JPS6152307A - Method and device for producing pulverous metallic powder - Google Patents

Abstract

PURPOSE:To obtain pulverous metallic powder having high purity with good productivity by supplying pellets formed by pelletizing a metallic chloride to the melt of the same kind of metal and subjecting the same to plasma heating in the presence of gaseous hydrogen. CONSTITUTION:The pellets P pelletized from the pulverous metallic powder are powder are supplied into a furnace body 1. The supply is preferably executed in an atmosphere of gaseous hydrogen and gaseous argon. The pellets are supplied toward the recess 5 of a crucible 4 and the melt M of the same kind of metal as the pellets P is held in the recess 5. The formation and holding of the melt M are executed by the injection of the plasma arc from a plasma torch 2 using gaseous hydrogen, etc. as a working gas. The supplied pellets P are captured by the melt M and are heated over the entire part by the presence of the gaseous hydrogen. The pellets are immediately reduced to metallic smoke V which is ejected through a discharge port 3. The ejected smoke V is captured and refined by the conventional practice.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method and apparatus for producing fine metal powder by plasma heating pellets of metal chloride.

In recent years, fine metal powders have been developed to have magnetic, optical, electrical, chemical reactivity, and sintering properties that are not found in metal blocks, and are used in large-capacity magnetic memories, sensors, and solar heat-absorbing paints. New fields of use are rapidly developing, such as superconducting materials, high-efficiency catalysts, and new sintered bodies.

The present invention relates to a method and apparatus for producing fine metal powder, which can produce fine metal powder with high productivity to meet such new uses.

<Prior art and its problems> Conventionally, chemical means and physical means have been employed as means for producing fine metal powder. The former chemical method involves obtaining fine metal powder as a precipitate through a chemical reaction in a solution;
Alternatively, metal compounds with high vapor pressure and low melting points, such as metal chlorides, are heated and evaporated and reduced with hydrogen to collect fine metal powder, but according to these conventional methods, , the particle size of the obtained metal fine powder is large,
Furthermore, there is a problem that the metal fine powder is inevitably contaminated with moisture, by-products, etc., resulting in low purity. The latter physical method is commonly known as vacuum evaporation method.
This method collects fine metal powder by heating and vaporizing the metal in a low-pressure inert gas, and is currently commonly used.This conventional method yields particles with small particle size and high purity. On the other hand, productivity is low due to slow evaporation rate.
Therefore, there is a problem that it is expensive.

Recently, a method for producing fine metal powder (commonly known as evaporation in gas method) has been proposed, which utilizes the reactivity of plasma hydrogen gas to metal and heats the metal with plasma. Volume No. 8, pp. 72-74, 1983
Year). This method involves plasma heating the metal in a hydrogen gas atmosphere and collecting the so-called metal smoke that is violently generated from the periphery of the molten metal, but even with this method, it is still difficult to produce the resulting fine metal powder. There are problems in terms of sexuality,
However, there are also problems such as particles with large diameters being mixed in due to the scattering of the melt that occurs during heating.

<Problems to be Solved by the Invention> The present invention solves the problems of conventional methods such as slanting. The purpose of the present invention is to provide a method and apparatus for producing fine metal powder with high productivity (specifically, by improving the throughput and yield per unit time) and thus economically. be.

<Means to Solve the Problems> However, the present inventors have found that plasma heating is relatively effective among conventional means in achieving the average particle size, purity, and productivity of the obtained metal fine powder. As a result of intensive research on the means for producing fine metal powder, we found that the problem with the above-mentioned productivity, etc., being still insufficient with this conventional method lies in the quantity and quality of the so-called metal salt (metal vapor) itself generated by plasma heating. In order to solve this problem, it is extremely effective to treat metal chloride pellets and heat them with plasma in the presence of hydrogen gas while temporarily trapping them in a molten metal of the same type. I discovered something,
The present invention has now been completed.

That is, the present invention relates to a method for producing fine metal powder, which comprises granulating a metal chloride into pellets, supplying the pellets to a molten metal of the same kind, and heating the pellets with plasma in the presence of hydrogen gas. and a roughly V-shaped furnace body, which is equipped with a plasma torch at one end and has an exhaust port at the other end, which is directly used in carrying out the invention of this manufacturing method. A crucible is attached to the center bottom side, and the crucible has a recess formed therein for holding molten metal, and a supply port for the pellets of metal chloride is opened at the upper side of the furnace body facing the crucible. The present invention relates to an apparatus for producing fine metal powder.

Hereinafter, the configuration of the present invention will be explained in more detail based on the drawings.

