JPS63267401A - Method and equipment for spray drying - Google Patents

Abstract

PURPOSE:To obtain powdery paint in which the residual amount of a solvent is minute by using a spray drier formed with a cool air zone to the outside of a hot zone for drying raw liquid in the case of producing powder paint. CONSTITUTION:Raw liquid A is blown into an equipment main body 1 from an atomizer 12 of raw liquid via a pump and also heated gaseous N2 is blown thereinto from its circumference through a filter 14 and a heater 15 of N2 and the raw liquid A is instantaneously dried to fine particles. Simultaneously gaseous N2 used for secondary cool air is blown into the circumferential direction through a nozzle 13 of the side part of the equipment main body 1 via a blower 16. The fine particles incorporating solvent content not more than 1wt.% are taken out from the lower part of the equipment and introduced into a cyclone 7 through a pipeline 17 to separate gas and recovered through a rotary valve 8. in this case, when cooling the wall surface with a cool air jacket 20 provided to the outside of the wall surface of the main body 1, the fine particles can be completely prevented from adhering on the wall surface. The gas separated in the cyclone 7 is reused for secondary cool air via a filter 18, a circulating blower 9 and a condenser 19.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a spray drying method and apparatus, and particularly to a spray drying method and apparatus that can reduce the amount of residual solvent to a very small amount, for example, 1% by weight or less.

(Prior art) Spray drying methods and equipment basically consist of: ■ Spraying an undiluted solution;
There are three essential functions: drying of sprayed minute droplets, and separation and collection of fine powder products, and spray drying equipment is usually equipped with a sprayer, drying chamber, and fine powder collector for each. has been done.

As an example of such a spray drying apparatus, those shown in FIGS. 3 and 4 are conventionally known. (Tokuko 1987
In the spray drying apparatus shown in FIG. 3, the stock solution sprayed from the nozzle 5 passes through the heater 4 to the inlet 2.
The liquid component is evaporated and the solid component is turned into fine powder by being instantaneously heated by hot air blown from the container. Most of the fine powder is taken out as a product via the rotary valve 6, but a portion of the fine powder is entrained by hot air, passes through the exhaust port 3, and is recovered from the rotary valve 8 in the cyclone 7.

The spray drying device shown in FIG. 4 is of a type that uses a rotating spray disk 10 instead of the nozzle 5 as a stock solution atomization device.

(Problems to be Solved by the Invention) However, when a product such as a powder coating is manufactured using a spray drying apparatus of the type shown in FIGS. 3 and 4, the resulting fine powder The amount of residual solvent is 5~
The amount was about 6% by weight, and it was not possible to produce a product in a minute amount that would be satisfactory, for example, less than 1% by weight.

(Means for Solving the Problems) Therefore, the present inventors took into consideration the problems of the prior art described above.
As a result of extensive research, we have discovered a means to minimize the amount of residual solvent in the resulting fine powder, and have arrived at the present invention.

That is, according to the present invention, in a spray drying method in which a stock solution is sprayed onto micro droplets and dried to produce a fine powder, the micro droplets are instantaneously dried and the resulting powder and dry gas are used. A spray drying method characterized in that a cold gas is introduced around a hot zone to form a cold air zone, and a mixed gas of drying gas and cold gas is discharged at a temperature below the melting point of the powder, and a raw solution. in a spray drying device that sprays micro droplets and dries them to produce a fine powder.

It is characterized by having a stock solution atomization device installed on the top of the device body for spraying the stock solution and drying the stock solution with dry gas, and a cold gas blowing means for blowing cold gas into the side of the device body. A spray drying apparatus is provided.

〔Example〕

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a partially cutaway explanatory view showing an embodiment of the spray drying apparatus of the present invention.

In the figure, the main body 1 of the spray drying apparatus includes a liquid atomizer 2112 provided at the top of the main body 1 for spraying the liquid A by a pump from a tank 11 containing the liquid A, and a circumference on the side of the main body 1. It basically consists of nozzles 13 installed at regular intervals in the direction for blowing N2 gas, which is an inert gas, in the tangential direction of the side part.

In the above configuration, the operation will be explained as follows: stock solution A,
For example, a polymer paint solution using methyl ethyl ketone (MEK) as a solvent is blown into the main body of the device from the stock solution atomization device 12 via a pump, and the blown stock solution A passes through a filter 14 and an N2 heater 15 to remove dust. Then, N2 gas heated to 100 to 200° C. is blown in, and the stock solution A is instantaneously dried into powder. At the same time, N2 gas at a temperature of about 10° C. is blown in the circumferential direction from the nozzle 13 on the side of the device main body l through the secondary cold air blower 16.

