NICKEL POWDER PRODUCTION METHOD AND NICKEL POWDER PRODUCTION DEVICE

Abstract

Provided is a method with which it is possible to prevent equipment, such as piping and valves, used to discharge and recover a nickel powder-containing slurry from a high pressure reaction tank from being damaged and trapping the nickel powder therein and to enable continuous operation, thereby improving the productivity. This nickel powder production method comprises a step of reacting a nickel sulfate-amine complex solution with hydrogen gas under high pressure in a reaction tank, thereby obtaining a nickel powder slurry containing nickel powder. The method is characterized in that the nickel powder slurry is discharged and transferred through discharge piping from the reaction tank in which the nickel powder-containing slurry has been produced, and then a washing solution is supplied to the discharge piping at a predetermined pressure to wash the discharge piping.

Description

TECHNICAL FIELD

The present invention relates to a method of subjecting a nickel sulfate-amine complex solution to hydrogen reduction to obtain nickel powder, and more specifically, to a nickel powder production method and a nickel powder production device which are capable of stably discharging a nickel powder slurry produced in a reaction tank.

BACKGROUND ART

As a method for industrially producing nickel powder, there is a nickel powder production method in which a raw material containing nickel is dissolved in a sulfuric acid solution, a treatment of removing impurities contained in the raw material is performed, ammonia is then added to the obtained nickel sulfate solution to form nickel in the form of amine complex, and nickel in the nickel sulfate-amine complex solution is reduced by bringing the nickel sulfate-amine complex solution into contact with hydrogen gas, for example, at a high temperature and a high pressure around 150° C. to 250° C. and 2.5 MPa to 3.5 MPa to produce nickel powder (for example, Patent Document 1).

Such a method is a method by which a high quality nickel metal can be efficiently obtained with a compact facility; on the other hand, there is a problem in that continuous operation which is industrially advantageous is difficult to perform since reaction is performed using a high-pressure container.

That is, the raw material and hydrogen gas are relatively easily supplied to a high-temperature high-pressure reaction tank; on the other hand, when a discharge side is constantly opened to external air, an internal pressure of the reaction tank easily becomes equal to the external air, and reaction cannot be performed under a high pressure. For this reason, it is necessary to appropriately adjust the pressure inside the reaction tank while a balance between supply and discharge is maintained.

In the related art, as a process of performing continuous reaction under a high temperature and a high pressure, for example, a high pressure acid leaching (HPAL) process as described in Patent Document 2 is known in which nickel oxide ore is charged together with sulfuric acid in an autoclave, a valuable metal such as nickel contained in the ore in a trace amount is leached in a sulfuric acid solution by heating the autoclave to about 250° C., and the valuable metal is recovered.

In the HPAL process, a flash vessel (depressurization tank) and a flash valve (discharge valve) are provided at an ejection side of the autoclave (reaction tank), control, for example, as disclosed in Patent Document 3 or Patent Document 4 is performed, and opening and closing of the flash valve are repeated while the internal pressure of the reaction tank is managed, so that the continuous operation is executed.

Such a method using the flash vessel and the flash valve is an excellent method in which steam generated at the time of depressurization is recovered as energy and used again. However, it is not easy to apply the continuous operation using the reaction tank in a high-pressure state as illustrated in the HPAL process to a complexing reduction process of obtaining nickel powder by subjecting the aforementioned nickel sulfate-amine complex solution to hydrogen reduction.

The reason for this is that there is a problem in that, since metal of nickel powder to be produced by reaction is fine and hard, the metal of nickel powder easily wears out piping or a member attached to the piping such as a valve when the metal of nickel powder is discharged from the reaction tank and cost and time and effort for maintenance are largely required.

In particular, when the pressure is intended to be depressurized from the reaction tank to atmospheric pressure, a flow velocity of a nickel powder-containing slurry passing through the flash valve reaches a furious speed close to a velocity of sound, frictional force significantly increases, and further, the slurry is hit by an inner wall of the flash vessel when the slurry is ejected and recovered, so that damage occurs.

Further, in the complexing reduction process, since a liquid in the middle of the nickel powder being precipitated from the solution is discharged from the reaction tank in some cases, the liquid is precipitated also on the inner wall of the piping after discharging to cause clogging, or the liquid is precipitated inside a valve controlling discharging or the valve traps the nickel powder therein so that opening and closing of the valve cannot be performed.

