JP2007093077A - Vacuum drying method and vacuum drying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum drying method and a vacuum drying device for depressurizing a chamber without using a vacuum pump. <P>SOLUTION: The vacuum drying method is provided for storing drying objects 50 in the drying chamber 4 and depressurizing the drying chamber 4 while heating the drying objects 50 subjected to vacuum drying. The method comprises a water vapor replacing step of replacing gas in the drying chamber 4 with water vapor, and a depressurizing step of condensing the water vapor in the drying chamber 4 on the surface of a cooler 10 in a state of closing the drying chamber 4 and discarding it to depressurize the drying chamber 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vacuum drying method and a vacuum drying apparatus in which an object to be dried is stored in a drying chamber, and the object to be dried is decompressed while being heated in the drying chamber and vacuum dried.

  Conventionally, when producing dried products from dried foods such as coffee and soup, and dried foods such as dried vegetables (such as spinach and leeks), a vacuum pump has been used as one of the devices for vacuum drying these dried products. An equipped vacuum drying apparatus has been proposed (see Patent Document 1). A vacuum drying apparatus equipped with such a vacuum pump is shown in FIG. The vacuum drying apparatus 100 stores the material 150 to be dried in the drying chamber 104, and then discharges the air in the drying chamber 104 by the vacuum pump 106 (white arrow in FIG. 3) to decompress the inside of the drying chamber 104.

  And if the to-be-dried object 150 is heated with the heating source 114 (this heat source 114 is comprised with the heat radiator of the refrigerator 102), the water | moisture content which the to-be-dried object 150 has will be evaporated at low temperature. That is, when the inside of the drying chamber 104 is evacuated by the vacuum pump 106, the water is evaporated at a low temperature to become water vapor. Between the drying chamber 104 and the vacuum pump 106, a cold trap 108 cooled to an extremely low temperature by a cooler of the refrigerator 102 is provided.

  The water vapor evaporated from the material to be dried 150 collides with the surface of the cold trap 108 and condenses and is discarded. That is, the water vapor in the drying chamber 104 is condensed by a so-called cryogenic cryopump and discarded. Thereby, moisture in the drying chamber 104 is removed and vacuum drying is performed. In this way, the material to be dried 150 was vacuum dried in the drying chamber 104.

JP 2004-353969 A

  However, when the object to be dried is vacuum-dried, a vacuum pump is provided in addition to the refrigerator to reduce the pressure in the chamber. For this reason, there existed a problem that a vacuum dryer will become a cost increase.

  Therefore, it has been desired to develop a vacuum drying apparatus that can vacuum dry an object to be dried without using a vacuum pump.

  The present invention has been made to solve the problems of the related art, and an object of the present invention is to provide a vacuum drying method and a vacuum drying apparatus capable of reducing the pressure in the chamber without using a vacuum pump. To do.

  That is, the vacuum drying method of the present invention is a method in which an object to be dried is housed in a drying chamber, and the object to be dried is vacuum-dried while being heated in the drying chamber. A water vapor replacement step of substituting with water vapor, and a depressurization step of depressurizing the inside of the drying chamber by condensing the water in the drying chamber into a cooler and discarding the water in the state where the inside of the drying chamber is sealed. Features.

  In addition to the above, the vacuum drying method of the invention of claim 2 is provided with an auxiliary chamber which is capable of communicating with the inside of the drying chamber and provided with a cooler. In the steam replacement step, the drying chamber and the auxiliary chamber are provided. And the gas in both chambers is replaced with water vapor, and in the decompression process, the moisture in both chambers is condensed in the cooler and discarded in the state where the drying chamber and auxiliary chamber are in communication. Features.

  In addition to the claim 2, the vacuum drying method of the invention of claim 3 includes, in addition to claim 2, a water vapor supply step for supplying water vapor into the auxiliary chamber in a state where the drying chamber and the auxiliary chamber are isolated after the pressure reducing step, After the water vapor supplying step, the water in the auxiliary chamber is condensed in the cooler and discarded, and the drying chamber and the auxiliary chamber are connected to each other and the second pressure reducing step for reducing the pressure in the drying chamber is performed at least once. It is characterized by carrying out.

