JP2001260105A - Method and apparatus for drying wood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply wood of high dryness (a water content of <=20%) at a low cost by preventing crack, bend and warping when (or after) boxed timber (especially home produced material), general timber and the like are dried. SOLUTION: A method and an apparatus for drying wood are provided wherein live steam and smoking are mixed and returned to normal circulation by high speed wind to a drying room in which the wood is stored a temperature in the drying room is kept at 100% or its vicinity, a core temperature of a material is kept at 80-90 deg.C necessary for treating heat of a wood core part, a water content in the wood is kept for 10-120 h without being boiled, the water content of the wood core part is previously allowed to approach 20% of a target or at least its vicinity, and the outside water content is lowered thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method and an apparatus for drying wood.

[0002]

2. Description of the Related Art An overview of currently used wood dryers is as follows. Steam dryer (steam-hot air convection method): Generally, steam is sent in for initial humidification, hot air from a steam heater is convected, the room temperature is raised to 150 to 160 ° C, and the humidity is lowered after the required time. And dry. The problem with this method is that even when the sapwood is dried (about 10%), the core is not dried (water content is 40 to 50%). Room temperature (material temperature) 150-1
Raising to 60 ° C. is considered unsuitable for drying wood. Reducing the indoor humidity in the drying process may cause cracks. Smoke dryer (method using smoke): There are mainly two types of methods for giving smoke. (1) A method in which smoke is smoked at the bottom of wood in a room. (2) Smoke is generated outside the room,
How to send this. The problem is that it has not been dried. There is variation. The drying conditions cannot be stabilized. For example, the vertical temperature difference in the drying chamber is 20 to 30 ° C. As a result, not only the room temperature but also the humidity varies. Microwave dryer (microwave heating method): Problem-Since the wood is heated from the center, the whole wood (especially the sapwood) is not dried. The core is hot (10
(0 ° C. or more), the inside is in a state of boiling and boiling, the wood is not dried and the core is crushed, and the strength is reduced as a structural material. High-frequency dryer (steam-high-frequency heating type): Problem-Contrary to the microwave type, the material is heated from the outer periphery of the wood, so the core temperature does not rise and advanced drying is not possible. When the outer peripheral portion and the sapwood portion are dried first, the drying portion has a heat insulating effect and poor heat conduction, and does not dry because the core temperature does not easily rise to about 60 ° C. or more. The following can be said about wood drying in the above-mentioned conventional dryer. (1) Attempting to dry wood from outside by increasing the material temperature. (2) Since the outer peripheral portion or the core portion is suddenly heated, partial drying is prior. (3) In the smoking method, it is intended to dry only with smoke. (4) Humidification with steam does not contribute to effective drying. As described above, conventional dryers have advantages and disadvantages, cracks,
Many bends and warpages occur, and even when the surface is dried, the core has a high moisture content, and is highly dried (for example, a moisture content of 10%).
Below). In particular, even steam dryers, which currently account for over 95% of the market, need to rely on pre-treatment machines and natural drying, and yet prevent cracking and reduce the moisture content of the core of the core material to, for example, less than 20% in about 7 days. Drying technology and performance. Therefore, trees (mainly domestic cedar) are described. In FIG. 6 showing a cross section of a tree, in the sapwood part, a cell conduit passes in the trunk direction between the annual rings, and the membrane / pore membrane retains water between cells (water content is 120 to 150). %). The transition material part grows in the growth period of 10 to 15 years, and does not move the moisture of the core part and the sap part,
Covers the water retention of the core (also called white line band).
The water content of the core is high (200 to 250%), and it is difficult to remove water from the sap. As described above, each part of the wood has its function and the moisture content also differs. Further, a growth stress is formed inside, and the result cannot be expected by considering such a wood as a homogeneous material and considering a drying method.

[0003]

SUMMARY OF THE INVENTION Cracking, bending, and the like during drying (or after) of core materials (particularly domestic materials) and general materials, etc.
An object of the present invention is to prevent warpage and to supply high-grade (less than 20% water content) dry wood at low cost.

