KR20040111647A - Method and device for producing metal powder - Google Patents

Abstract

The raw metal is fed into the chloride furnace intermittently or continuously, and the raw metal and chlorine gas are reacted in the chloride furnace to produce metal chloride vapor continuously, and the metal chloride vapor and hydrogen gas are reacted in the reduction furnace to continuously metal Get powder. In this case, the weight of the chloride furnace in the chlorination reaction is weighed, and the supply of the raw metal to the chloride furnace is controlled based on the weighing result.

Description

METHOD AND DEVICE FOR PRODUCING METAL POWDER}

Metal powders such as nickel and copper are widely used in all fields such as electronic materials and catalysts. Recently, metal powders called ultrafine powders having an average particle diameter of 1 µm or less are used for forming internal electrodes of multilayer ceramic capacitors. It is attracting attention as. Conventionally, precious metal powders such as silver, palladium, platinum and gold, or nonmetal powders such as nickel, cobalt, iron, molybdenum and tungsten have been used for electronic materials as conductive pastes, especially for internal electrodes of multilayer ceramic capacitors. It is used. In general, a multilayer ceramic capacitor has a structure in which a dielectric ceramic layer and a metal layer used as an internal electrode are alternately overlapped, and external electrodes connected to metal layers of the internal electrode are connected to both ends of the dielectric ceramic layer. As the material constituting the dielectric material, a material having a high dielectric constant such as barium titanate, strontium titanate, and yttrium oxide as its main component is used. On the other hand, as the metal constituting the internal electrode, the above-mentioned precious metal powder or nonmetal powder is used, but since a cheaper electronic material is required in recent years, the development of multilayer ceramic capacitors using the latter nonmetal powder has been particularly successful. Nickel powder is representative.

The multilayer ceramic capacitor is mixed with a dielectric powder, such as barium titanate, with an organic binder and suspended. The multilayer ceramic capacitor is formed into a sheet by the doctor blade method to form a dielectric green sheet, and the metal powder for internal electrodes is formed into an organic solvent, a plasticizer, It mixes with organic compounds, such as an organic binder, and forms a metal powder paste, and it prints on the green sheet by the screen printing method. This is laminated | stacked in several hundred layers, and it bakes at 1000 degreeC or more, and finally, an external electrode is welded to the both ends of a dielectric ceramic layer, and a multilayer ceramic capacitor is obtained.

In the method of manufacturing the multilayer ceramic capacitor as described above, a volume change occurs due to expansion and contraction of the metal powder during the step of evaporating and removing the organic component from the metal paste and the subsequent sintering step. On the other hand, the volume change also occurs by sintering in the dielectric itself. That is, since different materials such as dielectric and metal powder are sintered at the same time, a difference in sintering behavior due to the volume change of expansion and contraction of each material in the sintering process cannot be avoided. The problem was the destruction of the layered structure, called delamination.

In addition, as the size of the capacitor is reduced and the capacity is increased, the metal powder to be used as the internal electrode has an ultrafine powder having a particle size of 1 μm or less, as well as a particle size of 0.5 μm or less, due to the demand for high lamination, thinning of the internal electrode, and low resistance. Required. At this time, the presence of coarse powder of 1 μm or more or 2 μm or more makes it difficult to thin the internal electrode, and irregularities are generated on the surface of the electrode, causing shorts and, consequently, causing lamination. .

As a method for producing a metal powder having such a low coarse powder, Japanese Patent Application Laid-Open No. 10-219313 discloses a chlorination process for continuously generating metal chloride vapor by contacting a metal with chlorine gas, and reducing the metal chloride vapor generated in the chloride process. Disclosed is a method for producing a metal powder having a reduction step of contacting with a gas to continuously reduce the metal chloride.

The above production method is particularly excellent in that it can stably and efficiently manufacture nickel powder having a thickness of 1 µm or less. However, the metal powder produced still contains coarse powder of 1 micrometer or more and 2 micrometers or more, and improvement of the manufacturing method or apparatus which can control generation | occurrence | production of such a coarse powder was calculated | required.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for producing a metal powder and an apparatus for producing the same, and particularly to producing metal powders such as conductive paste fillers used in electronic components such as multilayer ceramic capacitors, bonding materials of titanium materials, and nickel bonded to various applications such as catalysts. It relates to a method and a manufacturing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS The longitudinal cross-sectional view which shows the structure of the manufacturing apparatus of the metal powder of embodiment of this invention.

2 is a graph showing the particle size distribution of nickel powders prepared in Examples and Comparative Examples;

3 is an SEM photograph of the nickel powder prepared in Example, (B) is an SEM photograph of the nickel powder prepared in Comparative Example,

4 is a graph showing the reaction rate (rate of change in weight of chloride furnace) in a chloride furnace.

