JPH02301503A - Method and apparatus for manufacturing metal powder - Google Patents

Abstract

PURPOSE:To manufacture granular fine metal powder having good quality and good shape at a low cost by substituting iron powder for the metal powder from metal acid salt water solution, precipitating, dewatering and drying after circulating a pressurized filtering chamber while adding water to the above slurry. CONSTITUTION:The fine iron powder obtd. with a wet type pulverizer 1 is charged into a reaction vessel 2, where, the acid salt water solution of the metal having less ionization tendency than iron is brought into contact with the above iron powder to substitute the iron powder for the above metal powder and precipitate it. successively, water is added to the slurry formed therein and while stirring this is passed through a continuous type filtration device 6 through a pump 5 and circulated through circulating passage 3. By this method, the water is substituted for the solution generated with the above reaction. Successively, the water slurry of the metal powder obtd. with this method is moved to centrifugal separator 7 and dewatered. After that, the dewatered metal powder is charged into a stirring type reduced pressure dryer 8. Then, this dryer is made under inert gas atmosphere from an inlet hole 36 and heated through a jacket 30 and while reducing the pressure with a vacuum pump 33, the metal powder is stirred with stirring blades 32 and dried. After that, the dried powder is cooled and pulverized with a pulverizer 40 to obtain the granular primary grain- shaped metal powder having fine particles and low oxidation degree.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for producing various granular fine metal powders from iron powder by utilizing its ionization tendency.

[Background technology of the invention]

There are many methods for producing fine metal powder for powder metallurgy.

The most commonly used methods for producing raw material powder for powder metallurgy are electrolysis, reduction, and mechanical pulverization. Powders are also often produced by combining these.

As one of the reduction methods, a reducing agent is placed in a metal salt aqueous solution,
A reducing agent? A method is known in which powder of the metal is precipitated at the same time as the metal is dissolved. In this case, the reducing agent used is an organic reducing agent, an inorganic reducing agent, metal powder, or the like.

The inventors have already filed patent applications in 1982-29 for a method for manufacturing fine granular metal powder and a method for manufacturing fine granular alloy powder using iron powder as a reducing agent and utilizing the ionization tendency of metals.
No. 3144 and Japanese Patent Application No. 62-297701. The gist of this is that the particle size is 0.1 to 3.0μ.
After putting iron powder with a specific surface area of 2.0 to 4.0 m'/H into a wet crusher (e.g., Attritor manufactured by Mitsui Miike Kakoki ■) and making it into a slurry, it was added to a metal salt aqueous solution in a reaction tank. The resulting mixed slurry of metal powder and iron salt is washed by repeating stirring, standing, and decantation until the iron ion concentration in the slurry is below 0.1 g/L, and then the slurry is washed. filtered with a filter press,
Metal powder is obtained by drying with an in-type vacuum dryer.

That is, in order to collect the metal powder from the mixed slurry of raw gold X@ powder and iron salt, a procedure was adopted in which the mixed slurry was replaced with mother liquor by decantation and then washed.

[Problem that the invention seeks to solve]

-a, the operation of replacing the mother liquor in the slurry and washing the powder is carried out by passing a predetermined amount of washing water from one side of the cake layer formed in the dehydrator to the other side. is normal. However, in the case of fine metal powders such as 01 to 3.0 .mu.m, even if this method is used, the cleaning effect will not be improved very much even if a large amount of water is used due to distortion of the cleaning water flow in the cake layer, short circuits, etc. Therefore, in order to perform reliable cleaning, it is necessary to use a mixed slurry of metal powder and iron salt.
It is considered best to repeat dehydration and dilution and dispersion. However, if it is too concentrated, it may be difficult to uniformly disperse the metal powder again.

On the other hand, when displacing the mother liquor by decantation as described above, if the particle size of the metal powder is as small as 0.1 to 3.0 μm, the sedimentation rate is slow, so the residence time is 30 μm per time.
It is necessary to take a long time of ~40 minutes. Therefore, in order to reduce the iron salt concentration in the mother liquor to 0.1 g/L or less, the washing time is extremely long. Furthermore, when the supernatant liquid is removed using a pump, powder is also sucked up, reducing the recovery rate. Furthermore, there was also the problem that the amount of waste liquid increased due to insufficient condensation and dehydration of the mixed slurry.