[0004]

According to the first aspect of the present invention, live steam and smoke are mixed and recirculated by high-speed air in a drying chamber in which wood is stored, and the humidity in the drying chamber is maintained at or near 100%. In addition, the core temperature is required to be 80 for the heat treatment of the wood core.
Keep at ~ 90 ° C and keep the moisture in the wood for 10 to 120 hours without boiling, bring the moisture content of the wood core to the target 20% or less near the target first, and then lower the moisture content of the outside This is a method for drying wood, characterized by going.

[0005] The invention of claim 2 is a drying chamber for accommodating wood, means for mixing and refluxing live steam, smoke and hot air in the drying chamber, temperature, humidity and smoke in the drying chamber. concentration,
A means for measuring the humidity of the wood core and a means for controlling the water content of the wood core so as to first bring the water content close to the target of 20% or less or less, and thereafter reduce the external water content. A wood drying device characterized by the following.

A third aspect of the present invention provides a ventilation duct comprising a slit plate on the entire bottom of the drying chamber and a space below the fin tube heater below the same, a slit plate on the entire ceiling of the drying chamber, and a fin tube on the upper side. An exhaust duct comprising a space above the heater, a blower having an air outlet and a suction port connected to the air duct and the air exhaust duct, a smoke generator connected to the air inlet, and a The wood drying apparatus according to claim 2, further comprising a steam pipe connected thereto, a damper communicating the intake port with the outside air, and a damper communicating the exhaust port of the exhaust duct with the outside air.

According to a fourth aspect of the present invention, there is provided the wood drying apparatus according to the third aspect, wherein the opening ratio of at least one slit of the slit plate is configured to equalize the upward airflow.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In practicing the present invention, first, moisture is given to a sapwood portion, and moisture is removed from the core first. During drying, the humidity in the drying room is maintained at 100% (that is, the sapwood portion is not dried first). During drying, the core temperature is 80-90.
Keep at ° C. The drying room temperature does not rise above 115 ° C.
Continue sending smoke and air until the target dry moisture content is reached. As is apparent from FIGS. 1 and 2, the wood drying apparatus according to the present invention comprises a drying chamber 1, a reflux blower unit 2, a smoke generator 5, a smoke material storage tower 4, a smoke material (eg, sawdust, chips). ) It consists of a charging machine 3 and a boiler unit 6, and a drying room 1
There is an entrance 7 at the front (left end) of the vehicle, and a cart 8 loaded with wood a is carried into the room.

An air duct 9 is provided on the entire bottom of the drying chamber 1 and an air exhaust duct 10 is provided on the entire surface of the ceiling. Fin tubes 11 are provided over the entire area above the air duct 9 and below the air exhaust duct 10, respectively. 12 are arranged.

Slit plates 13 and 14 are provided over the entire surface of the upper part of the air duct 9 and the lower part of the exhaust duct 10, respectively. The opening ratio (distribution density) of the slits of these slit plates is Is large (the total area of the openings is large), and is gradually reduced toward the entrance side, so that the wind pressure is applied to the entire surface of the wood a vertically and uniformly. The wind from the blower 15 is supplied to the blower port 16, the blower duct 9, together with steam from a steam pipe 39 (FIG. 2) described later.
Through the fin tube 11 and the slit plate 13, high humidity
After passing through the drying chamber 1 and the wood a in a high-temperature hot air state, and being reheated by the slit plate 14, the fin tube heater 12, and the exhaust duct 10, it exits from the exhaust port 17 and passes through the return duct 18, The air is again sucked and pressurized into the blower 15 from the suction port 19 of the blower 15, and is returned from the blower port 16.

