JP4019220B2 - Vacuum drying method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to vacuum drying of foods and the like, and relates to a vacuum drying method and apparatus capable of performing an efficient drying process.
[0002]
BACKGROUND OF THE INVENTION
Conventionally, in the processing of granular materials such as foods, pharmaceuticals, agricultural chemicals, feeds, chemicals, etc., a vibratory vacuum drying device has been adopted as one of the devices for vacuum drying raw materials to obtain granular materials. Yes.
As shown in FIG. 7, this vacuum drying apparatus D 'is formed by connecting a vacuum generator 6' for decompressing the inside of the drying chamber 10A 'to a casing 1' having an internal space as a drying chamber 10A '. Is,
The inside of the drying chamber 10A ′ is decompressed and the raw material charged into the drying chamber 10A ′ is vacuum-dried to obtain a granular material G.
[0003]
A bag filter 55 ′ for separating the powder G is provided between the drying chamber 10 A ′ formed in the housing 1 ′ and the vacuum generator 6 ′. 'Is reduced in air permeability due to the collected powder G as the operation of the vacuum drying apparatus D' continues, and the pressure loss before and after the bag filter 55 'increases, so the pressure in the drying chamber 10A' is reduced. It will be insufficient. For this reason, it is necessary to periodically remove the granular material G collected by the bag filter 55 '.
[0004]
As a conventional method for this purpose, attempts have been made to remove the granular material G by spraying the non-condensed gas as pulsed air on the bag filter 55 ', but in a high vacuum state, the introduced gas has a slow exhaust speed. Therefore, since the operation rate of the apparatus is remarkably lowered for a certain period of time due to the pressure in the vacuum system being increased, such removal work 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 introduced when pulsed air is introduced. As the temperature rises and the frozen material G0 melts, such a method using pulsed air cannot be employed.
[0005]
[Technical problem to be solved]
The present invention has been made in view of such a background, and it is possible to detach the granular material collected in the bag filter without lowering the vacuum state in the drying chamber. The technical problem is to develop a new vacuum drying method and apparatus capable of efficiently obtaining a dried product by increasing the operating rate and not causing the frozen material to melt during freeze drying.
[0006]
[Means for Solving the Problems]
That is, the vacuum drying method according to claim 1 uses a vacuum drying apparatus in which a vacuum generator for reducing the pressure in the drying chamber is connected to a casing having an internal space as a drying chamber, and the drying chamber is connected. In the method of obtaining a dried product by vacuum drying the raw material charged in the drying chamber, a dust collection chamber is provided between the drying chamber and the vacuum generator, and the dust collection chamber and the vacuum A steam supply port is formed in a pipe line connecting the generator, and steam is introduced into the steam supply port to reduce a pressure difference between the primary side and the secondary side of the bag filter, and The bag filter provided in the dust collection chamber is vibrated to release the powder particles collected by the bag filter.
According to the present invention, the granular material can be removed from the bag filter without increasing the pressure in the dust collection 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 the fall of the operation rate of an apparatus can be avoided.
In addition, the granular material can be easily detached to the primary side of the bag filter.
[0007]
In addition to the above requirements, the vacuum drying method according to claim 2 is characterized in that the vibration of the bag filter is performed by expanding and contracting the bag filter.
According to this invention, the granular material adhering to the primary side of the bag filter can be effectively separated.
[0008]
Furthermore, in addition to the above requirements , the vacuum drying method according to claim 3 includes a cold trap provided between the dust collection chamber and the vacuum generator, and closer to the vacuum generator than the steam supply port. The steam introduced into the steam supply port is condensed by the cold trap.
According to the present invention, the vapor whose pressure in the dust collection chamber is temporarily high is condensed by the cold trap, so that the front part of the vacuum generator can be quickly returned to low pressure, and the vacuum generator is overloaded. This can be prevented.
[0009]
Furthermore, the vacuum drying method according to claim 4 is characterized in that, in addition to the above requirements, the raw material is a frozen material.
According to this invention, freeze-drying can be performed efficiently.
[0010]
Furthermore, in the vacuum drying method according to claim 5 , in addition to the requirement according to claim 1, 2, or 3 , the raw material is a liquid, and a frozen material obtained by self-freezing the raw material liquid is vacuum-dried. Thus, it is characterized by obtaining a dry product in the form of a granular material.
According to this invention, freeze-drying can be performed efficiently.
[0011]
According to a sixth aspect of the present invention, there is provided a vacuum drying apparatus comprising: a housing having an internal space as a drying chamber; and a vacuum generator for depressurizing the drying chamber connected in a communicating state. In an apparatus for obtaining a dried product by vacuum drying the raw material charged in the drying chamber, a dust collecting chamber is provided between the drying chamber and the vacuum generator, and a bag filter is provided in the dust collecting chamber.
