JPH0675641B2 - Spray drying method and device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spray drying method and apparatus, and more particularly to a spray drying method and apparatus in which a spray drying chamber is formed of a porous film.

[Conventional technology]

The spray-drying method and apparatus basically require three functions of spraying the stock solution, drying the sprayed fine droplets, and separating and collecting the fine powder product. Equipped with a sprayer, a drying chamber and a fine powder collector.

As an example of such a spray-drying apparatus, those shown in FIGS. 6 and 7 are conventionally known. (Japanese Patent Sho 58-
32601 and Japanese Utility Model Laid-Open No. 58-26950) In the spray dryer of FIG. 6, the stock solution sprayed from the nozzle 5 is instantaneously heated by the hot air blown from the inlet 2 in the drying chamber 1. The liquid component is evaporated and the solid component is made into fine powder. Most of the fine powder is taken out as a product through the rotary valve 6, but a part of the fine powder is entrained by the hot air, passes through the exhaust port, and is collected from the rotary valve 8 in the cyclone 7.

The spray dryer shown in FIG. 7 is of a type in which a rotary spray disk 10 is used as a sprayer instead of the nozzle 5.

In the spray dryer of the type shown in FIGS. 6 and 7, the fine product powder is collected separately from the main body of the apparatus and the cyclone as described above, but in this case, it is relatively lightweight and has a small particle size. A cyclone is used, and a relatively large weight and large particle size is taken out from the main body of the apparatus, resulting in minute composition separation of the product.

In the past, this composition separation did not pose a problem depending on the type of product.

By the way, recently, as for the spray drying method and apparatus, a multi-product small-quantity production system for pharmaceuticals, fine ceramics and the like has been demanded from a conventional small-product mass production system.

In addition, the number of cases in which higher-purity products are required as products has increased.

[Problems to be solved by the invention]

As described above, the demand for a high-mix low-volume production method and the production of high-purity products has brought about new problems in addition to the above-mentioned composition separation, which has hardly been a problem in the conventional case.

In other words, due to frequent switching of product types, it has become necessary to quickly and completely wash the adhered solids on the inner wall of the drying chamber. Because
It takes a fatal defect to take a long time for cleaning in order to efficiently perform high-mix low-volume production, and when high purity and high quality are required for product quality, the adhered solid content is completely removed when changing product types. However, in reality, complete cleaning is extremely difficult. In addition, if the product is harmful to the human body, it cannot be directly touched and cleaning is extremely difficult.

In addition, the minute composition separation as described above has also become a problem due to the demand for high-purity products.

[Means for solving problems]

In view of the above-mentioned problems of the prior art, the inventors of the present invention have conducted extensive studies, and as a result, found that the above problems can be solved by forming a spray drying chamber with a porous film, and arrived at the present invention. .

That is, according to the present invention, in a spray drying method in which a stock solution is sprayed into fine droplets to be dried to immediately produce a powder from the stock solution, substantially the entire spray drying chamber is in the form of a single bag or cylinder. Of a heat-resistant and good-peeling porous film, and the dry exhaust gas is immediately separated from the dry exhaust gas and the powder by passing the dry exhaust gas from the inside to the outside of the spray drying chamber formed of the porous film. A spray drying method is provided for obtaining the total amount of powder from a spray drying chamber.

Further, according to the present invention, in a spray drying apparatus for immediately drying a stock solution sprayed into fine droplets to produce a powder from the stock solution, substantially the entire spray drying chamber has a single bag-like or cylindrical shape. Provided is a spray drying apparatus which is formed of a porous film having heat resistance and good peeling property, and which allows a dry exhaust gas to pass from the inside to the outside of a spray drying chamber formed of the porous film.

The porous membrane used in the present invention must be disposed in the spray dryer main body and have excellent heat resistance and peelability.

That is, the temperature of the hot air introduced into the spray drying chamber is usually about 120 to 280 ° C at the inlet temperature and about 150 to 70 ° C at the outlet temperature. However, since it is deposited, it must have good peelability for continuous use. Further, this porous membrane separates the target product fine powder from gas.

The type of the porous membrane having such a function is not particularly limited, but a cloth made of fiber or a combination membrane in which two or more kinds thereof are combined is usually used. As a preferable porous membrane, one having a good releasability network membrane laminated with a woven or non-woven fabric as a strength material is used. In this case, specifically, the mesh membrane is polytetrafluoroethylene (PTFE). ) (Trade name: Teflon) -based film, polytrifluoroethylene-based film, woven fabric, and non-woven fabric are preferably made of polyimide, heat-resistant nylon, polyester, or aramid.

