JPH0789025B2 - Microwave dryer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a microwave dryer.

(B) Prior Art Japanese Patent Application No. 2-2229 discloses a microwave drying device for microwave-drying an object to be dried by applying microwaves to a drying chamber to which the object to be dried is supplied. In this case, compressed air is supplied to the drying chamber, and air containing water vapor generated from the material to be dried during microwave drying is forcibly discharged outside the drying chamber.

However, if the compressed air itself supplied to the drying chamber contains a large amount of water, there is a problem that the dried material to be dried will absorb moisture again.

Further, when the fine powder generated from the material to be dried adheres to the microwave permeable protective cover that covers the microwave feeding port of the drying chamber, and the fine powder absorbs water vapor before discharge, the microwave is The fine powder is carbonized by being concentrated on the powder and a microwave discharge phenomenon occurs.

(C) Problem to be Solved by the Invention The present invention is intended to prevent the dried object to be dried again from absorbing moisture, and to suppress the occurrence of microwave discharge in the microwave permeable protective cover. Is.

(D) Means for Solving the Problems The present invention is directed to a drying chamber to which a granular or powdery material to be dried is supplied, a microwave power feeding port provided in the drying chamber, and a microwave transmitting member covering the power feeding port. And a microwave supply means for supplying a microwave for drying the object to be dried into the drying chamber through the power supply port.
The discharging means discharges air in the drying chamber, and the compressed drying air supplying means supplies compressed drying air into the drying chamber so as to blow it onto the protective cover.

(E) Action Compressed air is supplied to the drying chamber, and air containing water vapor generated from the material to be dried during microwave drying is forcibly discharged outside the drying chamber. In this case, the compressed air is in a dry state, and it is possible to prevent the material to be dried, which has been dried, from absorbing moisture again.

Further, the compressed air is blown onto the microwave transparent protective cover that covers the microwave power supply port, and the generation of microwave discharge due to the adhesion of fine powder to the cover is eliminated.

(F) Embodiment FIG. 1 shows the structure of a microwave drying apparatus according to an embodiment of the present invention. The apparatus comprises a drying apparatus main body 1 and its peripheral mechanism.

The drying apparatus main body 1 is provided with a cylindrical drying chamber 3 having an upper lid 2 which can be opened and closed as a main part. A supply pipe 4 is connected to the upper left part of the drying chamber, and the tip of the supply pipe is a storage tank 6 for storing a granular or powdery material 5 to be dried.
It has reached inside. The storage tank is below the drying chamber 3. Examples of the material to be dried 5 include resin pellets containing glass, rice, and chemical powder particles. The resin pellets are molded after being melted. If the resin pellets are dried to a water content of, for example, 0.05% or less prior to this melt molding, the subsequent molding will be well performed.
The normal water content of such resin pellets is, for example, 0.2%
Is. In this embodiment, the resin pellets containing glass are the material to be dried.

A suction hopper 7 is connected to the center of the upper lid 2 of the drying chamber 3, and a filter 8 is detachably arranged in the suction hopper 7. The filter has a mesh smaller than the material diameter of the material to be dried 5.

A poppet valve 9 is provided in the hopper 7 above the filter 8, and the poppet valve 9 is provided.
A suction blower 11 is connected to the above-mentioned suction hopper 7 at the upper part of the above through an intake pipe 10. In this case, when the suction blower 11 is driven with the poppet valve 9 being driven to open,
The suction action of the suction blower 11 reaches the suction pipe 10, the suction hopper 7, and the supply pipe 4, and the material to be dried 5 in the storage tank 6 is sucked and reaches the drying chamber 3 through the supply pipe 4.
When the material to be dried 5 reaches the material to be dried 3, it falls into the drying chamber due to its own weight and accumulates therein.

In the drying chamber 3, microwaves are supplied to the inside from the magnetron 12 through the waveguide 13 and the microwave feeding port 14 of the upper lid 2. The power supply port 14 is covered with a microwave transparent protective cover 15.

The bottom wall of the drying chamber 3 is provided with a stirrer 17 that is driven by a motor 16 and stirs the material to be dried 5. A level sensor 18, a temperature sensor 19, and a compressed dry air supply device 20 that detect whether or not a predetermined amount of the material to be dried 5 has accumulated in the drying chamber 3 are arranged on the side wall.

