JPH06257946A - Method and device for drying timber - Google Patents

Abstract

PURPOSE:To provide a drying method to decrease a finish water content uniformly to 10% and less, and to execute drying without generating a deformation or a crack caused by an unevenness of drying of a conifer such as a Japanese ceder or a pine efficiently in a short period, and a drying device wherein a drying process can be executed under a heat recovery condition of high efficiency, using steam generated from a timber effectively, and a cost decrease, a resources saving and the like can be realized. CONSTITUTION:In a drying room 2, a timber 1 is dried at a condition that a dry-bulb temperature is 100 deg.C to 150 deg.C and a wet-bulb temperature is 90 deg.C and more. In a drying device having a heat exchanger 10 and a circulation fan 6 in a drying room 2 accommodating a timber 1, the drying device is provided with a steam extracting pipeline 11 extracting steam generating from the timber 1 in a drying room 2 to outside of the drying room 2, a compressor 12 compressing extracted steam, and a heat pump type heat recovery device having a steam supplying pipe supplying the compressed heating steam to a heat exchanger 10 as a heat medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial drying technique for building pillars and boards, and more particularly to a method and apparatus for drying wood suitable for drying softwood.

[0002]

2. Description of the Related Art As is well known, in order to apply wood to building components, furniture, etc., it is necessary to dry the water content to a certain value or less to prevent deformation and cracking due to subsequent shrinkage. Such wood has been used as a drying material for a long period of several months or more due to natural drying in the old days, but in recent years when the rationalization of construction processing has advanced, artificial drying is performed for a short period of time.

Artificial drying techniques of wood that have been developed and used widely include, for example, a direct heating system in which smoke and combustion gas are supplied to a wood housed in a drying chamber to heat it, and a heater installed in the drying chamber is steamed.・ Indirect heating method that heats the drying chamber by supplying heat source such as hot water and electricity, natural or forced circulation method by circulating air, and other special drying methods such as high frequency drying, chemical drying, organic compound drying, vacuum drying, etc. There is. A dehumidifying and drying method has also been developed, but it is rarely used because the drying temperature is low and it takes a long time to dry, and the dehumidifying device frequently causes troubles.

By the way, in the above-mentioned conventional technique, it is general that the drying temperature by hot air, combustion gas, etc. is set in the range of 40 to 90 ° C., and the steam is discharged to the outside of the drying chamber. This is mainly based on a technique for efficiently drying hardwood without causing deformation or cracking due to uneven drying, and it takes several weeks or more to dry the softwood. For drying logs such as logs, set the drying temperature to 1
A technique of setting the temperature to 50 to 200 ° C. and condensing and condensing the steam generated from wood to the outside (JP-A-63-637).
No. 6, etc.) or a technique of drying at a high temperature of 180 to 200 ° C. and a steam atmosphere with heated steam (Japanese Patent Laid-Open No. 1-11).
No. 4686, etc.) has been developed, but if the drying temperature is too high and sawn timber, defects such as bending, cracking and surface alteration are likely to occur.

In addition, in order to solve problems such as surface alteration and cracking during drying in hot air, vacuum, combustion gas atmosphere, etc., a technique has been developed in which the humidity of the air circulating in the drying chamber is increased to perform drying. (JP-A-62-41)
No. 573). As a result, it became possible to dry for a relatively short period of time without any problems such as surface alteration or cracking. However, even in the case of this technique, the temperature in the drying chamber is 25 to 70.
The temperature is in the range of 0 ° C, and the period required for drying the softwood material still takes several weeks or longer, and the drying rate is not necessarily greatly improved.

