JPH085237A - Method and device for drying wooden material - Google Patents

Abstract

PURPOSE:To enable log drying while preventing a crack from being produced in the log by a method wherein a drying chamber is applied with a drying condition in which a drying rate at a surface layer of the log and another drying rate at a central layer of the log (a reduction in moisture content) are balanced or the drying rate at the central layer of the log is caused to approach to that of the surface layer as near as possible. CONSTITUTION:A primary drying is carried out such that only raw vapor is fed into a drying chamber A having a discharging device 5 for keeping its inner pressure at normal pressure or a state near normal pressure to heat up or increase a temperature from normal temperature to 90 deg.C or more to 100 deg.C and an entire inner region ranging from the surface layer of a wooden material (logs 1 with barks) to the central layer is heat treated up to 90 deg.C or more to 100 deg.C. Then, a secondary drying is performed such that an inner region in the drying chamber is heated up at once by a heater 9 to 100 deg.C or more to 200 deg.C to boil up moisture content in the wooden material and the material is heat treated up to a high temperature of a fiber saturation point where the moisture content reaches a target moisture rate. Lastly, a third drying operation is carried out such that a dry ball temperature and a wet ball temperature within the drying chamber A are changed in response to a drying state of the wooden material and a low temperature and low humidity processing is carried out for the target moisture content in response to the condition above and then it is possible to prevent a crack from being generated and to dry the wooden material up to the target moisture content rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drying wood and a drying apparatus therefor, and more specifically, it stores raw wood such as lumber processed into logs, corners and plates in a drying chamber, The present invention relates to a drying method of artificially drying by raising the temperature to an appropriate drying temperature.

[0002]

2. Description of the Related Art Conventionally known artificial drying of wood is generally performed by heating and raising the temperature of a drying chamber containing raw wood to a drying temperature of about 40 to 90 ° C. It took about 20 days to dry wood with a moisture content of 140% to a target moisture content of 17% (finished moisture content). Therefore, in the conventional method, the number of days until the drying is completed is long and the production efficiency is poor. Moreover, since the drying mainly consists of evaporation of water from the wood surface layer, only the surface layer is dried and the drying does not reach the central layer (center of the xylem). Cannot be dried uniformly. That is, the target moisture content could not be made uniform, and complete drying, which greatly affects various strengths of wood, could not be expected. Also, since the drying starts from the surface layer side where water evaporates, cracks occur in the surface layer due to the anisotropy of shrinkage due to the drying, and there are few parts that can actually be used as building materials and joinery materials That is, the utility value, which is said to be large, is greatly reduced. In any case, with conventional drying technology, wood drying that prevented cracking,
In particular, it was considered impossible to dry hearty logs and hearty lumber.

By the way, in the case of the core-bearing logs and the core-bearing lumber, there is a tendency that cracks occur from the surface layer toward the center layer during artificial drying. More specifically, the shrinkage in each direction due to drying (decrease in water content) is greater in the circumferential direction along the surface layer (tangential direction with annual rings) than in the radial direction from the surface layer to the central layer, so the central layer side If the surface layer is dried earlier than this, the growth of the annual ring layer is rougher than the central layer side, and the surface layer with a high water content tends to crack, which tends to gradually occur in the radial direction toward the central layer. Because.

[0004]

SUMMARY OF THE INVENTION The inventors of the present invention have conducted various researches based on their many years of experience and achievements in view of such conventional circumstances. As a result, when artificially drying wood, the surface layer side and the center layer side are In order to prevent cracking, it is most important to create a drying condition (drying atmosphere) in the drying chamber that equilibrates the drying rate (reduction rate of water content) with In order to realize it, various researches have been carried out repeatedly to prevent the generation of cracks and enable complete drying up to the central layer, and at the same time, we have developed an epoch-making drying method that can be implemented at low cost. It is an object to provide a method and an apparatus thereof.

[0005]

The technical means taken by the present invention to achieve the above object is to store a large number of timbers in a multi-tiered manner at intervals with heat passing between the timbers. , Only the raw steam is sent to a drying chamber that has an exhaust device that maintains the internal pressure at or near atmospheric pressure, and the room is heated from room temperature to 90 ° C to 100 ° C and heated to raise the temperature from the surface layer of the wood to the central layer. The primary drying of wood by heat-treating the entire internal area up to 90 to 100 ℃ above 90
After being heated to ℃ or more to 100 ℃, the temperature of the room is suddenly heated to 100 ℃ to 200 ℃ by the heater and the water inside the wood is boiled to reach the target water content. Secondary drying to be processed, and when the water content falls to the fiber saturation point, the temperature conditions such as the dry-bulb temperature and the wet-bulb temperature in the room are changed. This is the drying method.

