AU2019444538A1 - Method for treating nickel-including raw material - Google Patents

Abstract

A method for treating a nickel-including raw material, said method being characterized by having an oxidizing roasting step in which a nickel-including raw material that includes a magnesium component is oxidizing roasted to make the magnesium component into magnesium oxide.

Description

DESCRIPTION METHOD FOR TREATING NICKEL-INCLUDING RAW MATERIAL

Technical Field

[0001] The present invention relates to a method for treating a nickel-including raw

material.

Background Art

[0002] A nickel sulfate compound, which is a raw material of various nickel

compounds or metallic nickel, has been used for electrolytic nickel plating, electroless

nickel plating, a catalyst material, or the like. Recently, a demand for a secondary

battery in which a nickel compound or metallic nickel is used as a positive electrode

material, as a power source of transportation equipment, for example, an electric vehicle

or the like, electronic equipment, or the like, is expected to increase in the future. Stable

feeding of a high-purity nickel sulfate compound has been desired to obtain a high

performance secondary battery.

[0003] Examples of impurities that may be contained in a low-purity nickel compound

can include other metal compounds such as iron, copper, cobalt, manganese, and

magnesium. A method for dissolving, in a sulfuric acid solution, metallic nickel having

a high purity of nickel by an electrowinning method, or a solvent extraction method has

been used as a method for obtaining a high-purity nickel compound. In the solvent

extraction method, a step of selectively extracting and removing other metal compounds

or selectively extracting and removing a nickel compound is performed. In either case, in order to selectively extract specific metal ions, a special chemical is required, resulting in a high cost.

[0004] As a method for producing nickel sulfate, a method for exchanging anions of a

nickel compound for sulfate radicals by an ion exchange method or a method for

dissolving nickel metal powder in a sulfuric acid solution while generating hydrogen gas,

has been also known. In addition, Patent Literature 1 discloses a method for obtaining

water-soluble nickel sulfate by heat-treating nickel oxide powder having a specific gravity

of more than 6.30 in sulfuric acid and then leaching the heated nickel oxide powder with

hot water. In Patent Literature 1, a sulfuric acid solution having a concentration of 30%

to 60% (Claims 1 to 5), and concentrated sulfuric acid having a concentration of 95%

(Claims 6 and 7) are used as the sulfuric acid used in the heat treatment. In Patent

Literature 1, when the concentrated sulfuric acid having a concentration of 95% is used

(Examples 7 to 9), a high temperature of 275°C or higher is required.

Citation List

Patent Literature

[0005] Patent Literature 1: US 3,002,814

Summary of Invention

Technical Problem

[0006] An object of the present invention is to provide a method for treating a nickel

including raw material capable of efficiently treating a nickel-including raw material

containing a high concentration of a magnesium component.

Solution to Problem

[0007] A first aspect of the present invention is a method for treating a nickel-including

raw material, the method including an oxidizing roasting step of oxidizing roasting a

nickel-including raw material containing a magnesium component to obtain magnesium

oxide from the magnesium component.

[0008] A second aspect of the present invention is the method for treating a nickel

including raw material according to the first aspect, in which the nickel-including raw

material contains nickel ore, and the method further includes, after the oxidizing roasting

step, a magnesium removing step of removing the magnesium component from the

nickel-including raw material.

[0009] A third aspect of the present invention is the method for treating a nickel

including raw material according to the first or second aspect, in which the method further

includes, before the oxidizing roasting step, a step of crushing the nickel-including raw

material containing the magnesium component.

[0010] A fourth aspect of the present invention is the method for treating a nickel

including raw material according to the second aspect, in which in the magnesium

removing step, at least a part of a silica component contained in the nickel ore is removed.

[0011] A fifth aspect of the present invention is the method for treating a nickel

including raw material according to the second or fourth aspect, in which the method

further includes, after the magnesium removing step, a sulfating roasting step of sulfating

roasting the nickel-including raw material from which the magnesium component is

removed to obtain a roasted product containing nickel sulfate.

[0012] A sixth aspect of the present invention is the method for treating a nickel

including raw material according to the fifth aspect, in which the nickel-including raw material contains an iron component, and in the sulfating roasting step, heating and roasting are performed under conditions of an oxygen partial pressure and a sulfur dioxide partial pressure at which nickel sulfate is more thermodynamically stable than nickel oxide in a Ni-S-O system and iron oxide is more thermodynamically stable than iron sulfate in an Fe-S-O system.

Advantageous Effects of Invention

[0013] According to the first aspect, the oxidized roasted nickel-including raw material

can be easily treated in a subsequent step by using a difference in properties between

nickel oxide converted from a nickel component and magnesium oxide converted from a

magnesium component. Therefore, even a nickel-including raw material containing a

high concentration of a magnesium component can be efficiently treated.

[0014] According to the second aspect, the nickel-including raw material can be easily

treated in the subsequent step by removing the magnesium component contained in the

nickel-including raw material.

[0015] According to the third aspect, the oxidizing roasting of the magnesium

component contained in the nickel-including raw material can be accelerated by adjusting

a particle size of the nickel-including raw material.

[0016] According to the fourth aspect, the nickel-including raw material can be easily

treated in the subsequent step by removing an excessive silica component and the like

contained in the nickel-including raw material.

[0017] According to the fifth aspect, since the nickel-including raw material is treated

by a dry refining method, it is not necessary to use liquid sulfuric acid, and the treatment

is easily performed.

[0018] According to the sixth aspect, the nickel component is converted into a nickel

sulfate compound, and conversion from the iron component into iron sulfate is suppressed.

Thus, consumption of sulfur by the iron can be suppressed, and production efficiency of

the nickel sulfate compound can be improved.

Brief Description of Drawings

[0019] FIG. 1 is a configuration view schematically illustrating a method for treating

a nickel-including raw material according to an embodiment.