For this reason, it is necessary to perform maintenance such as frequent disassembling and washing of piping and a valve, and thus the continuous operation for a long time is difficult to perform. Further, there is no industrially actual case of the continuous operation, batch reaction in which a liquid is replaced from the reaction tank with respect to each reaction is a mainstream in commercial production, and a problem of an improvement in productivity arises.

• Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2015-212411
• Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2005-350766
• Patent Document 3: Japanese Unexamined Patent Application, Publication No. 2010-59489
• Patent Document 4: Japanese Unexamined Patent Application, Publication No. 2014-240524

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

The present invention is proposed in view of such circumstances, and an object thereof is to provide a method capable of preventing equipment, such as piping and valves, used to discharge and recover a nickel powder-containing slurry from a high-pressure reaction tank from being damaged and trapping the nickel powder therein and enabling the continuous operation to improve productivity.

Means for Solving the Problems

The present inventor has conducted intensive studies, and as a result, found that the aforementioned problems can be solved by discharging and transferring a slurry containing nickel powder obtained in a reaction tank through discharge piping and then supplying a washing solution at a predetermined pressure to the discharge piping to perform a washing treatment, thereby completing the present invention.

(1) A first invention of the present invention is a nickel powder production method, the method including reacting a nickel sulfate-amine complex solution with hydrogen gas under a high pressure in a reaction tank to obtain a nickel powder slurry containing nickel powder, in which the nickel powder slurry is discharged and transferred through discharge piping from the reaction tank in which the slurry containing nickel powder is produced, and then a washing solution is supplied to the discharge piping at a predetermined pressure to wash the discharge piping.

(2) A second invention of the present invention is the nickel powder production method in the first invention, in which the washing solution is supplied to the discharge piping at a pressure lower than an internal pressure of the reaction tank by 0.2 MPa to 1.0 MPa.

(3) A third invention of the present invention is the nickel powder production method in the first or second invention, in which a filtrate obtained by subjecting the recovered nickel powder slurry to solid-liquid separation is used as the washing solution.

(4) A fourth invention of the present invention is a nickel powder production device in which a nickel sulfate-amine complex solution is reacted with hydrogen gas under a high pressure to obtain a nickel powder slurry containing nickel powder, the device including: a reaction tank in which a nickel sulfate-amine complex solution is reacted with hydrogen gas to produce nickel powder; a depressurization tank that depressurizes the nickel powder slurry discharged from the reaction tank to normal pressure; discharge piping for connecting the reaction tank and the depressurization tank and discharging the nickel powder slurry from the reaction tank to the depressurization tank; and washing piping that is connected to the discharge piping and supplies a washing solution to the discharge piping.

Effects of the Invention

According to the present invention, it is possible to prevent equipment, such as piping and valves, used to discharge and recover a nickel powder-containing slurry from a high-pressure reaction tank from being damaged and trapping the nickel powder therein. Accordingly, time and effort and cost for maintenance are reduced and continuous operation is enabled, so that productivity can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the flow of a nickel powder production method and is a diagram illustrating the flow of a solution or the like to various treatment tanks.

FIG. 2 is a diagram illustrating a configuration of a nickel powder production device.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. Incidentally, the present invention is not limited to the following embodiment, and various modifications can be made within the range that does not change the spirit of the present invention. Further, in the present specification, the description “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less” unless otherwise specified.

<<1. Nickel Powder Production Method>>

A nickel powder production method according to the present embodiment is a method of charging a nickel sulfate-amine complex solution in a reaction tank, and reducing nickel ions to nickel in the solution by the solution being brought into contact with hydrogen gas under pressure, thereby obtaining a nickel powder slurry containing nickel powder.

Specifically, in the production method, the nickel sulfate-amine complex solution is supplied to the reaction tank and the pressure of a gas phase part inside the reaction tank is adjusted by continuous supply of hydrogen gas while a temperature inside the reaction tank is maintained in a predetermined range, so that nickel ions in the nickel sulfate-amine complex solution is reduced to nickel under pressure. In the reaction tank, the nickel powder as seed crystals can be added together with the nickel sulfate-amine complex solution, and hydrogen reduction reaction is caused by supplying a mixed slurry of the nickel sulfate-amine complex solution and the nickel powder to the reaction tank, so that nickel produced by reduction is precipitated on the surface of the nickel powder as seed crystals.

