JPH06172821A - Method and device for producing magnetic metal powder - Google Patents

Abstract

PURPOSE:To industrially, advantageously and continuously produce magnetic metal powders having a uniform and excellent magnetic characteristic by heating and dehydrating a material to be treated substantially kept standing on a belt, preventing the collision of the particles and the generation of fine powders and bringing the material into good contact with gas. CONSTITUTION:Iron compd. powders contg. iron oxide hydrate as the essential component are granulated into a granulated material having 1-20mm weight average particle diameter, a gas-permeable rection furnace having a gas- permeable belt is used with the granulated material as a raw material, the granulated material is continuously supplied on the belt, heated and dehydrated by a nonreducing gas to obtain the dehydrated material. The dehydrated material is simultaneously heated and reduced to obtain a reduced material. The reduced material is simultaneously heated and oxidized by an oxygen-contg. gas to continuously produce a magnetic metal powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing metallic magnetic powder. More specifically, the present invention relates to a manufacturing method and a manufacturing apparatus for continuously manufacturing metal magnetic powder useful for magnetic recording.

[0002]

2. Description of the Related Art In recent years,
Although various recording systems have been developed remarkably, the progress in reduction in size and weight of magnetic recording / reproducing devices is remarkable. Along with this, there is an increasing demand for higher performance of magnetic recording media such as magnetic tapes and magnetic disks. In order to satisfy such requirements for magnetic recording, magnetic powder having high coercive force and high saturation magnetization is required. Conventionally, as magnetic powder for magnetic recording, generally needle-shaped magnetite or maghemite or so-called cobalt-containing iron oxide obtained by modifying these magnetic iron oxide powders with cobalt is used, but in order to obtain a medium with higher output. Has started to use ferromagnetic metal powders with higher coercive force and saturation magnetization, so-called metal magnetic powders.

Such metal magnetic powder is generally manufactured by the following steps (1) to (3) using a powder of an iron compound mainly containing acicular hydrous iron oxide as a raw material. (1) A step of heating and dehydrating hydrous iron oxide to form iron oxide (heating and dehydrating step). (2) A step of heating the iron oxide in a reducing gas atmosphere such as hydrogen to reduce it to metallic iron (heating reduction step). (3) A step of vapor-phase oxidizing the metallic iron with an oxidizing gas such as an oxygen-containing gas to form an oxide film on the surface of the metallic iron particles (vapor-phase oxidizing step). Here, the metallic iron particles obtained in the step (2) are chemically unstable and undergo a rapid oxidation in the air, which significantly impairs the magnetic characteristics. Therefore, it is necessary to stabilize the metallic iron by the vapor phase oxidation step (3).

A metal magnetic powder useful for magnetic recording is required to have high coercive force and saturation magnetization as well as little variation in these magnetic characteristics. In order to obtain such a metallic magnetic powder, it is necessary to uniformly carry out the respective reactions of heat dehydration, heat reduction, and gas phase oxidation in the above three steps without impairing the acicular shape of the iron oxide hydroxide as a raw material. is there. All of these three reactions are carried out by contact between a gas and a solid, and conventionally, as a device used for such a reaction, a fluidized bed reaction system in which gas-solid contact is good is used. There are many
8-174509, JP-A-55-157214, JP-B-59-14081, and JP-A-59-1.
10701 gazette, JP-A-2-192103).
However, in these methods, there is a problem in that the agglomeration of the powder is promoted by the contact or collision of the powder particles with each other, the magnetic properties are deteriorated, and fine powder is generated and jumps out of the reactor.

On the other hand, the above problem can be solved by carrying out the reaction in a state where the powder to be reacted is allowed to stand, that is, in a fixed bed system, but this reaction system (for example, Japanese Patent Publication No. 60-48563).
Japanese Patent Publication No. 52242/1989) has the following problems. That is, the dehydration reaction of hydrous iron oxide and the hydrogen reduction reaction of iron oxide are represented by the following formulas (I) to (III).

[0006]

[Chemical 1]

In the fixed bed system, the steam generated by these reactions accumulates as the bed height (bed thickness) of the raw material particles increases, so that the steam partial pressure at the top of the bed becomes excessive. Then, the water vapor promotes the particle growth of the crystallites forming the acicular particles. Therefore, as the layer height increases, the size of the crystallites forming the skeleton particles (X-ray crystal grain size) becomes too large, resulting in needle-like deformation and sintering between skeleton particles,
The magnetic properties of the obtained metal magnetic powder are deteriorated. Furthermore, since the reaction of (III) is a reversible reaction, as the bed height increases, the reduction reaction rate decreases due to the influence of the generated steam, and the reduction becomes non-uniform.

Further, the saturation magnetization (σs) of the magnetic metal powder is reduced by vapor phase oxidation, and the amount of reduction is uniquely determined by the vapor phase oxidation temperature. When this gas phase oxidation is carried out in a fixed bed system, the reaction heat generated by the oxidation reaction is partially accumulated,
Only that part may become hot and the saturation magnetization may be reduced more than necessary, or conversely, a part that is not oxidized due to the drift of the gas may occur. As a result, the obtained magnetic metal powder has very different saturation magnetization. In some cases, when taken out into the atmosphere, a non-oxidized portion may generate heat or ignite due to a rapid oxidation reaction, and the original coercive force and saturation magnetization may be significantly impaired. Further, such partial accumulation of reaction heat and gas drift are more likely to occur as the bed height is increased in the fixed bed system. The problems in performing heat dehydration, reduction and gas phase oxidation by such a fixed bed become more remarkable as the bed height increases, and (fixed bed bed height /
It can be solved to some extent by reducing the tower diameter). However, such a fixed bed batch reaction system has a very poor production efficiency and is not suitable as an industrial production method.