[0006]

The large amount of cedar and pine trees planted in Japan in the past is currently growing to a size usable as a building material. Although these domestic softwoods are cheaper than imported timbers, it is predicted that if they cannot be dried in a short period of time, they will not be able to cope with future increase in demand. There is an urgent need for technology development. In this case, with regard to the drying of softwood materials for construction, it is necessary to take into consideration problems such as finishing accuracy, cracking due to drying after construction, shrinkage, etc. Among them, it is difficult to dry due to conditions such as large cross-sectional shape and core material, damage is likely to occur, and it is extremely difficult to uniformly dry to a low water content range of 10% or less due to large difference in material It is said that Further, with regard to pine such as larch and red pine, if the drying is insufficient, there is also a problem that the resin possessed flows out after use. Further, the above-mentioned conventional technique has a problem that the drying cost is high because the drying period is long and a large amount of heat source is required.

The present invention has been made in consideration of such various circumstances. A first object of the present invention is to efficiently and efficiently grind coniferous sawed wood such as cedar and pine in a short period of time and to prevent deformation due to uneven drying. It is an object of the present invention to provide a method for drying wood, which can be dried without causing cracks and in which the finished water content can be uniformly reduced to 10% or less.

The second purpose is to utilize the steam generated by the wood effectively, and the drying step by the above method can be performed under the highly efficient heat recovery, and the cost reduction and resource saving can be achieved. To provide a drying device.

[0009]

[Means and Actions for Solving the Problems] In the past, artificial forced drying in Japan has been mainly made of hardwood, and there is a particular demand for artificial drying of pillars and boards of softwood such as cedar and pine. It wasn't strong. Therefore, based on our experience so far, drying of softwood pillars and planks is not particularly distinguished from drying of hardwood, and the drying temperature at which good results without deformation or cracking of hardwood is obtained. The same applies to softwood materials, and an upper limit of about 80 ° C was set.

However, according to the study by the inventors, the influence of the relative humidity on the water content of wood is stronger than the influence of temperature. Therefore, by properly controlling the humidity as well as the temperature in the drying chamber, it is possible to grind the softwood. It has been found that the material can be dried in a good condition in a short period of time as compared with the conventional method. That is, unlike hardwoods, softwoods allow the interior of wood to be dried in a short period of time while preventing overdrying of the surface by setting the relative humidity above a certain value even when the temperature exceeds 80 ° C. In that case, it was confirmed that there was a region of temperature and humidity where there was no deformation such as warping or dropping, and no cracks inside or outside the wood. The specific temperature and humidity range is 20-25% in addition to 70-75% free water contained in undried wood.
It is considered that even the bound water (water content in the cell wall) can be efficiently scattered to the outside.

The present invention has been made on the basis of such findings, and the method for drying wood according to the invention of claim 1 has a dry-bulb temperature of 100 to 150 ° C. and a wet-bulb temperature of 90 ° C. in a drying chamber. It is characterized by being dried under the above conditions.

In the present invention, the dry-bulb temperature is 100 to 15
The reason for setting the temperature to 0 ° C. is that if the temperature is lower than 100 ° C., the desired drying rate cannot be obtained, and if the temperature exceeds 150 ° C., deformation or cracking is likely to occur.

The reason why the wet-bulb temperature is 90 ° C. or higher is that if the temperature is lower than this, the equilibrium water content is lowered and cracks are likely to occur. The desirable wet bulb temperature is 100 ° C or higher.

According to the method of the present invention, the drying time can be shortened. That is, it is possible to reduce the time required for drying wood, which conventionally required drying time of about 3 weeks, to about 1/7 of 3 days. Further, it is possible to eliminate the occurrence of uneven drying due to the variation in material, and it is possible to obtain wood of good quality.
Further, the finished water content can be reduced to 10% or less, which is impossible with the conventional drying method. In that case, the water content can be made uniform, the material strength can be maintained high, and the material can be dried in a short time without damage.

According to a second aspect of the present invention, there is provided a drying apparatus for wood, wherein a heat exchanger and a circulation fan are provided in a drying chamber for containing the wood, and the heat of the heat exchanger and the steam atmosphere generated from the wood are generated. In a wood drying device for drying wood, a steam extraction pipe for extracting steam generated from wood in the drying chamber to the outside of the drying chamber, and a compressor for compressing the steam extracted by the steam extraction pipe, A heat pump type heat recovery device having a steam supply pipe for supplying the superheated steam compressed by the compressor to the heat exchanger as a heat medium is provided.