Further, when the wood is dried to the target moisture content by the third drying, the temperature condition of only the wet-bulb temperature in the room is changed, and the drying stress and moisture gradient remaining in the wood are removed by the condition. This is a drying method whose main point is to carry out treatment.

[0007] It is composed of a drying chamber of a substantially rectangular plane shape having a door for wood closed on one side by a door, and a boiler chamber installed on the side of this drying chamber. Above the inside of the drying chamber, from the boiler chamber. A steaming pipe that is piped to feed live steam into the room to heat and raise the temperature, and a heater to heat and raise the room by heat exchange are installed. An exhaust device that allows natural exhaust when the temperature rises to maintain the internal pressure in the room at or near atmospheric pressure, and a circulation device that circulates the heat throughout the room during the heating / heating by the vaporizing pipe and heater. In addition, the drying device is characterized by the fact that a truck with multiple timbers stacked in multiple stages is loaded into the drying chamber on the floor of the drying chamber, and a traveling rail is installed to carry it out after the drying is completed. .

Further, the circulation device has a heat-resistant seal member at the rim of which a propeller shaft is horizontally supported via a heat-resistant bearing at the lower end of a support member hung from the ceiling and one end of which is opened to the side wall. The shaft is projected through the through hole to the outside of the drying chamber, and a motor is installed outside the side wall on the axis of the shaft. The motor is connected to the protruding one end side of the shaft, and the other shaft of the shaft inside the drying chamber is connected to the motor. It is a drying device whose main point is to install a propeller fan at the end.

Further, the exhaust device is a drying device characterized in that an opening / closing damper that is automatically released in one direction by being pushed by the internal pressure in the drying chamber is provided in an exhaust passage opened in a proper place in the drying chamber. is there.

[0010]

[Operation] Therefore, according to the above-mentioned claim 1 of the present invention, the drying chamber is kept only at room temperature from room temperature to 90 ° C or higher to 1 ° C or higher.
By heating and raising the temperature to 00 ° C. and maintaining the temperature, the above heat is spread evenly over the wood that is stacked and accommodated in a multi-stage manner at intervals of heat passage to heat each wood. On this occasion,
The indoor humidity gradually rises as the temperature rises and reaches 100% when the temperature reaches 90 ° C to 100 ° C. Therefore, the drying of the surface layer of wood is suppressed by the 100% humidity atmosphere. The heat is gradually transferred to the central layer of wood. As a result, the drying of the surface layer of the wood is suppressed, and the entire area of the interior is uniformly and equilibrium heated to a temperature of 90 ° C to 100 ° C immediately before the boiling of water. That is, primary drying is performed in which the entire inner region from the surface layer to the central layer is heated uniformly and in equilibrium according to a so-called drying schedule that balances temperature and humidity by combining temperature and humidity.

After the wood is sufficiently heated to 90 ° C to 100 ° C, the interior of the room is blown by a heater to 100 ° C to 2 ° C.
By heating and raising the temperature to 00 ° C and maintaining it, the inside of the wood is heated at a temperature of 100 ° C to 200 ° C to boil the water inside the wood all at once, and at the same time, the internal pressure increased to blow out from both ends of the wood. Then, secondary drying is performed to dry to the fiber saturation point. At this time, the internal pressure in the drying chamber due to the rise in the indoor temperature is exhausted to the outside of the drying chamber from the exhaust device, so that the chamber is maintained at a normal pressure or a state close to it, so that the moisture inside the boiled wood is It blows out from the mouth at once. Thereby, it is possible to equilibrate the drying rate (rate of decrease in water content) between the surface layer side and the center layer side, or to bring the drying rate on the center layer side to the surface layer side as close as possible to uniformly and equilibriumly dry the entire inner region. . Then, when the water content reaches the fiber saturation point, the dry-bulb temperature in the room,
By changing the drying conditions such as the wet-bulb temperature according to the drying condition of the wood and maintaining the drying conditions for a predetermined time, the third drying is performed to dry the water content inside the wood to the target water content.

According to the second aspect, when the wood is dried to the target water content, the drying condition of only the wet bulb temperature in the third drying is changed and the drying is performed for maintaining the condition for a predetermined time. As a result, the drying stress and moisture gradient remaining inside the wood dried to the target water content (finished water content) are removed.