FIG. 2 is a view illustrating a conceptual state of each of a Ni-S-O system and

an Fe-S-O system.

Description of Embodiments

[0020] A treatment method of the present embodiment includes an oxidizing roasting

step of oxidizing roasting a nickel-including raw material containing a magnesium

component to obtain magnesium oxide from the magnesium component.

[0021] The nickel-including raw material may be a nickel compound or metallic nickel

as long as it contains a nickel element. A nickel compound is not particularly limited,

and examples thereof can include nickel salts such as nickel oxide, nickel hydroxide,

nickel sulfide, and nickel chloride. The nickel compound may be a hydrate. The

metallic nickel may be a nickel alloy such as ferronickel. When metallic nickel (a

simple substance or an alloy) is used as the nickel-including raw material, metallic nickel

may be a shot formed of small pieces of a molten metal. Nickel ore can be used as the

nickel-including raw material. Examples of the nickel ore can include one or more of

nickel oxide ore and nickel sulfide ore. Nickel matte containing nickel sulfide as a main component or the like can be used as the nickel-including raw material.

[0022] Examples of the nickel oxide ore can include laterite ores containing a nickel

component, such as limonite and saprolite. The limonite may be limonite containing a

small amount of an iron component or limonite containing a large amount of an iron

component. The saprolite may be saprolite in which a content of nickel is high (for

example, a content of Ni is 1.8 wt% or higher) or may be saprolite in which a content of

nickel is low (for example, a content of Ni is lower than 1.8 wt%). Examples of the

nickel sulfide ore can include pentlandite, millerite, chalcopyrite containing a nickel

component, and pyrrhotite containing a nickel component.

[0023] The nickel-including raw material may or may not contain an iron component.

In a case where the nickel-including raw material contains an iron component, the iron

component is separated from the nickel sulfate compound in a subsequent step, but it is

desirable that a content of the iron component in the raw material is low, from the

viewpoint of energy consumption. The treatment can be performed even when the

content of the iron component is higher than that of the nickel component, but it is

preferable that the content of the iron component is lower than that of the nickel

component. The nickel-including raw material is not limited to one kind, and two or

more kinds of the nickel-including raw materials may be used. In a case where two or

more kinds of the nickel-including raw materials are used, these raw materials may be fed

in a mixed state or may be fed separately. For example, a nickel-including raw material

containing no sulfur component may be used, and/or a nickel-including raw material

containing a sulfur component as at least a part of the raw material, for example, nickel

sulfide ore, nickel sulfide, and nickel matte may be used.

[0024] In the nickel-including raw material suitable for the present embodiment, at least one kind of a nickel-including raw material contains a magnesium component. For example, nickel sulfide ore such as heazlewoodite or pentlandite may be contained in parent rock such as serpentine containing magnesium. As an example, a proportion of the nickel sulfide ore may be about 0.2 to 5 wt%, and a particle size of the nickel sulfide ore may be about 2 pm to 1 mm. In addition, even when the ore contains a high concentration of a mineral containing a magnesium component, such as dolomite or talc, the magnesium component can be mixed in the nickel-including raw material. A ratio of the magnesium component to the nickel component is not particularly limited, but

Mg/Ni may be, for example, about 5 to 15 or 8 to 12.5, or higher than these ranges. In

a case where the nickel-including raw material contains a magnesium component and an

iron component, a ratio of the magnesium component to the iron component is not

particularly limited, but Mg/Fe may be about 0.6 to 2. The nickel-including raw

material may contain a high concentration of the magnesium component. For example,

when serpentine whose chemical formula is Mg3Si2(OH) 4 0 5 is used, a proportion of Mg

is about 26 wt%. The proportion of the magnesium component in the nickel-including

raw material may be, for example, 10 wt% or higher, 15 wt%, 20 wt%, 25 wt%, 30 wt%,

or a proportion lower or higher than these proportions or in the middle of these

proportions.

[0025] FIG. 1 illustrates a schematic configuration of a system for performing a

sulfating roasting method using the treatment method according to the present

embodiment. The treatment system of the present embodiment includes an oxidizing

roasting furnace 12 for performing an oxidizing roasting step 10, a water adding device

22 and a classification device 24 for performing a magnesium removing step 20, a

sulfating roasting furnace 32 for performing a sulfating roasting step 30, and a cooling unit 41 and a dissolving tank 43 for performing an extraction step 40.

[0026] It is preferable to reduce a particle size of a nickel-including raw material 11 by

operations such as shredding, crushing, and grinding, prior to the oxidizing roasting step

10. Since an oxidizing roasting reaction is initiated from a surface of the nickel

including raw material 11, the smaller the particle size of the nickel-including raw

material 11, the shorter the reaction time, which is preferable. A means for crushing the

nickel-including raw material 11 is not particularly limited, but one or two or more of a

ball mill, a rod mill, a hammer mill, a fluid energy mill, and a vibration mill can be used.

The particle size of the nickel-including raw material 11 after the crushing is not

particularly limited. In a case where the nickel-including raw material is available in a

form of fine particles, such as limonite ore, the nickel-including raw material may be fed

to the oxidizing roasting step 10 as it is.

[0027] Examples of the oxidizing roasting furnace 12 can include a stirring type

roasting furnace, a rotary furnace type roasting furnace, and a fluidized roasting furnace

having a fluidized bed. In the related art, roasting of ore or the like is performed using

a stirring type roasting furnace or a rotary furnace type roasting furnace after coarsely

crushing mined ore. In this case, a burden of pretreating an object to be roasted is

reduced and a rotation speed is slow, but a reaction speed is slow and a device becomes

large. Therefore, a fluidized roasting furnace of a type for roasting an object to be

roasted while allowing the object to be roasted to flow in combustion air in a floating state

has become widespread. The device can be miniaturized by adopting the fluidized

roasting furnace. An optimum method for the oxidizing roasting furnace 12 can be

selected according to characteristics of ore to be treated. For example, in a case where

ore is mainly composed of fine powder of limonite or the like, scattering of the fine powder can be suppressed using a rotary furnace type roasting furnace.

