JPH03131302A - Porous filter for spray drying - Google Patents

Abstract

PURPOSE:To eliminate the generation of a dust leak and to stabilize spray drying by using a porous filter whose air permeability is 0.5-15cc/cm<2>/sec as the filter constituting the drying chamber of a spray drying apparatus. CONSTITUTION:The side surface part 3 of a porous filter is formed into a cylindrical shape and the bottom part thereof is formed into a funnel like shape and the lower end part thereof is connected and fixed to the powder taking-out port of a spray drying apparatus. Hooks 6 are provided to the connection part of the shoulder part, that is, the ceiling part 1 of the porous filter and the side surface part thereof to suspend the porous filter 1 from the upper fixing part of the spray drying apparatus. The air permeability of the porous filter is set to 0.5-15cc/cm<2>/sec and the mesh size of the filter is set to 1-100mum. Since the drying chamber of the spray drying apparatus is constituted of this porous filter, stable spray drying can be performed and the leakage of dust from the filter is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a porous filter used in a drying chamber of a spray drying apparatus. More specifically, the present invention relates to an air-permeable porous filter that constitutes a drying chamber of a spray drying apparatus, separates produced powder from gas, and recovers the powder.

[Prior art] Spray drying basically requires three functions: ■ Spraying the stock solution, ■ Drying the minute droplets generated by spraying, and ■ Separating and collecting powdered products. In response to demands for a high-mix, low-volume production system and the manufacture of high-purity products, the applicant previously proposed in JP-A-62-152501 that spraying, drying, and separation and collection are performed in the same drying area, and at the same time, changing the product type. We proposed a method and device that allows the drying chamber to be freely replaced depending on the situation.

[Problems to be Solved by the Invention] The method and device proposed above configure the spray drying chamber with a porous membrane to perform spraying, drying, and separation and recovery in the same drying area, and at the same time, it is possible to replace the drying chamber. It is something that can be done easily and is highly practical.

As the inventor conducted further experiments on this spray drying method and apparatus, it was discovered that depending on the operating conditions such as the amount of hot air blown, the pressure difference between the inside and outside of the drying chamber, and the particle size of the powder or granular material, the porous structure constituting the drying chamber We were faced with a situation where dust leaked from the membrane, that is, a porous filter, and pressure loss increased, making steady operation impossible. Therefore, as a result of various studies to investigate the cause and solve the problem, the inventor of the present invention has found that it is necessary to appropriately select the air permeability or opening of the porous filter that constitutes the drying chamber, and furthermore, the porous filter during operation. The inventors have discovered that the above problem can be solved by setting the shape of the drying chamber (that is, the shape of the drying chamber) to a predetermined value, and have arrived at the present invention.

[Means for Solving the Problems] That is, according to the present invention, there is provided a filter constituting a drying chamber of a spray drying device, which has an air permeability of 0.5 to 15 c.
Provided are a porous filter for spray drying that has a drying capacity of c/cm2/sec, and a porous filter for spray drying that constitutes a drying chamber of a spray drying device and has an opening of 1 to 100 μm. .

In addition, in the present invention, in the ventilation state during operation, the shape of the porous filter is changed such that when a rotating disk type spray device is used, the ceiling part is flat or inverted funnel shape, and when spraying is performed using a pressure nozzle or a two-fluid nozzle. The ceiling part is funnel-shaped, the side parts are cylindrical, and the bottom part is funnel-shaped, and the funnel-shaped bottom part is formed at an inclination angle of 30 to 150 degrees. If formed in this way, there is no need to support the funnel-shaped bottom from below, which is preferable. This shape also allows the ceiling of the porous filter to be connected to the head of the spray dryer (here, the spray nozzle,
A spraying means such as a spray disk is installed. ) and by connecting and fixing the bottom of the porous filter to the powder outlet, it is always maintained stably.

Furthermore, if the entire drying chamber is configured so that the seams of the porous filter are vertical, the accumulation of powder and granules generated near the seams will not occur, unlike when the seams are formed horizontally, and the porous filter It is preferable because it is difficult to adhere to the surface. In addition, in the ceiling part, it is not necessary to limit the direction of the seams because the powder particles tend to fall.

[Function] The porous filter of the present invention is characterized by having an air permeability or opening within a specific range.

The operating conditions of the spray drying device vary depending on the amount of processing (i.e., large or small device), the type of stock solution to be spray dried, etc., but the inventor has conducted various experiments and studies. By configuring the spray drying chamber with a porous filter having a specific range of air permeability or opening over a wide range of operating conditions, no dust leakage occurs.
It has been found that stable spray drying can be performed.

In the present invention, the air permeability of the porous filter is 0,
5 to 15 cc/cm”/see, preferably 1.0 to
8 cc/cm"/see. This air permeability range is within a range that does not form strong adhesion or deposits on the porous filter, and the operation of the spray drying equipment is stable. In particular, the air permeability should be kept low and stable. This prevents dust from adhering to the porous filter and prevents dust from leaking.

If the air permeability is less than 0.5 cc/cm2/sec, the difference in pressure between the inside and outside becomes too large during spray drying operation, making stable operation impossible.

On the other hand, if the air permeability exceeds 15 cc/cm2/sec,
Dust leaks from the porous filter.

Furthermore, regarding the opening of the porous filter of the present invention,
Basically, it is related to the shape and size of the powder, but as a result of various studies, we found that the opening of the porous filter is 1 to 1.
1100B, preferably 2 to 50 pm, prevents dust leakage. The opening of the porous filter is 1
When the opening is less than 7 hm, the difference between the inside and outside pressure becomes too large and stable spray drying operation cannot be performed. On the other hand, when the opening exceeds 100 μm, dust leakage occurs.