  According to a fourth aspect of the present invention, there is provided a vacuum drying apparatus according to the second or third aspect, wherein a heating source for heating an object to be dried in the drying chamber, and a water vapor supply device for supplying water vapor to the auxiliary chamber and the drying chamber And a valve device for controlling the communication between the drying chamber and the auxiliary chamber and the communication between both chambers and the outside, and a refrigerator having a refrigerant circuit including a cooler.

  Furthermore, the vacuum drying apparatus of the invention of claim 5 is characterized in that, in claim 4, the refrigerator uses carbon dioxide as a refrigerant.

  According to the present invention, a material to be dried is stored in a drying chamber, and the material to be dried is vacuum-dried while being heated in the drying chamber, wherein the gas in the drying chamber is replaced with water vapor. Since it includes a water vapor replacement step and a depressurization step of depressurizing the inside of the drying chamber by condensing the water in the drying chamber in a cooler and discarding it while the inside of the drying chamber is sealed, Thus, the pressure in the drying chamber can be reduced without using a vacuum pump in the vacuum drying apparatus. This makes it possible to simplify the vacuum drying apparatus. Therefore, the cost of the vacuum drying apparatus can be greatly reduced.

  Further, according to the invention of claim 2, in addition to the above, the auxiliary chamber provided with a cooler is provided while being able to communicate with the inside of the drying chamber. In the steam replacement step, the drying chamber and the auxiliary chamber are provided. Since the gas in both chambers is replaced with water vapor and the drying chamber and auxiliary chamber are in communication with each other, moisture in both chambers is condensed in the cooler and discarded in the decompression process. By reducing the pressure, the inside of the drying chamber can be depressurized and dehumidified for drying. Thereby, it becomes possible to dry the to-be-dried object accommodated in the drying chamber. Therefore, for example, it is possible to greatly improve the drying of an object to be dried stored in a drying chamber without obtaining an ultra-low temperature up to a cryopump as in the prior art.

  According to the invention of claim 3, in addition to claim 2, after the decompression step, the water vapor supply step of supplying water vapor into the auxiliary chamber in a state where the drying chamber and the auxiliary chamber are isolated, and the water vapor After the supplying step, the water in the auxiliary chamber is condensed in the cooler and discarded, and the drying chamber and the auxiliary chamber are connected to each other, and the second pressure reducing step for reducing the pressure in the drying chamber is performed at least once. Therefore, even when the moisture in the drying object evaporates and the pressure in the drying chamber rises in a state where the pressure in the drying chamber is reduced, the pressure in the drying chamber can be reduced again. Thereby, the inside of the drying chamber can be maintained in a predetermined reduced pressure state. Therefore, the material to be dried stored in the drying chamber can be dried extremely effectively.

  According to the invention of claim 4, in addition to claim 2 or claim 3, a heating source for heating an object to be dried in the drying chamber, a steam supply device for supplying steam to the auxiliary chamber and the drying chamber, And a refrigeration machine having a refrigerant circuit including a cooler, which controls the communication between the drying chamber and the auxiliary chamber, and the communication between both chambers and the outside. The drying of the material to be dried can be effectively promoted by the heating source. As a result, the object to be dried stored in the drying chamber can be dried very quickly.

  In particular, since a water vapor supply device for supplying water vapor to the auxiliary chamber and the drying chamber is provided, the water inside the auxiliary chamber and the drying chamber is cooled and condensed by a cooler, thereby reducing the pressure in the drying chamber. it can. Thereby, for example, the inside of the drying chamber can be effectively depressurized without using a vacuum pump as in a conventional vacuum drying apparatus. Therefore, it is possible to simplify the vacuum drying apparatus, and the cost of the vacuum drying apparatus can be greatly reduced.

  Furthermore, according to the invention of claim 5, in claim 4, since the refrigerator uses carbon dioxide as a refrigerant, it is possible to prevent environmental destruction such as a warming phenomenon due to acid rain or carbon dioxide, for example. Become. This contributes to the prevention of global warming and the prevention of destruction of the natural environment.