Further, a mechanism for exciting the bag filter is provided, and a steam supply port is formed in a pipe line connecting the dust collection chamber and the vacuum generator, and the steam supply device is connected to the steam supply port. It is characterized by connecting .
According to the present invention, the granular material can be removed from the bag filter without increasing the pressure in the dust collection 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 the fall of the operation rate of an apparatus can be avoided.
Further, 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 powder particles can be easily detached from the primary side of the bag filter.
[0012]
Furthermore, the vacuum drying apparatus according to claim 7 is characterized in that, in addition to the requirement of claim 6 , the dust collection chamber is provided with a mechanism for expanding and contracting the bag filter.
According to this invention, the granular material adhering to the primary side of the bag filter can be effectively separated.
[0013]
Furthermore, the vacuum drying apparatus according to claim 8 is in addition to the requirements of claim 6 or 7 , and is located between the dust collection chamber and the vacuum generation apparatus and closer to the vacuum generation apparatus than the vapor supply port. The place is characterized by having a cold trap.
According to the present invention, the vapor whose pressure in the dust collection chamber is temporarily high is condensed by the cold trap, so that the front part of the vacuum generator can be quickly returned to low pressure, and the vacuum generator is overloaded. This can be prevented.
[0014]
Furthermore, in the vacuum drying apparatus according to claim 9 , in addition to the requirements of claim 6, 7 or 8 , the drying chamber is vibrated by a vibrator unit, and the dust collection chamber and the exhaust in the drying chamber are exhausted. It is characterized in that it is connected to the mouth by a bellows pipe at the center of the drying chamber.
According to the present invention, it is possible to prevent the drying chamber from absorbing vibrations by the bellows piping, and further to prevent the drying chamber from contracting and lifting up.
The above problems can be solved by using the configuration of the invention described in each of the claims as a means.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The vacuum drying method and apparatus of the present invention will be described below. 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 the apparatus.
What is indicated by a symbol D in the figure is a vacuum drying apparatus, which places a casing 1 having an internal space as a drying chamber 10A on a base B with an elastic body 2 interposed therebetween. 1 is provided with a vibrator unit 3.
In this embodiment, the freezing part 10B is arranged in communication with the insertion port 15 in the housing 1, and the raw material liquid supply device 4 is provided above the freezing part 10B. Further, the dust collection chamber 5 is arranged in communication with the exhaust port 17 in the casing 1, and a vacuum generator 6 comprising a condenser, a vacuum pump, etc. is provided downstream of the dust collection chamber 5, steam. A supply device 7 and a cold trap 8 are provided. The casing 1 is connected to a heat medium circulating machine 9 and is configured to indirectly heat the inside of the drying chamber 10A.
[0016]
The vacuum drying apparatus D configured in this way guides the droplet-shaped raw material liquid L (hereinafter referred to as sprayed liquid droplet M) sprayed in the raw material liquid supply apparatus 4 to the freezing unit 10B and self-freezes it. The frozen product G0 is made into a fine-grained frozen product G0. Subsequently, the frozen product G0 is guided into the drying chamber 10A and the casing 1 is vibrated by the vibrator unit 3, and the frozen product G0 is dried while being fluidized. The body G is obtained.
[0017]
Hereinafter, each member constituting the vacuum drying apparatus D will be described in detail. First, the base B will be described. As an example, the base B is configured by appropriately combining steel materials as shown in FIGS. 1 and 2, and four support pillars C stand on the base B. Established.
[0018]
Next, the case 1 will be described. This is a horizontally-placed cylindrical member having an internal space as a drying chamber 10A. Four fixed legs 11 are connected to the side periphery of the case 1, and both cylindrical openings are opened. The side plate 12 is provided in the part so that opening and closing is possible. Further, an inner jacket plate 13 is provided inside the housing 1 and the side plate 12, and a heat medium nozzle 14 is attached to the heat medium nozzle 14, and a heat medium circulating machine 9 such as hot water is connected to the heat medium nozzle 14.
[0019]
In addition, an inlet 15 is formed in the side periphery of the housing 1, a discharge port 16 is formed in the side plate 12 located on the opposite side, and an exhaust port 17 is formed in the approximate center of the housing 1. The dust collection chamber 5 is connected above the exhaust port 17 with a bellows pipe 17A interposed therebetween. In addition, a measurement port 18 is formed at an appropriate location of the casing 1, and a temperature sensor, a humidity sensor, and the like are attached to the measurement port 18, and data measured by these are not shown in the drawing. Sent to the control panel. Furthermore, a drain port 19 is formed in the lower part of the housing 1.