According to the present invention, by adopting the heat pump system, the heat consumed for evaporating the moisture of the wood can be recovered and reused, and the heat energy is not discharged to the outside of the drying chamber. Therefore, as compared with the conventional drying device, the surrounding environment is not polluted, and the heat recovery system is highly efficient with no waste of energy consumption, and the drying cost can be significantly reduced. Therefore, it can greatly contribute to the drying of wood in the future.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, the drying device will be described with reference to FIG.

As shown in FIG. 1, the drying apparatus of this embodiment has the following structure.
There is a drying container 3 for accommodating the wood 1 in a drying chamber 2 inside the drying chamber 2, and an upper part of the drying container 3 is provided with a regulating valve 5a for supplying steam from a steam generator 4 to the drying chamber 2. A steam duct 5, a circulation fan 6, and a pair of ventilation ducts 8 with a damper 7 which are arranged in front of and behind the circulation fan 6 to communicate the inside and outside of the drying chamber 2 are provided.

A heat pump type heat recovery device 9 is provided in association with the drying container 3. This heat pump type heat recovery device 9 includes a heat exchanger 1 installed in a drying chamber 2.
0, a steam extraction pipe 11 for extracting steam generated from the wood 1 in the drying chamber 2 to the outside of the drying chamber, and this steam extraction pipe 11
And a compressor 12 for compressing the vapor extracted in 1.
The steam supply pipe 13 supplies the superheated steam compressed in 2 to the heat exchanger 10 as a heat medium. A drain pipe 14 is led out from the heat exchanger 10.

With such a structure, the heating, drying and cooling steps can be sequentially carried out as follows.

In the heating step, the steam generated by the steam generator 4 is supplied to the drying chamber 2 through the steam pipe 5, and the circulation fan 6 circulates the steam in the drying chamber 2 to heat the wood 1 with steam. . In this case, the air in the drying chamber 2 is discharged to the outside via the ventilation duct 8.

In the drying step, the heat pump type heat recovery device 9 is used. That is, since the wood 1 is heated by the steam previously supplied in the heating step to evaporate the water content, the generated steam is extracted from the drying chamber 2 into the steam extraction pipe 1
1 to send to the compressor 12 of the heat pump heat recovery device 9. By driving the compressor 12, the vapor introduced from the drying chamber 2 is compressed into superheated vapor, and the vapor supply pipe 13
And is sent to the heat exchanger 10 in the drying chamber 2 via the to function as a heat medium. As a result, heating can be performed by the heat exchanger 10 using only the steam generated from the wood 1, and drying can be performed in a wet state by the steam generated from the wood 1 itself filling the drying chamber 2. The steam used for work in the heat exchanger 10 becomes drain water, and the drain pipe 14
It is discharged to the outside via. The energy required at this time is only the electric power for operating the compressor 12.

In the cooling step, when the wood 1 is dried to a predetermined moisture content, the damper 7 is opened, the outside air is taken into the drying chamber 2 through the ventilation duct 8 and the circulation fan 6 is reversed.

According to the drying apparatus of this embodiment, by adopting the heat pump system, the heat consumed for evaporating the moisture of the wood 1 can be recovered and reused, and the heat energy is discharged to the outside of the drying chamber 2. Never. Therefore, as compared with the conventional drying device, the surrounding environment is not polluted, and the heat recovery system is highly efficient with no waste of energy consumption, and the drying cost can be significantly reduced. Furthermore, the heating, drying, and cooling processes can be switched easily, smoothly, and reliably.

The heating step can be carried out by supplying steam to the heat exchanger 10 from the external steam generator 4, or may be carried out by using other means not shown. Further, the heating step and the drying step may be performed by arbitrarily combining the steam generator 4 and the heat pump heat recovery device 9.