  The object of the present invention is to reduce the pressure in the drying chamber with a simple structure in which water vapor is supplied into the drying chamber and condensed by a cooler.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a vacuum drying apparatus 1 showing an embodiment of the present invention, and FIG. 2 is a time chart of the vacuum drying apparatus 1 of the present invention. As shown in FIG. 1, the vacuum drying apparatus 1 communicates with a drying chamber 4 for storing a dried food 50 such as powdered foods such as coffee and soup and dried vegetables (such as spinach and leeks), and the inside of the drying chamber 4. The auxiliary chamber 14 and the refrigerator 8 that heats the object to be dried 50 accommodated in the drying chamber 4 and cools the auxiliary chamber 14 are configured.

  The drying chamber 4 and the auxiliary chamber 14 are each connected to an exhaust duct 26 having a valve device 24, and the drying chamber 4 is also connected to the auxiliary chamber 14 by an intermediate duct 28 having a valve device 24. The valve device 24 includes a first on-off valve 24A, a second on-off valve 24B, and a third on-off valve 24C. The first on-off valve 24A is between the drying chamber 4 and the auxiliary chamber 14, the second on-off valve 24B is between the auxiliary chamber 14 and the exhaust duct 26, and the third on-off valve 24C is between the drying chamber 4 and the exhaust duct. 26.

  When the first opening / closing valve 24A is opened, the inside of the drying chamber 4 and the auxiliary chamber 14 are communicated, and when the first opening / closing valve 24A is closed, the communication between the inside of the drying chamber 4 and the inside of the auxiliary chamber 14 is blocked. Further, when the second opening / closing valve 24B is opened, the inside of the auxiliary chamber 14 and the exhaust duct 26 are communicated, and when the second on-off valve 24B is closed, the communication between the inside of the auxiliary chamber 14 and the inside of the exhaust duct 26 is blocked. Further, the interior of the drying chamber 4 and the exhaust duct 26 are communicated when the third on-off valve 24C is opened, and the communication between the interior of the drying chamber 4 and the exhaust duct 26 is blocked when the third on-off valve 24C is closed.

On the other hand, although not shown, the refrigerator 8 has an internal intermediate pressure type multistage (2) composed of an electric element (driving element) in a hermetic container and first and second rotary compression elements driven by the electric element. Stage) equipped with a compression rotary compressor. A predetermined amount of carbon dioxide (CO ₂ ) is sealed as a refrigerant in the refrigerant circuit of the rotary compressor.

The rotary compressor compresses a gas refrigerant (CO ₂ ) sucked from a suction pipe (not shown) by a first rotary compression element, and once discharges the compressed gas refrigerant into a sealed container. The intermediate-pressure gas refrigerant in the sealed container is sucked into the second rotary compression element, compressed, and discharged from the discharge pipe.

  A heating source 18 (corresponding to a radiator of the refrigerator 8 constituting the vacuum drying apparatus 1 of the present invention) is connected to a discharge pipe of the rotary compressor by piping, and an outlet valve (not shown) is provided on the outlet side of the heating source 18. The pipe is connected to the cooler 10 provided in the auxiliary chamber 14 via the. The outlet side of the cooler 10 is connected to a suction pipe of a rotary compressor through an accumulator (not shown), thereby forming an annular refrigerant circuit.

  The high-temperature and high-pressure gas refrigerant compressed in two stages by the first and second rotary compression elements of the rotary compressor as described above is heated in the heating source 18 with the air in the drying chamber 4 (corresponding to the gas of the present invention) and heat. The material to be dried is dissipated and the object to be dried 50 provided thereon is heated. The gas refrigerant radiated by the heating source 18 is liquefied in the process of being throttled by the expansion valve, enters a gas-liquid mixed state, flows into the cooler 10, and evaporates and vaporizes there.

  As a result, a cooling action is exerted to cause the surrounding water vapor to condense on the surface of the cooler 10, thereby depressurizing the auxiliary chamber 14. A technique for reducing the pressure in the auxiliary chamber 14 by condensing water vapor on the surface of the cooler 10 will be described in detail later. Then, the gas refrigerant exiting the cooler 10 flows into the accumulator, where it is gas-liquid separated, and the transcritical refrigeration cycle in which only the gas refrigerant is sucked into the rotary compressor from the suction pipe is repeated. In addition, 52 is a saucer for mounting the to-be-dried object 50.

