JPS62194181A - Decompression drier and control method thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides heating using a microwave heater, and further,
The present invention relates to a vacuum drying device that dries kitchen waste and the like by reducing the pressure, and particularly to a vacuum drying device suitable for automatic operation and a method for controlling the same.

[Conventional technology]

Conventionally, an automatic drying method in a drying device is described in Japanese Patent Publication No. 112675/1983. In this method, the end of drying is determined based on the principle that the rate of decrease in temperature of the object to be dried changes depending on the humidity ratio of the object, that is, the temperature of the object. Such a conventional drying apparatus will be explained in detail with reference to FIG. 3. In the figure, 1' is a container containing the material to be dried 21, and 11 is an infrared lamp etc. installed inside the container 1'. The heater 12 is a fan that stirs the heat radiated from the heater 11 to equalize the internal temperature of the container 1' and also blows air. 13 is a temperature sensor such as a thermocouple that detects the temperature inside the container 1'. 7' is the control mechanism,
Output section 14. Comparison part 15. Processing section 16 and storage section 17
It consists of In such a configuration, the object to be dried A is dried by the following action.

That is, the temperature inside the container 1' is maintained at a constant temperature, and when the temperature inside the container 1' drops, the heater 11 is used to heat the container 1'. 2, when drying the material n to be dried while keeping the inside of the container 1' at a constant temperature, the humidity inside the container 1' gradually decreases. On the other hand, as described above, when the humidity inside the container 1' decreases, the integrated value of the on-time of the heater 11 inside the container 1' becomes smaller and becomes smaller than the set value. This set value is set to a value corresponding to a desired degree of drying, and when the integrated value continues for a certain period of time, the control mechanism 7' can determine that drying of the material n to be dried is complete, and the operation is stopped. I can do it.

[Problems to be Solved by the Invention] By the way, in the above-mentioned prior art, the heating device determines the completion of drying by focusing on the fact that the operating time of the heater changes depending on the humidity. , complex and precise control was required, such as calculating the operating time per unit time by 8I. Therefore, the manufacturing cost of the control mechanism 7' was likely to be high.

An object of the present invention is to provide a reduced pressure drying J'W1 and a control method thereof, which can reliably detect the end of drying with simple control.

[Means to solve the problem]

Vacuum drying equipment? In this case, the pressure inside the vacuum container is reduced by a pressure reduction means, and a microwave heater is used to heat the material to be dried using microwaves. By the way, when the pressure of the vacuum container is reduced to a low vacuum, the moisture contained in the material to be dried is sequentially evaporated by microwave heating, filling the vacuum container and being exhausted. At this time, the temperature of the gas in the vacuum container is dominated by the temperature of the water vapor contained in the atmosphere, and if the moisture content of the material to be dried decreases, the amount of evaporation of the moisture decreases. The atmospheric temperature within the reduced pressure container is dominated by the temperature of gases other than water vapor.

Since this gas other than water vapor is not directly heated by the microwave heater, the ambient temperature inside the reduced pressure container is lower than when it contains a large amount of water vapor. On the other hand, the temperature of the water vapor, that is, the boiling point of water, is determined by the degree of vacuum in the reduced pressure container, so if the water vapor temperature is set as a set value and compared with the temperature of the atmosphere in the reduced pressure container, the temperature of the atmosphere will be included. When the amount of water vapor decreases, the temperature of the atmosphere does not reach the set value even if the material to be dried is continued to be heated. Therefore, by detecting the atmospheric temperature in the reduced pressure container and comparing it with the set value, it is possible to know a state in which the atmospheric temperature has not reached the set value, that is, a state in which the amount of water vapor in the atmosphere has decreased. The present invention focuses on this feature.

The above object has a means for detecting the temperature of the atmosphere, that is, the gas in the vacuum container, and the temperature of water vapor evaporating from the material to be dried in the vacuum container is set as a set value, and the detection result is compared with the detection result of the ambient temperature. decreases after reaching the set value, or by determining the relative imbalance between the heating control amount and the ambient temperature within the vacuum vessel.

