JP2018154883A - Method for producing a nickel powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nickel powder allowing for efficiently obtaining a nickel powder while continuously hydrogen-reducing a nickel sulfate ammine complex solution with high rate of reduction.SOLUTION: A method for producing a nickel powder is characterized by preparing a dispersant-containing mixed solution by adding, to a nickel sulfate ammine complex solution including ammonium sulfate, polyacrylic acid in an amount for a concentration of 0.01 g/L or greater and 10 g/L or smaller with respect to the nickel sulfate ammine complex solution, next supplying the dispersant-containing mixed solution into a reaction vessel and contacting it with a hydrogen gas that has been blown into the reaction vessel, producing a nickel powder through a reduction treatment of nickel complex ions in the nickel sulfate ammine complex solution, and discharging an obtained slurry including a nickel powder to an outside of the reaction vessel.SELECTED DRAWING: None

Description

  The present invention relates to a method for obtaining nickel powder by reducing nickel ions by bringing hydrogen gas into contact with a nickel sulfate ammine complex solution containing ammonium sulfate under high temperature and pressure.

  As a method for industrially producing nickel powder using a hydrometallurgical process, as shown in Patent Document 1, after dissolving a nickel-containing raw material in a sulfuric acid solution, a purified solution for removing impurities contained in the solution Through the process, ammonia is added to the obtained nickel sulfate solution to form a nickel ammine complex, and then this nickel sulfate ammine complex solution is placed in a high-temperature and high-pressure reaction vessel such as an autoclave, and hydrogen gas is supplied to produce sulfuric acid. A method for producing nickel powder by reducing nickel complex ions in a nickel ammine complex solution is known.

Since the above-described production method is carried out by a reaction at a high temperature and a high pressure, a production method using a batch method is often used from the viewpoint of ease of handling and apparatus cost.
However, in the batch-type manufacturing method, a reaction vessel is opened, a solution is charged, and the temperature is increased by sealing, the temperature and pressure are controlled, hydrogen gas is blown in to reduce, cool, and the reaction product is taken out. It was necessary to perform the operation step by step, requiring a lot of labor and time, and the operating rate was low, which was not industrially efficient.

  Further, in the batch reaction as described above, the influence of temperature change during heating before and after the reaction or during temperature reduction cannot be ignored, and during this time, non-uniform precipitation called “scaling” and particle size variation may occur. Coarse nickel powder is likely to be mixed, but if non-uniform nickel powder is generated, the equipment is likely to be worn or clogged during handling, resulting in a reduction in operating rate. For this reason, the effort to remove the scaling has increased, and it has been difficult to keep the product quality constant while maintaining the equipment operation rate.

Therefore, in order to prevent scaling and obtain uniform nickel powder, seed crystals (seed crystals) are added before hydrogen reduction, and dispersants such as polyacrylic acid and its salts are added to grow seeds. Attempts have been made to ensure that there is no uneven distribution.
However, there is a problem that the dispersant has an appropriate range of use, and if the addition amount is inappropriate, the reaction rate (reduction rate) for reducing nickel is lowered.

In addition, seed crystals are often manufactured by repeatedly using a part of the product or by providing a separate dedicated process, and there are problems such as an increase in the amount of work in the system due to repetition and an increase in equipment costs and labor. there were.
Thus, it was not easy to efficiently obtain uniform nickel powder by continuous hydrogen reduction.

JP2015-140480A

  The present invention intends to provide a method for producing nickel powder that efficiently obtains nickel powder while continuously hydrogen-reducing the ammine sulfate complex solution with a high reduction rate.

  1st invention of this invention which solves said subject is the quantity used as the density | concentration of 0.01 g / L or more and 10 g / L or less with respect to the said nickel sulfate ammine complex solution in the nickel sulfate ammine complex solution containing ammonium sulfate. A mixed solution containing a dispersant containing polyacrylic acid as a dispersant is prepared, and then the mixed solution containing the dispersant is supplied into the reaction vessel and continuously into the hydrogen gas blown into the reaction vessel. The nickel, wherein the nickel complex ions in the nickel sulfate ammine complex solution are subjected to reduction treatment to produce nickel powder, and then the resulting slurry containing the nickel powder is discharged out of the reaction vessel. It is a manufacturing method of powder.

  According to a second aspect of the present invention, in the reduction treatment according to the first aspect of the present invention, hydrogen gas is introduced into the reaction vessel so that the time for contacting the nickel sulfate ammine complex solution with hydrogen gas is 5 minutes to 120 minutes. The nickel powder manufacturing method is characterized in that, while blowing, the mixed solution containing a dispersant is supplied into the reaction vessel and discharged out of the reaction vessel.