  A steam supply device 22 for producing steam is connected to the auxiliary chamber 14. The water vapor supply device 22 is connected to the auxiliary chamber 14 by a water vapor supply duct 23, and the water vapor supply device 22 and the auxiliary chamber 14 are communicated with each other through the water vapor supply duct 23. The water vapor supply device 22 is configured by a water vapor generation device that generates water vapor by vibrating water using ultrasonic waves, or a water vapor generation device that generates water vapor by heating and boiling water. Preferably, the water vapor supply device 22 is constituted by a water vapor generator that heats and boiles water. The water vapor supply device 22 is configured to automatically supply water when water is generated by generating water vapor. Further, it is assumed that the water vapor supply device 22 is sealed and communicates with the auxiliary chamber 14.

  With the above configuration, the operation of the vacuum drying apparatus 1 will now be described with reference to FIG. It is assumed that an object to be dried 50 is accommodated in the drying chamber 4 and each valve device 24 (first on-off valve 24A, second on-off valve 24B, third on-off valve 24C) is closed. Further, the vacuum drying apparatus 1 includes a control device (not shown) constituted by a general-purpose microcomputer, etc. The vacuum drying device 1 uses this control device for the refrigerator 8, the steam supply device 22, the valve device 24, and the like. It is assumed that control is performed.

  FIG. 2 shows time on the horizontal axis, and time elapses from the left end to the right. In the figure, a six-stage frame is shown in the vertical direction. From the top, the first on-off valve 24A (on-off valve A in FIG. 2), the second on-off valve 24B (on-off valve B in FIG. 2), and the third on-off valve are shown. A three-stage frame of the valve 24C (the on-off valve C in FIG. 2) is shown, with the upper side of each frame showing valve opening and the lower side showing valve closing. The fourth frame shows the supply of water vapor from the water vapor supply device 22, and the upper side of this frame shows the supply of water vapor from the water vapor supply device 22 into the drying chamber 4 (auxiliary chamber 14). The side indicates that no steam is supplied from the steam supply device 22. The fifth frame shows the drying chamber 4 (chamber A in FIG. 2) and the sixth frame shows the auxiliary chamber 14 (chamber B frame in FIG. 2). Pressure), and the lower side indicates low pressure.

  When the operation of the vacuum drying device 1 (including the operation of the refrigerator 8) is started, the control device turns on each valve device 24 (first on-off valve 24A, second on-off valve 24B, third on-off valve 24C). Open for a predetermined time from the start position (1). Thereby, water vapor is supplied from the water vapor supply device 22 into the auxiliary chamber 14. When water vapor is supplied into the auxiliary chamber 14, a part of the air in the auxiliary chamber 14 (corresponding to the gas of the present invention) is discharged to the outside from the exhaust duct 26 via the second on-off valve 24B (see FIG. 1 white). Arrow), the remaining air is supplied into the drying chamber 4 through the first on-off valve 24A. Further, the air in the drying chamber 4 is pushed by the air flowing in from the first on-off valve 24A, and is discharged to the outside from the exhaust duct 26 through the third on-off valve 24C (white arrow in FIG. 1).

  When the water vapor is further supplied from the water vapor supply device 22 into the auxiliary chamber 14, the auxiliary chamber 14 is filled with water vapor. When the auxiliary chamber 14 is filled with water vapor, the water vapor flows from the auxiliary chamber 14 into the drying chamber 4 via the first on-off valve 24A. As a result, all the air in the drying chamber 4 is discharged from the exhaust duct 26 to the outside via the third on-off valve 24C, and the drying chamber 4 is filled with water vapor. In addition, the filling of the water vapor in the auxiliary chamber 14 is obtained in advance by an experiment to obtain an elapsed time until the water vapor is filled into the auxiliary chamber 14, and the filling of the water vapor in the auxiliary chamber 14 is detected based on the elapsed time. Further, the fullness may be detected by converting the amount of water vapor in the auxiliary chamber 14 using an oxygen amount detector or a humidity detector. In this case, if a plurality of oxygen detectors or humidity detectors are provided in the auxiliary chamber 14 at a plurality of locations, particularly at the corners of the plurality of locations, the filling of water vapor in the auxiliary chamber 14 can be detected more accurately. Can be convenient.

