JP2004353969A - Vacuum drying method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent melting of a frozen object in freezing and drying, for efficiently providing dry goods by enhancing an operation ratio, by separating powder/grain collected in a bag filter, without reducing a vacuum state in a drying chamber. <P>SOLUTION: A dust collecting chamber 5 is arranged between the drying chamber 10A and a vacuum generator 6; and is characterized by separating the powder/grain G collected by the bag filter 55, by exciting the bag filter 55 equipped in this dust collecting chamber 5; and can remove the powder/grain G from the bag filter G without increasing pressure in the dust collecting chamber 5 and the drying chamber 10A. Thus, drying-freezing is enabled, and reduction in the operation ratio of the device can be avoided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to vacuum drying of foods and the like, and relates to a vacuum drying method and an apparatus therefor capable of performing an efficient drying process.
[0002]
BACKGROUND OF THE INVENTION
BACKGROUND ART Conventionally, in the processing of powders and granules such as foods, pharmaceuticals, agricultural chemicals, feeds, and chemicals, a vibrating vacuum drying apparatus has been employed as one of devices for vacuum-drying raw materials to obtain powders and the like. I have. As shown in FIG. 7, the vacuum drying apparatus D 'is formed by connecting a vacuum generator 6' for reducing the pressure in the drying chamber 10A 'to a housing 1' having an internal space as a drying chamber 10A '. The inside of the drying chamber 10A 'is depressurized, and the raw material charged into the drying chamber 10A' is vacuum-dried to obtain a powder G.
[0003]
A bag filter 55 'for separating the powder G is provided between the drying chamber 10A' formed in the housing 1 'and the vacuum generator 6'. As the operation of the vacuum drying apparatus D 'is continued, the permeability decreases due to the collected powder G, and the pressure loss before and after the bag filter 55' increases, so that the pressure in the drying chamber 10A 'is reduced. It will be insufficient. Therefore, it is necessary to periodically remove the powder G collected by the bag filter 55 '.
[0004]
As a conventional method for this purpose, it has been attempted to remove the powder G by blowing non-condensed gas as pulsed air to the bag filter 55 '. However, in a high vacuum state, the exhaust speed of the introduced gas is low. For a certain period of time, the pressure in the vacuum system is increased and the operation rate of the apparatus is significantly reduced, so that such a removal operation cannot be performed frequently. In particular, when freeze-drying is performed using the vacuum drying apparatus D 'or when the frozen product G0 obtained by self-freezing the raw material liquid L is vacuum-dried, the pressure in the drying chamber 10A' is increased by introducing pulse air. As a result, the frozen matter G0 is melted and the method using such pulsed air cannot be adopted.
[0005]
[Technical issues to be solved]
The present invention has been made in view of such a background, and it is possible to separate the powder particles collected in the bag filter without lowering the vacuum state in the drying chamber. It is an object of the present invention to develop a new vacuum drying method and an apparatus thereof that can increase the operation rate and efficiently obtain a dried product, and that does not cause melting of a frozen product during freeze drying.
[0006]
[Means for Solving the Problems]
In other words, the vacuum drying method according to claim 1 uses a vacuum drying apparatus in which a vacuum generating device for reducing the pressure in the drying chamber is connected to a housing having an internal space as a drying chamber, and the drying chamber is connected to the housing. In a method of obtaining a dried product by depressurizing and drying the raw material put in the drying chamber under vacuum, a dust collecting chamber is provided between the drying chamber and the vacuum generator, and is provided in the dust collecting chamber. By vibrating the bag filter, the granular material collected by the bag filter is detached.
According to the present invention, it is possible to remove particles from the bag filter without causing a pressure increase in the dust collecting chamber and the drying chamber as in the case of blowing pulsed air to the bag filter. For this reason, vacuum drying can be performed efficiently, and a decrease in the operation rate of the apparatus can be avoided.