According to a third aspect of the present invention, a trolley in which wood is mounted in multiple stages is carried into a drying chamber through an entrance whose door is opened by a traveling rail to accommodate the wood therein, and the entrance is closed by the door. After that, the boiler is operated to feed live steam into the steam pipe in the upper part of the drying chamber where the boiler chamber can be piped. Live steam is vaporized into the room from above the inside of the drying room, and the room is heated from room temperature to 90 ° C to 100 ° C.
Raise the temperature. Then, the heat of the live steam spreads to the lumber on the trolley, which is stacked and accommodated in a multi-stage manner at intervals of heat passage, by the circulation device to heat the lumber. At this time, when the internal pressure rises due to the heating and temperature rise of the room temperature by live steam, it is exhausted to the outside of the drying room through the exhaust device,
The inside of the drying chamber is maintained at or near normal pressure. The temperature inside the drying chamber gradually rises above 90 ° C due to live steam
When the temperature reaches 100 ° C, the humidity also gradually rises to 100% as the temperature rises, and the drying of the wood surface layer reaches 100%.
Heat is gradually transferred to the central layer while being suppressed by a humidity atmosphere of 90% or more immediately before boiling of water to 90 ° C to 100 ° C.
The entire inside is heated uniformly and in equilibrium to a temperature close to ℃. That is, the entire inner region from the surface layer to the central layer is heated uniformly and in equilibrium according to a so-called drying schedule that balances temperature and humidity by combining temperature and humidity.

90 ° C. just before the entire interior of the wood boils
When heated to a temperature close to ~ 100 ° C, high temperature steam is sent from the boiler room to the heater in the upper part of the drying room.
Heat and raise the temperature from 00 ℃ to 200 ℃. Then, the inside of the wood is heated to 100 ° C to 200 ° C all at once, and the water inside the wood starts to boil at once and is blown out from the mouths (cuts) of both ends of the wood. Thereby, the wood is dried to the point of fiber saturation. At this time, since the internal pressure in the drying chamber is naturally exhausted from the exhaust device and maintained at or near atmospheric pressure, the water inside the boiled wood is blown out at once from the mouths of both ends and the surface side and the center side And the drying rate (rate of decrease in water content) are equilibrated, or the drying rate on the central layer side is brought as close as possible to the surface layer side to uniformly and equilibrate the entire inner region.

When the water content in the wood reaches the fiber saturation point, the drying conditions such as the dry-bulb temperature and the wet-bulb temperature in the drying chamber are changed according to the drying condition of the wood, and the drying condition is set to a predetermined value. Drying is carried out for the above period to dry the water content inside the wood to the target water content.

According to the technical means described in claim 4, since the motor is installed outside and the rotating power is transmitted to the propeller fan in the drying chamber, the indoor temperature is 100 ° C. or more. The motor is protected from heat.

According to the fifth aspect, when the internal pressure becomes higher than the normal pressure as the inside of the drying chamber is heated and heated by the live steam vaporized from the vaporizing tube above the drying chamber and the heat radiated from the heater. The opening / closing damper of the exhaust passage is pushed by the internal pressure and opens. As a result, the internal pressure in the drying chamber that exceeds the atmospheric pressure is naturally exhausted to the outside of the drying chamber through the exhaust passage.Therefore, the condition under which the water inside the boiling wood is blown out from both ends of the wood at once, that is, the internal pressure of the drying chamber is always Maintained at or near pressure.

[0018]

[Examples] An example of carrying out the present invention will be described below with reference to the drawings. Figs. 1 to 5 show a method for drying a raw log 1 with bark (hereinafter, simply referred to as "log") (hereinafter, referred to as "this method"). An example of a drying apparatus for carrying out the above is shown. A is a heat insulating material 2- between an outer wall material 2-1 made of corrugated steel plate and an inner wall material 2-2 made of stainless steel plate subjected to ceramics coating treatment (surface treatment). Floor A-1, built with 3 loaded, sidewall A-2,
This is a drying room that is assembled from a ceiling A-3 in a plane and horizontally long rectangular shape. A large number of logs 1 stacked in multiple rows in a horizontal row at intervals of heat passing through the floor A- in the drying room A- It is configured so that it can be carried in and stored on a carriage 4 traveling on a stainless steel rail 3 laid from 1 to an entrance P on one side thereof to the outside. An exhaust device 5 is provided at an appropriate position on the side wall A-2 of the drying chamber A to prevent the internal pressure from increasing due to the temperature rise in the room.
Is provided, and the interior of the drying chamber A is maintained at or near atmospheric pressure by spontaneously exhausting from the exhaust device 5.

Incidentally, the drying chamber A of the present embodiment has a lower unit A'in which a whole surface of the floor A-1 and a side wall A-2 rising up from the periphery of the floor A-1 are integrally assembled and constructed, and a remaining unit A ' The side wall A-2 and the ceiling A-3 are integrally assembled and constructed, and the upper unit A ″ is transported to the site, and at the site, the side wall A-2 of the lower unit A ′ and the side wall A of the upper unit A ″. -2 It is constructed by connecting the lower end with welding etc. (see Fig. 3).