  That is, the control device drives the valve device 24 to open the first on-off valve 24A, the second on-off valve 24B, and the third on-off valve 24C, and to supply water vapor from the water vapor supply device 22 into the drying chamber 4 and the auxiliary chamber 14. The steam replacement process (Fig. 2 * arrow) that replaces the air is performed. Note that at start (1), the control device opens the first on-off valve 24A and the third on-off valve 24C for a predetermined time without opening the second on-off valve 24B, and opens the auxiliary chamber 14 from the water vapor supply device 22. Water vapor may be supplied into the drying chamber 4. In this case, when the water vapor replacement step is executed with the first on-off valve 24A, the second on-off valve 24B, and the third on-off valve 24C opened, the water vapor filled in the auxiliary chamber 14 is discharged from the second on-off valve 24B to the exhaust duct 26. There is a possibility of leakage. However, if the first on-off valve 24A and the third on-off valve 24C are opened for a predetermined time and the water vapor replacement step is executed while the second on-off valve 24B is closed without being opened, the water vapor filled in the auxiliary chamber 14 becomes the second There is no possibility of leakage from the on-off valve 24B to the exhaust duct 26, and the drying chamber 4 and the auxiliary chamber 14 can be efficiently filled with water vapor.

  Next, the control device closes the second on-off valve 24B and the third on-off valve 24C after a predetermined time has elapsed (after supply of water vapor from the water vapor supply device 22 into the auxiliary chamber 14 is stopped) (hereinafter referred to as the “on / off valve”). The third on-off valve 24C is kept closed). When the second on-off valve 24B and the third on-off valve 24C are closed, the inside of the drying chamber 4 and the auxiliary chamber 14 are sealed. At this time, the inside of the drying chamber 4 and the auxiliary chamber 14 communicate with each other while the first on-off valve 24A remains open.

  Next, the cooler 10 in the auxiliary chamber 14 is cooled by the operation of the refrigerator 8, and the heating source 18 in the drying chamber 4 is damaged at a predetermined temperature (in this case, the color or flavor of the object 50 to be dried). Not heated). When the cooler 10 of the auxiliary chamber 14 is cooled, water vapor in the drying chamber 4 and the auxiliary chamber 14 condenses on the surface of the cooler 10.

  Here, a technique for reducing the pressure in the auxiliary chamber 14 by condensing water vapor on the surface of the cooler 10 will be described. It is already known that when water becomes water vapor, the volume increases about 1700 times, and conversely, when water vapor condenses into water (including water droplets), the volume becomes about 1/1700 times. That is, when the water vapor filled in the drying chamber 4 and the auxiliary chamber 14 condenses on the surface of the cooler 10 to form water droplets, the volume of the water vapor decreases, and the inside of the drying chamber 4 and the auxiliary chamber 14 The pressure is reduced and the vacuum is applied after a predetermined time has elapsed (FIG. 2 (A1), (B1)).

  In this embodiment, the refrigerator 8 is operated at the start of the operation of the vacuum drying apparatus 1. However, it takes a predetermined time until the cooler 10 is cooled to a temperature at which water vapor condenses on the surface. Even if the apparatus 1 and the refrigerator 8 are operated at the same time and the water vapor is supplied from the water vapor supply device 22 into the auxiliary chamber 14, there is no major problem in the decompression of the auxiliary chamber 14. In addition, when the steam supply capacity of the steam supply device 22 is small, it takes a long time to fill the auxiliary chamber 14 with water vapor, and if the water vapor condenses on the surface of the cooler 10, it will hinder the decompression in the auxiliary chamber 14. May occur. In this case, it is desirable to operate the refrigerator 8 after the drying chamber 4 and the auxiliary chamber 14 are filled with water vapor, or before a predetermined time before the drying chamber 4 and the auxiliary chamber 14 are filled with water vapor. Thereby, the decompression in the auxiliary chamber 14 can be suitably performed without any trouble, which is convenient.