According to such a method, it is possible to efficiently produce nickel powder having a high quality and an optimum shape by continuous operation.

(Regarding Hydrogen Reduction Reaction in Reaction Tank)

Specifically, FIG. 1 is a diagram illustrating the flow of a nickel powder production method and illustrates the flow of a solution or the like to various treatment tanks. As illustrated in FIG. 1, in the production method, first, a mixed slurry of a nickel sulfate-amine complex solution and nickel powder (nickel powder slurry) as seed crystals is supplied to a reaction tank. Then, hydrogen gas for reduction is continuously supplied to the reaction tank in which the mixed slurry of a nickel sulfate-amine complex solution and nickel powder as seed crystals is charged.

The nickel sulfate-amine complex solution is a solution containing nickel in the form of an amine complex, and can be obtained, for example, by adding ammonia gas or ammonia water (NH₄OH) to a nickel sulfate (NiSO₄) solution.

When the nickel sulfate-amine complex solution is produced, the concentration of ammonia to be added is not particularly limited, but for example, it is preferable to add ammonia to be 1.9 or more in a molar ratio with respect to the nickel concentration in the solution. According to this, it can be prevented that nickel in the solution becomes nickel hydroxide deposition without forming an amine complex.

As the nickel powder to be added as seed crystals, nickel powder with an average particle size of 0.1 μm to 300 μm is preferably used, and nickel powder with an average particle size of 10 μm to 200 μm is more preferably used. When the particle size of the nickel powder as seed crystals is less than 0.1 μm, the nickel powder to be obtained is too fine, and thus there is a possibility that the effect as seed crystals is not sufficiently exhibited. On the other hand, when the particle size of the nickel powder as seed crystals is more than 300 μm, the nickel powder is coarse, and thus the effect of suppressing abrasion of the facility is not obtainable and it is economically disadvantageous that such coarse nickel powder is prepared.

As the nickel powder as seed crystals, commercially available nickel powder can be used, and nickel powder chemically precipitated by a known method can be classified and used. Further, produced nickel powder can also be repeatedly used. Incidentally, the nickel powder as seed crystals is continuously supplied together with the nickel sulfate-amine complex solution as a raw material to the reaction tank by a supply device such as a slurry pump.

The temperature inside the reaction tank, that is, the reaction temperature of the hydrogen reduction reaction is set to a range of 150° C. to 250° C. Further, the temperature is set preferably to 150° C. to 185° C. The temperature inside the reaction tank is adjusted, for example, by heating using a heating device or the like, and is maintained. When the reaction temperature is lower than 150° C., reduction efficiency of nickel ions in the nickel sulfate-amine complex solution is degraded. On the other hand, even when the reaction temperature is higher than 250° C., the reduction reaction is not affected, and instead, the loss of hydrogen gas to be supplied to the reaction tank and the loss of thermal energy occur.

In this production method, in a state where the temperature of the reaction tank is maintained at 150° C. to 250° C., hydrogen gas is continuously supplied to the gas phase part at which the solution is not filled in the reaction tank. By supplying the hydrogen gas in this way, the pressure of the gas phase part is set, for example, to a range of 2.5 MPa to 3.5 MPa. Specifically, hydrogen gas is directly blown to the gas phase part in the reaction tank, for example, from a cylinder or the like, or is blown into the slurry.

Regarding the pressure of the gas phase part, when the internal pressure is less than 2.5 MPa, the efficiency of reduction reaction of nickel ions is degraded. On the other hand, even by setting a high pressure condition such that the internal pressure is more than 3.5 MPa, the reduction reaction is not affected, and instead, the loss of the supplied hydrogen gas increases.

As described above, in the nickel powder production method according to the present embodiment, hydrogen gas is blown to the mixed slurry of a nickel sulfate-amine complex solution and nickel powder as seed crystals to adjust the pressure to a predetermined pressure, so that nickel ions contained in the nickel sulfate-amine complex solution is reduced to nickel under pressure. According to this, nickel produced by reduction is precipitated on the surface of the nickel powder supplied as seed crystals so that reduced nickel powder can be obtained.