[0028] A roasting temperature (oxidizing roasting temperature) in the oxidizing

roasting step of the present embodiment is preferably, for example, 600°C or higher. An

upper limit of the oxidizing roasting temperature is not particularly limited, but the

oxidizing roasting temperature may be about 600 to 800°C, from the viewpoint of a cost

of a refractory material of the oxidizing roasting furnace 12 or the like. The treatment

can be performed at a relatively low temperature as compared to a case in which slag is

discharged in a refining furnace at, for example, about 1,500 to 1,550°C. As a specific

example, the oxidizing roasting temperature may be 600°C, 650°C, 700°C, 750°C, or

800°C, or a temperature in a range of lower or higher than these temperatures or in the

middle of these temperatures. In a case where the nickel-including raw material 11 such

as raw ore is crushed before the oxidizing roasting step 10, it is preferable that the nickel

including raw material 11 is crushed until the particle size of the nickel-including raw

material 11 is 30 mm or less, for example, about 150 pm. A structure of the oxidizing

roasting furnace 12 is not particularly limited, but an inlet for the nickel-including raw

material 11 and an outlet for an oxidized roasted product 13 may be provided on each side

surface of the furnace body, for example, in an oblique direction. An outlet for an

exhaust gas 14 may be provided at an upper portion of the furnace body.

[0029] A cost can be reduced by feeding the raw ore to the oxidizing roasting step 10

using only a simple pretreatment method such as crushing or the like without treating the

raw ore by flotation. When ore such as serpentine is crushed and then treated by

flotation, the ore becomes fine particles and moves to a floating side, similarly to a

metallic nickel component. Therefore, it is difficult to concentrate the nickel component

by separating the nickel component from a parent rock component. In addition, even in a case where the parent rock component moves to a sedimentation side, a large amount of the nickel component is likely to move together with the parent rock component, resulting in a large loss. Therefore, a recovery rate of the nickel component can be increased by treating the ore by oxidizing roasting without flotation.

[0030] In the oxidizing roasting step 10, as an oxidant, 02 gas, air, or the like may be

fed. In the oxidized roasted product 13 obtained by oxidizing roasting the nickel

including raw material 11 containing the magnesium component, the magnesium

component is converted into magnesium oxide. Further, the nickel component may be

converted into nickel oxide. Iron, the sulfur component, and the like contained in the

nickel-including raw material 11 may be oxidized. Ore such as serpentine can be

decomposed to form magnesium silicate such as MgSiO2, and can also be decomposed

into MgO + SiO 2 by further oxidizing the ore.

[0031] In the magnesium removing step 20, water 21 is added to the oxidized roasted

product 13 by the water adding device 22. Therefore, the magnesium oxide reacts with

water to form magnesium hydroxide. A magnesium component 26 and a residue 25

containing a nickel component are separated from a mixture 23 passing through the water

adding device 22 by the classification device 24. As a method for removing the

magnesium component 26 from the oxidized roasted product 13, a method for separating

the magnesium component by a difference in particle sizes as in the classification device

24 may be used, or a method using a specific gravity difference or solubility, or any other

methods may be adopted. In the water adding device 22, in a case where water is

sprayed when the oxidized roasted product 13 is hot, MgO changes to Mg(OH)2 and

crushed by a volume expansion effect, which is preferable. In this case, even when the

particle size of the nickel-including raw material 11 before the oxidizing roasting is relatively large, the residue 25 having a small particle size can be obtained. In a case where the nickel-including raw material 11 contains a silica (SiO 2 ) component such as nickel ore, at least a part of the silica component may be separated and removed from the residue 25 along with the magnesium component 26.

[0032] In the present specification, at least a part of the magnesium component 26 may

be removed from the oxidized roasted product 13, but in a case where the residue 25 is

used as an object to be sulfated roasted 31, it is preferable to remove as much of the

magnesium component 26 as possible. When the magnesium component 26 is subjected

to the sulfating roasting step 30 in a state in which the magnesium component 26 remains

in the object to be sulfated roasted 31, the sulfur component may be excessively consumed,

and magnesium sulfate may be mixed in a sulfated roasted product 33, which may cause

difficulty in separation between nickel sulfate and magnesium sulfate.

[0033] The residue 25 in the classification device 24, obtained by removing the

magnesium component 26 from the oxidized roasted product 13 is fed to the sulfating

roasting furnace 32 as the object to be sulfated roasted 31. Examples of the sulfating

roasting furnace 32 can include a stirring type roasting furnace, a rotary furnace type

roasting furnace, and a fluidized roasting furnace having a fluidized bed. As described

above, in a case where a fluidized roasting furnace is used, the device can be miniaturized.

The sulfating roasting furnace 32 may be a roasting furnace different from the oxidizing

roasting furnace 12, but the oxidizing roasting step 10 and the sulfating roasting step 30

may be performed in the same roasting furnace. A structure of the sulfating roasting

furnace 32 is not particularly limited, but an inlet for the object to be sulfated roasted 31

and an outlet for the sulfated roasted product 33 may be provided on each side surface of

the furnace body, for example, in an oblique direction. An outlet for an exhaust gas 34 may be provided at an upper portion of the furnace body. When a particle size of the residue 25 is small, a sulfating roasting reaction is initiated from a surface of the object to be sulfated roasted 31, and the reaction time is thus shortened, which is preferable.

[0034] In the sulfating roasting furnace 32, the object to be sulfated roasted 31 is

treated by sulfating roasting to convert the nickel component contained in the nickel

including raw material 11 into nickel sulfate. A sulfur component which is deficient in

the object to be sulfated roasted 31, oxygen for oxidizing the sulfur component, and the

like may be fed to the sulfating roasting furnace 32. For simplification, paths for feeding

various materials to be fed to the sulfating roasting furnace 32 are not distinguished in

FIG. 1. In order to improve conversion efficiency of the sulfating roasting, auxiliary

substances or materials may be fed to the sulfating roasting furnace 32 together with the

object to be sulfated roasted 31.