Furthermore, when dehydrating metal powder using a filter press, if the metal powder is fine and has a large specific surface area and is easily oxidized, the filter cloth and filter plate must be removed each time after filtration.
It needs to be cleaned and is very time consuming. As the number of filter cloths and filter plates increases, the amount of waste liquid due to cleaning increases, and the loss due to adhesion of metal powder also increases.

On the other hand, when it comes to drying the fine metal powders that have been washed in this way, it is important to note that the metal powders are thermally sensitive and unstable, and are prone to quality deterioration due to changes over time. Due to reasons such as the need to remove the cake from the cake in a short time and at a low temperature, it is necessary to perform reduced pressure drying under vacuum. Conventional so-called shelf wall vacuum dryers separate different types of metal powder into columns. It is ideal for drying, but since it dries the cake in a stationary state,
There was a problem that the cake was separated from the heat transfer surface and the heat resistance between individual particles of the metal powder was large (and the heat transfer efficiency was extremely poor. Therefore, it took 3 to 4 days for the metal powder to dry. It was also decided that

Furthermore, the heating and cooling mechanism of the main body of the dryer uses electric heating for natural cooling, so it takes one day to cool the dryer to room temperature.

In addition to the problem that drying a large amount of metal powder requires a very large area, there is also the problem that metal powder dried in a shelf-wall vacuum dryer will aggregate into lumps, and hammer mills, etc. This required post-processing such as crushing. that time.

Oxidation occurs due to heat generation of metal powder, and countermeasures such as replacing the inside of the hammer mill with nitrogen to suppress oxidation were required.

In this method for producing fine metal powder, fine reduced iron powder with a particle diameter of 0.1 to 3.0 μm is used as a reducing agent, and fine metal powder of approximately the same diameter is precipitated by displacement from a metal salt solution. There are still many problems, especially in the filtration, washing and drying of the mother liquor, and it is difficult to obtain high-quality granular fine metal powders with low residual iron salts, low degree of surface oxidation, and a morphology similar to primary particles at low prices. There were problems in manufacturing.

[Means for solving problems]

The present invention uses fine iron powder with a grain size of 0.1 to 3.0 μm, especially reduced iron powder with a specific surface area of 2.0 to 4.0 m''/g, as a reducing agent, to reduce the ionization tendency of iron. The following method is provided for producing fine metal powder by displacement precipitating a small metal powder from an acidic salt solution as a powder having approximately the same particle size distribution as the iron powder used.

That is, a step in which iron powder is brought into contact with an acidic salt aqueous solution of a metal that has a smaller ionization tendency than iron to precipitate the metal powder by displacement, a step in which the post-reaction liquid produced in this step is replaced with water, and this step 1. A method for producing metal powder, which comprises the steps of dehydrating the water slurry of metal powder obtained in step 1 and then drying the dehydrated metal powder under reduced pressure.

One of its features is 1. When carrying out the above-mentioned step of replacing the post-reaction liquid with water, the slurry in the reaction vessel in which the metal powder precipitated by displacement is suspended is transferred from the reaction vessel to a pressurized filtration chamber equipped with stirring blades. The slurry that has passed through the pressurized filtration chamber is circulated again into the reaction vessel, the filtrate is separated and removed from the pressurized filtration chamber, and water is supplied to the circulation system. The process should be carried out until the after-liquid is substantially replaced with water.

Another feature is that the process of dewatering the water slurry of metal powder is carried out using a basket centrifuge;
There is.

Another feature is the vacuum drying process.

The dehydrated cake of metal powder is loaded into a vacuum container equipped with a stirring R and a jacket on the circumference that allows switching between heating and cooling media to circulate, and then! A. Perform the operation under heating with a heating medium and stirring under reduced pressure. 9. Then, perform the operation of cooling with a cooling medium.

It is in.