  Then, in a state where the inside of the drying chamber 4 is sealed, the moisture (water vapor) in the drying chamber 4 is condensed on the surface of the cooler 10 and discarded, whereby the first decompression step (first step) for decompressing the inside of the drying chamber 4 is performed. 1 decompression step) (Figure 2 **). The water condensed on the surface of the cooler 10 can be discarded from the auxiliary chamber 14 to the outside by a pump (not shown), or can be used again as water vapor by the water vapor supply device 22.

    Due to this reduced pressure, the moisture of the object to be dried 50 stored in the drying chamber 4 has a low boiling temperature, the water is evaporated from the object to be dried 50, and so-called vacuum drying of the object to be dried 50 is performed. That is, the water vapor in the drying chamber 4 and the auxiliary chamber 14 is condensed in the cooler 10 provided in the auxiliary chamber 14 so that the pressure in the drying chamber 4 and the auxiliary chamber 14 is reduced. Water can be boiled and evaporated. Thereby, vacuum drying can be performed without impairing the color or flavor of the object to be dried 50. Further, since the object to be dried 50 is heated by the heating source 18 provided below, the moisture contained in the object to be dried 50 is evaporated and dried by this heating and decompression, and the inside of the drying chamber 4 and auxiliary The pressure in the chamber 14 gradually increases with time (FIG. 2 (B1) → (B2)).

  When the object to be dried 50 in the drying chamber 4 is dried for a predetermined time, the control device drives the valve device 24 again, closes the opened first on-off valve 24A, and closes the second on-off valve. 24B is opened and the drive of the refrigerator 8 is stopped ((2) of FIG. 2). When the second on-off valve 24B is opened, the auxiliary chamber 14 communicates with the exhaust duct 26, and the pressure increases (atmospheric pressure) ((B2) in FIG. 2). In this case, since the third on-off valve 24C as described above remains closed, the drying chamber 4 and the auxiliary chamber 14 are sealed in an isolated state (independent state).

  Next, the control device supplies water vapor from the water vapor supply device 22 into the auxiliary chamber 14 for a predetermined time. That is, a water vapor supply step for supplying water vapor from the water vapor supply device 22 into the auxiliary chamber 14 is performed. In the water vapor supply step, when water vapor is supplied into the auxiliary chamber 14, the air in the auxiliary chamber 14 is discharged to the outside from the exhaust duct 26 via the second on-off valve 24B, and the auxiliary chamber 14 is filled with water vapor. To charge. That is, here, the air and water vapor in the auxiliary chamber 14 are replaced (FIG. 2, ◆ arrows). Each ◆ arrow in FIG. 2 indicates a water vapor supplying step.

  Next, after a predetermined time has elapsed, the control device stops the supply of water vapor from the water vapor supply device 22 into the auxiliary chamber 14, closes the second on-off valve 24B, and starts the operation of the refrigerator 8. Thereby, the cooler 10 in the auxiliary chamber 14 is cooled as described above. When the cooler 10 is cooled, the water vapor in the auxiliary chamber 14 condenses on the surface of the cooler 10 and the pressure in the auxiliary chamber 14 is reduced. In this case, since the first on-off valve 24A is closed, only the auxiliary chamber 14 is decompressed.

  Then, when a predetermined time elapses, the pressure in the auxiliary chamber 14 is reduced more than the pressure in the drying chamber 4. That is, the drying chamber 4 and the auxiliary chamber 14 are individually sealed, and the inside of the drying chamber 4 is heated by the heating source 18. As a result, the moisture contained in the object to be dried 50 evaporates and the pressure gradually rises, so that the auxiliary chamber 14 is depressurized more than the drying chamber 4.

  When the inside of the auxiliary chamber 14 is reduced to a predetermined pressure, the control device opens the first on-off valve 24 </ b> A to connect the inside of the drying chamber 4 and the inside of the auxiliary chamber 14. Thereby, the pressure in the drying chamber 4 and the auxiliary chamber 14 is reduced to the same pressure ((A2) (B3) in FIG. 2). That is, after the first decompression step, the moisture in the drying chamber 4 is condensed on the surface of the cooler 10 and discarded in a state where the inside of the drying chamber 4 and the auxiliary chamber 14 are communicated and sealed again. A second depressurization step is performed to depressurize the inside of the drying chamber 4 (marked with a circle in FIG. 2).

