JPH10219313A - Production of metal powder and production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and device for producing a metal powder by which the grain diameter is stabilized and optionally set in the range from 0.1 to 1.0μm. SOLUTION: Gaseous chlorine is brought into contact with metallic nickel to continuously generate a gaseous nickel oxide in the chlorination stage, and the gaseous metal chloride is brought into contact with a reducing gas to continuously reduce the metal chloride in the reducing stage. Since both stages are provided, the amt. of the gaseous metal chloride to be generated is controlled by controlling the supply of gaseous chlorine, and the grain diameter of the metal powder generated is surely controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a method for producing a metal powder such as Ni, Cu or Ag suitable for various uses such as a conductive paste filler used for electronic parts, a joining material of a Ti material, and a catalyst. Related to the device.

[0002]

2. Description of the Related Art Conductive metal powders such as Ni, Cu, and Ag are useful for forming internal electrodes of a multilayer ceramic capacitor. In particular, Ni powder has recently attracted attention as such an application. Among them, Ni ultrafine powder produced by a dry production method is promising. Due to the demand for thinner and lower resistance internal electrodes with the miniaturization and large capacity of capacitors, the particle diameter is not more than 1 μm,
There is a demand for ultrafine powder having a size of less than μm.

Conventionally, various production methods for producing the above metal powder have been proposed. For example, Japanese Patent Publication No. 59-7765 discloses a method in which solid nickel chloride is heated and evaporated to form nickel chloride vapor, and hydrogen gas is sprayed at a high speed to grow nuclei in an unstable interface region. Japanese Patent Application Laid-Open No. 4-365806 discloses a nickel chloride vapor (hereinafter, referred to as N) obtained by evaporating solid nickel chloride.
iCl ₂ gas) is 0.05-0.3,
A method for gas phase reduction at 1004 ° C. to 1453 ° C. is disclosed. According to these manufacturing methods, it is said that spherical Ni ultrafine powder having an average particle diameter of 0.1 to several μm is generated.

[0004]

However, in the method for producing metal powder according to the above proposal, since solid nickel chloride is used as a starting material, there are the following essential problems. Since the operation of heating and evaporating (sublimating) solid NiCl ₂ is essential, it is difficult to stably generate steam. As a result, the partial pressure of the NiCl ₂ gas fluctuates, and the particle size of the generated Ni powder becomes unstable. If the amount of solid NiCl ₂ in the evaporating section fluctuates during the operation of the process, the evaporation rate fluctuates, and stable production cannot be performed. Since solid NiCl ₂ has water of crystallization, not only is dehydration required before use, but insufficient dehydration causes oxygen contamination of the generated Ni powder. Since the evaporation rate of solid NiCl ₂ is slow, a large amount of carrier gas (inert gas such as nitrogen gas) is required for transferring the NiCl ₂ gas to the reduction step, and unnecessary heating for heating nitrogen gas or the like is required. Requires energy. Therefore, the concentration (partial pressure) of the NiCl ₂ gas in the reduction step cannot be increased, so that not only the production speed of the Ni powder is low, but also a large reaction vessel is required.

Accordingly, the present invention has been made in view of the above circumstances, and is a method and an apparatus for producing metal powder, which can achieve the following objects. 1) A powder (ultrafine powder) such as Ni, Cu or Ag having an average particle size of 0.1 to 1.0 μm is stably manufactured. 2) There is no heating evaporation (sublimation) step, and the reaction is easily controlled. 3) The whole process can be controlled by the gas flow rate, and a metal powder having a desired particle size is arbitrarily manufactured. 4) Low consumption of gas and energy.

[0006]

SUMMARY OF THE INVENTION A method for producing a metal powder according to the present invention comprises: a step of continuously generating a metal chloride gas by contacting a metal with a chlorine gas; And a reducing step of continuously reducing metal chlorides by contacting with a reducing gas.