[0007]
The vacuum drying method according to claim 2 is characterized in that, in addition to the above requirements, the excitation of the bag filter is performed by expanding and contracting the bag filter.
ADVANTAGE OF THE INVENTION According to this invention, the granular material which adhered to the primary side of the bag filter can be effectively separated.
[0008]
Furthermore, in the vacuum drying method according to the third aspect, in addition to the above requirements, a steam supply port is formed in a pipe connecting the dust collecting chamber and the vacuum generator, and a steam supply port is formed in the steam supply port. And reducing the pressure difference between the primary side and the secondary side of the bag filter.
ADVANTAGE OF THE INVENTION According to this invention, a granular material can be easily detached to the primary side of a bag filter.
[0009]
Furthermore, the vacuum drying method according to claim 4, in addition to the requirements according to claim 3, further includes a portion between the dust collection chamber and the vacuum generator and closer to the vacuum generator than the steam supply port. Is provided with a cold trap, wherein the cold trap agglomerates the steam introduced into the steam supply port.
According to the present invention, by temporarily aggregating the steam having a high pressure in the dust collection chamber by the cold trap, it is possible to quickly return the preceding stage of the vacuum generator to the low pressure, and the vacuum generator is overloaded. This can be prevented.
[0010]
Furthermore, the vacuum drying method according to claim 5 is characterized in that, in addition to the above requirements, the raw material is a frozen product.
According to the present invention, freeze-drying can be performed efficiently.
[0011]
Further, in the vacuum drying method according to the sixth aspect, in addition to the requirements described in the first, second, third or fourth aspect, the raw material is a liquid, and the frozen material obtained by self-freezing the raw material liquid is vacuum-dried. It is characterized in that it is dried to obtain a dried product in the form of a granular material.
According to the present invention, freeze-drying can be performed efficiently.
[0012]
Further, the vacuum drying apparatus according to claim 7 is configured by connecting a vacuum generating device for reducing the pressure in the drying chamber to a housing having an internal space as a drying chamber in a communicating state, and reducing the pressure in the drying chamber. In a device for vacuum-drying a raw material charged into a drying chamber to obtain a dried product, a dust collection chamber is provided between the drying chamber and a vacuum generator, and a bag filter is provided in the dust collection chamber. It is characterized by having a mechanism for exciting the bag filter.
According to the present invention, it is possible to remove particles from the bag filter without causing a pressure increase in the dust collecting chamber and the drying chamber as in the case of blowing pulsed air to the bag filter. For this reason, vacuum drying can be performed efficiently, and a decrease in the operation rate of the apparatus can be avoided.
[0013]
Furthermore, a vacuum drying apparatus according to an eighth aspect is characterized in that, in addition to the requirements described in the seventh aspect, the dust collecting chamber is provided with a mechanism for expanding and contracting the bag filter.
ADVANTAGE OF THE INVENTION According to this invention, the granular material which adhered to the primary side of the bag filter can be effectively separated.
[0014]
Further, in the vacuum drying apparatus according to the ninth aspect, in addition to the requirements according to the seventh or eighth aspect, a steam supply port is formed in a pipe connecting the dust collecting chamber and the vacuum generator. And a steam supply device connected to the steam supply port.
According to the present invention, by introducing steam into the steam supply port and reducing the pressure difference between the primary side and the secondary side of the bag filter, the granular material can be easily detached to the primary side of the bag filter. .
[0015]
Furthermore, the vacuum drying device according to claim 10 is, in addition to the requirements according to claim 9, between the dust collection chamber and the vacuum generator and at a position closer to the vacuum generator than the steam supply port. Is characterized by having a cold trap.
According to the present invention, by temporarily aggregating the steam having a high pressure in the dust collection chamber by the cold trap, it is possible to quickly return the preceding stage of the vacuum generator to the low pressure, and the vacuum generator is overloaded. This can be prevented.