The exhaust device 5 is released when the internal pressure that rises due to the heating and temperature rise in the drying chamber A exceeds the normal pressure, and the internal pressure is naturally exhausted to the outside of the drying chamber A to reduce the internal pressure in the same. It plays a role of maintaining at or near atmospheric pressure. As shown in Fig. 6, the exhaust passage 5-1 opened in the side wall A-2 of the drying chamber A is pushed by internal pressure and its exhaust direction is increased. Deploy the opening and closing damper 5-2 that makes the movement to release only
The open / close damper 5-2 is automatically released by the internal pressure. The opening / closing damper 5-2 is formed of a lightweight member that can be released by being pressed by the internal pressure in the drying chamber A, and the upper side of the opening / closing damper 5-2 is vertically supported so as to be freely opened / closed in the exhaust passage 5-1. And
Attach the seal frame 5-3 that stops the movement toward the drying chamber A side with the open / close damper 5-2 hanging vertically (closed state) and release it only in the exhaust direction by attaching it to the peripheral wall of the exhaust passage 5-1. I'm trying to make it. Further, an exhaust fan 6 for forcibly releasing the opening / closing damper 5-2 to exhaust the internal pressure when the drying apparatus of the present invention is used for low temperature drying can be inserted and connected to the exhaust passage 5-1 of the exhaust device 5. (See FIG. 7).

Reference numeral 7 in the figure is the floor of the drying chamber A as shown in FIG.
It is a drainage hole that is provided like a passage toward the outside in a suitable place of A-1 so that the water blown out from the log 1 can quickly escape to the outside without accumulating on the floor A-1. In addition to the role of draining the water discharged from the log 1 to the outside, the drain hole 7 also discharges the exhaust of the same pressure to the outside so as to suppress the rise of the internal pressure due to the temperature rise of the room. It also serves as a water drainage and exhaust hole, and plays a role of maintaining the inside of the drying chamber A together with the exhaust device 5 at a normal pressure or in a state close thereto.

In the vicinity of the ceiling A-3 at the upper part of the drying chamber A, the vaporizing pipe 8 has been piped from the boiler chamber B beside the drying chamber A.
A heater 9 and a heater 9 are installed in the longitudinal direction, and primary drying is performed by heating and raising the temperature of the room from room temperature to 90 ° C or more to 100 ° C with live steam that is vaporized from the vaporizing pipe 8. The heat radiated from the inside of the room
By performing secondary drying that heats and raises the temperature from 100 ° C to 200 ° C, for example, log 1 with a water content of 140% is dried to a fiber saturation point of 25 to 28% up to the target water content of 17%. It has become. The maximum capacity of the boiler used in this embodiment is about 164 when the working pressure is 7 to 8 kg / cm ² and the saturation temperature is
~ 170 ℃, the saturation temperature is about 204 at 16Kg / cm ^2.
° C.

A plurality of vaporizing pipes 8 are divided into right and left in the vicinity of the ceiling A-3 of the drying chamber A, and the live steam sent from the boiler chamber B is vaporized into the drying chamber A from the vaporizing port. At the very least, it is configured so that the room can be heated and raised from room temperature to 90 ° C to 100 ° C.

The heater 9 is a ceiling A-3 of the drying chamber A. A plurality of finned heating pipes 9-1 for passing steam are divided into left and right pipes arranged in parallel in the upper and lower directions to heat the heating pipe 9-1. It is a heat exchanger that heats the drying chamber A by exchanging it, and steam is added to each heating pipe.
Heat is exchanged with the inside of the drying chamber A through the inside of 9-1 so that the inside of the drying chamber A can be heated and heated up to 100 ° C to 200 ° C all at once with the live steam vaporized from the vaporizing pipe 8. It is composed.

Further, in the vicinity of the ceiling A-3 above the drying chamber A, there are several units that can spread the live steam to be vaporized from the vaporizing pipe 8 and the heat by heat exchange with the heating pipe 9-1 all over the room in a million valves. Circulation equipment
10 are installed so that all the logs 1 on each carriage 4 which is divided into several carriages 4 and carried into and accommodated in the drying chamber A can be uniformly heated.

The circulation device 10 has a ceiling A-3 as shown in FIG.
A propeller shaft 10-1 is horizontally supported by a heat-resistant bearing 12 on the lower end of a supporting member 11 hung from above, and one end of the propeller shaft 10-1 is projected outside the drying chamber A through a through hole 13 formed in a side wall A-2. Together with the side wall on the axis of the shaft 10-1
A-2 Install a motor 10-2 outside and couple the motor 10-2 with the protruding end of the shaft 10-1.
Connect directly with 14. Then, the propeller fan 10-3 is attached to the other end of the propeller shaft 10-1 existing in the drying chamber A.
Attach.

