JPH0252981A - Microwave drying device for granular body - Google Patents

Abstract

PURPOSE:To permit efficient microwave drying of granular body to be treated which is provided with a small microwave loss coefficient by a method wherein a mixer, consisting of microwave absorbing material and mixing the granular body to be treated, is provided in a vessel receiving the granular body to be treated. CONSTITUTION:A mixer or vanes 17, for example, which mixes granular body 10 to be treated, is provided in a vessel 18 while the vanes 17 are constituted of a microwave absorbing material or a material having a large microwave loss coefficient such as the ceramics of SiC, SiN, ferrite material for example. When an electric power source is impressed on a microwave oscillating source 1 to oscillate microwaves and the microwaves are sent into an oven 7 through a waveguide 2 to project them against the granular bodies 10 to be treated and the mixer or the vanes 17, the vanes 17 absorb the microwaves and generate heat. At the same time, the vanes 17 generating heat are driven by a motor 20 to rotate and mix the granular body 10 and, therefore the generated heat is transferred to the granular body 10 and/or contacted directly with the granular body 10 to be treated.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a microwave drying device for powder and granular materials.

(Prior art) In recent years, in fields such as the chemical industry, drug manufacturing industry, food industry, and waste treatment, large amounts of powder, sour, or granular materials containing a large amount of moisture have been produced due to storage and processing techniques of goods. There is an increasing demand for drying to a moisture content below .

In this case, a microwave drying device for powder and granular material is used that uses microwaves to dry the material, but an example of this type of device for discontinuous processing has conventionally been constructed as shown in Fig. 5. It becomes.

In the figure, 1 is a microwave oscillation source such as a magnetron or klystron, 2 is a waveguide, 3 is a fixing plate that fixes the air sealing plate 4, 5.8 is a packing, and 6 is a microwave oscillation source in the microwave oven 7. A stirrer fan for radio stirring is attached to the ceiling, 9 is a door that can be opened and closed on the side of the oven 7, 10 is a powder to be processed placed in a container 18, 11 is a vacuum pump, and 12 is a vacuum In total, 13 is an exhaust pipe, 14 is a valve, and 15 is a leak valve.

Using such a device, the powder and granular material 10 to be treated is heated and
To dry, the container 18 containing the powder and granular material 10 to be treated is
After placing the oven 7 in the oven 7, the vacuum pump 11 is operated to reduce the pressure inside the oven 7 and create a vacuum state.

Thereafter, when the leak valve 15 is adjusted to reach a predetermined degree of vacuum, microwave power is generated from the microwave oscillation source 1 and irradiated onto the powder and granular material 1.0 to be processed. For example, if it is desired to process the granular material 10 to be processed at 40° C., the leak valve 15 may be adjusted to maintain the degree of vacuum in the oven 7 at approximately 55 Torr.

(Problems to be Solved by the Invention) However, the conventional device as described above still has the following problems to be improved.

(1) When the microwave loss coefficient of the powder to be treated 10 is small, the powder to be treated 10 itself hardly generates heat;
Purpose 9 Do not raise the temperature to the temperature.

(2) Powder to be treated 10 with a small microwave loss coefficient
When drying the water contained in water, if the water content is about 10% or more, the water itself will absorb microwaves and evaporate as the temperature rises, but if the water content is less than 10%, most of the microwaves will be absorbed. This will result in insufficient drying.

In addition, as a conventional technique for continuous processing, Japanese Patent Application Laid-Open No. 57
There is an invention described in Japanese Patent No.-31776, but it has the same problem as above.

An object of the present invention is to provide a microwave drying apparatus for powder and granular materials that can efficiently dry powder and granular materials having a small microwave loss coefficient using microwaves.

[Structure of the Invention] (Means for Solving the Problem) This invention provides a method in which a stirrer made of a microwave absorbing material and for stirring the powder and granular material to be treated is provided in a container in which the powder and granular material to be treated is stored. This is a microwave drying device for powder and granular materials.

(Function) According to the present invention, even powder particles to be treated with a small microwave loss coefficient can be heated by a stirrer that absorbs microwaves and generates heat, or come into contact with the stirrer to evaporate water. It can be efficiently dried to near absolute dryness.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The microwave heating device according to the present invention is constructed as shown in FIG. 1, and the same parts as in the conventional example (FIG. 5) are given the same reference numerals.