FIG. 1 is a cross-sectional view (partially omitted) showing an embodiment of the apparatus according to the present invention, and FIG. 2 is a partially enlarged view thereof, which also illustrates the implementation state of the method according to the present invention. Therefore, the structure of the apparatus according to the present invention will be explained first, and then the structure of the method according to the present invention will also be explained in the section of its operation.

There is a roughly V-shaped furnace body 1, which is naturally hollow, with a plasma torch 2 installed at one end of the 7-shape, and an exhaust port 3 at the other end. It is opened. A crucible 4 is attached to the bottom of the furnace body 1, which is made of copper and is water-cooled, and has a recess 5 that can hold the molten metal M.
is formed. A supply port 6 for metal chloride pellets P is opened in the upper side of the furnace body 1 so as to face the crucible 4 . In the case of the drawing, an inflow lower for hydrogen gas and/or argon gas is also provided around the outside of the supply port 6.

FIG. 3 is an enlarged plan view illustrating another crucible used in the present invention, FIG. 4 is a partial cross-sectional view taken along the line A-A, and FIG. 5 is a partial cross-sectional view taken along the line B-B.

The crucible 8 has a circular outer circumferential plane, and a two-stage recess 13.14 surrounded by inclined surfaces 9, 10, 11.12 is formed at approximately the center of the crucible 8. The molten metal is held in the recess 13 with a greater degree of .

<Operation> The operation of the apparatus according to the present invention will be explained below with reference to FIGS. 1 and 2, and the configuration of the method according to the present invention will also be explained here. In the present invention, the object to be treated is pellets obtained by granulating metal chloride. Pellets of this type can be easily obtained, for example, by subjecting a powder of nickel chloride (NiC/2), ferrous chloride (FeCh), or the like to a well-known granulator. The metal chloride used may contain water of crystallization (for example, NiC/z・
6H20) or a so-called anhydride, but it is preferable that the pellets granulated from these powders be dried from the viewpoint of stabilizing subsequent processing.

The above-mentioned belen) P is supplied from the supply port 6 to the inside of the furnace body 1 by falling under its own weight. Due to the nature of the invention, the supply in this case is
It is preferable to carry out in an atmosphere of hydrogen gas and/or argon gas. The supply direction is the recess 5 of the crucible 4. In this depression 5, a molten metal M of the same type of metal as the object to be treated (Belen) P is prepared in advance, and the molten metal M is held during the subsequent treatment. The molten metal M is created and held using hydrogen gas or a plasma arc ( This is done by jetting a plasma jet. Therefore, the pellets P supplied from the supply port 6 are once captured by the molten metal M. The captured pellets P are entirely heated in the presence of hydrogen gas in the furnace body 1 by the molten metal M heated at high temperature by the plasma arc, and are immediately reduced to become so-called metal smoke (metal vapor). . This metal smoke V is carried out from the exhaust port 3 as if riding on the jet flow of the plasma arc. The metal smoke V carried out may be condensed in the gas phase according to the conventional method, but the metal smoke V is collected with quenched water in a high-temperature IT, and the resulting suspension is separated into solid-liquid. The separated solid content is heated, for example, at 300° C. in a hydrogen gas stream.
It is preferable to perform indirect heating at a temperature of about 'C and reductive purification.

In the present invention, pellets P, which are granulated metal chlorides, are treated. Therefore, since the vapor pressure is higher than that of the metal composing it, and the metal chloride itself vaporizes directly by sublimation, the pereno)P evaporates rapidly, and the processed product becomes molten droplets and scatters. There is no such thing. In addition,
Since the reduction reaction is carried out in the form of vaporized gas molecules and ionized ions, the particle size of the metal fine powder produced by reduction is extremely small. Furthermore, if metal chloride is fed into the furnace body 1 from the feed port 6 in powder form, the feed rate cannot be as high as that of pellets P, and the unreacted particles are blown away by the plasma arc jet. There is an inconvenience that the powder is carried out from the exhaust port 3 as it is.

Therefore, when supplying the powder as it is, the amount of supply must be suppressed, but the above-mentioned disadvantages are still unavoidable. As a result, both productivity and purity as described above become low. The purpose of the present invention is to use Belen) P not only because it is easily supplied because it is continuously supplied by falling under its own weight, but also because it eliminates the above-mentioned disadvantages and improves productivity and purity as described above. This is because it can be done.

In the present invention, Pereno) P is once captured in a molten metal M of the same kind of metal. This is because the entire pellet P is efficiently and uniformly heated by the molten metal M heated at high temperature by the plasma arc from the plasma torch 2, so that the pellet P undergoes a reduction reaction quickly and completely. This is because the above-mentioned disadvantage can be eliminated by M capturing P (Pellet) itself. The molten metal M, which plays such a role, needs to be held almost fixedly at all times during processing, both in terms of trapping the pellets P and heating by the plasma arc. The reason why the recess 5 is formed in the crucible 4 is that the recess 5 satisfies this need.