The propeller shaft 10-1 is made of stainless steel having excellent heat resistance, and one end of the propeller shaft 10-1 projects outward from the through hole 13 of the side wall A-2 and the other end of the propeller shaft 10-1 is located above the drying chamber A. 8 and the heater 9 are formed to have a length, and the other end is a ceiling between the vaporizing tube 8 and the heater 9 on both sides.
A heat-resistant bearing 12 is used to rotatably support the lower end of a support tool 14 vertically installed on A-3, and one end side of which is projected to the outside is a bearing 16 mounted on a base 15 on which a motor 10-2 is installed.
It is installed horizontally between both bearings 12 and 16 by directly supporting it on one side, and the one end side projecting to the outside is directly connected to the motor 10-2 by the coupling 14 and both sides of the upper part of the drying chamber A are connected. A propeller fan 10-3 is attached to the other end located between the vaporizing tube 8 and the heater 9. Then, a heat-resistant seal member 17 is attached to the outer edge of a through hole 13 formed by inserting a stainless steel pipe from the inside of the drying chamber A to the outside of the propeller shaft 10-1 so that the indoor heat flows out ( release)
It is designed to prevent you from doing so.

By the way, the heat-resistant bearing 12 is formed by interposing a ball made of ceramics between a bearing case made of stainless steel and a shaft support case, and the propeller shaft 10-1 is not affected by heat in the room. Is supported smoothly.

The circulation device 10 is the propeller shaft 10.
-By adopting the external installation structure in which the motor 10-2 that drives and rotates the propeller fan 10-3 via -1 is installed outside, it is considered not to be directly affected by the heat in the room exceeding 100 ° C. It is designed to extend the service life by protecting the heat-sensitive motor 8-2 from heat.

Next, a description will be given of the drying of logs by the present method using the drying apparatus configured as described above. First, steam is sent from the boiler chamber B to the vaporizing pipe 8 above the drying chamber A and steaming is performed. Drying room A with only live steam blown from the shooting tube 8
Are heated from room temperature to 90 ℃ or more to 100 ℃ and are piled up in multi-stages at intervals with heat passing by square timbers 18 such as piers and on the top log 1 to prevent warping during drying. Heat processing of each log 1 is carried out by distributing the heat of 90 ° C to 100 ° C to the log 1 on the trolley 4 carried in and housed in the drying chamber A with the weight 19 placed thereon by the circulation device 10 to 10,000 valves. Primary drying is performed. Next, steam is sent from the boiler room B to the heater 9 in the upper part of the drying room A, and heat is exchanged with the heat radiated from the superheater tube 9-1 of the heater 9 to heat and raise the room at a temperature of 100 ° C to 200 ° C at a stretch. Warmly log 1
The log 1 with a water content of 140% is heated to 100 ° C to 200 ° C at a high temperature by secondary drying.
It will dry up to a target water content of 10% without cracking, which is the biggest problem of log drying. And log 1 is 17
When the water content is dried to a target moisture content of%, the temperature condition of only the wet-bulb temperature in the room is changed, and the drying process is performed to remove the drying stress and the water gradient remaining in the wood 1 under the conditions.

As a drying condition of the drying chamber A in this method, the temperature is kept within the range of 90 ° C. to 100 ° C. during the primary drying. 100 ℃ or more to 200 ℃ at the time of secondary drying
Keep within the range of. The dry-bulb temperature is 70 at the time of the third drying.
It is necessary to keep the wet-bulb temperature within the range of 64-69 ° C (relative humidity of about 76-96%) depending on the degree of dryness of ℃ and log 1.

The reason is as follows. In the case of primary drying, if the drying temperature in the drying chamber A is 90 ° C. or lower, the inside of the log 1 cannot be heated sufficiently and evenly to the central layer thereof just before the temperature range where the water content in the chamber boil. That is, when the secondary drying is started, the drying temperature is suddenly raised to 100 ° C or more to 200
When heating and raising the temperature to ℃, log 1 at about the same time
If the internal moisture starts boiling at once and the internal drying is not performed quickly, the moisture content of the moisture will be higher than that of the central layer side,
The surface layer of log 1 where cracking is likely to occur is 100 ° C or above ~ 2
Due to the high temperature heat of 00 ° C, drying is started first, and radial cracks are generated in the surface layer toward the central layer. More specifically, if it takes time until the internal water content starts to boil after the secondary drying, the evaporation of water in the surface layer of the log 1 proceeds first, and the surface water content before the internal water content starts to boil. This is because the part is dried and the surface layer part is cracked due to the contraction in the circumferential direction.

