JPS5992017A - Spray drying method and its apparatus - Google Patents

Abstract

PURPOSE:To obtain a spray dried particle of which the contained fine particles each comprising a magnetic material are oriented in the same direction, by acting a unidirectional magnetic field for orienting fine particles each comprising a magnetic material in slurry liquid droplets injected from a sprayer in an undried state on said slurry liquid droplets. CONSTITUTION:When a slurry containing fine particles each comprising a magnetic material is spray dried by a drying tower 14, a unidirectional magnetic field for orienting fine particles each comprising the magnetic material in slurry liquid droplets is acted on said slurry liquid droplets injected from a spray nozzle 32 in an undried state by an electric type magnetic field generating means comprising a coil 42. By this method, a spray dried particle of which the fine particles comprising the magnetic material are oriented to a same direction. By preparing ferrite according to a dry ferrite method by using this spray dried particle, residual magnetic flux density and energy product almost equal to that of ferrite prepared according to a wet ferrite process by using the same magnetic fine particles can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spray drying method and apparatus that can be particularly effectively used for spray drying magnetic materials.

Ferrai 1 - A magnet that combines powdered magnetic materials, such as a magnet! The following dry ferrite method is known as one of the 1iJJ methods. That is, for example, BaCO3 or 5
Magnetic materials such as rC(h and re203 are mixed in advance in, for example, a wet ball mill, then primary fired in, for example, a rotary kiln, then coarsely ground in, for example, a hammer mill or vibration mill, and then further mixed in, for example, in a vibration mill, for example. Grind into fine particles of about 1 micron. And for example,
Spray dry the fine particle slurry using a spray dryer. When a slurry of fine particles is spray-dried, the sprayed slurry becomes a sphere containing a large amount of fine particles due to surface tension, and is ejected into hot air and dried to remove weight. As a result, spray-dried particles having a size of about 40 to 100 microns, which are an aggregate of many fine particles, are obtained. Thereafter, the spray-dried particles thus obtained are sized using, for example, an automatic sieve, placed in a mold and subjected to a magnetic field, and pressed using, for example, a hydraulic press, followed by secondary firing and finishing. This is the way to do it. This manufacturing method is very convenient as it allows magnets of any shape to be easily made. However, such dry ferrite is produced by the so-called wet ferrite method, in which particles of a magnetic material of about 1 micron are made into a slurry, put directly into a mold, pressed while applying a magnetic field, and then dried. Compared to , the residual magnetic flux density (Rr) and energy product (13・l()max) of the magnet are small.For wet ferrite, this is the minimum median of magnetic materials;
This is thought to be due to the fact that all of the fine particles of about 1 micron, which are the constituent units, are oriented in the same direction, whereas in dry ferrite, the fine particles are not all oriented in the same direction. .

That is, in the dry ferrite method, particles of 40 to 100 microns, which are an aggregate of magnetic material*1111 particles obtained by IIJN mist drying and particle sizing, and are about the size of a fingernail are placed in a mold and subjected to a magnetic field. However, this only causes the overall magnetic direction of the individual particles of 40 to 100 microns obtained by spray drying to be oriented in the same direction; This is because each of the many fine particles of the magnetic material, each of which has a diameter of about 1 micron, remains randomly oriented within the particle. The reason for this is that when spray-drying a slurry of fine particles of magnetic material with a size of about 1 micron to create particles of about 40 to 100 microns, the fine particles of magnetic material in the droplets of the undried slurry drop. Since the particles are randomly oriented and dried as they are, in the dried particles of about 40 to 100 microns,
The smallest medium fine particles remain randomly oriented,
When these particles are placed in a mold to create the final form of Ferai I, even if a magnetic field is applied, the microscopic particles within each particle cannot move freely and change their direction. This is because they are unable to do so. Therefore, if all the fine particles of the magnetic material in the particles of about 40 to too microns obtained by spray drying are oriented in the same direction in advance, the residual magnetic flux density will be the same as that of wet ferrite even if the dry ferrite method is used. (llr) and energy product (B・H')
Ferrite with 1Ilax can be made.

However, in conventional spray drying, it has not been possible to obtain spray-dried particles in which fine particles of magnetic material contained are oriented in the same direction.

Therefore, the present invention aims to provide a spray drying method and apparatus capable of obtaining spray-dried grains in which fine particles of magnetic material contained therein are oriented in the same direction.