It is an object of the present invention to prevent the shape change of particles and the sintering of particles at the production stage of such metal magnetic powder, and to provide the metal magnetic powder showing uniform and excellent magnetic characteristics on an industrial scale. An object of the present invention is to provide a manufacturing method and a manufacturing apparatus for mass-producing continuously with high efficiency.

[0010]

DISCLOSURE OF THE INVENTION As a result of studying the above-mentioned problems, the inventors of the present invention have found that a gas flow type reactor having a belt through which heat dehydration, reduction and gas phase oxidation can be carried. By using the above, it is possible to obtain a metal magnetic powder that exhibits uniform and excellent magnetic characteristics without causing shape change of particles and sintering of particles even in a reaction in a substantially static state, and The present invention has been completed by finding that the magnetic metal powder can be industrially advantageously continuously produced.

That is, the gist of the present invention is as follows: (1) An iron compound powder mainly containing hydrous iron oxide is granulated to obtain a granulated product having a weight average particle diameter of 1 to 20 mm, and the granulated product is used as a gas. A method for producing a metallic magnetic powder containing metallic iron as a main component, which comprises performing the following steps (a) to (c) using a gas flow type reaction furnace having a flowable belt: And (a) the granulated product is continuously supplied and placed on a belt, and while the granulated product is being transferred, heat dehydration treatment is performed with a non-reducing gas to continuously obtain a heat dehydrated product. Step, (b) The heated dehydrated product obtained in the step (a) is continuously supplied and placed on a belt, and while the heated dehydrated product is being transferred, a heating reduction treatment is performed with a reducing gas to perform reduction. The step of continuously obtaining the product and (c) reducing the product obtained in step (b) A step of continuously supplying and placing on a glass plate, carrying the reduced gas while carrying out a heating vapor phase oxidation treatment with an oxygen-containing gas, and continuously obtaining a metallic magnetic powder containing metallic iron as a main component, (2) A heating dehydration reaction furnace for heating and dehydrating a granulated product of an iron compound powder mainly containing iron oxide hydroxide, a heating reduction reaction furnace for heating and reducing the heated dehydration product obtained from the reaction furnace, and a reaction furnace A heating apparatus for producing a magnetic metal powder, comprising a heating vapor-phase oxidation reaction furnace for heating and vapor-oxidizing a reduced product, wherein these reaction furnaces are heated and dehydrated at least through a powder transport means, and heated. A reduction flow reactor and a heating vapor-phase oxidation reaction furnace are connected in series in this order, and each reaction furnace has a gas flow-type reactor main body having a gas inlet and a gas outlet, and a supply port and a discharge port for the object to be treated. , Gas distribution provided in the reactor body A belt conveyor for transporting a processed material having a possible belt, a gas dispersion plate for uniformly dispersing and supplying the gas introduced from the gas inlet to the belt surface on which the object to be processed is mounted, and in the reaction furnace main body The present invention relates to an apparatus for producing magnetic metal powder, which is a gas flow type reaction furnace provided with a heating means arranged to heat a gas.

First, the gas flow type reaction furnace constituting the production apparatus used in the method for producing metallic magnetic powder of the present invention will be described.
This will be described with reference to FIG. 4, which is a schematic explanatory diagram. The gas flow type reaction furnace in the present invention is a gas flow type reaction furnace main body having a gas inlet and outlet, and a supply port and a processed product discharge port of a processing object, and a gas provided in the reaction furnace main body. A belt conveyor for transporting a processed material having a flowable belt, a gas dispersion plate for uniformly dispersing and supplying the gas introduced from the gas inlet to the belt surface on which the object to be processed is mounted, and the reactor main body It comprises a heating means arranged to heat the inside. That is, the reactor main body 40 is a sealed horizontal container having a gas inlet 44, a gas outlet 45, a workpiece supply port 46, and a treated product outlet 47. A heating means 43 is provided around the reactor body. The heating means is not particularly limited as long as it can heat the object to be processed to the processing temperature. For example, a combustible fuel combustion method, an electric furnace method, a jacket method, or the like can be used. In addition, in the present invention, in order to keep the processing temperature in the reaction furnace main body 40 constant, the heat is normally maintained by using a heat insulating material.

A belt conveyor 41 is provided in the reaction furnace main body for transferring an object to be processed. The shape of the belt is an openable endless belt or the like which has openings that can hold the granulated object and has an opening ratio that reduces the pressure loss when gas flows through the pores of the belt surface. There is no particular limitation as long as it exists. For example, a mesh belt, a perforated plate belt, etc. may be mentioned. Further, the drive device for transfer is not particularly limited, and for example, a rotation speed variable motor is suitable.

In the reactor main body, a gas dispersion plate 42 is provided in order to uniformly disperse and supply the gas introduced from the gas inlet 44 to the belt surface on which the granulated object to be treated is placed. As the gas dispersion plate, various shapes such as a porous plate, a sintered metal plate, a wire mesh type, and a cap type can be adopted. Further, the gas dispersion plate may be installed on the upper side of the belt on which the granulation object is placed, or on the lower side of the return surface of the belt, but preferably, the gas sealing is easy, so that FIG.
As shown in, it is installed between the surface on which the granulation object is loaded and the return surface. At that time, one dispersion plate may be installed according to the effective processing length of the belt (the length of the belt surface on which the object to be processed is placed), or several dispersion plates may be installed in the running direction of the belt. It may be installed continuously. The gas supply to the gas dispersion plate 42 is preferably performed by a blower or the like having a discharge pressure equal to or higher than the pressure loss when the gas flows through the gas dispersion plate, the belt, the object layer, and the like.