  The third invention of the present invention is that the reduction treatment in the first and second inventions is performed under a pressure in the range of 2.5 to 3.5 MPa and maintained in a temperature range of 150 to 185 ° C. It is the manufacturing method of the nickel powder characterized.

  According to the present invention, it is possible to perform a reduction process while suppressing scaling and non-uniform nucleation that occur during the reduction process, and nickel powder can be obtained efficiently and at a high reduction rate.

In the conventional process of adding a seed crystal to promote the reaction, a process for manufacturing the seed crystal is separately required, which is expensive.
In contrast to the above-described production method using seed crystals, the method of the present invention uses a polyacrylic acid as a dispersing agent in the form of a polyacrylic acid solution or a polyacrylate, and adds a predetermined amount thereof to a nickel complex solution to produce hydrogen. It has been found that fine nickel powder that has been reduced by hydrogen gas and precipitated in a solution by blowing gas can be used as a seed crystal. Therefore, the present invention is a simple method that can omit the step of producing the seed crystal, is simple and helps to reduce the cost, and is an efficient nickel powder production method.

The present invention continuously supplies a mixed solution containing a dispersant formed by adding a dispersant to a nickel sulfate ammine complex solution containing ammonium sulfate into a pressure vessel, and hydrogen gas blown into the reaction vessel. By making contact, nickel powder that acts as a seed crystal is produced from the solution using the reducing power of hydrogen, and the nickel powder is further grown and continuously discharged from the pressurized container.
Hereafter, the manufacturing method of the nickel powder of this invention is demonstrated.

The nickel sulfate ammine complex solution used in the present invention is not particularly limited, but one or a mixture selected from nickel and cobalt mixed sulfide, crude nickel sulfate, nickel oxide, nickel hydroxide, nickel carbonate, nickel powder and the like. By subjecting nickel-containing materials, such as industrial intermediates, to nickel leaching solution (solution containing nickel) obtained by dissolving with sulfuric acid or ammonia, and subjecting it to liquid purification processes such as solvent extraction, ion exchange, and neutralization. A solution obtained by adding ammonia to a solution obtained by removing impurity elements from the solution to form a nickel sulfate ammine complex solution is suitable.
Further, ammonium sulfate is contained, and the ammonium sulfate concentration is preferably in the range of 10 to 500 g / L. If the concentration exceeds 500 g / L, the solubility is exceeded and crystals are deposited. Moreover, since ammonium sulfate is newly produced | generated by reaction, it is difficult to achieve less than 10 g / L.

  In the present invention, a dispersant is added to such a nickel sulfate ammine complex solution in order to disperse the nickel powder that has been reduced by hydrogen gas and deposited in the complex solution. The dispersing agent is not particularly limited as long as it is polyacrylic acid or a polyacrylic acid salt that becomes a polyacrylic acid source in the liquid, but sodium polyacrylate is suitable as an industrially available material.

The amount of dispersant added is such that the polyacrylic acid and its salt are added in a concentration of 0.01 g / L to 10 g / L with respect to the amount of nickel sulfate ammine complex solution. To do.
If the concentration of polyacrylic acid is less than 0.01 g / L, the amount of the dispersant is too small to obtain a seed crystal of nickel powder having an appropriate particle size. Since the reduction rate (reaction rate) decreases, it is not suitable. On the other hand, even if the polyacrylic acid concentration exceeds 10 g / L, there is no effect and excessive addition occurs.

  Next, reaction of a high-pressure and high-pressure vessel such as an autoclave in which internal pressure is controlled by hydrogen gas is performed using a mixed solution containing a dispersant formed by adding the dispersant to a nickel sulfate ammine complex solution containing ammonium sulfate as a reaction vessel. The tank is continuously charged, and a liquid phase part and a gas phase part occupied by the mixed solution containing the dispersant are formed in the reaction tank.

  After that, in the mixed solution containing the dispersant in the reaction vessel continuously charged, the nickel complex ions contained in the nickel sulfate ammine complex solution are reduced by the blown-in hydrogen gas whose internal pressure is controlled. Then, using the deposited fine crystals as seeds, nickel is further deposited thereon to obtain a grown nickel powder, which is continuously discharged.