[0035] For example, a material harder than the nickel component contained in the

object to be sulfated roasted 31 may be fed to the sulfating roasting furnace 32 as a

medium. Therefore, reactivity can be improved due to grinding of the nickel component.

In a case where a silica component is contained in the object to be sulfated roasted 31, the

silica component may also function as a medium. It is preferable that a material of the

medium is softer than an inner wall material of the sulfating roasting furnace 32.

Therefore, deterioration, damage, and the like of the inner wall material can be reduced.

Specific examples of the medium can include aluminum oxide such as synthetic alumina,

zirconia, silica, silicon nitride, silicon carbide, tungsten carbide, and glass. A particle

shape of the medium is not particularly limited, and examples thereof can include a

spherical shape, a columnar shape, and a polyhedral shape. An average particle size of

the media may be, for example, 0.02 to 10 mm. In a case where the sulfated roasted product 33 is water-soluble, the medium can be separated according to solubility in water.

Thus, the medium is preferably insoluble or sparingly soluble in water.

[0036] The sulfated roasted product 33 containing a nickel sulfate compound is

obtained through the sulfating roasting step 30. In the extraction step 40, a nickel sulfate

solution 44 is obtained by a water dissolution step of dissolving the nickel sulfate

compound in water by feeding water to the sulfated roasted product 33 in the dissolving

tank 43. Details will be described below, but it is preferable to cool the sulfated roasted

product 33 in the cooling unit 41 before adding water to the sulfated roasted product 33.

In addition, the sulfated roasted product 33 may be crushed before adding water to the

sulfated roasted product 33. Since the iron component contained in the sulfated roasted

product 33 becomes a form which is sparingly soluble in water, such as iron oxide or iron

sulfide, a solid-phase residue 45 precipitates in the dissolving tank 43. Then, the nickel

sulfate solution 44 is obtained as a liquid phase from the dissolving tank 43, and the

residue 45 containing iron oxide is separated as a solid phase. Further, if necessary, for

example, a step of purifying the nickel sulfate solution 44 is performed to separate nickel

sulfate, cobalt sulfate, and the like, thereby obtaining a nickel sulfate compound from

which impurities such as cobalt are removed. A method for separating the iron

component contained in the sulfated roasted product 33 is not limited to a method using

a difference in solubilities, and a method using a difference in magnetisms, specific

gravities, particle sizes, and the like, or a method using differences in two or more of

magnetisms, specific gravities, particle sizes, and the like may be adopted.

[0037] It is preferable that the nickel-including raw material is sulfated roasted under

conditions of an oxygen partial pressure and a sulfur dioxide partial pressure at which

nickel sulfate is more thermodynamically stable than nickel oxide in a Ni-S-O system and iron oxide is more thermodynamically stable than iron sulfate in an Fe-S-0 system.

Therefore, even in a case where the nickel-including raw material contains an iron

component, the nickel component is converted into nickel sulfate and conversion from

the iron component into iron sulfate is suppressed. Thus, it is possible to suppress

consumption of the sulfur component by the iron component and to improve production

efficiency of nickel sulfate.

[0038] FIG. 2 is a view illustrating an example of a conceptual phase diagram of each

of a Ni-S-0 system and an Fe-S-0 system. Boundary lines between phases in the Ni-S

o system are indicated by broken lines (---), and boundary lines between phases in the

Fe-S-0 system are indicated by alternate long and short dash lines(---). Chemical

formulas along with the arrows show thermodynamically stable phases on the sides from

the boundary lines toward the arrows. In the phase diagram illustrated in FIG. 2, a

horizontal axis represents a logarithm of the 02 partial pressure. The 02 partial pressure

is higher on the more right side of the horizontal axis, and the 02 partial pressure is lower

on the more left side of the horizontal axis. In the phase diagram illustrated in FIG. 2, a

vertical axis represents a logarithm of the S02 partial pressure. The S02 partial pressure

is higher on the upper side of the vertical axis, and the S02 partial pressure is lower on

the lower side of the vertical axis. A unit of the partial pressure is, for example,

atmospheric pressure (atm= 101,325 Pa).

[0039] An example of the nickel sulfate contained in the Ni-S-0 system can include

NiSO4 , and an example of the nickel oxide contained in the Ni-S-0 system can include

NiO. In the phase diagram illustrated in FIG. 2, a boundary line LNi indicates a boundary

line between a region in which nickel sulfate is thermodynamically stable and a region in

which nickel oxide is thermodynamically stable. In a region in which the S02 partial pressure and the 02 partial pressure are higher than the boundary line LNi, the nickel sulfate becomes a thermodynamically stable phase. In addition, in a region in which the

S02 partial pressure and the 02 partial pressure are lower than the boundary line LNi, the

nickel oxide becomes a thermodynamically stable phase.

[0040] Examples of the iron sulfate contained in the Fe-S-0 system can include FeS0 4

and Fe2(SO 4 )3, and an example of the iron oxide contained in the Fe-S-0 system can

include Fe203. In the phase diagram illustrated in FIG. 2, a boundary line LFe indicates

a boundary line between a region in which iron sulfate is thermodynamically stable and

a region in which iron oxide is thermodynamically stable. In a region in which the S02

partial pressure and the 02 partial pressure are higher than the boundary line LFe, the iron

sulfate becomes a thermodynamically stable phase. In addition, in a region in which the

S02 partial pressure and the 02 partial pressure are lower than the boundary line LFe, the

iron oxide becomes a thermodynamically stable phase.