[0016]
Furthermore, in the vacuum drying apparatus according to the eleventh aspect, in addition to the requirements according to the seventh, eighth, ninth, or tenth aspect, the drying chamber is vibrated by a vibrator unit. And a bellows pipe at the center of the drying chamber.
According to the present invention, the vibration of the drying chamber can be absorbed by the bellows pipe, and furthermore, the drying chamber can be prevented from shrinking and being lifted off.
The above object is achieved by using the configuration of the invention described in each of the claims.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the vacuum drying method and the apparatus thereof according to the present invention will be described. First, the configuration of the vacuum drying apparatus D will be described, and then the vacuum drying method will be described together with the operation mode of this apparatus.
A vacuum drying apparatus is denoted by reference numeral D in the figure. The vacuum drying apparatus is configured such that a housing 1 having an internal space of a drying chamber 10A is placed on a base B with an elastic body 2 interposed therebetween, and a housing is provided. 1 is provided with a vibrator unit 3.
Further, in this embodiment, the freezing portion 10B is arranged in communication with the input port 15 of the housing 1, and the raw material liquid supply device 4 is provided above the freezing portion 10B. Further, a dust collecting chamber 5 is arranged in communication with an exhaust port 17 of the housing 1, and a vacuum generating device 6 including a condenser, a vacuum pump, etc., A supply device 7 and a cold trap 8 are provided. A heat medium circulator 9 is connected to the housing 1, and is configured to indirectly heat the inside of the drying chamber 10A.
[0018]
The vacuum drying apparatus D configured as described above introduces the droplet-shaped raw material liquid L (hereinafter, referred to as “sprayed droplet M”) sprayed in the raw material liquid supply device 4 to the freezing unit 10B and self-freezes. The frozen product G0 is formed into a fine-grained frozen product G0. Subsequently, the frozen product G0 is introduced into the drying chamber 10A, and the frozen product G0 is dried while flowing by vibrating the housing 1 by the vibrator unit 3 to perform the drying process. The body G is obtained.
[0019]
Hereinafter, each member constituting the vacuum drying device D will be described in detail. First, the base B will be described. For example, as shown in FIGS. 1 and 2, this base is constituted by appropriately combining steel materials, and four support pillars C stand on the base B. Is established.
[0020]
Next, the housing 1 will be described. The housing 1 is a horizontal cylindrical member having an internal space as a drying chamber 10A. A fixed leg 11 is connected to the side circumference of the housing 1 by four legs. A side plate 12 is provided at the portion so as to be freely opened and closed. A jacket inner plate 13 is provided inside the housing 1 and the side plate 12, a heating medium nozzle 14 is further attached, and a heating medium circulator 9 such as hot water is connected to the heating medium nozzle 14.
[0021]
Further, an inlet 15 is formed in a side peripheral portion of the housing 1, an outlet 16 is formed in a side plate 12 located on the opposite side, and an exhaust outlet 17 is formed substantially in the center of the housing 1. The dust collecting chamber 5 is connected above the exhaust port 17 via a bellows pipe 17A. A measurement port 18 is formed at an appropriate position of the housing 1, and a temperature sensor, a humidity sensor, and the like are attached to the measurement port 18. Sent to control panel. Furthermore, a drain port 19 is formed in the lower part of the housing 1.
[0022]
The outlet 16 is opened and closed by a lid 16a, and the lid 16a approaches and separates from the outlet 16 by operating a handle 16c provided in the duct 16b. Of course, the opening and closing of the lid 16a may be configured so that no manual operation is required by using an appropriate motor or the like.
In this embodiment, the drying chamber 10A is set on the base B with the outlet 16 side inclined downward by 1 to 2 ° with respect to the horizontal line.
[0023]
The freezing section 10B is a cylindrical member connected to the input port 15, and a raw material supply device 4 is provided above the freezing portion 10B. The drying chamber 10A is configured to be in communication with the freezing section 10B.