On the other hand, when the temperature exceeds 100 ° C., the boiling of the internal moisture starts halfway, and it is not possible to expect a blowout of moisture from the wood mouth. At the same time, the moisture evaporation of the surface layer progresses and the surface layer side and the central layer side This is because it is not possible to equilibrate the drying rate (reduction rate of water content) with or to create a drying condition (drying atmosphere) that brings the drying rate of the central layer side as close as possible to the surface layer side. By setting the drying temperature of the primary drying in the range of 90 ℃ or more to 100 ℃, immediately after entering the secondary drying, a boil of boil from the mouth of both ends of the log is achieved.
In the drying chamber A, the drying time can be further shortened, and the drying condition on the central layer side can be equilibrated or brought closer to the surface layer side.

In the case of secondary drying, the drying temperature in the drying chamber A is
If the temperature is 100 ° C or lower, the same problems as those in the case of exceeding 100 ° C in the primary drying described above occur, and it is impossible to expect a rapid boiling blowout of the internal moisture.

On the other hand, when the temperature exceeds 200 ° C., it is possible to expect rapid boiling of internal water and a quick blow from the mouth, while log 1
Evaporation of water in the surface layer proceeds faster than that, and the water content of the surface layer evaporates completely before the internal water content reaches the target water content of 25 to 28% before reaching the fiber saturation point. This is because there is a risk of carbonization beyond drying. By setting the drying temperature in the secondary drying in the range of 100 to 200 ℃, the inside of the log 1 heated up to the boiling point of the internal water during the primary drying is heated to the boiling point all at once and the surface layer is dried. Before proceeding, the water can be blown out at once from the wood mouth to speed up the internal drying. That is, log 1
Drying rate (rate of decrease of water content) between the surface layer side and the center layer side of
Can be equilibrated, or the most preferable drying condition (drying atmosphere) can be created in the drying chamber A so that the drying speed of the central layer side can be made as close as possible to the surface layer side.

An experimental example of this method will be described below based on the above drying conditions. Room temperature Primary drying 90 to 100 ° C Secondary drying 100 or more to 200 ° C Third drying Dry bulb temperature 70 ° C, Wet bulb temperature 64 to 69 ° C (relative humidity approx. 76 to 96%) Logs used Kind of species Softwood with bark (logs) Shape: end diameter class 20 cm or less, length 3 m A large number of logs 1 are placed in a multi-tiered manner on several trolleys 4 with a space for heat passing between the logs 1 with a pier 16 interposed between them. It is carried in and housed inside, the door A-4 and the inspection door A-5 are closed, and the raw steam is sent into the drying chamber A from the vaporizing pipe 8 and only the raw steam is heated from room temperature to 90 to 100 ° C in the drying chamber A. Was heated and heated to perform primary drying in which the temperature of the room reached 90 to 100 ° C. and maintained for 6 to 8 hours.

The room is heated from room temperature to 90 to 100 ° C.
It takes about 2 to 3 hours to raise the temperature. At this time, the circulation device 10
The above operation is started to stir the raw steam in the whole chamber to heat the respective logs 1 while distributing the heat to the logs 1 housed at intervals of heat passage. The room temperature is
When the temperature reaches 90 to 100 ° C, the indoor humidity gradually rises to 100% as the temperature rises, and the drying of the surface layer of the log is suppressed by the humidity atmosphere of 100%. Then, the log 1 is heated uniformly and in equilibrium to a temperature close to 90 to 100 ° C. immediately before the water in the entire region boils while the surface of the log 1 is prevented from being dried.

Then, it takes 6 to 8 hours to reach the center layer by 100.
After the inside of the log 1 has been sufficiently heated to a temperature close to ℃, the heater 9 keeps the room temperature from 90 to 100 ℃ and the temperature above 100 ℃ to 200 Room temperature is 100
From the time when the temperature reached to above-200 ° C., secondary drying was carried out while maintaining the room temperature for about 24 hours.

It should be noted that the temperature in the room is 90 to 100 ° C. and above 100 to 200
It takes about 3 hours to heat and raise the temperature to ℃. The room temperature is
When it reaches over 100-200 ℃, the water inside the log 1 will boil up to 100 ℃ or more, and the water inside the log 1 will boil all at once and will be pushed out from the internal pressure inside the log 1 which is increased accordingly. It blows out from the mouths of both ends at once. Looking at the water content inside the log 1 after 24 hours, it can be seen from FIG. 9 that the log 1 with a water content of 140%
It can be seen that the fiber was dried to a fiber saturation point of about 25 to 28% in about 4 days. Room temperature of 100 ~
Even if the temperature rises to 200 ° C, the internal pressure in the drying chamber A is automatically released to the outside from the exhaust passage 5-1 by the automatic release of the opening / closing damper 5-3 of the exhaust device 5, so that the inside of the drying chamber A is always at normal pressure, Or the water inside the boiled log 1 which is maintained in a state close to that is blown out at once from the throats of both ends of the log 1 and the drying rate (rate of decrease of water content) on the surface side and the center layer side is in equilibrium,
Alternatively, it was confirmed that the drying rates on the surface layer side and the center layer side were as close as possible to each other to uniformly and equilibrarily dry the entire inner region. As a result, it was confirmed that the water content inside the log 1 was lowered without causing any cracks.

