JP5927066B2 - Drying apparatus and drying method - Google Patents

Description

  The present invention relates to a drying apparatus and a drying method.

  As a method of drying powder (hereinafter referred to as a work) wetted with moisture, the work is put in a container made of a heat transfer material, the container is accommodated in a vacuum dryer, and the inside of the vacuum dryer is brought to a normal pressure or less. A method of heating the container is also known (see, for example, Patent Document 1).

  In addition, a method is known in which a workpiece is applied to the surface of a heated rotating drum, evaporated and dried, and the resulting dried product is pulverized with a pulverizer (see, for example, Patent Document 2).

  Furthermore, a method is known in which porous particles are mixed in a workpiece, moisture is adsorbed to the porous particles, and then classified to collect powder (see, for example, Patent Document 3).

  In addition, a method is known in which moisture frozen by storing a work frozen in a freezer in a processing chamber of a drying apparatus and putting the processing chamber in a high vacuum state (see, for example, Patent Document 4).

JP 2002-139279 A JP 2009-249473 A JP 2003-254668 A Japanese Patent Laid-Open No. 11-276571

  In the method described in Patent Document 1, since the pressure in the chamber is high, it takes time for moisture to evaporate from the workpiece, and much time is required for drying the workpiece. Furthermore, in this method, there is a possibility that the powders adhere to each other and the dried product becomes agglomerated. Therefore, it is necessary to pulverize the dried product with a pulverizer as described in Patent Document 2.

  Moreover, in the method of patent document 3, after drying a workpiece | work, in order to obtain only powder from a dried material, you have to classify | categorize. Therefore, it takes a lot of time to obtain a dry powder.

  In addition, the method described in Patent Document 4 requires a refrigeration facility for freezing the workpiece. Moreover, since the process of freezing the work is necessary, it takes a lot of time to dry the work.

  The present invention has been made paying attention to such problems, and an object of the present invention is to provide a drying apparatus and a drying method capable of efficiently drying an object to be dried.

In order to achieve the above object, a drying apparatus according to the first aspect of the present invention comprises:
A chamber in which a processing chamber for drying an object to be dried is formed and a through hole is formed to communicate the processing chamber with the outside;
Heating means for heating the object to be dried;
Pressure adjusting means connected to the through-hole to bring the processing chamber in a reduced pressure state lower than normal pressure;
Pressure detecting means for detecting the pressure in the processing chamber;
When the pressure detecting means detects that the pressure in the processing chamber has dropped to a first pressure lower than 600 Pa, the heating means is operated, and a second lower than 600 Pa and higher than the first pressure. Control means for stopping the heating means when it is detected that the pressure has risen,
It is characterized by providing.

In order to achieve the object, the drying method according to the second aspect of the present invention comprises:
Storing the object to be dried in the processing chamber of the drying apparatus;
Bringing the processing chamber into a reduced pressure state lower than normal pressure with a pressure adjusting means;
Heating the material to be dried when the pressure in the processing chamber drops to a first pressure lower than 600 Pa;
A step of stopping heating of the object to be dried when the pressure in the processing chamber rises to a second pressure lower than 600 Pa and higher than the first pressure;
It is characterized by including.

  The pressure adjusting means may be a water ring vacuum pump and a mechanical booster pump.

  The first pressure may be 150 to 300 Pa, and the second pressure may be 350 to 500 Pa.

  ADVANTAGE OF THE INVENTION According to this invention, the drying apparatus and drying method which can dry a to-be-dried body efficiently can be provided.

It is a figure which shows typically the drying apparatus which concerns on embodiment of this invention. It is a figure which shows the state of water. It is a figure which shows typically the aqueous solution which the powder dried with the drying apparatus which concerns on embodiment of this invention melt | dissolved, (a) is a figure which shows the state in which aqueous solution was mounted on the workpiece mounting base, (b) is a figure which shows the state where the water | moisture content of aqueous solution is a liquid, (c) is a figure which shows the state which the water | moisture content of aqueous solution was frozen. It is a graph which shows the process of drying the aqueous solution which concerns on embodiment of this invention. It is a table which shows operation | movement of the drying apparatus which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the following embodiment and drawing. It goes without saying that the following embodiments and drawings can be modified without changing the gist of the present invention.

  A drying apparatus according to an embodiment of the present invention will be described.

  As shown in FIG. 1, the drying apparatus 10 includes a chamber 20, a vacuum pump unit 40, and a control unit 100. The drying apparatus 10 shown in FIG. 1 will be described below with the upper side of the drawing as “upper side”, the lower side of the drawing as “lower side”, the left side of the drawing as “left side”, and the right side of the drawing as “right side”.