The gas flow reactor of the present invention has an appropriate gas seal structure so that the gas ejected from the gas dispersion plate can effectively flow through the belt surface without passing through the side surface (end portion) of the belt. Is preferably provided. Examples of this structure include a structure in which a seal wall is provided on the side surface of the gas dispersion plate and the belt, and a structure in which the side surface of the gas dispersion plate and the belt are in close contact with the side wall of the reactor body.

Next, the apparatus for producing the metallic magnetic powder of the present invention constituted by the gas flow type reaction furnace will be explained. FIG. 5 is a schematic explanatory view of an example of a manufacturing apparatus suitable for the method for manufacturing the metallic magnetic powder of the present invention. As shown in the figure, the production apparatus of the present invention comprises a heating dehydration reaction furnace 51, a heating reduction reaction furnace 52, and a heating gas phase oxidation reaction furnace 53, which are connected in series in this order. Is connected via at least the powder transport means. Powder transport for continuously supplying the material to be processed (raw material granulated material) supply port 71 of the heat dehydration reaction furnace 51 to the material to be processed in the material storage tank 54 on the mesh belt in the reaction furnace. The means, for example, the powder feeder 55, is directly connected. Similarly, the powder feeder 58 is provided in the supply port 73 for the object to be treated (heated dehydration product) of the heating reduction reaction furnace 52, and the powder feeder 58 is provided in the supply port 75 for the object to be treated (reduced product) in the heating gas phase oxidation reaction furnace 53. The body feeders 61 are directly connected to each other. As the powder feeder, various known types such as a screw feeder, a rotary feeder and a gate type feeder can be adopted.

Discharge ports 72, 74, 7 of each reactor
6 is a treated product storage tank 5 for collecting the treated products.
6, 59 and 62 are connected. This treated product storage tank 56
The powder supply valves 63 and 64 respectively supply the heated dehydrated product from the processed material storage tank 57 to the processed material storage tank 57 and the reduced product from the processed material storage tank 59 to the processed material storage tank 60. In addition, the gas, the object to be treated, and the object to be treated do not come into direct contact with the atmosphere, or the gases flowing through the reaction furnaces do not mix with each other, these object-to-be-treated storage tanks 54, 57. , 60 and the treated material storage tanks 56, 59, 62 are purged with nitrogen gas.

Next, the method for producing the metallic magnetic powder of the present invention will be described. According to the production method of the present invention, an iron compound powder mainly containing hydrous iron oxide is granulated to obtain a weight average particle diameter of 1
A granulated product having a size of 20 mm and a gas flow type reaction furnace having a belt through which the granulated product can be used as a raw material, and a treatment including the following steps (a) to (c) is performed. It is what (A) A step of continuously supplying and placing the granulated product on a belt and carrying out a heat dehydration treatment with a non-reducing gas while transferring the granulated product to obtain a heated dehydrated product continuously. (B) The heated dehydrated product obtained in the step (a) is continuously supplied and placed on a belt, and while transferring the heated dehydrated product,
Step of performing heat reduction treatment with a reducing gas to continuously obtain a reduced product (c) The reduced product obtained in the step (b) is continuously supplied and placed on a belt, and the reduced product is transferred. However, the step of performing a heating gas phase oxidation treatment with an oxygen-containing gas to continuously obtain a metal magnetic powder containing metallic iron as a main component The production method of the present invention can be suitably performed using the production apparatus described above. it can.

The raw material used in the present invention is an iron compound powder mainly containing hydrous iron oxide. Examples of the hydrous iron oxide include α-FeOOH, β-FeOOH, and γ-Fe.
OOH is mentioned. Elements such as cobalt, zinc, copper, chromium, nickel, silicon, aluminum, tin and titanium may be added to these iron oxide hydroxides. The particle shape of the iron compound powder mainly containing hydrous iron oxide is not particularly limited as long as it is needle-like, and specifically, it includes strips, spindles, spindles, rice grains and the like. Among these, the effect of the present invention becomes more effective particularly when fine particles of needle crystals having a length of 0.3 μm or less and an axial ratio of 5 or more are used.

In the present invention, in each step of the heat dehydration treatment, heat reduction treatment, and heat vapor phase oxidation treatment, the object to be treated is held by the belt through which gas can flow and the object to be treated is belted by the gas flow. Granules having a larger particle size than the iron compound powder as the raw material, that is, the iron compound powder, in order to prevent the objects to be processed from contacting each other in the fluidized state above and further preventing the objects to be scattered The material to be treated which is granulated is used as a raw material.

At this time, the shape of the granulated product is not particularly limited, but it is preferable to use a granulated product having a weight average particle diameter of 1 to 20 mm. When the granulated product is less than 1 mm,
In each step of the heat dehydration treatment, heat reduction treatment, and heat vapor phase oxidation treatment, when the gas is brought into contact with the granule at a preferable gas flow rate, the granule tends to be in a fluidized state. As a result, fine powder is generated, granules are scattered from the belt,
Further, the magnetic properties are deteriorated due to the collision of the granulated materials. If the granulation product exceeds 20 mm, the diffusion of the processing gas, generated steam, etc. in the granulation product in each of the above-mentioned steps will be poor, and the processing will be non-uniform. A known method is used as the granulation method, and examples thereof include stirring rolling granulation, fluidized granulation, extrusion granulation, and crush granulation.

In the manufacturing method of the present invention, the above-mentioned raw materials are used, and (a) is used in each of the reaction furnaces 51, 52 and 53 of FIG.
Although the steps (b) and (c) are sequentially performed, the processing method common to each step will be described below with reference to FIG. The gas is introduced from the gas inlet 44, dispersedly supplied from the gas dispersion plate 42 to the surface of the belt 41 through which the gas can flow, passes through the holes on the surface of the belt 41, and the gas outlet 4
Emitted from 5. In this way, while the gas is flowing through the belt, the inside of the reaction furnace main body 40 is heated by the heating means 43 at a predetermined processing temperature. The gas introduced from the gas inlet 44 may be heated by an external heat exchanger (not shown) or the like. On the other hand, the object to be processed is continuously supplied onto the belt 41 through the supply port 46 of the object to be processed and placed, and the object to be processed is transferred by the belt conveyor 41 in the direction of arrow A shown in the figure. Gas is circulated in the material layer to continuously perform the heat reaction treatment. The obtained processed product is collected from the processed product outlet 47.