  Due to this reduced pressure, moisture is further evaporated from the material to be dried 50 and vacuum drying is performed. Moreover, since the to-be-dried object 50 is heated by the heating source 18 provided below, the moisture contained in the to-be-dried object 50 evaporates, and the inside of the drying chamber 4 and the auxiliary chamber 14 with the passage of time. The pressure gradually rises (FIG. 2 (B3) → (B4)).

  Then, if the object to be dried 50 in the drying chamber 4 is dried for a predetermined time, the control device drives the valve device 24 again as described above, and closes the opened first on-off valve 24A and closes the second closed valve 2A. The on-off valve 24B is opened to stop the driving of the refrigerator 8 ((3) in FIG. 2). When the second on-off valve 24B is opened, the inside of the auxiliary chamber 14 communicates with the exhaust duct 26, and the pressure increases (atmospheric pressure) ((B4) in FIG. 2).

  The control device again causes the moisture in the drying chamber 4 to condense on the surface of the cooler 10 in a state where the inside of the drying chamber 4 and the auxiliary chamber 14 are again communicated and sealed after the first decompression step. It discards, The inside of the drying chamber 4 is decompressed, and the to-be-dried object 50 is repeatedly vacuum-dried (A3) → (A4), (B5) → (B6) → (B7). That is, the vacuum drying method of the present invention is a method in which an object to be dried 50 is accommodated in the drying chamber 4, and the object to be dried 50 is vacuum-dried while being heated in the drying chamber 4. The to-be-dried object 50 is vacuum-dried by performing the 1st pressure reduction process to the 2nd pressure reduction process 1 time or more.

  As described above, the vacuum drying apparatus 1 is configured to replace the air in the drying chamber 4 with water vapor, and to remove the moisture in the drying chamber 4 from the surface of the cooler 10 in a state where the drying chamber 4 is sealed. And the pressure reducing step of reducing the pressure inside the drying chamber 4 by discarding it, for example, the pressure inside the drying chamber 4 can be surely reduced without using a vacuum pump in a vacuum drying device as in the prior art. be able to. As a result, the vacuum drying device 1 can be simplified, and the cost of the vacuum drying device 1 can be greatly reduced.

  In addition, the vacuum drying apparatus 1 is capable of communicating with the inside of the drying chamber 4 and is provided with an auxiliary chamber 14 provided with a cooler 10. In the water vapor replacement step, the drying chamber 4 and the auxiliary chamber 14 are communicated to replace the gas in both the chambers 4 and 14 with water vapor. In the first decompression step, the water vapor in both the chambers 4 and 14 is condensed on the surface of the cooler 10 in a state where the drying chamber 4 and the auxiliary chamber 14 are communicated with each other. By depressurizing the auxiliary chamber 14, the inside of the drying chamber 4 is depressurized and dehumidified, and the object to be dried 50 can be vacuum dried. Thereby, drying of the to-be-dried object 50 accommodated in the drying chamber 4 can be improved significantly.

  In addition, after the first decompression step, a water vapor supply step for supplying water vapor into the auxiliary chamber 14 in a state where the drying chamber 4 and the auxiliary chamber 14 are isolated, and after the water vapor supply step, Moisture is condensed on the surface of the cooler 10 and discarded, and the drying chamber 4 and the auxiliary chamber 14 are communicated to perform the second decompression step of decompressing the interior of the drying chamber 4 at least once. Yes. Thereby, even when moisture evaporates from the object to be dried 50 and the pressure in the drying chamber 4 increases, the pressure in the drying chamber 4 can be reduced again. Therefore, it becomes possible to maintain the inside of the drying chamber 4 in a predetermined reduced pressure state, and the object to be dried 50 stored in the drying chamber 4 can be dried extremely effectively.

