JP2002321203A - Method and apparatus for drying lumber by microwave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for drying lumber with microwave for accelerating heat drying by carrying out irradiation with microwave in drying in a lumber drying warehouse with a steam drying apparatus for lumber. SOLUTION: For the method for drying lumber with microwave, in the method for drying lumber with microwave comprising successive execution of a humidification mode control, a drying mode control and a cooling mode control, the humidification mode control carries out temperature control with a humidifer 9, the drying mode control controls a microwave transmitter by ON/OFF to evaporate water of the lumber by irradiating an inside of a drying room with the microwave to evaporate water in the lumber, and when a temperature in the drying room reaches a specific temperature or higher, a blower device 11 is turned ON. Further when the temperature reaches a set temperature or lower, the humidifier 9 is turned ON to carry out temperature control. Then, when a moisture inclination between a core of the lumber and its surface reaches an optional set value or under, the humidifier 9 and the microwave transmitter 15 are stopped to migrate to the cooling mode control. For the cooling mode control, when a temperature of the drying room reaches the set value or under, an atomizing spray is turned ON to carry out decrease of temperature by vaporization heat, and a water content of the lumber core is set at an optional specific value by gradually decreasing the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for drying wood using microwaves, which can dry wood as it is.

[0002]

2. Description of the Related Art Conventionally, wood has been subjected to a pretreatment to irradiate microwaves to increase the temperature and pressure inside the wood,
It is known from JP-A-6-297411 that the wood is dried in a drying chamber in which the temperature and humidity can be controlled. According to this known publication, when wood is irradiated with microwaves, water molecules inside the wood are activated by the characteristics of the microwaves, and as a result, the temperature and pressure inside the wood rise. When the temperature and pressure inside the wood rise, the cell valve of the wood is opened, so that the water inside the wood flows out of the cell valve and joins, and the joined water joins in a state where it is further connected to the kiguchi. Eventually, a water channel is formed inside the wood from its center to the mouth. And after performing such pre-processing,
When the wood is heated by blowing hot air or the like in a drying room in which the temperature and the humidity can be controlled, the moisture in the inside easily moves toward the mouth, and is discharged outside through the mouth. In addition, when this microwave irradiation is applied strongly to the center of the wood, the center is heated the most, and a temperature gradient is generated inside the wood that becomes lower at the tip of the wood, and as a result, the pressure becomes higher at the center. Therefore, the formation of the water channel is further promoted, which is more preferable. in this way,
It is a method of increasing the temperature and pressure inside the wood to form a water channel for guiding the moisture inside the wood to the mouth of the wood, and then drying the wood. However, it is possible to dry efficiently even the raw wood with bark. However, the above publications are not efficient because microwaves are used in the pretreatment step and microwaves are not directly used for drying wood.

[0003]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a method and apparatus for drying wood using microwaves, which irradiates microwaves during drying in a wood drying cabinet to promote heat drying in a wood steam drying apparatus. The purpose is to provide.

[0004]

For this purpose, a method for drying wood by microwave according to the present invention is directed to a method for drying wood by microwave comprising sequentially performing humidification mode control, drying mode control and cooling mode control. The mode control turns on the humidifier when the temperature of the drying chamber is lower than the set value.
Temperature control by high-temperature steam, and in the drying mode control, when the moisture gradient between the wood core and the surface is equal to or more than an arbitrary set value, the microwave transmitter is turned on / off to control the microwave into the drying chamber. Irradiate the wood to evaporate the moisture of the wood, and when the humidity in the drying room reaches a certain level or more, turn on the blower to discharge the air inside the drying room to the outside and introduce outdoor air into the drying room to reduce the humidity. If the temperature falls below the set value, turn on the humidifier to control the temperature.If the water gradient between the wood core and the surface falls below the set value, turn off the humidifier and microwave transmitter. When the humidity in the drying chamber is equal to or higher than the set value, the blower device is turned on and the air inside the drying chamber and the outdoor air are exchanged while performing heat exchange. The humidity in the drying room to the set value. Performs temperature drop due to heat of vaporization to ON spray spray if it becomes lower, it is to set the water content of the core of the wood to any constant value by the temperature gradually decreases while repeating this. In the wood drying apparatus using microwaves of the present invention, a gap having a predetermined width is formed between the side walls of the wood stacked on the pallet and the side walls inside the drying chamber, and the gap between the walls of the drying chamber in the gap is formed. At the height position, the steam pipe is folded at both ends in the longitudinal direction, is circulated along the inner side wall so as to progress from the inside to the outside in a meandering manner, and sprays steam into the drying chamber, At the mid-height position on both sides of the outside of the drying room, a fan motor that circulates the air inside the drying room inside the waterproof cover and a microwave transmitter that radiates microwaves are placed next to each other at different heights. motor,
A number of heating units each having a microwave transmitter and a radiating fan as one unit are arranged in a staggered manner, and the fan motor extends the tip of the fan motor shaft almost to the vicinity of the stacked wood, and a propeller is provided at the tip of the fan motor shaft. The fan is fixed.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A wood drying cabinet used in the microwave drying method of the present invention will be described with reference to the drawings. As shown in the front view of FIG. The drying machine 2 comprises a drying chamber 2 and the machine chamber 1 is provided in a rectangular shape on one side of a horizontally long rectangular parallelepiped, and the drying chamber 2 is partitioned by the other side of the horizontally long rectangular parallelepiped by the machine room 1 and a partition. The entire inner wall excluding the chamber 1 is formed of a heat insulating material, and as shown in the side view of FIG. 1 (b), an opening / closing door 3 is provided on the entire horizontal end face, and the drying chamber 2 is closed by closing the opening / closing door 3. A closed space is formed therein.

