JPH02290488A - Method and apparatus for drying granule - Google Patents

Abstract

PURPOSE:To enable improvement of the degree of drying in a short time by a method wherein a granular substance is subjected to primary drying by dried hot air and thereafter it is dried under a reduced pressure in a hot air flowing state and subjected to secondary drying. CONSTITUTION:The outside air sucked into a hot air drying element 30 is passed first through an air refrigerator 31 to be dehumidified preliminarily. Thereafter it is dehumidified in a high degree by a dehumidifier 32, sent to a heater 34 to be turned into hot air, and jetted into a hopper 20 through a hot air jet nozzle 35, whereby a granule F is subjected to primary drying. In an airing reduced-pressure drying element 40, subsequently, a vacuum pump 41 is operated to put the inside of the drying hopper 20 in a vacuum and the substance is subjected to secondary drying therein. Since water evaporated in the drying hopper 20 is exhausted outside without remaining therein, according to this constitution, the efficiency of drying of the granule F turns excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for drying a powder or granular material, such as a pellet made of synthetic resin, using hot air.

[Prior Art] Conventionally, as methods for drying powder or granules, there are methods in which the powder or granules are simply dried with hot air, and methods in which the powder or granules are simply heated and dried in a vacuum.

The hot air drying of the powder in the former method is normal pressure drying, and the vacuum drying in the latter method is performed by storing the powder in a vacuum tank, and this vacuum tank contains the removed moisture. It does not have an effective means of draining water to the outside.

[Problem to be solved by the invention]

By the way, in the former conventional method, the powder and granules are simply dried with hot air, so although it can be dried relatively quickly up to a certain degree of dryness, as mentioned above, this hot air drying is not always possible. Pressure drying takes time and is inefficient to obtain a high degree of dryness.

In addition, in the latter method, the powder and granules are simply heated and dried in a vacuum state, and the vacuum tank is not equipped with an effective means for discharging the removed moisture to the outside. The water content in the granular material cannot be sufficiently discharged from the vacuum tank, which means that it takes a long time to obtain a product with a high degree of dryness.

The present invention was made against the background of such conventional technology, and an object of the present invention is to provide a method and apparatus for drying powder and granular material that can obtain a high degree of dryness in a relatively short time.

[Means to solve the problem]

The present invention firstly dries the granular material with dry hot air,
The present invention provides a method for drying powder and granules, which is characterized in that the primary dried powder and granules are then dried under reduced pressure while blowing hot air for secondary drying. A drying device for powder and granular material, comprising a hot air drying section for primary drying, and an aeration vacuum drying section for secondary drying by drying the primarily dried powder and granular material under reduced pressure in a hot air aeration state. It also provides.

[Function] In the method of drying powder or granular material of the present invention, first, the powder or granular material is primarily dried with dry hot air. This allows it to adhere to the powder and/or
Or remove most of the moisture contained.

Thereafter, this primary dried powder and granular material is dried under reduced pressure while blowing hot air to perform secondary drying. As a result, the residual moisture in the powder is discharged to the outside according to the flow of hot air under reduced pressure in a ventilated state, so that the residual moisture in the powder can be efficiently removed.

In addition, in the powder drying apparatus of the present invention, first, in the hot air drying section, dry hot air is blown onto the powder and granules to perform primary drying, thereby removing most of the particles that have adhered to and/or contained in the powder or granules. Remove moisture.

Thereafter, this primary dried powder and granular material is dried under reduced pressure with hot air in an aerated vacuum drying section for secondary drying to remove residual moisture from the powder and granular material.

By doing so, powder with a high degree of dryness can be obtained in a relatively short time.

[Example] Hereinafter, the method and apparatus for drying powder of the present invention will be specifically explained based on the drawings, but the present invention is not limited to this example.

In describing the examples, a powder drying method and apparatus for drying synthetic resin pellets will be taken as an example.

First, a powder drying apparatus used in the powder drying method of the present invention will be explained.

As shown in FIG. 1, the powder drying apparatus of the present invention includes a raw material supply section 10, a drying hopper 20, a hot air drying section 30, and an aeration vacuum drying section 40.

This raw material supply unit 10 is a supply unit for supplying powder or granular material F as a raw material into the drying hopper 20, and includes a raw material storage tank 11,
It has a hopper loader 12 that temporarily stores the powder and granular material F in the raw material storage tank 11 before it is introduced into the drying hopper 20, and a raw material supply suction machine 13 that sucks and supplies the powder and granular material F to the hopper loader 12. , each connected by a line.