[0020]
The discharge port 16 is opened and closed by a lid body 16a. The lid body 16a approaches and separates from the discharge port 16 by operating a handle 16c provided in the duct 16b. Of course, the lid 16a can be opened and closed by using a motor as appropriate so that no manual operation is required.
In this embodiment, the drying chamber 10A is installed on the base B in a state where the discharge port 16 side is inclined downward by 1 to 2 ° with respect to the horizontal line.
[0021]
The freezing section 10B is a cylindrical member connected to the charging port 15, and a raw material liquid supply device 4 is provided above the freezing section 10B, and a liquid supply chamber 40 in the raw material liquid supply apparatus 4 is provided. The drying chamber 10A is configured to be in communication with the freezing unit 10B.
[0022]
Further, the liquid supply chamber 40 is provided with, for example, a nozzle 41 to which a spray nozzle or the like is applied. A raw material tank 42, a pump 43 and a valve 44 are provided for a pipe line connected to the nozzle 41. Thus, the raw material liquid L introduced into the raw material tank 42 can be sprayed into the liquid supply chamber 40.
Furthermore, a valve 45 to which a ball valve is applied is provided as an example between the liquid supply chamber 40 and the drying chamber 10A.
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 of supplying raw material liquid to a vacuum dryer and its device” which is a patent application filed by the present applicant. Particularly, this is a preferable configuration for freeze-drying the raw material liquid L, but in other cases, such as using a frozen material G0 obtained in a separate process as a raw material, the raw material is directly fed into the drying chamber 10A from the inlet 15 It is set as the structure which supplies.
[0023]
A mounting 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 mounting bracket 3a.
The casing 1 configured as described above is placed on the base B with an elastic body 2 formed by columnar elastic members such as springs and vibration-proof rubber as an example.
[0024]
Here, the dust collection chamber 5 will be described in detail. As shown in FIGS. 1 and 3, the dust collection chamber 5 is provided for a machine frame F provided to straddle the casing 1 placed on the base B. The communication port 50b formed in the lower lid 50B that closes the lower portion of the cylindrical casing 50 is connected to the exhaust port 17 by the bellows pipe 17A. The upper portion of the housing 50 is closed by the upper lid 50A.
The communication port 50b and the exhaust port 17 are connected by a bellows pipe 17A provided vertically at the center of the drying chamber 10A. Accordingly, 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 atmospheric pressure in the drying chamber 10A and the dust collecting chamber 5, and the vibration of the casing 1 is caused to vibrate. It is possible to prevent it from being transmitted to.
[0025]
A bag filter 55 is provided in the housing 50. This bag bag has six cylindrical filter portions 55b as an example with respect to a circular base portion 55a as shown in FIG. is there. The upper end of the filtering portion 55b is closed by a top plate portion 55c, and a string thread 55d is attached on the top plate portion 55c. An annular filter flange 55e is sewn into the edge of the base portion 55a, and the filter flange 55e is sandwiched between flange portions provided on the lower portion of the casing 50 and the lower lid 50B, whereby a bag filter 55 is installed in the dust collection chamber 5. In addition, the confidentiality of the dust collection chamber 5 is ensured by interposing the packing P between the flange provided on the lower part of the casing 50 and the lower cover 50B and the filter flange 55e.
[0026]
Next, a mechanism for expanding and contracting the bag filter 55 arranged in the dust collection chamber 5 will be described. First, a rotating shaft 51 is pivotally supported on the upper portion of the housing 50, and a link 52 is connected to the rotating shaft 51, and an annular suspension ring 53 is connected to the link 52. . A link 56 is connected to the rotating shaft 51 on the outside of the housing 50, and an arm 57 a of a cylinder 57 is connected to the link 56. With such a configuration, the suspension ring 53 moves up and down by the 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 is formed with a plurality of suspension holes 53a on the side peripheral portion thereof. The string body 54 passed through the suspension hole 53a is passed through the string passage 55d, and the string body 54 By connecting both ends with an eggplant 54a, the top plate portion 55c is lifted and the shape of the dust filtering portion 55b is maintained in a cylindrical state.
[0027]
Further, an exhaust pipe 58 is provided on a side peripheral portion of the casing 50, and the exhaust pipe 58 is connected to a cold trap 8 as shown in FIG. A vacuum generator 6 comprising such as is connected. A steam supply port 58a is formed in the exhaust pipe 58, and a steam supply device 7 is connected to the steam supply port 58a through a valve 71.