At the time when the water content falls to the fiber saturation point of 25 to 28%, the dry-bulb temperature in the room is adjusted according to the drying condition of the log 1.
After changing the condition of 70 ℃ and wet bulb temperature to 68 ℃ (relative humidity about 91%) and maintaining the condition for about 1 day, only wet bulb temperature is 66 ℃ (relative humidity about 83%) Was changed to, and the third drying was performed for about 1 day. In this case, by gradually reducing the humidity as the room temperature decreases,
It was possible to dry the water content inside the log 1 to a target water content of 17% without cracking.

Finally, as a treatment for removing the dry stress and moisture gradient (difference in water content between the surface layer and the central layer) remaining in the dried log 1, only the wet bulb temperature is 69 ° C.
After changing the drying conditions to 96%) and maintaining the drying conditions for about 1 day, the door A-4 is opened and the log 1 is taken out from the drying chamber A.

In the drying method of the present invention, in addition to the drying of the bark-containing log 1 described above, it is possible to dry so-called squares or plates made by stripping the peeled logs into squares or plates.
That is, it is possible to completely prevent the cracking from occurring and to completely dry the entire inside to the target water content, as in the case of drying the bark-containing log 1 described above. Examples of wood intended for drying include larch, spruce, red pine, etc. from conifers, and oak, wig, shioji, etc. from hardwood, but are not limited to these, and the present invention is a structural material (building material ), All wood used for construction materials and furniture materials is subject to drying.

[0043]

Since the drying method and the apparatus therefor according to the present invention are constructed as described above, the following operational effects are achieved. ． In the primary drying, the room is kept at a humidity atmosphere of 100% by heating and raising the room temperature from 90 ℃ to 100 ℃ only with live steam, and the logs are heated to 90 ℃ to 100 ℃ in the atmosphere. Therefore, the entire area inside where the drying of the surface layer is suppressed to the center layer of the wood is 90 ° C just before the water boil.
Above, it is uniformly and equilibrium heated to a temperature close to 100 ° C.
Then, in the secondary drying, the temperature of the room suddenly rises above 100 ° C ~ 2
By heating and raising the temperature to 00 ℃, the inside of the log heated to just before boiling in the primary drying is heated to 100 ℃ or more to 200 ℃ at a stroke, and the water inside is boiled at once and blown out at once from the wood mouth. As a result, the drying rate (rate of decrease in water content) between the surface layer and the central layer side of the wood is balanced, or the drying rate on the central layer side is brought as close as possible to the surface layer to make the fiber saturation point uniform and balanced throughout the interior. Can be dried up to. Finally, by changing the drying conditions such as the dry-bulb temperature and the wet-bulb temperature in the room in the tertiary drying according to the drying condition of the wood and maintaining the drying conditions for a predetermined time, the water content of the wood is changed to the target water content. , For example, the water content is 140
A dry finish can be performed to dry% wood to a target moisture content of 17%.

Therefore, according to the present invention, the drying rate (moisture content reduction rate) between the surface layer side and the central layer side, which is important for preventing cracks when artificially drying wood, is balanced or set to the surface layer side. Since it is possible to dry the wood while creating a drying condition (drying atmosphere) that makes the drying speed on the central layer side as close as possible, it is possible to prevent the generation of cracks and completely dry the wood to the target moisture content. Therefore, the waste of dried wood due to cracking is eliminated unlike conventional drying,
Due to the high cost due to lack of resources, especially the shortage of building materials, which has inevitably led to soaring prices, it is possible to supply dry wood at a low price, and to continue to prosper in the future. It will be a drying method for a period. Moreover, since the drying is performed by blowing out the moisture inside from the mouth at once, it is possible to realize a drastic reduction in the drying period compared with the conventional drying technique in which the moisture is gradually evaporated from the surface layer of the wood. To improve production efficiency,
A drastic reduction in drying cost can be achieved.

[0045] By installing the motor outside and transmitting the rotational power to the propeller fan inside the drying room, the motor is protected from the indoor heat that reaches a drying temperature of 100 ° C or higher. Therefore, it is possible to prolong the service life of the motor by protecting it from heat, which is not susceptible to heat inside the room above 100 ℃.