The smoke material (sawdust, chips) b in the smoke material charging machine 3 is pumped together with air by a blower 20, passes through a cyclone 21, and is scattered and stored in a smoke material storage tower 4.
The blower 20 is configured so that when the level sensor 22 detects a full level, the blower 20 is stopped by the signal, and a replenishment instruction is displayed by a lamp (or / and a buzzer warning) by a decrease signal of less than the full level, and re-storage is started.

The smoke material b is supplied from the bottom of the smoke storage tower 4 to the hot plate 2 at the center bottom of the smoke generator 5 by a screw conveyor 23.
4 is sent on. The screw conveyor 23 is stopped at regular intervals (every time one batch of the smoke material b is burned), the hot plate 24 is opened downward to drop and discharge the combustion ash d, and then the hot plate 24 is returned to its original position. Then, the smoke material b is sent to restart the smoking.

The smoke c is supplied to the vertical duct 2 in the smoke generator 5.
6, the air enters the suction port 19 of the blower 15 from the smoke introduction duct 27, and is pressurized by the blower 15;
From the drying chamber 1.

When the ventilation of the smoke c is cut off, the screw conveyor 23 is stopped, the power of the hot plate 24 is turned off, the generation of smoke is stopped, and the electric damper 28 is closed.

An air introduction adjusting port 29 is provided at the bottom of the smoke generator 5, and its opening is initially adjusted and fixed, for example, together with the temperature setting of the hot plate 24. A gas vent 25 is provided at the top, and the generation status of smoke c and the blower 1
The state of inhalation into the device 5 is visible from outside.

Electric dampers 30, 31 are provided above the reflux duct 18, and are connected to an electric control unit 55 (FIG. 2). In the cooling of the drying schedule (D in FIG. 5), when the electric damper 30 is closed and the electric damper 31 is opened, the return air is discharged to the outside of the room to stop the return. At this time, the electric damper 28 is closed, the supply of the smoke c is stopped, and the normally closed electric damper 3 outside the suction port 19 is closed.
Open 2 to introduce outside air.

Live steam whose pressure has been adjusted by the pressure reducing valve 33 from the boiler unit 6 is discharged into the blower opening 16 from the end of the steam pipe 39. The pressurized steam whose pressure has been adjusted by the pressure reducing valves 34 and 35 is sent to the fin tube heaters 11 and 12, and heat and humidify the wood a in the drying chamber 1, and the exhaust duct 10
Used to heat the reflux air to the air.

Steam traps 40 and 41 are attached to the ends of the fin tube heaters 11 and 12, respectively.
The drain water is returned to the water supply tank in the boiler unit 6.

A smoke sensor 42 is provided at the center of the smoke generator 5.
Is provided. A smoke sensor 43 is provided above the entrance of the drying chamber 1.
And a humidity measuring device 44 are further provided with temperature measuring sensors 45 and 46.
Are attached to the lower part on the entrance side and the upper part on the rear side, and these are connected to the electric control panel 55. A large amount of condensed water accumulates at the bottom of the drying chamber during the drying process, and this condensed water is drained from the auto drain 47 at the corner of the drying chamber.

A heat insulating material 48 is attached to the entire inner surfaces of the drying chamber 1 and the door, and the protective plate 4 of the heat insulating material 48 is provided.
Numeral 9 is entirely welded to the wall of the drying chamber 1 to maintain the airtightness of the drying chamber 1. A heat insulating material 50 is also attached to the reflux duct 18 of the drying chamber 1, and a heat insulating material (not shown) is also attached to the steam pipe 39 extending downstream from the pressure reducing valves 33, 34, 35.

In order to measure the moisture content of the core of the wood a during drying, an electrode needle is driven into the wood located in the center of the drying chamber after the loading, and the connection between the humidity meter 51 and the lead wire is made after the loading. The work window 52 is configured to be operated. Drying room 1
Is connected to the electric control panel 55, and the pressure in the drying chamber 1 can always be supplied to the electric control panel 55 and controlled. A spring-type safety valve 54 is installed at the upper center of the drying chamber 1.