The powder F in this example includes, for example, polypropylene resin to which talc and/or mica, charcoal, etc. are added, polyamide resin, modified polyphenylene ether, polybutylene terephthalate, polyethylene terephthalate, polyethylene ether ketone, Pellets made of synthetic resin such as polyether kedone are used, but it is not necessarily limited to this. For example, pellets made of synthetic resin such as silica alumina and zirconia, which do not like high humidity and drying, are used in the fine ceramics field, food field, etc. Powder or granules can also be used.

The drying hopper 20 is a hopper for drying the granular material F input from the hopper loader 12, and a receiving hopper 21 for receiving the dried granular material F is arranged on the discharge side of the granular material F of this drying hopper 20. has been done.

The hot air drying section 30 is a primary drying section that supplies dry hot air into the drying hopper 20 to dry the powder F stored in the drying hopper 20, and is used for preliminary dehumidification of the external air taken in. air refrigerator 31 for this purpose, and this air refrigerator 3
A dehumidifier 32 that highly dehumidifies the external air pre-dehumidified in step 1.
, a circulation blower 33 that blows the outside air dehumidified by this dehumidifier 32 to the drying hopper 20 side, and this circulation blower 3
a heater 34 that heats the dehumidified external air blown by the heater 3; and a hot air jet nozzle 35 that is housed in the drying hopper 20 and that jets the external air heated by the heater 34 into the drying hopper 20. This drying hopper 2
A cyclone 36 that separates the hot air (external air) exhausted from 0 and the fine powder F mixed in this external air.
These components are connected to each other through lines so that they can take in and exhaust outside air.

A portion of the hot air (external air) separated and exhausted from the cyclone 36 is sucked into the circulation blower 33, while the remainder is exhausted to the outside.

In addition, this hot air exhausted to the outside is returned to the air refrigerator 31.
It can be pulled back and reused.

The aeration vacuum drying section 40 is a secondary drying section that dries the granules that have been primarily dried in the hot air drying section 30 under reduced pressure in a hot air aeration state, and is connected to the drying hopper 20 .
a vacuum pump 41 that reduces the pressure inside the drying hopper 20, and a twenty dollar valve 42 that makes the inside of the drying hopper 20 a hot air ventilation state while maintaining a predetermined reduced pressure state inside the drying hopper 20 by restricting the amount of external air blown. have.

Note that the 21 dollar valve 42 in this embodiment is arranged in a line between the dehumidifier 32 and the heater 34 in parallel with the circulation blower 33; The installation location is not limited as long as it is between lines.

In addition, in the figure, 101 is a valve for opening/closing air introduction for stopping the raw material supply, which is placed between the line between the hopper loader 12 and the raw material supply suction device 13, and 102 is a powder valve, which is placed between the hopper loader 12, the drying hopper 20, and the line. Valve 201 for charging granules F, drying hopper 20 and receiving hopper 21
A valve 301 is a valve for receiving and discharging dried powder F to the hopper 21, which is placed between the line between the dehumidifier 32 and the circulation blower 33, and a valve 301 is a valve for blowing external air, which is placed between the line between the dehumidifier 32 and the circulation blower 33. 302 is a valve for external air blowing disposed between the line between the circulation blower 33 and the heater 34;
304 is a valve for discharging hot air (external air) disposed between the line between the drying hopper 20 and the cyclone 36, and 304 is an exhaust circulation valve for discharging hot air (external air) disposed between the line between the cyclone 36 and the circulation blower 33. 305 is a valve for externally discharging collected powder deposited at the bottom of the cyclone; 401 is a drying hopper 20 and a vacuum pump 4;
A valve 402 is placed between the line between the heater 34 and the twenty-one dollar valve 42 to open the ventilation decompression line.

Next, a method for drying powder or granular material according to an embodiment of the present invention using this powder or granular material drying apparatus will be explained.

As shown in FIG. 1, the drying method of the powder or granular material according to the embodiment of the present invention is as follows: First, in the hot air drying section 30, dry hot air (external air) is blown onto the powder or granular material F for primary drying. This removes most of the moisture attached to and/or contained in the powder.

Specifically, the raw material supply suction machine 13, the air refrigerator 31, the dehumidifier 32, the circulation blower 33, and the heater 34 are operated in advance, and the valves 101, 201, 305, 401,
402 while valves 102, 301, 302 are closed.
, 303 and 304 are opened.

By the operation of this raw material supply suction device 13, the raw paddy storage tank 11
The powder F in the hopper loader 12 is supplied to the hopper loader 12, and then the powder F in the hopper loader 12 is transferred to the dry hopper 20.
It is thrown inside.

Note that this valve 102 is closed when the drying hopper 20 becomes full.