Next, a method of drying wood using the above apparatus will be described.

Example 1 (FIGS. 2 and 3) In this example, a cedar cored pillar material of 105 mm square and 4 m long was heated according to the time chart shown in FIG.
It dried by performing a drying process and a cooling process.

In the heating step, the pillar material was heated by steam heating from 30 ° C. to 110 ° C. for 6 hours at a dry-bulb temperature. The wet bulb temperature at this time increased from 28 ° C to 100 ° C.

In the drying process, the dry-bulb temperature is kept at 110 ° C. for 15 hours, the temperature is raised to 120 ° C. over 1 hour, the state is kept for 15 hours, and the drying is performed for 1 hour. The temperature was raised to 130 ° C., and the state was maintained for further drying for 15 hours. The wet bulb temperature during this period is 100 ° C.

In the cooling step, the dry-bulb temperature is from 130 ° C to 10 ° C.
The temperature was lowered to 5 ° C over 2 hours, and then further lowered to 35 ° C over 8 hours. The wet-bulb temperature dropped from 100 ° C to 28 ° C during the 8 hours of this final cooling stage.

As a result of the above heating, drying and cooling steps for 63 hours, the water content of the column material decreased to 10% or less as shown in FIG. That is, FIG. 3 is a graph showing the water gradient of the pillar material in the initial stage (characteristic line A), in the middle (same B) and in the final stage (same C) of the above process, in which the horizontal axis indicates the short cross section of the pillar material.
The figures are divided into equal parts (No1 and No21 indicate the outer end side, and No11 indicates the core side), and the vertical axis indicates the water content.

As shown by the curve A in FIG. 3, the column member, which had a water content of 30 to 75% in the initial raw material and a high water content on the core side, was dried. As shown by the curve C, the water content was about 5 to 8%, and the water content on the core side was lower than that on the outer end side.

Further, the dried pillar material was free from surface cracks, edge cracks, and bending, and a good product was obtained.

Example 2 (FIG. 4) In this example, a plate material of red pine having a thickness of 55 mm, a width of 200 mm and a length of 4 m was dried by performing a heating step, a drying step and a cooling step according to the time chart shown in FIG. did.

In the heating step, the pillar material was heated by steam heating from 30 ° C. to 100 ° C. at a dry bulb temperature for 4.5 hours. The wet bulb temperature at this time increased from 28 ° C to 100 ° C. In the drying process, keep the dry-bulb temperature at 100 ° C
After drying for an hour, the temperature was raised to a dry-bulb temperature of 110 ° C. over 0.5 hour, the state was maintained and dried for 6 hours,
The temperature was raised to 120 ° C. over 0.5 hours, and the state was maintained for further drying for 6 hours. The wet bulb temperature during this period is 100 ° C.

In the cooling step, the dry-bulb temperature is 120 ° C. to 10 ° C.
The temperature was lowered to 0 ° C. over 0.5 hours, and then further lowered to 35 ° C. over 4 hours. The wet bulb temperature dropped from 100 ° C to 28 ° C during 4.5 hours of this final cooling stage.

As a result of the above heating / drying / cooling process for 26 hours, the water content of the plate material decreased uniformly to 10% or less as in Example 1, and the dry plate material had surface cracks, small cracks, and bends. At all, a good product was obtained.

Example 3 (FIG. 5) In this example, as in Example 2, the thickness is 55 mm and the width is 200 mm.
Plates of Japanese red pine (mm, 4 m long) were dried by performing a heating step, a drying step and a cooling step according to the time chart shown in FIG.

In the heating step, the pillar material was heated by steam heating from 30 ° C. to 100 ° C. at a dry-bulb temperature for 4.5 hours. The wet bulb temperature at this time increased from 28 ° C to 100 ° C. In the drying process, keep the dry-bulb temperature at 100 ° C
It was dried for 7.5 hours. During this time, the wet-bulb temperature was lowered to 97 ° C. over 0.5 hours after the initial drying for 4 hours, and then the same state was further maintained and dried for 14 hours. The temperature was lowered to 95 ° C. and 90 ° C. sequentially.

