JPH0250073A - Method and device for auxiliary drying in microwave drying - Google Patents

Abstract

PURPOSE:To improve thermal efficiency, unnecessitate a separate heat source and reduce the cost of drying by a method wherein atmosphere, including heat dissipated from a substance to be dried, is utilized by circulating it. CONSTITUTION:When a substance 9 to be dried is entered into a drying chamber 1 and is preheated by microwave, much amount of moisture is stagnated on the surface of the substance 9 while becoming water drips 27. The moisture reduces the absorbing efficiency of the microwave and deprives much amount of evaporation heat upon evaporation whereby total thermal efficiency is deteriorated. In order to prevent the deterioration, atmosphere, heated by the dissipated heat of the heated substance 9 to be heated, is sucked by a ventilating device 23 through a suction port 15 and is discharged to send it to injection ports 19 through ducts 17b and inject warm-air through respective injection ports 19. The warm-air, injected through the injection ports 19, is blown against the surface of the substance 9 to be dried and blows off the moisture stagnating on the surface of the substance 9 or promotes the evaporation of the same. Accordingly, drying time may e shortened and both of the surface and the internal part of the substance 9 may be dried uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an auxiliary drying method and apparatus for microwave drying.

<Prior Art> Conventionally, methods for drying materials with high moisture content such as plaster statues include methods of drying by blowing hot air and methods of heating with a burner.

According to these drying methods, the drying time is long,
It also has drawbacks such as the formation of a moisture condensation layer just below the surface. Therefore, a method that uses microwave irradiation has been devised as a method that allows drying in a shorter time than the above-mentioned method and does not cause a moisture condensation layer.

<Problems to be Solved by the Invention> However, in the conventional method using only microwave irradiation, the water seeping from inside accumulates on the surface of the object to be dried as water droplets, and after the microwave irradiation is finished, the water droplets on the surface cannot be regenerated. It may absorb moisture and cause uneven dryness. Furthermore, in order to completely evaporate the water droplets on the surface simply by irradiating microwaves, a long period of microwave irradiation is required, leading to problems such as high costs and decreased productivity.

Means for Solving the Problems> The present invention for solving the problems described above includes a closed drying chamber 11 containing an object 9 to be dried, and irradiating the object 9 with microwaves. In the method of performing drying treatment,
The indoor atmosphere heated by the heat dissipation from the microwave heating of the material to be dried 9 is recovered, and the atmosphere is transferred to the material to be dried in the room 9.
In the drying chamber 1 in which microwaves are irradiated into the interior of the drying chamber 1, the interior of the drying chamber 1 is heated by heat dissipation due to microwave heating of the material 9 to be dried. An inlet 15 for sucking in the atmosphere and a plurality of injection ports 19 for ejecting the inhaled atmosphere are provided, a wind tunnel 17 is installed to connect the inlet 15 and the injection ports 19, and a wind tunnel 17 is installed between the inlet 15 and the injection ports 19 of the wind tunnel. It is characterized by having an air blower 23 attached to it.

Effect> The temperature of the material to be dried 9 placed in the drying chamber 1 rises due to microwave irradiation, and the moisture contained inside turns into water vapor and condenses on the surface. As the temperature of the material to be dried 9 increases, the temperature of the surrounding atmosphere inside the drying chamber 1 also increases. The atmosphere whose temperature has increased is recovered from the suction port 15, and the atmosphere passes through the wind tunnel 17 and is discharged from the injection port 19 by the blower device 23.

The dew condensation on the surface of the object to be dried 9 is accelerated to vaporize by the atmosphere injected from the injection port 19.

<Example> An example of the present invention will be described in detail below based on the drawings. The drying chamber 1 has an inner surface made of a material that reflects microwaves, and a waveguide 3 that guides microwaves is connected to the top surface to form a microwave irradiation window 5. A microwave generator 7 is attached to the end.

The material to be dried 9 is placed on a drying table 1 installed in the center of the drying chamber 1.
The drying table 11 is supported by a rotating shaft 13 protruding from the bottom of the drying chamber 1.

When the material to be dried 9 is heated and dried by microwave irradiation,
The atmosphere in the drying chamber 1 is heated by heat radiation from the material to be dried 9, and the chamber is filled with water vapor due to drying. An atmosphere saturated with water vapor hinders the drying of the material to be dried 9.
It is sucked in through the suction port 15 provided in the ceiling. A punching metal having a microwave shielding effect is attached to the inlet 15 to prevent microwaves from leaking to the outside of the drying chamber l. The shielding effect of punching metal is determined by the incident power density (= Pi) and the power density after passing (=
Pt) is -40 [dB] > 10 log (
P t/P i) is used.