Next, conditions and the like peculiar to the respective steps (a), (b) and (c) will be described below. [Step (a)] In the step (a), the raw material granulated product is continuously supplied and placed on a belt in a heating dehydration reaction furnace, and the granulated product is transferred while being non-reducing. In this step, a heated dehydration product is continuously obtained by heating with a gas. The non-reducing gas to be used is not particularly limited as long as it has no reducing power, and may be air or an inert gas. N ₂ , He, Ne, A as the inert gas
r, CO _{2 and the} like may be used alone or as a mixture.

Although the preferable gas flow rate of the non-reducing gas varies depending on the particle size of the granulated product, it is preferably 2 cm / sec or more at a gas linear velocity vertically upward with respect to the belt surface, and 10 to 1
00 cm / sec is more preferable. The gas linear velocity is the velocity at the heating dehydration temperature. Gas linear velocity is 2
If it is less than cm / sec, the partial pressure of water vapor generated by the dehydration reaction becomes high, and the size of the iron oxide crystallites (X-ray crystal grain size) constituting the needle-shaped particles of the heated dehydration product becomes large. If it becomes too much, it will be deformed into a needle shape and sintering between skeleton particles will occur, and the magnetic properties of the finally obtained metal magnetic powder will deteriorate.

The layer thickness of the granulated product on the belt is usually 30 c.
m or less, preferably 25 cm or less. That is, as the layer is made thicker, the granules in the upper part of the layer will be heated and dehydrated by the non-reducing gas containing a larger amount of water vapor generated in the lower part of the layer. The needle-like shape is deteriorated, and the magnetic properties of the finally obtained metal magnetic powder are deteriorated, which is not preferable.

The heat dehydration temperature is preferably 350 to 700 ° C, more preferably 400 to 650 ° C. Dehydration at a heating temperature of less than 350 ° C. is not preferable because the dehydration pores formed in the skeleton particles at the time of dehydration are not sealed and the magnetic properties of the finally obtained metal magnetic powder deteriorate. If the temperature exceeds 700 ° C., the acicular shape of the skeleton particles collapses and the magnetic properties deteriorate, which is not preferable.

Residence time in the heating dehydration reaction furnace main body, that is, the time from the feed of the raw material granules onto the belt in the reaction furnace main body until it exits from the discharge port of the processed product (heating dehydration product) (heating dehydration The time is usually 0.5-, though it depends on the above conditions.
It is 5 hours, preferably 0.5 to 2 hours. When the time is shorter than 0.5 hours, the heat dehydration is insufficient, and when the time is longer than 5 hours, there is no problem in terms of the quality of the metal magnetic powder, but the production efficiency is lowered, which is not preferable. In the present invention, heat dewatering is performed by thus providing a certain residence time,
Since it is possible to perform heat dehydration in a substantially stationary state, there is no collision between particles or generation of fine powder, and the contact between the object to be treated and the non-reducing gas is good, and heat dehydration is uniform. It can be performed. Such a residence time can be usually adjusted by changing the traveling speed of the belt by controlling the driving motor or the like.

[Step (b)] In the step (b), the heated dehydration product obtained in the above step (a) is continuously supplied and placed on a belt in a heating reduction reaction furnace, and the heating is performed. This is a step of continuously obtaining a reduced product by carrying out a heat reduction treatment with a reducing gas while transferring the dehydrated product.

As the reducing gas, pure hydrogen gas, CO gas or a mixed gas of these containing an inert component can be used, but pure hydrogen gas is preferably used. The preferable gas flow rate varies depending on the particle size of the granulated product, but is 10c at a gas linear velocity upward and perpendicular to the belt surface.
m / sec or more is preferable, 20 cm / sec or more is more preferable, and 30 to 100 cm / sec is particularly preferable. The gas linear velocity is the velocity at the reduction temperature. If the gas linear velocity is less than 10 cm / sec, the partial pressure of water vapor generated by the reduction reaction becomes high, and the size of the crystallite of metallic iron (X-ray crystal grain size) forming needle-shaped particles is large. If it becomes too much, needle-like deformation and sintering between skeletal particles occur, and the magnetic properties of the obtained metal magnetic powder deteriorate.

The layer thickness of the placed heat-dehydrated product on the belt is usually 25 cm or less, preferably 20 cm or less. That is, as the layer becomes thicker, the heated dehydration product in the upper part of the layer is reduced by hydrogen gas containing a larger amount of water vapor generated in the lower part of the layer, and the X-ray crystal grain size of the reduced product in the upper part of the layer becomes large. It is not preferable because the magnetic properties deteriorate. In addition, the reduction rate at the upper part of the layer is reduced and the reduction is not uniform, which is not preferable. If the layer thickness exceeds 25 cm, even if the gas linear velocity of hydrogen gas is 10 cm / sec or more as described above, the influence of the partial pressure of water vapor on the upper part of the layer cannot be ignored, which is not preferable.

The reduction temperature is preferably 300 to 700 ° C, more preferably 350 to 600 ° C. If the temperature is lower than 300 ° C., a reduced product having magnetic properties effective as a magnetic metal powder cannot be obtained, which is not preferable. If the temperature exceeds 700 ° C., the acicular shape of the skeleton particles collapses and the magnetic properties deteriorate, which is not preferable.