(Regarding Extraction of Nickel Powder Slurry)

Next, the nickel powder slurry containing nickel powder that is a reacted slurry produced in the reaction tank is discharged and extracted from the reaction tank to a depressurization tank. The nickel powder slurry is produced by reduction reaction in the reaction tank under pressure and has an extremely high pressure. Therefore, by discharging and transferring such a nickel powder slurry to the depressurization tank, the pressure is gradually reduced in the depressurization tank, and for example, is set to the same pressure as atmospheric pressure.

The reaction tank and the depressurization tank are connected by piping (discharge piping) for transferring the nickel powder slurry, and the nickel powder slurry ejected from the reaction tank is discharged to the depressurization tank through the discharge piping.

Herein, in the nickel powder production method according to the present embodiment, the nickel powder slurry produced in the reaction tank is discharged and transferred through the discharge piping, and then a washing solution is supplied at a predetermined pressure to the discharge piping to wash the inside of the discharge piping or a valve provided in the discharge piping. According to such a method, it is possible to wash and remove nickel powder and other precipitates precipitated during the process of discharging the nickel powder slurry, nickel powder trapped in the valve, and the like, and it is possible to effectively prevent abrasion and clogging of the piping and the valves caused by the precipitated nickel powder, or the like. According to this, time and effort and cost for maintenance can be effectively reduced and the continuous operation is enabled, so that productivity can be improved.

Incidentally, washing of the discharge piping using the washing solution will be described in detail together with the description of the configuration of a production device described later.

(Regarding Recovery of Nickel Powder from Nickel Powder Slurry)

When the pressure of the nickel powder slurry is reduced in the depressurization tank to atmospheric pressure, next, the nickel powder slurry is extracted from the depressurization tank and transferred to a solid-liquid separation tank.

In the solid-liquid separation tank, the nickel powder slurry is subjected to a solid-liquid separation treatment based on a known method, so that the nickel powder slurry is separated into nickel powder and a filtrate to recover nickel powder. Incidentally, although specifically described later, the filtrate separated herein can be reused as the washing solution of the discharge piping in order to transfer the nickel powder slurry from reaction tank to the depressurization tank.

<<2. Nickel Powder Production Device>>

Next, a production device for performing the nickel powder production method will be described in more detail. The nickel powder production method according to the present embodiment can be performed using a nickel powder production device to be described specifically below.

FIG. 2 is a diagram illustrating an example of the configuration of a nickel powder production device. This nickel powder production device 1 is a production device in which a nickel sulfate-amine complex solution is reacted with hydrogen gas under a high pressure to obtain a nickel powder slurry containing nickel powder.

Specifically, a nickel powder production device 1 (hereinafter, simply also referred to as “production device 1”) includes a reaction tank 11 in which a nickel sulfate-amine complex solution is reacted with hydrogen gas, a depressurization tank 12 that depressurizes the nickel powder slurry produced in the reaction tank 11 to normal pressure, and discharge piping 13 that connects the reaction tank 11 and the depressurization tank 12 and discharges and transfers the nickel powder slurry. Further, this production device 1 is provided with washing piping 14 that is connected to the discharge piping 13 and supplies a washing solution to the discharge piping 13.

As described above, in the nickel powder production device 1, by providing the washing piping 14 connected to the discharge piping 13, the washing solution is supplied to the discharge piping 13 so that it is possible to effectively wash the inside of the discharge piping 13 or a valve and the like provided in the discharge piping 13, and thus operation failure is prevented to enable stable operation and improvement in production efficiency can be achieved.

[Reaction Tank]

The reaction tank 11 is a place in which the nickel sulfate-amine complex solution is reacted with hydrogen gas. In this reaction tank 11, the reaction in which nickel ions in the nickel sulfate-amine complex solution are reduced to produce nickel powder, is caused by the supplied hydrogen gas. For example, hydrogen reduction reaction is caused by adjusting and maintaining the pressure of the gas phase part inside the reaction tank 11 to a range of 2.5 MPa to 3.5 MPa by continuous supply of hydrogen gas.