In the process of producing metal powder by a gas phase reaction,
At the moment when the metal chloride gas comes into contact with the reducing gas, metal atoms are generated, and the metal atoms collide and agglomerate to generate ultrafine particles and grow. The particle size of the generated metal powder is determined by conditions such as the partial pressure and temperature of the metal chloride gas in the atmosphere of the reduction step. According to the method for producing a metal powder of the present invention, since an amount of metal chloride gas is generated according to the supply amount of chlorine gas, the amount of metal chloride gas supplied to the reduction step by controlling the supply amount of chlorine gas Can be controlled. Further, since the metal chloride gas is generated by the reaction between the chlorine gas and the metal, unlike the method of generating the metal chloride gas by heating and evaporating the solid metal chloride, the use of the carrier gas can be reduced. Alternatively, it may not be used depending on the manufacturing conditions. Therefore, the manufacturing cost can be reduced by reducing the amount of carrier gas used and the resulting reduction in heating energy.

Further, by mixing an inert gas with the metal chloride gas generated in the chlorination step, the partial pressure of the metal chloride gas in the reduction step can be controlled. Thus, by controlling the supply amount of the chlorine gas or the partial pressure of the metal chloride gas supplied to the reduction step, the particle diameter of the metal powder can be controlled, and the particle diameter of the metal powder can be stabilized. In addition, the particle size can be arbitrarily set.

The apparatus for producing metal powder of the present invention includes a chlorination furnace for chlorinating the metal charged therein and a reduction furnace for reducing the metal chloride gas generated in the chlorination furnace. A raw material supply pipe for supplying metal to the inside,
A chlorine gas supply pipe for supplying chlorine gas inside, a transfer pipe for transferring the generated metal chloride gas to the reduction furnace, and an inert pipe for supplying an inert gas for diluting the metal chloride gas to the inside. A gas supply pipe, and the reduction furnace has a nozzle for ejecting metal chloride gas into the inside, a reducing gas supply pipe for supplying the reducing gas to the inside, and an inert gas for cooling the reduced metal powder. A cooling gas supply pipe for supplying gas to the inside, a chlorination furnace is disposed upstream of the reduction furnace,
By directly connecting the chlorination furnace and the reduction furnace, the chlorination reaction and the reduction reaction proceed simultaneously and continuously.

[0010] Also in the metal powder production apparatus having the above-described structure, the amount of metal chloride gas generated according to the supply amount of chlorine gas is generated, and the chlorine furnace and the reduction furnace are directly connected. By controlling the supply amount, the amount of the metal chloride gas supplied to the reduction furnace can be controlled. Also,
The chlorination furnace is provided with an inert gas supply pipe, from which an inert gas can be supplied to the chlorination furnace, so that the partial pressure of the metal chloride gas in the reduction furnace can be controlled. Therefore, in the metal powder production apparatus of the present invention, the particle size of the metal powder can be controlled by controlling the supply amount of the chlorine gas or the partial pressure of the metal chloride gas supplied to the reduction furnace. Can stabilize the particle size, and the same operation and effect as described above can be obtained, for example, the particle size can be set arbitrarily.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings based on examples of manufacturing Ni. A. Chlorination Step The chlorination step is preferably performed in a chlorination furnace 1 as shown in FIG. On the upper end surface of the chlorination furnace 1, a raw metal Ni (M)
The raw material supply pipe 11 for supplying the raw material is provided. Also,
A chlorine gas supply pipe 14 is connected to the upper part of the chlorination furnace 1,
An inert gas supply pipe 15 is connected to the lower side. A heating means 10 is arranged around the chlorination furnace 1, and a transfer pipe / nozzle 17 is connected to a lower end surface of the chlorination furnace 1. The chlorination furnace 1 may be a vertical type or a horizontal type, but a vertical type is preferable in order to perform a solid-gas contact reaction uniformly. The flow rate of the chlorine gas is measured and continuously introduced from the chlorine gas supply pipe 14. Chlorination furnace 1
And other members are preferably made of quartz glass. The transfer pipe / nozzle 17 is connected to the upper end surface of the reduction furnace 2 described below,
It has a function of transferring NiCl ₂ gas and the like generated in the chlorination furnace 1 to the reduction furnace 2. The lower end of the transfer pipe / nozzle 17 protrudes into the reduction furnace 2 and functions as a NiCl ₂ ejection nozzle. It is preferable to provide a net 16 as shown in FIG. 1 at the bottom of the chlorination furnace 1 and to deposit metal Ni (M) on the net 16.