[0024]
Further, a nozzle 41 to which a spray nozzle or the like is applied, for example, is provided in the liquid supply chamber 40. A raw material tank 42, a pump 43, and a valve 44 are provided in a pipe connected to the nozzle 41. Thus, the raw material liquid L put into the raw material tank 42 can be sprayed into the liquid supply chamber 40.
Further, a valve 45 to which a ball valve is applied is provided between the liquid supply chamber 40 and the drying chamber 10A, for example.
Such a configuration of the freezing unit 10B and the raw material supply device 4 is disclosed in Japanese Patent Application No. 2002-258499 “Method for Supplying Raw Material Liquid to Vacuum Dryer and Its Apparatus” filed by the present applicant. In particular, this is a preferable configuration for freeze-drying the raw material liquid L. In other cases, for example, using a frozen product G0 obtained in another step as a raw material, the raw material is directly supplied into the drying chamber 10A from the input port 15. It is configured to supply.
[0025]
A mount bracket 3a is fixed to the lower part of the outer periphery of the housing 1 as shown in FIG. 1, and a vibrator unit 3 having an eccentric weight is fixed to the mount bracket 3a.
The housing 1 configured as described above is mounted on the base B with an elastic body 2 formed by forming an elastic member such as a spring or a vibration-proof rubber into a column shape as an example.
[0026]
Here, the dust collecting chamber 5 will be described in detail. As shown in FIGS. 1 and 3, the dust collecting chamber 5 is provided for a machine frame F provided so as to straddle the casing 1 mounted on the base B. The communication port 50b formed in the lower lid 50B closing the lower part of the cylindrical housing 50 is connected to the exhaust port 17 by a bellows pipe 17A. The upper part of the housing 50 is closed by the upper lid 50A.
The communication port 50b and the exhaust port 17 are connected by a vertically provided bellows pipe 17A at the center of the drying chamber 10A. Therefore, since the bellows pipe 17A is stretched by the weight of the casing 1, the bellows pipe 17A is not completely contracted due to a decrease in the air pressure in the drying chamber 10A and the dust collecting chamber 5, and the vibration of the casing 1 is reduced. Can be prevented from being transmitted.
[0027]
A bag filter 55 is provided in the housing 50. As shown in FIG. 4, the bag filter 55 is provided with six cylindrical filter parts 55b as an example with respect to a circular base part 55a. is there. The upper end of the filter part 55b is closed by a top plate 55c, and a threading 55d is mounted on the top plate 55c. An annular filter flange 55e is sewn to the edge of the base portion 55a. The filter flange 55e is sandwiched between flange portions provided on the lower portion of the housing 50 and the lower lid 50B, thereby forming a bag filter. 55 is installed in the dust collection chamber 5. The packing P is interposed between the filter flange 55e and the flanges provided in the lower portion of the housing 50 and the lower lid 50B, respectively, to secure the confidentiality of the dust collection chamber 5.
[0028]
Next, a mechanism for extending and contracting the bag filter 55 disposed in the dust collection chamber 5 will be described. First, a rotating shaft 51 is pivotally supported at an upper portion in the housing 50, and a link 52 is connected to the rotating shaft 51, and further, an annular suspension ring 53 is connected to the link 52. . A link 56 is connected to the rotation shaft 51 on the outside of the housing 50, and an arm 57a of a cylinder 57 is connected to the link 56. With such a configuration, the suspension ring 53 moves up and down due to expansion and contraction of the cylinder 57. In this embodiment, the vertical stroke of the suspension ring 53 is set to about 230 mm.
The suspension ring 53 has a plurality of suspension holes 53a formed in a peripheral portion thereof. The string 54 passed through the suspension hole 53a is passed through the string thread 55d, and the suspension By connecting both ends with the eggplant a, the top plate portion 55c is lifted to maintain the shape of the dust filter portion 55b in a cylindrical state.
[0029]
Further, an exhaust pipe 58 is provided on a side peripheral portion of the housing 50. The exhaust pipe 58 is connected to the cold trap 8 as shown in FIG. The vacuum generating device 6 including the above is connected. The exhaust pipe 58 is formed with a steam supply port 58a, and the steam supply port 58a is connected to the steam supply device 7 via a valve 71.