As shown in the plan view of FIG. 2, a water supply startup 4, a water supply unit 5, a soft water unit 6, a chemical injection device 7, and a boiler 8 are provided inside the machine room 1, respectively.
A humidifier 9 (supercharger) that supplies steam to a steam pipe 10 described below, through which steam is produced,
A blower device 11 for exchanging the outdoor air while exchanging heat with the air inside the drying chamber 2; and a power receiving panel 12 for distributing electricity to the water supply unit 5, the soft water unit 6, the chemical injection device 7, and the boiler 8, respectively. And the power receiving board 12,
Blower device 11, fan motor 13, heat dissipation fan 1
4. An operation panel 16 for controlling the microwave transmitter 15.

As shown in FIG. 2, a steam pipe 10 is provided inside the drying chamber 2, and a supply port is connected to the humidifier 9 (supercharger) and a discharge port is connected to the boiler 8. As shown in the vertical side view of FIG. 4, a circulation pipe is provided at an intermediate height position of the inner side wall. A gap space having a predetermined width is formed between the timber stacked on the pallet and the side wall, and the steam pipe 10 is located at an intermediate height of the inner wall of the drying chamber 2 as shown in FIG. Circulation piping is provided along the inner side wall so that water vapor is sprayed into the drying chamber 2 so that the drying chamber 2 is folded back at both ends in the longitudinal direction and travels from the inside to the outside in a meandering manner. Also,
A spray spray (not shown) is plumbed along the steam pipe 10 so that water can be sprayed.

As shown in FIG. 2, a fan motor 13, a microwave transmitter 15, and a radiating fan 14 are provided in a waterproof cover 17 at an intermediate height position on both outer side walls of the drying chamber 2.
As shown in FIG. 4, a large number of heating units each having a plurality of are arranged in the longitudinal direction in a staggered manner with the steam pipe 10 interposed therebetween. The heating unit is shown in FIG.
As shown in the electric system diagram of FIG. 2, a fan motor 13 for circulating air in the drying chamber 2 and a microwave transmitter 15 for irradiating microwaves are arranged adjacent to each other at different heights. The tip of the 13-axis is extended to near the stacked wood, and the propeller fan 18 is fixed to the tip of the 13-axis fan motor to perform microwave stirring and circulation ventilation. Further, as shown in the right side sectional view of FIG. 5, a curved wind direction plate 19 for promoting air circulation is provided in the upper and lower corners of the drying chamber 2 along the longitudinal direction. Therefore, by driving the fan motor 13, the propeller fan 18 rotates to blow the air on the steam pipe 10 side to the stacked wood side and circulate the air. Can pass through.

The method of drying wood using microwaves according to the present invention comprises sequentially controlling a humidification mode, a drying mode, and a cooling mode. Hereinafter, this will be described. 3 is opened, the stacked wood is conveyed into the drying chamber 2 and the stacked wood is stored in the drying chamber 2, and the opening / closing door 3 is closed to close the drying chamber 2. Next, start the humidification mode control,
The humidifier 9 (supercharger) is turned on to spray high-temperature steam from the steam pipe 10 into the drying chamber 2 to increase the temperature and humidity in the drying chamber 2 so that the temperature in the drying chamber 2 becomes a constant temperature, for example. When the temperature reaches 80 ° C., the process shifts to the drying mode control. At this time, since the drying chamber 2 is performed in the same manner as ordinary steam drying, the temperature in the drying chamber 2 can be rapidly increased.

The drying mode control is a combination of the conventional steam drying and the microwave heating. The temperature control of the drying chamber 2 is performed by turning on / off the humidifier 9 (supercharger) by spraying / stopping the high-temperature steam. The drying of the wood is performed by turning on / off the microwave transmitter 15 to start / stop the microwave heating. That is, when shifting to the drying mode control, the moisture meter inserted into the wood measures the moisture gradient between the core and the surface of the wood, and when the moisture gradient is equal to or more than an arbitrary set value, the microwave transmitter 15 is turned on. Microwaves are generated, and the water inside the wood is heated by microwave irradiation to generate water vapor. In that case, the microwave irradiation time can be set arbitrarily in seconds, and continuous irradiation is not performed.
Irradiation for 2 seconds, measurement of water content is started after the microwave is stopped, then measurement of water content is stopped, and microwave irradiation is performed. Such ON / OFF control of the microwave transmitter 15 is repeated, and when the humidity of the drying chamber 2 rises due to the water vapor from the wood due to the microwave irradiation, the blower device 11 is turned ON and the drying chamber 2 is turned on. The air inside the refrigerator is discharged outside and the outdoor air is introduced into the drying chamber 2 to reduce the humidity.
As a result, the temperature in the drying chamber 2 decreases, and the humidifier 9 (supercharger) is turned on to spray high-temperature steam into the drying chamber 2 from the steam pipe 10 to increase the temperature in the drying chamber 2. . If the repetition of the upper and lower limits of the temperature and the humidity is remarkable in the drying mode control, the repetition program is easily operated to create a pattern repetition mode, and the time interval of the temperature and the humidity control is set in minutes.