As an apparatus for carrying out this method advantageously, the present invention includes a wet crusher for obtaining an aqueous slurry of iron powder, and an acid salt solution of iron powder and metal. 8 liquid under stirring, a pump and a continuous filtration device interposed in a slurry circulation path for returning the slurry in the reaction container to the reaction container, and a slurry in the circulation path. The present invention provides an apparatus for producing metal powder, which comprises a centrifugal bone N machine that receives and dehydrates the same, and an agitating vacuum dryer that dries the dehydrated cake dehydrated in the centrifuge under vacuum heating.

[Effect] One feature of the method for producing metal powder of the present invention is as follows.

Washing of the mixed slurry of metal powder and iron salt 8, that is, the operation of separating the post-reaction liquid from the slurry in which the metal powder is suspended in the post-reaction liquid and replacing it with water, is carried out by continuous pressure filtration and washing. That is, the slurry in the reaction vessel, which is cloudy with the metal powder precipitated by displacement, is continuously pumped from this reaction vessel to a pressure filtration chamber equipped with a stirring blade, and the slurry that has passed through this pressure filtration chamber is returned to the reaction vessel. Along with circulating it in the container,
In the pressurized filtration chamber, the filtrate is separated and water is supplied to the circulation system until the post-reaction liquid is substantially replaced with water. The problem with the decantation method mentioned above was solved by repeating the process continuously in a short period of time.

In ordinary static pressure filtration, the cake layer formed on the filtration surface grows with the filtration time, so the filtration rate is d! It continues to decrease inversely over time and must be removed mechanically after the cake reaches a certain thickness.

Therefore, this method necessitates discontinuous filtration due to wood quality. In the present invention, the mixed slurry in the 9 reaction vessels is continuously supplied to a pressurized filtration chamber equipped with stirring blades to separate the filtrate,
By repeating the cycle of returning the slurry to the reaction vessel (while continuing to add an appropriate amount of water to the circulation system), the solid particles deposited on the filtration surface in the pressurized filtration chamber are peeled off by the sweeping effect. The slurry is resuspended in the slurry, and the slurry is concentrated there, and the cake layer does not grow beyond that thickness.Therefore, high efficiency, constant pressure, constant speed filtration proceeds, and it is necessary to take residence time like in decantation. Since there is no water, cleaning can be completed in a short time. As a result, cleaning of the slurry is completed in approximately 115 hours compared to the case where decantation and static pressure filtration are performed. In addition, the concentrated slurry in the pressure filtration chamber returns to the reaction tank while maintaining fluidity until it reaches a high concentration due to its thixotropy and stirring action, so redispersion is very easy and problems such as aggregation occur. Since the concentration is about twice that of decantation, the amount of waste liquid is also about half.

Another feature of the metal powder production method of the present invention is that the slurry in which metal powder is suspended in water obtained in the previous step is dehydrated by basket centrifugation (e.g., basket type vertical centrifuge). This method does not use a filter press, etc., as in the past.As a result, the amount of loss due to adhesion is reduced by the amount of excess area, and compared to the case of a filter press, the cleaning time of the machine is also reduced. /
10 or less, and the amount of cleaning waste liquid is also reduced accordingly.

Furthermore, the centrifugal force of the centrifuge can reduce the water content of the metal powder cake by more than 10 wt.% to about 25 wt.chi, thereby reducing the overall manufacturing cost.