In this way, a hot zone with a temperature of 0.7 to 2 times the melting point of the powder is formed in the center of the apparatus main body l, and a hot zone surrounding the hot zone is formed in the outer periphery. A cold air zone is formed, and residual solvent in the powder obtained by conventional drying using only hot gas is removed.
However, by providing a cold air zone outside the hot zone, it is possible to use hot gas at a higher temperature and to reduce the flow of powder into the equipment. By preventing melt adhesion and making the temperature of the exhaust gas lower than the melting point of the powder, the amount of residual solvent in the powder can be reduced to 1% by weight or less.

The powder dried and granulated as described above is cooled to below its melting point and taken out from the lower part of the apparatus.

The gas is separated from the gas by a cyclone 7 via a pipe 17, and finally taken out as a product from a rotary valve 8.

Note that if the wall surface is cooled by the cold air jacket 20 provided on the outside of the wall surface of the spray drying apparatus main body 1, melting of the material deposited on the wall surface can be completely prevented.

In addition, the gas separated by the cyclone 7 is filtered through a filter 18.
The liquid is cooled in a condenser 19 via a circulation blower 9, liquid components such as accompanying solvent are removed, and the liquid is circulated for reuse.

In this example, nitrogen (N) was used as the drying gas.

) gas was used, but if a nonflammable solvent is used, air may be used, and in addition, C01Co2. Gases such as Ar and He can be used.

In addition, as a stock solution, solid content or non-volatile or hardly volatile components that have thermoplasticity and volatile substances (solvent) are used.
For example, by using a liquid containing paint components, the amount of residual solvent in the product powder can be reduced to 1% by weight or less, and it can be used as a final powder paint product. This is preferable because it can be done.

Furthermore, to form a cold air zone, the temperature of the cold air gas blown into the main body from the side of the device is usually -20 to 4
0°C, preferably -10 to 208C. If the temperature of the cold air gas is lower than -10°C, it may cause local condensation around the air inlet, while if it is higher than 20°C, the solvent concentration in the system will increase, reducing the amount of residual solvent in the product. becomes higher.

Moreover, about 3 to 10 nozzles 13 are usually provided in the circumferential direction of the side part of the apparatus main body 1, and the cold gas wind speed passing through the nozzles 13 is generally preferably 5 m/sec to 30 m/sec.

FIG. 2 is a partially cutaway explanatory view showing another embodiment of the present invention.

In this case, the difference from the embodiment shown in FIG.
Instead, a rotary blowing device 21 is provided which moves along the inner periphery of the side of the main body of the device and blows out cold air from multiple holes.

Therefore, in the case of FIG. 2 as well, the rotary blowing device 9721 blows cold air from the side of the device main body l in the circumferential direction.
Similar to the embodiment shown in Fig. 1, a hot zone is formed in the center, and a cold air zone is formed around the hot zone at the outer periphery, so that the amount of residual solvent in the product powder is can be 1% by weight or less.

In addition, the rotary blowing device 21 has a hole diameter of 1 to 3.
mm (φ) and a hole pitch of 10 to 60 mm, the blowing gas pressure is 500 to 3000 mmAq, and the moving speed is 5 to 15 m/min (circumferential speed).

Hereinafter, the spray drying method and apparatus of the present invention will be explained in more detail.

(Example 1) A device of the type shown in Fig. 1 [diameter 1600 mm (φ), straight body height 1000 mm, total height 2040 mm, the upper part is cylindrical, the lower part is funnel-shaped (the lowest part diameter is 400 mm (φ) ], the stock solution was spray-dried.

The processing conditions were as follows.

Stock solution: A mixture of epoxy resin, inorganic coloring pigment and solvent (methyl ethyl ketone (MEK)).The epoxy resin is M
It dissolves in EK, but inorganic color pigments do not dissolve in MEK.

Stock solution composition: Epoxy resin 20% Inorganic coloring pigment (titanium and others) 13% MEK 67% Softening point: Epoxy resin softening point approximately 90°C Stock solution processing:
1k: 7, 5 kg/Hr hot air temperature: 18
0°C Hot air: 11-: 120kg/Hr (N2 residue used) Cold air temperature 20°C Cold air volume: 140kg/Hr (N, gas) Exhaust air temperature: 52°C Hot zone temperature = 120°C Number of nozzles: 5 When processing was carried out at a cold gas wind speed of 20 m/sec or more through the nozzle, there was no residual solvent in the product.
．． At 8% by weight, the product recovery was 85%.

In addition, although there was some powder deposited in the funnel-shaped part inside the main body of the spray drying apparatus, it was not melted.

(Example 2) Using an apparatus of the type shown in FIG. 2, a stock solution was spray-dried. The stock solution used and the shape of the device body were the same as in Example 1.