The reaction tank 11 is not particularly limited as long as it is a pressurized reaction tank which can be adjusted to a predetermined temperature condition and a predetermined pressure condition and maintained. For example, an autoclave or the like can be used. The material of the autoclave is not particularly limited, and for example, an autoclave made of austenitic stainless steel such as SUS316L or SUS304L can be used. Further, the size thereof can also be appropriately set depending on a treated amount of the mixed slurry of a nickel sulfate-amine complex solution as a raw material and nickel powder as seed crystals, or the like.

The reaction tank 11 is provided with at least a charging port 11A in which the nickel sulfate-amine complex solution as a raw material is charged, a hydrogen gas supply port 11B to which hydrogen gas for hydrogen reduction is supplied, and an ejection port 11C that ejects (discharges) a slurry containing nickel powder produced by hydrogen reduction reaction (nickel powder slurry).

(Charging Port)

The charging port 11A is connected to charging piping (not illustrated), and is connected, for example, to a storage tank for the nickel sulfate-amine complex solution by the charging piping. In the reaction tank 11, the nickel sulfate-amine complex solution transferred through the charging piping is charged in the inside through the charging port 11A. Incidentally, the raw material charged from the charging port 11A may be the nickel sulfate-amine complex solution alone or may be a mixed slurry obtained by mixing nickel powder as seed crystals in the complex solution in advance.

(Hydrogen Gas Supply Port)

The hydrogen gas supply port 11B is connected to hydrogen gas supply piping 21, and is connected, for example, to a hydrogen gas supply device such as a hydrogen gas cylinder by the hydrogen gas supply piping 21. In the reaction tank 11, hydrogen gas supplied through the hydrogen gas supply piping 21 is supplied to the inside through the hydrogen gas supply port 11B.

Herein, the hydrogen gas supply piping 21 is, as described above, piping that is connected to a hydrogen gas cylinder or the like and is used for supplying hydrogen gas into the reaction tank 11. In this hydrogen gas supply piping 21, a gas supply valve 21a is provided at a predetermined position and the supply of hydrogen gas is controlled. Incidentally, the gas supply valve 21a may be an ON/OFF valve that controls ON (with supply) and OFF (without supply) of the supply of hydrogen gas, or may be a control valve that can control the amount of hydrogen gas supplied.

(Ejection Port)

The ejection port 11C is an ejection port for ejecting and discharging the nickel powder slurry produced by hydrogen reduction reaction in the reaction tank 11 from the reaction tank 11. The discharge piping 13 described later is connected to the ejection port 11C, and the nickel powder slurry ejected from the ejection port 11C is discharged and transferred to the depressurization tank 12 through the discharge piping 13.

[Depressurization Tank]

The depressurization tank 12 is a tank for depressurizing the nickel powder slurry produced in the reaction tank 11, for example, to normal pressure. The depressurization tank 12 includes, for example, a flash tank (flash vessel).

The depressurization tank 12 is provided with a charging port 12A for charging the nickel powder slurry discharged from the reaction tank 11 in the inside at a predetermined position of the top board thereof. The charging port 12A is connected to the discharge piping 13 described later, and the nickel powder slurry from the reaction tank 11 is transferred through the discharge piping 13 and charged in the inside of the depressurization tank 12 through the charging port 12A.

[Discharge Piping]

The discharge piping 13 is piping for connecting the reaction tank 11 and the depressurization tank 12 and discharging and transferring the nickel powder slurry produced in the reaction tank 11 to the depressurization tank 12. The nickel powder slurry discharged from the reaction tank 11 and passing through the discharge piping 13 is in a state of maintaining a high pressure, and the nickel powder slurry flows in the discharge piping 13 at a flow velocity close to a velocity of sound under the high pressure and is charged in the depressurization tank 12.

The discharge piping 13 is provided with at least an ejection valve 13a positioned in the vicinity of the reaction tank 11 side and a flash valve 13b positioned in the vicinity of the depressurization tank 12.

(Ejection Valve)

The ejection valve 13a is a control valve for controlling the amount of the nickel powder slurry ejected from the ejection port 11C of the reaction tank 11, that is, the amount of the nickel powder slurry transferred in the discharge piping 13. The ejection valve 13a may be an ON/OFF valve that controls ON (with transfer) and OFF (without transfer) of the transfer of the nickel powder slurry, or may be a control valve that can control the amount of the nickel powder slurry transferred.