That is, according to the present invention, when spray drying the magnetic material F1 fine particles, the magnetic material fine particles within the slurry droplets are oriented in the same direction on the undried slurry droplets discharged from the sprayer. A spray drying method is provided which is characterized by applying a unidirectional magnetic field for orientation. In the t1' method, a magnetic field generating means for generating a unidirectional magnetic field is placed near the slurry spraying port of the sprayer, which generates a unidirectional magnetic field that follows the course of the undried slurry liquid jetted from the sprayer. Spray drying according to the present invention 1 characterized by
This can be done by using the ``%A'' position.

I-11o)! +++ By doing so, when the undried slurry l(k droplet passes through a unidirectional magnetic field, all the magnetic 111A fine particles in the droplet are oriented in the same direction, and After passing through the unidirectional magnetic field, there is a shadow on the slurry skin :)! There is no magnetic field, so
The slurry droplets are dried with all of the fine particles of magnetic material oriented in the same direction. Therefore,
The particles that have been spray-dried have a magnetic 1'l
+Afli': All fine particles are oriented in the same direction. Therefore, using such particles, one is made by the dry ferrite method), -I is made by the wet ferrite method, and the residual magnetic flux density (B
r) and energy i'l(+3·IDmax).

In order to orient all the fine particles of magnetic material in the slurry droplets in the same direction, each slurry l+k? Since it is sufficient to apply a magnetic field in the direction of 50.1' deep L'1° to +N, even if the unidirectional magnetic field 1iil is parallel to the direction of the slurry droplet flow, the droplets will not be applied to the slurry l+. It may be in a direction that crosses the flow, and the lines of magnetic force in the unidirectional magnetic field may be straight at GJ or may be slightly curved.

Further, the means for generating the unidirectional magnetic field may be a permanent magnet, but an electric (magnetic field generating means) such as an electromagnet or a magnet is preferable.

Therefore, in one embodiment of the present invention, an electric magnetic field generator U2 is used to generate a one-way signal z1.

Then, every time some fine particles of magnetic material adhere to the magnetic field generating means (:1)
Then, after a time delay, the electric magnetic field generating means is deenergized and the electric magnetic field generating means is stopped.
′, drop the 1゛1γi that has adhered between 1 and 1, then energize the electric charge magnetic field generating means, and then spray with a time delay)J■ opens the spray i11″υ゛f!JJ
Squirting while repeating the process appropriately? 1 (*2: Dry. Also,
Yu! /i! The cows are raised and drowned in the river with a cover made of non-magnetic 11-mesh 411 to which slurry droplets do not easily adhere.

The present invention will be described in detail with reference to the accompanying drawings.

The attached drawing shows a schematic configuration of a spray drying apparatus in which the present invention is implemented. 12, and a rotary valve 16 is provided at the lower end of the drying tower 14.
1111j) can be taken out to the crystal link 18. Cylindrical shape of drying tower 14” Part 2
A hot air supply chamber 20 for circulating hot air and supplying it to the drying tower is installed on the ceiling of 0, and a hot air duct]・22
It is connected to the air heater 24 via. A blower 26 is connected to the air heater 24. In addition, in the center of the conical lower part j2 of the drying tower 14, there is an exhaust port 2.
8 is arranged, and an exhaust duct 29 extending from the exhaust Fil 2 B is connected to an exhaust fan 30. and,
On one side of the exhaust air 1-128, a negative flow nozzle is arranged as a spray nozzle 32, and its spray ↑Y nozzle 32 is connected to the pump 3 via a pipe 34, and the pump 3
In addition, it is connected via a valve 40 to a slurry tank 38 that stores a slurry of fine particles of magnetic H material of about 1 micron in size. The configuration described below is conventionally known, so a description of its operation will be omitted.

In such a spray drying apparatus, according to the present invention, a coil 42 is installed in the spray nozzle 32 "immediately" so as to surround the course of the spray, and the coil 42 is installed in a non-woven material to which slurry droplets do not easily adhere. It is covered with a coil cover 44 made of a magnetic material, for example an aluminum cover coated with Teflon. When generating a magnetic field in the same direction as the spray flow, a coil wound around the spray flow with the center of the spray flow as the central axis is used as the coil 42. When generating an &I field in a direction across the spray stream, a pair of wound coils like the water i1Z deflection coil of the deflection yoke of a cathode ray tube or the vertical deflection coil are prepared and arranged so as to narrow the spray stream. In the case of one-many person,
It is preferable to wrap the outside with a magnetic hand to prevent the magnetic field from leaking to the outside.