The compressed dry air supply device 20 includes a compressor 21 that generates compressed air, a compressed air pipe 22 that connects the compressor and the drying chamber 3, and a compressor that is provided in the middle of the pipe and passes through the pipe. It is composed of a moisture removing device 23 for removing moisture contained in air and an intake valve 24. The water removing device 23 is composed of a bundle of a large number of hollow fibers 25 as shown in FIG. 2. The hollow fibers 25 themselves are made of polyimide and have an outer diameter of 0.5 m.
m, inner diameter is 300 μm. Such a hollow fiber 25 is
The water vapor contained in the compressed air sent from one end to the inside is permeated very well from the hollow fiber membrane to the outside as indicated by arrow V, and the dried compressed air is discharged from the other end. A method for obtaining compressed dry air in this way is called a gas separation membrane method.
As the water removing device 23 as described above, a device manufactured by Ube Industries, Ltd. can be used, and in this case, the compressed dry air is in a dry state where the dew condensation temperature is minus several tens of degrees.

An exhaust valve 26 is provided on the upper lid 2 of the drying chamber 3.

As described above, the material to be dried 5 accumulated in the drying chamber 3 is agitated by the agitator 17 while its upper surface is aligned with a horizontal plane,
In this state, the level sensor 18 detects the supply amount of the material to be dried 5 into the drying chamber 3, and when the supply amount reaches a predetermined amount, the stirring by the stirring member 17 is continued and the magnetron is continuously supplied. 12 is drive-controlled and the to-be-dried material 5 is microwave-dried. At this time, the magnetron 12 is drive-controlled so that the temperature of the material to be dried 5 detected by the temperature sensor 19 is maintained at a desired temperature.

Further, the compressor 21 is driven and the intake valve 24 and the exhaust valve 26 are opened, so that the steam generated when the material to be dried 5 is dried by the microwave is discharged together with the compressed dry air from the compressed dry air supply device 20 into the exhaust valve 26. Is discharged to the outside through. In this case, the air supplied into the drying chamber 3 is compressed dry air and is in a dry state.
Does not absorb moisture again.

The compressed dry air is blown onto the protective cover 15 when being supplied into the drying chamber 3. This is achieved by inclining the tip of the compressed air pipe 22 of the compressed dry air supply device 20 so as to face the protective cover 15.
As a result, it is possible to prevent the fine powder of the material to be dried 5 from adhering to the protective cover 15 and carbonizing it during microwave drying to cause microwave discharge.

A discharge valve 27 is provided on the right bottom of the drying chamber 3,
The discharge valve is opened when discharging the material to be dried 5 that has been dried. The discharge valve 27 is connected to another suction hopper 28 through a transfer pipe 29. Such suction hopper
Similarly to the suction hopper 7, a filter 30 having a mesh smaller than the material diameter of the material to be dried 5 is arranged also at 28, and a poppet valve 31 is provided above the filter 30. The suction blower 11 is also connected to the suction hopper 28 above the poppet valve 31 via an intake pipe 32. In this case, when the blower 11 is driven with the discharge valve 27 and the poppet valve 31 opened, the intake action of the blower 11 reaches the transfer pipe 29 via the intake pipe 32 and the suction hopper 28, and the drying chamber 3 To be dried 5
Passes through the transfer pipe 29 and reaches the suction hopper 28. When the material to be dried 5 reaches the suction hopper 28, it falls into the hopper by its own weight.

An open / close valve 33 is provided at the lower end of the suction hopper 28. When the opening / closing valve 33 is closed, the intake action works to drop the material 5 to be dried in the suction hopper 28, and the material 5 to be dried is accumulated in the suction hopper 28, while the opening / closing valve 33 is opened. The material to be dried 5 thus accumulated falls downward and reaches the next-stage processing section, and the material to be dried 5 that is dried in this processing section, that is, the resin pellets, is melt-molded.

(G) Effect of the Invention According to the microwave drying apparatus of the present invention, compressed air is supplied to the drying chamber, and air containing water vapor generated from the material to be dried during microwave drying is forcibly discharged to the outside of the drying chamber. In the configuration, since the compressed air is in a dry state, it is possible to remarkably prevent the dried material to be dried from absorbing moisture again.

Furthermore, since the compressed air is blown onto the microwave permeable protective cover that covers the microwave power feeding port, it is possible to prevent the generation of microwave discharge due to the adhesion of fine powder to the cover.

[Brief description of drawings]

FIG. 1 is a sectional view of a microwave drying apparatus according to an embodiment of the present invention,
FIG. 2 is a perspective view of the same main part. 3 ... Drying room, 12 ... Magnetron, 14 ... Microwave power supply port, 15 ... Microwave permeable protective cover, 20 ... Compressed dry air supply device, 26 ... Exhaust valve.

Claims (1)

[Claims] 1. A drying chamber to which a granular or powdery material to be dried is supplied, a microwave power feeding port provided in the drying chamber, a microwave transparent protective cover covering the power feeding port, and the material to be dried. Microwave supply means for supplying microwaves for microwave drying into the drying chamber through the power supply port, discharging means for discharging air in the drying chamber, and spraying compressed dry air onto the protective cover. A microwave drying device comprising compressed dry air supplying means for supplying into the drying chamber.