<Explanation of symbols for main parts of drawing>

5... 9, chlorine furnace; Load cell

One… Raw material hopper 2... Load cell

13... Reduction furnace 3... Raw metal

Therefore, the present invention is a method of producing a metal chloride vapor by reacting a raw metal with chlorine gas, and reacting the metal chloride vapor with a hydrogen gas to obtain a metal powder, in particular having a stable particle size without generating coarse powder. An object of the present invention is to provide a method and apparatus for producing a metal powder suitable for an internal electrode of a multilayer ceramic capacitor having an average particle diameter of 1 µm or less.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to achieve the said objective, the present inventors discovered that the chlorine gas which did not react in the chloride furnace is supplied to a reduction furnace, and coarse powder is produced by the reaction temperature rising by this. .

The method for producing a metal powder of the present invention is made based on the above findings, and the raw metal is intermittently or continuously supplied into a chloride furnace, and the raw metal and chlorine gas are reacted in the chloride furnace to continuously generate metal chloride vapor. In the method for producing a metal powder in which a metal chloride vapor and hydrogen gas are reacted in a reduction furnace to continuously obtain a metal powder, the weight of the chloride furnace in the chlorination reaction is weighed and based on the result of the weighing, It is characterized by controlling the supply of the furnace.

Moreover, the manufacturing apparatus of the metal powder of this invention is the raw material hopper for supplying a raw material metal, the chloride furnace which chlorides the raw material metal supplied from this raw material hopper, and the reduction furnace which reduces the metal chloride vapor which generate | occur | produced in this chloride furnace. The raw material hopper and the chloride furnace are connected to the raw material supply pipe through a valve for supplying the raw metal and controlling the supply amount, and the chloride furnace and the reduction furnace transfer the metal chloride vapor generated in the chloride furnace to the reduction furnace. The chlorine furnace is provided with a chlorine gas supply pipe for supplying chlorine gas therein, and the reducing furnace includes a nozzle for blowing metal chloride vapor therein and a hydrogen gas for supplying hydrogen gas therein. A supply pipe and a cooling gas supply pipe for supplying an inert gas for cooling the reduced metal powder therein, and for weighing the entire weight of the chlorine furnace It is characterized by further comprising weighing means and control means for controlling the supply amount of the raw metal to the chloride furnace based on the weighing result of the weighing means.

According to the present invention, since the supply amount of the raw metal is controlled based on the weighing result of the entire weight of the chloride furnace, an appropriate amount of the raw metal can always be filled in the chloride furnace. As a result, the reaction between the raw metal and the chlorine gas is uniform, and the chlorine gas supplied to the reduction furnace by unreacted can be reduced.

The metal powder of this invention is a metal which can be used for the internal electrode and catalyst of a multilayer ceramic capacitor, and is a noble metal, such as silver, palladium, platinum, gold, or nonmetals, such as nickel, cobalt, iron, molybdenum, tungsten. Among these, nonmetals are preferable at the point of being inexpensive, and especially nickel is more preferable.

Although there is no restriction | limiting in particular about the particle shape of the metal powder manufactured by this invention unless there is a problem as each use, When used for the internal electrode of a multilayer ceramic capacitor, the average particle diameter of a metal powder becomes like this. Preferably it is 0.01-1. Microparticles | fine-particles, More preferably, the microparticles | fine-particles of the range 0.1-1 micrometer, especially 0.1-0.5 micrometer are used. Moreover, it is preferable that the specific surface area by BET of a metal powder is 1-20 m <2> / g. Moreover, it is preferable that the particle shape of a metal powder is spherical in order to improve sintering characteristic or dispersibility.

The present invention is a method of continuously producing a metal chloride vapor by reacting a raw metal and chlorine gas in a chloride furnace, and continuously reacting the metal chloride vapor and hydrogen gas in a reduction furnace to obtain a metal powder continuously (hereinafter referred to as "chlorination reduction method"). May be referred to as "). Generally, in the manufacturing process of the metal powder by such a gaseous reduction reaction, a metal atom produces | generates at the moment when metal chloride vapor and hydrogen gas contact, and ultrafine particles generate | generate and grow as metal atoms collide and agglomerate. And the particle diameter of the metal powder produced | generated is determined according to conditions, such as partial pressure and temperature of the metal chloride vapor in a reduction furnace. In this chlorine reduction method, since the amount of metal chloride vapor corresponding to the supply amount of chlorine gas is generated, the amount of metal chloride vapor supplied to the reduction furnace can be controlled by controlling the supply amount of chlorine gas. In addition, since the metal chloride vapor is generated by the reaction of the chlorine gas and the metal, unlike the method of generating the metal chloride vapor by the heat evaporation of the solid metal chloride, not only the use of the carrier gas can be reduced, but also the manufacturing conditions Therefore, it is also possible not to use. Therefore, manufacturing cost can be reduced by reducing the usage-amount of carrier gas, and reducing heating energy accordingly.