As a preparatory operation, the smoker blower 20, the smoker storage tower 4, the smoke generator 5 and the like are operated to fill the drying chamber 1 with smoke. The drying schedule is, for example, as follows. 1. Blowing starts from the start of drying. (1) Humidity in the drying room is 100%. (2) Core temperature is 80 ° C. (3) Smoke filling is achieved as quickly as possible. 2. The core temperature is maintained at 80 to 90 ° C. and the air blowing is continued until the target dry moisture content (for example, the core is 20%) is dried. 3. When the core water content reaches 20% (1) Stop sending in smoke (2) Reduce the air volume of the blower, and cool down time, for example, about 4
(3) The core temperature is set to 40 ° C. and the humidity in the drying room is set to 80% in 8 hours. Next, the drying operation will be described with reference to the schedule diagram of FIG. -The steam is sent from the steam pipe 39 to the fin tube heater 11, and the smoke c is sent at the same time. The steam is released and injected, and at the same time, the high-temperature and high-humidity steam (hot air) is refluxed by the operation of the blower 15 to be dried. High temperature in the room 1 rapidly,
Raise to high humidity smoke atmosphere. -The growth stress is removed by the thermal softening of the lignin, and the preparation for water outflow proceeds due to the destruction of the pore membrane. -While maintaining the inside of the drying chamber 1 at a predetermined temperature, humidity and smoke concentration, the reflux is continued to extract moisture from the wood. When the target dry water content point is reached, the supply of smoke and the heater are stopped, and the temperature is reduced according to the set cooling rate. At this time, the low-speed reflux is basically continued. Stopping the reflux (substantially the end of drying-wood transport O
K) Room temperature (end of drying-unloading of wood) Cooling rate Stop sending smoke (residual smoke in the drying room gradually attenuates) Stop sending live steam. In FIG. 5, the section A is heated, humidified, smoked,
B means cell membrane destruction, lignin heat softening (strain removal), C means water removal (drying), and D means cooling (drying). Further, the target dry moisture content at a core temperature of 80 to 90 ° C. of − is 20% or less, a reflux is stopped,
Means cooling rate, means smoking stop, means humidification stop.

The means for solving the above problems can be summarized as follows. The signals from the temperature measuring sensors 45 and 46, the humidity measuring devices 44 and 51, the smoke sensor 43, and the pressure gauge 53 are input to the computer of the electric control panel 55, and the inside of the drying chamber 1 is smoked by the computer. Adjust according to the schedule of humidity and temperature.
At this time, steam heat from the steam pipe 39 is used as a heat source. At the same time, live steam and smoke are mixed into the high-speed air to reflux,
Thermal efficiency is improved by preventing the inflow of outside air.
For example, keeping the humidity in the inside at 100%, making it easy to transfer heat into the wood by the far-red (far-infrared) effect of smoke, and the wind speed is 5-10m
It blows up evenly from the bottom at a rate of 1 / sec and eliminates uneven drying by applying evenly hot air to the pile.

By maintaining sufficient humidity (moisture) on the wood surface by keeping the humidity in the drying chamber 1 at 100%, the difference between the water content in the radial direction and the longitudinal direction of the wood can be reduced to a certain level. Take it, especially to prevent cracking of the wood surface due to drying. When the temperature inside the drying chamber 1 exceeds the 100 ° C range,
Although other steam dryers cannot maintain a humidity of 100%, the method and apparatus according to the present invention ensure the humidity by adhering water particles to the core of the smoke particles, and in combination with the action of the smoke. Therefore, the wood core temperature follows the temperature of the drying room,
The experiment succeeded in increasing the temperature by a difference of ° C.

By increasing the temperature of the wood core along with the temperature of the drying chamber, the wood core is maintained at 80 ° C. or higher required for heat treatment,
A temperature of 90 ° C or less at which water in the wood does not boil
By maintaining the water retention time for 0 to 120 hours, the water retention cell valve in the cell conduit is broken, and the water in the wood can be easily discharged to the outside.