The residence time in the heating / reduction reactor main body, that is, the time from the supply of the heated dehydration product onto the belt in the reactor main body to the exit from the outlet of the reduced product (reduction time), is as described above. Depending on the conditions, it is usually 0.5 to 10 hours, preferably 1 to 8 hours. If the time is shorter than 0.5 hours, the reduction is insufficient, and if the time is longer than 10 hours, there is no problem in terms of the quality of the metal magnetic powder, but the production efficiency is low, which is not preferable. In the present invention, the heating and reduction are performed by providing a constant residence time in this manner, and since it is possible to perform the heating and reduction in a substantially stationary state, there is no collision between particles or generation of fine powder, Further, the contact between the object to be treated and the reducing gas is good, and uniform heat reduction can be performed. Such a residence time can be usually adjusted by changing the traveling speed of the belt by controlling the driving motor or the like.

[Step (c)] In the step (c), the reduced product obtained in the above step (b) is continuously supplied and placed on a belt in a heating gas-phase oxidation reaction furnace. This is a step of continuously performing a heat-induced gas phase oxidation treatment with an oxygen-containing gas while transferring a reduced product to continuously obtain a metal magnetic powder containing metal iron as a main component.

The oxygen-containing gas used in the present invention includes
A mixed gas of oxygen or air and an inert gas can be used. The inert gas is a gas which does not substantially react with the magnetic metal powder under the contact treatment condition, and specific examples thereof include N ₂ , He, Ne, Ar and CO ₂ alone or in a mixture. The oxygen concentration in the mixed gas is preferably 100 ppm or more and 2500 ppm or less, and 150 ppm or more and 2000
ppm or less is more preferable. Oxygen concentration in mixed gas is 10
If it is less than 0 ppm, it takes a long time for the heating gas phase oxidation treatment, which is not industrially preferable. If it exceeds 2500 ppm, the oxidation reaction rapidly occurs, the reaction temperature rises, and it becomes difficult to maintain a constant reaction temperature, which is not preferable.

The preferred gas flow rate of the oxygen-containing gas varies depending on the particle size of the granulated product, but is preferably 5 cm / sec or more, and 10 cm in the upward linear gas velocity perpendicular to the belt surface.
/ Sec or more is more preferable, and 15 cm / sec or more 1
It is particularly preferably not more than 00 cm / sec. The gas linear velocity is the velocity at the gas phase oxidation temperature. Gas linear velocity is 5
If it is less than cm / sec, the effect of removing the reaction heat by the gas flow becomes small, so that it becomes difficult to keep the reaction temperature constant, the reaction heat is partially accumulated, and only that part becomes high temperature, and the saturation magnetization becomes higher than necessary. May decrease. In addition, since a nonuniform flow of gas is likely to occur, a portion that is not oxidized may occur. As a result, a magnetic metal powder with extremely different saturation magnetization is obtained, and in some cases, when taken out into the atmosphere, the unoxidized part generates heat or ignites due to a rapid oxidation reaction, and the coercive force originally possessed. And the saturation magnetization may be significantly impaired, which is not preferable.

The layer thickness of the placed reduced product on the belt is usually 30 cm or less, preferably 25 cm or less. When the layer thickness exceeds 30 cm, even if the gas linear velocity of the oxygen-containing gas is 5 cm / sec or more as described above, the formation of an oxide film may be non-uniform due to partial accumulation of reaction heat or gas drift. Not preferable.

The vapor phase oxidation temperature is preferably 40 ° C. or higher and 150 ° C. or lower, and more preferably 50 ° C. or higher and 130 ° C. or lower. It is particularly preferably 50 ° C. or higher and 100 ° C. or lower. If the reaction temperature is lower than 40 ° C., the surface is not sufficiently oxidized, and it will ignite when taken out into the atmosphere. If the temperature exceeds 150 ° C., the surface is oxidized more than necessary and high saturation magnetization cannot be obtained, which is not preferable. Moreover, since the saturation magnetization of the metallic magnetic powder after heated vapor phase oxidation is uniquely determined by the reaction temperature, it is necessary to maintain the reaction temperature at a substantially constant reaction temperature within the above range depending on the desired saturation magnetization. The substantially constant reaction temperature is a predetermined temperature ± 5
Refers to ° C. If the reaction temperature fluctuates beyond ± 5 ° C, it is difficult to obtain a metal magnetic powder having a desired saturation magnetization.

The residence time in the heated gas-phase oxidation reaction furnace body, that is, the time from when the reduced product is supplied onto the belt in the reaction furnace body to when it exits from the discharge port of the treated material (heating gas-phase oxidation time) , Usually 1 to 20 hours, depending on the above conditions,
It is preferably 1.5 to 18 hours. If it is shorter than 1 hour, the stabilization treatment by heating vapor phase oxidation is insufficient, and if it is longer than 20 hours, there is no problem in terms of the quality of the metal magnetic powder, but the production efficiency is low, which is not preferable. In the present invention, the gas phase oxidation is carried out by thus providing a certain residence time, and since the gas phase oxidation can be carried out in a substantially stationary state, the particles collide with each other and the generation of fine powder occurs. In addition, it is possible to produce a metal magnetic powder that has good contact between the object to be treated and the oxygen-containing gas, has a uniform oxide film, and has excellent magnetic properties. Such a residence time can be usually adjusted by changing the traveling speed of the belt by controlling the driving motor or the like.

By the manufacturing method of the present invention as described above, it is possible to obtain a metallic magnetic powder exhibiting uniform and excellent magnetic characteristics while preventing the shape change of particles and the sintering of particles at the manufacturing stage. Further, in the production method of the present invention, since the reaction furnaces used for the heating dehydration treatment, the heating reduction treatment, and the heating vapor phase oxidation treatment are connected in series and each treatment is continuously performed, the above-mentioned metal magnetic powder is used. Can be continuously mass-produced on an industrial scale with high efficiency.