In addition, in the present invention, the entire spray-drying chamber is formed of a single porous membrane, which is easy to remove from the apparatus, and therefore its maintenance is extremely simple.

[Action]

The undiluted solution sprayed in a bag-shaped or cylindrical drying chamber made of a porous film arranged in the spray dryer main body is instantaneously heated and dried by hot air with an inlet gas temperature of 120 to 280 ° C blown from the inlet. Then, it becomes gas and fine powder. Most of the fine powder sinks to the bottom of the drying chamber due to its own weight, while the gas is separated from the remaining fine powder through the ventilation holes of the porous membrane and exhausted to the outside through the exhaust port. Therefore, since all the fine powder is separated from the gas by the porous film, the composition separation of the product fine powder does not occur.

In continuous operation, fine powder adheres to and accumulates on the porous film, pressure loss increases, and the operation must be stopped at last. Therefore, the fine powder must be appropriately blown off. At that time, since the drying chamber is formed of a bag-like or tubular porous film with good peelability, the adhered powder is mechanically vibrated, or air is jetted (pulse air) from the opposite side in a short time. It can be easily brushed off. Also, at that time, in order to completely clean and prevent contamination of impurities, it is performed from the outside without touching the internal product by replacing the porous membrane, but it is a single bag-like replacement. Is easy.

Further, the separation of the fine powder and the gas by the porous membrane is usually to filter only the fine particles therein by passing the gas containing the fine powder through the cloth of the fibers constituting the porous membrane. In practice it is not a simple filtration, and the texture is usually many times larger than the particles to be separated. Therefore, the fine powder partially enters not only the surface of the filter cloth but also the inside thereof and is collected. In the case of the present invention, such a filter cloth is mainly used for a fine powder in which the fine powder is easily dissolved. However, it is desirable to use a combination membrane with the woven or non-woven fabric, which has good releasability for fine powder and has the heat-resistant and strength having the network membrane on the surface which is subjected to surface filtration. The effect of the invention is further increased. Then, the range of the separable particle size of the porous membrane extends over a wide range from 0.1 μm to several mm.

〔Example〕

Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of an apparatus using the spray drying method according to the present invention, (a) is a schematic sectional view of the entire apparatus,
(B) is a partially enlarged cross-sectional explanatory view of a porous film forming a spray drying chamber. In the figure, a spray drying chamber 1 formed of a bag-shaped porous film 15 is arranged inside the spray drying apparatus main body 11 along the inside thereof. This porous film 15 has a first
As shown in the figure (b), the mesh film 13 has a filter cloth as a strength material.
It is made up of 14 pieces. The hot air X is sent downward through the inlet 2 from the upper part of the apparatus main body 11 into the spray drying chamber 1, and is sprayed upward from the lower center of the spray drying chamber 1 through the nozzle 5. Contacted countercurrently.
The product fine powder enters the product receiver (not shown) from the outlet 6 by the seal valve, and the gas is separated from the fine powder A through the porous film 15 forming the outer wall of the spray drying chamber, and exhausted from the lower part of the main body 11. Each is discharged to the outside from the mouth 3.

FIG. 2 is a schematic cross-sectional view showing another embodiment of the present invention, in which a rotating atomizing disk 10 is used instead of the nozzle 5 as the atomizer, and the hot air X causes the undiluted solution from the atomizing disk 10 to flow downward in parallel. 1 is different from the structure shown in FIG. 1 except that the structure is substantially the same.

3 to 5 are also schematic cross-sectional views showing other embodiments of the present invention. FIG. 3 shows that hot air X and the stock solution from the nozzle 5 are introduced in a downward parallel flow. 4 is hot air X
And the undiluted solution from the nozzle 5 is introduced in a parallel direction in the upward direction, and FIGS. 5A and 5B show the undiluted solution from the hot air X and the nozzle 5 introduced from the lateral direction.

The apparatus shown in FIGS. 3 to 5 is provided with an expulsion mechanism (backwash type, pulse air type) Z for expulsion of fine powder. The fine powder A fed into the apparatus main body 11 from the direction and adhering to the porous film 15 is wiped off.

Hereinafter, the spray drying method and apparatus of the present invention will be described more specifically.