The processing conditions were as follows.

Raw solution processing amount near, 5 kg/Hr Hot air temperature: 180°C Hot air volume: 120 kg/Hr (using N2 gas) Cold air temperature: 0”C Cold air 74: l 20 kg/Hr (N
a gas used) Exhaust air temperature = 56°C Hot zone temperature: 120°C In addition, the rotary blowing device 21 has a hole diameter of 2 mm (φ),
A pipe with a hole pitch of 20 mm was used, the blowing gas pressure was 1,000,100 O, and the moving speed was 10 m7 (circumferential speed).

When the treatment was carried out under the above conditions, there was no residual solvent in the product.
．． At 9% by weight, the product recovery was 95%.

Moreover, there were almost no old publications inside the spray drying apparatus.

(Comparative Example 1) A spray drying process was performed using an apparatus having the same shape as the apparatus body used in Example 1 (however, no nozzle for forming a cold air zone was used).

The processing conditions were as follows.

Stock solution processing amount near, 5kg/Hr Hot air temperature near 0℃ DI! Air volume: 200kg/Hr (N, gas used)
When processing was carried out under conditions such as exhaust air temperature = 50°C, the residual solvent in the product was 4.
．． At 5% by weight, product recovery was 30%.

Also, although a large amount of powder was deposited on the funnel-shaped part of the main body of the spray drying apparatus, it was not melted.

(Comparative Example 2) A spray drying process was performed using an apparatus body having the same shape as the apparatus body used in Example 1 (however, no nozzle for forming a cold air zone was used).

The processing conditions were as follows.

Amount of raw solution processed: 10 kg/Hr Hot air temperature: 150°C Hot air volume: 1 40 kg/Hr (N2 gas used) When processing was carried out at an exhaust air temperature of 280°C or higher, the residual solvent in the product was 2.
．． At 3% by weight, the product recovery was 5%. In addition, powder adheres to the cylindrical part and funnel-shaped part of the spray drying equipment main body,
Most of it was melted.

(Effects of the Invention) As explained above, the spray drying method and apparatus of the present invention blows in the circumferential direction from the side of the apparatus main body to further form a cold air zone on the outer periphery of the hot zone, so that residual solvent in the product powder can be removed. The amount can be reduced to 1% or less, which is extremely useful especially for the production of powder coatings.

[Brief explanation of drawings]

Fig. 7 is a partially cutaway explanatory view showing one embodiment of a spray drying apparatus for unreleased IJ1, Fig. 21'A is a partially cutaway explanatory view showing another embodiment of the present invention, and Fig. 31'4-4 The figure is a schematic cross-sectional view showing a conventional spray drying apparatus. l...Device body, 2...Hot air inlet, 3...Exhaust port, 4...Heater, 5...Nozzle, 6...Product outlet, 7...Cyclone, 10... Spray disk, 11.
...tank, 12... stock solution atomization device, 13... nozzle, 14... filter, 15... N2 heater, 16... secondary cold air blower, 17... piping, 18
...Filter, 19...Capacitor, 20...
Cold air jacket, 21...rotary blowing device.

Claims (8)

[Claims] (1) In a spray drying method in which fine droplets are produced by spraying a stock solution into minute droplets and drying them, a hot zone consisting of the powder obtained by instantaneously drying the minute droplets and drying gas is formed around the hot zone. A spray drying method characterized in that a cold gas is introduced into the powder to form a cold air zone, and a mixed gas of drying gas and cold gas is discharged at a temperature below the melting point of the powder. (2) The spray drying method according to claim 1, wherein the stock solution is a liquid containing a thermoplastic substance and a volatile substance that are solids or non-volatile or hardly volatile components. (3) The temperature of the hot zone is relative to the melting point of the dry powder.
The spray drying method according to claim 1, wherein the spray drying method is 0.7 times to 2 times. (4) The spray drying method according to claim 1, wherein the drying gas and the cold gas are inert gases. (5) The spray drying method according to claim 1 or 2, wherein the stock solution is a liquid containing paint components. (6) In a spray drying device that sprays a stock solution into minute droplets and dries them to produce a fine powder, the stock solution is installed at the top of the device body and is used to spray the stock solution and dry it with drying gas. A spray drying device comprising an atomization device and a cold gas blowing means for blowing cold gas into the side of the device body. (7) The spray drying apparatus according to claim 6, wherein the cold gas blowing means is a nozzle device provided in the circumferential direction on the side of the apparatus main body. (8) The spray drying device according to claim 6, wherein the cold gas blowing means is a rotary blowing device that blows out cold gas from multiple holes while moving along the inner circumference of the side of the device body.