[0040]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (Example of Gas Flow Type Reactor) FIG. 1 is a longitudinal sectional view showing a gas flow type reactor according to the present invention. 2 and 3 are cross-sectional views of each part of the gas flow reactor. The size of the reactor body 1 is 390 mm in width, 520 mm in height, and 2900 m in length.
m. As a heating means, an electric furnace system using an electric heater 4 for heating and a heat insulating material 5 is adopted.

The belt 3 has a width of 300 mm and an effective processing length of 2
A steel endless mesh belt (mesh diameter 0.15 mm) of 000 mm. This belt is shown in FIG. 3 in order to prevent the object to be processed from falling off from the end of the belt.
The cross-sectional shape is as shown in. Then, this belt travels at a constant speed in the direction of arrow A in the figure by the belt drive roller 11 and the drive motor 21 provided outside the reactor main body. The roller drive shaft 12 is provided with a shaft seal 20 for sealing gas.

The gas dispersion plate 2 is a perforated plate having a cross section of 300 × 300 mm. Further, this gas dispersion plate is such that five dispersion plates are continuously installed below the surface of the mesh belt on which the object to be processed is placed. Further, as shown in FIG. 2, the gas seal wall 22 is provided so that the gas ejected from the gas dispersion plate does not pass through the side surface of the belt but effectively flows through the belt surface.

A powder feeder 13 for continuously supplying the object to be processed in the object storage tank 14 onto the mesh belt is directly connected to the object supply port 8 of the reaction furnace main body.
A screw feeder was used as the powder feeder.
Further, the thickness adjusting plate 10 is provided to make the object to be processed supplied on the mesh belt a constant layer thickness on the mesh belt, and has an adjusting mechanism capable of changing the layer thickness. The layer thickness depends on the feed rate of the object to be treated, the powder feeder 1
It can be adjusted by controlling the rotation speed of No. 3 and changing the set thickness of the thickness adjusting plate 10. The object having a constant layer thickness is moved in the direction of arrow A in the figure by the belt, is brought into contact with the gas introduced into the reactor main body from the gas inlet 6 and ejected from the gas dispersion plate, and is continuously processed. It The residence time of the object to be treated (the time from when the object to be treated is supplied onto the belt in the reactor body until it exits from the outlet 9 of the object to be treated), that is, the treatment time can be adjusted by the traveling speed of the belt, In order to appropriately control the belt traveling speed, the drive motor 21 has a mechanism capable of variably controlling the rotation speed of the motor. In order to collect the processed product obtained after a predetermined processing time, the processed product discharge port 9
A processed material storage tank 15 is connected to the. Further, the object storage tank 14 and the object storage tank 15 are purged with nitrogen gas so that the gas and the object are not in direct contact with the atmosphere.

Embodiment 2 (Example of Manufacturing Apparatus) As shown in FIG. 5, the manufacturing apparatus of this embodiment has a heating dehydration reaction furnace 51, a heating reduction reaction furnace 52, and a heating gas phase oxidation reaction furnace 53.
Are connected in series, and each reactor is connected via a powder supply valve. As the heating and dehydration reaction furnace 51, in the gas flow type reaction furnace of Example 1, the size of the reaction furnace main body was 390 mm in width, 620 mm in height, and 1 in length.
The same gas flow reactor is used except that the belt 3 has a width of 300 mm, the effective treatment length is 1000 mm, and three gas distribution plates 2 of 300 × 300 mm are continuously installed. As the heating / reduction reaction furnace 52, Example 1 was used.
I am using a gas flow reactor. As the heating vapor-phase oxidation reaction furnace 53, the length of the reaction furnace main body 1 is 3900 m.
m, the effective treatment length of the belt 3 is 3000 mm, and the gas distribution plate 2 is 8 in number, and the same gas flow reactor is used. A powder feeder for continuously supplying the material to be processed (raw material granulated material) supply port 71 of the heat dehydration reaction furnace 51 to the material to be processed in the material storage tank 54 on the mesh belt in the reaction furnace. 55 is directly connected. Similarly, a supply port 73 for the object to be treated (heated dehydration product) of the heating reduction reaction furnace 52
Is a powder feeder 58, and the heating gas-phase oxidation reaction furnace 53 is provided with a powder feeder 6 at a supply port 75 for an object to be treated (reduced product).
1 is directly connected. A screw feeder is used as the powder feeder.

Discharge ports 72, 74, 7 of each reactor
6 is a treated product storage tank 5 for collecting the treated products.
6, 59 and 62 are connected. Also, the processed material storage tank 5
6, powder supply valves 63 and 64 are provided between the processed material storage tank 57 and the processed material storage tank 59 and the processed material storage tank 60. Further, the object storage tanks 54, 57, 60 and the object storage tanks 56, 59, 62 are purged with nitrogen gas.

Example 3 (Production Example) As a raw material, needle-like α-FeOOH containing 4% by weight of Al with respect to Fe and having a primary particle size of 0.22 μm in major axis length and 10 in axial ratio. Was used to make a granulated product having a weight average particle diameter of 3 mm by extrusion granulation. By using the manufacturing apparatus shown in Embodiment 2 (see FIGS. 1 to 3 and 5),
The processes of steps (a), (b), and (c) were sequentially performed under the following conditions.

