AU2017283345B2 - Nickel powder production method and nickel powder production device - Google Patents

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-ammine 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

NICKEL POWDER PRODUCTION METHOD AND NICKEL POWDER PRODUCTION DEVICE TECHNICAL FIELD

The present invention relates to a method of subjecting a

nickel sulfate-ammine 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

ammine complex, and nickel in the nickel sulfate-ammine

complex solution is reduced by bringing the nickel sulfate

ammine 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 2500C, 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-ammine 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

The present invention is proposed in view of such

circumstances, and seeks 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.

The present inventor has conducted intensive studies, and

as a result, found that the aforementioned problems may be

addressed 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) According to one aspect a first invention of the

present invention is a nickel powder production method, the

method including reacting a nickel sulfate-ammine 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) According to another aspect 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) According to another aspect 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) According to another aspect a fourth invention of the

present invention is a nickel powder production device in

which a nickel sulfate-ammine 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-ammine 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.

According to another aspect there is provided a nickel

powder production method, the method comprising reacting a

nickel sulfate-ammine 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 to a depressurization tank that

6A

depressurizes the nickel powder slurry to normal pressure, and

then water, drain generated after heat is recovered from steam

generated when pressure is depressurized to normal pressure in

the depressurization tank, or a filtrate obtained by

subjecting the recovered nickel powder slurry to solid-liquid

separation is supplied as a washing solution to the discharge

piping at a predetermined pressure of 2.0 MPa to 2.5 MPa to

wash the discharge piping.

According to another aspect there is provided a nickel

powder production device in which a nickel sulfate-ammine

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-ammine 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, as a washing

solution, water, drain generated after heat is recovered from

steam generated when pressure is depressurized to normal

pressure in the depressurization tank, or a filtrate obtained

by subjecting the recovered nickel powder slurry to solid

liquid separation to the discharge piping at a pressure of 2.0

MPa to 2.5 MPa.

6B

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

ammine 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-ammine 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-ammine 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-ammine complex solution, and hydrogen reduction reaction is caused by supplying a mixed slurry of the nickel sulfate-ammine 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-ammine 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-ammine complex solution and

nickel powder as seed crystals is charged.

The nickel sulfate-ammine complex solution is a solution containing nickel in the form of an ammine complex, and can be obtained, for example, by adding ammonia gas or ammonia water

(NH 4 0H) to a nickel sulfate (NiSO 4 ) solution.

When the nickel sulfate-ammine 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 ammine complex.

As the nickel powder to be added as seed crystals, nickel

powder with an average particle size of 0.1 pm to 300 pm is

preferably used, and nickel powder with an average particle

size of 10 pm to 200 pm is more preferably used. When the

particle size of the nickel powder as seed crystals is less

than 0.1 pm, 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 pm, 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-ammine 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 1500C to 2500C. Further, the temperature is set

preferably to 1500C to 1850C. 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 1500C, reduction efficiency

of nickel ions in the nickel sulfate-ammine complex solution

is degraded. On the other hand, even when the reaction

temperature is higher than 2500C, 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 1500C to

2500C, 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-ammine 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-ammine 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-ammine 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

ammine 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-ammine complex solution is reacted with hydrogen gas.

In this reaction tank 11, the reaction in which nickel ions in

the nickel sulfate-ammine 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-ammine 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-ammine 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-ammine complex solution by the

charging piping. In the reaction tank 11, the nickel sulfate

ammine 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-ammine 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 ammine 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-ammine 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 pm 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 1850C, 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.

Throughout this specification and the claims which follow,

unless the context requires otherwise, the word "comprise",

and variations such as "comprises" or "comprising", will be

understood to imply the inclusion of a stated integer or step

or group of integers or steps but not the exclusion of any

other integer or step or group of integers or steps.

The reference in this specification to any prior

publication (or information derived from it), or to any matter

which is known, is not, and should not be taken as, an

acknowledgement or admission or any form of suggestion that

that prior publication (or information derived from it) or

known matter forms part of the common general knowledge in the

field of endeavour to which this specification relates.

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 (5)

The claims defining the invention are as follows:

1. A nickel powder production method, the method comprising

reacting a nickel sulfate-ammine 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 to a

depressurization tank that depressurizes the nickel powder

slurry to normal pressure, and then water, drain generated

after heat is recovered from steam generated when pressure is

depressurized to normal pressure in the depressurization tank,

or a filtrate obtained by subjecting the recovered nickel

powder slurry to solid-liquid separation is supplied as a

washing solution to the discharge piping at a predetermined

pressure of 2.0 MPa to 2.5 MPa 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

or 2, 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-ammine 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-ammine 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, as a washing solution, water, drain generated

after heat is recovered from steam generated when pressure is

depressurized to normal pressure in the depressurization tank,

or a filtrate obtained by subjecting the recovered nickel

powder slurry to solid-liquid separation to the discharge

piping at a pressure of 2.0 MPa to 2.

5 MPa.