Concentrating evaporators – Spray type – Gaseous current
Patent
1989-01-25
1991-05-14
Manoharan, Virginia
Concentrating evaporators
Spray type
Gaseous current
34 10, 34 57R, 159 481, 159DIG28, 159DIG41, 202236, 203 90, B01D 118, F26B 306
Patent
active
050153323
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a spray dryer, particularly to a spray dryer for reducing the pollution of a spray drying chamber by powder and preventing the compositional variation of the powder product.
BACKGROUND
Spray dryers basically have three essential functions of (1) spraying feed liquid, (2) drying resulting microdrops and (3) separating and recovering a resulting fine powder product, and ordinarily have an atomizer, a drying chamber and a fine powder recovering unit, respectively, corresponding to the above functions.
As examples of these spray dryers, there have hitherto been known those shown in FIGS. 9 and 10 (see Japanese Patent Publication No. 32601/1983 and Japanese Utility Model Laid-Open No. 26950/1983).
In the spray dryer of FIG. 9, a feed liquid is sprayed into a drying chamber 1 from a nozzle 5 and is momentarily heated by hot air from an inlet 2, whereby the liquid component of the feed liquid is evaporated and the solid component is made into a fine powder. The majority of the fine powder is taken out as a product via a rotary valve 6. Part of the fine powder accompanies hot air, passes a waste gas outlet 3 and enters a cyclone 7, and is recovered from a rotary valve 8.
The spray dryer of FIG. 10 is a type using, as an atomizer, a rotary spraying disc (a rotary disc) 10 in place of the nozzle 5.
In the spray dryers as shown in FIGS. 9 and 10, a fine powder product is recovered separately in the main section of the dryer and in the cyclone. In this case, a powder of lighter particles having smaller particle diameters is recovered in the cyclone and a powder of heavier particles having larger particle diameters is taken out from the main section; accordingly, slight compositional variations in the product occurs.
In the past, this compositional variation posed little problem depending upon the type of product.
It has been required recently that spray dryers can perform, instead of conventional few grade, large quantity type production, many grade, small quantity type production especially for medicines, fine ceramics, etc.
Also, it is increasingly required that spray dryers produce a product of higher purity.
Under these new situations requiring a spray dryer capable of providing many grade, small quantity type production and a powder of the higher purity, the abovementioned compositional variation of product which posed little problem in the past has entered a new phase. Moreover a new problem has arisen.
That is, with the increase in the frequency of product switch-over, the rapid and complete washing of the deposit adhering to the inner wall of the drying chamber has become necessary. It is necessary because if washing takes a long time it is detrimental to the efficient execution of many grade, small quantity type production and also because the complete washing of the deposit adhering to the inner wall of the drying chamber, which is required in the product switchover when a product of higher purity and higher quality is needed, is very difficult. Moreover, when a product harmful to humans is produced, washing is extremely difficult because the operator is prohibited from making direct contact with the product.
Further, the requirement for a product of higher purity has turned the above-mentioned slight compositional variation among products into a problem.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems of the prior art, the present inventors conducted experimentation and, as a result, reached the present invention.
According to the present invention a spray dryer is provided for momentarily drying microdrops by spraying the microdrops into a spray drying chamber together with hot air, the spray dryer being characterized in that the spray drying chamber is formed by a head section and a heatresistant porous membrane and that the heat-resistant porous membrane is made detachable and the head section is made displaceable vertically.
The heat-resistant porous membrane forming the outer wall of the spray drying chamber is swollen into
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Ito Takashi
Iwaya Shoichi
Kobayashi Katsumi
Masumura Hitoshi
Ohkawara Masaaki
Manoharan Virginia
Ohkawara Kakohki Co., Ltd.
TDK Corporation
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