(Flash Valve)

The flash valve 13b is a control valve for controlling charging the nickel powder slurry when the nickel powder slurry transferred through the inside of the discharge piping 13 is charged in the depressurization tank 12. When the nickel powder slurry is charged in the depressurization tank 12 by opening and closing the flash valve 13b while the internal pressure of the reaction tank 11 is appropriately managed, the continuous operation can be performed. The flash valve 13b may be an ON/OFF valve that controls ON (with charge) and OFF (without charge) of the charging of the nickel powder slurry to the depressurization tank 12, or may be a control valve that can control the amount of the nickel powder slurry charged.

[Washing Piping]

The washing piping 14 is piping that is connected to the discharge piping 13 and supplies a washing solution to the discharge piping 13. The washing piping 14 is connected, for example, to the discharge piping 13 while branching is provided at a predetermined site of the discharge piping 13 (for example, “P” in FIG. 2). A connection site on the discharge piping 13 with the washing piping 14 is not particularly limited, but can be a site in the vicinity of the ejection valve 13a or in the vicinity of the flash valve 13b, and can be an intermediate position of the discharge piping 13 connecting the reaction tank 11 and the depressurization tank 12.

The washing piping 14 is provided with a washing solution supply valve 14a. The washing solution supply valve 14a is provided in the vicinity of a washing solution tank storing a washing solution to be supplied to the discharge piping 13 through the washing piping 14, or the like and controls the supply of the washing solution. The washing solution supply valve 14a may be an ON/OFF valve that controls ON (with supply) and OFF (without supply) of the supply of the washing solution through the washing piping 14, or may be a control valve that can control the amount of the washing solution transferred.

The nickel powder production device 1 according to the present embodiment includes, as described above, the washing piping 14 connected to the discharge piping 13 for discharging the nickel powder slurry from the reaction tank 11, and by supplying the washing solution to the discharge piping 13 through the washing piping 14, the inside of the discharge piping 13 or a valve (the ejection valve 13a or the flash valve 13b) and the like provided in the discharge piping 1 can be washed. According to this, the nickel powder and other precipitates precipitated to the discharge piping 13, the flash valve 13b, and the like can be washed and removed, and for example, clogging or trapping of the flash valve 13b can be effectively prevented.

The washing solution is not particularly limited, and for example, water (washing water) or the like can be used. Further, other than this, drain generated after heat is recovered from steam generated when pressure is depressurized to normal pressure in the depressurization tank can be used, and further, a filtrate obtained by subjecting the recovered nickel powder slurry to solid-liquid separation by a known method may be reused.

Further, inert gas supply piping 22 for supplying an inert gas such as nitrogen gas or argon gas is connected to the washing piping 14 at a predetermined position. The inert gas such as nitrogen gas is used for adjusting the internal pressure of the washing piping 14 and the discharge piping 13 to adjust the pressure when the washing solution is supplied from the washing piping 14 to the discharge piping 13. The inert gas supply piping 22 is connected, for example, to a gas cylinder for nitrogen gas or the like and is provided with a gas supply valve 22a for adjusting the flow rate of gas at a predetermined position. The pressure of the inert gas is controlled by the gas supply valve 22a and the inert gas is supplied to the washing piping 14 through the inert gas supply piping 22.

Incidentally, the pressure of the washing solution is not limited to be controlled by the supply of the inert gas as described above, but for example, a liquid feeding pump may be connected to the washing piping 14 and the washing solution in the washing piping 14 may be pressurized. Further, by the aforementioned inert gas supply piping 22 being connected directly to a washing solution storage tank connected with the washing piping 14, the inert gas may be supplied into the storage tank, so that the washing solution can be supplied at a predetermined pressure.

(Supply of Washing Solution Through Washing Piping)

Herein, it is preferable to supply, to the washing piping 14, the washing solution at a pressure lower than the internal pressure of the reaction tank 11 by a range of 0.2 MPa to 1.0 MPa. Further, more preferably, the pressure is set to be lower than the internal pressure of the reaction tank 11 by a range of 0.5 MPa to 1.0 MPa. Incidentally, the pressure of the washing solution is, as described above, controlled by the gas supply valve 22a provided in the washing piping 14. Specifically, since the internal pressure in the reaction tank 11 is maintained in a range of 2.5 MPa to 3.5 MPa by the supply of hydrogen gas, the washing solution is supplied through the washing piping 14 at a pressure lower than the internal pressure of the reaction tank 11 by a range of 0.2 MPa to 1.0 MPa, for example, at a pressure of 2.0 MPa to 2.5 MPa.