Another feature of the metal powder manufacturing method of the present invention is that the conventional shelf-type vacuum dryer is replaced with an Fft stirring type vacuum dryer, which greatly shortens the drying time and The shape of the powder became close to that of primary particles (the shape of the iron powder used). This is because the metal powder is constantly mixed by the rotation of the agitating blades installed on the internal bottom of the agitating vacuum dryer, and the heat transfer surface is updated while equalizing the moisture inside the container, resulting in efficient heat transfer. This is because there is. For example, weight 7
When drying a metal powder cake weighing 8 kg and having a moisture content of 30%, drying is completed in about 7 hours, including the cooling time of the dryer. This is extremely fast considering that conventional vacuum dryers require 3 to 4 days. In addition, water in the metal powder cake during drying is removed after removing the entrained metal with a filter bag.
Since only the water can be recovered as a concentrated liquid in the condenser, even if fine metal powder is thrown up along with the water due to stirring, it can be prevented from reaching the vacuum pump and damaging the pump. In addition to the stirring blades, a screw-rotating type crusher can also be installed, so that even if the metal powder aggregates into lumps during drying, the crusher can break the agglomeration. This can shorten the drying time, and if the crusher is operated while mixing at the end of drying, metal powder in the form of coarse particles can be collected. Therefore, there is no need to crush metal powder agglomerates again using a hammer mill, etc., which not only prevents quality deterioration due to oxidation of metal powder caused by heat generated during crushing, but also reduces work time by omitting the crushing process. It becomes possible. Furthermore, the powder can be easily discharged by using a stirring blade, and packaging is also facilitated.

In this way, according to the present invention, 7-grain fine metal powder can be produced economically in a short time, and its quality is close to that of primary particles.
It becomes a good powder with a low degree of oxidation.

Note that the metal powder that can be produced according to the present invention may be of any type as long as it has a smaller ionization tendency than iron, but specifically, powders of copper, nickel, cobalt, lead, tin silver, etc. are produced. It is advantageous for Furthermore, if a composite solution containing acid salts of multiple types of metals having a smaller ionization tendency than iron is used as the reaction solution, alloy powders of the metals can also be produced.

[Preferred embodiment of the invention]

FIG. 1 systematically shows an example of an apparatus for implementing the present invention.

As shown in the figure, the entire device consists of a wet crusher l for obtaining an aqueous slurry of iron powder, a reaction vessel 2 for reacting the iron powder with an aqueous metal acid salt solution under stirring, and this reaction vessel. a pump 5 and a continuous filtration device 6 installed in the slurry circulation path 3 for returning the slurry in the reaction vessel 2 to the reaction vessel 2; a centrifugal separator 7 for receiving the slurry in the circulation path 3 and dewatering it; It consists of a stirring type vacuum dryer 8 that dries the dehydrated cake dehydrated in the centrifugal separator 7 under vacuum heating.

The wet crusher 1 is a normal aggregate crusher having crushing blades 10, and water and iron powder are put therein and stirred to obtain an iron powder-water slurry. This slurry is transported to the reaction vessel 2 by a slurry pump 11. Y! In the type crusher 1, it is preferable that the slurry has an iron powder concentration of about 50%.

The reaction vessel 2 is a normal reaction vessel equipped with a stirring blade 12, and is equipped with a slurry outlet 13 at the bottom, and an iron powder slurry supply port 14 from the wet crusher 1 described above. Water supply port 15. and a slurry return port 16 at the top.

In this reaction vessel 2, a step is carried out in which iron powder is brought into contact with an aqueous acidic salt solution of a metal having a smaller ionization tendency than iron to precipitate the metal powder by displacement. Here, the acid salt aqueous solution of the metal is 2, for example, copper, nickel, cobalt,
This refers to chlorides, disulfates, nitrates, etc. of metals that have a smaller ionization tendency than iron, such as lead, tin, and silver, and chlorides are preferable.To make this metal ion-containing solution, add commercially available chlorides as they are to water. dissolve. Dissolve the oxide with hydrochloric acid. A suitable method is dissolution by anodic electrolysis in an aqueous hydrochloric acid solution. on the other hand,
The iron powder used is preferably fine reduced iron powder with a grain size of about 0.1 to 3.0 ttm. In order to disperse such fine iron powder, it is suitable to use the above-mentioned wet crushing Jal. When such fine iron powder is sufficiently dispersed, metal powder equivalent to the iron powder is precipitated by displacement from an aqueous solution of an acid salt of the metal.

All of the iron powder is dissolved into an aqueous ferrous salt solution, and iron remains as a nucleus in the precipitated metal powder. In this displacement precipitation reaction of metal powder, the higher the temperature, the lower the acid salt concentration.