[0041] According to the phase diagram illustrated in FIG. 2, in a region A in which the

S02 partial pressure and the 02 partial pressure are lower than the boundary line LFe and

the S02 partial pressure and the 02 partial pressure are higher than the boundary line LNi,

the nickel sulfate in the Ni-S-0 system becomes a thermodynamically stable phase, and

the iron oxide in the Fe-S-0 system becomes a thermodynamically stable phase. Then,

a system containing nickel (Ni), oxygen (0), and sulfur (S) is roasted under a condition

of the overlapping region A, such that the nickel component can be converted into nickel

sulfate while suppressing production of iron sulfate, even when the iron component

coexists in the system.

[0042] A roasting temperature (sulfating roasting temperature) in the sulfating roasting

step of the present embodiment is preferably 400 to 750°C and more preferably 550 to

750°C. Asa specific example, the sulfating roasting temperature maybe 400°C, 450°C,

500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or a temperature in a range of lower or

higher than these temperatures or in the middle of these temperatures. At such a roasting

temperature, the reduction of the iron component is suppressed, and thus, the iron

component can coexist with a nickel sulfate compound in a form of iron oxide, iron

sulfide, or the like. Therefore, aggregation of particles in a roasted product can be

suppressed, and a treatment in a subsequent step can be easily performed. In addition,

at the above temperature, a carbonate is decomposed. Therefore, even in a case where

the carbonate is mixed, it is possible to prevent the carbonate from being dissolved in

water and thus remaining as an impurity, and it is possible to easily perform a treatment

in a subsequent step.

The sulfating roasting temperature is still more preferably 600 to 700°C. At

the above temperature, even in a case where the object to be roasted contains manganese

(Mn) as an impurity derived from the nickel-including raw material, the manganese forms

a spinel structure with iron, and thus, the manganese can be easily removed as an insoluble

matter.

[0043] As for the 02 partial pressure in the sulfating roasting step, a common logarithm

log p(O2) of the 02 partial pressure in terms of the atmospheric pressure (atm) unit is

preferably in a range of -4 to -6, and log p(O2) is more preferably in a range of -4 to -5 or

-5 to -6 depending on a condition and the like. When the 02 partial pressure is reduced,

the S02 partial pressure tends to increase even in the overlapping region A of FIG. 2.

Therefore, production of nickel sulfate can be accelerated while suppressing production

of iron sulfate. The optimum region deviates slightly depending on the sulfating

roasting temperature, and as the temperature becomes higher, the optimum region moves to a side where log p(O2) in the overlapping region A becomes large (a side where log p(O2) is closer to zero (0)). Log p(O2) may be selected from, for example, a range of -8 to 0 depending on a relationship between log p(S02) and the sulfating roasting temperature.

[0044] As for the S02 partial pressure in the sulfating roasting step, a common

logarithm log p(S02) of the S02 partial pressure in terms of the atmospheric pressure

(atm) unit is preferably in a range of -1 to +1, and log p(S02) is more preferably in a range

of -I to 0. Even in the overlapping region A of FIG. 2, production of a sulfate can be

accelerated by further increasing the S02 partial pressure. Further, when the S02 partial

pressure is set to about a normal pressure or a pressure equal to or lower than the normal

pressure (a common logarithm of the partial pressure is about 0 or less), the total pressure

of a roasting atmosphere in the sulfating roasting step does not become excessive, and

thus, the facility can be easily handled. Log p(S02) may be selected from, for example,

a range of -4 to +1 depending on a relationship with logp(O2) and the sulfating roasting

temperature.

[0045] In order to maintain the condition in which the 02 partial pressure is low in the

roasting furnace, an inert gas such as nitrogen (N2 ) or argon (Ar) may be fed to the

roasting furnace. The inert gas can be used as a carrier when feeding a volatile

component such as gas or steam to the roasting furnace. The S02 partial pressure can

be adjusted by, for example, controlling a feed amount of a sulfur source. In a case

where the amount of the sulfur component contained in the nickel-including raw material

is small, a sulfur component may be fed in the sulfating roasting step. Examples of a

feedstock of a sulfur component (sulfur source) can include solid sulfur which is solid at

a normal temperature (elementary sulfur (S)), a sulfur oxide (SO 2 or the like), sulfuric acid (H 2 SO 4 ), a sulfate, a sulfide, and sulfide ore such as iron pyrite (FeS2). In a case where the sulfur source is sulfur (S), it is preferable to generate S02 gas in an oxygen enriched state. Sulfur may be combusted in an atmosphere containing oxygen to produce a sulfur oxide.

[0046] A preferred range of the partial pressure can be determined from the positions

of the boundary line LNi and the boundary line LFe by examining the above-described

phase diagram according to the sulfating roasting temperature. For example, when the

sulfating roasting temperature is 650 to 750°C, as the preferred range of the partial

pressure, log p(O2) may be about -8 to -4 and log p(S02) may be about -2 to +2, log p(O2)

may be about -3 to -2 and log p(S02) may be about -3 to +1, or log p(O2) may be about

1 to 0 and log p(S02) may be about -4 to 0.

[0047] Next, purification of nickel sulfate obtained by the sulfating roasting and the

like will be described in more detail. In the water dissolution step, water added to the

sulfated roasted products 33 and 42 in the dissolving tank 43 is preferably pure water that

is treated so as not to contain impurities. A water treatment method is not particularly

limited, and examples thereof can include one or more of filtration, membrane separation,

ion exchange, distillation, disinfection, chemical treatment, and adsorption. As water

for dissolution, tap water, industrial water, or the like obtained from a water source may

be used, or water obtained by treating drainage water generated in other processes may

be used. Two or more types of water may also be used. The dissolution can be

performed with an acidic solution of sulfuric acid having a pH of about 4 as well as with

pure water. For example, in a region to be an oxidation region in measurement of an

oxidation-reduction potential at the pH of the solution of about 4 to 5, for example, 3.8 to

5.5, it is advantageous to selectively extract the nickel sulfate compound into an aqueous phase while suppressing dissolution of other impurities such as a sulfate, which is preferable.

