wood with the bark, so that it is not necessary to perform the work of stripping the bark or splitting the back, which has been performed prior to the drying. The drying process of W can be greatly simplified, and the cost can be greatly reduced.

Further, since the raw wood can be dried as it is without stripping the bark or splitting the back, the wood W can be effectively utilized without any exhaustion, and therefore the yield of lumber products can be improved. Further, it is possible to reduce a worker or equipment and a space therefor which have conventionally been required for bark stripping or back splitting work,
Also in this respect, the cost can be increased.

Furthermore, since the raw wood can be dried and stored as it is, it is not necessary to apply chemicals such as preservatives, the labor and the cost of chemicals can be saved, and the raw wood can be dried as it is. Since it can be stored in storage, it is possible to adjust the shipment, and it becomes possible to supply timber at a stable price.

Further, since the wood can be transported in a state where the raw wood is dried and the weight thereof is reduced to about half, the transportation cost can be reduced.

[0029]

According to the present invention, since the wood can be dried as it is as a raw wood, there is no need to remove the bark or split the back as in the prior art, and therefore the wood drying process can be greatly simplified to reduce the cost. In addition, since it can be dried and transported in a state where its weight is almost halved, the transportation cost can be reduced.

[Brief description of drawings]

FIG. 1 is an overall plan view of a drying device according to an embodiment of the present invention.

FIG. 2 is a partially transparent side view of the drying device.

FIG. 3 is a perspective view of a raw tree cut into a certain length.

FIG. 4 is a graph showing a temperature gradient inside wood.

[Explanation of symbols]

 D ... Drying device W ... Wood 1 ... Storage room 2 ... Pretreatment room 3 ... Stacking room 4 ... Drying room 5 ... Conveyor 7 ... Duct

Claims (1)

[Claims] 1. The wood is pre-treated by irradiating the wood with microwaves to raise the temperature and pressure inside the wood, and then the wood is dried in a drying chamber where the temperature and humidity can be controlled. How to dry wood.