Further, in the present invention, the supply amount of the mixed solution containing the dispersing agent into the reaction vessel so that the reaction time in the reduction treatment in which hydrogen gas is blown to reduce the nickel complex ions is maintained between 5 minutes and 120 minutes. And the amount of discharge to the outside of the reaction vessel is adjusted.
When the reaction time is shorter than 5 minutes, the reduction reaction hardly proceeds and nickel powder cannot be obtained. On the other hand, even if it is subjected to a reduction reaction for a long time exceeding 120 minutes, there is no change, and the amount of the remaining liquid increases, which is not preferable because the apparatus becomes large.
Thus, in the present invention, since the reduction is performed by continuous treatment, the growth of nickel powder can be stably controlled by maintaining the reaction time within the above range.

  Moreover, the reaction temperature at this time has the preferable range of 150 degreeC or more and 185 degrees C or less. If it is less than 150 degreeC, reduction efficiency will fall, and even if it exceeds 185 degreeC, there is no influence on reaction, rather, since loss, such as a heat energy, increases, it is not suitable.

Furthermore, it is preferable to maintain the pressure in the gas phase part of the reaction tank during the reaction in the range of 2.5 to 3.5 MPa. If it is less than 2.5 MPa, the reaction efficiency decreases, and if it exceeds 3.5 MPa, there is no influence on the reaction, and the loss of hydrogen gas increases.
By the reduction treatment accompanied by precipitation of nickel under the above conditions, nickel powder that can be used as a seed crystal is produced by the blown-in hydrogen gas itself, and nickel powder that grows around the seed is obtained.

  The nickel powder produced as described above can be used, for example, as a nickel paste, which is an internal constituent material of a multilayer ceramic capacitor. In addition, the particles are grown by repeating the above hydrogen reduction, and high purity and suitable for handling. Metal such as uniform nickel briquette can be produced.

  The present invention will be further described below using examples.

  In a pressure vessel (autoclave) with a capacity of 3 L, an amount corresponding to an ammonium sulfate concentration of 200 g / L, a nickel ammine complex solution corresponding to a nickel concentration of 55 g / L, and a polyacrylic acid concentration of 5 g / L 1 L of a mixed solution containing a dispersant mixed with sodium polyacrylate was put in, and the temperature was maintained at 185 ° C., and hydrogen gas was started to be blown so that the internal pressure of the pressurized container (pressure in the gas phase) was maintained at 3.5 MPa. It was. At the same time, a liquid having the same composition as above was supplied at a rate of 16.7 ml per minute so that the same amount of liquid was discharged from the pressurized container. That is, the reaction time in the pressurized container is 1 hour.

If the ratio of the amount of nickel actually reduced to the amount of nickel that can be theoretically reduced by the amount of hydrogen gas supplied is defined as the nickel reaction rate, the nickel reaction rate is 95%, and an efficient reaction is achieved. It was.
The produced particle diameter of the obtained particles was 14 μm when expressed by D50 (median diameter), which is the particle diameter of 50% cumulative distribution, and there was no problem of blocking the pipe.

(Comparative Example 1)
A mixed solution having the same composition as in Example 1 was supplied and discharged at a flow rate of 16.7 ml per minute, except that the same pressurized container as in Example 1 did not contain polyacrylic acid.

  The reaction rate of nickel was only 38%, and the output particle diameter of the obtained particles was excessively coarse with a D50 of 68 μm.

The above results are summarized in Table 1.
As shown in Table 1, it was confirmed that nickel powder could be produced stably and continuously with high reaction efficiency by using the method of the present invention.

Claims (3)

A mixed solution containing a dispersant containing, in a nickel sulfate ammine complex solution containing ammonium sulfate, polyacrylic acid in an amount of 0.01 g / L or more and 10 g / L or less with respect to the nickel sulfate ammine complex solution as a dispersant. Make
Next, the mixed solution containing the dispersant is supplied into a reaction vessel, and continuously contacted with the hydrogen gas blown into the reaction vessel to reduce the nickel complex ions in the nickel sulfate ammine complex solution. After producing | generating nickel powder, the slurry containing the obtained nickel powder is discharged | emitted out of the said reaction container, The manufacturing method of the nickel powder characterized by the above-mentioned.   Hydrogen gas is blown into the reaction vessel so that the time during which the nickel sulfate ammine complex solution is brought into contact with hydrogen gas in the reduction treatment is 5 minutes to 120 minutes, and the mixed solution containing the dispersant is placed in the reaction vessel. The nickel powder production method according to claim 1, wherein the nickel powder is supplied to the reactor and discharged out of the reaction vessel.   The method for producing nickel powder according to claim 1 or 2, wherein the reduction treatment is performed while maintaining a temperature range of 150 to 185 ° C under a pressure in a range of 2.5 to 3.5 MPa. .