Although the form of the metal Ni (M) as the starting material is not limited, from the viewpoint of contact efficiency and prevention of an increase in pressure loss, it is preferably in the form of granules, lumps, or plates having a particle size of about 5 mm to 20 mm. Is generally preferably 99.5% or more.
The height of the packed bed of metal Ni (M) in the chlorination furnace 1 is based on the chlorine supply speed, chlorination furnace temperature, continuous operation time, shape of the metal Ni (M), etc., and the supplied chlorine gas is converted into NiCl ₂ gas. What is necessary is just to set suitably in the range which is sufficient. The temperature in the chlorination furnace 1 is set to 800 ° C. or higher in order to sufficiently promote the reaction.
The temperature is 1483 ° C. or lower, which is the melting point of i. Considering the reaction rate and the durability of the chlorination furnace 1, practically 900 ° C. to 11 ° C.
A range of 00 ° C. is preferred.

In the method for producing a metal powder according to the present invention,
Continuous supply of chlorine gas to the chlorination furnace 1 filled with metallic nickel (M) results in continuous generation of NiCl ₂ gas.
Then, since the supply amount of chlorine gas controls the amount of generated NiCl ₂ gas, it controls a reduction reaction to be described later, and as a result, a target product Ni powder can be produced. The details of the chlorine gas supply will be described more specifically in the section of the reduction step below.

The NiCl ₂ gas generated in the chlorination step is transferred as it is to the reduction step by the transfer pipe / nozzle 17 or, depending on the case, an inert gas such as nitrogen or argon is supplied from the inert gas supply pipe 15 to the NiCl ₂ gas. 1 for gas
Mol% to 30 mol%, and this mixed gas is transferred to a reduction step. The supply of the inert gas is a factor for controlling the particle size of the Ni powder. Excessive mixing of the inert gas not only results in a large consumption of the inert gas, but also results in energy loss and is uneconomical. From such a viewpoint, the preferable NiCl ₂ gas partial pressure of the mixed gas passing through the transfer pipe / nozzle 17 is in the range of 0.5 to 1.0 when the total pressure is 1.0.
In particular, when producing Ni powder having a small particle size of 0.2 μm to 0.5 μm, a partial pressure of about 0.6 to 0.9 is preferable. As described above, the NiCl ₂ gas generation amount can be arbitrarily adjusted by the chlorine gas supply amount, and the partial pressure of the NiCl ₂ gas can be arbitrarily adjusted by the inert gas supply amount.

B. Reduction step NiCl ₂ gas produced in the chlorination step is transferred continuously to the reduction step. The reduction step includes a reduction furnace 2 as shown in FIG.
It is desirable to use this method. At the upper end of the reduction furnace 2,
The nozzle of the transfer pipe / nozzle 17 described above (hereinafter simply referred to as the nozzle 17) is projected downward. A hydrogen gas supply pipe (reducing gas supply pipe) 21 is connected to an upper end surface of the reduction furnace 2, and a cooling gas supply pipe 22 is connected to a lower part of the reduction furnace 2. A heating means 20 is arranged around the reduction furnace 2. The nozzle 17 has a function of injecting NiCl ₂ gas (which may include an inert gas) from the chlorination furnace 1 into the reduction furnace 2 at a preferable flow rate, as described later.

When the reduction reaction by the NiCl ₂ gas and the hydrogen gas progresses, a bright flame (hereinafter, referred to as a flame) extending downward from the tip of the nozzle 17 similar to the combustion flame of a gaseous fuel such as LPG. F is formed. The supply amount of hydrogen gas to the reduction furnace 2 is 1.0 to 3.0 of the chemical equivalent of NiCl ₂ gas, that is, the chemical equivalent of chlorine gas supplied to the chlorination furnace 1.
It is about twice, preferably about 1.1 to 2.5 times, but is not limited thereto. However, an excessive supply of hydrogen gas causes a large flow of hydrogen in the reduction furnace 2, disturbs the NiCl ₂ jet flow from the nozzle 17, causes a non-uniform reduction reaction, and causes unconsumed gas release. It is uneconomical. The temperature of the reduction reaction may be any temperature that is higher than the temperature sufficient to complete the reaction.
Since the handling is easier when i powder is produced, the melting point of Ni is preferably lower than the melting point. Considering the reaction rate, durability of the reduction furnace 2 and economy, 900 ° C. to 1100 ° C. is practical, but not particularly limited thereto.