The cold trap 8 has a low-temperature solid surface in the flow path, and condenses a vapor component in a gas that has touched the solid surface.
[0030]
The vacuum drying apparatus D of the present invention is configured as described above as an example. Hereinafter, the vacuum drying method of the present invention will be described together with the operation mode of this apparatus.
(1) Setting of the apparatus Prior to the operation of the vacuum drying apparatus D, both openings of the housing 1 are closed by the side plate 12 and the outlet 16 is closed by the lid 16a. Further, the number of rotations of the vibrator unit 3 is determined in accordance with the shape, particle size, weight, and the like of the frozen matter G0 put into the drying chamber 10A, and the vibration cycle and amplitude are set. In this embodiment, the rotation speed is set to 1800 rpm as an example.
Further, the pressure in the drying chamber 10A controlled by the vacuum generator 6 is set, and the temperature and flow rate of the heat medium circulated by the heat medium circulator 9 are set.
[0031]
(2) Depressurization in the drying chamber and starting the vacuum generator 6 to make the inside of the drying chamber 10A and the freezing part 10B depressurized, and starting the heat medium circulating machine 9 to start circulating supply of the heat medium, Further, the vibrator unit 3 is activated to vibrate the housing 1. Since the dust collecting chamber 5 and the exhaust port 17 of the drying chamber 10A are connected by a bellows pipe 17A, the vibration of the drying chamber 10A is absorbed by the bellows pipe 17A and the dust collecting chamber 5 I don't get it. Furthermore, when the dust collection chamber 5 and the exhaust port 17 of the drying chamber 10A are connected at a place other than the center of the drying chamber 10A, the pressure in the drying chamber 10A and the freezing section 10B is reduced. This shrinks, and the drying chamber 10A is lifted to one side. By connecting the bellows pipe 17A at the center of the drying chamber 10A, such a situation can be avoided.
[0032]
(3) Supply of the raw material liquid and self-freezing Subsequently, the pump 43 is started, and the opening degree of the valve 44 is appropriately adjusted to spray the raw material liquid L from the nozzle 41 into the liquid supply chamber 40. Becomes a mist spray droplet M.
Next, the spray droplet M self-freezes in the process of falling in the freezing portion 10B, and becomes a fine-grained frozen product G0 having a diameter of about 0.3 to 1.5 mm. Thereafter, the frozen material G0 falls into the drying chamber 10A through the input port 15.
In the case other than self-freezing, for example, when the frozen material G0 obtained in another step is used as the raw material, the raw material is supplied from the inlet 15.
[0033]
(4) Drying Operation Next, the frozen matter G0 that has reached the inside of the drying chamber 10A is distributed over a wide area in the longitudinal direction of the drying chamber 10A while flowing under the vibration force from the vibrator unit 3, and in this state, the heat from the heat medium is generated. Is indirectly received and evaporated or sublimated for drying.
The vapor generated at this time reaches the cold trap 8 from the exhaust port 17, where it is condensed and discharged to the outside.
[0034]
(5) Discharging operation The vacuum drying device D is activated when the moisture value of the frozen product G0 is eventually detected to be a desired value by a temperature sensor or the like or when a preset processing time has elapsed. After stopping, the discharge port 16 is opened to discharge to the outside as the powder G in a desired dry state.
[0035]
(6) As the bag filter is cleaned and the drying operation is continued, as shown in FIG. 5 (a), the collected frozen matter G0 and powder G become excessive and the air permeability increases. As a result, the pressure on the primary side (drying chamber 10A side) of the bag filter 55 becomes higher than the pressure on the secondary side (vacuum generator 6 side).