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

As described above, the chlorination reduction method has an advantage in that a metal powder having a stable particle size can be obtained and can be efficiently manufactured at low cost. However, when metal powder is continuously manufactured by the chlorination reduction method, a change may occur in the rate of chlorination reaction in a chloride furnace. When a change in the rate of chlorination occurs, the amount of generation of metal chloride vapor generated in the chlorine furnace changes, so that the partial pressure of the metal chloride in the reducing furnace changes, resulting in unstable particle size of the resulting metal powder and the desired particle size. Metal powder may not be obtained. In particular, in the case of producing the nickel powder for the internal electrode of the multilayer ceramic capacitor, when such a change in the chlorine reaction rate occurs, a large amount of coarse powder of 1 µm or more or 2 µm or more may occur.

For example, in the case of nickel powder production, a pellet raw material nickel of several millimeters is filled in a chloride furnace, and it heats about 800 degreeC then, chlorine gas and raw material nickel are continuously supplied, and a chlorination reaction is performed. At this time, the raw material nickel is chlorinated to become nickel chloride vapor, and the packed layer of the raw material nickel in the chloride furnace is reduced. At this time, if the raw nickel packed layer is constantly reduced along the cross section of the chloride furnace, the chlorine reaction rate is kept constant.

However, the temperature distribution of the raw material nickel filling layer in the chloride furnace is not uniform, and depending on the position of the chlorine gas supplied to the chloride furnace or the position of the raw material nickel, the central or outer portion of the raw material nickel filling layer is selectively chlorinated and reduced. There is a case. If the reduction in the nonuniform raw nickel packing layer continues, a gap of a certain size penetrates the filling layer, so that a part of the supplied chlorine gas does not come into contact with the raw material nickel and is directly reduced with the nickel chloride vapor. It is supplied to. In this way, when unreacted chlorine gas is directly supplied to the reduction furnace, the partial pressure of nickel chloride vapor in the reduction furnace decreases, and chlorine gas is supplied to the reduction reaction, whereby the rate of formation of nickel powder increases, resulting in coarse powder. It increases abnormally.

The present inventors have found that the biggest cause of coarse powder generation is the inflow of unreacted chlorine gas into the reduction furnace in this chlorination reaction. Originally, such an abnormal phenomenon can be detected by continuously quantitating the composition of steam and gas generated from a chlorine furnace. However, separation and quantification were difficult because it is a mixed gas of chlorine gas and metal chloride as in the present invention.

Therefore, the rate of chlorine reaction corresponds to the rate of change in the weight of the chlorine furnace. Therefore, it is preferable to monitor the rate of change in the weight of the chlorine furnace and to feedback control the rate of chlorine reaction. As the means for controlling the chlorine reaction rate, when the reaction rate is lowered, the outflow of unreacted chlorine gas due to the occurrence of a gap penetrating into the raw metal packed layer in the chloride furnace is mainly caused, as described above. There is a method of reducing the amount of chlorine gas to be supplied, or limiting the amount of metal chloride vapor generated from the chloride furnace to the reduction furnace. However, these methods lower the productivity of the entire metal powder, and there is a risk of uneven reaction in the reduction furnace, resulting in unstable particle size of the produced metal powder. The raw metal is fed to the chlorination furnace to remove it. Normally, in continuous operation, the raw metal is continuously or intermittently supplied to the chloride furnace, but in this case, when a decrease in the reaction rate is detected, it is preferable to increase the supply amount of the raw metal in response to this.

As described above, when chlorine gas flows into the reduction furnace without being in contact with the raw metal in the chloride furnace and remains unreacted, the reaction rate of the chloride reaction decreases rapidly, and if left unchanged, the particle size of the metal powder produced is unstable. It may be determined and a large amount of coarse powder may be generated.

Therefore, in the present invention, it is preferable to monitor the rate of change of the weight of the chloride furnace and to temporarily increase the supply amount of the raw metal when the signs of change of the rate of change are recognized. For example, as shown in FIG. 4, when detecting the drop P of the change rate, the same amount or more as the raw metal to be supplied for 30 minutes intermittently or continuously is supplied once or many times. After that, it supplies as intermittent or continuous as usual or a little amount is reduced. Thereby, since the state of excess chlorine gas can be eliminated at once, the particle size of the metal powder obtained by reducing the chlorine gas supplied to a reduction furnace by unreacting can be stabilized, and generation | occurrence | production of coarse powder can be suppressed especially.