As described above, the chlorine gas introduced into the chlorination step becomes substantially the same molar amount of NiCl ₂ gas, which is used as a reducing raw material. NiCl ₂ gas or NiCl ₂
-The particle diameter of the obtained Ni powder P can be made appropriate by adjusting the linear velocity of the gas flow ejected from the tip of the nozzle 17 of the inert gas mixed gas. That is, if the nozzle diameter is constant, the Ni powder P generated in the reduction furnace 2 depends on the chlorine supply amount and the inert gas supply amount to the chlorination step.
Can be adjusted to a desired range. Nozzle 1
The linear velocity of the gas flow at the tip 7 (the sum of the NiCl ₂ gas and the inert gas (calculated value in terms of the gas supply amount at the reduction temperature)) is about 1 m / sec. At a reduction temperature of 900 ° C. to 1100 ° C. Set to 30 m / s, 0.
When producing Ni powder having a small particle size such as 1 μm to 0.3 μm, approximately 5 m / sec to 25 m / sec.
When producing Ni powder of 4 μm to 1.0 μm, approximately 1 m / sec to 15 m / sec is appropriate. The linear velocity of the hydrogen gas in the reduction furnace 2 in the axial direction is about 1/50 to 1/300 of the injection velocity (linear velocity) of the NiCl ₂ gas, preferably 1
/ 80 to 1/250 is good. Therefore, the state is such that the NiCl ₂ gas is substantially injected from the nozzle 17 into the static hydrogen atmosphere. In addition, it is preferable that the direction of the outlet of the hydrogen gas supply pipe 21 does not face the flame side.

In the production method of the present invention, when the supply flow rate of chlorine gas to the chlorination step is increased, Ni produced in the reduction step is reduced.
The particle size of the powder becomes smaller, and conversely, if the supply flow rate of chlorine gas is reduced, the particle size increases. Further, by controlling the partial pressure of the NiCl ₂ gas with the inert gas mixed with the NiCl ₂ gas near the outlet of the chlorination furnace 2 as described above, specifically, 1 mol% to the NiCl ₂ gas. 30
By mixing in the range of mol%, for example, increasing the partial pressure can increase the particle size of the generated Ni powder.
When the partial pressure of the Cl ₂ gas is reduced, the particle size of the generated Ni powder can be reduced.

C. Cooling Step The method for producing metal powder of the present invention may include a cooling step. As shown in FIG. 1, the cooling step can be performed in a space portion of the reduction furnace 2 opposite to the nozzle 17,
Alternatively, another container connected to the outlet of the reduction furnace 2 can be used. In the present invention, the term “cooling” refers to Ni in a gas stream (including hydrochloric acid gas) generated by a reduction reaction.
This is an operation performed to stop or suppress the growth of particles, and specifically means an operation of rapidly cooling a gas flow around 1000 ° C. after the reduction reaction to about 400 ° C. to 800 ° C. Of course, cooling to a temperature lower than this may be performed.

As a preferred example of cooling, an inert gas may be blown into a space below the flame tip. Specifically, the cooling gas supply pipe 2
By blowing nitrogen gas from Step 2, the gas flow can be cooled. By blowing the inert gas, the particle size can be controlled while preventing the aggregation of the Ni powder P.
By providing the cooling gas supply pipe at one location or at a plurality of locations by changing the position in the vertical direction of the reduction furnace 2, the cooling conditions can be arbitrarily changed, thereby controlling the particle size more accurately. Can be.

D. Mixed gas of Ni powder P and hydrochloric acid gas and the inert gas passed through the recovery step or steps is transferred to the recovery step, where the Ni powder P from the mixed gas is separated and recovered. For the separation and recovery, for example, one or a combination of two or more of a bag filter, an underwater collecting and separating means, an in-oil collecting and separating means, and a magnetic separating means is suitable, but not limited thereto. For example, when Ni powder P is collected by a bag filter, a mixed gas of Ni powder P, hydrochloric acid gas, and an inert gas generated in the cooling step is led to a bag filter, and only the Ni powder P is collected. You may send it. When using oil-in-oil collection separation, it is preferable to use normal paraffin having 10 to 18 carbon atoms or light oil. In the case of using collection in water or oil, a surfactant such as polyoxyalkylene glycol, polyoxypropylene glycol or a derivative thereof (monoalkyl ether, monoester) or sorbitan, sorbitan monoester, A known antioxidant such as a phenol-based or an amine-based metal deactivator represented by benzotriazole or a derivative thereof, and addition of one or more of these at about 10 ppm to 1000 ppm can prevent aggregation of metal powder particles. Effective for rust prevention.