In the cooling step, the dry-bulb temperature is 100 ° C. to 95 ° C.
Decrease the temperature to ℃ over 0.5 hour, then 4
The temperature was lowered to 35 ° C over time. The wet bulb temperature dropped from 90 ° C to 28 ° C during 4.5 hours of this final cooling stage.

As a result of the above heating / drying / cooling process for 56.5 hours, the water content of the plate material decreased uniformly to 10% or less as in Example 2, and the dry plate material had surface cracks and small cracks. A good product was obtained without any bending.

Other Examples In addition to the above examples, various softwoods were dried in a drying chamber under conditions of a dry bulb temperature of 100 to 150 ° C. and a wet bulb temperature of 90 ° C. or higher. As a result, in the range of 20 to 70 hours, good drying results were obtained, which were substantially the same as those in the above-mentioned examples.

[0043]

As described above in detail, according to the method for drying wood according to the present invention, the drying time can be shortened to about 1/7 of the conventional one, and the occurrence of the unevenness of drying due to the variation of the material can be eliminated. , Good quality wood is obtained. Further, the finished water content can be reduced to 10% or less, which has been impossible in the past, and the water content can be made uniform and the strength can be improved.

Further, according to the wood drying apparatus of the present invention, by adopting the heat pump system, the heat consumed for evaporating the moisture of the wood can be recovered and reused, and the heat energy is discharged to the outside of the drying room. There is nothing to do. Therefore,
Compared with the conventional drying device, the surrounding environment is not polluted, and the heat recovery system is highly efficient with no waste of energy consumption, and the drying cost can be significantly reduced. Therefore, it can greatly contribute to the drying of wood in the future.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a wood drying apparatus according to the present invention.

FIG. 2 is a time chart showing Example 1 of the method for drying wood according to the present invention.

FIG. 3 is a diagram showing characteristics of the same embodiment.

FIG. 4 is a time chart showing a second embodiment of the method for drying wood according to the present invention.

FIG. 5 is a time chart showing Example 3 of the method for drying wood according to the present invention.

[Explanation of symbols]

 1 Wood 2 Drying Room 6 Circulation Fan 9 Heat Pump Type Heat Recovery Device 10 Heat Exchanger 11 Steam Extraction Pipe 12 Compressor 13 Steam Supply Pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kashihara Regular No. 19-7 Senjunaka-cho, Adachi-ku, Tokyo Within Sumikin Hill Debrand Co., Ltd. (72) Inventor Takeshi Oyama 2-30-2 Kanda-Jimbocho, Chiyoda-ku, Tokyo TEPCO Ltd. Development Laboratory (72) Inventor Takeshi Kobayashi 2-32 Kanda Jinbocho, Chiyoda-ku, Tokyo Tokyo Electric Power Company Development Laboratory (72) Inventor Koichi Sato 2-2, Kanda Jimbocho, Chiyoda-ku, Tokyo No. 30 Tokyo Electric Power Company, Inc.

Claims (2)

[Claims] 1. Dry-bulb temperature 100 to 1 in a drying chamber for wood.
A method for drying wood, which comprises drying under conditions of 50 ° C. and a wet bulb temperature of 90 ° C. or higher. 2. A wood drying apparatus which is provided with a heat exchanger and a circulation fan in a drying chamber for storing wood, and which dries the wood under heating of the heat exchanger and a steam atmosphere generated from the wood. The steam extraction pipe for extracting the steam generated from the wood in the drying chamber to the outside of the drying chamber, the compressor for compressing the steam extracted by the steam extraction pipe, and the superheated steam compressed by the compressor for the heat exchanger. A wood drying device comprising a heat pump type heat recovery device having a steam supply pipe for supplying as a heat medium to the.