Specifically, the weighing means of the furnace is preferably a load cell, and it is particularly preferable that the weight change can be detected over time. In the present invention, a change in the weight of the chloride furnace is detected, and a change in weight per unit time is obtained from this, and this is controlled as the reaction rate. That is, this reaction rate is the weight per unit time of the generated metal chloride vapor, and if this reaction rate is always kept constant, the chlorination reaction is stable, and as a result, the particle size of the metal powder obtained by making the reaction in the reduction furnace stable also It is stable.

In addition, when the raw metal is continuously or intermittently supplied to the chloride furnace as described above, the weight of the raw material hopper for storing and supplying the raw metal is also weighed by the load cell. Thereby, the reaction rate of the chloride reaction can be detected and controlled from the weight change of the raw material hopper and the weight change to the chloride.

The form of the preferable manufacturing method in this invention is shown below.

(1) Metal Raw material such as nickel is supplied from a raw material hopper having a weighing means by a load cell to a chloride furnace equipped with a weighing means by a load cell to form a raw metal packed layer having a certain height.

(2) Thereafter, the chlorine furnace is heated to supply chlorine gas into the chlorine furnace to start the chlorination reaction.

(3) At the same time, the raw metal is supplied continuously or intermittently.

(4) The reaction rate of the chloride reaction is continuously detected from the weight change of the raw material hopper and the chloride furnace.

(5) If a change in the reaction rate, in particular a decrease, is observed, the supply of the raw metal is increased to reach a predetermined reaction rate.

In the above aspect, the weight of the raw material hopper and the weight of the chlorine furnace is weighed to detect the change in the reaction rate of the chlorine reaction, and in conjunction with this to automatically control the supply amount of the raw metal to control the reaction rate. It is further more preferable that it is a manufacturing system.

In the apparatus of the present invention, the chlorination furnace is disposed upstream of the reduction furnace as described above, and the chlorination reaction and the reduction reaction can be simultaneously and continuously performed by directly connecting the chloride furnace and the reduction furnace, thereby efficiently producing metal powder. can do. In addition, since the amount of metal chloride vapor corresponding to the supply amount of chlorine gas into the chloride furnace is generated, and since the furnace and the reduction path are directly connected, the amount of metal chloride vapor supplied to the reduction furnace by controlling the supply amount of chlorine gas. Can be controlled.

In addition, since an inert gas can be supplied to the chloride furnace by providing an inert gas supply pipe in the chloride furnace, the partial pressure of the metal chloride vapor in the reduction furnace can be controlled. Therefore, the particle size of the metal powder can be controlled by controlling the supply amount of chlorine gas or the partial pressure of the metal chloride vapor supplied to the reduction furnace. Moreover, since the measuring means which measures the weight of the whole chlorine furnace is provided, the change of the reaction rate in a chlorination reaction can be detected, and by controlling this, the particle size of the metal powder obtained is stabilized and especially generation of coarse powder is carried out. It is now possible to suppress. Moreover, by providing the measuring means which measures a weight also about a raw material hopper, it becomes possible to control reaction rate with high precision.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the manufacturing apparatus of the metal powder of this invention is described in detail, referring drawings. It is preferable to perform a chlorination reaction with the chlorination furnace 5 shown in FIG. The chloride furnace 5 is supported by the load cell 9. The raw material hopper 1 for storing and supplying the raw metal 3 is arrange | positioned at the upper part of the chlorination furnace 5, The raw material hopper 1 provided through raw metal supply valves 4a and 4b on the way. It is connected to the top of the chloride furnace 5 by the raw material metal supply pipe 21. The raw material hopper 1 is supported by the load cell 2, and the load cell 2 is connected to the load cell 9 of the chloride furnace 5.

The chlorine gas supply pipe 6 is connected to the upper part of the chloride furnace 5, and the inert gas supply pipe 8 is connected to the lower part. The heater 7 is arrange | positioned around the chlorination furnace 5, and the metal chloride vapor conveyance pipe 12 is connected to the lower part of the chlorination furnace 5. As shown in FIG. The chloride furnace 5 is either vertical or horizontal, but is preferably vertical in order to uniformly perform the solid-gas contact reaction. Moreover, the intermediate part of the raw material supply pipe 21, the chlorine gas supply pipe 6, and the inert gas supply pipe 8 becomes a structure with elasticity and flexibility like a bellows, for example, and the raw material hopper 1 and the chloride furnace 5 It is possible to accurately weigh the weight of. Moreover, the filling 11 is arrange | positioned in the bottom part of the chloride furnace 5 so that the bottom of a chloride furnace may be comprised. The filler 11 is composed of small pieces of quartz glass or the like, for example, which allows metal chloride vapor and an inert gas to flow and prevents the fall of the raw metal.