The cold trap 8 has a low-temperature solid surface in the flow path, and condenses vapor components in the gas that touches the solid surface.
[0028]
The vacuum drying apparatus D of the present invention is configured as described above as an example, and the vacuum drying method of the present invention will be described below together with the operation mode of this apparatus.
(1) Setting of the apparatus Prior to the operation of the vacuum drying apparatus D, both the openings of the housing 1 are closed by the side plate 12, and the discharge port 16 is closed by the lid 16a. Further, the number of rotations of the vibrator unit 3 is determined according to the shape, particle size, weight, etc. of the frozen material G0 put into the drying chamber 10A, and the vibration period and amplitude are set. In this embodiment, as an example, the rotation speed is 1800 rpm.
Furthermore, the pressure in the drying chamber 10A adjusted 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.
[0029]
(2) Depressurization in the drying chamber Then, the vacuum generator 6 is activated to bring the drying chamber 10A and the freezing part 10B into a depressurized state, and the heating medium circulator 9 is activated to start circulating supply of the heating medium. Further, the vibrator unit 3 is activated to vibrate the housing 1. Since the dust collection chamber 5 and the exhaust port 17 in 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 is contained in the dust collection chamber 5. I don't get it. Furthermore, when the dust collection chamber 5 and the exhaust port 17 in the drying chamber 10A are connected at a place other than the central portion of the drying chamber 10A, the pressure in the drying chamber 10A and the freezing portion 10B is reduced. Although this thing contracts and the drying chamber 10A is offset and lifted, such a situation can be avoided by connecting the bellows pipe 17A at the center of the drying chamber 10A.
[0030]
(3) Supply of 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 into the liquid supply chamber 40 from the nozzle 41. Becomes a mist-like spray droplet M.
Next, the spray droplet M is self-frozen in the process of falling in the freezing part 10B,
It becomes a fine granular frozen material 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 charging port 15.
Note that the raw material is supplied from the inlet 15 in cases other than self-freezing, such as when the frozen material G0 obtained in a separate process is used as the raw material.
[0031]
(4) Drying operation Next, the frozen material G0 that has reached the inside of the drying chamber 10A is distributed over the 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 Indirectly evaporates or sublimates and dries.
Further, 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.
[0032]
(5) Discharging operation When the moisture content of the frozen material G0 eventually becomes a desired value by a temperature sensor or the like, or when a preset processing time has elapsed, the vacuum dryer D is turned on. Then, the discharge port 16 is opened and discharged to the outside as the granular material G in a desired dry state.
[0033]
(6) Cleaning of the bag filter As the drying operation is continued, the bag filter 55 becomes air-permeable as the collected frozen material G0 and the granular material G become excessive as shown in FIG. 5 (a). It is significantly reduced,
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, the vacuum generator 6 is first 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, and accordingly, the dust portion 55b of the bag filter 55 contracts as shown in FIG. 5 (b). . Further, when the cylinder 57 is extended from this state, the suspension ring 53 is raised by the action of the link 56 and the link 52, and accordingly, the dust portion 55b of the bag filter 55 is as shown in FIG. 5 (a). Elongate. By repeating such expansion and contraction of the dust portion 55b, the frozen material G0 and the granular material G collected in the dust portion 55b are detached from this, and enter the drying chamber 10A through the communication port 50b in the lower lid 50B. It is everything.
[0034]
At this time, vapor having the same quality as the liquid component generated by evaporation or sublimation of water vapor or frozen material G0 is supplied from the vapor supply device 7 to the vapor supply port 58a in the exhaust pipe 58. This steam increases the pressure on the secondary side (vacuum generator 6 side) of the bag filter 55 to reduce the difference from the pressure on the primary side (drying chamber 10A side), and thereby the dust portion 55b. It is possible to easily remove the frozen material G0 and the granular material G that have been collected in the container.
Further, by applying steam as the gas supplied to the exhaust pipe 58 in this way, when the vacuum generator 6 is started again, the atmosphere in the dust collection chamber 5 is changed to the cold trap 8 before reaching the vacuum generator 6. As a result, the vapor component is condensed, so that the vacuum generator 6 is reached in a state where the pressure is reduced, and the load on the vacuum generator 6 can be reduced.
[0035]
For this reason, the frozen material G0 and the granular material G collected by the bag filter 55 can be detached without causing an increase in pressure in the drying chamber 10a that is in communication with the dust collection chamber 5, and the vacuum is again applied. Since the next drying treatment can be performed immediately after starting the generator 6, the operating rate of the vacuum dryer D can be increased and the granular material G can be obtained efficiently.