[For production]

While reducing the pressure inside the vacuum container and heating the material to be dried,
Detecting the atmosphere, that is, the temperature of the gas inside the vacuum container, and determining whether or not the ambient temperature reaches the set value by setting the water vapor temperature in the vacuum chamber at the time of pressure reduction as a set value, and determining whether the ambient temperature reaches the set value. When the set value is not reached, it is determined that the drying is completed.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3. In the figure, reference numeral 1 denotes a reduced-pressure container that stores the object 2 to be dried, and 3 a microwave heater that heats the object 2 to be dried using microwaves. The microwave heater 3 is installed on the side wall of the reduced pressure container 1 so as to be able to heat the material 2 to be dried in the reduced pressure container 1. 4a and 4b are exhaust pipes provided on the side wall of the decompression vessel 1;
a is connected to a vacuum vessel 11, and a pump 5 is connected to the exhaust pipe 4a.
is connected to the pump 5, and an exhaust pipe 4b is further connected to the pump 5. 6a and 6b are front 1e! A temperature detector is installed in the trachea 4a and detects the temperature of the atmosphere inside the vacuum container 1, which is exhausted from the vacuum container 1 by the pump 5.The temperature sensor 6a detects the upper limit value, and the WA temperature sensor 6b detects the lower limit value. It is something to detect. Reference numeral 7 denotes a control unit, which is composed of an input/output device 8a, a storage device i8b consisting of a fixed memory bag 'fit (ROM), a readable or writable storage device t (RAM), and a central processing unit f (CPU) 8C. . The input/output bag! 8a is a temperature sensor 6a, 6b
It is connected to the microwave heater 3 and the electromagnetic valve 10 and outputs control signals thereof. In addition, the central processing bag'm 8
c compares the temperature detection result sent through the input/output bag fl8a with the set value stored in the storage device i8b, and controls the microwave heater 3 or the solenoid valve 10. It calculates and outputs a signal based on the data in the storage device 8b. The functions of the control section 7 will be explained at the same time as the operating conditions are explained.

In such a configuration, the drying process status of the material to be dried 2 will be explained. First, the material to be dried 2 is placed in a vacuum container 1, and the pressure inside the vacuum container 1 is reduced by the pump 5. Thereafter, the microwave heater 3 is operated to heat the material 2 to be dried. The temperature of the material to be dried 2 increases, water evaporates, and the reduced pressure container 1 is filled with water vapor. Therefore, the exhaust pipe 4a
The temperature of the atmosphere inside the vacuum vessel 1 exhausted from the vacuum vessel 1 has a humidity at the boiling point of water depending on the degree of vacuum within the vacuum vessel 1, since water vapor accounts for a large proportion of the atmosphere as described above. Therefore, the temperature detector 6a for measuring the upper limit value operates and detects the temperature of the exhaust gas. When the temperature detector 6a operates, the detection result is transmitted to the central processing bag K8c via the input/output device 8a of the control section 7, and input/output is sent from the central processing device 8c to the microwave heater 3. A stop signal is output via device I 8 a. The microwave heater 3 stops its heating operation in response to a stop signal from the central processing unit 8c. At this time, the pump 5 continues to operate and exhausts the atmosphere inside the reduced pressure container l. Therefore, the water vapor in the reduced pressure container 1 is exhausted by the pump 5, and the water in the material to be dried 2 is evaporated one after another.

Therefore, the temperature of the material to be dried 2 itself decreases due to the heat of vaporization of the moisture, and the temperature of the exhaust gas also decreases. and,
When the exhaust gas temperature becomes a certain temperature, that is, below the lower limit value, the temperature detector 6b is activated.

The detection result of the temperature sensor 6b is sent to the input/output circuit 8 of the control section 7.
It is input to the central processing unit 8c via a.

The central processing *M8c outputs a starting signal to start the microwave heater 3 based on the detection result of the temperature sensor 6b. The activation signal is transmitted to the microwave heater 3 via the input/output bag ft 8 a, and the microwave heater 3 is activated to heat the object 2 to be dried. in this way,
The microwave heater 3 is repeatedly started and stopped to heat the material 2 to be dried to a certain temperature range, and the atmosphere inside the vacuum container 1 is exhausted by the pump 5, thereby drying the material 2 to be dried. Then, when the material to be dried 2 becomes dry, no water vapor is generated. On the other hand, since gases other than water vapor in the reduced pressure container 1 are not directly heated by the microwave heater 3, the atmospheric temperature in the reduced pressure container 1 becomes difficult to rise. Therefore, since the ambient temperature becomes difficult to rise, the time required for the temperature sensor 6a to operate becomes longer. In addition, in the central processing unit 8C, the time from starting to stopping the microwave heater 3 is measured by a built-in timer means. If the time exceeds a certain value, that is, the material to be dried 2 in the vacuum container 1 becomes dry, no water vapor is generated, and it takes a long time for the atmospheric temperature in the vacuum container 1 to rise. When this happens, it is determined that the drying is completed, and a stop signal is output from the central processing unit 8C to the microwave heater 3 and the pump 5 via the input/output device 8a.

This stop signal causes the microwave heater 3 and the pump 5 to
stops. Further, a release signal is output from the central processing unit 8c to the solenoid valve 1o via the input/output bag W18a, and the solenoid valve 10 opens to open the inside of the depressurized container 1 to the atmosphere. With this operation, the operation of drying the object to be dried 2 is completed.