E. Other Embodiments In the above embodiment, the reduction step is made into one step, but the reduction step can be divided into a plurality of steps. FIG.
Shows an example in which one reduction step is divided into two steps, and the same components as those shown in FIG. 1 are denoted by the same reference numerals. As shown in FIG.
Is not provided in the reduction furnace 2 ′ of the first reduction step, but is provided only in the reduction furnace 2 of the second reduction step. The amount of hydrogen gas supplied to the first reduction step is set to 0.5 to the chemical equivalent of NiCl _2.
In the second reduction step, the shortage of hydrogen gas is supplemented, and the total amount is 1.0 to 2.5 times the amount of NiCl ₂ gas.
By supplying twice the hydrogen gas, it is possible to control the particle size with higher accuracy and in a wider range. In this case, an appropriate amount of NiCl ₂ gas may be supplied near the outlet of the reduction furnace 2 ′ as necessary.

By dividing the reduction step into a plurality of steps as described above, the gas flow in the reduction furnaces 2 and 2 'can be made close to a laminar flow. As a result, reduction furnace 2, 2 '
The residence time of the Ni particles in the chamber can be made uniform,
The growth of i-particles can be made uniform. This allows
The particle size of the generated Ni powder can be made uniform. Further, it is preferable that the total volume of all the reduction furnaces when the reduction step is divided into a plurality of steps is equal to the volume of the reduction furnace when the division is not performed. Thereby, without changing the average residence time of the Ni powder contained in the gas flow passing through all the reduction furnaces, only the residence time distribution can be made close to that of the extrusion mixing, and more accurate particle size control can be performed. Become.

As described above, in the conventional production method in which solid NiCl ₂ is used as a starting material, which is evaporated to be subjected to a reduction reaction, it is extremely difficult to control the solid-gas conversion rate, and the process of sublimation of solid NiCl ₂ is performed. Therefore, the supply of NiCl ₂ gas into the reduction furnace
Although it was necessary to rely on the flow of a large amount of inert gas to the evaporating section of l ₂ , it was difficult to increase the partial pressure of NiCl ₂ gas, and it was very difficult to control the process. In the method, the amount of NiCl ₂ gas generated can be controlled by the supply amount of chlorine gas, so that process control is easy and stable. According to the manufacturing method of the present invention, C other than Ni
Powders such as u and Ag can also be produced by using the respective metals as starting materials and selecting the temperature for salification and reduction.

[0025]

The present invention will be described below in more detail with reference to specific examples. [Example 1] Chlorination furnace 1 of the apparatus for producing metal powder shown in FIG.
Was charged with 15 kg of Ni powder having an average particle size of 5 mm, the furnace atmosphere temperature was set to 1100 ° C., a chlorine gas was introduced at a flow rate of 4 Nl / min, and the metal Ni was chlorinated to generate a NiCl ₂ gas. 10% of the supply amount of chlorine gas (molar ratio)
The NiCl ₂ -nitrogen mixed gas was introduced at a flow rate of 2.3 m / sec (converted to 1000 ° C.) from the nozzle 17 into the reduction furnace 2 heated to an ambient temperature of 1000 ° C. At the same time, hydrogen gas was supplied from the top of the reduction furnace 2 at a flow rate of 7 Nl /
min to reduce the NiCl ₂ gas. And
In a cooling step, a nitrogen gas was mixed with a product gas containing Ni powder generated by the reduction reaction and cooled. Next, a mixed gas composed of nitrogen gas-hydrochloric acid vapor-Ni powder was led to an oil scrubber to separate and collect the Ni powder. Then, the recovered N
The i powder was washed with xylene and then dried to obtain a product Ni powder. This Ni powder has an average particle size of 0.70 μm (BET
(Measured by the method). The particle size determined from the SEM photograph was 0.80 μm, which almost coincided with the particle size determined by the BET method. This means that the surface of the Ni powder obtained in this example is smooth as in the SEM photograph example shown in FIG. As a result of performing the stable operation for 10 hours by the method of this embodiment, the supply amount of hydrogen gas and the supply amount of nitrogen gas per 1 g of Ni powder were 0.668 Nl /
g and 0.038 Nl / g.