  The chamber 20 has a sealed door 20a on the left side, and is formed in a substantially rectangular parallelepiped box shape. A processing chamber 21 for drying the workpiece W is formed in the chamber 20.

  In the processing chamber 21, a work mounting table 24 for mounting the work W is formed.

  As shown in FIG. 1, in order to heat the workpiece W, heaters 22 are disposed on the upper wall, the lower wall and the right wall of the chamber 20 and the sealing door 20a. A heater 23 is disposed on the work mounting table 24. The heaters 22 and 23 are, for example, sheathed heaters whose temperature can be adjusted between 60 and 80 ° C. The heaters 22 and 23 may be heat medium heaters that circulate a heat medium (oil, hot water, etc.) by arranging a flow pipe inside each wall or inside the workpiece mounting table 24.

  As shown in FIG. 1, the processing chamber 21 is provided with a pressure sensor 28 that measures the pressure in the processing chamber 21. As the pressure sensor 28, a piezoelectric type using a piezoelectric effect, a type using a diaphragm, a type integrating a strain gauge and a diaphragm, or the like can be used. Further, a temperature sensor (not shown) for measuring the temperature in the processing chamber 21 may be provided in the processing chamber 21.

  Further, an exhaust port 36 that communicates the processing chamber 21 and the outside of the chamber 20 is formed on the right side wall of the chamber 20. A conduit 37 is connected to the exhaust port 36. A gas exhaust valve 38 is connected to the conduit 37. The gas exhaust valve 38 is formed of a three-way valve that can be switched in the direction of the outside air. A vacuum pump unit 40 is connected to the gas exhaust valve 38.

  The vacuum pump unit 40 is composed of a water ring vacuum pump 41 and a mechanical booster pump 42.

  Unlike a rotary pump using oil, the water ring vacuum pump 41 is a vacuum pump configured to perform vacuum sealing, lubrication of a rotating portion, and cooling of a sliding portion with water. Therefore, the water-sealed vacuum pump 41 is suitable for discharging a gas containing water vapor. The water ring vacuum pump 41 has the ability to reach the pressure in the processing chamber 21 to, for example, about 2000 Pa. In order to further increase the degree of vacuum, an air ejector (not shown) may be attached to the water ring vacuum pump 41.

  A mechanical booster pump 42 is disposed between the water ring vacuum pump 41 and the gas exhaust valve 38. The mechanical booster pump 42 is a vacuum pump used in combination with a water-sealed vacuum pump or the like when a high exhaust speed is required. By combining the mechanical booster pump 42 with the water-sealed vacuum pump 41, the pressure in the processing chamber 21 can be made to reach, for example, about 10 Pa.

  When the vacuum pump unit 40 is operated in a state where the gas exhaust valve 38 is opened so that the processing chamber 21 and the vacuum pump unit 40 communicate with each other, the gas in the processing chamber 21 is sucked into the vacuum pump unit 40, It passes through the gas exhaust valve 38 and is exhausted from the water ring vacuum pump 41. Thereby, the inside of the processing chamber 21 is in a vacuum state.

  The control unit 100 is composed of a computer and controls the operation of the drying apparatus 10. Specifically, the control unit 100 performs heating of the heaters 22 and 23, operation of the pressure sensor 28, opening and closing of the gas exhaust valve 38, and water-sealed vacuum according to a control program stored in the storage unit in the control unit 100. By supplying a control signal for controlling the operation of the pump 41 and the mechanical booster pump 42 to each unit, the operation of the drying apparatus 10 is controlled through a driver drive circuit (not shown). As will be described later, the control unit 100 controls the heaters 22 and 23 to be turned on or off based on a signal from the pressure sensor 28.

  Here, the three states of water will be described. As shown in FIG. 2, water exists in any state of gas, liquid, and solid. The three states are divided by a vapor pressure curve A indicating the boundary between the gas and the liquid, a sublimation curve B indicating the boundary between the gas and the solid, and a dissolution curve C indicating the boundary between the solid and the liquid. The triple point T is where these three states overlap. The triple point T is a point where the temperature is about 0.01 ° C. and the pressure is about 611 Pa. At a pressure and temperature lower than the triple point T, ice and water vapor are in an equilibrium state. When heat is applied to ice in this state, the state changes from ice to water vapor due to the sublimation phenomenon.

  In the present embodiment, after the processing chamber 21 containing the workpiece W is set to a pressure of 600 Pa or less to freeze the moisture contained in the workpiece W, the workpiece W is heated with a heater so that the moisture does not melt. Then, the work W is dried by sublimating moisture.