When a difference between the supply pressure of the washing solution and the internal pressure of the reaction tank 11 is less than 0.2 MPa, the removal force by the flow velocity at the time of supplying the washing solution becomes small and thus there is possibility that sufficient washing cannot be performed. On the other hand, even when the difference with the internal pressure of the reaction tank 11 is larger than 1.0 MPa, the washing effect is not further improved, and instead, there is possibility that piping and valves are worn out or damaged by the nickel powder removed by washing, or the like.

Examples

Hereinafter, the present invention will be described in more detail by means of Examples of the present invention, but the present invention is not limited to the following Examples at all.

Example 1

Nickel powder was produced using the device as schematically illustrated in FIG. 2. That is, an autoclave made of austenitic stainless steel such as SUS316L or SUS304L with a capacity of 200 L was used as a reaction tank, and hydrogen gas was continuously supplied to a nickel sulfate-amine complex solution to cause hydrogen reduction reaction. Further, a flash tank with a capacity of 1000 L was used as a depressurization tank, and a slurry of the nickel powder produced in the reaction tank was charged in the flash tank and was depressurized to atmospheric pressure. Then, the reaction tank and the depressurization tank were connected by discharge piping with an inner diameter of 10 mm. Incidentally, an ejection valve was provided at an ejection port of the reaction tank, a flash valve for controlling the charging of the nickel powder slurry into the depressurization tank was provided at a ceiling part of the depressurization tank, and charging control was performed by opening and closing the valve.

Further, in the production device, washing piping was connected while branching was provided in the middle of the discharge piping, and a washing solution was enabled to be supplied to the discharge piping through the washing piping. Incidentally, the washing piping was connected while branching was provided at the side close to the reaction tank in the discharge piping. Further, piping for industrial water was connected to the washing piping, and the industrial water as the washing solution was supplied under the supply control by a washing solution supply valve. Furthermore, supply piping supplying nitrogen gas as an inert gas was connected to the washing piping, and the nitrogen gas was enabled to be supplied under the supply control by a gas supply valve.

The nickel sulfate-amine complex solution with a nickel concentration of 82.5 g/L was supplied at a flow rate of 1.0 L/min to the reaction tank by using such a production device. Further, a slurry containing 33 g/L of nickel powder with a diameter of 75 μm or less as seed crystals was supplied at a flow rate of 0.5 L/min.

Further, the internal temperature of the reaction tank was maintained at 185° C., and the pressure inside the reaction tank was adjusted to a range of 2.5 MPa to 3.5 MPa by blowing hydrogen gas from a cylinder. Incidentally, in order to maintain the amount of the solution in the reaction tank to be 90 L, the flash valve attached to the top part of the depressurization tank was intermittently opened and closed to extract the nickel powder slurry into the depressurization tank through the discharge piping.

After the nickel powder was extracted, the ejection valve of the reaction tank and the flash valve were sequentially closed in this order. Next, the washing solution supply valve Provided in the washing piping was opened to supply 4 L of washing solution (industrial water) into the discharge piping through the washing piping, and then the washing solution supply valve was closed. Incidentally, 1 to 2 L space was allowed to remain inside the washing piping and the discharge piping. Then, the gas supply valve was opened to adjust the internal pressure of the washing piping and the discharge piping to a range of 2.0 MPa to 2.5 MPa that is lower than the internal pressure of the reaction tank by 0.5 MPa to 1.0 MPa, and the washing solution was supplied to the discharge piping at such a pressure.

The discharge piping and the flash valve were washed by opening the flash valve under the supply of the washing solution through the washing piping. After the completion of washing, the ejection valve of the reaction tank and the flash valve were opened, and discharging of the nickel powder slurry from the reaction tank to the depressurization tank was repeated.