When such a situation occurs, first, the vacuum generator 6 is stopped. Then, the cylinder 57 is contracted, and the suspension ring 53 is lowered by the action of the link 56 and the link 52. With this, the dust filter 55b of the bag filter 55 contracts as shown in FIG. 5 (b). . When the cylinder 57 is further extended from this state, the suspension ring 53 is raised by the action of the link 56 and the link 52, and as a result, the dust filter 55b of the bag filter 55 is moved as shown in FIG. Elongate. By repeating such expansion and contraction of the filter part 55b, the frozen matter G0 and the powder G collected in the filter part 55b are detached from the filter part 55b and enter the drying chamber 10A through the communication port 50b in the lower lid 50B. Is everything.
[0036]
At this time, steam of the same quality as the liquid component generated by evaporation or sublimation of the steam or the frozen matter G0 is supplied from the steam supply device 7 to the steam supply port 58a in the exhaust pipe 58. This steam increases the pressure on the secondary side (on the side of the vacuum generator 6) of the bag filter 55 to reduce the difference from the pressure on the primary side (on the drying chamber 10A side). This makes it possible to easily remove the frozen matter G0 and the granular material G that have been collected in the above.
Further, by applying steam as the gas to be supplied to the exhaust pipe 58, when the vacuum generator 6 is started up again, the atmosphere in the dust collection chamber 5 becomes cold trap 8 before reaching the vacuum generator 6. As a result, the vapor component is condensed, so that the gas reaches the vacuum generator 6 in a state where the pressure is reduced, and the load on the vacuum generator 6 can be reduced.
[0037]
For this reason, the frozen matter G0 and the granular material G collected by the bag filter 55 can be separated without causing a pressure increase in the drying chamber 10a which is in communication with the dust collection chamber 5, and the vacuum again Since the next drying treatment can be performed immediately after the activation of the generator 6, the operating rate of the vacuum drying device D can be increased and the powder G can be obtained efficiently.
[0038]
[Other embodiments]
Although the present invention is based on the above-described embodiment, the following embodiment can be adopted based on the technical idea of the present invention.
First, in the above-described basic embodiment, as a method of exciting the bag filter 55, a configuration in which the bag filter 55 is expanded and contracted is adopted. However, as shown in FIG. A configuration in which the dust filter 55b is vibrated through the suspension ring 53 can be employed. In this case as well, the powder particles collected by the bag filter 55 without causing an increase in the pressure in the drying chamber 10a. The body G can be removed.
[0039]
Further, in the present invention, a vacuum generator 6 for depressurizing the inside of the drying chamber 10A is connected to the casing 1 having an internal space having a drying chamber 10A in a communicating state, and the inside of the drying chamber 10A is depressurized and dried. The present invention is applied to an apparatus for vacuum-drying a raw material charged into the chamber 10A to obtain a granular solid material. Therefore, if it belongs to the category of the so-called "vacuum drying device", in addition to the vibration type vacuum drying device D shown in the basic embodiment, a vacuum conical ribbon vacuum dryer, a vacuum stirring dryer, and a disk Various forms of vacuum dryers, such as a dryer, a belt type continuous vacuum dryer, a double cone type vacuum dryer, a microwave type continuous vacuum dryer, can be applied.
[0040]
【The invention's effect】
According to the present invention, the powder particles G collected by the bag filter 55 can be separated without lowering the vacuum state in the drying chamber 10A, thereby reducing the operating rate of the vacuum drying device D. It is possible to efficiently obtain a dried product by increasing the temperature, and it does not cause melting of the frozen material G0 when freeze-drying is performed.
[Brief description of the drawings]
FIG. 1 is a side view showing a vacuum drying apparatus according to the present invention, partially cut away.
FIG. 2 is a front view and a rear view of the same.
FIG. 3 is a front view, a side view, and a plan view showing a dust collection chamber.
FIG. 4 is a perspective view showing a dust collection chamber partially broken away.
FIG. 5 is a vertical sectional side view showing a state where a bag filter expands and contracts in a dust collection chamber.