  The vacuum drying apparatus 1 includes a heating source 18 (heat radiator) that heats an object to be dried 50 in the drying chamber 4, a water vapor supply device 22 that supplies water vapor into the auxiliary chamber 14 and the drying chamber 4, and a drying chamber. 4 and the auxiliary chamber 14 and a valve device 24 for controlling the communication between the chambers 4 and 14 and the outside, and the refrigerator 8 including the cooler 10 and having a refrigerant circuit. Thus, the drying of the object to be dried 50 can be effectively promoted by the reduced pressure in the drying chamber 4 and the heating source 18, and the object to be dried 50 can be vacuum dried extremely quickly.

  In particular, since the steam supply device 22 for supplying water vapor to the auxiliary chamber 14 and the drying chamber 4 is provided, the water vapor in the auxiliary chamber 14 and the drying chamber 4 is condensed by being cooled by the cooler 10. The inside of 4 can be depressurized. Thus, for example, the inside of the drying chamber 4 can be effectively depressurized without using a vacuum pump as in a conventional vacuum drying apparatus, so that the vacuum drying apparatus 1 can be simplified. The cost of the vacuum drying apparatus 1 can be significantly reduced.

  Moreover, since the refrigerator 8 uses carbon dioxide as a refrigerant, it becomes possible to prevent environmental destruction such as warming due to acid rain or carbon dioxide. As a result, it is possible to contribute to prevention of global warming and to prevent destruction of the natural environment.

  In the embodiment, the heating source 18 for heating the object to be dried 50 in the drying chamber 4 has been described as a radiator of the refrigerator 8, but the heating source 18 is not limited to a radiator and may be an electric heater. . In this case, since the electric heater can easily control the temperature, the color and flavor of the object to be dried 50 can be suitably suppressed, which is convenient.

  Further, the vacuum drying apparatus 1 is not limited to the above embodiment, and the present invention is effective even when various other changes are made without departing from the gist of the present invention.

It is a block diagram of the vacuum dryer which shows the Example of this invention. It is a time chart figure of the vacuum dryer of this invention. It is a block diagram of the conventional vacuum dryer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum drying apparatus 4 Drying chamber 8 Refrigerator 10 Cooler 14 Auxiliary chamber 18 Heating source (heat radiator)
DESCRIPTION OF SYMBOLS 22 Steam supply apparatus 23 Steam supply duct 24 Valve apparatus 24A 1st on-off valve 24B 2nd on-off valve 24C 3rd on-off valve 26 Exhaust duct 50 Dried object

Claims (5)

A method of storing a material to be dried in a drying chamber and vacuum-drying the material to be dried while heating in the drying chamber,
A water vapor replacement step of replacing the gas in the drying chamber with water vapor;
A vacuum drying method comprising: a depressurizing step of depressurizing the inside of the drying chamber by condensing moisture in the drying chamber in a cooler and discarding the water inside the drying chamber in a sealed state. An auxiliary chamber provided with the cooler and capable of communicating with the inside of the drying chamber is provided,
In the water vapor replacement step, the drying chamber and the auxiliary chamber are communicated, and the gas in both chambers is replaced with water vapor,
2. The vacuum drying method according to claim 1, wherein in the decompression step, moisture in both chambers is condensed in the cooler and discarded in a state where the drying chamber and the auxiliary chamber are in communication with each other. After the pressure reducing step, a water vapor supplying step for supplying water vapor into the auxiliary chamber in a state where the drying chamber and the auxiliary chamber are separated from each other;
After the water vapor supplying step, the water in the auxiliary chamber is condensed in the cooler and discarded, and a second pressure reducing step for reducing the pressure in the drying chamber by connecting the drying chamber and the auxiliary chamber is performed. It implements at least once or more, The vacuum-drying method of Claim 2 characterized by the above-mentioned. A heating source for heating an object to be dried in the drying chamber;
A water vapor supply device for supplying water vapor into the auxiliary chamber and the drying chamber;
A valve device for controlling communication between the drying chamber and the auxiliary chamber, and communication between both chambers and the outside;
A vacuum drying apparatus for carrying out the vacuum drying method according to claim 2 or 3, further comprising a refrigerator having a refrigerant circuit including the cooler.   The vacuum dryer according to claim 4, wherein the refrigerator uses carbon dioxide as a refrigerant.

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