The chlorine gas is continuously introduced from the chlorine gas supply pipe 6 by measuring the flow rate. The furnace 5 and other members are preferably quartz glass. The metal chloride vapor delivery pipe 12 is connected to the metal chloride vapor jet nozzle 14 of the upper end surface of the reduction furnace 13 mentioned later.

Regardless of the form of the starting metal 3 as a starting material, granules, lumps, plates, and the like having a particle diameter of about 5 mm to 20 mm are preferable from the viewpoint of contact efficiency and prevention of pressure loss rise, and the purity is generally 99.5% or more. This is preferred. The height of the raw metal packed layer 108 in the chloride furnace 5 is based on the chlorine feed rate, the chlorine furnace temperature, the continuous operation time, the shape of the raw metal 3, and the like. It may be appropriately set in a range sufficient for. The temperature in the chlorination furnace 5 may be any temperature at which the raw metal is chlorinated, but in the case of metal nickel, the temperature is set at 800 ° C. or higher in order to sufficiently advance the reaction, and is set at 1483 ° C. or lower, which is the melting point of nickel. Considering the durability of the furnace 5, the range of 900 to 1100 degreeC is preferable practically.

The chlorine gas is continuously supplied into the chlorine furnace 5 from the chlorine gas supply pipe 6, and the raw metal 3 is continuously or intermittently supplied by opening and closing the raw material supply valve 4 from the raw material hopper 1. At that time, the supply amount of the raw metal is measured by the load cell 2.

The metal chloride vapor generated in the chloride furnace 5 is transferred to the reduction furnace 13 by the metal chloride vapor transfer pipe 12 as it is, or in some cases, such as nitrogen or argon, from the inert gas supply pipe 8. Gas is mixed with 1 mol%-30 mol% with respect to metal chloride vapor, and this mixed gas is sent to a reduction furnace. The supply of this inert gas becomes a particle size control factor of the metal powder. Excessive mixing of the inert gas not only leads to enormous consumption of the inert gas, but also results in energy loss and is uneconomical. In view of this, the preferred metal chloride vapor partial pressure of the mixed gas passing through the feed pipe 12 is a metal powder having a small particle size in the range of 0.5 to 1.0, in particular a particle size of 0.15 탆 to 0.5 탆, when the total pressure is 1.0. When manufacturing, about 0.6-0.9 partial pressure is preferable. As described above, the metal chloride vapor generation amount can be arbitrarily adjusted according to the chlorine gas supply amount, and the partial pressure of the metal chloride vapor can also be arbitrarily adjusted to the inert gas supply amount.

The metal chloride vapor generated in the chloride furnace 5 is continuously transferred to the reduction furnace 13. At the upper end of the reduction furnace 13, a metal chloride vapor jet nozzle 14 (hereinafter simply referred to as a nozzle 14) connected to the metal chloride vapor transfer pipe 12 protrudes downward. In addition, the hydrogen gas supply pipe 15 is connected to the upper end surface of the reduction furnace 13, and the cooling gas supply pipe 17 is connected to the lower part of the reduction furnace 13. In addition, a heater 16 is disposed around the reduction furnace 13. As described later, the nozzle 14 has a function of ejecting metal chloride vapor (which may contain an inert gas) from the chloride furnace 5 into the reduction furnace 13 at a preferable flow rate.

When the reduction reaction by the metal chloride vapor and hydrogen gas proceeds, a downwardly extending reaction salt 18 is formed from the tip of the nozzle 14, similar to the fuel salt of gaseous fuel such as LPG. The hydrogen gas supply amount to the reduction furnace 13 is about 1.0 to 3.0 times, preferably about 1.1 to 2.5 times, the chemical equivalent of the metal chloride vapor, that is, the chemical equivalent of the chlorine gas supplied to the chloride furnace 5, It is not limited to this. However, an excessive supply of hydrogen gas causes a large flow of hydrogen in the reduction furnace 13, disturbing the metal chloride vapor jet stream from the nozzle 14, causing a non-uniform reduction reaction and at the same time not being consumed. It is uneconomical, causing emissions. In addition, the temperature of the reduction reaction may be any temperature sufficient to complete the reaction. However, in the case of producing nickel powder, since it is easier to handle solid nickel powder, the melting point of nickel is preferably lower than the reaction rate and the reduction furnace. Considering the durability and economical efficiency of (13), 900 to 1100 ° C is practical, but is not particularly limited thereto.