(Example 1) Using a spray dryer of the type shown in FIG. 1, stabilized zirconia (Ca _0.15 Zr _0.85 O _1.85 ) and lanthanum-added barium titanate [BaTiO ₃ +0.01 (La ₂ O ₃ )] Two types of stock solution concentration 60% (in the case of stabilized zirconia), 70
% (For barium titanate with lanthanum), throughput 15
It was sprayed at a rate of 0 kg / Hr. The drying chamber has a diameter of 2500 mm, a straight body length of 2500 mm, a total height of 4300 mm, the upper part is cylindrical, and the lower part is funnel-shaped.The porous film forming the drying chamber is made of heat-resistant nylon nonwoven fabric laminated with polytetrafluoroethylene. A combination membrane was used. The hot air inlet temperature was 220 ° C, and the exhaust air temperature was 120 ° C.

The stock solution was spray-dried under the above conditions. As a result, the properties of the product fine powder were as follows.

(1) (2) Product particle size (average) 60 μm 70 μm Product moisture 0.3% 0.7% No composition variation None None Yield after 4 hours operation 99% 99% Note that (1) is stabilized zirconia and (2) is lanthanum. The added barium titanate is shown.

When switching products, the time required for switching is approximately 40
It took only a minute.

〔The invention's effect〕

As described above, the spray drying apparatus of the present invention forms substantially the entire spray drying chamber with a single porous membrane, and passes the dry exhaust gas from the inside to the outside of the spray drying chamber formed with the porous membrane. Since fine powder with a small particle size is not entrained in the gas and discharged to the outside of the main unit as in the past, composition separation does not occur, and frequent product type switching due to the multiple product type small volume production method. Also in this case, it is possible to quickly and easily wash and remove the adhered fine powder, and as a result, it is possible to improve the quality and the purity of the fine product powder.

Further, there is an effect that a dust collecting device which has conventionally been separately installed is unnecessary.

[Brief description of drawings]

FIG. 1 shows an embodiment of a spray drying apparatus according to the present invention, in which (a) is a schematic sectional view of the entire apparatus, (b) is a partially enlarged sectional explanatory view of a porous membrane, and FIGS. FIG. 5 is a schematic sectional view showing another embodiment of the present invention, and FIGS. 6 to 7 are schematic sectional views showing a conventional spray dryer. 1 ... Spray drying chamber, 2 ... Hot air inlet, 3 ... Exhaust outlet, 5
…… Nozzle, 6 …… Product outlet, 7 …… Cyclone, 10…
… Spraying disk, 11 …… main body, 13 …… mesh film, 14 ……
Filter cloth, 15 ... Porous membrane.

Front page continuation (72) Inventor Masaaki Okawara 3847 Ikebe-cho, Midori-ku, Yokohama-shi, Kanagawa Okawara Kako Machinery Co., Ltd. (72) Inventor Katsumi Kobayashi 3847 Ikebe-cho, Midori-ku, Yokohama-shi Kanagawa Okawara Kakoki (72) Inventor Takashi Ito 3847 Ikebe-cho, Midori-ku, Yokohama-shi, Kanagawa Okawara Kakoki Co., Ltd. (56) References Japanese Patent Publication No. 57-43212 (JP, B2) Actual Publication No. 52-28862 (JP, Y2)

Claims (4)

[Claims] 1. A spray-drying method for producing a powder from an undiluted solution by immediately drying the undiluted solution sprayed into fine droplets,
Substantially the entire spray-drying chamber is formed of a single bag-shaped or tubular heat-resistant and good-peeling porous film, and the dry exhaust gas is passed from the inside to the outside of the spray-drying chamber formed of the porous film. By passing it, dry exhaust gas and powder are immediately separated,
A spray drying method, characterized in that the total amount of powder is obtained from the spray drying chamber. 2. The spray drying method according to claim 1, wherein the porous membrane is a combination membrane of a mesh surface filtration membrane having good releasability from powder and a heat resistant filter cloth as a strength material. . 3. A spray-drying device for producing a powder from an undiluted solution by immediately drying the undiluted solution sprayed into fine droplets,
Substantially the entire spray-drying chamber is formed of a single bag-shaped or tubular heat-resistant and good-releasing porous film, and the dry exhaust gas flows from the inside to the outside of the spray-drying chamber formed by the porous film. A spray-drying device characterized in that it passes through. 4. A spray drying apparatus according to claim 3, wherein the porous membrane is a combination membrane of a mesh surface filtration membrane having good releasability from powder and a heat resistant filter cloth as a strength material. .