[Step (a)] Nitrogen gas was used as the non-reducing gas, and heat dehydration treatment was performed at 500 ° C. Nitrogen gas was circulated so that the linear gas velocity in the vertical upward direction with respect to the mesh belt surface was 8 cm / sec. The above-mentioned granulated material was filled in the material storage tank 54, and then continuously fed into the reactor body heated to the dehydration temperature by the powder feeder 55 at a rate of 8.5 kg / hr. The layer thickness of the granulated product on the mesh belt was set to 14 cm by the thickness adjusting plate. The granulated product was continuously heated and dehydrated while moving in the direction of arrow A in FIG. 1 together with the belt and in contact with the nitrogen gas flowing through the mesh belt. The residence time of the granulated product in the reaction furnace main body was set to 1.5 hours by adjusting the traveling speed of the belt by the belt driving motor provided outside the reaction furnace main body. Under the above setting conditions, 7.4 kg / hr is stored in the processed material storage tank 56.
To obtain a heated dehydrated product. This heated dehydrated product is supplied by the powder supply valve 63.
Was automatically opened and closed and continuously supplied into the object storage tank 57.

[Step (b)] Using hydrogen gas as a reducing gas, heat reduction was performed at 480 ° C. Hydrogen gas has a gas linear velocity of 50c vertically upward with respect to the mesh belt surface.
It was distributed so that it would be m / sec. The heated dehydration product in the processed material storage tank 57 is measured by the powder feeder 58 to be 7.4.
It was continuously fed into the reactor body heated to the heating reduction temperature at a rate of kg / hr. The layer thickness of the heated dehydration product on the mesh belt was set to 12 cm by the thickness adjusting plate. The heated dehydrated product moved in the direction of arrow A in FIG. 1 together with the belt and was continuously heated and reduced while being in contact with hydrogen gas flowing through the mesh belt. The residence time of the heated dehydration product in the reaction furnace main body was set to 3.0 hr by adjusting the traveling speed of the belt by the belt driving motor provided outside the reaction furnace main body. 5.3 kg / h in the treated material storage tank 59 under the above setting conditions
A reduced product of r was obtained. The reduced material was continuously supplied to the object storage tank 60 by automatically opening and closing the powder supply valve 64. Incidentally, a part of this reduced product was extracted and immersed in toluene,
Then, after air-drying in the air, a sample vibration type magnetometer (VS
When the magnetic characteristics were measured by M, the coercive force (H
c): 1600 [Oe], saturation magnetization (σs): 141
[Emu / g], squareness ratio (σr / σs): 0.52
It was [-].

[Step (c)] 500 as an oxygen-containing gas
using an air / nitrogen mixture containing ppm oxygen,
The heating vapor phase oxidation was performed at 70 ° C. The oxygen-containing gas has a gas linear velocity of 35 in the vertical upward direction with respect to the mesh belt surface.
It was distributed so that it would be cm / sec.

The above-mentioned reduced material in the material storage tank 60 was continuously supplied by the powder feeder 61 at a rate of 5.3 kg / hr into the reactor main body heated to the gas phase oxidation temperature.
The layer thickness of the reduced product on the mesh belt was set to 17 cm by the thickness adjusting plate. The reduced product moved in the direction of arrow A in FIG. 1 together with the belt and was continuously gas-phase oxidized while being in contact with the oxygen-containing gas flowing through the mesh belt. The residence time of the reduced product in the reaction furnace body was set to 9.0 hr by adjusting the traveling speed of the belt by a belt driving motor provided outside the reaction furnace body.

Under the above setting conditions, 5.8 kg / hr of metallic magnetic powder could be obtained in the treated material storage tank 62.
A part of this metal magnetic powder was extracted, and the VSM was used to measure the magnetic properties and the retention ratio of the saturation magnetization after standing for one week under the oxidation promoting condition of 60 ° C. and relative humidity of 90%. Further, the X-ray crystal grain size (size of crystallite of metallic iron) was measured by an X-ray diffractometer. At this time, the X-ray crystal grain size was obtained from the half-width of the iron (110) diffraction peak of X-ray diffraction using the Scherrer's formula. As a result, coercive force (Hc): 1565
[Oe], saturation magnetization (σs): 128 [emu / g],
The squareness ratio (σr / σs) was 0.52 [−], the saturation magnetization retention rate was 82 [%], the X-ray crystal grain size was 165 [A], and the magnetic properties were excellent. .

Example 4 (Production Example) As a raw material, needle-like α-FOOH containing Si in an amount of 3% by weight with respect to Fe and having a primary particle size having a major axis length of 0.25 μm and an axial ratio of 10. A granulated product having a weight average particle diameter of 3 mm by extrusion granulation was used. By using the manufacturing apparatus shown in Example 2 (see FIGS. 1 to 3 and 5), the steps (a), (b), and (c) were sequentially performed under the following conditions.

[Step (a)] The gas linear velocity of nitrogen gas is set to 8
cm / sec, and the feed rate of the above granules is 6.5 kg
/ Hr and the layer thickness of the granulated product was 10 cm,
The step (a) was performed under the same conditions as in Example 3. As a result, 5.8 kg / hr of heated dehydrated product was obtained in the treated product storage tank 56. The heated dehydrated product was continuously supplied into the object storage tank 57 by automatically opening and closing the powder supply valve 63.

[Step (b)] The heating reduction temperature is 500 ° C., the gas linear velocity of hydrogen gas is 40 cm / sec, the supply rate of the heated dehydration product is 5.8 kg / hr, and the layer thickness of the heated dehydration product is The step (b) was performed under the same conditions as in Example 3 except that was set to 9 cm. As a result, the processed material storage tank 5
4.1 kg / hr of the reduced product was obtained in 9. The reduced material was continuously supplied into the object storage tank 60 by automatically opening and closing the powder supply valve 64. The magnetic properties of this reduced product were measured in the same manner as in Example 3, and the coercive force (Hc): 15
80 [Oe], saturation magnetization (σs): 146 [emu /
g] and the squareness ratio (σr / σs): 0.51 [−].