Although the operation as described above was continued for 6 hours, abrasion, or adhering or trapping of the nickel powder or the like in the flash valve and the discharge piping did not occur, and it was possible to stably perform extraction of the nickel powder slurry from the reaction tank to the depressurization tank without any trouble.

Example 2

The operation was performed using the same production device as in Example 1, except that the washing piping was connected to a 350 L washing solution storage tank, and nitrogen gas supply piping was connected directly to the washing solution storage tank to enable nitrogen gas to be supplied.

As the washing solution, 300 L of filtrate obtained by subjecting the nickel powder slurry recovered from the depressurization tank by the operation in Example 1 to solid-liquid separation using Nutsche was used. Incidentally, the filtrate was stored in the washing solution storage tank and used as the washing solution. Further, nitrogen gas was supplied to the washing solution storage tank to adjust the internal pressure of the washing solution storage tank to a range of 2.0 MPa to 2.5 MPa, the washing solution supply valve was controlled such that 4 L of the washing solution was ejected at one time, and the washing solution was supplied to the discharge piping through the washing piping.

Although the operation as described above was continued for 7 hours, abrasion, or adhering or trapping of the nickel powder or the like in the flash valve and the discharge piping did not occur, and it was possible to stably perform extraction of the nickel powder slurry from the reaction tank to the depressurization tank without any trouble.

Comparative Example 1

The operation was performed using the same production device as in Example 1, except that the washing piping was not provided. That is, the operation was performed using the production device not including the mechanism of supplying the washing solution to the discharge piping at a predetermined pressure.

Although the operation was performed for 6 hours under the same condition as in Example 1, after 1 hour from the operation start, opening and closing of the flash valve were not able to be controlled, an excessive amount of the nickel powder slurry was discharged and transferred from the reaction tank to the depressurization tank, so that the amount of the solution in the reaction tank was not able to be maintained to 90 L and the operation was stopped.

After the operation stop, when the flash valve was observed, the nickel precipitate or fine nickel powder was precipitated or trapped in the valve.

EXPLANATION OF REFERENCE NUMERALS

• 1 NICKEL POWDER PRODUCTION DEVICE
• 11 REACTION TANK
• 11A CHARGING PORT
• 11B HYDROGEN GAS SUPPLY PORT
• 11C EJECTION PORT
• 12 DEPRESSURIZATION TANK
• 12A CHARGING PORT
• 13 DISCHARGE PIPING
• 13a EJECTION VALVE
• 13b FLASH VALVE
• 14 WASHING PIPING
• 14a WASHING SOLUTION SUPPLY VALVE
• 21 HYDROGEN GAS SUPPLY PIPING
• 21a GAS SUPPLY VALVE
• 22 INERT GAS SUPPLY PIPING
• 22a GAS SUPPLY VALVE

Claims

1. A nickel powder production method, the method comprising reacting a nickel sulfate-amine complex solution with hydrogen gas under a high pressure in a reaction tank to obtain a nickel powder slurry containing nickel powder, wherein

the nickel powder slurry is discharged and transferred through discharge piping from the reaction tank in which the slurry containing nickel powder is produced, and then a washing solution is supplied to the discharge piping at a predetermined pressure to wash the discharge piping.

2. The nickel powder production method according to claim 1, wherein the washing solution is supplied to the discharge piping at a pressure lower than an internal pressure of the reaction tank by 0.2 MPa to 1.0 MPa.

3. The nickel powder production method according to claim 1, wherein a filtrate obtained by subjecting the recovered nickel powder slurry to solid-liquid separation is used as the washing solution.

4. A nickel powder production device in which a nickel sulfate-amine complex solution is reacted with hydrogen gas under a high pressure to obtain a nickel powder slurry containing nickel powder, the device comprising:

a reaction tank in which a nickel sulfate-amine complex solution is reacted with hydrogen gas to produce nickel powder;

a depressurization tank that depressurizes the nickel powder slurry discharged from the reaction tank to normal pressure;

discharge piping for connecting the reaction tank and the depressurization tank and discharging the nickel powder slurry from the reaction tank to the depressurization tank; and

washing piping that is connected to the discharge piping and supplies a washing solution to the discharge piping.

5. The nickel powder production method according to claim 2, wherein a filtrate obtained by subjecting the recovered nickel powder slurry to solid-liquid separation is used as the washing solution.