The faster the iron powder addition rate and the stronger the stirring, the more fine the metal powder tends to precipitate by displacement, but the larger the primary particle size of the iron powder used, the larger the particle size of the precipitated metal powder becomes. The speed will also be slower. Because of this, 5
Particle size is 0.1-3.0μm and specific surface area is 2.0-4.0
It is advantageous to use reduced iron powder of m''/g, in which case one reaction is generally completed in 10 to 15 minutes.

After this displacement precipitation reaction is completed, the first step is to add the post-reaction solution in the slurry in which the metal powder, which is the reactant, is suspended in the solution (8 liquids of water in which the ferrous salt is dissolved and further unreacted metal salts are dissolved). ) is replaced with pure water. This is circulation path 3
This is carried out by a forced Wi cycle of the suspension in which a pump is driven to continuously pump the suspension in the two reaction vessels to the continuous filtration device 6 and return it to the reaction vessel 2 again.

The continuous filtration device 6 used for this has a rotating shaft 18 at the center.
and a fluid inlet 19 at one end and a fluid outlet 2 at the other end.
In the cylindrical container 21 containing 0, ? 3i Several filter plates 22 are arranged with gaps in the direction orthogonal to the axis, and the stirring blades 23 are rotated in the gaps between the filter plates 22.
This is the device attached to 8. In the illustrated example, each ill
The temporary 22 has a hollow disk shape. i.e. 1
It has a hollow disk shape with an opening in the center that has an inner diameter sufficiently larger than the outer diameter of the rotating shaft in one day, and an internal space for leaching the d# liquid inside. is entirely composed of a filter medium, and its outer periphery is hermetically joined to the inner surface of the cylindrical container 21. In addition, each stirring blade 23 is a disk that rotates in the center of the gap between each hollow disk-shaped filter plate 22, and its center is fixed to the rotating shaft 18, and its radius is larger than the inner diameter of the cylindrical container 21. It is also small. With this configuration, the slurry introduced from the fluid inlet port 19 at one end hits the stirring blade 23, moves in a zigzag pattern between the stirring blade 23 and the filter plate 22, and receives resistance due to the rotation of the stirring R23, while the other fluid is introduced. We will be moving towards exit 20! A large pressure is applied to the overplate 22 under flowing conditions. therefore,
Il! While the lil liquid is filtered into the internal space of the filter plate 22, the metal powder that accumulates on the outer surface of the filter plate 22 is prevented from increasing in layer thickness by the stirring blades 23, and the peeled part is recycled again. The liquid becomes a fluid and flows toward the fluid outlet 20. At this time, the slurry concentration increases as the filtrate is separated, but the slurry is forcibly moved by the hydraulic pressure applied by the pump 5 and the rotational power of the stirring blades 23. The apparatus is constructed with a pressure-resistant structure so that such pressurized continuous filtration can be realized, and the pump 5 used has a discharge pressure of 2 to 5 kg/cm''.

The filtrate filtered inside the filter plate 22 is continuously discharged outside the system as waste liquid, passes through this continuous filtration device 6, and the slurry that has become highly concentrated is returned to the reaction vessel 2. If you continue, the slurry concentration will increase for a while, and Wi
Water may be introduced into the system as appropriate to prevent damage to the ring. This is done by supplying water into the reaction vessel 2 from the water supply port 15 of the reaction vessel 2. In this way, as the slurry continues to circulate between the reaction vessel 2 and the filtration device 6 while discharging 1lte out of the system and introducing water into the system, the slurry gradually becomes The post-reaction liquid is almost replaced with water. In practice, by carrying out this continuous circulation operation for about one hour, it is possible to finally obtain water with an iron salt concentration of 0.1 g/L or less, p) 15.0 or more, and preferably neutral water. .

After the replacement of the post-reaction liquid with water has been completed and the metal powder has been sufficiently washed, the first step is to add water from the powder rI4#9J to the branch path 25 branched from the middle of the I# ring path 3. The slurry is extracted by opening the valve 26 installed in the two branch passages 25 and driving the pump 4 installed in the first branch passage 25. 3) The water slurry of metal powder flowing out from this branching path 25 is supplied to the centrifuge 7. This centrifugal separator 7 performs a dehydration process.