As described above, the chlorine gas introduced into the chloride furnace 5 becomes a substantially equivalent molar amount of metal chloride vapor, which becomes a reducing raw material. The particle diameter of the metal powder 19 obtained can be appropriately adjusted by adjusting the linear velocity of the gas stream blown off from the tip of the nozzle 14 of the metal chloride vapor or the metal chloride vapor-inert gas mixed gas. In other words, if the nozzle diameter is constant, the particle size of the metal powder 19 produced in the reduction furnace 13 can be adjusted to the target range by the chlorine supply amount to the chloride furnace 5 and the inert gas supply amount. The linear velocity (the sum of the metal chloride vapor and the inert gas (calculated value in terms of the gas supply amount at the reduction temperature)) of the preferred gas flow at the tip of the nozzle 14 is about 1 m / at a reduction temperature of 900 ° C to 1100 ° C. In the case of producing nickel powder having a particle size of about 30 m / sec and having a small particle size of 0.1 µm to 0.3 µm, when producing nickel powder having approximately 5 m / sec to 25 m / sec and 0.4 µm to 1.0 µm, About 1 m / sec-15 m / sec are suitable. The flux in the axial direction in the reduction furnace 13 of the hydrogen gas is about 1/50 to 1/300 of the ejection rate (speed) of the metal chloride vapor, and preferably 1/80 to 1/250. Therefore, the metal chloride vapor is substantially in a state in which it is injected from the nozzle 14 in the static hydrogen atmosphere. In addition, it is preferable that the direction of the outlet of the hydrogen gas supply pipe 15 does not face the flame side.

In the production method of the present invention, when the chlorine gas supply flow rate to the chloride furnace 5 is increased, the particle diameter of the metal powder 19 produced in the reduction furnace 13 is reduced, and conversely, when the supply flow rate of the chlorine gas is reduced, the particle diameter is reduced. This increases. In addition, by adjusting the partial pressure of the metal chloride vapor with an inert gas mixed with the metal chloride vapor near the outlet of the chloride furnace 5 as described above, specifically 1 mol% to 30 mol% with respect to the metal chloride vapor. When mixing in the range, for example, by increasing the partial pressure, the particle diameter of the metal powder to be produced can be increased. On the contrary, by lowering the partial pressure of the metal chloride vapor, the particle diameter of the metal powder to be produced can be reduced.

As described above, the chlorine reaction is continuously performed in the chlorine furnace 5, and in the process of producing metal powder generated in the metal chloride vapor in the reducing furnace 13, the weight of the chlorine furnace 5 is transferred to the load cell 9. Weighing is continuously detected for weight change. On the other hand, the weight change of the raw material hopper 1 is continuously weighed by the load cell 2, and the weight of the raw material metal 3 supplied into the chloride furnace 5 is detected. The reaction rate of the chlorination reaction is detected from these weight changes over time. That is, the sum of the weight change per unit time of the raw material hopper 1 and the weight change per unit time of the chloride furnace 5 becomes the weight per unit time of the metal chloride vapor generated in the chloride furnace 5, and the reaction rate (metal Chloride vapor generation weight / hour).

During the production of the metal powder, the reaction rate is continuously monitored, and when the signs of the reaction rate decrease, the supply of the metal raw material 3 from the raw material hopper 1 is temporarily increased to stabilize the reaction rate. Let's do it. Since the surface of the raw material metal filling layer 10 is nonuniform at this time, it is preferable to supply a raw metal, confirming visually so that this upper surface may become smooth. In addition, when the weight change detected by the load cell 2 and the load cell 9 and the raw material metal supply valve 4 are interlocked using the dispersion control system etc., when the indication of the fall of reaction speed arises, a metal supply valve It is preferable to set so that (4) will open and the raw material metal 3 will be supplied stably.

In the manufacturing method of the metal powder of this invention, a cooling process can be provided. As shown in FIG. 1, the cooling process can be performed in the space part on the opposite side to the nozzle 11 in the reduction furnace 13, or it can also connect to the outlet of the reduction furnace 13, and can use another container. Do. In addition, the cooling said in this invention is an operation performed in order to stop or suppress the growth of the metal particle in the gas stream (containing hydrochloric acid gas) produced | generated by the reduction reaction, specifically, 1000 degreeC vicinity which completed the reduction reaction. Means an operation of rapidly cooling the gas stream to about 400 ° C to 800 ° C. Of course, you may cool to below this temperature.

As a preferable example for performing cooling, it can be comprised so that an inert gas may be blown in the space part below from a flame front end. Specifically, the gas flow can be cooled by blowing nitrogen gas from the cooling gas supply pipe 17. By blowing inert gas, particle size control can be performed, preventing aggregation of the metal powder 19. FIG. The cooling gas supply pipe can be arbitrarily changed by changing a position in one place or in the up-down direction of the reduction furnace 13, and can change a cooling condition arbitrarily, and can control particle size more accurately.