[0036]
[Other embodiments]
Although the present invention is based on the above-described embodiment, the following embodiment can also be adopted based on the technical idea of the present invention.
First, in the basic embodiment described above, a configuration in which the bag filter 55 is expanded and contracted is adopted as a method of exciting the bag filter 55. However, as shown in FIG. It is possible to adopt a configuration in which the dust filtering part 55b is vibrated through the suspension ring 53. In this case also, the powder particles collected by the bag filter 55 without causing an increase in pressure in the drying chamber 10a. The body G can be detached.
[0037]
Further, in the present invention, a vacuum generator 6 for reducing the pressure inside the drying chamber 10A is connected to the casing 1 having an internal space as the drying chamber 10A, and the inside of the drying chamber 10A is decompressed and dried. A device for obtaining a powdery solid material by vacuum drying the raw material charged into the chamber 10A is an application target. Therefore, as long as it belongs to the category of so-called “vacuum drying apparatus”, in addition to the vibration type vacuum drying apparatus D shown in the basic embodiment, a vacuum cone type ribbon vacuum dryer, a vacuum stirring dryer, a disk Various types of vacuum drying apparatuses such as a dryer, a belt-type continuous vacuum dryer, a double cone type vacuum dryer, and a microwave-type continuous vacuum dryer can be applied.
[0038]
【The invention's effect】
According to the present invention, the granular material G collected by the bag filter 55 can be released without reducing the vacuum state in the drying chamber 10A, thereby increasing the operating rate of the vacuum drying device D. The dried product can be efficiently obtained by increasing the temperature, and when the freeze-drying is performed, the frozen material G0 is not melted.
[Brief description of the drawings]
FIG. 1 is a side view of a vacuum drying apparatus according to the present invention, partially broken 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 the dust collecting chamber in a partially broken view.
FIG. 5 is a vertical side view showing how the bag filter expands and contracts in the 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 dryer 1 Case 1b Top plate 10A Drying chamber 10B Freezing part 11 Fixed leg 12 Side plate 13 Jacket inner plate 14 Heat medium nozzle 15 Input port 16 Outlet port 16a Lid 16b Duct 16c Handle 17 Exhaust port 17A Bellows piping 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 Moving shaft 52 Link 53 Suspension ring 53a Suspension hole 54 String body 54a Naskan 55 Bag filter 55a Base 55b Dust filter part 55c Top plate part 55d String passage 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 material G Powder L Material liquid M Spray droplet P Packing

Claims (9)

Using a vacuum drying device in which a vacuum generator for reducing the pressure inside the drying chamber is connected to a housing having an internal space as a drying chamber, the drying chamber is decompressed and put into the drying chamber. In the method of obtaining a dried product by vacuum drying the raw material, a dust collection chamber is provided between the drying chamber and the vacuum generator, and a steam pipe is connected to the pipe connecting the dust collection chamber and the vacuum generator. are those supply port is formed, this steam supply port introducing steam, the addition to reduce the pressure difference between the primary side and the secondary side of the bag filter, pressurize the bag filter provided in said dust collecting chamber A vacuum drying method characterized by detaching the granular material collected by the bag filter by shaking.   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 cold trap is provided between the dust collection chamber and the vacuum generator and closer to the vacuum generator than the steam supply port, and the steam introduced into the steam supply port by the cold trap. vacuum drying method according to claim 1 or 2, wherein the coagulating. The raw material according to claim 1, 2 or 3 vacuum drying method wherein a is frozen product. 4. The vacuum drying according to claim 1, 2 or 3, wherein the raw material is a liquid, and a frozen product obtained by self-freezing the raw material liquid is vacuum-dried to obtain a dry product in a granular form. Method. A vacuum generator for reducing the pressure inside the drying chamber is connected to a casing having an internal space as a drying chamber, and the drying chamber is depressurized and the raw material charged in the drying chamber is vacuum dried. In the apparatus for obtaining a dried product, 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. Furthermore, a vapor supply port is formed in a pipe line connecting the dust collection chamber and the vacuum generator, and a vapor supply device is connected to the vapor supply port . The vacuum drying apparatus according to claim 6 , wherein the dust collection chamber includes a mechanism for expanding and contracting the bag filter. The vacuum drying apparatus according to claim 6 or 7 , further comprising a cold trap between the dust collection chamber and the vacuum generator and closer to the vacuum generator than the steam supply port. The said drying chamber is vibrated by a vibrator unit, and the dust collecting chamber and the exhaust port in the drying chamber are connected by a bellows pipe at the center of the drying chamber . The vacuum drying apparatus according to 7 or 8 .

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