The centrifugal separator 67 is a basket-type vertical centrifuge, and uses a basket 27 (made of a filter medium) with an opening at the top that rotates around a vertical shaft 28 . By putting the aqueous slurry of metal powder into this basket 27 and applying a centrifugal force of about 400 G, it can be easily dehydrated to a metal powder cake with a moisture content of 25 to 30%. This dehydrated cake is first transferred to a stirring type vacuum dryer 8, where a step of drying under vacuum is carried out.

This stirring type vacuum dryer 8 is equipped with stirring blades 32 in a vertical cylindrical container 31 having a jacket 30 on one circumference for passing a heat medium, and an exhaust port 34 communicating with a vacuum pump 33.
A filtration bag 35 is attached to the container, and a gas inlet 36 is provided for injecting inert gas into the container.

A powder discharge port 37 is provided for discharging the powder out of the container while being isolated from the surrounding atmosphere. Jagento 30
A heating medium such as hot water or water is introduced during the drying process, and a cooling medium such as cold water is introduced after the drying process is completed. The metal powder cake that has completed the previous process is introduced by opening the lid body 42 with a jacket 30'', and after closing the 1M body 42, the vacuum pump 33 is driven to exhaust the heat medium. ° to raise the temperature inside the container, and rotate the stirring blade 32 to dry the cake.By this operation of reducing the pressure, increasing the temperature, and stirring, the cake is dissolved and dried well.At this time, the metal powder The moisture in the cake is transferred to the exhaust gas, and the entrained metal is removed from this exhaust gas by a filter bag 35, and the moisture in the exhausted exhaust gas is recovered as a condensate by a condenser 39.

This prevents failure of the vacuum pump due to fine metal powder or moisture.

In addition, this vacuum dryer has a screw rotary crusher with 8!4
0 is attached, and by lowering the crushing blade 141 appropriately, even if the metal powder aggregates into lumps during stirring by the stirring blade 32, the agglomerated lumps will not come into contact with the tip of the coughing blade 41 during the stirring. This is then broken down and a good dispersion state is maintained. This can prevent the drying time from becoming longer and the agglomerates from becoming larger. At the end of drying, the heating medium flowing at 30°30' was changed to water to cool the entire container.

The metal powder is cooled to room temperature in a short period of time, and then nitrogen gas, for example, is introduced into the container from the inert gas inlet 36, and after returning to normal pressure, the stirring blade 32 continues to rotate to stir the metal powder. At the same time, the crusher 40 is also driven for a predetermined time (for example, about 0.5 to 1.0 hours).

As a result, it is possible to obtain a metal powder in the state of primary particles (fine particles close to the form of the iron powder used) which is precipitated by displacement in the reaction vessel 2. The metal powder is discharged from the dryer by rotating the stirring blades 32 in the opposite direction through the powder discharge port 37.
If the container is fully opened, it can be discharged naturally, and the treatment can be completed by putting it into a packaging bag, for example.

As described above, according to the present invention, extremely fine granular metal powder can be produced in the form of primary particles and in a state with a low degree of oxidation, and the series of steps of filtration, washing, water, and drying after displacement precipitation can be approximately performed. It can be automated, and metal powder with stable quality can be economically produced by shortening processing time and simplifying operations. As a result, 1. not only the normal powder metallurgy field, but also
Conductive material, porous electrode material, catalyst, magnetic material f-1. Now more than ever, we look forward to contributing to new fields such as injection molding materials.

[Brief explanation of drawings]

FIG. 1 is an equipment layout system diagram showing an embodiment of an apparatus for carrying out the present invention. 1. Big brother type crusher, 2. Reaction vessel. 3. Slurry Wi ring path, 5. Circulation pump. 6. Continuous filtration device, 7. Centrifugal separator. 8. Stirring type vacuum dryer @ machine, 18. Rotating shaft. 22... Filter plate, 23... Stirring blade of the filtration device. 32...Dryer stirring blade, 33...Vacuum pump. 35...Filtering bag, 36...Inert gas inlet. 37...Powder discharge port, 40...Screw rotary crusher.