The mixed gas of the metal powder 19 and the hydrochloric acid gas and the inert gas which passed through the above process is sent to a collection | recovery process, and the metal powder 19 is separated and collect | recovered from the mixed gas there. In the separation and recovery, for example, one or two or more types of bug filters, underwater collection separation means, oil collection separation means, and magnetic separation means are preferable, but not limited thereto. For example, when the metal powder 19 is collected by the bug filter, the mixed gas of the metal powder 19 and hydrochloric acid gas and the inert gas generated in the cooling process is led to the bug filter, so that only the metal powder 19 You may send to a washing | cleaning process after collection | recovery. In the case of using oil-in-oil separation, it is preferable to use normal paraffin or light oil having 10 to 18 carbon atoms. In the case of using in-water or water-in-oil collection, the collection liquid contains polyoxyalkylene glycol, polyoxypropylene glycol or derivatives thereof (monoalkyl ether, monoester) or surfactants such as sorbitan and sorbitan monoester, and benzotriazole. Or 10 ppm-1000 ppm of well-known antioxidants, such as a phenol type or amine of a metal inert agent represented by the derivative, and these 1 type, or 2 or more types are added, and it is effective for preventing aggregation of a metal powder particle, and rust prevention. .

As mentioned above, in the manufacturing method and manufacturing apparatus of the conventional metal powder by the chlorination method, since inflow of unreacted chlorine gas into the reduction furnace by the heterogeneous reaction of the raw material metal filling layer in a chloride furnace occurred, The particle size of the metal powder to be produced was not stable, and coarse particles were generated in particular. However, in the production method and apparatus of the present invention, the reaction rate of the chlorination reaction can be controlled and stabilized by weighing the weight of the chlorine furnace, so that the inflow of unreacted chlorine gas into the reduction furnace can be prevented, and as a result, Metal powders having a stable particle size, particularly free of coarse particles, can be produced. In addition, in the conventional method or the conventional apparatus, the reaction rate could not be increased because of the unstable reaction such as a sharp drop in the chlorine reaction as described above. However, in the present invention, the reaction rate is stable, so that the reaction rate can be increased, resulting in metal The productivity of the powder can be improved.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

(Example)

In the chloride furnace 5 of the apparatus for producing a metal powder shown in FIG. 1, 15 kg of raw material nickel having an average particle diameter of 5 mm was filled from the raw material hopper 1, and the flow rate of 4Nl / min was set at an atmospheric temperature of 1100 ° C in the chloride furnace. Chlorine gas was introduced to initiate the chloride reaction. Thereafter, the raw material nickel was intermittently supplied from the raw material hopper 1 at 0.5 kg / at 5 minute intervals to the chloride furnace 5. Thus, metal nickel was chlorided to generate nickel chloride vapor.

Nitrogen gas of 10% (molar ratio) of the chlorine gas supply amount was mixed with this, and the flow rate 2.3m from the nozzle 14 to the reduction furnace 13 which heated this nickel chloride vapor-nitrogen mixed gas to the ambient temperature of 1000 degreeC. It was introduced in / second (1000 degreeC conversion). At the same time, hydrogen gas was supplied from the top of the reduction furnace 13 at a flow rate of 7 Nl / min to reduce nickel chloride vapor.

As described above, the chlorination reaction and the reduction reaction are carried out simultaneously and in parallel (30 hours), at which time the weights of the raw material hopper 1 and the chloride furnace 5 are weighed with the load cells 2 and 9, respectively. The reaction rate of the chlorination reaction in a chlorination furnace was detected continuously from the weight change. Since the indication of reaction rate fall was seen after 25 hours after the start of manufacture, the supply amount of the raw material nickel from the raw material hopper 1 was increased to 5 kg per one time, the reaction rate was stabilized, and manufacture was continued.

The product gas containing the nickel powder produced | generated by the reduction reaction mixed and cooled nitrogen gas in the cooling process. Subsequently, a mixed gas composed of nitrogen gas-hydrochloric acid vapor-nickel powder was introduced into pure water to separate and recover the nickel powder. Subsequently, the recovered nickel powder was washed with pure water and then dried to obtain a product nickel powder. The particle size distribution of the obtained nickel powder is shown in FIG. 2, and a SEM photograph is shown in FIG. The average particle diameter by BET method was 0.40 micrometer, the average particle diameter when suspended in an organic solvent was 1.50 micrometer, and the coarse powder of 5 micrometers or more was 0%. Here, the average particle diameter and particle size distribution when suspended in an organic solvent, using a laser light scattering method method particle size analyzer (Coulter LS230: Coulter Co., Ltd.), the appropriate amount of metal powder suspended in α-terpineol and then ultrasonic The mixture was dispersed for 3 minutes, measured at a sample refractive index of 1.8, and the particle size distribution of the volume statistics was obtained.