  Next, the drying method of the workpiece | work W performed using the drying apparatus 10 which concerns on this embodiment comprised as mentioned above is demonstrated. As an example, a case where the workpiece W is an aqueous solution W1 in which powder is dissolved and the room temperature is 25 ° C. will be described.

  First, the aqueous solution W1 is introduced into the processing chamber 21 (see FIG. 1). As shown to Fig.3 (a) and (b), the space | interval of the powder particle W11 and the powder particle W12 is L1, and the water | moisture content which is a liquid intervenes among these.

  Next, the power of the drying apparatus 10 (see FIG. 1) is turned on. The control unit 100 opens the gas exhaust valve 38 and operates the vacuum pump unit 40 (water-sealed vacuum pump 41 and mechanical booster pump 42). Thereby, as shown to a of FIG. 4, the process chamber 21 is pressure-reduced.

  When the pressure in the processing chamber 21 reaches 3166 Pa, which is the vapor pressure of water at 25 ° C. (see b in FIG. 4), the moisture contained in the aqueous solution W1 starts to evaporate. In addition, when a part of the water becomes water vapor, the decompression speed of the processing chamber 21 decreases as shown in FIG.

  Furthermore, when the pressure in the processing chamber 21 reaches 611 Pa, which is the vapor pressure of water at 0 ° C. (see d in FIG. 4), the water contained in the workpiece W is frozen. When water is frozen, its volume is about 1.1 times that of the liquid state. Therefore, as shown in FIG. 3 (c), the volume of moisture intervening between the powder particles W11 and the powder particles W12 increases, so the interval between the powder particles is L1 before freezing (see FIG. 3 (b)). ) Is larger than L2.

  Further, at this time (see d in FIG. 4), the frozen water is sublimated. Since the amount of water that becomes water vapor by sublimation is smaller than the amount of water that becomes water vapor by evaporation (see c in FIG. 4), the pressure reduction rate of the processing chamber 21 increases as shown in e of FIG.

  Then, as shown in f of FIG. 4, when the pressure in the processing chamber 21 is reduced to, for example, 165 Pa (water vapor pressure at −15 ° C.), the control unit 100 prompts moisture sublimation. 22 and the heater 23 of the workpiece mounting table 24 are turned on (see FIG. 5).

  Thereby, since the aqueous solution W1 is supplied with heat, the amount of sublimated water increases. And since the frozen water | moisture content turns into water vapor | steam, as shown to g of FIG. 4, the pressure in the process chamber 21 rises.

  Next, as shown in h of FIG. 4, when the pressure in the processing chamber 21 rises to, for example, 476 Pa (water vapor pressure at −3 ° C.), the controller 100 controls the chamber 20 to prevent dissolution of moisture. The heater 22 and the heater 23 of the work mounting table 24 are turned off (see FIG. 5). Thereby, since heat is no longer supplied to the aqueous solution W1, the amount of sublimated water is reduced. And as shown to i of FIG. 4, the pressure of the process chamber 21 falls again.

  Then, as shown in j of FIG. 4, when the pressure in the processing chamber 21 is reduced to 165 Pa, the control unit 100 turns on the heater 22 of the chamber 20 and the heater 23 of the workpiece mounting table 24 in order to promote moisture sublimation. (See FIG. 5). As described above, since the frozen water becomes water vapor, the pressure in the processing chamber 21 rises again as indicated by k in FIG.

  As described above, by repeatedly turning on and off the heaters 22 and 23 while the vacuum pump unit 40 is operated for a predetermined time, the water contained in the aqueous solution W1 is sublimated and almost removed. . Then, when most of the water contained in the aqueous solution W1 is removed, the pressure in the processing chamber 21 is reduced to 165 Pa as shown in l of FIG. 4, and the control unit 100 controls the heater 22 and the workpiece mounting table in the chamber 20. Even if the heater 23 is turned on, the pressure in the processing chamber 21 continues to decrease.

  When the pressure in the processing chamber 21 reaches, for example, 103 Pa (see m in FIG. 4), the control unit 100 determines that moisture has been removed from the aqueous solution W1, that is, an object to be dried has been obtained, and the vacuum pump unit 40 is turned on. Stop (see FIG. 5).

  And the control part 100 opens the gas exhaust valve 38, and makes the pressure in the process chamber 21 equivalent to a normal pressure. Thereafter, when the temperature of the object to be dried becomes equal to room temperature, the sealed door 20a is opened and the object to be dried is taken out.

  As described above, moisture can be removed from the aqueous solution W1 using the drying apparatus 10 to obtain an object to be dried.