Claims (7)

[Claims] (1) A step in which iron powder is brought into contact with an acidic salt aqueous solution of a metal that has a smaller ionization tendency than iron to precipitate the metal powder by displacement, and a step in which the post-reaction liquid produced in this step is replaced with water; A method for producing metal powder, comprising the steps of dehydrating a water slurry of metal powder obtained in the step, and then drying the dehydrated metal powder under reduced pressure, the step of replacing the post-reaction liquid with water. In carrying out this process, the slurry in the reaction vessel in which the metal powder precipitated by displacement is suspended is continuously pumped from this reaction vessel to a pressurized filtration chamber equipped with stirring blades, and the slurry that has passed through this pressurized filtration chamber is The filtrate is circulated again to the reaction vessel, the filtrate is separated and removed in the pressurized filtration chamber, and water is supplied to the circulation system, which are carried out until the post-reaction liquid is substantially replaced with water. A method for producing metal powder. (2) A pressurized filtration chamber with stirring blades is a cylindrical filtration chamber with a fluid inlet at one end and a fluid outlet at the other end, and a large number of filtration plates spaced apart from each other in a direction perpendicular to its axis. 2. The method for producing metal powder according to claim 1, wherein the filtration device is arranged with a gap between the filter plates and a stirring blade arranged in the gap between the filter plates. (3) A step in which iron powder is brought into contact with an acidic salt aqueous solution of a metal that has a smaller ionization tendency than iron to precipitate the metal powder by displacement, and a step in which the post-reaction liquid produced in this step is replaced with water; A method for producing metal powder comprising the steps of dehydrating a water slurry of metal powder obtained in the process and then drying the dehydrated metal powder under reduced pressure, the step of dewatering the water slurry of metal powder being a basket. 1. A method for producing metal powder, characterized in that it is carried out using a centrifugal separator. (4) A step in which iron powder is brought into contact with an acidic salt aqueous solution of a metal that has a smaller ionization tendency than iron to precipitate the metal powder by displacement, and a step in which the post-reaction liquid produced in this step is replaced with water; A method for producing metal powder comprising the steps of dehydrating an aqueous slurry of metal powder obtained in the process, and then drying the dehydrated metal powder under reduced pressure, the method comprising: drying the dehydrated metal powder under reduced pressure; The dehydrated cake of the metal powder is loaded into a reduced pressure container having a jacket on the circumference for switchable circulation of a cooling medium and a stirring blade, and the dehydration cake is carried out under heating with a heating medium and under reduced pressure stirring, Next, a method for producing metal powder comprising cooling with a cooling medium. (5) a wet crusher 1 for obtaining water slurry of iron powder;
A reaction vessel 2 for reacting iron powder and an aqueous metal acid salt solution with stirring, a pump 5 interposed in a slurry circulation path 3 for returning the slurry in the reaction vessel 2 to the reaction vessel 2, and a continuous a centrifugal separator 7 that receives the slurry in the circulation path 3 and dehydrates it, and an agitating vacuum dryer 8 that dries the dehydrated cake dehydrated in the centrifugal separator 7 under vacuum heating. Metal powder manufacturing equipment consisting of. (6) A continuous filtration device is a cylindrical container that has a rotating shaft at the center, a fluid inlet at one end, and a fluid outlet at the other end.
6. The metal device according to claim 5, wherein a plurality of filter plates are arranged with gaps in a direction perpendicular to the axis, and a stirring blade is attached to the rotating shaft so as to rotate in the gap between the filter plates. Powder manufacturing equipment. (7) A stirring type vacuum dryer is equipped with stirring blades inside a cylindrical container that has a jacket around its periphery that allows heat medium to pass through, and a filter bag is attached to the exhaust port leading to the vacuum pump, and the inside of the container is kept inert. 7. The metal powder manufacturing apparatus according to claim 6, further comprising a gas introduction port for replacing the powder with gas and a powder discharge port for discharging the powder out of the container while being isolated from the surrounding atmosphere.