By repeating the above, when the water content of the wood core becomes equal to or less than an arbitrary constant value, the humidifier and the microwave transmitter are stopped. Therefore, in the drying mode control, ON / OFF of the microwave transmitter 15, ON / OFF of the humidifier 9 (supercharger), and ON of the blower device 11 are performed.
Since / OFF is also performed at the same time, the moisture content of the wood core can be quickly set to an arbitrary constant value. When the moisture content of the wood core reaches an arbitrary constant value, the cooling mode control is started at the end of the drying mode control.

In the cooling mode control, when the drying chamber 2 has a humidity equal to or higher than the set humidity, the blower device 11 is turned on to exchange heat while exchanging heat between the inside air of the drying chamber 2 and the outdoor air to lower the humidity. If the temperature of the chamber 2 is lower than the set humidity, the water spray is turned on to lower the temperature by the heat of vaporization. Although the temperature decreases due to the heat of vaporization due to the evaporation of moisture, the humidity also increases. At the same time, when the drying chamber 2 becomes higher than the set humidity, the blower device 11 is turned on to turn on the air inside the drying chamber 2 and the outdoor air. The water content of the wood core can be maintained at an arbitrary constant value by exchanging heat while exchanging heat to lower the humidity and gradually lowering the temperature while repeating this.

[0013]

According to the method for drying wood by microwave of the present invention, steam drying and microwave irradiation can be performed simultaneously, the moisture content of the wood core can be quickly brought to a constant value, and water spray can be performed. By doing so, the temperature can be lowered while maintaining a constant humidity, and the moisture content of the wood core can be kept constant. The microwave wood drying apparatus of the present invention can perform microwave irradiation during drying in a drying chamber to dry the wood as it is.

[Brief description of the drawings]

FIG. 1 is a (a) front view and (b) a right side view of a wood drying apparatus used in the present invention.

FIG. 2 is a plan view of a wood drying apparatus used in the present invention.

FIG. 3 is an electrical diagram of a wood drying apparatus used in the present invention.

FIG. 4 is a vertical sectional view of a wood drying apparatus used in the present invention.

FIG. 5 is a right side sectional view of a wood drying apparatus used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Machine room 2 Drying room 3 Opening / closing door 4 Water supply start-up 5 Water supply unit 6 Soft water unit 7 Chemical injection device 8 Boiler 9 Humidifier 10 Steam pipe 11 Blower device 12 Power receiving board 13 Fan motor 14 Radiation fan 15 Microwave transmitter 16 Operation Panel 17 Waterproof cover 18 Propeller fan 19 Wind direction board

Claims (2)

[Claims] 1. A method for drying wood using microwaves, comprising sequentially performing humidification mode control, drying mode control, and cooling mode control, wherein the humidification mode control is performed when the temperature of the drying chamber is equal to or lower than a set value. Turn ON to perform temperature control using high-temperature steam.Drying mode control, when the moisture gradient between the wood core and the surface is equal to or greater than an arbitrary set value, turns on / off the microwave transmitter to control the microwave into the drying chamber. When the humidity in the drying room reaches a certain level or more, the blower is turned on to discharge the air inside the drying room to the outside and introduce outdoor air into the drying room to reduce the humidity. If the temperature drops below the set value, turn on the humidifier to control the temperature.If the water gradient between the wood core and the surface falls below the set value, the humidifier and microwave transmitter Stop the cooling module When the humidity in the drying chamber is equal to or higher than the set value, the cooling mode control turns on the blower device and exchanges heat while exchanging the air in the drying chamber with the outdoor air to reduce the humidity. When the humidity in the drying chamber falls below the set value, spray
A method for drying wood using microwaves, characterized in that the temperature is lowered by heat of vaporization when turned on, and the temperature is gradually lowered while repeating the process so as to set the moisture content of the wood core to an arbitrary constant value. 2. A space having a predetermined width is formed between the side walls of the wood stacked on the pallet and the side wall in the interior of the drying chamber. The pipe is folded at both ends in the longitudinal direction and is circulated along the inner side wall so as to travel from the inside to the outside in a meandering manner, so that steam is sprayed into the drying chamber. In the middle height position, a fan motor that circulates air in the drying room inside the waterproof cover and a microwave transmitter that irradiates microwaves are placed adjacent to each other at different heights, and the fan motor and microwave transmitter A large number of heating units having a radiating fan as one unit are arranged in a zigzag pattern, and the fan motor extends the tip of the fan motor shaft almost to the vicinity of the stacked wood. Wood drying apparatus by microwaves, characterized in that securing the propeller fan.