  As described above, according to the drying apparatus 10 of the present embodiment, since the work W is frozen by evacuating the processing chamber to 600 Pa or less, a step of freezing using a freezer or the like is not necessary. Therefore, the drying time of the workpiece W can be shortened.

  Also, at 260 Pa (water vapor pressure at −10 ° C. of water) at which the water contained in the workpiece W is sufficiently frozen, the heaters 22 and 23 are turned on, and 437 Pa (water at −4 ° C. of water does not dissolve) Since the heaters 22 and 23 are turned off by pressure), the moisture does not melt and the moisture can be surely sublimated.

  Further, since the water is sublimated in a frozen state, the cavity formed between the powder particles W11 and the powder particles W12 becomes larger than when the liquid is evaporated in a liquid state. Therefore, a fine powder can be obtained without the powders being in close contact with each other.

  Moreover, since the water-sealed vacuum pump 41 suitable for discharging gas containing water vapor is used, it is not necessary to use a cold trap that requires a large installation place. Further, since no cold trap is used, the cost can be reduced.

  In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible.

  For example, in the above embodiment, the heaters 22 and 23 are turned on when it is detected that the pressure in the processing chamber 21 has decreased to 260 Pa, and the heaters 22 and 23 are detected when it has been detected that the pressure has increased to 437 Pa. Turned off. However, the pressure at which the heater is turned on or off is not limited to these. For example, you may determine suitably according to the kind, thickness, shape, or moisture content of a to-be-dried object.

  For example, the pressure in the processing chamber 21 for turning on the heaters 22 and 23 may be a pressure at which moisture contained in the material to be dried is sufficiently frozen, and is preferably 150 to 300 Pa. Further, the pressure in the processing chamber 21 for turning off the heaters 22 and 23 may be a pressure at which the moisture contained in the material to be dried does not dissolve, and preferably 350 to 500 Pa.

  Further, in the above embodiment, the pressure in the processing chamber 21 continues to decrease even when the heaters 22 and 23 are turned on, and it is considered that moisture has been removed from the workpiece W by reaching a predetermined pressure. However, the present invention is not limited to this. For example, if the state in which the pressure in the processing chamber 21 does not increase even when the heaters 22 and 23 are turned on continues for a predetermined time, it is assumed that moisture has been removed from the workpiece W, and the vacuum pump unit 40 is stopped. May be.

  Moreover, in the said embodiment, although the workpiece | work W was set to the aqueous solution W1 in which the powder melt | dissolved as an example, it is not limited to this. For example, the workpiece W may be a porous material such as activated carbon or zeolite, a polymer solution in which a polymer is dissolved in a solvent, or a powder wet with water.

DESCRIPTION OF SYMBOLS 10 Drying apparatus 20 Chamber 20a Sealed door 21 Processing chamber 22 Heater 23 Heater 24 Workpiece mounting table 28 Pressure sensor 36 Exhaust port 37 Conduit 38 Gas exhaust valve 40 Vacuum pump unit 41 Water seal vacuum pump 42 Mechanical booster pump

Claims (6)

A chamber in which a processing chamber for drying an object to be dried is formed and a through hole is formed to communicate the processing chamber with the outside;
Heating means for heating the object to be dried;
Pressure adjusting means connected to the through-hole to bring the processing chamber in a reduced pressure state lower than normal pressure;
Pressure detecting means for detecting the pressure in the processing chamber;
When the pressure detecting means detects that the pressure in the processing chamber has dropped to a first pressure lower than 600 Pa, the heating means is operated, and a second lower than 600 Pa and higher than the first pressure. Control means for stopping the heating means when it is detected that the pressure has risen,
A drying apparatus comprising:   The drying apparatus according to claim 1, wherein the pressure adjusting means includes a water ring vacuum pump and a mechanical booster pump.   The drying apparatus according to claim 1 or 2, wherein the first pressure is 150 to 300 Pa, and the second pressure is 350 to 500 Pa. Storing the object to be dried in the processing chamber of the drying apparatus;
Bringing the processing chamber into a reduced pressure state lower than normal pressure with a pressure adjusting means;
Heating the material to be dried when the pressure in the processing chamber drops to a first pressure lower than 600 Pa;
A step of stopping heating of the object to be dried when the pressure in the processing chamber rises to a second pressure lower than 600 Pa and higher than the first pressure;
Including a drying method.   The drying method according to claim 4, wherein the pressure adjusting means is a water ring vacuum pump or a mechanical booster pump.   6. The drying method according to claim 4, wherein the first pressure is 150 to 300 Pa, and the second pressure is 350 to 500 Pa. 7.

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