Note that the air permeability and mesh opening described above were measured as follows.

The air permeability of the porous filter was measured based on method A of JIS L1096. That is, using a Frazier type tester, after attaching a test piece to one end of a cylinder, a rheostat was used to adjust the tilt type barometer to a height of 1.27 cm (124 cm) in the water column.
Adjust the suction fan so that it shows a pressure of 5 Pa), and from the pressure indicated by the vertical barometer and the type of air hole used, calculate the amount of air passing through the test piece ( cc/cm2/5ec) was determined, and this was taken as the air permeability.

The opening of the porous filter was determined by measurement under a microscope. In the present invention, the maximum spherical particle diameter that can pass through the gaps of the filter medium is defined as the opening. In other words, the maximum value of the short axis portion of the eye opening that could be observed was adopted.

The porous filter used in the present invention is preferably heat resistant and has excellent removability. That is, the temperature of the hot air introduced into the spray drying chamber is usually 200 to 280.
It is as high as ℃, and the temperature that passes through the filter is 5℃.
Since the temperature is 0 to 150℃, it must be able to withstand this temperature, and powder and granules always adhere and accumulate, so
For continuous use, it is desirable to have good releasability. This porous filter is attached removably and can be replaced at any time. This porous filter separates the target product powder from the gas, that is, collects the powder.

As a porous filter that performs such a function, the type thereof is not particularly limited, but fibrous cloths such as woven cloth and nonwoven cloth, and combination membranes in which a porous film is bonded to the surface of these cloths are used.

As the material of the porous filter, heat-resistant nylon, polyester, polyimide, polyamide, polyphenyl sulfide, etc. are used. Moreover, polytetrafluoroethylene (PTFE), polytrifluoroethylene, etc. are used as the porous film. Next, the porous filter of the present invention will be explained based on the drawings.

FIG. 1 is an explanatory diagram showing an example of the shape of the porous filter of the present invention during operation. In this example, the ceiling part l is flat and has a connection for connecting and fixing it to the head part of a spray drying device (not shown). It has part 2.

The side surface 3 of the porous filter has a cylindrical shape, and the bottom 4 has a funnel shape, and the bottom 4 is connected and fixed to a lower end 5 of the powder outlet of a spray drying device (not shown). A hook 6 is provided at the shoulder of the porous filter, that is, at the connection between the ceiling 1 and the side surface 3, and is hung from the upper fixing part of the spray drying device.

Furthermore, the seams 7 of the porous filter constituting the entire drying chamber were formed in a vertical direction to suppress adhesion of the powder to the porous filter.

Incidentally, the inclination angle α of the funnel-shaped bottom portion 4 is 30 to 1506,
Preferably, when formed to have a length of 50 to 120', the above shape can be stably maintained without requiring support means from below.

The shape of the porous filter, such as a two-legged one, usually makes the internal pressure of the porous filter 1011111 relative to the external pressure.
It is maintained by setting it to H20 or higher.

[Examples] The present invention will be explained in more detail based on Examples below.
The present invention is not limited to these examples.

(Example) A drying chamber was constructed with a porous filter using various fibers,
Spray drying was performed under the following conditions, and the filter characteristics and the presence or absence of dust leakage from the filter were examined.

(Spray drying conditions) ■Average particle diameter of spray-dried powder --- 10 to 200 μm ■Hot air inlet temperature...200 to 250'C ■Blow rate
=1000-1500 m'/hr The results are shown in Table 1.

As is clear from Table 1, when a porous filter having an air permeability or opening within a specific range is used, dust leakage can be prevented within a range where the pressure loss does not become too large.

0 Table 1 (Notes) Material of porous filter A...Heat-resistant nylon fiber, B...Heat-resistant nylon fiber, C...Heat-resistant polyamide fiber, D...Polyphenyl sulfide fiber, E... Composite membrane of polytetrafluoroethylene (PTFE) (porous film) and heat-resistant nylon fiber, F...heat-resistant nylon fiber, G...polyphenylsulfide fiber, H...heat-resistant polyamide fiber (Note 2) Dust leakage Presence or absence○...No dust leakage, ×...Dust leakage (Note 3)
Evaluation ■: Particularly good, O: Good 1 [Effects of the invention] As explained above, according to the present invention, the drying chamber of the spray drying apparatus is With this structure, it is possible to perform stable spray drying and recover powder particles without causing dust leakage from the porous filter, regardless of the spray drying operating conditions.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the shape of the porous filter of the present invention during operation. 1... Ceiling part of the porous filter, 2... Connection part,
3... Side part of the porous filter, 4... Bottom part of the porous filter, 5... Lower end part, 6... Hook, 7
···stitch.

Claims (4)

[Claims] (1) A filter constituting the drying chamber of a spray dryer, whose air permeability is 0.5 to 15 cc/cm^2/se
A porous filter for spray drying, characterized in that c. (2) A porous filter for spray drying, which is a filter constituting a drying chamber of a spray drying apparatus, and is characterized in that the opening thereof is 1 to 100 μm. (3) The ceiling is flat, inverted funnel-shaped, or funnel-shaped;
3. The porous filter for spray drying according to claim 1, wherein the side part has a cylindrical shape, the bottom part has a funnel shape, and the funnel-shaped bottom part has an inclination angle of 30 to 150 degrees. (4) The porous filter for spray drying according to claim 3, wherein the seams of the porous filter are formed in a vertical direction.