In parallel with this, the hot air drying section 30 is operated by the circulating blower 34.
The external air sucked into the interior first passes through an air refrigerator 31 to be preliminarily dehumidified, then is highly dehumidified by a dehumidifier 32, and is blown to a heater 34 where it is hot-aired.

Next, the hot-aired external air that has passed through the heater 34 is ejected through the hot air jetting nozzle 35 into the drying hopper 20 into which the granular material F has been introduced.
is first dried.

Next, the hot air (external air) after the primary drying of the granular material F is used to separate and remove the fine powder of the granular material F in the cyclone 36, and a part is reused by the circulation blower 33. ,
The remainder is exhausted to the outside.

Note that this hot air exhausted to the outside is returned to the air refrigerator 31.
It may be reused by blowing air to it.

Next, this primary dried granular material F is subjected to secondary drying by drying under reduced pressure in a hot air aeration state in the aeration reduced pressure drying section 40 to remove residual moisture from the granular material F.

Specifically, first, the valves 102, 201, 301, 30
2, 303, 304, 305, 402 while closing
The valve 401 is opened, the circulation blower 33 is deactivated, and the vacuum bomb 41 is activated to evacuate the interior of the drying hopper 20.

After that, the valve 402 is opened, the amount of the dehumidified external air is throttled by the 21 dollar valve 42, and the outside air that has been throttled by the 21 dollar valve 42 is heated by the heater 34 to be hot-aired. Hot air is blown into the reduced pressure drying hopper 20 through the hot air jet nozzle 35 for secondary drying. This vacuum drying with hot air ventilation is performed at a temperature of 110 to 210 T, for example.
It is carried out under reduced pressure of o r r. Note that the external air sucked by this vacuum pump 41 is exhausted to the outside.

In this way, by drying the primary dried powder and granular material F under reduced pressure while blowing hot air, not only can the powder and granular material F be dried under reduced pressure, but also the drying hopper 20 Since the moisture evaporated inside is discharged to the outside without remaining, the drying efficiency of the powder F is improved compared to simple hot air drying or vacuum drying.

By doing so, powder with a high degree of dryness can be obtained in a relatively short time.

For example, 400 kg of polypropylene resin powder F to which talc and mica are added has an initial water content of 600 ppm.
When dried for 1 hour using the powder drying device of this example, approximately 2
Even during the rainy season, powder F with an initial moisture content of 1.500 ppm can be dried to about 500 ppm.

Then again, while closing valves 401 and 402,
A predetermined valve is opened to bring the inside of this drying hopper 20 to normal pressure, and then a valve 201 is opened to bring the inside of this drying hopper 20 to normal pressure.
The granular material F that has been dried inside is received and discharged into the hopper 21.

In this example, in order to further improve the drying efficiency, the primary drying and secondary drying are performed for several cycles, and the powder F after drying is also divided into quarters, for example. Although the drying process is carried out in parts as shown in FIG. 1, the drying process is not limited to this, and it is also possible to carry out this drying in one cycle and also discharge the powder F after drying all at once.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, but is included in the present invention even if the structure and operation are changed without departing from the gist.

For example, there is no need to limit the specific method of drying the powder or granular material to the method of the example, and any method may be used as long as hot air drying and aerated vacuum drying are performed.

Further, the specific drying device for powder and granular materials is not limited to the one in this example, and may be constructed of any type of device as long as it is equipped with a hot air drying section and an aeration vacuum drying section. good.

Furthermore, in describing this example, we took as an example a drying method and apparatus for drying a powder or granule for drying synthetic resin pellets, but the method is not limited to this, but any powder or granule can be dried. It can also be adopted as a method and apparatus.

(Effects of the Invention) Since the present invention is a method of drying a powder or granular material and an apparatus thereof, it is possible to produce a powder or granular material with a high degree of dryness in a relatively short time.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a powder drying apparatus according to an embodiment of the present invention. F: Powder 30; Hot air drying section 40; Ventilation and vacuum drying section Patent applicant: Mitsubishi Kakoki Co., Ltd. Agent: AALPI TOPLA Co., Ltd. Patent attorney: Shige Takashi Shirai

Claims (2)

[Claims] (1) First, the powder or granule material is firstly dried with dry hot air, and then this first dried powder or granule material is dried under reduced pressure in a hot air ventilation state for second drying. Drying method. (2) Equipped with a hot air drying section that primarily dries the granular material with dry hot air, and an aeration vacuum drying section that performs secondary drying by drying the primarily dried granular material under reduced pressure in a hot air aeration state. A drying device for powder and granular materials characterized by the following.