If the straight crucible 8 illustrated in FIGS. 3 to 5 is used instead, even if the feeding direction of the pellets P is slightly shifted,
2, the molten metal will eventually be captured in the hottest molten metal which is held in the recess 13 and directly heated by the plasma arc. A crucible whose periphery is surrounded by an inclined surface is preferable. In FIG. 1, when hydrogen gas and/or argon gas flows in from the inflow lower, the gas seals the corresponding atmosphere C that supplies the pellets P to the molten metal M. As a result, not only can the shift in the supply direction of the pellets P be suppressed, but also the inside of the atmosphere C can be made into a hydrogen gas atmosphere with a relatively high concentration, so that the reduction reaction of the pellets P can be promoted accordingly. At this time, if the crucible 4 is made of water-cooled copper, the crucible 4 will not be consumed, so that fine metal powder of even higher purity can be obtained.

Further, in the present invention, a substantially V-shaped furnace body 1 is preferably used. Reduces resistance to plasma arc jet flow,
This is to carry out the metal smoke V generated by reduction on the jet stream from the exhaust port 3, and at the same time, it also removes the unreacted fragments of the pellets P, which are considerably heavier than the metal smoke V, the furnace body 1, etc. This is to prevent various impurities caused by this from being carried out from the exhaust gas.

<Effects of the Invention> As explained above, according to the present invention, extremely fine metal powder of high purity can be produced with good productivity, and new uses of metal fine powder are being rapidly developed. It has the effect of being able to fully adapt to the situation both qualitatively and quantitatively.

<Example> Using the apparatus illustrated in FIGS. 1 and 2, processing was carried out under the following conditions.

Pellet: Anhydrous nickel chloride (purity 99.4% by weight) granulated into a disk shape with a diameter of 16w and a thickness of 10+w Continuous supply of pellets: 167g/min x 20min Plasma torch: Output 84KW Working gas: Hydrogen gas 3ONly argon gas 35N
ty minutes Shielding gas: Hydrogen gas 360N 17 minutes Crucible: Made of water-cooled copper Three water tanks are lined up in series to collect the metal smoke carried out from the exhaust port of the furnace body with quenching water while maintaining its high temperature. The discharged metal fumes were sequentially passed into water), the resulting suspension was subjected to solid-liquid separation (filtration), and the separated solids were heated in a hydrogen gas stream (300°C, 2 hours/ Solid content 10
0f). As a result of analyzing the recovered metal fine powder, the generation rate of the metal smoke was 6s, 1q/
minute, yield of fine metal powder 90% by weight or more, purity 98% by weight
Above, oxygen content 1.0% by weight or less, chlorine content 0.0
It was 1% by weight or less.

[Brief explanation of the drawing]

FIG. 1 is a sectional view (partially omitted) showing an embodiment of the device according to the present invention, FIG. 2 is a partially enlarged view thereof, and FIG. 3 is an enlarged plan view illustrating a crucible used in the present invention. Figure 4 is the third
FIG. 5 is a partial cross-sectional view taken along the line A--A in the figure, and FIG. 5 is a partial cross-sectional view taken along the line B-B. 1...Furnace body, 2...Plasma arc, 3
...Exhaust port, 4.8°le 2'.5, 13
, 14... recess, 6... supply port, 7... inlet, 9, 10, 11, 12... inclined surface, P... pellet, M... molten metal, ■... Metal smoke, agent Hiroshi Iriyama Masashi Figure 1 Figure 2 Figure 3 r, B Figure 4 L'8 +4 Figure 5! 4

Claims (1)

[Scope of Claims] 1. A method for producing fine metal powder, which comprises granulating a metal chloride into pellets, and heating the pellets with plasma in the presence of hydrogen gas while supplying the pellets to a molten metal of the same type. 2. The method for producing fine metal powder according to claim 1, wherein the atmosphere in which the pellets are supplied to a molten metal of the same kind is sealed with hydrogen gas and/or argon gas. 3 A roughly V-shaped furnace body equipped with a plasma torch at one end and an exhaust port opened at the other end, a crucible is attached to the bottom side of the furnace body, and a molten metal is placed in the crucible. 1. An apparatus for producing fine metal powder, comprising: a recess for holding a metal chloride pellet; 4. The apparatus for producing fine metal powder according to claim 3, wherein an inlet for hydrogen gas and/or argon gas is provided around the outside of the supply port. 5 Claim 3 in which the crucible is made of water-cooled copper
The apparatus for producing fine metal powder according to item 1 or 4.