[0048] Solubility of nickel sulfate in water is highest at 150°C, at which 55 g of NiSO 4

is dissolved in 100 g of the solution, but 22 gofNiSO 4 is dissolved in 100 g of the solution

even at 0°C. Therefore, it is desirable to perform the dissolution operation at a

temperature equal to or lower than a boiling point of water. In addition, it is preferable

that the nickel sulfate solution 44 obtained in the water dissolution step has a

concentration at which NiSO4 does not precipitate even at a normal temperature, and it is

preferable that the nickel sulfate solution 44 is maintained in a heated state at a

concentration of NiSO 4 higher than the concentration. In order to adjust a temperature

of the nickel sulfate solution 44, it is preferable to adjust a temperature of each of the

sulfated roasted products 33 and 42 or a temperature of water before performing the

dissolution operation. Residual heat of the sulfated roasted products 33 and 42 may be

used as at least a part of a heat source for maintaining the nickel sulfate solution 44 in the

heated state. Therefore, it is preferable that the temperature of each of the sulfated

roasted products 33 and 42 before being dissolved in water is set to an appropriate

temperature.

[0049] As described above, in the system illustrated in FIG. 1, the cooling unit 41 is

provided between the sulfating roasting furnace 32 and the dissolving tank 43. The

cooling unit 41 may be a batch type or a continuous type. In the case of the batch type,

the sulfated roasted products 33 and 42 may be left until the temperature is lowered to a

desired temperature without adding water. In the case of the continuous type, for

example, the cooling unit 41 may be provided in a pipe connecting the sulfating roasting

furnace 32 and the dissolving tank 43 to each other. In the cooling unit 41, for example, a heat exchanger may be provided to recover excess residual heat from the sulfated roasted products 33 and 42, and the recovered residual heat may be used as various heat sources.

[0050] Particles of the sulfated roasted products 33 and 42 may be solidified or a film

which is sparingly soluble in water may be formed on a surface of the particle, due to the

state of each of the sulfated roasted products 33 and 42 obtained from the sulfating

roasting furnace 32 or a change in state of each of the sulfated roasted products 33 and 42

during cooling in the cooling unit 41. Therefore, a step of crushing the sulfated roasted

products 33 and 42 may be added before adding water to the sulfated roasted products 33

and42. A means for crushing the sulfated roasted products 33 and 42 is not particularly

limited, but one or two or more of a ball mill, a rod mill, a hammer mill, a fluid energy

mill, and a vibration mill can be used. The crushing of the sulfated roasted products 33

and 42 may be started before or after cooling the sulfated roasted products 33 and 42.

[0051] A solid-liquid separation method after the water dissolution step is not

particularly limited, and examples thereof can include a filtration method, a centrifugal

separation method, and a precipitation separation method. In a case where a solid-liquid

separation tank is installed separately from the dissolving tank 43, it is preferable to use

a solid-liquid separation tank having a high performance for separation of solid-phase

fine particles to be the residue 45. Examples of the solid-liquid separation tank can

include one or two or more of afiltration tank, a centrifugal separation tank, a

sedimentation tank, and a precipitation tank. For example, in filtration, a filtration

method is not particularly limited, and examples thereof can include gravity filtration,

reduced pressure filtration, pressurized filtration, centrifugal filtration, filtration with

addition of a filter aid, and compression squeeze filtration. Pressurized filtration is preferred in terms of easy adjustment of a differential pressure and quick separation.

[0052] Examples of the impurities that can coexist with the nickel sulfate compound

can include iron (Fe), cobalt (Co), and aluminum (Al). In a case where these metal salts

become sulfates in the roasting step, when the nickel sulfate compound is dissolved in

water, iron sulfate, cobalt sulfate, and the like are also dissolved. Further, in water, for

example, iron precipitates as oxides such as FeOOH, Fe203, and Fe304, and thus, the

impurities are easily removed from the nickel sulfate compound. In the sulfating

roasting step of the present embodiment, conditions are set so that the iron component

does not easily become iron sulfate. Therefore, the nickel sulfate compound is subjected

to water dissolution and solid-liquid separation to obtain the nickel sulfate solution 44

having a small amount of an iron component. The residue 45 containing iron oxide and

the like after separating the nickel sulfate solution 44 can be reused as an iron component

for cement. In addition, the iron oxide separated from the residue 45 can also be used

in production of pig iron or the like as a raw material for iron production using a melt

reduction furnace, an electric furnace, or the like, or used for a pigment, ferrite, a magnetic

material, a sintered material, or the like. In particular, in a case where an area where a

nickel-including raw material is produced is a remote area away from industrial areas,

cities, and the like, it is advantageous to commercialize an iron component locally,

similarly to the nickel component, from the viewpoint of transportation costs and the like.

For example, when pig iron is produced using an electric furnace installed in a refining

step of ferronickel and a volume reduction is performed, it is easy to carry out the pig iron

as an unprocessed iron metal.

[0053] Among the impurities, a metal having a lower ionization tendency than

hydrogen (H), such as copper (Cu), gold (Au), silver (Ag), or a platinum group metal

(PGM), remains as a solid in the water dissolution step, and can thus be removed in a

solid-liquid separation step. In addition to the impurities, a compound such as, Pb, or

Zn can be included in the solid removed in the solid-liquid separation step. The solid

including these impurities can be recycled as valuable resources.

[0054] The nickel sulfate solution 44 obtained through the water dissolution and solid

liquid separation contains the nickel sulfate compound as a main component. Therefore,

the nickel sulfate solution 44 can be transported and used as a solution of the nickel sulfate

compound as it is, or as a solid of the nickel sulfate compound by drying or the like. In

a case where it is desirable to reduce the impurities in the nickel sulfate solution 44, for

example, cobalt sulfate and the like, depending on use, techniques such as solvent

extraction, electrodialysis, electrowinning, electro refining, ion exchange, and

crystallization can be used.