Example 2 Ni powder was manufactured using the manufacturing apparatus shown in FIG. 1 under the same temperature conditions as in Example 1 under the gas flow conditions shown in Table 1. As shown in Table 1, it was confirmed that as the chlorine gas flow rate increased, the particle size of the generated Ni powder became smaller.

Example 3 Using the manufacturing apparatus shown in FIG. 1, the temperature conditions were the same as in the example, and Ni powder was manufactured under the gas flow conditions shown in Table 1. As shown in Table 1, by lowering the partial pressure of the NiCl ₂ gas,
The particle size of the i-powder can be reduced.

[0028]

[Table 1]

[0029]

As described above, according to the present invention, the following effects can be obtained. By controlling the supply amount of chlorine gas, the supply amount of metal chloride gas can be controlled, and stable operation of the entire process can be performed. Thereby, the particle size of the generated metal powder can also be reliably controlled. Ni, Cu, A having an average particle size in the range of 0.1 to 1.0 μm
g of metal powder can be easily produced. In particular, a powder of 0.2 to 0.4 μm, which is considered to be difficult to produce, can be easily produced. Nitrogen gas and hydrogen gas can be used efficiently,
The production cost of the metal powder can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one example of an apparatus for producing metal powder of the present invention.

FIG. 2 is a longitudinal sectional view showing another example of the apparatus for producing metal powder of the present invention.

FIG. 3 is an example of an SEM photograph of a Ni powder manufactured according to the present invention.

[Explanation of symbols]

1 ... Chlorination furnace, 2, 2 '... Reduction furnace, 11 ... Raw material supply pipe, 14 ... Chlorine gas supply pipe, 17 ... Transfer pipe and nozzle, 15 ... Inert gas supply pipe, 21 ... Hydrogen gas supply pipe (reducing gas supply pipe), 22 ... cooling gas supply pipe, M
... Ni particles, P ... Ni powder.

Claims (6)

[Claims] 1. A step of continuously generating a metal chloride gas by bringing a metal into contact with chlorine gas, and a step of bringing the metal chloride gas generated in the step of chloride into contact with a reducing gas to continuously generate a metal chloride. A method for producing metal powder, comprising: 2. The method for producing a metal powder according to claim 1, further comprising a cooling step of cooling a gas containing the metal powder generated in the reduction step with an inert gas. 3. The method according to claim 1, wherein a particle diameter of the metal powder is controlled by adjusting a flow rate of a chlorine gas introduced into the chlorination step. 4. The method for producing metal powder according to claim 1, wherein the reduction step is performed by ejecting the metal chloride gas into a hydrogen atmosphere. 5. The method according to claim 1, wherein the metal is Ni, and the reducing step is performed by ejecting NiCl ₂ gas having a partial pressure of 0.5 to 1.0 into a hydrogen atmosphere. A method for producing a metal powder according to any one of the above. 6. A chlorination furnace for salifying a metal filled therein, and a reduction furnace for reducing a metal chloride gas generated in the chlorination furnace, wherein the chlorination furnace is provided for supplying a metal therein. A raw material supply pipe, a chlorine gas supply pipe for supplying chlorine gas into the inside, a transfer pipe for transferring generated metal chloride gas to the reduction furnace, and an inert gas for diluting the metal chloride gas inside. An inert gas supply pipe for supplying the metal chloride gas to the inside; a nozzle for ejecting the metal chloride gas into the inside; a reducing gas supply pipe for supplying a reducing gas to the inside; A cooling gas supply pipe for supplying an inert gas for cooling the metal powder, wherein the chlorination furnace is disposed on the upstream side of the reduction furnace, and is directly connected to the chlorination furnace and the reduction furnace. The chlorination reaction and the reduction reaction An apparatus for producing metal powder, wherein the apparatus proceeds continuously.