That is, one side of the microwave oven 7 having a cylindrical shape or a rectangular parallelepiped shape has 1. A door 9 is provided which can be opened and closed to take in and take out the granular material 10 to be processed. Moreover, the oven 7 and the waveguide 2 are installed on the ceiling of the oven 7.
An air sealing plate 4 made of a dielectric material with low microwave loss and a fixing plate 3 for fixing the air sealing plate 4 are provided. Incidentally, between the door 9 and the oven 7 and between the air sealing plate 4 and the oven 7, a bar socket 5.8 is naturally used to prevent air leakage.

A microwave oscillation source 1 is connected to one end of the waveguide 2, and the microwave power generated by the microwave oscillation source 1 is introduced into the oven 7 via the waveguide 2 and The granular material 10 and a stirrer described below are irradiated.

Furthermore, one support stand is provided at the bottom of the oven 7,
A container 18 in which the granular material 10 to be processed is accommodated is placed on the upper surface of the support base 19 . The material of this container 18 may be either metal or dielectric, but in order to improve the microwave absorption efficiency, dielectric is preferable, and it is also made of a material with a small microwave loss coefficient (for example, quartz, Teflon, polypropylene, etc.) or a large material. Any material (for example, ceramic such as 5iCSSiN ferrite material) may be used.

Further, in the container 18, a stirrer, for example, a blade 17, for stirring the powder and granular material 10 to be processed is provided. It is connected to a rotating device, such as a motor 20, through it. In this way, the blades 17 are driven by the motor 20 and are rotatable.

The blade 17 is made of a microwave absorbing material, that is, a material with a large microwave loss coefficient, for example, a ceramic such as a 5iC1SLN ferrite material.

The powder and granular material 10 to be treated includes anything from fine powder to beads, etc., and can have any shape such as spherical, polygonal, circular/prismatic, hollow, etc., and the size can range from about 0.1 μm to several cm. Yes, the size, shape, and number of stirrers are selected depending on the shape and size. In other words, the stirrer should be in good contact with the granular material.

Furthermore, a vacuum pump 11 is connected to the other side of the oven 7 via an exhaust pipe 13 and a valve 14. This vacuum pump 11 is for exhausting the air in the oven 7 and the steam generated from the granular material 10 to be processed. A vacuum gauge 12 and a leak valve 15 are connected to the exhaust pipe 13. The vacuum gauge 12 is for checking the degree of vacuum inside the oven 7, and the leak valve 15 is for checking the degree of vacuum inside the oven 7. This is to create a predetermined pressure.

Next, in order to dry the granular material 10 to be treated using the apparatus of the present invention, first, the container 18 containing the granular material 10 to be treated is placed in the oven 7 with the door 9 opened. and place it on the support stand 19. Thereafter, power is applied to the microwave oscillation source 1 to oscillate microwaves, and the microwaves are sent into the oven 7 through the waveguide 2 and the powder and granular material to be processed 1
0 and the blade 17, which is a stirrer, are irradiated. Then, the blade 17 absorbs the microwave and generates heat.

At the same time, the blades 17 that generate heat are driven by the motor 20 and rotate to agitate the powder and granular material 10 to be treated, so that the generated heat is transmitted to the powder and granular material 10 to be treated, and also comes into direct contact with the powder and granular material 10 to be treated. I will do it. As a result, the powder to be treated 10
The water is evaporated and dried.

In addition, although the explanation so far has been based on heating by reducing the pressure and lowering the boiling point, it goes without saying that the same problem will not arise even if it is applied to microwave heating at normal atmospheric pressure.

(Modified Examples) Figures 2 to 4 show modified examples of this invention.
The same effects as in the above embodiment can be obtained.

First, in the case of FIG. 2, contrary to the above embodiment, the blade 17 is fixed and the container 18 is rotated by driving the support base 21 with a motor 22. In this case as well, as a result, the granular material 10 to be treated in the container 18 is directly stirred by the heat-generating stirrer, and heated and dried.