[0055] In the case of the solvent extraction, it is preferable to use an extractant capable

of preferentially or selectively extracting cobalt rather than nickel into a solvent.

Therefore, purification can be efficiently performed by leaving the nickel sulfate

compound in an aqueous solution. Examples of the extractant can include organic

compounds having a functional group that can bind to a metal ion, such as a phosphinic

acid group and a thiophosphinic acid group. In the solvent extraction, as a diluent, an

organic solvent capable of separating the extractant from water may be used. By

dissolving the extractant bonded to a metal ion such as cobalt in the diluent, the cobalt is

easily separated from the aqueous solution containing nickel sulfate compound without

using a large amount of the extractant. The diluent is preferably an organic solvent

which is immiscible with water.

[0056] In the case of the crystallization, the nickel sulfate compound to be targeted may be crystallized from the solution by at least one factor such as a change in temperature, a reduction in solvent, or addition of other substances. In this case, purification may be performed by leaving at least a part of the impurities in a liquid phase.

Specific examples thereof can include an evaporation crystallization method and a poor

solvent crystallization method. In the evaporation crystallization method, a solution is

concentrated by boiling or evaporation under reduced pressure to crystallize the nickel

sulfate compound. The poor solvent crystallization method is a crystallization method

used in pharmaceutical production or the like, and in the poor solvent crystallization

method, for example, an organic solvent is added to a solution containing a nickel sulfate

compound to precipitate the nickel sulfate compound. The organic solvent used in the

crystallization is preferably an organic solution which is miscible with water, and

examples of the organic solvent can include one or more selected from the group

consisting of methanol, ethanol, propanol, isopropanol, butyl alcohol, ethylene glycol,

and acetone. Two or more of the organic solvents may be used. As for a concentration

range in which the organic solvent is mixed with water, it is preferable that the organic

solvent is mixed with water at a concentration at which the organic solvent is added to

the extent that the nickel sulfate compound precipitates, and it is more preferable that the

organic solvent is freely mixed with water in any ratio. The organic solvent added in

the crystallization step is not limited to an anhydrous organic solvent, and may be a water

containing organic solvent to the extent that it does not interfere with the crystallization.

A ratio of water to the organic solvent is not particularly limited, but may be set to, for

example, 1:20 to 20:1, and is preferably about 1:1, for example, 1:2 to 2:1.

[0057] In a case where the solid nickel sulfate compound is obtained through the

crystallization or the like, the nickel sulfate compound may be in a state of anhydride, monohydrate, dihydrate, pentahydrate, hexahydrate, or heptahydrate of nickel sulfate.

The nickel sulfate compound precipitated by the crystallization can be separated from the

solution by solid-liquid separation. A solid-liquid separation method is not particularly

limited, and examples thereof can include a filtration method, a centrifugal separation

method, and a sedimentation separation method. The metal dissolved in the solution is

preferably neutralized and removed from the solution by a method such as precipitation.

In a case where the purified solution mainly contains a mixture of water and the organic

solvent, it is possible to separate the water and the organic solvent from each other by a

method such as distillation.

[0058] According to the sulfating roasting method of the present embodiment, the

following effects can be obtained.

(1) A yield of the nickel sulfate compound can be improved by removing the

magnesium component contained in the nickel-including raw material.

(2) The conversion reaction from the nickel-including raw material into nickel

sulfate can be accelerated to improve reactivity.

(3) A high-purity nickel sulfate compound can be produced from the nickel

including raw material by the sulfating roasting.

(4) Production of iron sulfate can be suppressed in the sulfating roasting step.

In addition, generation of hydrogen (H 2 ) gas can also be suppressed.

(5) Since the sulfated roasted product is a chemical species in which an iron

component is difficult to dissolve in water and contains a nickel component which is

easily dissolved in water as a nickel sulfate compound, the iron component is easily

removed.

(6) The facility cost can be reduced as compared to a method according to the related art.

(7) Since the conversion reaction of the nickel-including raw material can be

accelerated, for example, in a case where iron is fed in a form of iron oxide, the conversion

reaction proceeds without formation of iron sulfate by iron oxide or formation of a ferrite

alloy of iron and nickel. Therefore, it is possible to obtain a sulfated roasted product

containing high-purity nickel sulfate.

[0059] Hereinabove, the present invention has been described based on preferred

embodiments, but the present invention is not limited to the above-described

embodiments, and various modifications can be made without departing from the gist of

the present invention.

[0060] The object to be roasted is not limited to a nickel-including raw material, and a

material containing metals (Cu, Zn, Co, Fe, and the like) other than nickel can also be

considered. The roasting of the nickel-including raw material according to the above

described embodiments can be applied to roasting for obtaining a metal compound from

the raw material containing another metal.

[0061] In the method for treating a nickel-including raw material described above, the

oxidized roasted product can be used even in a step different from sulfating roasting.

Examples

[0062] Hereinafter, the present invention will be specifically described with reference

to Examples.

[0063] <Example 1>

Raw ore in which a content of a magnesium component was high was crushed

using a ceramic desktop ball mill so that an average particle size thereof was 150 im.

As for main components of a mineral composition (weight ratio) of the used raw ore, serpentine containing a Mg component and a silica component accounted for 82.89%, magnetite containing an Fe component accounted for 9.06%, brucite containing a Mg component accounted for 4 .6 5 %, heazlewoodite containing a Ni component accounted for 2.92%, pentlandite containing a Ni component accounted for 0.19%, coalingite containing a Mg component accounted for 0.08%, chlorite containing a Mg component and the like accounted for 0.07%, and olivine containing a Mg component or an Fe component accounted for 0.04%. Here, a total proportion of the minerals as the main components is 9 9 .8 8 %. A proportion of serpentine is a sum of 82.25% of Mg-serpentine and 0. 6 4 % of Fe-serpentine.