Next, the operation will be explained. First, the -toil 42 is energized with direct current and air is applied! ! ) The fan 24, the blower 26, and the υ1 fan 30 are operated. In this way, the hot air is swirled and supplied from the hot air supply chamber 20 to the drying tower 14, and the swirling hot air descends while swirling along the inner circumferential surface of the drying tower 14, as shown by the arrow, and lowers the conical lower part of the drying tower 14. At the bottom of 12, the air turns around and rises while turning around the center, enters the exhaust air D2B-1, and is discharged through the υ1 air duct 29 by the air exhaust fan 30.

In this state, the pump 26 is operated to spray the slurry from the spray nozzle 32. The atomized slurry, which is atomized by the atomizing nozzle 32 into slurry droplets of, for example, 40 to 100 microns, passes through the coil 42 in a wet state. At that time, the magnetic material inside the slurry droplet is
The 1γ molecules are all oriented in the same direction under the influence of a magnetic field.

Hidden °C1 When looking at each droplet, the slurry droplets, in which all the fine particles of magnetic material within the droplet are oriented in the same direction, are directed toward the swirling downward hot air as shown by the dotted line.
3t, first flew upwards against the hot air while being subjected to the drying effect of the hot air, then swirled downward while being subjected to the drying effect of the hot air, swirled downward with the hot air, and became dry 4 0-1 (1 (l i spherical particles) and collect at the bottom of the conical lower part 12. On the other hand, the air that has been heated by the slurry droplets is discharged outside the tower from the exhaust air r128. Therefore, 11 - By keeping the tally valve 16 open appropriately or by periodically opening the rotary valve 16, the spray-dried particles can be
It can be taken out to the product tank 18.

Note that since the fine particles contained in the slurry are the magnetic material r1, it is inevitable that the slurry droplets and dried particles will adhere to the coil cover 44 to some extent. Therefore,
Do not repeat the following removal operation appropriately. That is, the spraying operation is interrupted by turning the pump 36 4'; The attached spermatozoa are allowed to fall naturally from the coil cover 44. At this time: The I-il cover may be vibrated. After that, 21 Il 42 II1
．． energizes the pump 36 and then activates the pump 36 again with a time delay. Restart 15i. in this case,
It is preferable that the coil cover has a simple shape so that attached particles can easily fall off.

Spray-dried particles (40 to 10
When ferrite was made using the dry ferrite I method using magnetic particles (approximately 0 microns), ferrite was made using the wet ferrite method using the same fine particles of magnetic material!・Residual magnetic flux density (r) and energy product (B ・II
) may have had.

In the actual travel example below, a spray nozzle (-
Although a fluid nozzle) was used, it will be clear to those skilled in the art that a rotating disk, such as a rotating bowl-shaped disk, could alternatively be used. Further, although a coil is used as a magnetic field generating means, an electromagnet or a permanent magnet may be used instead.

[Brief explanation of the drawing]

The accompanying drawing is a cross-sectional view showing a schematic configuration of a spray drying apparatus embodying the present invention. 10... Cylindrical J: 14B, 12... Conical lower part, 14... Drying tower, 16... Rotary valve, 1
8...Product tank, 2o...Hot air supply room, 22...
・Hot air duct, 24...Air heater, 26...Blower, 28...Exhaust air "1.29...Exhaust duct, 3o
...Exhaust fan, 32...Spray nozzle, 34...Pipe, 36...Pump, 38...Slurry tank, 4
0... Valve, 42... Coil, 44... Coil cover.

Claims (6)

[Claims] (1) Spray magnetic feed fine particle slurry? ■Undried slurry sprayed from the sprayer during drying? II
i. A spray drying method characterized in that a unidirectional magnetic field is applied to the droplets to orient the fine particles of magnetic material within the slurry droplets in the same direction. (2) The spray drying method according to claim 1, characterized in that a unidirectional magnetic field is applied using an electric magnetic field generating means. (3) Stop the spraying by the spray 7ifA +J, ll, and then deenergize the electric magnetic field generating means with a time delay,
Particles attached around the electric magnetic field generating means are dropped,
Spray drying method according to claim 2, characterized in that spray drying is carried out by appropriately repeating the operation of energizing the electric magnetic field generating means again and then, with a time delay, initiating the spray by the spray machine. . (4) A magnetic field generating means for generating a unidirectional magnetic field that overlaps with the course of the undried slurry droplet stream ejected from the sprayer is disposed near the slurry spray "1" of the sprayer. Spray drying equipment. (5) A spray drying apparatus characterized in that the magnetic field generating means is a coil wound around a stream of undried slurry droplets ejected from a sprayer. (6) The spray drying apparatus according to claim 4rf1 or claim 5, wherein the magnetic field generating means is covered with a cover made of a non-magnetic material to which slurry droplets do not easily adhere.