Based on a specific example of the vacuum drying apparatus, the relationship between the operating time of the microwave heater and the degree of dryness of the material to be dried, that is, the mass ratio before and after the drying process will be explained with reference to FIG. By the way, the process shown in FIG. 2 is the situation when 13007 kitchen waste was dried at a reduced pressure of -500 Hy. Further, the upper limit detection temperature of the temperature detector 6a is 68°C, i1! The lower limit detection temperature of the degree detector 6b is 64°C, and the drying completion determination time of the operation time from start to stop of the microwave heater 3 measured by the central processing bag fit8c is 6 minutes. Furthermore, in FIG. 2, the vertical axis shows the microwave heater 3.
The horizontal axis shows the operation time of , and the mass ratio of the material to be dried 2 is shown on the horizontal axis. In the figure, immediately after the start of drying, the material to be dried 2 is at room temperature, so the operating time of the microwave heater 3 is long when heating it. As a result, the operation time of the dryer is shortened by only supplying the heat taken away by the heat of vaporization of water.In this way, the material to be dried 2 is heated and dried, and the mass ratio of the material to be dried 2 is 15. %, the amount of water vapor evaporated from the dried material 2 decreases, making it difficult for the atmospheric temperature inside the vacuum container 1 to rise as described above. Therefore, as the operating time of the microwave heater 3 increases, , the temperature of the atmosphere does not rise to the upper limit value of the temperature sensor 6a. That is,
Temperature detector 6a stops working and microwave heater 3
A state in which the variation detector 6a does not operate for more than 6 minutes after activation is considered to be the end of drying, and each device is stopped and the solenoid valve 10 is opened. An example of the drying situation described above is shown as a flowchart as the third factor.

According to such a configuration, since the end of the drying process of the object 2 to be dried is automatically determined, the operator can
No uneven drying occurs. Moreover, problems such as ignition due to over-drying treatment can be prevented. Further, in the above configuration, the exhaust pipe 4a is used to detect the atmospheric temperature inside the reduced pressure container 1.

4b is provided with temperature sensors 6a and 5b having a simple structure, and the configuration is simple.

By the way, in the above embodiment, the operation time of the microwave heater 3 is measured and the end of drying is determined based on the time, but the present invention is not limited to this.
Changes in the ambient temperature inside the vacuum container 1 may be constantly detected, and the end of drying may be determined when a state in which the ambient temperature does not rise even though the vacuum container 1 is in a heating state is detected. Further, in one embodiment, the exhaust temperature is detected by the temperature detectors 6a and 6b, but if the configuration is such that the atmospheric temperature inside the reduced pressure vessel 1 can be detected without being influenced by the microwave heater 3, However, the present invention is not limited to the above embodiment in this respect either. Furthermore, the microwave heater 3 is not limited to this; similar effects can be obtained by using other high-frequency heaters with different frequency ranges.

〔Effect of the invention〕

As explained above, according to the present invention, completion of drying can be reliably detected with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing an embodiment of the reduced pressure drying device according to the book I, and Fig. 2 is a graph showing the relationship between the operating time of the microwave heater and the quality l ratio of moisture in the dried material. FIG. 3 is a flowchart showing an example of operating conditions in the embodiment of FIG. 1, and FIG. 4 is a block circuit diagram showing a conventional drying device. ! ...Reduced pressure container, 2... Material to be dried, 3
...Microwave heater, 4a, 4b...
・Exhaust pipe, 5...Pump, 6a, 6b...
・・Temperature detector, ・・・Control unit, 10・・・・
...Katsuo Ogawa 7, Solenoid Valve Agent Patent Attorney. Figure 1 5 --- Bonde 6a, 6b --- Figure 3

Claims (1)

[Scope of Claims] 1. A vacuum container for storing a material to be dried therein, a pressure reducing means for reducing the pressure inside the vacuum container, a high-frequency heater for heating the material to be dried, and an atmospheric temperature within the vacuum container. Vacuum drying characterized by comprising a temperature detector for detecting the temperature, and a control means for determining the relative imbalance between the control amount of the high-frequency heater that heats the inside of the vacuum container and the ambient temperature to determine the end of drying. Device. 2. A method for controlling a vacuum drying device comprising a vacuum container for storing a material to be dried therein, a pressure reducing means for reducing the pressure inside the vacuum container, and a high-frequency heater for heating the material to be dried,
reducing the pressure in the vacuum container and heating the material to be dried;
A method for controlling a vacuum drying apparatus, characterized in that the processing operation is stopped when the ambient temperature in the vacuum container reaches a set value corresponding to the boiling point of water in the vacuum container and the ambient temperature drops.