A wind tunnel 17 is connected to the suction port 15 from the outside of the drying chamber 1. Further, a plurality of injection ports 19 are provided on the inner surface of the drying chamber 1, and a shield pipe 21 is provided on the outside of the injection ports 19.
Each one is placed towards the inside of the box.

Similar to the above-mentioned punching metal, the shield vibe 21 also prevents microwave leakage from the injection port 19, so the relationship between the incident power density and the power density after passing is -40 [d
B ] > 10 log(P t/P i).

The above solid intake port 15 and injection port 19 are connected by a wind tunnel 17, and the injection port 1 connects each injection port 19.
It is divided into a wind tunnel 17b on the 9 side and a wind tunnel 17a on the inlet 15 side. A blower device 2 is installed between each wind tunnel 17a and 17b.
3 is installed. The air blower 23 has an inlet 15
The atmosphere inside the drying chamber 1 is sucked in from the drying chamber 1, and hot air is sent to each injection port 19. The sent hot air is ejected from the injection port 19 and hits the surface of the object to be dried 9, thereby promoting drying of the surface. Also, if the jetting pressure is increased, the jetting pressure will cause the material to be dried to
The water droplets 27 generated on the surface can be blown away, and it is also possible to reduce the heat of evaporation of the water droplets and increase thermal efficiency.

If a filter is installed in the wind tunnel 17 or the blower 23, it is possible to remove dust and the like in the atmosphere.

Moreover, if a dehumidifier is provided in the wind tunnel 17, dehumidified wind can be blown onto the material to be dried 9, thereby further promoting drying.

A drying method using the drying apparatus described above will be described below.

A material to be dried 9 having a high moisture content, such as gypsum, is placed in the drying chamber 1. By adding residual heat using microwaves,
The moisture in the material to be dried 9 actively evaporates, forming water droplets 2 on the surface.
7, and a large amount of water remains. This water reduces the absorption efficiency of microwaves, and also takes away a large amount of heat of evaporation during evaporation, thereby reducing the overall thermal efficiency.

Therefore, the atmosphere warmed by the heat dissipation of the heated material 9 to be dried is absorbed and discharged from the suction port 15 by the blower 23, and the atmosphere is sent to the spout 19 through the wind tunnel 17b, and the atmosphere is heated from each spout 19. Spew out wind.

The ejected hot air is blown onto the surface of the material to be dried 9,
Blows away moisture accumulated on the surface or accelerates evaporation. Therefore, the drying time is shorter than in the past, and the surface and interior can be dried uniformly.

Furthermore, even if the heat of evaporation is taken away by the evaporation of water on the surface, it is replenished by the amount of heat possessed by the warm air, so there is little loss due to the heat of evaporation.

Any moisture that is blown away or drips down should be removed from the drying room l.
It is discharged from a drain 25 provided at the bottom of the tank. The drain 25 is opened and closed, and is closed in order to prevent microwave leakage during the drying process.

<Effects of the Invention> According to the method and apparatus of the present invention configured as described above,
Since the atmosphere containing hot air radiated from the material to be dried is circulated and utilized, the thermal efficiency is good, and since no side heat source is used, costs can be reduced.

Furthermore, by blowing warm air onto the surface of the object to be dried, the microwave dries the inside and the surface at the same time, making drying possible in a short time and preventing uneven drying due to re-absorption of water droplets on the surface. be able to.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of the drying chamber. 1: Drying room 9: Material to be dried 15: Inlet
17: Wind tunnel

Claims (1)

[Claims] 1) Putting the material to be dried (9) into the sealed drying chamber (1),
In the method of performing drying treatment by irradiating the object to be dried (9) with microwaves, recovering the indoor atmosphere heated by heat radiation due to microwave heating of the object to be dried (9),
An auxiliary drying method in microwave drying in which the atmosphere is sprayed onto the object to be dried (9) indoors to promote drying of the surface of the object to be dried (9). 2) in the drying chamber (1) into which microwaves are irradiated, an inlet (15) that sucks in indoor atmosphere heated by heat radiation from the microwave heating of the object to be dried (9);
A plurality of injection ports (19) for injecting the inhaled atmosphere are provided, a wind tunnel (17) is installed that connects the intake port (15) and the injection port (19), and the air intake port (15) and the injection port ( 19) is an auxiliary drying device for microwave drying equipped with a blower device (23).