[0064] A pyrolysis curve of serpentine was obtained from a crushed product of the raw

ore using a thermogravimetric/differential thermal (TG/DTA) analyzer. As a result,

although there were variations in samples, it was determined that the serpentine was

pyrolyzed at 600°C to 650°C. In addition, as a result of X-ray analysis, a peak

representing the chemical formula Mg3Si2(OH) 4 0 5 of the serpentine was present in the

raw ore, but the peak disappeared after the oxidizing roasting, and peaks detected with X

rays appeared at a portion representing the chemical formulas Mg2SiO4 and MgSiO3. It

was determined from the result that the oxidizing roasting temperature is desirably 650°C

or higher.

[0065] <Example 2>

A spiral tube electric furnace (furnace core tube: SUS316L, outer appearance

mm x length 400 mm, maximum temperature: 1,500°C) manufactured by SILICONIT

was installed so that the spiral tube was vertically installed and a gas dispersion plate was

installed at the bottom of the furnace. The same raw ore as that of Example 1

(containing Mg component and Ni component) was crushed into an average particle size of 2 mm and 1,000 g of the crushed raw ore was fed to the roasting test device, flowing air was fed from a lower portion to maintain the raw ore in a flow state, and a gas adsorption tube and a vacuum pump were installed on an exhaust gas side of the roasting test device. Oxygen was fed from the gas dispersion plate so that the raw ore was allowed to flow. The oxidizing roasting temperature of the raw ore was 650°C. As a result of performing oxidizing roasting for 0.5 hours and then spraying water when the oxidized roasted product was at a high temperature, a reaction represented by the formula

MgO + H 2 0 -- Mg(OH)2 occurred, and the oxidized roasted product was crushed until a

particle size thereof was 150 pm to 0.8 mm. A peak representing Mg(OH)2 was

confirmed with X-ray analysis in the oxidized roasted product. When the nickel

component in the crushed product obtained by the water spraying was concentrated by a

vibrating sieve and a specific gravity difference separation, most of Mg(OH)2 and SiO 2

were separated.

[0066] <Example 3>

It was experimentally confirmed how many grams of various compounds were

dissolved and saturated in 100 ml of pure water at 25°C. As a result, each of 0.0086 g

of magnesium oxide (MgO), 0.0012 g of magnesium hydroxide (Mg(OH)2), 25.5 g of

magnesium sulfate (MgSO4), 39.3 g of manganese sulfate (MnSO4), and 65 g of nickel

sulfate (NiSO4 ) was dissolved and saturated. As a result, it was presumed that it was

easy to separate and remove magnesium oxide and magnesium hydroxide from nickel

sulfate by solubility, but it was not easy to separate the magnesium sulfate and manganese

sulfate from nickel sulfate by solubility.

[0067] <Example 4>

With respect to a nickel residue from which a Mg component and a silica component were removed in Example 2, equimolar sulfur (S) was added assuming that the nickel component was nickel sulfide ore (Ni3 S2). Sulfating roasting was performed in an electric furnace at 650°C for 30 minutes using the same roasting test device used for oxidizing roasting of Example 2. The sulfated roasted product was dissolved in pure water to obtain a nickel sulfate solution. As a result of comparing the total amount of

Ni in the raw ore before oxidizing roasting with the total amount of Ni recovered as the

nickel sulfate solution after sulfating roasting and water dissolution, 98% of the Ni

component was recovered.

Industrial Applicability

[0068] The present invention can be used for producing a high-purity nickel sulfate

compound which is useful as a raw material of various nickel compounds or metallic

nickel, used for an electrical part such as a secondary battery, a chemical product, or the

like.

Reference Signs List

[0069] 10 Oxidizing roasting step

11 Nickel-including raw material

12 Oxidizing roasting furnace

13 Oxidized roasted product

14 Exhaust gas

20 Magnesium removing step

21 Water

22 Water adding device

23 Mixture

24 Classification device

Residue in classification device

26 Magnesium component

Sulfating roasting step

31 Object to be sulfated roasted

32 Sulfating roasting furnace

33 Sulfated roasted product

34 Exhaust gas from sulfating roasting furnace

Extraction step

41 Cooling unit

42 Cooled sulfated roasted product

43 Dissolving tank

44 Nickel sulfate solution

Residue in dissolution device

Claims (6)

1. A method for treating a nickel-including raw material, the method

comprising:

an oxidizing roasting step of oxidizing roasting a nickel-including raw material

containing a magnesium component to obtain magnesium oxide from the magnesium

component.

2. The method for treating a nickel-including raw material according to claim

1, wherein

the nickel-including raw material contains nickel ore, and

the method further comprises, after the oxidizing roasting step, a magnesium

removing step of removing the magnesium component from the nickel-including raw

material.

3. The method for treating a nickel-including raw material according to claim

1 or 2, wherein

the method further comprises, before the oxidizing roasting step, a step of

crushing the nickel-including raw material containing the magnesium component.

4. The method for treating a nickel-including raw material according to claim

2, wherein

in the magnesium removing step, at least a part of a silica component contained

in the nickel ore is removed.

5. The method for treating a nickel-including raw material according to claim

2 or 4, wherein

the method further comprises, after the magnesium removing step, a sulfating

roasting step of sulfating roasting the nickel-including raw material from which the

magnesium component is removed to obtain a roasted product containing nickel sulfate.

6. The method for treating a nickel-including raw material according to claim

, wherein

the nickel-including raw material contains an iron component, and

in the sulfating roasting step, heating and roasting are performed under

conditions of an oxygen partial pressure and a sulfur dioxide partial pressure at which

nickel sulfate is more thermodynamically stable than nickel oxide in a Ni-S-O system and

iron oxide is more thermodynamically stable than iron sulfate in an Fe-S-O system.