In a conventional dryer, drying was particularly rapid from the small edge to around 30 cm, and it was difficult for moisture to escape due to shrinkage of cell conduits due to drying. However, as in the present invention, sufficient moisture, temperature and smoking were required. In addition, it is possible to remove the internal stress by increasing the internal temperature of the wood while performing the heat treatment while preventing cracking of the wood and to remove the internal stress, thereby removing the internal water and removing the wood in the fore-edge direction without obstructing the outflow of the internal water. That is, the water content of the core of the wood is first brought close to the target of, for example, 20%, and the water content that can be easily reduced is lowered thereafter, thereby preventing cracking due to the difference in the water content between the inside and the outside of the wood. Mandarin cracking due to boiling and boiling inside the wood can be prevented at the same time.

When the core moisture content falls to a predetermined value,
Stop smoking and gradually lower the drying room temperature to the outside temperature.
The humidity in the drying room is changed at a drying room temperature of 40% at 100%, the outside air flows into the drying room up to the outside temperature, the live steam is stopped, and the drying is switched to the wind drying by a high-speed fan (blower 15) to wet the surface of the wood. Gradually lower the rate to 10%.
Above, complete drying is difficult even if any of the four elements of temperature, humidity, smoke density, and wind are missing. Therefore, as described above, the above four elements are computer controlled by a measuring instrument.

[0028]

According to the first aspect of the present invention, an altitude free from cracks, bending, and warpage (for example, a core water content of 10 to 20%).
Dried wood can be reliably obtained.

According to the second aspect of the present invention, an apparatus suitable for implementing the method of the first aspect can be obtained at low cost.

According to the third aspect of the present invention, it is easy to implement a drying schedule.

According to the fourth aspect of the invention, it is easy to make the rising hot air uniform in the drying chamber.

[Brief description of the drawings]

FIG. 1 is a vertical side view of a drying apparatus according to the present invention.

FIG. 2 is a partial vertical plan view of FIG.

FIG. 3 is a schematic sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a schematic sectional view taken along the line IV-IV of FIG. 1;

FIG. 5 is a schedule diagram.

FIG. 6 is a sectional view of wood.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drying room 5 Smoke generator 9 Air duct 10 Air exhaust duct 11,12 Fin tube heater 13,14 Slit plate 16 Air vent 19 Suction port 29,31 Electric damper 39 Steam pipe 55 Electric control panel a Wood

Claims (4)

[Claims] 1. Steam and smoke are mixed and refluxed by a high-speed air in a drying chamber in which wood is stored, and the humidity in the drying chamber is kept at or near 100% and the core temperature is used for heat treatment of the wood core. Keep the required 80-90 ° C. and keep the water in the wood for 10 to 120 hours without boiling, bring the water content of the wood core first to the target 20% or less or less, and the external water content A method for drying wood, characterized by lowering it afterwards. 2. A drying chamber for accommodating wood, and means for mixing and refluxing live steam, smoke and hot air in the drying chamber;
Measure the temperature, humidity, concentration of smoke and the humidity of the wood core in the drying room. First, bring the moisture content of the wood core close to the target of 20% or less, and then the external moisture content. Means for controlling the temperature of the wood to be lowered. 3. A ventilation duct comprising a slit plate on the entire bottom of the drying chamber and a space below the fin tube heater below the same, and a space above the slit plate on the entire ceiling of the drying chamber and the fin tube heater above the same. An exhaust duct comprising
A blower having a blower port and a suction port connected to the blower duct and the exhaust duct, a smoke generator connected to the suction port, and a steam pipe connected to the blower port, respectively. 3. The wood drying apparatus according to claim 2, further comprising: a damper that communicates with the outside air, and a damper that communicates an exhaust port of the exhaust duct with the outside air. 4. 4. The wood drying apparatus according to claim 3, wherein the opening ratio of at least one slit of the slit plate is configured to equalize the upward airflow.