In addition, in the case of Fig. 3 and Fig. 4, the apparatus is suitable for continuously drying the powder and granular material 10 to be treated, and in particular, it is suitable for continuously drying the powder and granular material with a moisture content of 20% or more to a few percent or less. It is suitable for drying. That is, the inside of the microwave oven 23 is divided into a plurality of rooms (for example, room A and room B) by at least one partition plate 24, and in each room A and B, the microwave oscillation source 1 is installed outside the ceiling through a waveguide. 2, and a star fan 6 is installed inside the ceiling. Partition plate 2
4 also serves to prevent water vapor from going to the left chamber during operation.

Inside the oven 23 is a long dielectric container 2 with a U-shaped cross section.
5 is disposed, and an inlet 26 for the granular material 10 to be processed is provided penetrating through the ceiling of the oven 23 corresponding to one end of the container 25 . Although not shown, the other end of the container 25 is provided with a discharge port for the granular material 10 to be processed. The powder and granular material 10 to be treated is introduced into the container 25 from the inlet 26, and screws 27a and 27b, which are stirrers for stirring the powder and granular material 10 to be treated, are further provided. , 27b are rotationally driven by a motor 29 outside the oven 23.

In this case, in the chamber A where the screw 27a is located, the powder and granular material 10 to be treated has a high moisture content, for example, 20% or more, so the water content of the granular material 10 to be treated is absorbed by the microwave. I get a fever. Therefore, the material of the screw 27a does not need to absorb microwaves, and is made of a low-loss dielectric such as ceramic or resin.

On the other hand, in the B chamber where the screw 27b is located, the water content of the granular material 10 to be processed is low, so the material of the screw 27b is made of a microwave absorbing material. or,
The shaft 28 is made of metal or dielectric. 30 in the figure is an exhaust port.

When drying the powder and granular material 10 to be treated, the powder and granular material 10 to be treated is put into the container 23 from the inlet 26, but inside the chamber A, the water inside the powder and granular material 10 itself is heated by microwaves. Then, while evaporating, it is moved to the left by the action of the screw 27a. In the B chamber, the granular material 10 to be processed directly comes into contact with a heat-generating screw 27b made of a microwave absorbing material and is heated, and the moisture itself comes into contact with this screw 27b and evaporates, thereby performing drying.

Although the apparatus suitable for this continuous drying process is of a so-called horizontal type in FIGS. 3 and 4, it may be of a vertical type. In any case, this continuous drying treatment apparatus is suitable when the moisture content before treatment is relatively high (approximately 20% or more), and can be reduced to several percent or 1% or less after treatment.

In the above embodiments and modified examples, the blades 17 and the screws 27a, 27b were used as the stirrer, but the stirrer is not limited to these, and the stirrer is not limited to these. It may be one with an absorbent plate or film attached thereto, or one with another protective film applied to its outer surface so as not to contaminate the granular material 1o to be treated.

[Effects of the Invention] As explained above, according to the present invention, the powder to be treated in the container is stirred by the stirrer made of a microwave absorbing material, so that the powder to be treated has a small microwave loss coefficient. Even when drying a drying body, moisture evaporates when it comes into contact with a stirrer heated by microwaves, significantly improving drying efficiency.

As a result, even powder particles to be treated that absorb little or no microwaves can be dried to near absolute dryness. Furthermore, since the stirrer itself is a heat generating material, no extra parts are required and the apparatus can be constructed relatively easily.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a microwave drying device for powder and granular materials according to an embodiment of the present invention, FIGS. 2 and 3 are cross-sectional views showing modified examples of the present invention, and FIG. FIG. 5 is a sectional view showing a conventional microwave drying apparatus for powder and granular materials. DESCRIPTION OF SYMBOLS 1... Microwave oscillation source, 7... Microwave oven, 10-" Powder to be processed, 17.27a, 27b...
- Stirrer, 18.23... Container. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] A microwave drying device for powder and granular material, comprising a microwave oscillation source, a microwave oven connected to the microwave oscillation source, and a container disposed within the oven and containing the powder and granular material to be treated, A microwave drying apparatus for powder or granular material, characterized in that a stirrer made of a microwave absorbing material and for stirring the powder or granular material to be treated is provided in the container.