[Step (c)] The feed rate of the reduced product is 4.1 kg / hr, the layer thickness of the reduced product is 9 cm,
The step (c) was performed under the same conditions as in Example 3 except that the residence time of the reduced product in the reaction furnace body was set to 6.0 hr. As a result, 4.5 kg / hr of metallic magnetic powder could be obtained in the treated material storage tank 62. The magnetic properties of this metal magnetic powder are as follows: coercive force (Hc): 1545 [Oe], saturation magnetization (σ
s): 131 [emu / g], squareness ratio (σr / σs):
The magnetic properties were 0.51 [-], the saturation magnetization retention rate: 82 [%], and the X-ray crystal grain size: 161 [A], which had excellent magnetic properties.

[0057]

EFFECTS OF THE INVENTION By using the production method and production apparatus of the present invention, the object to be treated can be subjected to heat dehydration, heat reduction, and heat vapor oxidation in a substantially stationary state on the belt. It is possible to produce a metallic magnetic powder that does not generate fine powder, has good contact between the object to be treated and gas, and has uniform magnetic properties. Further, it becomes possible to continuously produce such a high-quality metal magnetic powder industrially advantageously.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a gas flow type reaction furnace according to the present invention.

FIG. 2 is a sectional view taken along line II-II of the gas flow reactor of FIG.

3 is a cross-sectional view of the gas flow reactor of FIG. 1 taken along the line I-I.

FIG. 4 is a schematic explanatory view of a gas flow type reaction furnace according to the present invention.

FIG. 5 is a schematic explanatory view of an example of a manufacturing apparatus of the present invention.

[Explanation of symbols]

 1 Reactor Main Body 2 Gas Dispersion Plate 3 Belt 4 Electric Heater 5 Heat Insulating Material 6 Gas Inlet 7 Gas Outlet 8 Gas Supply Port 9 Treated Product Discharge Port 9 Treated Product Discharge Port 10 Thickness Adjustment Plate 11 Belt Drive Roller 12 Roller Drive shaft 13 Powder feeder 14 Treated material storage tank 15 Treated material storage tank 16 Nitrogen purge gas inlet 17 Nitrogen purge gas outlet 18 Nitrogen purge gas inlet 19 Nitrogen purge gas outlet 20 Shaft seal 21 Drive motor 22 Gas seal wall 40 Reactor body 41 Belt conveyor 42 Gas Dispersion Plate 43 Heating Means 44 Gas Inlet 45 Gas Outlet 46 Supply Port for Treated Product 47 Discharge Port for Treated Product 51 Heated Dehydration Reactor 52 Heated Reduction Reactor 53 Heated Gas Phase Oxidation Reactor 54 Treated Object ( Raw material granulated product) Storage tank 55 Powder feeder 56 Treated product (heated dehydrated product) storage tank 5 Treated (heated dehydrated) storage tank 58 Powder feeder 59 Treated (reduced) storage tank 60 Treated (reduced) storage tank 61 Powder feeder 62 Treated (product) storage tank 63 Powder supply valve 64 Powder supply Valve 65 Inlet for non-reducing gas 66 Outlet for non-reducing gas 67 Inlet for reducing gas 68 Outlet for reducing gas 69 Inlet for oxygen-containing gas 70 Outlet for oxygen-containing gas 71 For processed material (raw granules) Supply port 72 Treatment product (heating dehydration product) discharge port 73 Treatment target (heating dehydration product) supply port 74 Treatment product (reducing product) discharge port 75 Treatment target (reducing product) supply port 76 Treatment product ( Product) outlet 77 Nitrogen purge gas inlet 78 Nitrogen purge gas outlet

Claims (2)

[Claims] 1. A gas flow type having an iron compound powder mainly containing hydrous iron oxide as a granulation product having a weight average particle size of 1 to 20 mm, and having a belt through which the granulation product can flow as a gas. A method for producing a magnetic metal powder containing metallic iron as a main component, which comprises performing the following processes (a) to (c) using a reaction furnace. (A) A step of continuously supplying and placing the granulated product on a belt and carrying out a heat dehydration treatment with a non-reducing gas while transferring the granulated product to obtain a heated dehydrated product continuously. , (B) the heated dehydrated product obtained in step (a) is continuously supplied and placed on a belt, and while the heated dehydrated product is being transferred, a heating reduction treatment is performed with a reducing gas to obtain a reduced product. Continuously, and (c)
The reduced product obtained in the step (b) is continuously supplied and placed on a belt, and while the reduced product is being transferred, a heating vapor phase oxidation treatment is performed with an oxygen-containing gas to make metallic iron the main component. A step of continuously obtaining a magnetic metal powder, 2. A heating dehydration reaction furnace for heating and dehydrating a granulated product of an iron compound powder mainly containing iron oxide hydroxide, a heating reduction reaction furnace for heating and reducing the heated dehydration product obtained from the reaction furnace, and the reaction. An apparatus for producing a magnetic metal powder, comprising a heating vapor-phase oxidation reaction furnace for heating a gas-phase oxidation of a reduction product obtained from the furnace, wherein these reaction furnaces are heated and dehydrated at least through a powder transport means. , A heating reduction reaction furnace, and a heating gas-phase oxidation reaction furnace are connected in series in this order, and each reaction furnace has a gas inlet and a gas outlet, and a supply port and a discharge port for the object to be treated. A main body, a belt conveyor for transferring a processed material having a belt through which a gas can flow provided in the main body of the reaction furnace, and a gas introduced from an inlet of the gas is uniformly applied to the belt surface on which the processed object is placed. Gas to be distributed and supplied to An apparatus for producing metal magnetic powder, which is a gas flow type reaction furnace comprising a dispersion plate and a heating means arranged to heat the inside of the reaction furnace body.