FIG. 6 is a side view showing an embodiment in which a suspension ring is vibrated by a vibrator.
FIG. 7 is a longitudinal sectional view showing an existing vacuum dryer.
[Explanation of symbols]
D Vacuum drying device 1 Housing 1b Top plate 10A Drying room 10B Freezing unit 11 Fixed leg 12 Side plate 13 Inner plate 14 Heat medium nozzle 15 Input port 16 Outlet 16a Lid 16b Duct 16c Handle 17 Exhaust port 17A Bellows pipe 18 Measurement Port 19 Drain port 2 Elastic body 3 Vibrator unit 3a Mount bracket 4 Raw material liquid supply device 40 Liquid supply chamber 41 Nozzle 42 Raw material tank 43 Pump 44 Valve 45 Valve 5 Dust collection chamber 50 Housing 50A Upper lid 50B Lower lid 50b Communication port 51 times Active shaft 52 Link 53 Hanging ring 53a Hanging hole 54 String body 54a Naskan 55 Bag filter 55a Base 55b Filtering part 55c Top plate 55d String passing 55e Filter flange 56 Link 57 Cylinder 57a Arm 58 Exhaust pipe 58a Steam supply port 59 Vibrator 6 Vacuum generator 7 Steam supply device 71 Valve 8 Cold trap 9 Heat medium circulator B Base C Support column F Machine frame G0 Frozen matter G Powder L Material liquid M Spray droplet P Packing

Claims (11)

A vacuum drying apparatus was used in which a vacuum generating device for reducing the pressure in the drying chamber was connected to a casing having an internal space as a drying chamber, and the drying chamber was depressurized and charged into the drying chamber. In the method of drying a raw material under vacuum to obtain a dried product, a dust collecting chamber is provided between the drying chamber and a vacuum generator, and a bag filter provided in the dust collecting chamber is vibrated to form a bag. A vacuum drying method, comprising separating powders and particles collected by a filter. 2. The vacuum drying method according to claim 1, wherein the vibration of the bag filter is performed by expanding and contracting the bag filter. A steam supply port is formed in a pipe connecting the dust collecting chamber and the vacuum generator. Steam is introduced into the steam supply port, and the pressure difference between the primary side and the secondary side of the bag filter is changed. 3. The vacuum drying method according to claim 1 or 2, wherein A cold trap is provided between the dust collection chamber and the vacuum generator and at a position closer to the vacuum generator than the steam supply port, and the steam introduced into the steam supply port by the cold trap is provided. 4. The vacuum drying method according to claim 3, wherein agglomeration is performed. 5. The vacuum drying method according to claim 1, wherein the raw material is a frozen product. The raw material is a liquid, and a frozen product obtained by self-freezing the raw material liquid is vacuum-dried to obtain a dried product in the form of a granular material, according to claim 1, 2, or 3. Vacuum drying method. A vacuum generating device for depressurizing the drying chamber is connected to a housing having an internal space as a drying chamber, and the vacuum generating device for depressurizing the drying chamber is connected to the casing. In the apparatus for obtaining dried products, a dust collecting chamber is provided between the drying chamber and the vacuum generator, a bag filter is provided in the dust collecting chamber, and a mechanism for exciting the bag filter is further provided. A vacuum drying device. The vacuum drying device according to claim 7, wherein the dust collecting chamber includes a mechanism for expanding and contracting the bag filter. 9. A steam supply port is formed in a pipe connecting the dust collecting chamber and the vacuum generator, and a steam supply device is connected to the steam supply port. Vacuum drying equipment. 10. The vacuum drying apparatus according to claim 9, further comprising a cold trap between the dust collection chamber and the vacuum generator and at a position closer to the vacuum generator than the steam supply port. The drying chamber is vibrated by a vibrator unit, and the dust collection chamber and an exhaust port of the drying chamber are connected by a bellows pipe at a central portion of the drying chamber. The vacuum drying apparatus according to 8, 9 or 10.

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