[0046] When the internal pressure becomes higher than normal pressure due to the heating and temperature rise in the drying chamber due to the heat emitted from the heater and the live steam evaporating from the steam pipe above the drying chamber, the opening / closing damper of the exhaust passage leading to the outside will Since the internal pressure was automatically released by the internal pressure and the internal pressure exceeding the atmospheric pressure was naturally exhausted to the outside of the drying chamber through the exhaust passage, the condition for blowing out the water inside the boiling wood from both ends of the wood at once, that is, the internal pressure of the drying chamber is Maintained at or near normal pressure. Therefore, it is possible to create a drying condition in the drying chamber in which the boiling water inside the wood is blown out at once from the mouth of the wood to rapidly dry the inside.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a drying apparatus for carrying out the drying method of the present invention, which is shown with a partly cutaway section.

FIG. 2 is a plan view of the same with a partially cutaway section.

FIG. 3 is an exploded perspective view showing a lower unit and an upper unit that construct a drying chamber.

4 is a vertical side view taken along the line IV-IV in FIG.

5 is an enlarged cross-sectional view taken along the line VV of FIG.

6 is an enlarged sectional view taken along line VI-VI of FIG.

FIG. 7 is an enlarged cross-sectional view showing a state in which an exhaust fan is connected to a through hole of an exhaust device.

FIG. 8 is an enlarged sectional view taken along the line VIII-VIII in FIG.

[Fig. 9] A graph showing an example of a drying experiment when a coniferous tree (log) with a bark having an end diameter of 20 cm or less and a water content of 140% is used.

[Explanation of symbols]

A: Drying room A-1… Floor A-2
… Sidewall A-3… Ceiling 1… Log with bark (wood)
5 ... Exhaust device 5-1 ... Exhaust hole 5-2 ... Open / close damper
8 ... Steaming tube 9 ... Heater 10 ... Circulation device 10-1
… Propeller shaft 10-2… Motor 10-3… Propeller fan
A '... Lower unit A "... Upper unit

Claims (5)

[Claims] 1. A drying chamber having an exhaust device for accommodating a large number of pieces of wood in a multi-tiered manner at intervals with heat passing between the pieces of wood and maintaining an internal pressure at or near normal pressure. Only live steam is sent to heat the room from room temperature to 90 ° C to 100 ° C, and the entire area from the surface layer to the central layer of wood is heated to 90 ° C to 100 ° C. Primary drying, After the central layer is heated to 90 ° C or higher to 100 ° C, the temperature of the room is suddenly heated to 100 ° C or higher to 200 ° C by a heater to boil the moisture in the wood to reach the target moisture content. Secondary drying of high temperature treatment up to the saturation point, and when the water content falls to the fiber saturation point, the temperature conditions such as the dry-bulb temperature and the wet-bulb temperature in the room are changed, and the low-temperature wet treatment up to the target water content is performed according to those conditions. A method of drying wood that includes tertiary drying. 2. The drying method according to claim 1, wherein the temperature condition of only the wet-bulb temperature in the room is changed when the wood is dried to the target moisture content, and the drying stress remaining on the wood is changed by the condition. And a method for drying wood, which comprises performing a drying process for removing the water gradient. 3. A boiler room, which has a substantially rectangular flat surface having a wood inlet / outlet closed on one side by a door, and a boiler room installed beside the drying room, wherein the boiler is located above the inside of the drying room. A steaming pipe that is piped from the room to feed live steam into the room to heat and heat it, and a heater to heat and heat the room by heat exchange are installed, and the drying room is in the appropriate place inside the room. Exhaust device that allows natural exhaust during heating / heating to maintain the internal pressure in the room at or near atmospheric pressure, and the heating by the vaporizing pipe and heater
A circulator that circulates the heat throughout the room at the time of temperature rise is installed.Furthermore, a trolley on which a large number of woods are stacked and mounted on the floor of the drying room is carried into the drying room, and after drying is carried out. A wood drying device characterized by laying running rails. 4. The drying device according to claim 3, wherein the circulation device horizontally supports a propeller shaft on a lower end of a support member hung from the ceiling via a heat-resistant bearing, and opens one end of the propeller shaft on a side wall. The protrusion is projected to the outside of the drying chamber through a through hole having a heat resistant seal member, and a motor is installed outside the side wall on the axis of the shaft, and the protruding one end of the shaft is connected to the motor, and A drying apparatus for wood, characterized in that a propeller fan is attached to the other end of the shaft that is present inside the drying chamber. 5. The drying device according to claim 3, wherein the exhaust device is provided with an opening / closing damper that is automatically released in an exhaust direction by being pressed by an internal pressure in the drying chamber, in an exhaust passage opened at a proper place in the drying chamber. A drying device characterized by being configured.