(Comparative Example)

The preparation was carried out in the same manner as in Example 1 except that the weight of the raw material hopper 1 and the chloride furnace 5 was not weighed and the reaction rate of the chloride reaction in the chloride furnace was not controlled. The particle size distribution of the obtained nickel powder is shown in FIG. 2, and a SEM photograph is shown in FIG. The average particle diameter by BET method was 0.45 micrometer, the average particle diameter when suspended in an organic solvent was 1.45 micrometer, and the coarse powder of 5 micrometers or more was 3.0%.

The particle size distribution of the nickel powder prepared in the example of the method of the present invention is very small in coarse powder, compared to the nickel powder prepared in Comparative Example from FIG. 2, and is produced in Comparative Example from the SEM photograph of FIG. 3. One nickel powder shows a lot of coarse powder of 1 μm or more, whereas the nickel powder prepared in Examples is very small in coarse powder of 1 μm or more.

As explained above, according to the manufacturing method and manufacturing apparatus of the metal powder of this invention, metal powder, such as nickel powder, which requires a fine particle diameter of 1 micrometer or less, such as an internal electrode of a multilayer ceramic capacitor, can be manufactured efficiently, and The reaction rate of the chlorination reaction can be controlled, resulting in the effect of producing a metal powder without coarse powder with a uniform particle size.

Claims (17)

The raw metal is intermittently or continuously supplied into the chlorine furnace, the raw metal and chlorine gas are reacted in the chlorine furnace to continuously generate metal chloride vapor, and the metal chloride vapor and hydrogen gas are reacted in a reduction furnace. A method of producing a metal powder in which a metal powder is continuously obtained, wherein the weight of the chloride furnace in the chlorination reaction is weighed, and the supply of the raw metal to the chloride furnace is controlled based on the weighing result. Method of making the powder. The method for producing a metal powder according to claim 1, wherein the rate of change of the weight of the chloride furnace is monitored and the supply of the raw metal to the chloride furnace is controlled based on the rate of change. The method for producing a metal powder according to claim 2, wherein the supply amount of the raw metal is temporarily increased when the indication that the change rate falls sharply is recognized. 3. The method according to claim 2, wherein the speed change is detected and, in conjunction with this, the amount of supply of the raw metal to the chloride furnace is automatically controlled so that the chloride of the raw metal and the chlorine gas in the chloride furnace is controlled. A method for producing a metal powder, characterized in that the reaction rate is controlled. The method for producing a metal powder according to claim 1, wherein the weight of the chloride furnace is measured by a load cell. The method for producing a metal powder according to claim 1, wherein the weight of the entire raw material hopper for supplying the raw metal to the chloride furnace is weighed. The method for producing a metal powder according to claim 1, wherein the metal is nickel. The method for producing a metal powder according to claim 7, wherein the metal powder is a nickel powder having an average particle diameter of 0.01 to 1 µm. The method for producing a metal powder according to claim 8, wherein the metal powder is for a conductive paste. The method for producing a metal powder according to claim 8, wherein the metal powder is for a laminated ceramic capacitor. A raw material hopper for supplying a raw metal, a chloride furnace for chlorideing the raw metal supplied from the raw material hopper, and a reduction furnace for reducing metal chloride vapor generated in the chloride furnace, The raw material hopper and the chloride furnace communicate with the raw material supply pipe through a valve for supplying the raw metal and controlling the supply amount, The chloride furnace and the reduction furnace are in communication with the transfer pipe for transferring the metal chloride vapor generated in the chloride furnace to the reduction furnace, The chloride furnace is provided with a chlorine gas supply pipe for supplying chlorine gas therein, The reduction furnace includes a nozzle for ejecting the metal chloride vapor therein, a hydrogen gas supply pipe for supplying hydrogen gas therein, and a cooling gas supply pipe for supplying an inert gas for cooling the reduced metal powder therein. and, Weighing means for weighing the entire weight of the chloride furnace, and control means for controlling the supply amount of the raw metal to the chloride furnace on the basis of the weighing result of the weighing means, the production of metal powder Device. 12. The production of metal powder according to claim 11, wherein the control means monitors the rate of change of the weight of the chloride furnace and controls the supply of the raw metal to the chloride furnace based on the rate of change. Device. 13. The apparatus for producing a metal powder according to claim 12, wherein the control means temporarily increases the supply amount of the raw metal when a change in the rate of change is recognized. 13. The control apparatus according to claim 12, wherein, when detecting the change rate, the control means automatically controls the amount of supply of the raw metal to the chloride furnace in conjunction with the change rate so that the raw metal and the raw material in the chloride furnace are controlled. An apparatus for producing a metal powder, wherein the rate of chlorine reaction with chlorine gas is controlled. 12. The apparatus for producing a metal powder according to claim 11, further comprising weighing means for weighing the entire weight of the raw material hopper. 12. An apparatus for producing a metal powder according to claim 11, wherein said weighing means is a load cell. The apparatus for producing a metal powder according to claim 11, wherein the metal is nickel.